EP2003183B1

Phosphor and light-emitting device

Abstract

This record has no abstract on file.

EP2003183B1, drawing sheet 1 — Sheet 1 of 32

Term

0.5 yearsleft in the term

Expires 9 March 2027.

Parties

Owner: Kabushiki Kaisha Toshiba
Applicants: TOSHIBA KK
Inventors: FUKUDA, Yumi c/o Intellectual Property Division, Minato-ku Tokyo, Japan
TAMATANI, Masaaki c/o Intellectual Property Division, Minato-ku Tokyo, Japan
ASAI, Hironori c/o Intellectual Property Division, Minato-ku Tokyo, Japan
HIRAMATSU, Ryosuke c/o Intellectual Property Division, Minato-ku Tokyo, Japan
and 3 more inventorsShow fewer
TATAMI, Junichi c/o Nat. University Corp. Yokohama Nat. University, Yokohama-shi Kanagawa-ken, Japan
KOMEYA, Katsutoshi c/o Nat. University Corp. Yokohama Nat. University, Yokohama-shi Kanagawa-ken, Japan
WAKIHARA, Toru c/o Nat. University Corp. Yokohama Nat. University, Yokohama-shi Kanagawa-ken, Japan

Examination

Agent: Granleese, Rhian Jane
Filing to grant: 5.5 years

Reach

Cited by: 1 later patent⁠
Cites: 15 earlier patents⁠
Family: 37 members in 4 offices⁠JP18EP9US8WO2

Classification

CPC: C09K11/0883C09K11/77348H10H20/8512
IPC: C09K11 08C09K11 77

3 claims: 1 independent, 2 dependent

1
A luminescent material which is featured in that it exhibits a light emission peak in a wavelength ranging from 490 to 580 nm when excited with light having a wavelength ranging from 250 to 500 nm and that it has a composition represented by the following general formula (2):(M 1-x R x ) a2 AlSi b2 O c2 N d2 (2) (In the general formula (2), M is Sr;R is Eu;and x, a2, b2, c2 and d2 satisfy following relationships: 0 < x ≤ 0.5 , 0.93 < a ⁢ 2 < 1.3 , 4.0 < b ⁢ 2 < 5.8 0.6 < c ⁢ 2 < 1 , 6 < d ⁢ 2 < 11 ) .

281 paragraphs, as filed

Technical Field

0001This invention relates to a luminescent material to be employed in a light-emitting device and to a light-emitting device.

Background Art

0002LED lamps utilizing light-emitting diodes are now employed in various kinds of display devices such as portable devices, PC peripherals, OA equipment, various kinds of switches, light sources for backlights, and display panels. A high-load LED is known to become hot when energized, thus increasing the temperature of the luminescent material to about 100 to 200°C and, due to this rise in temperature, the emission intensity of the luminescent material deteriorates. It is desirable that the luminescent material barely deteriorates even when caused to rise in temperature.

0003As the luminescent material which is capable of green emission as it is excited by blue light and which is designed to be employed in the aforementioned LED lamp, there is known an Eu-activated β-sialon luminescent material. This luminescent material is known to exhibit excellent emission efficiency as it is excited with light having a wavelength of 450 nm. Namely, when this luminescent material is excited with light having a wavelength of 450 nm, it exhibits an absorption coefficient of 65%, an internal quantum efficiency of 53% and an emission efficiency of 35%.

0004It should be noted, with regard to the development of a flat panel display device, that although much vigorous effort has been made in the development of a plasma display panel (PDP) and liquid crystal display (LCD), a field-emission-type display is expected to be more advantageous than the PDP and the LCD in that it is capable of providing a clearer image.

0005This field-emission-type display has a screen in which red, green and blue luminescent materials are arrayed and with a cathode which is disposed to face the screen at smaller intervals than those of the CRT. The cathode is provided with a plurality of electron sources as an emitter element, enabling the electron sources to emit an electron in conformity with a potential difference between the electron sources and the gate electrodes disposed near the electron sources. The electron thus emitted is accelerated by an anode voltage (accelerating voltage) of the luminescent materials side and enabled to impinge against the luminescent materials, thereby enabling the luminescent materials to emit light.

0006As the luminescent materials to be employed in the field-emission-type display constructed as described above, it is required that the luminescent materials are capable of exhibiting a sufficiently high luminous efficiency, so that even when the luminescent materials are saturated with electric charge as excited by a high current density, they are still capable of exhibiting a sufficiently high luminous efficiency. The conventional sulfide luminescent materials (ZnS:Cu, ZnS:Ag) which have been employed as a luminescent material for CRT may be a prospective candidate as meeting the aforementioned requirements. It is however reported that the sulfide luminescent materials such as ZnS are subject to decomposition under the conditions where a low energy cathode-ray display screen is excited. The decomposed matters thus generated may badly degrade a heat filament which is designed to emit electron beam. In particular, ZnS-based blue luminescent materials that have been conventionally employed are more liable to suffer from luminance deterioration as compared with red luminescent materials and green luminescent materials, thereby raising the problem that the display color of a color picture plane changes with time.

Disclosure of Invention

0007An object of the present invention is to provide a luminescent material which is excellent in temperature characteristics.

0008In a first aspect, the present invention provides a luminescent material as recited in claim 1.

Brief Description of Drawings

0009<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is an XRD profile of a luminescent material according to one embodiment;</li><li><figref idref="f0001">FIG. 2</figref> is a cross-sectional view schematically illustrating the structure of a light-emitting device according to one embodiment;</li><li><figref idref="f0002">FIG. 3</figref> are emission spectra obtained as the luminescent materials of Reference Examples 1-4 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0002">FIG. 4</figref> are emission spectra obtained as the luminescent materials of Reference Examples 5-8 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0003">FIG. 5</figref> are XRD profiles of the luminescent materials of Reference Examples 1-4, 7 and 8;</li><li><figref idref="f0003">FIG. 6</figref> are emission spectra obtained as the luminescent materials of Reference Examples 9-11 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0004">FIG. 7</figref> are emission spectra obtained as the luminescent materials of Reference Examples 12-16 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0004">FIG. 8</figref> are emission spectra obtained as the luminescent materials of Reference Examples 17-20 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0005">FIG. 9</figref> are emission spectra obtained as the luminescent materials of Reference Examples 21-23 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0005">FIG. 10</figref> are emission spectra obtained as the luminescent materials of Reference Examples 24-26 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0006">FIG. 11</figref> are emission spectra obtained as the luminescent materials of Reference Examples 27-29 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0006">FIG. 12</figref> is an emission spectrum obtained as the luminescent material of Reference Example 30 was excited by light having a wavelength of 457 nm;</li><li><figref idref="f0007">FIG. 13</figref> are emission spectra obtained as the luminescent materials of Examples 1-4 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0007">FIG. 14</figref> is an emission spectrum obtained as the luminescent material of Example 5 was excited by light having a wavelength of 461 nm;</li><li><figref idref="f0008">FIG. 15</figref> are emission spectra obtained as the luminescent materials of Examples 6 and 7 were excited by light having a wavelength of 461 nm;</li><li><figref idref="f0008">FIG. 16</figref> are emission spectra obtained as the luminescent materials of Examples 8-11 were excited by light having a wavelength of 461 nm;</li><li><figref idref="f0009">FIG. 17</figref> are emission spectra obtained as the luminescent materials of Examples 12-14;</li><li><figref idref="f0009">FIG. 18</figref> are emission spectra obtained as the luminescent materials of Reference Examples 31-34 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0010">FIG. 19</figref> are emission spectra obtained as the luminescent materials of Reference Examples 35-38 were excited by light having a wavelength of 457 nm;</li><li><figref idref="f0010">FIG. 20</figref> is an emission spectrum obtained as the luminescent material of Reference Example 39 was excited by light having a wavelength of 457 nm;</li><li><figref idref="f0011">FIG. 21</figref> are XRD profiles of the luminescent materials of Comparative Examples 3-5, Reference Example 20 and Example 2;</li><li><figref idref="f0011">FIG. 22</figref> are emission spectra obtained as the luminescent materials of Comparative Examples 3-5, Reference Example 20 and Example 2 were excited by light having a wavelength of 390 nm;</li><li><figref idref="f0012">FIG. 23</figref> is a graph illustrating the temperature characteristics, relative to emission intensity, of the luminescent materials of Reference Examples 20 and 39 and Comparative Examples 1 and 2 as they were excited by light having a wavelength of 461 nm; and</li><li><figref idref="f0012">FIG. 24</figref> is a graph illustrating the temperature characteristics, relative to emission intensity, of the luminescent materials of Examples 1 and Comparative Example 6 as they were excited by light having a wavelength of 461 nm.</li></ul>

Best Mode for Carrying Out the Invention

0010Next, various embodiments of the present invention will be explained.

0011It has been found out by the present inventors that it is possible to obtain a luminescent material which is excellent in temperature characteristics through the addition of a luminescence center element to a sialon-based compound having a specific composition. This sialon-based compound in this specification can be represented by the following composition formula (A). MAlSiON (A) In this composition formula (A), M is Sr.

0012In the creation of the luminescent material according to this embodiment, at least part of the metallic element M in the sialon-based compound is replaced by a luminescence center element and the constituent elements of the composition are respectively regulated to a predetermined range. The luminescent material according to this embodiment can be considered as represented by the following composition formula (B) wherein the constituent elements thereof are respectively regulated to a predetermined range. (M1-xRx)aAlSibOcNd (B) As the luminescence center element R is Eu.

0013It is desirable that the luminescence center element R is substituted for at least 0.1 mole % of the metallic element M. If the amount of substitution is less than 0.1 mole %, it may become difficult to obtain sufficient light-emitting effects. Although the luminescence center element R may be employed to substitute all of the metallic element M, as long as the amount of substitution is limited to less than 50 mole %, it is possible to suppress most effectively the deterioration (concentration quenching) of emission efficiency.

0014A luminescent material according to one embodiment is featured in that it exhibits an emission peak at a wavelength ranging from 490 to 580 nm as it is excited by light having a wavelength ranging from 250 to 500 nm and that it has a composition represented by the following general formula (2): (M1-xRx)a2AlSib2Oc2Nd2 (2) (In the general formula (2), M is Sr; R is Eu; and x, a2, b2, c2 and d2 satisfy following relationships): <maths id="math0001"><math display="block"><mn mathvariant="normal">0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">x</mi><mo mathvariant="normal">≤</mo><mn mathvariant="normal">0.5</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">0.93</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">1.3</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">4.0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">b</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">5.8</mn></math><img file="EP2003183B1_D0001.tif" /></maths><maths id="math0002"><math display="block"><mrow><mn mathvariant="normal">0.6</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">c</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">6</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">d</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">11</mn><mo mathvariant="normal">)</mo></mrow><mn mathvariant="normal">.</mn></math><img file="EP2003183B1_D0002.tif" /></maths>

0015The luminescent material having the composition represented by the aforementioned general formula (2) may be classified as emitting a light zone ranging in color from green to yellowish green when excited with light having a wavelength ranging from 250 to 500 nm.

0016When Sr is included, as the metallic element M, in the aforementioned general formula (2), the luminescent material to be obtained is enabled to exhibit an X-ray diffraction profile as schematically shown in <figref idref="f0001">FIG. 1</figref> for example in the X-ray diffraction where CuKα characteristic X-rays (wavelength: 1.54056Å) is employed. As shown in <figref idref="f0001">FIG. 1</figref>, the luminescent material having the composition represented by the aforementioned general formula (2) contains one component concurrently indicating diffraction peaks at diffraction angles (2θ) of 11.81-11.85, 15.34-15.38, 20.40-20.47 and 23.74-23.86°.

