JP2014207436A - Wavelength converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wavelength converter which can further increase an internal quantum efficiency, and the brightness of e.g. a white-light emitting module while using a binder for reliably keeping a bonding strength of a phosphor layer.SOLUTION: A wavelength converter 10 converts excitation light 12 in wavelength into light different from the excitation light 12 in luminous color. The wavelength converter 10 comprises: a translucent substrate 14; and a phosphor layer 16 formed on one principal surface 14a of the translucent substrate 14. The phosphor layer 16 includes a phosphor and glass serving as a binder, and exhibits an internal quantum efficiency of 61% or larger when being irradiated with excitation light of a wavelength of 460 nm.

Description

  The present invention relates to a wavelength converter, and for example, to a wavelength converter suitable for use with a blue light emitting element (LED (light emitting diode) or LD (semiconductor laser)) to obtain a white light emitting module.

  A general white light emitting module is composed of a blue light emitting element and an inorganic phosphor for wavelength conversion, and has a structure in which the blue light emitting element is covered with a transparent resin or glass in which the phosphor is dispersed (Patent Literature). 1 and 2). However, resin is easily deteriorated and discolored by irradiation with high-energy blue light. As a result, particularly in a high-intensity light emitting module of 1 watt or more, the luminance of the illumination is reduced and the color variation occurs. It is desirable. In addition, since the resin has a low thermal conductivity, temperature quenching of the phosphor occurs, and the luminance of the illumination decreases. Temperature quenching is a phenomenon in which the brightness of the phosphor decreases as the phosphor generates heat due to blue light irradiation and the temperature rises. In order to solve these problems, a wavelength converter having a structure in which a phosphor layer is formed on a translucent substrate having high thermal conductivity and heat generated in the phosphor is dissipated through the translucent substrate is proposed. (See Patent Document 3).

JP 2000-208815 A Japanese Patent No. 4158012 JP 2007-258228 A

  By the way, when forming a fluorescent substance layer in a translucent board | substrate, it is desirable to use a binder for ensuring the adhesive strength of a fluorescent substance layer. At this time, in order to suppress light absorption by the binder, it is necessary to reduce the amount of binder added as much as possible. Further, in order to increase the luminance of the white light emitting module, it is required to further improve the internal quantum efficiency of the wavelength converter. The internal quantum efficiency refers to the ratio of the number of photons emitted to the number of photons of excitation light absorbed by the wavelength converter. The difference between the number of absorbed photons and the number of emitted photons changes mainly to heat and does not contribute to light emission.

  The present invention has been made in consideration of such problems, and the internal quantum efficiency can be further improved while using a binder to ensure the adhesive strength of the phosphor layer. An object of the present invention is to provide a wavelength converter capable of improving luminance.

[1] A wavelength converter according to the present invention is a wavelength converter that converts the wavelength of excitation light to obtain a light emission color different from that of the excitation light. A phosphor layer formed on a surface, and the phosphor layer includes phosphor and glass as a binder, and has an internal quantum efficiency of 61% or more when irradiated with excitation light having a wavelength of 460 nm. It is characterized by that.

  That is, since the phosphor layer includes glass as a phosphor and a binder, the internal quantum efficiency can be further improved while using a binder to ensure the adhesive strength of the phosphor layer, For example, the luminance of the white light emitting module can be improved.

[2] In the present invention, the translucent substrate preferably has a thermal conductivity of 30 W / m · K or more. Heat generated in the phosphor layer can be dissipated through the translucent substrate, and the occurrence of temperature quenching can be suppressed.

[3] In the present invention, in the volume ratio of the phosphor constituting the phosphor layer and the glass, the composition of the phosphor is preferably 72 vol% or more and less than 100 vol%. The internal quantum efficiency can be increased to 80% or more, and the luminance can be improved.

[4] In the present invention, in the volume ratio of the phosphor constituting the phosphor layer and the glass, it is more preferable that the composition of the phosphor is 82 vol% or more and 90 vol% or less. The effect of improving the internal quantum efficiency becomes more remarkable.

[5] In the present invention, the ratio (particle size: film thickness) of the phosphor particle size (D50) to the phosphor layer thickness is preferably 1: 1 to 1: 3.5.

[6] In this case, it is preferable that the phosphor has a particle size (D50) of 10 to 35 μm. The effect of improving the internal quantum efficiency can be obtained.

[7] In the present invention, the glass preferably has a softening point of 340 to 880 ° C. Thereby, the effect which prevents the deterioration of the fluorescent substance characteristic in the case of glass softening can be acquired.

[8] In the present invention, the phosphor may have a maximum absorption wavelength at about 400 to 480 nm and a maximum emission wavelength at about 480 to 780 nm. Thereby, the wavelength of the short wavelength light can be converted into the long wavelength light, and for example, a part of the blue light can be converted into light of a different wavelength (for example, yellow light).

