Wavelength converted semiconductor light emitting devices

The present invention relates to a wavelength conversion type semiconductor light emitting device.

Semiconductor light emitting devices, including light emitting diodes (LEDs), are one of the most efficient light sources currently available. Manufacturers of high-brightness light-emitting devices capable of operating over the entire visible spectrum are currently paying attention to the material systems of gallium, aluminum, indium, and nitrogen binary alloys, ternary alloys, and especially group III nitride materials. Group III-V semiconductors such as quaternary alloys can be mentioned. Typically, Group III nitride light emitting devices stack semiconductor layers of different compositions and additive concentrations by metalorganic vapor phase growth (MOCVD), molecular beam epitaxy (MBE), or other epitaxial techniques. , Sapphire, silicon carbide, group III nitride, or other suitable substrate. Sapphire is widely available on the market and is relatively easy to handle, so it is often used as a growth substrate. A stack grown on a growth substrate typically comprises one or more n-type layers formed on the substrate, for example Si added, and the n-type layer or multiple n-type layers. It includes a light emitting region or active region to be formed and one or more p-type layers formed on the active region to which, for example, Mg has been added. The Group III nitride light emitting device efficiently emits UV through green light.

<p> Lighting systems that convert the color of light emitted by a light emitting diode using a fluorescent material such as a phosphor have been proposed. A two-color lighting system that mixes the primary emission light of a blue LED with the light emitted by a yellow phosphor is described in US Pat. No. 5,998,925. Y₃Al₅O₁₂: Ce³⁺A phosphor covers the Group III nitride LED, and a part of the blue light emitted from the LED is converted into yellow light by the phosphor. The rest of the blue light from the LED is transmitted through the phosphor. Thus, the system emits both the blue light emitted by the LED and the yellow light emitted by the phosphor. The mixed light in the blue and yellow emission bands has a CRI between about 75 and about 80 and a color temperature T in the range of about 6000K to about 8000K._CIt is recognized by what you see as white light with and.</p><p> However, white LEDs based on the two-color approach can only be used in a limited range of general-purpose lighting due to the poor color rendering due to the absence of the red component. A lighting system that compensates for the lack of red color is shown in Figure 1 and described in detail by US Pat. No. 6,351,069. The LED 34 in Figure 1 is designed to produce a color-balanced white light output to provide illumination that provides good color rendering. The LED 34 includes a gallium nitride (GaN) die 12 positioned on the reflector cup-shaped lead frame 14 and electrically connected to the leads 16 and 18. Leads 16 and 18 supply excitation power to the GaN die 12. The GaN die 12 can generally have a square shape. In a preferred embodiment, the GaN die 12 is made to emit primary light, i.e. blue light, having a peak wavelength of 470 nm within the blue region of the optical spectrum. The GaN die 12 is covered with a spacer layer 36 made of a transparent material. The transparent material can be transparent epoxy or glass.</p><p> Adjacent to the spacer layer 36 is the fluorescent layer 38. The fluorescent layer 38 contains the fluorescent substance 22 and the second fluorescent substance 40. The fluorescent substance 22 has the property of absorbing the primary light and emitting the secondary light having the first peak wavelength, while the fluorescent substance 40 absorbs the primary light and has the second peak wavelength. It has the property of emitting secondary light. The secondary light emitted by the fluorescent substance 22 preferably has a high band spectral distribution centered in the yellow region of the visible spectrum. However, the secondary light emitted by the fluorescent substance 40 has a strong spectral distribution in the red region of the visible spectrum. Therefore, when the primary light and the secondary light emitted by the fluorescent substances 22 and 40 are mixed, white light containing a large amount of red color is generated in addition to other colors. The peak wavelength of the secondary light is determined by the composition of the fluorescent substances 22 and 40 in addition to the peak wavelength of the primary light.</p><p> The layer 38 containing the two fluorescent substances is a phosphor-resin mixture "containing the two fluorescent substances bonded using a resin paste". The phosphor-resin mixture "deposits on the encapsulating layer to form a fluorescent layer that evenly covers the encapsulating layer. The deposited phosphor-resin mixture is then gelled, i.e. partially cured. I can let you. " Thus, in the system that compensates for the red deficiency of US Pat. No. 6,351,069, the two fluorescent materials are mixed and then dispersed in the resin layer.</p>