0017Since this luminescent material is formulated to have a composition wherein the contents of constituent elements thereof are respectively confined to a specific range, this luminescent material is enabled to exhibit excellent temperature characteristics.

0018The luminescent material according to this embodiment can be synthesized using, as starting materials, the carbonates, nitrides or oxides of the metallic element M; carbides of cyanamide; the nitrides, oxides or carbide of Al or Si; and the oxides, nitrides or carbonates of the luminescence center element R. More specifically, to obtain a luminescent material containing Eu as a luminescence center element R, SrCO3, AlN, Si3N4 and Eu2O3 can be employed as starting materials. More specifically, these starting materials are weighed and mixed together so as to obtain a mixed powder having a desired composition, which is then sintered to obtain the aimed luminescent material. In the step of mixing these starting materials, it is possible to employ a ball mill in which these starting materials are mixed together with, for example, dehydrated isopropanol (IPA) for 2 to 72 hours. It is also possible to employ, other than the aforementioned IPA, other organic solvent such as ethanol or an aqueous solution. The mixing of these starting materials may be performed by either dry mixing in a mortar or wet mixing methods.

0019The IPA is then volatilized and removed by room temperature drying or heat-drying using a mantle heater. Thereafter, the resultant mixture is allowed to dry overnight in air atmosphere at a temperature ranging from 0 to 40°C and then ground in a mortar and charged in a carbon crucible. The drying of the mixture may be performed using a hot plate as desired. Further, as the material of the crucible, it may be boron nitride, silicon nitride, silicon carbide, aluminum nitride, sialon, aluminum oxide, molybdenum or tungsten.

0020The mixture in the crucible is then subjected to sintering for a predetermined period of time to obtain a luminescent material having a predetermined composition. The pressure in the sintering step should preferably be higher than atmospheric pressure. In order to suppress the decomposition of silicon nitride at high temperatures, the pressure in this sintering step should preferably be 5 atm or more. As for the sintering temperature, it should preferably be confined within the range of 1500 to 2000°C, more preferably the range of 1800 to 2000°C. If the sintering temperature is lower than 1500°C, it may become difficult to create the sialon. On the other hand, if the sintering temperature is higher than 2000°C, the materials or products may sublime. Further, since AlN employed as a raw material is vulnerable to oxidation, the sintering should preferably be performed in a nitrogen atmosphere. Alternatively, the sintering may be performed in a mixed gas atmosphere consisting of nitrogen and hydrogen.

0021The powder that has been sintered is optionally subjected to post treatments such as washing to obtain a luminescent material according to one embodiment. The washing can be performed by washing with pure water or by acid washing for example. It should be noted that, as for the conventional nitride luminescent material, there is also known CaAlSiN3:Eu, which can be synthesized using Ca3N2, etc., as raw materials. Since this raw material is anaerobic, the weighing and mixing of raw materials on the occasion of the synthesis of luminescent material are required to be performed in an environment which is sealed off from air atmosphere, e.g., in a glove box. Whereas, in the case of synthesizing a luminescent material according to this embodiment however, the weighing and mixing of raw materials can be performed in air atmosphere. The reason for this can be ascribed to the fact that the reactivity in air atmosphere of the raw materials of luminescent material according to this embodiment is lower than that of the aforementioned Ca3N2. Therefore, the luminescent material according to this embodiment can be manufactured in a very simple process, thereby making it possible to remarkably reduce the manufacturing cost.

0022The luminescent material according to this embodiment can be applied to the manufacture of a white LED. More specifically, it is possible to obtain white light by suitably combining plural kinds of luminescent materials. For example, plural kinds of luminescent materials respectively emitting red, yellow (or green) or blue light as they are irradiated with ultraviolet rays can be combined to obtain white light. Alternatively, it is also possible to combine plural kinds of luminescent materials respectively emitting yellow or red light (a luminescent material which is capable of emitting red light may be omitted if required) as they are irradiated with blue light.

0023In the light-emitting device shown in <figref idref="f0001">FIG. 2</figref>, a resin stem 200 comprises a lead 201 and a lead 202 both forming a lead frame, and a resin part 203 which is formed integral with these leads 201 and 202. This resin part 203 is provided with a recess 205 having an upper opening which is made larger in width than that of the bottom thereof and with a reflection surface 204 on the sidewall of recess 205.

0024A light-emitting chip 206 is mounted at a central portion of nearly circular bottom of the recess 205 by silver paste, etc. As for the light-emitting chip 206, it is possible to employ, for example, a light-emitting diode, a laser diode, etc. Alternatively, it is also possible to employ those which are capable of emitting ultraviolet rays. Namely, there is not any particular limitation with respect to the kinds of the light-emitting chip 206. Thus, it is possible to employ, other than the ultraviolet-ray-emitting chip, a chip which is capable of emitting blue, bluish purple, or near-ultraviolet light. For example, it is possible to employ a semiconductor light-emitting element such as GaN, etc. The electrodes (not shown) of the light-emitting chip 206 are electrically connected, through bonding wires 207 and 208 made of gold, etc., with the lead 201 and the lead 202, respectively. It should be noted that the arrangement of these leads 201 and 202 can be optionally modified.

0025A luminous layer 209 is placed in the recess 205 of resin part 203. This luminous layer 209 can be formed by dispersing or sedimenting a luminescent material 210 according to one embodiment in a resin layer 211 made of silicone resin for example at a concentration ranging from 5 to 50% by weight. In the luminescent material according to this embodiment, a nitride which is high in covalent boding property is employed as a matrix. Because of this, the luminescent material is rendered hydrophobic and hence very excellent in affinity with the resin. Therefore, it is possible to effectively suppress the scattering of light at the interface of resin and luminescent material, and the light extraction efficiency is improved.

0026As the light-emitting chip 206, it is possible to employ a flip-chip where an n-type electrode and a p-type electrode are positioned on the same plane. In this case, it is possible to overcome the problems originating from wire such as the cut-off or peeling of wire and the absorption of light by the wire, thus making it possible to obtain a semiconductor light-emitting device which is high in reliability and also high in luminance. Further, it is also possible to employ an n-type substrate for the light-emitting chip 206 to fabricate the following structure. More specifically, an n-type electrode is formed on the rear face of an n-type substrate, a p-type electrode is formed on the upper face of a semiconductor layer formed on the substrate, and the n-type electrode or the p-type electrode is mounted on one of leads. The rest of the p-type electrode and the n-type electrode are electrically connected through a wire with the other lead. The size of the light-emitting chip 206, the dimension and configuration of the recess 205 may be optionally modified.

0027It should be noted that the kinds of light-emitting device to which the luminescent material of this embodiment is applicable can be optionally changed. More specifically, even to a bombshell-type LED and a surface-mounted type LED, the luminescent material of this embodiment can be applied while securing the same effects as described above.

0028Next, the present invention will be explained in detail with reference to examples and comparative examples. These examples however are not intended to limit the present invention.

(Reference Example 1)

0029SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 25.687, 8.198, 46.770 and 4.575g, respectively. Then, these starting materials were mixed together with dehydrated isopropanol (IPA) for 24 hours in a ball mill. After IPA was volatilized and removed by drying at room temperature, the mixture was allowed to dry overnight in air atmosphere and at a temperature of 120°C. The resultant mixture was ground in a mortar and then charged in a carbon crucible. The mixture in the crucible was then subjected to sintering in a nitrogen atmosphere of 7.5 atm. for eight hours at a temperature of 1900°C to synthesize a luminescent material of this reference example.

0030This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body colors, and a white sintered powder and a red sintered powder were confirmed. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 2)

0031A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 1 except that the loading of SrCO3 was changed to 25.097g and the loading of Eu2O3 was changed to 5.279g.

0032This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 3)

0033A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 1 except that the loading of SrCO3 was changed to 24.506g and the loading of Eu2O3 was changed to 5.983g.

0034This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 4)

0035A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 1 except that the loading of SrCO3 was changed to 7.012g and the loading of Eu2O3 was changed to 0.440g.

0036This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

0037The red powder of Reference Example 1 was taken out of the crucible and ground in a mortar. This red powder was excited by an emission diode exhibiting a peak wavelength of 457 nm to observe the emission spectrum of the red powder. The red powders of Reference Examples 2 to 4 were also respectively taken out and ground in the same manner as the red powder of Reference Example 1 and excited using light having a peak wavelength of 457 nm to observe the emission spectrum of each of the red powders of Reference Examples 2 to 4.

0038The results thus obtained are shown in <figref idref="f0002">FIG. 3</figref>. In <figref idref="f0002">FIG. 3</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 620 to 640 nm was obtained. By the expression "single-band", it is intended to indicate an emission which appears as if the peak wavelength where the emission intensity becomes maximal is only one.

(Reference Example 5)

0039A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 1 except that the sintering temperature was changed to 1950°C.

0040This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 6)

0041A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 2 except that the sintering temperature was changed to 1950°C.

0042This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 7)

0043A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 3 except that the sintering temperature was changed to 1950°C.

0044This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 8)

0045A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 4 except that the sintering temperature was changed to 1950°C.

0046This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

0047The red powders of Reference Examples 5 to 8 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0002">FIG. 4</figref>. In <figref idref="f0002">FIG. 4</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 620 to 640 nm was obtained.

0048The red powders of Reference Examples 1-4, 7 and 8 were subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å). The profiles thus obtained are shown in <figref idref="f0003">FIG. 5</figref>. As shown in <figref idref="f0003">FIG. 5</figref>, since the profiles shown therein contained a large number of peaks, these red powders were assumed as having a relatively complicated structure.

0049It will be recognized that every red powders concurrently indicate diffraction peaks at diffraction angles (2θ) of 8.60-8.64, 11.16-11.20 and 18.26-18.30°. It was suggested that the peaks on the lower angle side were relatively large in unit lattice.

0050When this profile was collated with the JPCDS cards, there were no JPCDS cards data on existing substances which were identical with this profile. It should be noted that the JPCDS cards are a data book in which the peak profiles of various kinds of substances as obtained by X-ray diffraction are summarized.

0051It was found as a result of index numbering of peaks of the profile of red powder of Reference Example 1 that the lattice size of the red powder was quite identical with the space group Pnma, Pnc2 (rhombic system) of 11.7×4.96×21.4Å. Further, as a result of the index numbering of peaks of the profile of red powder of Reference Example 2, it was found that the lattice size of the red powder was quite identical with the space group Pnma (rhombic system) P21/c (monoclinic system) of 11.7×4.96×21.4Å. It will be recognized from these results that these luminescent materials were at least formed of rhombic system and the lattice size thereof was around 12×5×21Å.

(Reference Example 9)

0052A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 2 except that the sintering temperature was changed to 1850°C.

0053This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 10)

0054A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 3 except that the sintering temperature was changed to 1850°C.

0055This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 11)

0056A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 4 except that the sintering temperature was changed to 1850°C.

0057This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

0058The red powders of Reference Examples 9 to 11 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0003">FIG. 6</figref>. In <figref idref="f0003">FIG. 6</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 610 to 620 nm was obtained.

(Reference Example 12)

0059A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 1 except that the loading of SrCO3 was changed to 13.287g and the loading of Eu2O3 was changed to 1.760g.

0060This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 13)

0061A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 12 except that the sintering temperature was changed to 1800°C.

0062This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 14)

0063A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 2 except that the sintering temperature was changed to 1800°C.

0064This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 15)

0065A luminescent material was synthesized in this reference example under the same conditions as described in Reference Example 4 except that the sintering temperature was changed to 1800°C.

0066This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 16)

0067A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 14 except that the crucible was changed to a boron nitride crucible.