[9] In the present invention, it has one surface on which the excitation light is incident and the other surface on which the emission color is emitted, and the phosphor layer is disposed on the one surface side or the other surface side. May be. When the phosphor layer is arranged on one surface side, a part of the excitation light is converted into light having a different wavelength (for example, yellow light) by the phosphor layer and diffused on the light-transmitting substrate. . Since the excitation light that has passed through the phosphor layer is also diffused by the translucent substrate, the excitation light and the wavelength-converted light are mixed in the translucent substrate to become the light extraction side of the light-emitting substrate. The light is emitted from the surface as mixed color light (for example, white light). When the phosphor layer is disposed on the other surface side, the light diffused by the translucent substrate is homogenized and irradiated on the phosphor layer.

[10] In [9], a dichroic mirror may be disposed on the one surface side of the phosphor layer. In this case, the light directed toward one surface is reflected by the dichroic mirror and returned to the other surface, which contributes to white light emission and can further improve the luminance.

[11] In [9] or [10], an antireflection film may be disposed on at least one of the one surface side and the other surface side of the phosphor layer. Thereby, reflection of light at the interface is suppressed by the antireflection film, which contributes to improvement in luminance.

[12] In [9], a lens shape may be formed on the other surface side of the translucent substrate. Thereby, the mixed color light travels toward the lens shape, and in particular, the light diffused in the oblique direction beyond the critical angle can be extracted without being totally reflected by the lens shape, which contributes to the improvement of the luminance.

[13] In the present invention, the internal quantum efficiency may be 80.9% or more.

  According to the wavelength converter of the present invention, the internal quantum efficiency can be further improved while using a binder to ensure the adhesive strength of the phosphor layer. Therefore, by mounting the wavelength converter according to the present invention on a light emitting module using a light emitting element with high luminance, luminance reduction and color variation due to resin deterioration do not occur, and luminance due to temperature quenching of the phosphor. It is possible to obtain a light emitting module that does not deteriorate.

It is sectional drawing which shows the wavelength converter which concerns on this Embodiment. FIG. 2A is a cross-sectional view showing a wavelength converter according to a first modification, and FIG. 2B is an explanatory view showing a normal action when no reflective film is provided. FIG. 3A is a cross-sectional view showing a wavelength converter according to a second modification, and FIG. 3B is an explanatory view showing a normal action when an antireflection film is not provided. It is sectional drawing which shows the wavelength converter which concerns on a 3rd modification. It is sectional drawing which shows the wavelength converter which concerns on a 4th modification. It is sectional drawing which shows the wavelength converter which concerns on a 5th modification. It is sectional drawing which shows the wavelength converter which concerns on a 6th modification. It is sectional drawing which shows the wavelength converter which concerns on a 7th modification. FIG. 9A is an explanatory diagram showing a method for evaluating the total front transmittance using an integrating sphere in Examples 1 to 18, and FIG. 9B is an explanatory diagram showing a method for evaluating the linear transmittance similarly. In Examples 1-18, it is explanatory drawing which shows the evaluation method of the internal quantum efficiency using an integrating sphere. It is a graph which shows the change of the internal quantum efficiency with respect to the fluorescent substance composition based on Examples 1-8.

  Hereinafter, embodiments of the wavelength converter according to the present invention will be described with reference to FIGS. In addition, in this specification, "-" which shows a numerical range is used as the meaning containing the numerical value described before and behind that as a lower limit and an upper limit.

  As shown in FIG. 1, the wavelength converter 10 according to the present embodiment is a wavelength converter that converts the wavelength of the excitation light 12 from, for example, a light emitting diode to obtain an emission color different from that of the excitation light 12. And a phosphor layer 16 formed on one principal surface 14a of the translucent substrate 14. In particular, the phosphor layer 16 includes a phosphor (that is, phosphor particles) and glass as a binder. Examples of the excitation light 12 include excitation light from a blue light emitting diode or a blue semiconductor laser. Further, when viewed as a whole, the wavelength conversion body 10 has one surface 11a on which excitation light is incident and the other surface 11b on which emission color is emitted. In FIG. 1, the size of the phosphor layer 16 is shown smaller than the translucent substrate 14, but the present invention is not limited to this. The dimensions of these members are arbitrary, and the size of the phosphor layer 16 may be the same as or larger than that of the translucent substrate 14. The same applies to FIGS. 2A to 8.

  For example, an alumina substrate (translucent alumina substrate) having a thermal conductivity of 30 W / m · K or more is preferably used as the translucent substrate 14. By setting the thermal conductivity to 30 W / m · K or more, the heat generated in the phosphor layer 16 can be dissipated through the translucent substrate 14, and the occurrence of temperature quenching can be suppressed. Of course, if the thermal conductivity is 30 W / m · K or more, a sapphire substrate or an aluminum nitride substrate may be used in addition to the above-described alumina substrate. Further, the total front transmittance of the translucent substrate 14 is preferably 30% or more, and the linear transmittance is set to 65% or less in order to improve the light diffusibility in the translucent substrate 14. Is desirable.

