JP2008231218A - Phosphor material and white light-emitting diode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a phosphor material which emits light being a homogeneous mixture of excitation light for phosphor excitation and fluorescent light emitted from the phosphor and to provide a white LED using the same. <P>SOLUTION: The phosphor material is one which comprises a translucent polycrystalline material having both the property of transmitting light and the property of scattering light and having a scattering coefficient of 10-700 cm<SP>-1</SP>at a wavelength of 550 nm and emits, upon being irradiated with excitation light comprising visible light, light being a homogeneous mixture of light comprising excitation light and fluorescent light from the luminescent face opposite to the excitation face irradiated with the excitation light by the mechanism in which, upon such irradiation, it absorbs part of the excitation light to emit fluorescent light in a wavelength region different from that of the excitation light and the scattering of the excitation light and of the fluorescent light is repeated within the polycrystalline material. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a phosphor material, and more specifically, a phosphor material capable of emitting fluorescence by excitation light and emitting white light by synthesizing transmitted excitation light and fluorescence, and a white LED using the phosphor material It is about.

  A white LED that combines a blue LED (Light Emitting Diode) chip and a YAG phosphor that emits yellow light by blue light emitted from the blue LED chip has been developed (Patent Document 1). This white LED has advantages such as long life, low power consumption, and no inclusion of environmentally hazardous substances, as compared to conventional light sources such as lighting devices, so it can be used as a next-generation light source to replace incandescent bulbs and fluorescent lamps. Expected.

  However, the white LED disclosed in Patent Document 1 has a structure in which the phosphor is in a powder state and is thus mixed with a transparent resin and provided on the excitation LED. For this reason, the transparent resin deteriorates due to heat or light emitted from the LED chip, causing discoloration. As a result, there is a problem in that the emission intensity is reduced and the chromaticity shift occurs and the life of the LED is shortened. In order to solve such a problem, a structure is conceivable in which glass is used in place of the transparent resin, and crystals serving as phosphors are held in the glass matrix. According to such a structure, deterioration due to heat generated from the LED chip can be suppressed. However, there exists a subject that luminous efficiency becomes low compared with commercially available white LED.

  Further, a commercially available white LED has a structure in which a phosphor emitting yellow light is provided on a blue LED as described above, but the so-called arrangement in which the color tone of the obtained white light is different between the central portion and the end portion. There is also a problem that optical characteristics are poor. This is considered to be due to the variation in the thickness of the phosphor provided on the LED chip and the shape of the portion to which the phosphor is applied. As a method for improving such a light distribution characteristic, a method of mixing a scattering agent that scatters light in a resin in which a phosphor is dispersed or a concentration distribution on the phosphor can be considered. In terms of height.

The present invention uses a phosphor material made of ceramic as described later. Patent Document 2 discloses that a phosphor material made of ceramic is used and a wavelength conversion layer is formed from this phosphor material. However, the wavelength conversion layer made of ceramic disclosed in this prior art is intended to convert incident light by wavelength conversion and emit the light as in the present invention. It is not a translucent polycrystalline body that has both the properties of scattering.
JP 2000-208815 A JP 2006-5367 A

  An object of the present invention is to provide a phosphor material capable of emitting light in which excitation light for exciting a phosphor and fluorescence emitted from the phosphor are homogeneously mixed, and a white LED using the phosphor material. It is in.

The phosphor material of the present invention has both a property of transmitting light and a property of scattering light, and is composed of a translucent polycrystalline body having a scattering coefficient of 10 to 700 cm ⁻¹ at a wavelength of 550 nm, and from visible light. When the excitation light is irradiated, a part of the excitation light is absorbed and fluorescence in a wavelength region different from that of the excitation light is emitted, and the excitation light and the fluorescence are scattered inside the polycrystal to be irradiated with the excitation light. It is characterized by emitting light in which excitation light and fluorescence are uniformly mixed from a light emitting surface opposite to the excitation surface.

The phosphor material of the present invention comprises a translucent polycrystal having both a property of transmitting light and a property of scattering light, and a scattering coefficient of 10 to 700 cm ⁻¹ at a wavelength of 550 nm. For this reason, when excitation light composed of visible light is irradiated, a part of the excitation light is transmitted through the polycrystalline body and emitted from the light emitting surface opposite to the excitation surface irradiated with the excitation light. Further, part of the excitation light is absorbed and emits fluorescence in a wavelength region different from that of the excitation light. In addition, inside the polycrystal, the excitation light and the fluorescence are repeatedly scattered, so that the light in which the excitation light and the fluorescence are homogeneously mixed from the light emitting surface opposite to the excitation surface irradiated with the excitation light. Emits light. Therefore, according to the present invention, a phosphor material that emits light in which excitation light for exciting the phosphor and fluorescence emitted from the phosphor are homogeneously mixed can be obtained.