<p> According to the embodiment of the present invention, the wavelength conversion type semiconductor light emitting device includes a first wavelength conversion substance and a second wavelength conversion substance. The first wavelength-converting material emits light having a shorter wavelength than the light emitted by the second wavelength-converting material. In some embodiments, the first and second wavelength converters maximize one or more of the equivalent brightness, color rendering index, and color gamut of the mixed visible light emitted by the device. Arranged to do. In some embodiments, the first and second wavelength converters are deposited adjacent to each other on the light emitting device. In some embodiments, the first and second wavelength converters are deposited as separate layers.</p>

According to an embodiment of the present invention, a system including a multi-wavelength conversion material such as a phosphor combined with a semiconductor light emitting device is disclosed. In the following description, "mixed" or "synthetic" light refers to the combination of light emitted by a semiconductor light emitting device and light emitted by all phosphors in the system.

In some embodiments, a blue light emitting diode is combined with a yellow or green light emitting phosphor and a red light emitting phosphor. As an example of a suitable yellow or green luminescent phosphor, for example Lu₃Al₅O₁₂: Ce³⁺And Y₃Al₅O₁₂: Ce³⁺Including (Lu_1-xyabY_xGd_y)₃(Al_1-zGa_z)₅O₁₂: Ce_a³⁺Pr_b³⁺(Here, 0 &lt;x &lt;1, 0 &lt;y &lt;1, 0 &lt;z 0.1, 0 &lt;a 0.2, 0 &lt;b 0.1), for example, SrSi.₂N₂O₂:EU²⁺Including (Sr_1-abCa_bBa_c) Si_xN_yO_z:EU_a²⁺(Here, a = 0.002 ~ 0.2, b = 0.0 ~ 0.25, c = 0.0 ~ 0.25, x = 1.5 ~ 2.5, y = 1.5 ~ 2.5, z = 1.5 ~ 2.5), for example, SrGa₂S₄:EU²⁺Including (Sr_1-uvxMg_uCa_vBa_x) (Ga_2-yzAl_yIn_zS₄):EU²⁺And Sr_1-xBa_xSiO₄:EU²⁺And can be mentioned. As an example of a suitable red-emitting phosphor, for example CaS: Eu²⁺And SrS: Eu²⁺Including (Ca_1-xSr_x) S: Eu²⁺(Here, 0 &lt;x 1), for example, Sr₂Si₅N₈:EU²⁺Including (Sr_1-xyBa_xCa_y)_2-zSi_5-aAl_aN_8-aO_a:EU_z²⁺(Here, 0 a &lt;5, 0 &lt;x 1, 0 y 1, 0 &lt;z 1).

In some embodiments, UV light emitting diodes are combined with blue light emitting phosphors, yellow or green light emitting phosphors, and red light emitting phosphors. Examples of suitable yellow or green luminescent phosphors, and suitable red luminescent phosphors are described above. As an example of a suitable blue fluorescent emitter, for example MgSrSiO₄Can be mentioned. The embodiments described below refer to a blue LED in combination with two phosphors and an ultraviolet LED in combination with three phosphors, but with more or less phosphors and others. It is understood that an LED that emits light can be used.

Some excitation and emission spectra of the above phosphors are shown in FIG. In FIG. 2, the spectrum a is Sr.₂Si₅N₈:EU²⁺Excitation spectrum of, spectrum b is Sr₂Si₅N₈:EU²⁺Is the emission spectrum of, and the spectrum c is MgSrSiO.₄Is the emission spectrum of, and the spectrum d is Sr._1-xBa_xSiO₄:EU²⁺Is the emission spectrum of, and the spectrum e is SrGa.₂S₄:EU²⁺Is the emission spectrum of, and the spectrum f is SrSi.₂N₂O₂:EU²⁺Is the emission spectrum of.

