JP2014157856A - Optical conversion member, and illumination light source having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical conversion member which includes glass and an inorganic fluorescent material capable of converting excitation light of a light source, and has an improved light extraction efficiency.SOLUTION: An optical conversion member of the invention comprises an inorganic fluorescent material and glass. The glass has a refraction index nd of 1.7-2.8. The optical conversion member has a surface roughness Ra of 0.75 μm or larger as to one or more faces thereof.

Description

  The present invention relates to a light conversion member in which an inorganic phosphor used as a light conversion member for LED light or the like is dispersed.

  An LED (Light Emitting Diode) is used as an illumination light source of minute electric power, and is expected to be developed for various illumination applications. Among LEDs, a white LED obtains white light by synthesizing blue light emitted from a blue LED element and yellow light obtained by converting a part of the blue light into yellow with an inorganic phosphor.

  As a member for converting the wavelength of incident light, there is known a light conversion member (hereinafter also simply referred to as a light conversion member) having a configuration in which an inorganic phosphor is dispersed in glass (for example, Patent Document 1). . The light conversion member has high transmittance, and can efficiently release heat generated from the element to the outside. Moreover, the damage of the member by light and a heat | fever is also low, and long-term reliability is acquired.

  Patent Document 1 describes a bulk phosphor having a surface roughness Ra of 0.05 to 3 μm, which is a light conversion member used for a white light emitting device and is composed of only an inorganic material. However, a light conversion member containing an inorganic phosphor and uncrystallized glass is not described.

  Patent Document 2 describes a light conversion member formed by dispersing an inorganic phosphor in glass. Specifically, a light conversion member having a Vickers hardness difference of 300 or more between an inorganic phosphor and glass and a surface roughness Ra of 0.1 μm or less is described.

JP 2007-161944 A JP 2011-122067 A

  However, in the conventional light conversion member, the light extraction efficiency of the light source cannot be sufficiently increased. An object of the present invention is to provide a light conversion member containing glass and an inorganic phosphor that converts excitation light of a light source, and having improved light extraction efficiency.

  The present inventors have found that the light conversion member reduces the light extraction efficiency of the light source, and that the cause is due to the reflection on the light incident surface and the light exit surface, thereby completing the present invention. It came to do. As a result of intensive studies by the present inventors, in order to reduce the amount of light reflected at the interface where light enters the light conversion member, the difference in refractive index between the light source and the light conversion member is reduced, and the light conversion member In order to reduce the amount of light reflected at the interface from which light is emitted, the inventors have found that the light conversion member extraction efficiency can be increased by adjusting the surface roughness to an appropriate range.

  That is, the light conversion member of the present invention has a light conversion member containing an inorganic phosphor and glass, the refractive index nd of the glass is 1.7 to 2.8, and one or more surfaces of the light conversion member The surface roughness Ra is 0.75 μm or more.

  The light conversion member of the present invention can suppress total reflection at the interface between the light source and the light conversion member and the interface between the light conversion member and the atmosphere, and can improve the extraction efficiency of light emitted from the light source. Moreover, an illumination light source with high light extraction efficiency can be obtained.

(Light conversion member)
The light conversion member of the present invention (hereinafter, this light conversion member) will be described. If this light conversion member is used, a part of the light emitted from the light source is transmitted, the wavelength of the remaining light is converted into light having a wavelength different from that of incident light (hereinafter also referred to as excitation light), and the transmitted light And the light whose wavelength has been converted can be converted into the desired color of the light from the light source. The light conversion member is preferably used as a light conversion member for converting a blue light source into white. Moreover, it is more preferable to use a semiconductor light emitting element as a light source.

  The light conversion member contains glass and an inorganic phosphor. As long as the function as the light conversion member described above is exhibited, the distribution of the inorganic phosphor is not particularly limited as long as it is contained in the glass. That is, the inorganic phosphor may be uniformly dispersed in the glass or may be unevenly distributed in a part of the glass. From the viewpoint of production efficiency, the inorganic phosphor is preferably dispersed in the glass.

  If the light conversion member can coat | cover the whole light emission surface of a light source, the magnitude | size and plane shape will not be specifically limited. Since the semiconductor light emitting element used as the light source is rectangular or disk-shaped, the light conversion member is preferably rectangular or disk-shaped. The light conversion member is preferably plate-shaped from the viewpoint of ease of processing, that is, efficiency in production.