The phosphor material of the present invention is characterized in that the scattering coefficient at a wavelength of 550 nm is 10 to 700 cm ⁻¹ . This scattering coefficient is an index indicating the degree of the property of transmitting light and the property of scattering light in the translucent polycrystalline body. When the scattering coefficient is smaller than 10 cm ^−1, the probability that the excitation light travels straight without being absorbed or reflected in the polycrystalline body is increased, and as a result, the color emitted from the light emitting surface is colored in the central portion and the peripheral portion. A difference occurs in the degree, resulting in poor light distribution. On the other hand, if the scattering coefficient is larger than 700 cm ^{−1, the} loss due to light scattering increases and the intensity of the obtained light decreases. When the scattering coefficient is in the range of 10 to 700 cm ⁻¹ , excitation light and fluorescence are appropriately scattered inside the polycrystalline body, and both are uniformly mixed. As a result, light emission with excellent color distribution and no color unevenness can be obtained. Scattering coefficient is more preferably within a range of 20～500Cm ^-1, more preferably in the range of 50～400Cm ^-1, particularly preferably in the range of 100~300cm ^-1. The scattering coefficient μ is defined by the following equation, where L is the thickness (cm) of the sample, T is the transmittance, and R is the reflectance.

μ = − (1 / L) × ln (T / (1-R) ² )
In the present invention, the size of the microcrystalline particles in the polycrystal is preferably in the range of 10 to 100 μm. By setting the crystal particle diameter in the polycrystal within the range of 10 to 100 μm, the excitation light and the fluorescence emitted by the excitation light can be multiple-reflected at the microcrystal interface and scattered more effectively. When the particle diameter of the microcrystalline particles is smaller than 10 μm, the amount of light scattering becomes too large, and the intensity of the obtained light is lowered. On the other hand, when the particle diameter of the microcrystal is larger than 100 μm, the linear transmittance of the excitation light in the phosphor material increases, and the chromaticity varies.

  The scattering coefficient in the present invention can be controlled by the size of the crystal particle diameter. As the crystal particle diameter increases, the area of the crystal particle interface for scattering light decreases, so that the property of transmitting light increases and the property of scattering light decreases. As a result, the scattering coefficient is reduced and the light emission intensity is increased, but the light distribution is lowered.

  As the crystal particle diameter decreases, the area of the crystal particle interface for light scattering increases, so that the property of scattering light increases and the property of transmitting light decreases. As a result, the scattering coefficient increases and the emission intensity decreases.

  The range of the crystal particle diameter of the microcrystalline particles in the polycrystal is more preferably 15 to 70 μm, and particularly preferably 20 to 50 μm.

  The size of the microcrystalline particles in the polycrystal can be measured as an average value by observation with an electron microscope.

  The particle diameter of the microcrystalline particles in the polycrystal can be controlled by adjusting the firing temperature and firing time when firing the material into a member. The higher the firing temperature, the larger the crystal particle size, and conversely, the lower the firing temperature, the smaller the crystal particle size. Further, the longer the firing time, the larger the crystal particles, and conversely, the shorter the firing time, the smaller the crystal particle diameter.

  In the present invention, the polycrystalline body preferably has a property of absorbing light having a wavelength of 400 to 500 nm and emitting fluorescence of light having a wavelength of 450 to 780 nm. More preferably, it has a property of absorbing blue light and emitting yellow fluorescence. By using such a polycrystal, the light emitted from the polycrystal and the excitation light transmitted through the polycrystal are synthesized, and white light can be emitted. Blue light means light having a central wavelength at a wavelength of 430 to 480 nm, and yellow light means light having a central wavelength at a wavelength of 535 to 590 nm.

The polycrystal in the present invention is preferably composed of a microcrystal containing Ce ³⁺ in a garnet crystal. By adopting a structure containing Ce ^{3+ in the} garnet crystal, Ce ³⁺ becomes the emission center, absorbs blue excitation light, and can emit yellow fluorescence.