The present inventors have discovered that when several fluorophores are mixed, the interaction between the mixed fluorophores may adversely affect the efficiency and spectrum of the device. Therefore, the performance of the device can be improved by depositing the phosphors as separate individual layers as described later with reference to FIGS. 3 to 6 depending on the phosphors to be combined. Placement of a phosphor is either a separate layer as shown in FIG. 6 from a mixture of phosphor or 3 as shown in FIG. 1, the excitation spectrum of the phosphor to be determined by the torque and the emission spectrum and uses Become. There are three uses: a luminaire with phosphors deposited directly on the LED, a display with phosphors spaced apart from the LEDs, and lighting with phosphors spaced apart from the LEDs. The device is described below. For luminaires, the placement of the phosphor can be selected to maximize the color rendering index given as CRI or Ra. In the case of display devices, the placement of the fluorophore can be selected to maximize the color gamut of the filters used in the device. It is desirable to maximize the equivalent brightness in both the lighting device and the display device. Equivalent brightness is the maximum efficiency possible for a given spectrum and is expressed in lumens / watts.

1 and 3 to 6 show a first-use luminaire with a phosphor deposited directly on an LED as a mixture in FIG. 1 and as individual layers in FIGS. 3-6. It is a thing. In the luminaire, the arrangement of the phosphors is chosen to maximize the equivalent brightness and color rendering index. Judgment as to which of the different fluorophore arrangements shown in FIGS. 1 and 3 to 6 is appropriate for the specific combination of fluorophore is in two examples, namely Y.₃Al₅O₁₂: Ce³⁺Fluorescent material and Sr₂Si₅N₈:EU²⁺Elements with phosphors and Y₃Al₅O₁₂: Ce³⁺Fluorescent material and CaS: Eu²⁺The explanation will be given in the context of an element having a phosphor.

In the first example, the blue light emitting diode is Y₃Al₅O₁₂: Ce³⁺Fluorescent material and Sr₂Si₅N₈:EU²⁺Combined with a fluorophore. Figure 2 shows Y₃Al₅O₁₂: Ce³⁺And Sr₂Si₅N₈:EU²⁺The excitation spectrum and the emission spectrum of are shown. A first-order approximation of the coupled light emitted by this system adds the spectrum of the blue light emitting diode and the spectrum of the two phosphors. Y₃Al₅O₁₂: Ce³⁺And Sr₂Si₅N₈:EU²⁺The emission spectrum of both shows that both phosphors emit strongly at an orange wavelength of, for example, about 600 nm. Overlapping emission spectra at orange wavelengths shift the appearance of mixed light away from red towards shorter wavelengths. This shift can adversely affect the color rendering of the mixed light.

In addition, Figure 2 shows Y₃Al₅O₁₂: Ce³⁺Emission spectrum of Sr₂Si₅N₈:EU²⁺It is shown that it overlaps with the excitation spectrum of. As a result, Y₃Al₅O₁₂: Ce³⁺Part of the light emitted from the phosphor is Sr₂Si₅N₈:EU²⁺It will be consumed by the phosphor and will reduce the amount of green / yellow light in the mixed light. In addition, Y₃Al₅O₁₂: Ce³⁺Light emitted by Sr₂Si₅N₈:EU²⁺Absorption by this causes a shift of the mixed light in the shorter orange wavelength direction. Both actions can adversely affect the color rendering of the mixed light.

The absorption of the light emitted by the green / yellow luminescent phosphor by the red luminescent phosphor can be reduced by dividing the green / yellow luminescent material and the red luminescent material into separate regions. 3 to 6 show embodiments of an element in which a red light emitting phosphor and a green / yellow light emitting phosphor are deposited so as to reduce absorption of light emitted by the green / yellow light emitting phosphor by the red light emitting phosphor. Is shown.

In the device shown in FIG. 3, the semiconductor light emitting device 1 is deposited in the reflector cup 2. The green / yellow fluorophore 5 is mixed with resin, silicon, or other transparent material and deposited on one side of the reflector cup 2, while some other fluorophore 4, including the red fluorophore, Mixed with resin, silicon, or other transparent material, the slurry 5 is deposited on the other side of the reflector cup 2 so that it mixes little with the slurry 4. In some embodiments, the viscosity of the slurry-like transparent material is selected so that the fluorophore 4 does not mix with the fluorophore 5. The light emitted by the green / yellow fluorophore 5 emits some red light within the slurry 4 because the green / yellow fluorophore 5 and some other fluorophore 4 are adjacent to each other rather than being mixed into the same slurry. It is unlikely to be absorbed by the phosphor.