  The molding method of the translucent substrate 14 is not particularly limited, and may be any method such as a doctor blade method, an extrusion method, a gel casting method, or the like. Particularly preferably, the translucent substrate 14 is manufactured using a gel cast method. In a preferred embodiment, a slurry containing a ceramic powder, a dispersion medium and a gelling agent is cast, and the slurry is gelled to obtain a molded body. The conductive substrate 14 is obtained (see JP 2001-335371 A).

  Particularly preferably, a raw material in which an auxiliary of 150 to 1000 ppm is added to high-purity alumina powder having a purity of 99.9% or more (preferably 99.95% or more) is used. Examples of such high-purity alumina powder include high-purity alumina powder manufactured by Daimei Chemical Industry Co., Ltd.

As the above-mentioned auxiliary agent, magnesium oxide (MgO) is preferable, but zirconium oxide (ZrO ₂ ), yttrium oxide (Y ₂ O ₃ ), lanthanum oxide (La ₂ O ₃ ), scandium oxide (Sc ₂ O ₃ ) are also included. It can be illustrated.

  The gel casting method includes the following methods.

(1) Along with inorganic powder, a prepolymer such as polyvinyl alcohol, epoxy resin, phenol resin or the like, which becomes a gelling agent, is dispersed in a dispersion medium together with a dispersant to prepare a slurry. The slurry is solidified by crosslinking and gelation.

(2) The slurry is solidified by chemically bonding an organic dispersion medium having a reactive functional group and a gelling agent. This method is the method described in Japanese Patent Application Laid-Open No. 2001-335371 of the present applicant.

  On the other hand, with respect to the phosphor layer 16, in the volume ratio of the phosphor and glass constituting the phosphor layer 16 (the volume of each component is obtained by dividing the weight of each component by the specific gravity of each component). The composition is preferably 72 vol% or more and less than 100 vol%. Accordingly, the internal quantum efficiency is improved while using a binder to ensure the adhesive strength of the phosphor layer 16 to the translucent substrate 14, and for example, white using the wavelength converter 10 according to the present embodiment. The luminance of the light emitting module can be improved. That is, by mounting the wavelength conversion body 10 according to the present embodiment on a light emitting module using a light emitting element with high luminance, luminance reduction and color variation due to resin degradation do not occur, and temperature quenching of the phosphor occurs. Thus, a light emitting module can be obtained that does not cause a decrease in luminance.

  Further, if the composition of the phosphor is 82 vol% or more and 90 vol% or less, the glass acts more effectively than the other cases, so that variation in luminance is further reduced, luminance is stabilized, and luminance is improved. Becomes prominent.

  Moreover, it is preferable that ratio (particle size: film thickness) of the particle size (D50) of the phosphor and the film thickness of the phosphor layer 16 is 1: 1 to 1: 3.5. In this case, the particle size (D50) of the phosphor is preferably 35 μm or less, more preferably 10 to 35 μm. When using a single phosphor, the particle size should be large.When mixing different types of phosphors, the particle size should be small compared to using a single phosphor to improve the mixing condition. It is desirable to do. Here, the particle size (D50) of the phosphor is 50% of the accumulated amount (integrated passage rate) from the small particle size side in the volume-based particle size distribution obtained by measurement by the laser diffraction / scattering particle size distribution measurement method. The particle diameter (D50).

  The method for providing the phosphor layer 16 is not particularly limited, and known methods such as dip coating and ink jet can be used in addition to screen printing.

  A method for producing the paste of the phosphor layer 16 is not particularly limited, and a known method such as a tri-roll mill can be used in addition to a self-revolving stirring and defoaming mixer. Also, the types of organic vehicles such as phosphors, paste resins and solvents are not particularly limited. For example, for phosphors, sialon (silicon-aluminum-oxygen-nitrogen) phosphors can be used in addition to YAG (yttrium-aluminum-garnet) phosphors. For vehicles, terpineol is used as a solvent. In addition, known materials such as polyvinyl acetal, etc., and known resins such as etosel, acrylic and butyral resins can be used as the resin for paste. When the phosphor is not an oxide, for example, a nitride or a mixture of oxide and nitride, the heat resistant temperature in the atmosphere is higher than when the phosphor is a simple oxide. May be low. In that case, it is necessary to set the baking temperature of the glass serving as the binder under conditions that consider the heat-resistant temperature of the phosphor.