The concentration of Ce ₂ O ₃ in the polycrystal is preferably 0.001 to 0.5 mol%. When the content of Ce ₂ O ₃ is reduced, the intensity of yellow fluorescence emitted from Ce ³⁺ becomes weak and it becomes difficult to obtain white light. On the other hand, when the content of Ce ₂ O ₃ is increased, most of the excitation blue light is absorbed and only yellow fluorescence is obtained, so that it is difficult to obtain white light. The more preferable range of the content of Ce ₂ O ₃ is 0.002 to 0.2 mol%, and particularly preferably 0.005 to 0.1 mol%.

The garnet crystal is generally a crystal represented by A ₃ B ₂ C ₃ O ₁₂ (A = Mg, Mn, Fe, Ca, Y, Gd, etc .: B = Al, Cr, Fe, Ga, Sc, etc .: C = Al, Si, Ga, Ge, etc.) As the above-mentioned garnet crystal, particularly a YAG crystal (Y ₃ Al ₅ O ₁₂ crystal) or a YAG crystal solid solution, a desired yellow fluorescence can be obtained. It is preferable because it emits light. As a YAG crystal solid solution, a part of Y is at least one element selected from the group consisting of Gd, Sc, Ca and Mg, and / or a part of Al is a group consisting of Ga, Si, Ge and Sc. YAG crystal solid solution substituted with at least one element selected from

To obtain the phosphor material, first, A ₃ B ₂ C ₃ O ₁₂ (A = Mg, Ca, Y, Gd, etc .: B = Al, Ga, Sc, etc .: C = Al, Si, Ga, Ge, etc.) Etc.), A, B and C oxide raw materials having a high purity and a particle size of several μm or less are weighed, and Ce ₂ O ₃ is added in an amount of 0.001 to 0.5 mol. %Added. Next, after sufficiently stirring and mixing with a ball mill or the like, the obtained powder is press-molded at a pressure of 150 to 250 MPa. Subsequently, the obtained molded body is fired at a temperature of 1500 ° C. to 1800 ° C. At this time, firing is performed in a reduced pressure atmosphere of 1000 Pa or less in a part of the temperature raising process. By doing so, it is possible to obtain a phosphor material having a property of absorbing light having a wavelength of 400 to 500 nm as described above and emitting fluorescence of light having a wavelength of 450 to 780 nm.

  The phosphor material in the present invention, that is, the polycrystalline body, may have an arbitrary shape, for example, a disk shape, a columnar shape, a rod shape, or the like. Such a shape can be formed by cutting and polishing the phosphor material.

  The phosphor material in the present invention, that is, the polycrystalline body may have an arbitrary shape as described above, but it is particularly preferable to have a plate shape. The reason is that if the phosphor material is plate-like, the thickness can be easily made uniform throughout, so that when the excitation light is incident and excited, the resulting chromaticity is less likely to be distributed.

  The thickness when the phosphor material of the present invention is plate-shaped is preferably 0.01 to 1.0 mm. If the thickness of the phosphor material is too thin, the amount of crystals in the phosphor material is reduced, for example, the yellow fluorescence intensity becomes weak, and white light may not be obtained. Moreover, if the thickness is too thick, for example, blue excitation light is hardly absorbed and transmitted, and as a result, it is difficult to obtain a phosphor material that emits white light. A more preferable range of the thickness when the phosphor material is plate-shaped is 0.05 to 0.8 mm, particularly preferably 0.1 to 0.5 mm.

  The white LED of the present invention is characterized by using the phosphor material of the present invention. Specifically, a light source of excitation light for irradiating the phosphor material with excitation light and the phosphor material of the present invention are provided. Specifically, a blue LED element or the like is provided as a light source for excitation light. In the white LED, part of the blue light incident on the phosphor material is wavelength-converted to yellow fluorescence by the phosphor, and the remaining blue light is transmitted. By combining the wavelength-converted yellow light and the blue light transmitted through the phosphor material to synthesize a spectrum close to white tone, the blue light can be converted into white light.

  ADVANTAGE OF THE INVENTION According to this invention, it can be set as the fluorescent substance material which emits the light with which the excitation light for exciting a fluorescent substance and the fluorescence emitted from a fluorescent substance were mixed uniformly. Since the phosphor material of the present invention does not use a resin material as a matrix unlike the conventional wavelength conversion member, it can suppress a decrease in emission intensity and a shortened life due to deterioration of the resin, and has a high emission intensity. And it can be set as the fluorescent material excellent in light emission light distribution.

  In addition, since the white LED of the present invention uses the phosphor material of the present invention, it is possible to suppress a decrease in light emission intensity and a shortened life, and a white light having high light emission intensity and excellent light emission light distribution. It can be an LED.

