Wavelength converter and light source for generating white light

The present invention comprises a light emitting element and a phosphor, the light emitting element emits light in a first spectral range, particularly in the blue and / or ultraviolet range of the optical spectrum, and the phosphor is an alkaline earth metal orthosilikate. With respect to a light source derived from or containing at least one component of this group of luminescent materials, absorbing a portion of the light emitted by the light emitting element and emitting light in another spectral range, particularly in the yellow-green, yellow or orange range. .. The selected fluorophore is used in admixture with other fluorophores in this group and / or other luminescent materials that do not belong to this group.

The light emitting element is particularly an inorganic LED, but may be an organic LED, a laser diode, an inorganic thick film electroluminescence sheet or an inorganic thin film electroluminescence component.

Inorganic LEDs are particularly good in terms of long life, space saving, seismic resistance, and light emission in a narrow spectrum.

A large number of emission colors, especially a large number of emission colors over a wide spectrum, cannot be achieved or can only be achieved inefficiently by the internal emission of the active semiconductor material in the LED. This is especially true when obtaining white light.

According to the conventional technique, an emission color that cannot be realized internally by using a semiconductor is obtained by color conversion.

This color conversion technique is primarily based on the principle of placing at least one phosphor on the LED die. The phosphor absorbs part of the radiation emitted from this die and is excited to photoluminescence. The emission color of the light source, or light color, is produced by mixing the transmitted radiation of the die with the emitted radiation of the luminescent material.

Basically, an organic type or an inorganic type can be used as the phosphor. The main advantages of inorganic pigments are their high chemical temperature and radiation stability compared to organic pigments. In relation to the long life of inorganic LEDs, the long life inorganic phosphor guarantees high color position stability of the light source composed of two components.

If the radiation emitted by a blue light emitting LED should be converted to white light, a luminescent material that effectively absorbs blue light (450 to 490 nm) and converts it into mostly yellow luminescence radiation with high efficiency is required. .. Of course, only a few inorganic phosphors can meet this requirement. At present, YAG luminescent material class materials are often used as color conversion pigments for blue LEDs (see International Publication Nos. 98/05078 and 98/12757 pamphlets). However, this material has the disadvantage that it exhibits sufficiently high efficiency only when the material has a maximum emission value of 560 nm or less. For this reason, using a YAG pigment combined with a blue diode (450 to 490 nm), a color temperature of 6000 to 8000 K and a relatively low color rendering index (the standard value of the color rendering index Ra is 70 to 75). It is possible to realize only a cold-feeling white light color having a diode. This severely limits the range of applications. On the one hand, applying a white light source to general lighting usually places high demands on the color rendering of the luminaire, while on the other hand, customers in Europe and North America in particular prefer warm light colors with a color temperature of 2700-5000K. There is.

Furthermore, from the pamphlet of International Publication No. 00/33389, especially Ba as a phosphor for converting the light of the blue LED.₂SiO₄:EU²⁺Is known to be used. Luminescent substance Ba₂SiO₄:EU²⁺The maximum emission value of is at 505 nm, so it is not possible to reliably generate white light with such a combination.

A paper by SHM Poort et al., Optical properties of Eu²⁺-aktivated orthosilicates and orthophospates (published Journal of Alloys and Compounds Volume 260, 1997, pp. 93-97), Eu-activated Ba₂SiO₄And phosphates (eg KBaPO)₄, KSrPO₄) Properties have been studied. In the same document, Ba₂SiO₄It has been confirmed that the emission of is at 505 nm.

<p><patcit num="1"><text>International Publication No. 00/33389 Pamphlet</text></patcit></p>

<p> The object of the present invention is to obtain the above-mentioned types of light sources at the same time with high efficiency and high color rendering, and to obtain a white light color having a high color temperature, particularly the tolerance determined by the International Commission on Illumination (CIE) for general lighting. The purpose is to change the color position located in the ellipse so that it can be generated.</p>

<p><u style="single">This task is a phosphor that absorbs a part of the first emission of blue and emits the second emission in the yellow-green, yellow or orange region, and the phosphor is M.</u>_{<u style="single">2</u>}<u style="single">Si</u>_{<u style="single">1-X</u>}<u style="single">N</u>_{<u style="single">X</u>}<u style="single">O</u>_{<u style="single">4</u>}<u style="single">: Eu (where M is SrBa, SrCa, or SrBaCa, N is Ga, Ge, B, P or Al, x is less than or equal to 0.05), and the second emission is the second emission. It is solved by a phosphor that is mixed with the blue light of the rest of the light emission except for the part to generate white light.</u><u style="single">The subject is a phosphor that absorbs the first ultraviolet emission of 370 to 390 nm and emits the second emission in the yellow-green, yellow or orange region, and the phosphor is M.</u>_{<u style="single">2</u>}<u style="single">Si</u>_{<u style="single">1-X</u>}<u style="single">N</u>_{<u style="single">X</u>}<u style="single">O</u>_{<u style="single">4</u>}<u style="single">: Eu (where M is SrBa, SrCa, or SrBaCa, N is Ga, Ge, B, P or Al, x is less than or equal to 0.05), and the second emission is blue. It is solved by a phosphor that is mixed with the third emission of the above to generate white light.</u></p>