In the device shown in FIG. 4, the green / yellow luminescent phosphor 5 and the other phosphor 4 are deposited on the LED 1 as individual layers. The fluorophore layer 4, which contains some red-emitting fluorophore, is deposited closest to LED1. The green / yellow luminescent phosphor 5 is then deposited on the phosphor layer 4. The phosphor layers 4 and 5 can be separated by any transparent layer 6. The phosphor layers 4 and 5 are deposited as a slurry of resin or other transparent material, or as a thin film by, for example, electron beam deposition, thermal deposition, high frequency sputtering, chemical vapor deposition, or atomic layer epitaxy. Alternatively, it can be deposited as a conformal layer on LED1 by, for example, screen printing, the stencil described in US Pat. No. 6,650,044, or the electrophoretic deposition method described in US Pat. No. 6,576,488. The thin film is described in detail in US Pat. No. 6,696,703. U.S. Pat. Nos. 6,696,703, U.S. Pat. No. 6,650,044, and U.S. Pat. No. 6,576,488 are each incorporated herein by reference. In contrast to thin films, which typically function as a single large fluorophore particle, the conformal layer fluorophore generally functions as a large number of fluorophore particles. In addition, thin films typically contain no material other than phosphors. The conformal layer often contains a non-fluorescent material, such as silica.

In some embodiments, one or more dichroic filters are included within the device. A dichroic filter designed to allow the light emitted by the LED1 to pass through but to reflect the light emitted by the phosphors 4 and 5 can be sandwiched between the LED1 and the phosphor layer 4. The layer 6 between the green / yellow fluorescee 5 and the red fluorescee 4 is a dichroic filter designed to pass the light emitted by the red fluorescee 4 and LED1 and is a green / yellow luminescent filter. The light emitted by the phosphor 5 can be reflected. The dichroic filter can reduce the amount of backscattered radiation into LED1 by the fluorophore layers 4 and 5 and absorb that radiation.

In the device shown in FIG. 5, the green / yellow luminescent phosphor 5 and the other phosphor 4 are deposited in a plurality of microscopic regions on the LED1. A pattern such as a checkerboard pattern is formed by different regions. When the light from LED1 is emitted without being converted, such as when the blue light emitted by the LED is mixed with the green light and red light emitted by the phosphor to become white light. The amount of unconverted light adjusts the thickness of phosphor regions 4 and 5, or leaves an uncovered region of LED1 or is covered by any transparent material 7 that does not convert the light emitted by that LED1. It can be controlled by leaving the area of LED1 that is called. The patterns of the different illuminant layers, as shown in FIG. 5, are such that the first phosphor layer is deposited by electrophoretic precipitation, the layer is patterned using conventional lithography and etching techniques, and then the second. It can be formed by depositing the phosphor layer of the above by an electrophoretic precipitation method. Alternatively, the pattern of the phosphor layer can be deposited by screen printing or ink jet printing. In some embodiments, the pattern of the fluorescent layer can be formed by dispensing the individual fluorescent mixtures 4 and 5 into the wells of a clear plastic microplate used in microbiology. The fluorophore-filled microplate is then placed on LED1. The fluorophore-filled microplate can be formed separately from LED1.

In the device shown in FIG. 6, a plurality of minute regions of the phosphor 4 including some red emitting phosphor are formed on the surface of the LED 1. A layer of green / yellow luminescent phosphor 5 is deposited on multiple regions of the fluorophore 4.

Each of the embodiments shown in FIGS. 3 to 6 can alleviate the absorption problem described above. In either case, the light emitted by LED1 first enters the red-emitting phosphor or the red-emitting phosphor and the green / yellow-emitting phosphor in separate regions. Thus, the arrangement shown in FIGS. 3 to 6 reduces the probability that the light emitted from the green / yellow luminescent phosphor will be absorbed by the red luminescent phosphor.