  Since the phosphor material and the white LED of the present invention are excellent in light distribution and can emit light with high intensity, they are suitable as materials used for light sources for lighting, displays and the like, and light sources for headlights such as automobiles. It is a thing.

  Hereinafter, the present invention will be described with reference to specific examples, but the present invention is not limited to the following examples.

(Examples 1-10 and Comparative Examples 11-12)
The phosphor material was fired and manufactured as follows.

  First, oxide raw materials having high purity and a particle diameter of 2 μm or less were weighed so as to have the compositions shown in Tables 1 and 2. Tetraethoxysilane was added as a sintering aid to the weighed oxide raw materials so that each amount would be 0.6% by weight. Next, the mixture was stirred and mixed in ethanol using an alumina ball mill for 17 hours. Thereafter, the powder was dried in a reduced-pressure atmosphere, and the obtained powder was press-molded at a pressure of 200 MPa to obtain a press-molded body. Next, this press-molded body was fired under the firing conditions shown in Tables 1 and 2. The rate of temperature increase was 10 ° C./min up to 1000 ° C., and the rate of temperature increase from 1000 ° C. was 5 ° C./min. The temperature of the firing conditions shown in Table 1 and Table 2 was set as the maximum temperature, and the maximum temperature was maintained for the time shown in Table 1 and Table 2, and then cooled to room temperature at a temperature decrease rate of 5 ° C / min. A temperature profile is shown in FIG.

  When the temperature was raised from room temperature to 1000 ° C., the pressure of the atmosphere was reduced to the atmospheric pressure at the time of temperature rise shown in Tables 1 and 2. This decompression was carried out to a temperature 50 ° C. lower than the maximum temperature. The above reduced pressure state was maintained until the temperature reached 50 ° C. below the maximum temperature, and the vacuum pump was stopped at a temperature 50 ° C. below the maximum temperature. Since the vacuum pump was stopped, the atmospheric pressure gradually increased thereafter. The atmospheric pressure profile is shown in FIG. The atmospheric pressure at the time of temperature increase shown in Table 1 and Table 2 is the lowest pressure in the atmospheric pressure profile shown in FIG.

  The obtained phosphor material was polished until the thickness shown in Tables 1 and 2 was obtained, and a plate-like phosphor material was produced. With respect to this plate-like phosphor material, the total luminous flux, the scattering coefficient at a wavelength of 550 mm, the crystal particle diameter, the chromaticity, the emission color and the light distribution were measured.

  In measuring the total luminous flux, the phosphor material was excited with a blue LED (wavelength 465 nm, operating current 20 mA) in an integrating sphere, the emission spectrum was taken into a PC through a small spectroscope, and measured by calculation.

  The chromaticity was calculated from the obtained emission spectrum.

The scattering coefficient μ is calculated from the formula μ = − (1 / L) × ln (T / (1-R) ² ) using the sample thickness L (cm), linear transmittance T, and reflectance R. did.

  The crystal particle diameter was calculated from an image obtained by observing the fracture surface of the phosphor material with an electron microscope. The crystal particle diameter is a number average particle diameter.

  The luminescent color was judged by visual observation.

  The light distribution was evaluated as x when a difference in chromaticity was confirmed on the paper surface when the paper surface was illuminated with emitted light, and was evaluated as ◯ when no difference was confirmed in the chromaticity on the paper surface.

  The evaluation results are shown in Tables 1 and 2.

As shown in Table 1, in Examples 1 to 10 according to the present invention, white light having excellent light distribution was obtained, and the value of the total luminous flux was also high. On the other hand, as shown in Table 2, it can be seen that Comparative Example 11 is inferior in light distribution because the scattering coefficient is as small as 5 cm ⁻¹ . In Comparative Example 12, since the scattering coefficient is as large as 770 cm ⁻¹ , the total luminous flux is as low as 0.5 lm, and the light emission intensity is low.

(White LED)
1-6 is typical sectional drawing which shows embodiment of white LED according to this invention. In the embodiment shown in FIGS. 1 to 3, the phosphor member 1 is placed in contact with the LED chip 2. As shown in FIGS. 1 to 3, when the phosphor member 1 and the LED chip 2 are placed in contact with each other, an adhesive is applied to at least a part of the contact portion between the phosphor member 1 and the LED chip 2. Thus, the phosphor member 1 and the LED chip 2 are bonded. As the adhesive, silicon, an inorganic adhesive, low melting point glass, or the like can be used. As the shape of the phosphor member 1, various shapes such as a plate shape as shown in FIG. 1, a hemispherical lens shape as shown in FIG. 2, and a lid shape covering the LED chip 2 as shown in FIG. 3 are used. Can do.