  The glass contained in the phosphor layer 16 is preferably a glass having a softening point of 340 to 880 ° C. Furthermore, when chemical stability such as moisture resistance is desired, it is desirable to use a glass having a high softening point. For example, when the phosphor is a simple oxide or a mixture of oxides, a glass with a high softening point can be used, but for a phosphor containing a non-oxide phosphor with a low heat resistance temperature. When seeking chemical stability of glass, it is desirable to use glass with a high softening point, and shorten the temperature exposed to temperatures above its heat resistance temperature to minimize the total amount of heat received by the phosphor. It is preferable to use conditions.

  That is, since it is necessary to reduce the thermal history (which is approximately the same as holding temperature × holding time), (baking temperature−softening temperature) is 0 to 200 ° C., and (softening temperature−heat resistant temperature) is 0 to 200 ° C. Is desirable. The holding time at the firing temperature is preferably about 10 to 60 minutes if (baking temperature-heat resistant temperature) is 0 to 200 ° C, and about 0 to 10 minutes at 200 to 400 ° C. Further, it is desirable to increase the temperature rising rate and the temperature decreasing rate, and it is desirable to use a belt furnace in addition to a single furnace.

Here, when the composition of glass is exemplified, it is preferable to use a lead-based or bismuth-based material in order to soften at a low temperature. Further, when softening at 500 ° C. or higher, a glass having an alkali metal oxide content of 5 wt% or lower can be used. Specifically, ZnO—B ₂ O ₃ —SiO ₂ system, R ₂ O (R is an alkali metal, the same shall apply hereinafter) —PbO—SiO ₂ system, R ₂ O—CaO—PbO—SiO ₂ system, BaO—Al Examples thereof include ₂ O ₃ —B ₂ O ₃ —SiO ₂ system and B ₂ O ₃ —SiO ₂ system. The front transmittance of the glass is preferably 70% or more when the thickness is 0.5 mm.

  The phosphor layer 16 is preferably disposed on the side irradiated with the excitation light 12. As a result, a part of the excitation light 12 (for example, blue light) is converted into light having a different wavelength (for example, yellow light) by the phosphor layer 16 and diffused in the translucent substrate 14. Since the excitation light 12 that has passed through the phosphor layer 16 is also diffused by the translucent substrate 14, the excitation light 12 and the wavelength-converted light are mixed by the translucent substrate 14, and the translucent substrate. 14 is emitted as mixed color light 18 (for example, white light) from the other main surface 14b (surface on the light extraction side). Of course, the phosphor layer 16 may be disposed on the side opposite to the side irradiated with the excitation light 12.

  Here, a mode (modification) suitable for further improving the light emission luminance will be described with reference to FIGS. 2A to 8.

  As shown in FIG. 2A, the wavelength converter 10 a according to the first modification has a dichroic mirror (reflective film) 20 formed on the end surface 16 a on the one surface 11 a side of the phosphor layer 16. The dichroic mirror 20 is a kind of mirror that transmits light of a specific wavelength (for example, excitation light 12) and reflects light of other wavelengths (for example, light after wavelength conversion or mixed color light 18). It is formed by coating a thin film such as a multilayer film.

That is, the dichroic mirror 20 has a structure in which high refractive index layers and low refractive index layers are alternately stacked. Examples of the material for the high refractive index layer include TiO ₂ (refractive index = 2.2 to 2.5) and Ta ₂ O ₃ (refractive index = 2.0 to 2.3). Examples of the material include SiO ₂ (refractive index = 1.45 to 1.47) and MgF ₂ (refractive index = 1.38). The number of layers of the dichroic mirror 20 is 5 to 100 for each of the high refractive index layer and the low refractive index layer, and the film thickness is 50 to 500 nm per layer.

  Usually, for example, as shown in FIG. 2B, a part of the light after wavelength conversion by the phosphor layer 16 (including light reflected at the interface between the phosphor layer 16 and the translucent substrate 14) Since it goes to the light source side, it does not contribute as the mixed color light 18 (white light) forward. However, as shown in FIG. 2A, by providing the dichroic mirror 20 described above, the light 22 traveling toward the light source side is reflected by the dichroic mirror 20 and returned to the translucent substrate 14 side. This contributes to a further improvement in luminance.

  The dichroic mirror 20 may be formed on the surface of the phosphor layer 16 formed as described above by a method such as vapor deposition, but the surface of the phosphor layer 16 is preferably formed on a flat surface. Before firing the phosphor layer 16, the surface of the phosphor layer 16 may be flattened, or after firing the phosphor layer 16, by filling the surface of the phosphor layer 16 with a translucent substance, It may be made flat. In addition, it is desirable to appropriately perform a method such as polishing the surface of the phosphor layer 16 after firing or performing a heat treatment after polishing.

As shown in FIG. 3A, the wavelength converter 10 b according to the second modification has an antireflection film 24 on the other main surface 14 b (surface on the light extraction side) of the other surface 11 b of the light transmissive substrate 14. It is different in point. The antireflection film 24 is also called an AR coating (Anti Reflection Coating), and is a thin film that reduces reflection on the surface of the translucent substrate 14 by light interference. Examples of the material of the antireflection film 24 include TiO ₂ and SiO ₂ , and MgF ₂ and ZrO ₂ .