By separating the phosphors as shown in FIGS. 3-6, the blue LED and Y₃Al₅O₁₂: Ce³⁺Fluorescent material and Sr₂Si₅N₈:EU²⁺The color rendering of the lighting system, including the phosphor, is significantly improved. FIG. 15 shows the blue LED and Y in the mixed fluorophore arrangement (curve a) as shown in FIG. 1 and the layered fluorophore arrangement (curve b) as shown in FIG.₃Al₅O₁₂: Ce³⁺Fluorescent material and Sr₂Si₅N₈:EU²⁺The spectrum of the mixed light from the phosphor is shown. Both fluorophore arrangements have a high equivalent brightness of 296 for the layered arrangement and 343 for the mixed type arrangement, but the layered arrangement has a significantly higher color rendering index of 87 compared to 75 for the mixed type arrangement. Shows the index.

In some embodiments, the blue LED is Y₃Al₅O₁₂: Ce³⁺Fluorescent material and CaS: Eu²⁺Separation of the green / yellow luminescent phosphor and the red luminescent phosphor does not improve the performance of the device, as shown in the example of the second lighting system when combined with a phosphor. Figure 14 shows Y₃Al₅O₁₂: Ce³⁺And CaS: Eu²⁺The excitation spectrum and the emission spectrum of are shown. The leftmost solid line is Y₃Al₅O₁₂: Ce³⁺Is the excitation spectrum of. The solid line in the center is Y₃Al₅O₁₂: Ce³⁺Is the emission spectrum of. The dashed line is CaS: Eu²⁺Is the excitation spectrum of. The rightmost solid line is CaS: Eu²⁺Is the emission spectrum of. Figure 7 shows the blue LED and Y₃Al₅O₁₂: Ce³⁺Fluorescent material and CaS: Eu²⁺Three spectra of synthetic light from the system containing the phosphor are shown. Curve a is a simulation spectrum calculated by superimposing the emission spectra of the light emitting diode and the two phosphors. Curve b is an observation spectrum from the device formed by mixing the two phosphors in a single layer as shown in FIG. Curve c is an observation spectrum from an element containing two separate phosphor layers as shown in FIG. By layering the phosphor, the equivalent brightness of the device is reduced. The layered element has a color rendering index of 96 and an equivalent brightness of 265. The mixed element has Ra of 91 and equivalent brightness of 300. Therefore, even if the phosphor is layered, the color rendering is not improved so much, and the equivalent brightness of the device is reduced. As a result, it is preferable to mix the phosphors.

Many factors will determine whether it is best to mix a large number of phosphors or to form them as separate layers. The difference in refractive index between the two phosphors and the difference in particle size between the two phosphors affect the absorbency of the emission from the green / yellow phosphor by the red phosphor. As the difference in refractive index between two substances increases, it is more likely that the incident light at the interface between the two substances will be reflected rather than absorbed. Thus, when the refractive indexes of the two phosphors are significantly different, the light emitted by the green / yellow phosphor is more likely to be scattered rather than absorbed when incident on the red phosphor. In addition, the position of the emission spectrum of the red-emitting phosphor may determine whether the two phosphors should be mixed. As mentioned above, the interaction between the green / yellow luminescent phosphor and the red luminescent phosphor shifts the red component of the synthetic light from the system towards the shorter orange wavelength direction, resulting in reduced color performance. As the peak wavelength of the red-emitting phosphor becomes longer, the system will be able to tolerate a shift of red towards shorter wavelengths without affecting color rendering. Similarly, the overlap between the emission spectrum of the green / yellow luminescent phosphor and the excitation spectrum of the red luminescent phosphor will determine whether the two illuminants should be mixed. The greater the overlap, the more likely it is that more of the amount of light emitted from the green / yellow luminescent phosphor will be absorbed by the red luminescent phosphor. Therefore, the greater the overlap, the more likely it is that the performance of the system will change by separating the fluorophore.

In some embodiments, the fluorophore is separated into separate layers, for example a small amount of red luminescent phosphor can be included in the green / yellow luminescent phosphor layer. The presence of a small amount of red light emitting phosphor in the green / yellow light emitting phosphor layer can improve the color rendering of the synthesized light.