  In the present light conversion member, the surface roughness Ra of one or more surfaces is 0.75 μm or more. If the surface roughness Ra of at least one surface is in the above-described range, the surface roughness Ra of the other surface is not particularly limited. The surface having a surface roughness Ra of 0.75 μm or more is preferably a surface that emits light from the light conversion member (hereinafter referred to as a first surface).

  If the surface roughness Ra of the first surface is 0.75 μm or more, total reflection at the interface between the light conversion member and the atmosphere can be effectively suppressed. From the viewpoint of suppressing total reflection, the surface roughness Ra of the first surface is preferably 0.8 μm or more, and more preferably 0.9 μm or more. On the other hand, in order to reduce light scattering on the surface, the surface Ra of the first surface is preferably 10 μm or less, more preferably 5 μm or less, and even more preferably 3 μm or less.

  If the surface roughness Ra of the first surface is 0.75 μm or more, the surface roughness Ra of the surface on which light is incident on the light conversion member (hereinafter referred to as the second surface) is not particularly limited. If the surface Ra of the second surface of the light conversion member is low, it is preferable because scattering of light incident on the light conversion member on the second surface can be suppressed and the light emission efficiency can be increased. The surface Ra of the second surface is preferably 5 μm or less, and more preferably 3 μm or less.

  The lower limit value of the surface Ra of the second surface is determined based on the viewpoint of increasing the total reflection angle on the second surface and suppressing light reduction due to total reflection at the different refractive index interface.

  When the refractive index of the light source is nd1 and the refractive index of the light conversion member is nd2, when nd1 <nd2 or nd1 ≧ nd2 and nd2 / nd1 is 0.866 or more, the total reflection angle is 60 ° or more. And reduction of light due to total reflection can be reduced to 50% or less. In this case, the surface Ra of the second surface is preferably 0.02 μm or more, and more preferably 0.05 μm or more.

  On the other hand, when nd1 ≧ nd2 and nd2 / nd1 is less than 0.866, the surface Ra of the second surface is preferably 0.8 μm or more, and more preferably 0.9 μm or more. If the surface Ra of the second surface is within such a range, it is preferable because reflection of incident light can be suppressed.

  Note that when nd1 ≧ nd2, the reduction (unit:%) of light due to total reflection at the interface of different refractive indices is a value calculated by the following equation (1).

  In the present specification, the surface Ra refers to a value measured according to JIS B0601: 2001, for example, using a surface roughness / contour measuring instrument (trade name: Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd.) Drive length 2.5 mm, drive speed 0.2 mm / sec. Can be measured under the following conditions.

  The thickness of the light conversion member is preferably 50 to 300 μm. If the thickness is in the above-described range, it effectively functions as a light conversion member, the transmittance can be increased, and the mechanical strength of the light conversion member can be secured. The thickness of the light conversion member is more preferably 100 to 200 μm, and further preferably 120 to 180 μm. The thickness of the light conversion member can be measured using, for example, a micrometer.

  The total light transmittance of the light conversion member of the present invention is preferably 75% or more. A higher transmittance is preferable because the light extraction efficiency of the light source can be increased. The total light transmittance is preferably 80% or more, and more preferably 85% or more. In the present specification, the total light transmittance refers to a value measured in accordance with JIS K 7136.

  The haze of the light conversion member of the present invention is preferably 70 to 95%. If the haze is in this range, scattering in the light conversion member is reduced, and the light extraction efficiency is increased. The haze is more preferably 80 to 95%, further preferably 85 to 95%. In the present specification, the haze refers to a value measured according to JIS K 7136.

  The light extraction efficiency of the light conversion member of the present invention is evaluated by quantum conversion efficiency (QE, unit:%). The quantum conversion efficiency is preferably 90% or more, more preferably 91% or more, and further preferably 92% or more.

In the present specification, the quantum conversion efficiency (QE) is expressed as a ratio between the number of photons (N _abs ) of excitation light irradiated from the second surface and the number of photons (N _f ) emitted from the first surface. And the value calculated by the following equation (2). The number of photons is a value measured by the integrating sphere method.