  Usually, for example, as shown in FIG. 3B, a part of white light generated by diffusion of light (excitation light 12 and light after wavelength conversion) in the translucent substrate 14 is the other main surface of the translucent substrate 14. Since it reflects in 14b and goes to the back (light source side) as the reflected light 26, it does not contribute as the mixed color light 18 (white light) to the front. However, by providing the antireflection film 24 on the other main surface 14b of the translucent substrate 14, most of the mixed-color light 18 is not reflected by the other main surface 14b of the translucent substrate 14, and the mixed-color light 18 forward is prevented. Will be emitted. This contributes to an improvement in luminance.

  As shown in FIG. 4, the wavelength converter 10 c according to the third modification has a lens shape 28 integrally formed on the other main surface 14 b (light extraction side surface) on the other surface 11 b side of the translucent substrate 14. It differs in the point provided. As a method of integrally providing the lens shape 28, the above-described gel casting method can be used.

  By providing the lens shape 28 integrally, the generated mixed color light 18 (white light) travels toward the lens shape 28, and in particular, the light diffused beyond the critical angle in the oblique direction is totally reflected by the lens shape 28. Therefore, it can contribute to the improvement of luminance.

  As shown in FIG. 5, the wavelength converter 10d according to the fourth modification has substantially the same configuration as the wavelength converter 10a according to the first modification described above, but one principal surface 14a of the translucent substrate 14. And the other main surface 14b are different in that an antireflection film 24 is formed. In this case, by providing the antireflection film 24 on the one main surface 14 a of the translucent substrate 14, most of the light after wavelength conversion by the phosphor layer 16 is the phosphor layer 16 and the translucent substrate 14. The light is not reflected at the interface with the light and proceeds into the translucent substrate 14. Further, the light traveling in the translucent substrate 14 is not reflected by the other main surface 14 b of the translucent substrate 14. As a result, it contributes to white light emission, and the luminance can be further improved. The antireflection film 24 may be formed on one of the one main surface 14a and the other main surface 14b of the translucent substrate 14.

  The wavelength converter 10e according to the fifth modification is different in that the phosphor layer 16 is disposed on the other surface 11b side of the translucent substrate 14, as shown in FIG. In this case, the light diffused by the translucent substrate 14 is homogenized and applied to the phosphor layer 16. Further, part of the diffused light (excitation light 12) is converted into light having a different wavelength (for example, yellow light) by the phosphor layer 16. The light diffused in the phosphor layer 16 (excitation light) and the light after wavelength conversion are mixed, and mixed color light (for example, white light) from the end surface 16b of the phosphor layer 16 (the end surface on the other surface 11b side). Will be emitted. In the wavelength converter 10e, the dichroic mirror 20 is disposed on the one surface 11a side of the phosphor layer 16. In the example of FIG. 6, the example which formed the dichroic mirror 20 in the other main surface 14b of the translucent board | substrate 14 is shown. Furthermore, the wavelength converter 10e has an antireflection film 24 formed on one main surface 14a of the translucent substrate 14.

  According to the wavelength converter 10e according to the fifth modification, the excitation light 12 is diffused into the phosphor layer 16 without being reflected by the one main surface 14a and the other main surface 14b of the translucent substrate 14. And proceed. Further, a part of the light after wavelength conversion by the phosphor layer 16 and a part of the mixed color light generated by the phosphor layer 16 are directed to the one surface 11a side. Since it is reflected by the dichroic mirror 20 formed on the main surface 14b and returned to the other surface 11b side, it contributes to white light emission, and the luminance can be further improved.

  As shown in FIG. 7, the wavelength converter 10f according to the sixth modification has substantially the same configuration as the wavelength converter 10e according to the fifth modification described above, but the other surface 11b side of the phosphor layer 16 is provided. This is different in that an antireflection film 24 is formed on the end face 16b. In this case, similarly to the fifth modification, the light (part of the light after wavelength conversion and part of the mixed color light) traveling toward the one surface 11a is reflected by the dichroic mirror 20 and is reflected on the phosphor layer. 16 is returned to the end face 16b side. In particular, in the sixth modification, the mixed color light generated in the phosphor layer 16 is emitted outward without being reflected by the end face 16b of the phosphor layer 16. Therefore, it contributes to white light emission, and the luminance can be further improved.