0068This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

0069The red powders of Reference Examples 12 to 16 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0004">FIG. 7</figref>. In <figref idref="f0004">FIG. 7</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 600 to 630 nm was obtained.

(Reference Example 17)

0070A luminescent material was synthesized in this reference example by following the same procedures as described in Reference Example 2 except that the sintering time period was changed to 16 hours.

0071This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a red emission from the red powder were observed.

(Reference Example 18)

007231.371g of SrCO3, 12.296g of AlN, 46.770g of Si3N4 and 6.599g of Eu2O3 were prepared as starting materials. Then, a luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 1 except that the sintering conditions thereof were changed to 1750°C in temperature and 20 hours in sintering time.

0073This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 19)

0074A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 1 except that the sintering conditions thereof were changed to 1850°C in temperature and 16 hours in sintering time.

0075This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 20)

0076A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 2 except that the sintering conditions thereof were changed to 1850°C in temperature and 16 hours in sintering time.

0077This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

0078The red powders of Reference Examples 17 to 20 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0004">FIG. 8</figref>. In <figref idref="f0004">FIG. 8</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 616 to 618 nm was obtained.

0079The red powders of Reference Examples 1 to 4, 7, 8 and 17 were sorted out to perform the chemical analysis thereof, the results being summarized in the following Table 1. In this Table 1, there are shown the values of "a", "b", "c" and "d" in the aforementioned general formula (B). <tables id="tabl0001" num="0001"><table frame="all"><title>Table 1</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="13mm" /><colspec colnum="3" colname="col3" colwidth="12mm" /><colspec colnum="4" colname="col4" colwidth="13mm" /><colspec colnum="5" colname="col5" colwidth="12mm" /><thead><row><entry align="center" /><entry align="center">a</entry><entry align="center">b</entry><entry align="center">c</entry><entry align="center">d</entry></row></thead><tbody><row><entry valign="bottom">Ref. Ex.1</entry><entry align="center" valign="bottom">0.858</entry><entry align="center" valign="bottom">3.34</entry><entry align="center" valign="bottom">0.350</entry><entry align="center" valign="bottom">4.92</entry></row><row><entry valign="bottom">Ref. Ex.2</entry><entry align="center" valign="bottom">0.935</entry><entry align="center" valign="bottom">3.41</entry><entry align="center" valign="bottom">0.418</entry><entry align="center" valign="bottom">5.18</entry></row><row><entry valign="bottom">Ref. Ex.3</entry><entry align="center" valign="bottom">0.868</entry><entry align="center" valign="bottom">3.58</entry><entry align="center" valign="bottom">0.270</entry><entry align="center" valign="bottom">5.42</entry></row><row><entry valign="bottom">Ref. Ex.4</entry><entry align="center" valign="bottom">0.911</entry><entry align="center" valign="bottom">3.70</entry><entry align="center" valign="bottom">0.272</entry><entry align="center" valign="bottom">5.63</entry></row><row><entry valign="bottom">Ref. Ex.7</entry><entry align="center" valign="bottom">0.839</entry><entry align="center" valign="bottom">3.37</entry><entry align="center" valign="bottom">0.283</entry><entry align="center" valign="bottom">5.18</entry></row><row><entry valign="bottom">Ref. Ex.8</entry><entry align="center" valign="bottom">0.845</entry><entry align="center" valign="bottom">3.34</entry><entry align="center" valign="bottom">0.281</entry><entry align="center" valign="bottom">5.14</entry></row><row><entry valign="bottom">Ref. Ex.17</entry><entry align="center" valign="bottom">0.680</entry><entry align="center" valign="bottom">2.54</entry><entry align="center" valign="bottom">0.332</entry><entry align="center" valign="bottom">4.29</entry></row></tbody></tgroup></table></tables>

(Reference Example 21)

0080A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 12 except that the sintering conditions thereof were changed to 1800°C in temperature and 16 hours in sintering time.

0081This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 22)

0082A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 1 except that the sintering conditions thereof were changed to 1800°C in temperature and 16 hours in sintering time.

0083This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 23)

0084A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 3 except that the sintering conditions thereof were changed to 1800°C in temperature and 16 hours in sintering time.

0085This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

0086The red powders of Reference Examples 21 to 23 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0005">FIG. 9</figref>. In <figref idref="f0005">FIG. 9</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 615 to 645 nm was obtained.

(Reference Example 24)

0087A raw material powder that had been mixed, dried and ground in the same manner as that of Reference Example 1 was placed in a boron nitride crucible. Thereafter, the raw material powder was sintered for 24 hours at a temperature of 1900°C in a nitrogen atmosphere of 7.5 atm. Then, the sintering of the raw material powder was continued for 64 hours at a temperature of 1800°C, thereby synthesizing the luminescent material of this reference example.

0088This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 25)

0089A raw material powder that had been mixed, dried and ground in the same manner as that of Reference Example 2 was placed in a boron nitride crucible. Thereafter, the raw material powder was sintered for 24 hours at a temperature of 1900°C in a nitrogen atmosphere of 7.5 atm. Then, the sintering of the raw material powder was continued for 64 hours at a temperature of 1800°C, thereby synthesizing the luminescent material of this reference example.

0090This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

(Reference Example 26)

0091A raw material powder that had been mixed, dried and ground in the same manner as that of Reference Example 3 was placed in a boron nitride crucible. Thereafter, the raw material powder was sintered for 24 hours at a temperature of 1900°C in a nitrogen atmosphere of 7.5 atm. Then, the sintering of the raw material powder was continued for 64 hours at a temperature of 1800°C, thereby synthesizing the luminescent material of this reference example.

0092This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder, and a yellowish green emission from the yellowish green powder were observed.

0093The red powders of Reference Examples 24 to 26 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0005">FIG. 10</figref>. In <figref idref="f0005">FIG. 10</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every red powders, a single-band emission exhibiting a peak at a wavelength ranging from 580 to 610 nm was obtained.

(Reference Example 27)

0094SrCO3, AlN, Si3N4 and Eu2O3 were employed as starting materials, and these starting materials were weighed to obtain 0.664, 0.410, 0.702 and 0.088g, respectively. Then, these starting materials were sufficiently mixed together in a mortar and then charged in a carbon crucible. The mixture in the crucible was then subjected to sintering in a nitrogen atmosphere of 7.5 atm. for four hours at a temperature of 1800°C, thereby synthesizing a luminescent material of this reference example.

0095This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and an orange emission from the orange powder were observed.

(Reference Example 28)

0096SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 1.417, 0.820, 1.403 and 0.070g, respectively. Then, these starting materials were sufficiently mixed together in a mortar and then charged in a carbon crucible. The mixture in the crucible was then subjected to sintering in a nitrogen atmosphere of 7.5 atm. for ten hours at a temperature of 1800°C, thereby synthesizing a luminescent material of this reference example.

0097This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and an orange emission from the orange powder were observed.

(Reference Example 29)

0098SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 1.402, 0.820, 1.403 and 0.088g, respectively. Then, these starting materials were sufficiently mixed together in a mortar and then charged in a carbon crucible. The mixture in the crucible was then subjected to sintering in a nitrogen atmosphere of 7.5 atm. for ten hours at a temperature of 1800°C, thereby synthesizing a luminescent material of this reference example.

0099This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and an orange emission from the orange powder were observed.

0100The orange powders of Reference Examples 27 to 29 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the orange powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0006">FIG. 11</figref>. In <figref idref="f0006">FIG. 11</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every orange powder, a single-band emission exhibiting a peak at a wavelength ranging from 587 to 606 nm was obtained.

(Reference Example 30)

0101A luminescent material of this reference example was synthesized by following the same procedures as described in Reference Example 18 except that the sintering conditions thereof were changed to 1800°C in temperature and 16 hours in sintering time.

0102This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and an orange emission from the orange powder were observed.

0103The red powder of Reference Example 30 was taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powder was excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrum thus obtained is shown in <figref idref="f0006">FIG. 12</figref>. In <figref idref="f0006">FIG. 12</figref>, the band exhibiting a peak at 457 nm was derived from the reflection of exciting beam. <figref idref="f0006">FIG. 12</figref> clearly indicates a single-band emission exhibiting a peak at a wavelength of 611 nm.