  The content ratio of the inorganic phosphor and glass in the light conversion member is not particularly limited as long as it can function as the above-described light conversion member. The content ratio is preferably inorganic phosphor: glass = 1: 99 to 40:60 in a volume ratio. It is preferable to contain the inorganic phosphor at such a ratio because the light color of the light source can be converted into a desired color and the transmittance of the light conversion member can be increased.

  The light conversion member is preferably made of a mixture of glass powder and inorganic phosphor, or a sintered body obtained by firing a paste obtained by kneading the mixture, resin and organic solvent. More preferably, the light conversion member is made of a sintered body obtained by processing the paste into a green sheet and firing it.

  When the light conversion member is manufactured by firing the above-described mixture, the volume ratio of the glass and the inorganic phosphor content in the light conversion member and the volume ratio of the glass powder and the inorganic phosphor are small. preferable. The smaller the change in the volume ratio, the more preferable is the deactivation of the inorganic phosphor in the firing step. Therefore, the content ratio between the glass powder and the inorganic phosphor is preferably 1:99 to 40:60.

  If the inorganic phosphor is contained at 1% or more and the glass powder is contained at 99% or less, the quantum conversion yield can be increased, and light of a desired color can be obtained. The volume fraction of the inorganic phosphor is more preferably 5% or more, further preferably 7% or more, and particularly preferably 10% or more. The volume fraction of the glass powder is more preferably 95% or less, still more preferably 93% or less, and particularly preferably 90% or less.

  If the volume fraction of the inorganic phosphor is more than 40% and the volume fraction of the glass powder is less than 60%, the sinterability of the mixture of the inorganic phosphor and the glass powder is impaired, and the transmittance of the light conversion member is low. There is a risk. Moreover, there is a possibility that light of a desired color cannot be obtained due to an increase in converted fluorescent light. The volume fraction of the inorganic phosphor is more preferably 35% or less, still more preferably 30% or less, and particularly preferably 25% or less. The volume fraction of the glass powder is more preferably 65% or more, further preferably 70% or more, and particularly preferably 75% or more.

(Glass)
The glass contained in the light conversion member has a refractive index nd of 1.7 to 2.8. Usually, an LED is used as a light source of a light emitting element in which a light conversion member is used. As the substrate of the LED, a sapphire substrate (nd: 1.77), a gallium nitride substrate (nd: 2.39), a silicon carbide substrate (nd: 2.65), or a zinc oxide substrate (nd: 2.00) is used. Is done. When the light conversion member is placed in contact with the light source, the lower the refractive index difference from the light source, the more the total reflection at the interface can be suppressed. The refractive index nd of the glass is preferably 1.7 to 2.6, and more preferably 1.7 to 2.4.

The glass is not particularly limited as long as it has a desired refractive index. Examples of the glass include B ₂ O ₃ system, SiO ₂ system, P ₂ O ₅ system, and TeO ₂ system.

Moreover, it is preferable that the softening point of glass is low from a viewpoint of the manufacturing efficiency of a light conversion member. Therefore, B ₂ O ₃ -based or SiO ₂ -based glass is preferable, B ₂ O ₃ -based glass is more preferable, and Bi ₂ O ₃ -B ₂ O ₃ -based glass is more preferable. The softening point of the glass is more preferably 850 ° C. or less, and further preferably 600 ° C. or less.

Examples of the Bi ₂ O ₃ —B ₂ O ₃ based glass include, for example, 3% to 30% Bi ₂ O ₃ , 10% to 50% B ₂ O ₃ , and 0% to 45% ZnO in terms of mol% based on oxide. The glass to contain is more preferable. _{Bi 2 O 3 3~30%, B} 2 O 3 10~50%, ZnO 0~45%, SiO 2 5~35%, BaO 0~20%, MnO 2 0~1%, CeO 2 0~1% The glass containing is more preferable.

(Inorganic phosphor)
The inorganic phosphor contained in the light conversion member is not particularly limited as long as it emits fluorescence having a wavelength different from that of the excitation light upon receiving the excitation light. The inorganic phosphor is preferably at least one selected from the group consisting of oxides, nitrides, oxynitrides, sulfides, oxysulfides, rare earth sulfides, aluminate chlorides, and halophosphates. The inorganic phosphor is more preferably an oxide or aluminate chloride. As oxides or aluminate chlorides, garnet crystals are more preferred because of their excellent water resistance and heat resistance. As the garnet-based crystal, a complex oxide of yttrium and aluminum (hereinafter also referred to as YAG in the present specification) is particularly preferable. Two or more inorganic phosphors may be used, or only one of them may be used.