<figref num="1">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="2">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="3">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="4">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="5">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="6">The figure which shows the spectrum (relative intensity depending on the wavelength) of the LED light source by this invention.</figref><figref num="7">Schematic cross-sectional view of the first embodiment of the LED light source according to the present invention.</figref><figref num="8">Schematic cross-sectional view of a second embodiment of the LED light source according to the present invention.</figref><figref num="9">Schematic cross-sectional view of a third embodiment of the LED light source according to the present invention.</figref><figref num="10">Schematic cross-sectional view of a fourth embodiment of the LED light source according to the present invention.</figref>

Other advantages of the present invention will be described in detail below with reference to examples and drawings.

FIGS. 1 to 6 show spectra (wavelength-dependent relative intensities) of various LED light sources according to the present invention, and FIGS. 7 to 10 show various examples of LED light sources according to the present invention.

Figure 1 shows a blue LED that emits light in the first spectral range with a center of gravity wavelength of 464 nm and a composition that emits light in the second spectral range with a maximum value of 596 nm (Sr._1.4Ca_0.6SiO₄:EU²⁺) Is shown in the emission spectrum of a white LED having a color temperature of 2700K formed by the combination with the phosphor according to the present invention.

Other examples of combinations of LEDs that emit light at 464 nm with each one of the orthosilicate phosphors according to the invention are shown in FIGS. 2 and 3. Composition Sr_1.90Ba_0.08Ca_0.02SiO₄:EU²⁺When a fluorophore that has a yellow light is used for color conversion, a white light color with a color temperature of 4100K is produced, while the fluorophore Sr_1.84Ba_0.16SiO₄:EU²⁺Is used to produce, for example, a white light source with a color temperature of 6500K.

The standard spectrum of the combination of the 464 nm LED and the two orthosilicate phosphors according to the invention is shown in FIG. The luminescent material used is composition Sr_1.4Ca_0.6SiO₄:EU²⁺And Sr_1.00Ba_1.00SiO₄:EU²⁺have. A color temperature of 5088K and a color rendering index Ra of 82 are maintained for the specific spectrum shown in FIG. Naturally, all color temperatures are achieved in the range of about 3500K to 7500K depending on the selected amount ratio of the phosphor, a mixture of this kind consisting of two alkaline earth metal orthosilicate phosphors according to the present invention. The big advantage of is that Ra value of 80 or more can be obtained at the same time.

An example of this is shown in FIG. The spectra shown are a 464 nm LED and two phosphors Sr._1.6Ca_0.4Si_0.98Ga_0.02O₄:EU²⁺And Sr_1.10Ba_0.90SiO₄:EU²⁺It shows a combination with a mixture consisting of and provides a Ra value of 82 at a color temperature of 5000K.

When a UV-LED that emits light in the first spectral range having a maximum value of 370 to 390 nm is used as the light emitting device, the LED and the phosphor according to the present invention shown in FIG. Emitting barium-magnesium aluminate light emitting material: Ra value of 90 or more is realized by combination with a light emitting material mixture containing a specific component of Eu, Mn. FIG. 6 shows the emission spectrum of a white light source with 91 Ra at a color temperature of 6500K.

Other examples are listed below. In addition to the emission wavelength of the inorganic LED used and the respective composition of the phosphor according to the invention, the resulting color temperature and Ra value and the color position of the light source are shown. T = 2778K (464nm + Sr_1.4Ca_0.6SiO₄:EU²⁺); x = 0.4619, y = 0.4247, Ra = 72, T = 2950K (464nm + Sr)_1.4Ca_0.6SiO₄:EU²⁺); x = 0.4380, y = 0.4004, Ra = 73, T = 3497K (464nm + Sr)_1.6Ba_0.4SiO₄:EU²⁺); x = 0.4086, y = 0.3996, Ra = 74, T = 4183K (464nm + Sr)_1.9Ba_0.08Ca_0.02SiO₄:EU²⁺); x = 0.3762, y = 0.3873, Ra = 75, T = 6624K (464nm + Sr)_1.9Ba_0.02Ca_0.08SiO₄:EU²⁺); x = 0.3101, y = 0.3306, Ra = 76, T = 6385K (464nm + Sr)_1.6Ca_0.4SiO₄:EU²⁺+ Sr_0.4Ba_1.6SiO₄:EU²⁺); x = 0.3135, y = 0.3397, Ra = 82, T = 4216K (464nm + Sr)_1.9Ba_0.08Ca_0.02SiO₄:EU²⁺)); x = 0.3710, y = 0.3696, Ra = 82, T = 3954K (464nm + Sr)_1.6Ba_0.4SiO₄:EU²⁺+ Sr_0.4Ba_1.6SiO₄:EU²⁺+ YVO₄:EU³⁺); x = 0.3756, y = 0.3816, Ra = 84, T = 6489K (UV-LED + Sr)_1.6Ca_0.4SiO₄:EU²⁺+ Sr_0.4Ba_1.6SiO₄:EU²⁺+ Barium-magnesium aluminate: Eu²⁺); x = 0.3115, y = 0.3390, Ra = 86, T = 5097K (464nm + Sr)_1.6Ba_0.4(Si_0.98B_0.02) O₄:EU²⁺+ Sr_0.6Ba_1.4SiO₄:EU²⁺); x = 0.3423, y = 0.3485, Ra = 82, T = 5084K (UV-LED + Sr)_1.6Ca_0.4(Si_0.99B_0.01) O₄:EU²⁺+ Sr_0.6Ba_1.4SiO₄:EU²⁺+ Strontium-magnesium aluminate: Eu²⁺); x = 0.3430, y = 0.3531, Ra = 83, T = 3369K (464nm + Sr)_1.4Ca_0.6Si_0.95Ge_0.05O₄:EU²⁺); x = 0.4134, y = 0.3959, Ra = 74, T = 2787K (466nm + Sr)_1.4Ca_0.6Si_0.98P_0.02O_4.01:EU²⁺); x = 0.4630, y = 0.4280, Ra = 72, T = 2913K (464nm + Sr)_1.4Ca_0.6Si_0.98Al_0.02O₄:EU²⁺); x = 0.4425, y = 0.4050, Ra = 73T = 4201K.