0104The values of absorption coefficient, quantum yield and luminous efficiency of the red powders of Reference Examples 1-26, the orange powders of Reference Examples 27-29 and the red powder of Reference Example 30 are summarized in the following Table 2. <tables id="tabl0002" num="0002"><table frame="all"><title>Table 2</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="36mm" /><colspec colnum="3" colname="col3" colwidth="35mm" /><colspec colnum="4" colname="col4" colwidth="33mm" /><colspec colnum="5" colname="col5" colwidth="40mm" /><thead><row><entry align="center" valign="middle" /><entry align="center" valign="middle">Peak wavelength (nm)</entry><entry align="center" valign="middle">Absorption coefficient</entry><entry align="center" valign="middle">Quantum efficiency</entry><entry align="center" valign="middle">Luminescence efficiency</entry></row></thead><tbody><row><entry align="center" valign="bottom">Ref. Ex.1</entry><entry align="center" valign="bottom">622</entry><entry align="center" valign="bottom">0.83</entry><entry align="center" valign="bottom">0.23</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.2</entry><entry align="center" valign="bottom">631</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.22</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.3</entry><entry align="center" valign="bottom">633</entry><entry align="center" valign="bottom">0.87</entry><entry align="center" valign="bottom">0.17</entry><entry align="center" valign="bottom">0.15</entry></row><row><entry align="center" valign="bottom">Ref. Ex.4</entry><entry align="center" valign="bottom">642</entry><entry align="center" valign="bottom">0.93</entry><entry align="center" valign="bottom">0.12</entry><entry align="center" valign="bottom">0.11</entry></row><row><entry align="center" valign="bottom">Ref. Ex.5</entry><entry align="center" valign="bottom">630</entry><entry align="center" valign="bottom">0.79</entry><entry align="center" valign="bottom">0.22</entry><entry align="center" valign="bottom">0.18</entry></row><row><entry align="center" valign="bottom">Ref. Ex.6</entry><entry align="center" valign="bottom">628</entry><entry align="center" valign="bottom">0.81</entry><entry align="center" valign="bottom">0.17</entry><entry align="center" valign="bottom">0.14</entry></row><row><entry align="center" valign="bottom">Ref. Ex.7</entry><entry align="center" valign="bottom">630</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.16</entry><entry align="center" valign="bottom">0.14</entry></row><row><entry align="center" valign="bottom">Ref. Ex.8</entry><entry align="center" valign="bottom">640</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.13</entry><entry align="center" valign="bottom">0.11</entry></row><row><entry align="center" valign="bottom">Ref. Ex.9</entry><entry align="center" valign="bottom">614</entry><entry align="center" valign="bottom">0.79</entry><entry align="center" valign="bottom">0.33</entry><entry align="center" valign="bottom">0.26</entry></row><row><entry align="center" valign="bottom">Ref. Ex.10</entry><entry align="center" valign="bottom">617</entry><entry align="center" valign="bottom">0.81</entry><entry align="center" valign="bottom">0.32</entry><entry align="center" valign="bottom">0.26</entry></row><row><entry align="center" valign="bottom">Ref. Ex.11</entry><entry align="center" valign="bottom">621</entry><entry align="center" valign="bottom">0.88</entry><entry align="center" valign="bottom">0.25</entry><entry align="center" valign="bottom">0.22</entry></row><row><entry align="center" valign="bottom">Ref. Ex.12</entry><entry align="center" valign="bottom">626</entry><entry align="center" valign="bottom">0.74</entry><entry align="center" valign="bottom">0.29</entry><entry align="center" valign="bottom">0.21</entry></row><row><entry align="center" valign="bottom">Ref. Ex.13</entry><entry align="center" valign="bottom">602</entry><entry align="center" valign="bottom">0.78</entry><entry align="center" valign="bottom">0.32</entry><entry align="center" valign="bottom">0.25</entry></row><row><entry align="center" valign="bottom">Ref. Ex.14</entry><entry align="center" valign="bottom">619</entry><entry align="center" valign="bottom">0.78</entry><entry align="center" valign="bottom">0.38</entry><entry align="center" valign="bottom">0.29</entry></row><row><entry align="center" valign="bottom">Ref. Ex.15</entry><entry align="center" valign="bottom">629</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.29</entry><entry align="center" valign="bottom">0.25</entry></row><row><entry align="center" valign="bottom">Ref. Ex.16</entry><entry align="center" valign="bottom">628</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.42</entry><entry align="center" valign="bottom">0.36</entry></row><row><entry align="center" valign="bottom">Ref. Ex.17</entry><entry align="center" valign="bottom">616</entry><entry align="center" valign="bottom">0.82</entry><entry align="center" valign="bottom">0.37</entry><entry align="center" valign="bottom">0.30</entry></row><row><entry align="center" valign="bottom">Ref. Ex.18</entry><entry align="center" valign="bottom">618</entry><entry align="center" valign="bottom">0.88</entry><entry align="center" valign="bottom">0.32</entry><entry align="center" valign="bottom">0.28</entry></row><row><entry align="center" valign="bottom">Ref. Ex.19</entry><entry align="center" valign="bottom">618</entry><entry align="center" valign="bottom">0.86</entry><entry align="center" valign="bottom">0.22</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.20</entry><entry align="center" valign="bottom">617</entry><entry align="center" valign="bottom">0.88</entry><entry align="center" valign="bottom">0.24</entry><entry align="center" valign="bottom">0.21</entry></row><row><entry align="center" valign="bottom">Ref. Ex.21</entry><entry align="center" valign="bottom">616</entry><entry align="center" valign="bottom">0.90</entry><entry align="center" valign="bottom">0.16</entry><entry align="center" valign="bottom">0.15</entry></row><row><entry align="center" valign="bottom">Ref. Ex.22</entry><entry align="center" valign="bottom">627</entry><entry align="center" valign="bottom">0.91</entry><entry align="center" valign="bottom">0.20</entry><entry align="center" valign="bottom">0.18</entry></row><row><entry align="center" valign="bottom">Ref. Ex.23</entry><entry align="center" valign="bottom">645</entry><entry align="center" valign="bottom">0.91</entry><entry align="center" valign="bottom">0.21</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.24</entry><entry align="center" valign="bottom">614</entry><entry align="center" valign="bottom">0.71</entry><entry align="center" valign="bottom">0.44</entry><entry align="center" valign="bottom">0.31</entry></row><row><entry align="center" valign="bottom">Ref. Ex.25</entry><entry align="center" valign="bottom">647</entry><entry align="center" valign="bottom">0.72</entry><entry align="center" valign="bottom">0.37</entry><entry align="center" valign="bottom">0.27</entry></row><row><entry align="center" valign="bottom">Ref. Ex.26</entry><entry align="center" valign="bottom">646</entry><entry align="center" valign="bottom">0.77</entry><entry align="center" valign="bottom">0.34</entry><entry align="center" valign="bottom">0.26</entry></row><row><entry align="center" valign="bottom">Ref. Ex.27</entry><entry align="center" valign="bottom">604</entry><entry align="center" valign="bottom">0.77</entry><entry align="center" valign="bottom">0.32</entry><entry align="center" valign="bottom">0.24</entry></row><row><entry align="center" valign="bottom">Ref. Ex.28</entry><entry align="center" valign="bottom">587</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.35</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.29</entry><entry align="center" valign="bottom">587</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.35</entry><entry align="center" valign="bottom">0.19</entry></row><row><entry align="center" valign="bottom">Ref. Ex.30</entry><entry align="center" valign="bottom">587</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.35</entry><entry align="center" valign="bottom">0.19</entry></row></tbody></tgroup></table></tables>

0105As shown in Table 2, all of the red powders of Reference Examples 1-26, the orange powders of Reference Examples 27-29 and the red powder of Reference Example 30 were capable of exhibiting an emission wavelength falling within the range of 580 to 700 nm as they were excited by the light having a wavelength ranging from 250 to 500 nm. The absorption coefficient, quantum yield and luminous efficiency of these luminescent materials were by no means inferior to the conventional red-type luminescent materials such for example as Sr2Si5N8Eu, etc.

0106It should be noted that, even if the exciting wavelength was changed to 254, 365, 390 or 460 nm, it was possible to confirm the emission having a peak in the aforementioned wavelength range. Because of the facts that if the exciting wavelength is too short, the loss due to Stokes shift would become prominent and that if the exciting wavelength is too long, the excitation efficiency would be deteriorated, the exciting wavelength should preferably be confined within the range of 380 to 460 nm. Further, the peak wavelength of emission should desirably be confined to 670 nm or less.

0107With respect to the compositions of red powders of Reference Examples 1-4, 7, 8 and 17, they are already shown in Table 1. The red powders and orange powders of other Reference Examples were also chemically analyzed to investigate the values of "a", "b", "c" and "d" in the aforementioned general formula (B).

0108As a result, it was found out that, in the cases of the red powders of Reference Examples 1-26, the orange powders of Reference Examples 27-29 and the red powder of Reference Example 30, the upper limit of the value of "a" was 0.948 and the lower limit thereof was 0.605. With respect to the upper limit and the lower limit of the value of "b", they were 3.88 and 2.10, respectively. With respect to the upper limit and the lower limit of the value of "c", they were 0.446 and 0.253, respectively. Further, with respect to the upper limit and the lower limit of the value of "d", they were 5.68 and 4.05, respectively.

0109Based on these results, the compositions of red powders of Reference Examples 1-26, the orange powders of Reference Examples 27-29 and the red powder of Reference Example 30 were found definable by the following general formula (1). (M1-xRx)alAlSiblOclNdl (1)

0110In the general formula (1), M is at least one metallic element excluding Si and Al; R is a luminescence center element; and x, a1, b1, c1 and d1 satisfy following relationships: <maths id="math0003"><math display="block"><mn mathvariant="normal">0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">x</mi><mo mathvariant="normal">≤</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">0.6</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">0.95</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">b</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">3.9</mn></math><img file="EP2003183B1_D0003.tif" /></maths><maths id="math0004"><math display="block"><mn mathvariant="normal">0.25</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">c</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">0.45</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">4</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">d</mi><mo>⁢</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">5.7</mn></math><img file="EP2003183B1_D0004.tif" /></maths>

0111When all of the compositions of red powders of Reference Examples 1-26, the orange powders of Reference Examples 27-29 and the red powder of Reference Example 30 were subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), they exhibited concurrently diffraction peaks at least at diffraction angles (2θ) of 8.60-8.64, 11.16-11.20 and 18.26-18.30°.

(Example 1)

0112A luminescent material was synthesized in this example by following the same procedures as described in Reference Example 21 except that the sintering conditions thereof were changed to 1800°C in temperature and 72 hours in sintering time.

0113This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a yellowish green sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a yellowish green emission from the yellowish green powder and an orange emission from the orange powder were observed.

(Example 2)

0114A luminescent material was synthesized in this example by following the same procedures as described in Reference Example 22 except that the sintering conditions thereof were changed to 1800°C in temperature and 72 hours in sintering time.

0115This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a yellowish green sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a yellowish green emission from the yellowish green powder and an orange emission from the orange powder were observed.

(Example 3)

0116A luminescent material was synthesized in this example by following the same procedures as described in Reference Example 23 except that the sintering conditions thereof were changed to 1800°C in temperature and 72 hours in sintering time.

0117This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a yellowish green sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a yellowish green emission from the yellowish green powder and an orange emission from the orange powder were observed.

0118When this yellowish green powder was subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 11.831, 15.361, 20.451 and 23.840°.

(Example 4)

0119A luminescent material was synthesized in this example by following the same procedures as described in Reference Example 24 except that the sintering conditions thereof were changed to 1800°C in temperature and 72 hours in sintering time.

0120This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a yellowish green sintered powder and an orange sintered powder. When this luminescent material was excited by black light, a yellowish green emission from the yellowish green powder and an orange emission from the orange powder were observed.

0121The yellowish green powders of Examples 1 to 4 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the yellowish green powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0007">FIG. 13</figref>. In <figref idref="f0007">FIG. 13</figref>, the bands each exhibiting a peak at 457 nm were derived from the reflection of exciting beam. From every yellowish green powders, a single-band emission exhibiting a peak at a wavelength ranging from 522 to 524 nm was obtained.

0122The yellowish green powder of Example 3 was sorted out from the crucible to perform the chemical analysis thereof, the results being indicated in the following Table 3. In this Table 3, there are shown the values of "a", "b", "c" and "d" in the aforementioned general formula (B). <tables id="tabl0003" num="0003"><table frame="all"><title>Table 3</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="12mm" /><colspec colnum="2" colname="col2" colwidth="13mm" /><colspec colnum="3" colname="col3" colwidth="12mm" /><colspec colnum="4" colname="col4" colwidth="12mm" /><colspec colnum="5" colname="col5" colwidth="12mm" /><thead><row><entry align="center" valign="top" /><entry align="center" valign="top">a</entry><entry align="center" valign="top">b</entry><entry align="center" valign="top">c</entry><entry align="center" valign="top">d</entry></row></thead><tbody><row><entry align="center">Ex.3</entry><entry align="center">0.940</entry><entry align="center">4.15</entry><entry align="center">0.63</entry><entry align="center">6.30</entry></row></tbody></tgroup></table></tables>

0123The values of absorption coefficient, quantum yield and luminous efficiency of the yellowish green powders of Examples 1-4 as they were excited by the light having a wavelength of 457 nm are summarized in the following Table 4. <tables id="tabl0004" num="0004"><table frame="all"><title>Table 4</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="12mm" /><colspec colnum="2" colname="col2" colwidth="36mm" /><colspec colnum="3" colname="col3" colwidth="35mm" /><colspec colnum="4" colname="col4" colwidth="33mm" /><colspec colnum="5" colname="col5" colwidth="40mm" /><thead><row><entry align="center" valign="middle" /><entry align="center" valign="middle">Peak wavelength (nm)</entry><entry align="center" valign="middle">Absorption coefficient</entry><entry align="center" valign="middle">Quantum efficiency</entry><entry align="center" valign="middle">Luminescence efficiency</entry></row></thead><tbody><row><entry align="center" valign="bottom">Ex.1</entry><entry align="center" valign="bottom">522</entry><entry align="center" valign="bottom">0.84</entry><entry align="center" valign="bottom">0.48</entry><entry align="center" valign="bottom">0.40</entry></row><row><entry align="center" valign="bottom">Ex.2</entry><entry align="center" valign="bottom">522</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">0.48</entry><entry align="center" valign="bottom">0.40</entry></row><row><entry align="center" valign="bottom">Ex.3</entry><entry align="center" valign="bottom">524</entry><entry align="center" valign="bottom">0.83</entry><entry align="center" valign="bottom">0.45</entry><entry align="center" valign="bottom">0.38</entry></row><row><entry align="center" valign="bottom">Ex.4</entry><entry align="center" valign="bottom">524</entry><entry align="center" valign="bottom">0.80</entry><entry align="center" valign="bottom">0.45</entry><entry align="center" valign="bottom">0.36</entry></row></tbody></tgroup></table></tables>

0124As shown in Table 4, all of the yellowish green powders of Examples 1-4 were capable of exhibiting an emission wavelength falling within the range of 490 to 580 nm as they were excited by the light having a wavelength ranging from 250 to 500 nm. The absorption coefficient, quantum yield and luminous efficiency of these luminescent materials were by no means inferior to the conventional yellowish green luminescent materials such for example as (Ba,Sr)2SiO4:Eu, etc.