FIG. 8 shows a second application, a display device with phosphors spaced apart from one or more LEDs. The device shown in FIG. 8 was filed on October 3, 2003, with the title of the invention being "LCD Backlight Using Two-Dimensional Array LEDs" and is incorporated herein by reference in US Application Serial No. 10 / 678,541. , Will be explained in more detail. FIG. 8 is a side view of the LCD display. The LED array 24 is mounted on the rear panel of the backlight 26. The backlight 26 is covered with a diffusion cover plate 40. The diffuser 40 is made of, for example, acrylic or glass and has a rough surface to diffuse light. Alternatively, the diffuser 40 can also include light scattering particles along with a sheet of acrylic or glass. Many types of diffusers are known and can be used with backlight 26. If the light output of the backlight 26 is sufficiently diffused without the diffuser, a transparent plate can be used instead of the diffuser 40. Manufactured by 3M, for example, Brightness, for example Additional films (not shown) for increasing brightness or efficiency, such as Enhancement Films and Dual Brightness Enhancement Films, may be used just prior to the LCD on the top surface of the diffuser.

The rear surface and side walls of the backlight 26 are covered with a highly reflective material. Good results were obtained with a white diffuse film (eg E60L manufactured by Toray of Japan) on the back and a specular material (eg Miro material manufactured by Alanod of Germany) on the side walls. However, other configurations work as well. The material used should preferably have a high reflectance coefficient greater than 90%. A high reuse rate is achieved by using such a highly reflective material. This is because such films cannot be used in the first optical path and reflect light between the second or third optical paths that needs to be reused to contribute to the output of the LCD. This is especially important when the Brightness Enhancement Film is used as described above.

The LCD panel 14 is installed in front of the backlight 26. The LCD panel 14 comprises a first polarizing filter, a thin film transistor array for generating an electric field across a selection of liquid crystal layers, a liquid crystal layer, an RGB color filter array, and a second polarizing filter. It can be a conventional LCD having. The color filter array has red, green, and blue subpixels. An additional film, such as a brightness-enhancing film (BEF) or a polarization recovery film (DBEF), can be used between the LCD panel 14 and the backlight 26.

The LED26 is generally a blue or UV emitting LED. A fluorescent layer 39, which can contain a large number of phosphors that can be mixed as shown in FIG. 1 or layered as shown in FIGS. 3-6, is not directly on the LED 26 but on the cover plate 40. Formed on top. In some embodiments, different fluorescent layers are formed on different surfaces of the cover plate 40. The cover plate 40 may or may not be a diffuser, depending on the amount of diffusion performed by the phosphor. Due to the high reflectance of the film used for the backlight 26, the light emitted from the phosphor to the rear of the backlight 26 has a higher reuse rate than the light entering the LED chip. It is preferable to place it away from. In addition to the reuse rate, the fluorophore does not have to withstand high temperatures near the LED or be chemically compatible with the LED, increasing the number of suitable fluorophores available, increasing the efficiency of the device and Life may be improved. The blue backlight can be used in a wide variety of different displays with different types of color filters, and to fit a particular LCD, simply optimize the thickness of the phosphor layer and the concentration of the phosphor. Since it is good, this solution is also noteworthy from a logistics point of view. In the display device shown in FIG. 8, the phosphor arrangement is selected to maximize equivalent brightness and color gamut.

9, FIG. 10, FIG. 11, FIG. 12, and FIG. 13 show the performance of several phosphor compositions combined with blue light emitting diodes. In each of FIGS. 9 to 13, curve a represents a Planck locus considered to be true white light, and curve b represents a CIE chart. Curve c shows the color gamut enabled by using the filter in the RGB pixel filter of the device of FIG. The point d represents the color of the mixed light emitted by the LED and the phosphor. The curve e represents the color gamut required by the NTSC standard. The point f represents the color of the light after being filtered by each of the red, blue, and green filters. Point g shows the spectrum of synthetic light before filtering. Curves h, i, and j show the performance of the blue, green, and red filters of the RGB pixel filter of FIG. The curve k shows the synthetic light emitted by the combination of the LED and the phosphor. The curve l shows the synthetic light after passing through the blue filter represented by the curve h. The curve m shows the synthetic light after passing through the green filter represented by the curve i. Curve n shows the synthetic light after passing through the red filter represented by curve j.

In the device shown in FIG. 9, for example, a blue LED that emits 455 nm light is Y, which is a single phosphor.₃Al₅O₁₂: Ce³⁺Combined with. The device shown in FIG. 9 operates at equivalent luminance 299 and has a color gamut that is 62% of the NTSC standard color gamut range.