In an advantageous embodiment of the present invention, the color conversion is carried out as follows.

Assemble one or more LED chips 1 (see Figure 7) on the printed circuit board 2. Directly on the LED (on the one hand to protect the LED chip and on the other hand to allow the light generated within the LED chip to be better emitted) the encapsulating material (encapsulation material) 3 Arrange in the shape of a hemisphere or hemi-ellipse. The encapsulant material 3 may include each die individually, or the encapsulant material may be a common single form for all LEDs. The printed plate 2 mounted in this manner is installed in the reflector 4, or the reflector 4 is placed on the LED chip 1.

A translucent plate 5 is installed on the reflector 4. On the one hand, the translucent plate 5 is used to protect the device, and on the other hand, the phosphor 6 is mixed in the translucent plate 5. The blue light (or ultraviolet radiation) transmitted through the transmissive plate 5 is partially converted into the second spectral range by the phosphor 6 during its transmission, resulting in an overall white color impression. The loss due to waveguides that occurs between plane-parallel plates is reduced by the opacity and scattering properties of the transmissive plate. In addition, the reflector 4 allows only the light that has already been adjusted to enter the transmissive plate 5, so that the total reflection effect is reduced from the beginning.

As shown in FIG. 8, it is also possible to adhere the phosphor 6 to the reflector 4. In this case, no translucent plate is required.

Separately, a reflector 4 ́ may be placed on each LED chip 1, and this reflector 4 ́ is made by casting a sealing material (encapsulating material) 3 ́ in a dome shape and a translucent plate. 5 is located on each reflector 4 ́, that is, on the entire device (see Figure 9).

It is advantageous to use LED arrays instead of individual LEDs to manufacture illumination sources. In an excellent variant of the present invention, the color conversion is performed on the LED array 1 ́ (see FIG. 10) in which the LED chip 1 is assembled directly on the printed circuit board 2 as follows.

The LED array 1 ́ is glued to a transparent polymer lens 7 made of another material (eg PMMA) using a casting material (eg epoxy resin) 3. The materials of the polymer lens 7 and the casting material 3 are selected to have a refractive index that is as close as possible, i.e. phase-matched. The casting material 3 resides in the maximum spherical or oval recess of the polymer lens 7. The shape of this depression is important in that the color-converting material is dispersed in the casting material 3, and therefore this shape-impartment ensures that an angle-independent emission color is obtained. Separately, the array may be first cast with a clear casting material and then adhered to the polymer lens using a casting material containing a color converter.

In order to produce a white LED with particularly good color rendering in which at least two different fluorophores are used, these fluorophores are dispersed separately rather than dispersed together in one matrix. It is advantageous to set it up. This is especially true for combinations where the final light color is obtained by a multi-stage color conversion process. That is, the longest wave emission color is produced by one emission process, which is as follows: the first phosphor absorbs the emission of the LED-the first phosphor emits light. -The second phosphor absorbs the light emission of the first phosphor-the second phosphor emits light, and so on. In particular, for this type of process, it is advantageous to place the individual phosphors back and forth in the direction of light propagation. This is because it can reduce the concentration of the material as compared to the case where the various materials are uniformly dispersed.

The present invention is not limited to the above-mentioned examples. The phosphor may be incorporated into a polymer lens (or another optical component). The phosphor can be placed directly on the LED die or on the surface of a transparent casting material. The phosphor can also be incorporated into a single matrix with scattered particles. This prevents sedimentation in the matrix and ensures uniform light emission.

1 LED chip 1 ́ LED array 2 Print plate 3, 3 ́ Sealing material 4, 4 ́ Reflector 5 Transmissive plate 6 Fluorescent 7 Polymer lens