  The inorganic phosphor preferably has an emission peak at a wavelength of 380 to 780 nm which is a visible light region. In particular, those having emission peaks in blue (wavelength 440 to 480 nm), green (wavelength 500 to 540 nm), yellow (wavelength 540 to 595 nm), and red (wavelength 600 to 700 nm) are more preferable.

As an inorganic phosphor that emits blue light when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm, Sr ₅ (PO ₄ ) ₃ Cl: Eu ²⁺ , (Sr, Ba) MgAl ₁₀ O ₁₇ : Eu ²⁺ Or (Sr, Ba) ₃ MgSi ₂ O ₈ : Eu ²⁺ .

Inorganic phosphors that emit green fluorescence when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm include SrAl ₂ O ₄ : Eu ²⁺ , SrGa ₂ S ₄ : Eu ²⁺ , SrBaSiO ₄ : Eu ²⁺ , CdS: In, CaS: Ce ³⁺ , Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ²⁺ , Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce ³⁺ , SrSiO _n : Eu ²⁺ , ZnS: Al ³⁺ , Cu ⁺ , CaS: Sn ²⁺ , CaS: Sn ²⁺ , F, CaSO ₄ : Ce ³⁺ , Mn ²⁺ , LiAlO ₂ : Mn ²⁺ , BaMgAl ₁₀ O ₁₇ : Eu ²⁺ , Mn ²⁺ , ZnS: Cu ⁺ , Cl ⁻ , Ca ₃ WO ₆ : U, Ca ₃ SiO ₄ Cl ₂ : Eu ²⁺ , Sr _0.2 Ba _0.7 Cl _1.1 Al ₂ O _3.45 : Ce ³⁺ , M n ²⁺ , Ba ₂ MgSi ₂ O ₇ : Eu ²⁺ , Ba ₂ SiO ₄ : Eu ²⁺ , Ba ₂ Li ₂ Si ₂ O ₇ : Eu ²⁺ , ZnO: S, ZnO: Zn, Ca ₂ Ba ₃ (PO ₄ ) ₃ Examples thereof include Cl: Eu ²⁺ , BaAl ₂ O ₄ : Eu ^{2+, and the} like.

As inorganic phosphors that emit green fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm, SrAl ₂ O ₄ : Eu ²⁺ , SrGa ₂ S ₄ : Eu ²⁺ , SrBaSiO ₄ : Eu ²⁺ , CdS: In, CaS : Ce ³⁺ , Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ²⁺ , Ca ₃ Sc ₂ Si ₃ O ₁₂ : Ce ³⁺ , or SrSiO _n : Eu ²⁺ .

Inorganic phosphors that emit yellow fluorescence when irradiated with ultraviolet to near ultraviolet excitation light having a wavelength of 300 to 440 nm include ZnS: Eu ²⁺ , Ba ₅ (PO ₄ ) ₃ Cl: U, Sr ₃ WO ₆ : U, CaGa ₂ S ₄ : Eu ²⁺ , SrSO ₄ : Eu ²⁺ , Mn ²⁺ , ZnS: P, ZnS: P ³⁻ , Cl ⁻ , ZnS: Mn ^{2+, and the} like.

As an inorganic phosphor that emits yellow fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm, Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ²⁺ , Ba ₅ (PO ₄ ) ₃ Cl: U, or CaGa ₂ S ₄ : Eu ^{2+ and the} like.