In the apparatus shown in FIG. 10, the red luminescent phosphor SrS: Eu²⁺Is added to the device in Figure 9. SrS: Eu²⁺The addition does not significantly affect the performance of the device. The device shown in FIG. 10 operates at equivalent luminance 291 and has a color gamut that is 62% of the NTSC standard color gamut range.

The device shown in FIG. 11 uses a blue light emitting diode SrGa.₂S₄:EU²⁺And CaS: Eu²⁺It is to be combined with. This device has an excellent color gamut (86% of NTSC), but with a low quality equivalent brightness of 200. In this case, it is preferable to form individual fluorophore regions as shown in FIGS. 3 to 6, rather than mixing the fluorophores as shown in FIG.

In the device shown in FIG. 12, CaS: Eu of the device shown in FIG. 11²⁺Is SrS: Eu²⁺Is replaced by. This device exhibits excellent color gamut (73% of NTSC) and excellent equivalent brightness (298). In this case, it is preferable to form individual fluorophore regions as shown in FIGS. 3 to 6, rather than mixing the fluorophores as shown in FIG.

The device shown in FIG. 13 uses a blue light emitting diode Sr._1-xBa_xSiO₄:EU²⁺And Sr₂Si₅N₈:EU²⁺It is to be combined with. This device has a color gamut of 72% of NTSC and an equivalent brightness of 241.

In a third application, the illuminator comprises phosphors spaced apart from one or more LEDs. An example of such a device is the device shown in FIG. 8 with the LCD 14 omitted. In these embodiments, the fluorophore arrangement is chosen to maximize equivalent brightness and color rendering index. In the first application, a combination of phosphors as described above would be appropriate.

Although the present invention has been described in detail, those skilled in the art can make modifications to the present invention on the premise of the present disclosure without departing from the spirit of the concept of the invention described in the present specification. Will understand. Therefore, it is not intended that the scope of the invention be limited to the particular embodiments exemplified and described.

<figref num="1">A lighting system that compensates for the lack of red color, which is a conventional technique, is shown.</figref><figref num="2">Sr₂Si₅N₈:EU²⁺The excitation spectrum of the above and the emission spectrum of some phosphors are shown.</figref><figref num="3">Embodiments of the present invention are shown in which separate phosphor layers are used to minimize phosphor interaction.</figref><figref num="4">Embodiments of the present invention are shown in which separate phosphor layers are used to minimize phosphor interaction.</figref><figref num="5">Embodiments of the present invention are shown in which separate phosphor layers are used to minimize phosphor interaction.</figref><figref num="6">Embodiments of the present invention are shown in which separate phosphor layers are used to minimize phosphor interaction.</figref><figref num="7">Blue light emitting diode and Y₃Al₅O₁₂: Ce³⁺Fluorescent material and CaS: Eu²⁺The simulation spectrum of the system including the phosphor and the two spectra obtained from the experiment are shown.</figref><figref num="8">The display which concerns on embodiment of this invention is shown.</figref><figref num="9">An example of the combination of the LED and the phosphor used in the device of FIG. 8 is shown.</figref><figref num="10">An example of the combination of the LED and the phosphor used in the device of FIG. 8 is shown.</figref><figref num="11">An example of the combination of the LED and the phosphor used in the device of FIG. 8 is shown.</figref><figref num="12">An example of the combination of the LED and the phosphor used in the device of FIG. 8 is shown.</figref><figref num="13">An example of the combination of the LED and the phosphor used in the device of FIG. 8 is shown.</figref><figref num="14">Y₃Al₅O₁₂: Ce³⁺Fluorescent material and CaS: Eu²⁺The excitation spectrum and the emission spectrum of the phosphor are shown.</figref><figref num="15">Blue light emitting diode and Y₃Al₅O₁₂: Ce³⁺Fluorescent material and Sr₂Si₅N₈:EU²⁺Two spectra obtained from experiments on the system containing phosphors are shown.</figref>

Code description

1: Semiconductor light emitting device 2: Reflector cup 4, 5: Fluorescent material 6: Layer 7: Transparent material 14: LCD 24: LED array 26: Backlight 39: Fluorescent layer 40: Cover plate