  In the second embodiment shown in FIGS. 4 to 6, the phosphor member 1 is provided away from the LED chip 2 through the air layer 5. When the phosphor member 1 is installed away from the LED chip 2, a support member 4 for supporting the phosphor member 1 is used. Using such a support member 4, the phosphor member 1 can be installed away from the LED chip 2. Even if an optical component 3 (for example, a lens component) is installed on the phosphor member 1 or the LED chip 2 as shown in FIGS. 5 and 6 so that light emitted from the LED chip 2 can be efficiently extracted. Good. In addition, the attachment of the phosphor member 1 to the support member 4 and the attachment of the optical component 3 on the phosphor member 1 or the LED chip 2 are performed by applying the above adhesive to at least a part of the contact portion between the members. And can be attached by gluing.

  Examples of the LED chip 2 include an LED chip having a quantum well structure using InGaN obtained by adding In to GaN as a light emitting layer. Note that an electrode, an n-type semiconductor, a p-type semiconductor, a sapphire substrate, and the like are included in the LED chip 2 but are not shown. The optical component (lens component) 3 may be any shape as long as it has a lens effect for efficiently irradiating the phosphor member 1 with light or condensing the light emitted from the phosphor member. Plastics can be used. The support member 4 only needs to have a shape that can support the phosphor member 1, and glass, ceramic, metal, or the like can be used.

  As described above, the phosphor material of the present invention can be used as a wavelength conversion member in a white LED. However, not only the LED but also an optical component having high-power excitation light such as a laser diode (LD). It can be used as general phosphors, partial illuminations, light emitting devices such as displays, headlights of automobiles, and the like.

The typical sectional view showing the embodiment of white LED according to the present invention. The typical sectional view showing the embodiment of white LED according to the present invention. The typical sectional view showing the embodiment of white LED according to the present invention. The typical sectional view showing the embodiment of white LED according to the present invention. The typical sectional view showing the embodiment of white LED according to the present invention. The typical sectional view showing the embodiment of white LED according to the present invention. The figure which shows the temperature profile and atmospheric | air pressure profile of the baking process in the Example according to this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Phosphor member 2 ... LED chip 3 ... Optical component 4 ... Support member 5 ... Air layer

Claims (11)

It consists of a translucent polycrystal having both a property of transmitting light and a property of scattering light, and a scattering coefficient at a wavelength of 550 nm of 10 to 700 cm ⁻¹ , and when irradiated with excitation light consisting of visible light, A part of the excitation light is absorbed and fluorescence in a wavelength region different from that of the excitation light is emitted, and the excitation light and the fluorescence are repeatedly scattered inside the polycrystal to emit light on the side opposite to the excitation surface irradiated with the excitation light. A phosphor material that emits light in which excitation light and fluorescence are uniformly mixed from a surface.   2. The phosphor material according to claim 1, wherein in the step of firing the polycrystalline body, a part of the temperature raising process is sintered under a reduced pressure of 1000 Pa or less.   The phosphor material according to claim 1 or 2, wherein the size of the microcrystalline particles in the polycrystal is in the range of 10 to 100 µm.   The phosphor material according to any one of claims 1 to 3, wherein the polycrystalline body has a property of absorbing light having a wavelength of 400 to 500 nm and emitting fluorescence of light having a wavelength of 450 to 780 nm.   The phosphor material according to any one of claims 1 to 4, wherein the polycrystal has a property of absorbing blue light and emitting yellow fluorescence.   The polycrystalline body absorbs blue light and emits yellow fluorescence, and the fluorescence and blue light transmitted through the polycrystalline body are combined to emit white light. The phosphor material according to Item 1. The phosphor material according to any one of claims 1 to 6, wherein the polycrystal is composed of a microcrystal containing Ce ³⁺ in a garnet crystal. The phosphor material according to claim 7, wherein the concentration of Ce ₂ O ₃ in the polycrystal is 0.001 to 0.5 mol%. The phosphor material according to claim 7 or 8, wherein the garnet crystal is a YAG (Y ₃ Al ₅ O ₁₂ ) crystal or a YAG crystal solid solution.   The phosphor material according to any one of claims 1 to 9, wherein the polycrystal is plate-shaped and has a thickness of 0.01 to 1.0 mm.   White LED which uses the fluorescent substance material of any one of Claims 1-10.

Images