  As shown in FIG. 8, the wavelength converter 10g according to the seventh modification has substantially the same configuration as that of the wavelength converter 10f according to the sixth modification described above, but one principal surface 14a of the translucent substrate 14. The dichroic mirror 20 is formed, and the antireflection film 24 is formed on the other main surface 14 b of the translucent substrate 14. In this case, the excitation light 12 is diffused in the phosphor layer 16 without being reflected by the one main surface 14 a and the other main surface 14 b of the translucent substrate 14. Further, of the mixed color light generated in the phosphor layer 16, the mixed color light traveling toward the one surface 11 a is reflected by the dichroic mirror 20 formed on the one main surface 14 a of the translucent substrate 14 and is then reflected on the phosphor layer. Since it returns to the 16th side, it will contribute to white light emission, and the brightness | luminance can be improved further. The antireflection film 24 formed on the other main surface 14b of the translucent substrate 14 may be omitted.

  For Examples 1 to 18, optical characteristics (front total transmittance, linear transmittance, and internal quantum efficiency) were evaluated.

Example 1
The gel cast manufacturing method described in JP-A No. 2001-335371 is performed, the purity is 99.98%, the relative density by Archimedes method is 99.5% or more, the average crystal grain size is 25 μm, the outer dimension is 100 × 100 mm, the thickness is 1. A translucent alumina substrate having a thickness of 0.0 mm was obtained.

Specifically, 500 ppm of magnesium oxide powder was added to high-purity alumina powder having a purity of 99.99% or more, a BET surface area of 9 to 15 m ² / g, and a tap density of 0.9 to 1.0 g / cm ³ . . This raw material powder was molded by a gel cast method. 100 parts by weight of this powder, 40 parts by weight of a dispersion medium (dimethyl malonate), 8 parts by weight of a gelling agent (4,4'-diphenylmethane diisocyanate modified product), 0.1 to 0.3 parts by weight of a reaction catalyst (triethylamine) And a nonionic dispersant were mixed.

  At 20 ° C., the raw material powder and the dispersant were added and dispersed in a dispersion medium, then a gelling agent was added and dispersed, and finally a reaction catalyst was added to prepare a slurry. This slurry was poured into a mold and left to gel for 2 hours. The gelled molded body was taken out from the mold and dried at 60 to 100 ° C. Next, the compact was degreased at 1100 ° C. for 2 hours and fired in a hydrogen atmosphere.

A self-revolving stirring and defoaming mixer was used to mix and paste the phosphor and glass. Phosphor powder (particle size D50 = 20 μm, Y ₃ Al ₅ O ₁₃ : Ce ³⁺ ), glass frit (softening point 500 ° C.), and a predetermined amount of vehicle were uniformly mixed and kneaded to obtain the desired paste. The raw material ratio of the phosphor and glass was adjusted so that the volume ratio excluding the resin component (phosphor: glass) was 14:86. Terpineol was used as a vehicle component, and the amount added was adjusted so that the viscosity of the prepared phosphor glass paste was 600 to 800 Pa · s.

  The prepared paste was printed on a translucent alumina substrate by screen printing. This was dried at 60-100 degreeC, and the wavelength converter which concerns on Example 1 was obtained by baking at 600 degreeC. The printing conditions were adjusted so that the fired film thickness was 35 μm.

(Example 2)
A wavelength converter according to Example 2 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 40:60. The printing conditions were adjusted so that the fired film thickness was 35 μm.

Example 3
A wavelength converter according to Example 3 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 72:28. The printing conditions were adjusted so that the fired film thickness was 35 μm.

Example 4
A wavelength converter according to Example 4 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 82:18. The printing conditions were adjusted so that the fired film thickness was 35 μm.

(Example 5)
A wavelength converter according to Example 5 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 86:14. The printing conditions were adjusted so that the fired film thickness was 35 μm.

(Example 6)
A wavelength converter according to Example 6 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 90:10. The printing conditions were adjusted so that the fired film thickness was 35 μm.

(Example 7)
A wavelength converter according to Example 7 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was set to 97: 3. The printing conditions were adjusted so that the fired film thickness was 35 μm.

(Example 8)
A wavelength converter according to Example 8 was obtained in the same manner as in Example 1 except that the volume ratio of the phosphor to glass (phosphor: glass) was 99: 1. The printing conditions were adjusted so that the fired film thickness was 35 μm.

Example 9
A wavelength converter according to Example 9 was obtained in the same manner as in Example 5 except that the printing conditions were adjusted so that the fired film thickness was 20 μm.

(Example 10)
A wavelength converter according to Example 10 was obtained in the same manner as in Example 5 except that the printing conditions were adjusted so that the fired film thickness was 70 μm.

(Example 11)
A wavelength converter according to Example 11 was obtained in the same manner as Example 5 except that the printing conditions were adjusted so that the fired film thickness was 120 μm.

(Example 12)
A wavelength converter according to Example 12 was obtained in the same manner as in Example 5 except that a phosphor powder having a phosphor particle size D50 of 10 μm was used.

(Example 13)
A wavelength converter according to Example 13 was obtained in the same manner as in Example 5 except that the phosphor powder having a phosphor particle size D50 of 35 μm was used.