0125Further, the emission characteristics of the luminescent material of Example 2 as it was excited by the light having a wavelength of 450 nm were 87% in absorption coefficient, 48% in internal quantum yield and 42% in luminous efficiency. These results indicates that, as far as the yellowish green luminescent material of this embodiment is concerned, it has such emission characteristics that the excitation thereof using a wavelength of 450 nm is more advantageous in obtaining higher luminous efficiency than the excitation thereof using a wavelength of 460 nm.

0126It should be noted that <nplcit id="ncit0001" npl-type="s"><text>N. Hirosaki et al., Extended Abstracts (53rd Spring Meeting), The Japan Society of Applied Physics and Related Societies, 25p-ZR-11 (2006</text></nplcit>), describes that the emission characteristics of Eu-activated β sialon as it was excited by the light having a wavelength of 450 nm were 65% in absorption coefficient, 53% in internal quantum yield and 35% in luminous efficiency. <patcit id="pcit0001" dnum="JP2005255895A"><text>JP-A 2005-255895</text></patcit> (KOKAI) is a Patent Gazette related to the aforementioned Eu-activated β sialon. It will be recognized from the comparison between the luminous efficiency of this conventional luminescent material and the luminous efficiency of the luminescent material of this embodiment under the same condition with respect to the excitation wavelength that the yellowish green luminescent material of this embodiment is more excellent than the aforementioned conventional luminescent material.

0127Even if the exciting wavelength was changed to 254, 365, 390 or 460 nm, it was possible to confirm the emission having a peak in almost the same wavelength range as described above. Because of the facts that if the exciting wavelength is too short, the loss due to Stokes shift would become prominent and that if the exciting wavelength is too long, the excitation efficiency would be deteriorated, the exciting wavelength should preferably be confined within the range of 380 to 460 nm. Further, the peak wavelength of emission should desirably be confined to 560 nm or less. Additionally, the peak wavelength of emission should desirably be confined to 500 nm or more.

(Example 5)

0128SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 16.027, 4.837, 27.594 and 1.661g, respectively. Then, these starting materials were mixed together with dehydrated isopropanol (IPA) for 2 hours in a ball mill. IPA was volatilized and removed by drying using mantle heater. Thereafter, the resultant mixture was passed through a sieve having an aperture of 300 µm to prepare a raw material powder. The raw material powder thus obtained was allowed to naturally drop from sieve having an aperture of 500-1000 µm, thereby enabling a boron nitride crucible to be filled with the raw material powder. The raw material powder in the crucible was then subjected to sintering in a nitrogen atmosphere of 7 atm. for 12 hours at a temperature of 1800°C to synthesize a luminescent material of this reference example.

0129This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a yellowish green emission from the yellowish green powder were observed.

(Example 6)

0130A luminescent material was synthesized in this example by following the same procedures as described in Example 5 except that the loading of SrCO3, AlN, Si3N4 and Eu2O3 was changed to 16.298, 4.919, 25.256 and 1.689g, respectively. The raw material powder thus obtained was sintered for 6 hours at a temperature of 1850°C to synthesize a luminescent material of this reference example.

0131This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Example 7)

0132A luminescent material was synthesized in this example by following the same procedures as described in Example 6 except that the loading of Si3N4 was changed to 26.659g.

0133This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Example 8)

0134A luminescent material was synthesized in this example by following the same procedures as described in Example 7 except that the sintering conditions thereof were changed to 1800°Cin temperature and 16 hours in sintering time.

0135This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Example 9)

0136A luminescent material was synthesized in this example by following the same procedures as described in Example 5 except that the sintering time period thereof were changed to 16 hours.

0137This luminescent material thus sintered was formed of a mixture of three kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder, a red sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, a red emission from the red powder and a yellowish green emission from the yellowish green powder were observed.

(Example 10)

0138A luminescent material was synthesized in this example by following the same procedures as described in Example 9 except that the loading of Si3N4 was changed to 29.465g.

0139This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a yellowish green emission from the yellowish green powder were observed.

0140When this yellowish green powder was subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 11.870, 15.39, 20.47 and 23.79°.

(Example 11)

0141A luminescent material was synthesized in this example by following the same procedures as described in Example 9 except that the loading of Si3N4 was changed to 30.868g.

0142This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a yellowish green sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder and a yellowish green emission from the yellowish green powder were observed.

(Example 12)

0143A luminescent material was synthesized in this example by following the same procedures as described in Example 6 except that the loading of Si3N4 was changed to 29.465g and the sintering time period was changed to 10 hours. This luminescent material thus sintered was formed of a sintered powder exhibiting a body color of yellowish green. When this luminescent material was excited by black light, a yellowish green emission was observed.

(Example 13)

0144A luminescent material was synthesized in this example by following the same procedures as described in Example 5 except that the loading of SrCO3 was changed to 16.550g and the loading of Eu2O3 was changed to 1.038g. This luminescent material thus sintered was formed of a sintered powder exhibiting a body color of yellowish green. When this luminescent material was excited by black light, a yellowish green emission was observed.

(Example 14)

0145A luminescent material was synthesized in this example by following the same procedures as described in Example 12. This luminescent material thus sintered was formed of a sintered powder exhibiting a body color of yellowish green. When this luminescent material was excited by black light, a yellowish green emission was observed.

0146When this yellowish green powder was subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 11.87, 15.39, 20.47 and 23.85°.

0147The yellowish green powder of Example 5 was excited by an emission diode exhibiting a peak wavelength of 461 nm. The emission spectrum thus obtained is shown in <figref idref="f0007">FIG. 14</figref>. In <figref idref="f0007">FIG. 14</figref>, the band exhibiting a peak at 461 nm was derived from the reflection of exciting beam. From this yellowish green powder, a single-band emission exhibiting a peak wavelength falling within the range of 514 to 518 nm was obtained.

0148The yellowish green powders of Examples 6 and 7 were respectively excited by an emission diode exhibiting a peak wavelength of 461 nm. The emission spectrums thus obtained are shown in <figref idref="f0008">FIG. 15</figref>. In

0149<figref idref="f0008">FIG. 15</figref>, the band exhibiting a peak at 461 nm was derived from the reflection of exciting beam. From these yellowish green powders, a single-band emission exhibiting a peak wavelength at 517 nm was obtained.

0150The yellowish green powders of Examples 8 to 11 were respectively excited by an emission diode exhibiting a peak wavelength of 461 nm. The emission spectrums thus obtained are shown in <figref idref="f0008">FIG. 16</figref>. In <figref idref="f0008">FIG. 16</figref>, the band exhibiting a peak at 461 nm was derived from the reflection of exciting beam. From these yellowish green powders, a single-band emission exhibiting a peak wavelength falling within the range of 517 to 520 nm was obtained.

0151The yellowish green powders of Examples 12 to 14 were respectively excited by an emission diode exhibiting a peak wavelength of 461 nm. The emission spectrums thus obtained are shown in <figref idref="f0009">FIG. 17</figref>. In <figref idref="f0009">FIG. 17</figref>, the band exhibiting a peak at 461 nm was derived from the reflection of exciting beam. From these yellowish green powders, a single-band emission exhibiting a peak wavelength falling within the range of 517 to 520 nm was obtained.

0152The yellowish green luminescent materials of Examples 5, 7, and 10-14 were respectively sorted out from the crucible to perform the chemical analysis thereof, the results being summarized in the following Table 5. In this Table 5, there are shown the values of "a", "b", "c" and "d" in the aforementioned general formula (B). <tables id="tabl0005" num="0005"><table frame="all"><title>Table 5</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="14mm" /><colspec colnum="2" colname="col2" colwidth="13mm" /><colspec colnum="3" colname="col3" colwidth="12mm" /><colspec colnum="4" colname="col4" colwidth="12mm" /><colspec colnum="5" colname="col5" colwidth="10mm" /><thead><row><entry align="center" /><entry align="center">a</entry><entry align="center">b</entry><entry align="center">c</entry><entry align="center">d</entry></row></thead><tbody><row><entry align="center" valign="bottom">Ex.5</entry><entry align="center" valign="bottom">0.940</entry><entry align="center" valign="bottom">4.12</entry><entry align="center" valign="bottom">0.71</entry><entry align="center" valign="bottom">6.7</entry></row><row><entry align="center" valign="bottom">Ex.7</entry><entry align="center" valign="bottom">0.950</entry><entry align="center" valign="bottom">4.41</entry><entry align="center" valign="bottom">0.82</entry><entry align="center" valign="bottom">8.8</entry></row><row><entry align="center" valign="bottom">Ex.10</entry><entry align="center" valign="bottom">0.963</entry><entry align="center" valign="bottom">4.28</entry><entry align="center" valign="bottom">0.64</entry><entry align="center" valign="bottom">6.9</entry></row><row><entry align="center" valign="bottom">Ex.11</entry><entry align="center" valign="bottom">1.09</entry><entry align="center" valign="bottom">5.73</entry><entry align="center" valign="bottom">0.68</entry><entry align="center" valign="bottom">9.7</entry></row><row><entry align="center" valign="bottom">Ex.12</entry><entry align="center" valign="bottom">1.30</entry><entry align="center" valign="bottom">5.70</entry><entry align="center" valign="bottom">0.85</entry><entry align="center" valign="bottom">11</entry></row><row><entry align="center" valign="bottom">Ex.13</entry><entry align="center" valign="bottom">1.06</entry><entry align="center" valign="bottom">4.78</entry><entry align="center" valign="bottom">0.71</entry><entry align="center" valign="bottom">7.3</entry></row><row><entry align="center" valign="bottom">Ex.14</entry><entry align="center" valign="bottom">1.03</entry><entry align="center" valign="bottom">4.61</entry><entry align="center" valign="bottom">0.74</entry><entry align="center" valign="bottom">7.4</entry></row></tbody></tgroup></table></tables>