As inorganic phosphors that emit red fluorescence when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm, CaS: Yb ²⁺ , Cl, Gd ₃ Ga ₄ O ₁₂ : Cr ³⁺ , CaGa ₂ S ₄ : Mn ²⁺ Na (Mg, Mn) ₂ LiSi ₄ O ₁₀ F ₂ : Mn, ZnS: Sn ²⁺ , Y ₃ Al ₅ O ₁₂ : Cr ³⁺ , SrB ₈ O ₁₃ : Sm ²⁺ , MgSr ₃ Si ₂ O ₈ : Eu ²⁺ , Mn ²⁺ , α-SrO · 3B ₂ O ₃ : Sm ²⁺ , ZnS—CdS, ZnSe: Cu ⁺ , Cl, ZnGa ₂ S ₄ : Mn ²⁺ , ZnO: Bi ³⁺ , BaS: Au, K, ZnS: Pb ²⁺ , ZnS: Sn ²⁺ , Li ⁺ , ZnS: Pb, Cu, CaTiO ₃ : Pr ³⁺ , CaTiO ₃ : Eu ³⁺ , Y ₂ O ₃ : Eu ³⁺ , (Y, Gd) ₂ O ₃ : Eu ³⁺ , CaS: Pb ²⁺ , Mn ²⁺ , YPO ₄ : Eu ³⁺ , Ca ₂ MgSi ₂ O ₇ : Eu ²⁺ , Mn ²⁺ , Y (P, V) O ₄ : Eu ³⁺ , Y ₂ O ₂ S: Eu ³⁺ , SrAl ₄ O ₇ : Eu ³⁺ , CaYAlO ₄ : Eu ³⁺ , LaO ₂ S: Eu ³⁺ , LiW ₂ O ₈ : Eu ³⁺ , Sm ³⁺ , (Sr, Ca, Ba, Mg) ₁₀ ( PO ₄ ) ₆ Cl ₂ : Eu ²⁺ , Mn ²⁺ , Ba ₃ MgSi ₂ O ₈ : Eu ²⁺ , Mn ^{2+ and the} like.

Examples of inorganic phosphors that emit red fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm include ZnS: Mn ²⁺ , Te ²⁺ , Mg ₂ TiO ₄ : Mn ⁴⁺ , K ₂ SiF ₆ : Mn ⁴⁺ , SrS: Eu. ²⁺ , CaS: Eu ²⁺ , Na _1.23 K _0.42 Eu _0.12 TiSi ₄ O ₁₁ , Na _1.23 K _0.42 Eu _0.12 TiSi ₅ O ₁₃ : Eu ³⁺ , CdS: In, Te, CaAlSiN ₃ : Eu ²⁺ , CaSiN ₃ : Eu ²⁺ , (Ca, Sr) ₂ Si ₅ N ₈ : Eu ²⁺ , or Eu ₂ W ₂ O _7, (Sr _1-x Eu _x ) ₂ (Si _1-y Al _y ) ₅ (ON) ₈ or the like.

The average particle diameter (hereinafter abbreviated as the average particle diameter) D ₅₀ of the inorganic phosphor is preferably 20 μm or less. If desired size D ₅₀ of the inorganic phosphor, be uniformly dispersed in the light conversion member, it can improve the conversion efficiency of light. D _{50 of the} inorganic phosphor is more preferably 15 μm or less, and further preferably 10 μm or less. On the other hand, from the viewpoint of production efficiency, the average particle diameter D ₅₀ of the inorganic phosphor is preferably at least 3 [mu] m, more preferably not less than 5 [mu] m.

In the present specification, the average particle diameter D ₅₀ is a value calculated by a laser diffraction type particle size distribution measurement.

(Method for producing light conversion member)
In the present invention, the production method is not particularly limited as long as the light conversion member has the above-described characteristics. For example, as a method for producing a light conversion member of the present invention, a light conversion member having a specific surface Ra can be efficiently produced by polishing the surface of glass containing an inorganic phosphor. If the said glass is plate shape, since grinding | polishing can be made uniform over the whole surface, it is preferable.

  The polishing method in the polishing step is not particularly limited as long as the light conversion member has a desired surface Ra. Specific examples include blasting, fixed abrasive surface polishing, or free abrasive surface polishing. From the viewpoint of controlling the roughness while suppressing cracks and the like, polishing by free abrasive flat surface polishing is more preferable. Note that the polishing step is unnecessary if the necessary surface Ra can be obtained.

  The glass is preferably formed by sintering glass powder having a desired composition or desired characteristics and an inorganic phosphor. Such a method is preferable because the shape, size, thickness, or volume ratio of the glass and the inorganic phosphor can be easily controlled. Moreover, it is preferable to further have the process of mixing an inorganic fluorescent substance and glass powder, the process of preforming a mixture, and the process of baking the preformed thing.