(Example 14)
A wavelength converter according to Example 14 was obtained in the same manner as Example 5 except that frit glass having a softening point of 800 ° C. was used.

(Example 15)
A wavelength converter according to Example 15 was obtained in the same manner as in Example 5 except that the phosphor powder having a phosphor particle size D50 of 40 μm was used and the printing conditions were adjusted so that the fired film thickness was 90 μm.

(Example 16)
A wavelength converter according to Example 16 was obtained in the same manner as Example 5 except that phosphor powder having a phosphor particle size D50 of 5 μm was used and the printing conditions were adjusted so that the fired film thickness was 25 μm.

(Example 17)
A wavelength converter according to Example 17 was obtained in the same manner as Example 5 except that frit glass having a glass softening point of 300 ° C. was used.

(Example 18)
A wavelength converter according to Example 18 was obtained in the same manner as in Example 5 except that frit glass having a glass softening point of 900 ° C. was used.

<Evaluation of optical properties>
(Front total transmittance)
The front total transmittance of the obtained Examples 1 to 18 was measured using a spectrophotometer (manufactured by Hitachi High-Tech, U-4100) having an integrating sphere having an entrance and a detector, as shown in FIG. 9A. did. The measurement samples (Examples 1 to 18) were cut into dimensions of 10 mm (length) × 10 mm (width) × 0.5 mm (thickness).

  Monochromatic light having a wavelength of 555 nm is incident on the surface of the measurement sample fixed to the entrance of the integrating sphere from the light source, and radiated light emitted from the back side toward the integrating sphere through the measurement sample is detected by the detector. .

The total front transmittance is a ratio of light intensity (I) when the visible light passing through the measurement sample is collected by an integrating sphere and light intensity (I ₀ ) when measurement is performed without fixing the measurement sample (= I / I ₀ ).

  The total front transmittances of Examples 1 to 18 were all 30% or more.

(Linear transmittance)
The linear transmittances of Examples 1 to 18 were measured using a spectrophotometer (manufactured by Hitachi High-Tech, U-4100) having an integrating sphere having an entrance and a detector, as shown in FIG. 9B. The measurement samples (Examples 1 to 18) were cut into dimensions of 10 mm (length) × 10 mm (width) × 0.5 mm (thickness).

  Then, the light source and the integrating sphere were arranged with the light source and the integrating sphere entrance facing each other, and a slit plate having one through hole was installed between the light source and the integrating sphere. The measurement sample was fixed so as to block the through hole on the surface of the slit plate facing the integrating sphere. The measurement wavelength of the spectrophotometer is 175 to 2600 nm, and a light source that emits light having a wavelength of 200 to 1000 nm was used as the light source. Regarding the dimensional relationship, the diameter of the entrance of the integrating sphere is about 9 mm, the diameter of the through hole of the slit plate is 2 mm, and the distance La from the measurement sample to the entrance of the integrating sphere is about 90 mm.

The linear transmittance is a ratio of light intensity (I) when the visible light passing through the measurement sample is collected with an integrating sphere and light intensity (I ₀ ) when measurement is performed without fixing the measurement sample (= I / I ₀ ).

  The linear transmittances of Examples 1 to 18 were all 65% or less.

(Internal quantum efficiency)
The wavelength converters according to Examples 1 to 18 were cut into approximately 10 mm × 10 mm, and the internal quantum efficiency was measured using a fluorescence spectrophotometer (manufactured by JASCO, FP-8300) and a φ60 mm integrating sphere. In the measurement of optical characteristics, excitation light was irradiated toward the phosphor layer.

As shown in FIG. 10, the internal quantum efficiency measurement of the wavelength converter is performed by holding the measurement sample (Examples 1 to 18) on the Spectralon standard reflector, and in this state, directly measuring the measurement sample from the excitation port of the integrating sphere. The sample was placed in an integrating sphere and the fluorescence spectrum of the sample was measured. The excitation light was 460 nm. For the internal quantum efficiency, the excitation light intensity I ₀ (wavelength 460 ± 20 nm) is obtained from the excitation light spectrum when no measurement sample is installed, and the excitation light intensity I ₁ (wavelength 460 nm ± 20 nm) that is not absorbed from the fluorescence spectrum of the sample. Sample emission intensity E ₁ (480 to 780 nm) was obtained and calculated from the following equation (1).
Internal quantum efficiency = E ₁ / (I ₀ −I ₁ ) (1)

  The evaluation results of Examples 1 to 18 are shown in Table 1. Moreover, the change of the internal quantum efficiency with respect to the fluorescent substance composition of Examples 1-8 is shown in FIG.