0153The values of absorption coefficient, quantum yield and luminous efficiency of the yellowish green powders of Examples 5-14 are summarized in the following Table 6. <tables id="tabl0006" num="0006"><table frame="all"><title>Table 6</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="14mm" /><colspec colnum="2" colname="col2" colwidth="36mm" /><colspec colnum="3" colname="col3" colwidth="35mm" /><colspec colnum="4" colname="col4" colwidth="33mm" /><colspec colnum="5" colname="col5" colwidth="40mm" /><thead><row><entry align="center" valign="middle" /><entry align="center" valign="middle">Peak wavelength (nm)</entry><entry align="center" valign="middle">Absorption coefficient</entry><entry align="center" valign="middle">Quantum efficiency</entry><entry align="center" valign="middle">Luminescence efficiency</entry></row></thead><tbody><row><entry align="center" valign="bottom">Ex.5</entry><entry align="center" valign="bottom">518</entry><entry align="center" valign="bottom">0.79</entry><entry align="center" valign="bottom">0.58</entry><entry align="center" valign="bottom">0.46</entry></row><row><entry align="center" valign="bottom">Ex.6</entry><entry align="center" valign="bottom">514</entry><entry align="center" valign="bottom">0.84</entry><entry align="center" valign="bottom">0.55</entry><entry align="center" valign="bottom">0.46</entry></row><row><entry align="center" valign="bottom">Ex.7</entry><entry align="center" valign="bottom">517</entry><entry align="center" valign="bottom">0.91</entry><entry align="center" valign="bottom">0.56</entry><entry align="center" valign="bottom">0.51</entry></row><row><entry align="center" valign="bottom">Ex.8</entry><entry align="center" valign="bottom">517</entry><entry align="center" valign="bottom">0.84</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.45</entry></row><row><entry align="center" valign="bottom">Ex.9</entry><entry align="center" valign="bottom">518</entry><entry align="center" valign="bottom">0.81</entry><entry align="center" valign="bottom">0.54</entry><entry align="center" valign="bottom">0.44</entry></row><row><entry align="center" valign="bottom">Ex.10</entry><entry align="center" valign="bottom">520</entry><entry align="center" valign="bottom">0.80</entry><entry align="center" valign="bottom">0.55</entry><entry align="center" valign="bottom">0.44</entry></row><row><entry align="center" valign="bottom">Ex.11</entry><entry align="center" valign="bottom">520</entry><entry align="center" valign="bottom">0.75</entry><entry align="center" valign="bottom">0.54</entry><entry align="center" valign="bottom">0.41</entry></row><row><entry align="center" valign="bottom">Ex.12</entry><entry align="center" valign="bottom">514</entry><entry align="center" valign="bottom">0.64</entry><entry align="center" valign="bottom">0.62</entry><entry align="center" valign="bottom">0.40</entry></row><row><entry align="center" valign="bottom">Ex.13</entry><entry align="center" valign="bottom">511</entry><entry align="center" valign="bottom">0.72</entry><entry align="center" valign="bottom">0.59</entry><entry align="center" valign="bottom">0.43</entry></row><row><entry align="center" valign="bottom">Ex.14</entry><entry align="center" valign="bottom">516</entry><entry align="center" valign="bottom">0.80</entry><entry align="center" valign="bottom">0.59</entry><entry align="center" valign="bottom">0.48</entry></row></tbody></tgroup></table></tables>

0154As shown in Table 6, all of the yellowish green powders of Examples 5-14 were capable of exhibiting an emission wavelength falling within the range of 490 to 580 nm as they were excited by the light having a wavelength ranging from 250 to 500 nm. The absorption coefficient, quantum yield and luminous efficiency of these luminescent materials were by no means inferior to the conventional yellowish green luminescent materials such for example as (Ba,sr)2SiO4:Eu, etc.

0155With respect to the compositions of yellowish green powders of Examples 3, 5, 7, and 10-14, they are already shown in Table 1. The yellowish green powders of other Examples were also chemically analyzed to investigate the values of "a", "b", "c" and "d" in the aforementioned general formula (B).

0156As a result, it was found out that, in the cases of the yellowish green powders of Reference Examples 1-14, the upper limit of the value of "a" was 1.30 and the lower limit thereof was 0.940. With respect to the upper limit and the lower limit of the value of "b", they were 5.73 and 4.12, respectively. With respect to the upper limit and the lower limit of the value of "c", they were 0.85 and 0.63, respectively. Further, with respect to the upper limit and the lower limit of the value of "d", they were 11 and 6.3, respectively.

0157Based on these results, the compositions of yellowish green powders of Examples 1-14 were found definable by the following general formula (2). (M1-xRx)a2AlSib2Oc2Nd2 (2)

0158In the general formula (2), M is at least one kind of metallic element excluding Si and Al; R is a luminescence center element; and x, a2, b2, c2 and d2 satisfy the following relationships: <maths id="math0005"><math display="block"><mn mathvariant="normal">0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">x</mi><mo mathvariant="normal">≤</mo><mn>1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">0.93</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">1.3</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">4.0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">b</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">5.8</mn></math><img file="EP2003183B1_D0005.tif" /></maths><maths id="math0006"><math display="block"><mn mathvariant="normal">0.6</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">c</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mi>and</mi><mspace width="1em" /><mn mathvariant="normal">6</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">d</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">11.</mn></math><img file="EP2003183B1_D0006.tif" /></maths>

0159The yellowish green luminescent materials of Examples 5-8 and 14 were found capable of exhibiting a luminous efficiency of 45% or more, thus indicating excellent luminous efficiency. The compositions of yellowish green powders of Examples 1-14 which were especially excellent in luminous efficiency can be defined by the general formula (2) wherein a2, b2, c2 and d2 satisfy the following relationships: <maths id="math0007"><math display="block"><mn mathvariant="normal">0.94</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">1.1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">4.1</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">b</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">4.7</mn></math><img file="EP2003183B1_D0007.tif" /></maths><maths id="math0008"><math display="block"><mn mathvariant="normal">0.7</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">c</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">0.85</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">7</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">d</mi><mo>⁢</mo><mn mathvariant="normal">2</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">9.</mn></math><img file="EP2003183B1_D0008.tif" /></maths>

0160When all of the yellowish green powders of Examples 1-14 were subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), they exhibited concurrently diffraction peaks at least at diffraction angles (2θ) of 11.81-11.85, 15.34-15.38, 20.40-20.47 and 23.74-23.86°.

(Reference Example 31)

0161SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 29.378, 16.395, 28.062 and 0.176g, respectively. Then, these starting materials were mixed together with dehydrated isopropanol (IPA) for 24 hours in a ball mill. After IPA was volatilized and removed by room temperature drying, the mixture was allowed to dry overnight in air atmosphere and at a temperature of 120°C. The resultant mixture was ground in a mortar and then charged in a carbon crucible. Finally, the mixture in the crucible was subjected to sintering in a nitrogen atmosphere of 7.5 atm. for 60 hours at a temperature of 1800°C to synthesize a luminescent material, wherein this sintering was repeated twice under the same conditions.

0162This luminescent material thus sintered was formed of a mixture of sintered powders differing in body color, i.e., a white sintered powder, a minute amount of orange sintered powder and a minute amount of red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, an orange emission from the minute amount of orange sintered powder and a red emission from the minute amount of red powder were observed.

0163This red powder was dispensed and subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å). As a result, it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 13.10, 18.62, 20.22, 26.40 and 26.04°.

0164When this red powder was subjected to chemical analysis, it was possible to confirm a composition represented by (M0.991R0.009)2.23AlSi4.75O0.80N7.88. The red powder of this reference example can be defined, by the values of a, b, c and d in the aforementioned general formula (B), such that the value of (1+b)/a is 2.58 and the value of (c+d)/a is 3.93.

(Reference Example 32)

0165A luminescent material was synthesized in this example under the same conditions as described in Reference Example 31 except that the loading of SrCO3 was changed to 29.231g and the loading of Eu2O3 was changed to 0.352g.

0166This luminescent material thus sintered was formed of a mixture of sintered powders differing in body color, i.e., a white sintered powder, a minute amount of orange sintered powder and a minute amount of red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, an orange emission from the minute amount of orange sintered powder and a red emission from the minute amount of red powder were observed.

(Reference Example 33)

0167A luminescent material was synthesized in this example under the same conditions as described in Reference Example 31 except that the loading of SrCO3 was changed to 28.935g and the loading of Eu2O3 was changed to 0.704g.

0168This luminescent material thus sintered was formed of a mixture of sintered powders differing in body color, i.e., a white sintered powder, a minute amount of orange sintered powder and a minute amount of red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, an orange emission from the minute amount of orange sintered powder and a red emission from the minute amount of red powder were observed.

0169This red powder was dispensed and subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å). As a result, it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 13.08, 18.62, 20.18, 26.38 and 28.02°.

(Reference Example 34)

0170A luminescent material was synthesized in this example under the same conditions as described in Reference Example 31 except that the loading of SrCO3 was changed to 28.640g and the loading of Eu2O3 was changed to 1.056g.

0171This luminescent material thus sintered was formed of a mixture of sintered powders differing in body color, i.e., a white sintered powder, a minute amount of orange sintered powder and a minute amount of red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, an orange emission from the minute amount of orange sintered powder and a red emission from the minute amount of red powder were observed.

0172This red powder was dispensed and subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å). As a result, it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 13.10, 18.60, 20.20, 26.38 and 28.03°.

0173The red powders of Reference Examples 31-34 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0009">FIG. 18</figref>. In <figref idref="f0009">FIG. 18</figref>, the band exhibiting a peak at 457 nm was derived from the reflection of exciting beam. A single-band emission exhibiting a peak at a wavelength ranging from 620 to 640 nm was obtained from all of these red powders.

(Reference Example 35)

0174The same kind of raw material as that of Reference Example 31 was placed in a carbon crucible. Thereafter, the raw material was sintered for 60 hours at a temperature of 1800°C in a nitrogen atmosphere of 7.5 atm., thereby synthesizing the luminescent material of this reference example.

0175This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, and a red emission from the red powder were observed.

0176This red powder was then subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å). As a result, it exhibited concurrently diffraction peaks at diffraction angles (2θ) of 13.12, 18.64, 20.22, 26.40 and 28.04°.

(Reference Example 36)

0177The same kind of raw material as that of Reference Example 32 was placed in a carbon crucible. Thereafter, the raw material was sintered for 60 hours at a temperature of 1800°C in a nitrogen atmosphere of 7.5 atm., thereby synthesizing the luminescent material of this reference example.

0178This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, and a red emission from the red powder were observed.

(Reference Example 37)

0179The same kind of raw material as that of Reference Example 33 was placed in a carbon crucible. Thereafter, the raw material was sintered for 60 hours at a temperature of 1800°C in a nitrogen atmosphere of 7.5 atm., thereby synthesizing the luminescent material of this reference example.

0180This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, and a red emission from the red powder were observed.

(Reference Example 38)

0181The same kind of raw material as that of Reference Example 34 was placed in a carbon crucible. Thereafter, the raw material was sintered for 60 hours at a temperature of 1800°C in a nitrogen atmosphere of 7.5 atm., thereby synthesizing the luminescent material of this reference example.

0182This luminescent material thus sintered was formed of a mixture of two kinds of sintered powder differing in body color, thus confirming existence of a white sintered powder and a red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, and a red emission from the red powder were observed.

0183The red powders of Reference Examples 35-38 were respectively taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powders were respectively excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrums thus obtained are shown in <figref idref="f0010">FIG. 19</figref>. In <figref idref="f0010">FIG. 19</figref>, the band exhibiting a peak at 457 nm was derived from the reflection of exciting beam. A single-band emission exhibiting a peak at a wavelength ranging from 610 to 640 nm was obtained from all of these red powders.

(Reference Example 39)

0184SrCO3, AlN, Si3N4 and Eu2O3 were prepared as starting materials, and these starting materials were weighed to obtain 2.923, 1.640, 2.806 and 0.035g, respectively. Then, these starting materials were mixed together in a mortar for 20 minutes and then placed in a carbon crucible. The mixture in the crucible was then subjected to sintering in a nitrogen atmosphere of 7.5 atm. for four hours at a temperature of 1800°C, thereby synthesizing a luminescent material of this reference example.

0185This luminescent material thus sintered was formed of a mixture of sintered powders differing in body color, i.e., a white sintered powder, a minute amount of orange sintered powder and a minute amount of red sintered powder. When this luminescent material was excited by black light, a blue emission from the white powder, an orange emission from the minute amount of orange sintered powder and a red emission from the minute amount of red powder were observed.

0186The red powder of Reference Example 39 was taken out of the crucible and ground in a mortar in the same manner as described above. Then, the red powder was excited by an emission diode exhibiting a peak wavelength of 457 nm. The emission spectrum thus obtained is shown in <figref idref="f0010">FIG. 20</figref>. In <figref idref="f0010">FIG. 20</figref>, the band exhibiting a peak at 457 nm was derived from the reflection of exciting beam. A single-band emission exhibiting a peak at a wavelength ranging from 610 to 640 nm was obtained from the red powder.