  When attention is paid to Examples 1 to 8, it can be seen that when the phosphor composition is 72 to 99 vol% (Examples 3 to 8), the internal quantum efficiency is as high as 80% or more (see curve L in FIG. 11). In particular, in the case of the phosphor composition of 86 to 90 vol% (Examples 5 and 6), this effect is particularly remarkable. The reason why the internal quantum efficiency of the phosphor is improved by setting the composition ratio of the phosphor and glass within a specific range is unclear, but it is possible that the transparent glass emits light from the phosphor. It functions as a path for guiding light to the outside of the wavelength converter. Moreover, when a fluorescent substance composition is less than 72 vol% (Examples 1 and 2), it turns out that internal quantum efficiency is falling. This is considered to be because the influence of the decrease in internal quantum efficiency due to light absorption in the glass becomes more prominent as the glass composition increases.

  When attention is paid to Examples 5, 9 to 11 and 16, the above effect (the effect of improving the internal quantum efficiency) is recognized in the case of phosphor particle size D50: film thickness after firing = 1: 1 to 1: 3.5. It is done. On the other hand, in the case of phosphor particle size D50: film thickness after firing = 1: 6 (Example 11) or 1: 5 (Example 16), the internal quantum efficiency is lowered. This is because, even if glass functions as a light guide path in the phosphor layer, if the film thickness is thicker (6 times or 5 times) than the phosphor particle size, absorption by the glass and self absorption of the phosphor There is a possibility that the effect of loss due to Here, self-absorption refers to a phenomenon in which light emission of the phosphor is absorbed again by the phosphor.

  When attention is paid to Examples 5, 12, 13, and 15, it is considered that the above effect is observed in a phosphor having a phosphor particle size D50 = 10 to 35 μm. Further, the phosphor particle size is preferably 35 μm or less because if the particle size is larger than 35 μm, the formability of the phosphor layer is deteriorated or the light emission distribution of the phosphor is deteriorated.

  Paying attention to Examples 5, 14, 17, and 18, it is considered that the above effect is observed when the softening point of the glass frit is 340 to 880 ° C. In particular, in the case of a glass having a low softening point, it tends to be colored, which is not preferable for optical parts, and in a glass having a high softening point, thermal damage to the phosphor particles when the phosphor layer is fired is reduced. In any case, the softening point described above is desirable to increase the internal quantum efficiency.

  Note that the wavelength converter according to the present invention is not limited to the above-described embodiment, and can of course have various configurations without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 10, 10a-10g ... Wavelength converter 12 ... Excitation light 14 ... Translucent substrate 14a ... One main surface 16 ... Phosphor layer 18 ... Mixed color light 20 ... Reflective film 22 ... Light 24 ... Antireflection film 26 ... Reflected light 28 ... Lens shape

Claims (13)

In the wavelength converter that converts the wavelength of the excitation light to obtain an emission color different from that of the excitation light,
A translucent substrate;
A phosphor layer formed on one main surface of the translucent substrate,
The phosphor layer includes a phosphor and glass as a binder,
A wavelength converter having an internal quantum efficiency of 61% or more when irradiated with excitation light having a wavelength of 460 nm. The wavelength converter according to claim 1,
The translucent substrate has a thermal conductivity of 30 W / m · K or more. In the wavelength converter of Claim 1 or 2,
The wavelength converter, wherein a composition of the phosphor is not less than 72 vol% and less than 100 vol% in a volume ratio of the phosphor constituting the phosphor layer and the glass. In the wavelength converter of Claim 1 or 2,
The wavelength converter, wherein a composition of the phosphor is not less than 82 vol% and not more than 90 vol% in a volume ratio of the phosphor constituting the phosphor layer and the glass. In the wavelength converter of any one of Claims 1-4,
A wavelength converter having a ratio (particle size: film thickness) of the particle size (D50) of the phosphor and the film thickness of the phosphor layer of 1: 1 to 1: 3.5. The wavelength converter according to claim 5, wherein
A wavelength converter having a particle size (D50) of the phosphor of 10 to 35 μm. In the wavelength converter of any one of Claims 1-6,
The wavelength conversion body characterized by the softening point of the said glass being 340-880 degreeC. In the wavelength converter of any one of Claims 1-7,
The wavelength converter, wherein the phosphor has a maximum absorption wavelength at about 400 to 480 nm and a maximum emission wavelength at about 480 to 780 nm. In the wavelength converter of any one of Claims 1-8,
Having one surface on which the excitation light is incident and the other surface from which the emission color is emitted;
The wavelength conversion body, wherein the phosphor layer is disposed on the one surface side or the other surface side. The wavelength converter according to claim 9,
A wavelength converter, wherein a dichroic mirror is disposed on the one surface side of the phosphor layer. The wavelength converter according to claim 9 or 10,
A wavelength converter, wherein an antireflection film is disposed on at least one of the one surface side and the other surface side of the phosphor layer. The wavelength converter according to claim 9,
A wavelength converter, wherein a lens shape is formed on the other surface side of the translucent substrate. In the wavelength converter of any one of Claims 1-12,
The wavelength converter having the internal quantum efficiency of 80.9% or more.

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