0187The values of absorption coefficient, quantum yield and luminous efficiency of the yellowish green powders of Reference Examples 31-39 are summarized in the following Table 7. <tables id="tabl0007" num="0007"><table frame="all"><title>Table 7</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="20mm" /><colspec colnum="2" colname="col2" colwidth="36mm" /><colspec colnum="3" colname="col3" colwidth="35mm" /><colspec colnum="4" colname="col4" colwidth="33mm" /><colspec colnum="5" colname="col5" colwidth="40mm" /><thead><row><entry align="center" valign="middle" /><entry align="center" valign="middle">Peak wavelength (nm)</entry><entry align="center" valign="middle">Absorption coefficient</entry><entry align="center" valign="middle">Quantum efficiency</entry><entry align="center" valign="middle">Luminescence efficiency</entry></row></thead><tbody><row><entry align="center" valign="bottom">Ref. Ex.31</entry><entry align="center" valign="bottom">621</entry><entry align="center" valign="bottom">0.63</entry><entry align="center" valign="bottom">0.52</entry><entry align="center" valign="bottom">0.33</entry></row><row><entry align="center" valign="bottom">Ref. Ex.32</entry><entry align="center" valign="bottom">625</entry><entry align="center" valign="bottom">0.77</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.41</entry></row><row><entry align="center" valign="bottom">Ref. Ex.33</entry><entry align="center" valign="bottom">626</entry><entry align="center" valign="bottom">0.79</entry><entry align="center" valign="bottom">0.53</entry><entry align="center" valign="bottom">0.42</entry></row><row><entry align="center" valign="bottom">Ref. Ex.34</entry><entry align="center" valign="bottom">646</entry><entry align="center" valign="bottom">0.83</entry><entry align="center" valign="bottom">0.49</entry><entry align="center" valign="bottom">0.41</entry></row><row><entry align="center" valign="bottom">Ref. Ex.35</entry><entry align="center" valign="bottom">616</entry><entry align="center" valign="bottom">0.62</entry><entry align="center" valign="bottom">0.40</entry><entry align="center" valign="bottom">0.25</entry></row><row><entry align="center" valign="bottom">Ref. Ex.36</entry><entry align="center" valign="bottom">623</entry><entry align="center" valign="bottom">0.64</entry><entry align="center" valign="bottom">0.42</entry><entry align="center" valign="bottom">0.27</entry></row><row><entry align="center" valign="bottom">Ref. Ex.37</entry><entry align="center" valign="bottom">624</entry><entry align="center" valign="bottom">0.69</entry><entry align="center" valign="bottom">0.44</entry><entry align="center" valign="bottom">0.30</entry></row><row><entry align="center" valign="bottom">Ref. Ex.38</entry><entry align="center" valign="bottom">637</entry><entry align="center" valign="bottom">0.74</entry><entry align="center" valign="bottom">0.47</entry><entry align="center" valign="bottom">0.35</entry></row><row><entry align="center" valign="bottom">Ref. Ex.39</entry><entry align="center" valign="bottom">633</entry><entry align="center" valign="bottom">0.75</entry><entry align="center" valign="bottom">0.46</entry><entry align="center" valign="bottom">0.35</entry></row></tbody></tgroup></table></tables>

0188As shown in Table 7, all of the yellowish green powders of Reference Examples 31-39 were capable of exhibiting an emission wavelength falling within the range of 580 to 700 nm as they were excited by the light having a wavelength ranging from 250 to 500 nm. The absorption coefficient, quantum yield and luminous efficiency of these luminescent materials were by no means inferior to the conventional yellowish green luminescent materials such for example as Sr2Si5N8:Eu, etc.

0189Even if the exciting wavelength was changed to 254, 365, 390 or 460 nm, it was possible to confirm the emission having a peak in almost the same wavelength range as described above. Because of the facts that if the exciting wavelength is too short, the loss due to Stokes shift would become prominent and that if the exciting wavelength is too long, the excitation efficiency would be deteriorated, the exciting wavelength should preferably be confined within the range of 380 to 460 nm. Further, the peak wavelength of emission should desirably be confined to 670 nm or less.

0190With respect to the composition of red powder of Reference Example 31, it is already explained above. The red powders of other Reference Examples were also chemically analyzed to investigate the values of "a", "b", "c" and "d" in the aforementioned composition formula (B). As a result, it was found out that, in the cases of the red powders of Reference Examples 31-39, the lower limit and the upper limit of the value of (1+b)/a was 2.41 and 2.58, respectively. Further, the lower limit and the upper limit of the value of (c+d)/a was 3.48 and 4.17, respectively.

0191Based on these results, the compositions of yellowish green powders of Reference Examples 31-39 were found definable by the following general formula (3). (M1-XRx)a3AlSib3Oc3Nd3 (3)

0192In the general formula (3), M is at least one metallic element excluding Si and Al; R is a luminescence center element; and x, a3, b3, c3 and d3 satisfy the following relationships: <maths id="math0009"><math display="block"><mn mathvariant="normal">0</mn><mo mathvariant="normal"><</mo><mi mathvariant="normal">x</mi><mo mathvariant="normal">≤</mo><mn mathvariant="normal">1</mn><mo mathvariant="normal">,</mo><mspace width="1em" /><mn mathvariant="normal">2.4</mn><mo mathvariant="normal"><</mo><mfenced><mn mathvariant="normal">1</mn><mo mathvariant="normal">+</mo><mi mathvariant="normal">b</mi><mo>⁢</mo><mn mathvariant="normal">3</mn></mfenced><mo mathvariant="normal">/</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">2.6</mn></math><img file="EP2003183B1_D0009.tif" /></maths><maths id="math0010"><math display="block"><mn mathvariant="normal">3.4</mn><mo mathvariant="normal"><</mo><mfenced><mi mathvariant="normal">c</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo mathvariant="normal">+</mo><mi mathvariant="normal">d</mi><mo>⁢</mo><mn mathvariant="normal">3</mn></mfenced><mo mathvariant="normal">/</mo><mi mathvariant="normal">a</mi><mo>⁢</mo><mn mathvariant="normal">3</mn><mo mathvariant="normal"><</mo><mn mathvariant="normal">4.2.</mn></math><img file="EP2003183B1_D0010.tif" /></maths>

0193When all of the compositions of red powders of Reference Examples 31-39 were subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), they exhibited concurrently diffraction peaks at least at diffraction angles (2θ) of 13.06-13.16, 18.58-18.68, 20.14-20.24, 26.32-26.46 and 27.98-28.10°.

(Comparative Example 1)

019426.573g of SrCO3, 23.385g of Si3N4 and 3.519g of Eu2O3 were prepared as starting materials, and these starting materials were mixed together in a ball mill. The resultant mixture was placed in a carbon crucible and then subjected to sintering in a nitrogen atmosphere of 7 atm. for 8 hours at a temperature of 1650°C to synthesize a luminescent material of this comparative example.

0195As a result of chemical analysis, the luminescent material of this comparative example was confirmed as having a composition represented by (Sr0.9Eu0.1)2Si5N8. The luminescent material thus obtained was a vermilion sintered body and when it was excited by black light, a red emission was observed.

(Comparative Example 2)

0196148g of SrCO3 and 0.176g of Eu2O3 were prepared as starting materials, and these starting materials were mixed together in a mortar. The resultant mixed powder was placed in a quartz crucible and then subjected to sintering in a H2S atmosphere of 1 atm. for one hour at a temperature of 1100°C. The sintered mixture was further powdered and blended with 2g of NH4Cl. The resultant mixture was further mixed in a mortar and sealed in a quartz tube. Thereafter, the mixture was sintered for one hour at a temperature of 1100°C in a nitrogen atmosphere of 1 atm., thereby synthesizing the luminescent material of this comparative example.

0197As a result of chemical analysis, the luminescent material of this comparative example was confirmed as having a composition represented by (Sr0.999Eu0.001)2S· The luminescent material thus obtained was a pink sintered body and when it was excited by black light, a red emission exhibiting a peak wavelength of 620 nm was observed.

(Comparative Example 3)

019817.066g of SrCO3, 8.198g of AlN, 23.759g of Si3N4 and 3.590g of Eu2O3 were prepared as starting materials. These starting materials were mixed, dried and ground in the same manner as Example 1. After being placed in a carbon crucible, the resultant mixture was sintered using a hot press for two hours at a press pressure of 350 MPa and a temperature of 1800°C in a nitrogen atmosphere of 3.5 atm. The sample thus sintered was formed of a sintered body having a gray-yellowish green body color and when it was excited by black light, a weak yellowish green emission was observed.

(Comparative Example 4)

0199A luminescent material was synthesized in this comparative example in the same manner as in Comparative Example 3 except that 17.693g of SrCO3, 6.148g of AlN, 29.114g of Si3N4 and 3.722g of Eu2O3 were employed as starting materials. The sample thus sintered was formed of a sintered body having a gray-yellowish green body color and when it was excited by black light, a weak yellowish green emission was observed.

(Comparative Example 5)

0200A raw material that had been weighed and mixed in the same manner as in Reference Example 1 was placed in a carbon crucible and sintered in the same manner as in Comparative Example 3, thereby synthesizing a luminescent material of this comparative example. The sample thus sintered was formed of a sintered body having a gray-yellowish green body color and when it was excited by black light, a weak yellowish green emission was observed.

(Comparative Example 6)

020194.27g of SrCO3 powder, 7.12g of BaCO3 powder, 22.835g of SiO2 powder and 4.460g of Eu2O3 powder were prepared as starting materials. To these starting materials, 1.8g of NH4Cl was added as a crystal growth-promoting agent. Then, these starting materials were mixed together in a ball mill.

0202The mixed raw materials thus obtained were charged into a sintering vessel and sintered under the following sintering conditions. First of all, the mixed raw materials were sintered for 3-7 hours in a reducing atmosphere of nitrogen/hydrogen at a temperature ranging from 1000 to 1600°C to prepare an Sr1.9Ba0.1SiO4:Eu luminescent material of this comparative example. The luminescent material thus sintered was formed of a sintered body having a yellow body color and when it was excited by black light, a yellow emission was observed.

0203The luminescent materials of Comparative Examples 3-5 were respectively chemically analyzed, the results being summarized in the following Table 8. In this Table 6, there are shown the values of "a", "b", "c" and "d" in the aforementioned general formula (B). <tables id="tabl0008" num="0008"><table frame="all"><title>Table 8</title><tgroup cols="5"><colspec colnum="1" colname="col1" colwidth="22mm" /><colspec colnum="2" colname="col2" colwidth="12mm" /><colspec colnum="3" colname="col3" colwidth="12mm" /><colspec colnum="4" colname="col4" colwidth="12mm" /><colspec colnum="5" colname="col5" colwidth="12mm" /><thead><row><entry align="center" /><entry align="center">a</entry><entry align="center">b</entry><entry align="center">c</entry><entry align="center">d</entry></row></thead><tbody><row><entry align="center" valign="bottom">Comp. Ex.3</entry><entry align="center" valign="bottom">0.68</entry><entry align="center" valign="bottom">2.59</entry><entry align="center" valign="bottom">1.12</entry><entry align="center" valign="bottom">3.78</entry></row><row><entry align="center" valign="bottom">Comp. Ex.4</entry><entry align="center" valign="bottom">0.95</entry><entry align="center" valign="bottom">4.25</entry><entry align="center" valign="bottom">1.68</entry><entry align="center" valign="bottom">5.59</entry></row><row><entry align="center" valign="bottom">Comp. Ex.5</entry><entry align="center" valign="bottom">0.99</entry><entry align="center" valign="bottom">5.03</entry><entry align="center" valign="bottom">1.75</entry><entry align="center" valign="bottom">6.48</entry></row></tbody></tgroup></table></tables>

0204Although the luminescent materials of Comparative Examples 3-5 all comprise, as a matrix, a sialon-based compound, they fail to meet any of the conditions defined by the general formulas (1), (2) and (3). Therefore, it will be seen that these luminescent materials were all falling outside the scope of composition of luminescent material as defined by the embodiment of the present invention. It should be noted that the luminescent materials of Comparative Examples 1, 2 and 6 were all different from those comprising a sialon-based compound as a matrix.

0205The luminescent materials of Comparative Examples 3-5 were subjected to X-ray diffraction measurement employing CuKα characteristic X-rays (wavelength: 1.54056Å), the results being illustrated in <figref idref="f0011">FIG. 21</figref>. In this <figref idref="f0011">FIG. 21</figref>, the results of X-ray diffraction measurement performed on the luminescent materials of Reference Example 20 and of Example 2 are also illustrated. As shown in <figref idref="f0011">FIG. 21</figref>, since the compositions of the luminescent materials of Comparative Examples 3-5 were not confined within the aforementioned prescribed range, the luminescent materials of Comparative Examples 3-5 exhibited XRD profiles which were different from that of Reference Example 20 or of Example 2. For this reason, the luminescent materials of Comparative Examples 3-5 were supposed that they were respectively formed of a different structure from that of the luminescent material of Example 2. The structure of each of the luminescent materials of Comparative Examples 3-5 was almost identical with the pattern of S phase (JCPDS card #53-0636) shown in <figref idref="f0011">FIG. 21</figref>.

0206The luminescent materials of Comparative Examples 3-5 were respectively excited by an emission diode exhibiting a peak wavelength of 390 nm. The emission spectrums thus obtained are shown in <figref idref="f0011">FIG. 22. FIG. 22</figref> also shows the results obtained from the red powder of Reference Example 20 and from the yellowish green powder of Example 2. In <figref idref="f0011">FIG. 22</figref>, the bands each exhibiting a peak at 390 nm were derived from the reflection of exciting beam. The luminescent materials of Comparative Examples 3-5 were all very low in emission intensity.

0207As seen from the results described above, any kinds of luminescent material whose compositions fall outside the composition range of luminescent material as defined by this embodiment would have a different structure from those of the luminescent materials of this embodiment, thus failing to obtain desired emission characteristics.

0208The red powders of Reference Examples 20 and 39 were excited while increasing the temperature of these samples from room temperature to 200°C by a heater to measure any changes in emission spectrum. In this excitation, an emission diode exhibiting a peak wavelength of 458 nm was employed. <figref idref="f0012">FIG. 23</figref> shows the temperature dependency of the peak emission intensity in emission spectrum at each temperature.

0209For the purpose of comparison, the temperature dependency of the peak emission intensity of Sr2Si5N8:Eu luminescent material of Comparative Example 1 and the temperature dependency of CaS:Eu luminescent material of Comparative Example 2 are also shown in <figref idref="f0012">FIG. 23</figref>. The y-axis in <figref idref="f0012">FIG. 23</figref> represents values which were normalized on the basis of emission intensity of each of luminescent materials at room temperature, the value of which being set to one.

0210The graph of <figref idref="f0012">FIG. 23</figref> indicates that, in the cases of luminescent materials of Reference Examples 20 and 39, even under high temperature conditions of as high as 200°C, the deterioration of emission intensity thereof was minimal. It will be recognized from these results that the luminescent material according to this embodiment was excellent in temperature characteristics as compared with CaS:Eu luminescent material and also with Sr2Si5N8:Eu luminescent material which was constituted by the same nitride matrix as that of the luminescent material of this embodiment. In the graph of <figref idref="f0012">FIG. 23</figref>, only the results obtained from the luminescent materials of Reference Examples 20 and 39 are shown. However, even in the cases of luminescent materials of other examples, it was also possible to obtain more excellent temperature characteristics than those of comparative examples.

0211In the same manner as described above, the red powders of Comparative Examples 3 to 5 were also excited while increasing the temperature of these samples to measure any changes in emission spectrum. As a result, under high temperature conditions of as high as 200°C, all of these luminescent materials were deteriorated in emission intensity, thus indicating almost the same tendency as that of Comparative Example 1 or Comparative Example 2.

0212Further, the yellowish green powder of Example 1 was excited while increasing the temperature of this sample from room temperature to 200°C by a heater to measure any changes in emission spectrum. In this excitation, an emission diode exhibiting a peak wavelength of 458 nm was employed. <figref idref="f0012">FIG. 24</figref> shows the temperature dependency of the peak emission intensity in emission spectrum at each temperature.

0213For the purpose of comparison, the temperature dependency of the peak emission intensity of Sr1.9Ba0.1SiO4:Eu luminescent material of Comparative Example 6 is also shown in <figref idref="f0012">FIG. 24</figref>. The y-axis in <figref idref="f0012">FIG. 24</figref> represents values which were normalized on the basis of emission intensity of each of luminescent materials at room temperature, the value of which being set to one.

0214The graph of <figref idref="f0012">FIG. 24</figref> indicates that the luminescent material of Example 1 was minimal in deterioration of emission intensity even under high temperature condition of as high as 200°C. It will be recognized from the result thus obtained that the luminescent material of this embodiment was excellent in temperature characteristics as compared with Sr1.9Ba0.1SiO4:Eu luminescent material.

0215Further, using the luminescent material of Example 1, a light-emitting device was manufactured as shown in <figref idref="f0001">FIG. 2</figref>. When the light-emitting device thus obtained was actuated at a temperature ranging from room temperature to 150°C to measure the changes in emission efficiency with temperature, almost no deterioration in emission efficiency was caused to occur within this range of temperature. From this fact, it was confirmed that the light-emitting device according to this embodiment was provided with excellent temperature characteristics.

0216When the luminescent material of Comparative Example 3 was employed to manufacture a light-emitting device which was similar in structure as described above and the light-emitting device was tested in the same manner as described above. As a result, the emission efficiency thereof was prominently deteriorated in the aforementioned range of temperature. Even when the luminescent materials of Comparative Examples 4 and 5 were employed, almost the same result as that of the luminescent material of Comparative Example 3 was obtained. It was confirmed that even in the case of sialon-based compounds comprising an emission center element, it was impossible to secure excellent temperature characteristics unless the composition thereof was not confined to fall within the aforementioned prescribed range.

0217According to the present invention, it is possible to provide a luminescent material excellent in temperature characteristics and a light-emitting device wherein this luminescent material is employed.

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US2009096361A1	United States of America	A1	2009-04-16
JPWO2007105631A1	Japan	A1	2009-07-30
EP2003183A4	European Patent Office (EPO)	A4	2010-12-01
US2011057149A1	United States of America	A1	2011-03-10
US2011058582A1	United States of America	A1	2011-03-10
US2011058583A1	United States of America	A1	2011-03-10
EP2308946A2	European Patent Office (EPO)	A2	2011-04-13
JP2011080068A	Japan	A	2011-04-21
JP2011082529A	Japan	A	2011-04-21
JP2011084741A	Japan	A	2011-04-28
JP2011116994A	Japan	A	2011-06-16
JP4719309B2	Japan	B2	2011-07-06
EP2308946A3	European Patent Office (EPO)	A3	2011-08-31
JP4762248B2	Japan	B2	2011-08-31
JP2011246733A	Japan	A	2011-12-08
JP2012001731A	Japan	A	2012-01-05
JP2012070014A	Japan	A	2012-04-05
JP2012109592A	Japan	A	2012-06-07
EP2003183B1This record	European Patent Office (EPO)	B1	2012-08-29
JP5058365B2	Japan	B2	2012-10-24
EP2518129A2	European Patent Office (EPO)	A2	2012-10-31
EP2518129A3	European Patent Office (EPO)	A3	2013-04-03
US8450923B2	United States of America	B2	2013-05-28
US8475680B2	United States of America	B2	2013-07-02
US8482192B2	United States of America	B2	2013-07-09
US8491817B2	United States of America	B2	2013-07-23
EP2308946B1	European Patent Office (EPO)	B1	2013-07-24
JP5319645B2	Japan	B2	2013-10-16
JP5323216B2	Japan	B2	2013-10-23
JP5337130B2	Japan	B2	2013-11-06
JP5454965B2	Japan	B2	2014-03-26
EP2518129B1	European Patent Office (EPO)	B1	2014-04-23
JP5586499B2	Japan	B2	2014-09-10
JP5696013B2	Japan	B2	2015-04-08

28 legal events, as 4 offices reported them to INPADOC

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Events

Legal events, newest first
	Event	Code	Office
2026-04-09	Annual fee paid to national office [announced via postgrant information from national office to epo]GrantedPGFP	PGFP	EP
2026-01-15	Annual fee paid to national office [announced via postgrant information from national office to epo]GrantedPGFP	PGFP	EP
2025-04-28	Annual fee paid to national office [announced via postgrant information from national office to epo]GrantedPGFP	PGFP	EP
2025-04-11	Annual fee paid to national office [announced via postgrant information from national office to epo]GrantedPGFP	PGFP	EP
2018-02-23	Fee paymentPLFP	PLFP	FR
2017-02-13	Fee paymentPLFP	PLFP	FR
2016-02-08	Fee paymentPLFP	PLFP	FR
2013-09-26	No opposition filed against granted patent, or epo opposition proceedings concluded without decisionGrantedR097	R097	DE
2013-08-07	No opposition filedOpposition26N	26N	EP
2013-07-05	No opposition filed within time limitOppositionORIGINAL CODE: 0009261PLBE	PLBE	EP
2013-07-05	Information on the status of an ep patent application or granted ep patentGrantedSTATUS: NO OPPOSITION FILED WITHIN TIME LIMITSTAA	STAA	EP
2012-10-18	Dpma publication of mentioned ep patent grantGrantedR096	R096	DE
2012-08-29	Designated contracting statesAK	AK	EP
2012-08-29	European patent grantedGrantedFG4D	FG4D	GB
2012-08-08	Request for extension of the european patent (deleted)DAX	DAX	EP
2012-07-27	(expected) grantORIGINAL CODE: 0009210GRAA	GRAA	EP
2012-07-25	Grant fee paidORIGINAL CODE: EPIDOSNIGR3GRAS	GRAS	EP
2012-03-16	Despatch of communication of intention to grant a patentORIGINAL CODE: EPIDOSNIGR1GRAP	GRAP	EP
2012-03-14	Information provided on ipc code assigned before grantRIC1	RIC1	EP
2012-03-14	Information provided on ipc code assigned before grantRIC1	RIC1	EP
2012-02-07	Amendment of ipc main classPREVIOUS MAIN CLASS: C09K0011640000R079	R079	DE
2011-09-14	First examination report despatched17Q	17Q	EP
2010-12-01	Supplementary search report drawn up and despatchedA4	A4	EP
2010-05-05	Party data changed (applicant data changed or rights of an application transferred)RAP1	RAP1	EP
2009-04-15	Designated contracting states (corrected)RBV	RBV	EP
2008-12-17	Request for examination filed17P	17P	EP
2008-12-17	Designated contracting statesAK	AK	EP
2008-11-14	Public reference made under article 153(3) epc to a published international application that has entered the european phaseORIGINAL CODE: 0009012PUAI	PUAI	EP