The glass powder is produced by pulverizing and classifying the desired glass. The average particle diameter _{D 50} of the glass powder is preferably 2.0μm or less. D ₅₀ is 2.0μm or less, the inorganic phosphor and glass powder be uniformly mixed, the dispersion state of the inorganic phosphor in a light conversion member after sintering can be improved. Glass powder having an average particle diameter _{D 50} of the following more preferably 1.5 [mu] m, more preferably not more than 1.4 [mu] m.

  As for content of an inorganic fluorescent substance and glass powder, it is more preferable that an inorganic fluorescent substance is 1 to 40% and glass powder is 60 to 99% by a volume fraction. The volume fraction of the inorganic phosphor is more preferably 5% or more, further preferably 7% or more, and particularly preferably 10% or more. The volume fraction of the inorganic phosphor is more preferably 35% or less, still more preferably 30% or less, and particularly preferably 25% or less. The volume fraction of the glass powder is more preferably 95% or less, still more preferably 93% or less, and particularly preferably 90% or less. The volume fraction of the glass powder is more preferably 65% or more, further preferably 70% or more, and particularly preferably 75% or more.

  As long as a desired shape can be imparted to the preforming step, the method is not limited. Specific examples of the preforming method include a press molding method, a roll molding method, a doctor blade molding method, and the like. If the preforming is a doctor blade molding method, it is preferable because a glass sheet having a uniform film thickness can be efficiently produced in a large area.

  In the preliminary molding, it is preferable to mold a green sheet containing glass powder and an inorganic phosphor. The green sheet can be manufactured, for example, by the following process. After mixing the glass powder and the inorganic phosphor, the mixed powder is kneaded in a vehicle and defoamed to obtain a slurry. Next, the slurry is processed on a transparent resin by a doctor blade method and dried. Then, after drying, it cuts out to a desired magnitude | size, peels off transparent resin, and passes through the process of obtaining a green sheet. Furthermore, obtaining a desired thickness can be achieved by laminating a plurality of one green sheet and pressing them.

  In the present specification, the vehicle is obtained by dissolving a resin in an organic solvent. As the resin, ethyl cellulose, nitrocellulose, acrylic resin, vinyl acetate, butyral resin, melamine resin, alkyd resin, rosin resin, or the like can be used. As the organic solvent, aromatic hydrocarbons, aliphatic hydrocarbons, alcohols, ethers, ketones or esters can be used. The strength of the green sheet can be improved by further containing a butyral resin, a melamine resin, an alkyd resin, a rosin resin, or the like in the vehicle.

  The transparent resin for applying the slurry is not limited as long as a green sheet having a uniform film thickness is obtained and can be peeled off. For example, a PET film etc. are mentioned.

  The firing step is a step of firing glass powder (hereinafter also referred to as main firing) to form glass. The firing step includes firing (hereinafter also referred to as debuying) at a lower temperature than the main firing and is preferably performed in two stages. If removal is performed before the main firing, the organic matter contained in the preformed product can be sufficiently removed, and impurities in the plate-like glass after the firing step can be reduced. In particular, when a green sheet is used in preforming, it is preferably performed in two stages.

  The firing conditions for the main firing differ depending on the glass powder used. The firing temperature is preferably 450 to 900 ° C. or Ts ± 50 ° C. when the softening point of the glass used is Ts, and the firing time is preferably 1 to 6 hours. With such firing conditions, bubbles generated in the light conversion member (hereinafter also referred to as encapsulated bubbles) can be reduced. If the encapsulated foam is large, light may be scattered in the light conversion member, the transmittance of the light conversion member may be decreased, haze may be increased, and the quantum yield (QE) may be decreased.

  The firing conditions for the debuying process vary depending on the type and amount of the binder in the vehicle used in the production of the preform green sheet. For example, it is preferable to carry out by using an electric furnace etc. and hold | maintaining at 400-480 degreeC for 1 to 6 hours.

(Illumination light source having light conversion member)
The light conversion member of the present invention can be combined with a light source to obtain an illumination light source that emits a desired wavelength. The light conversion member is preferable because it can make the light extraction efficiency of the light source higher by contacting the light emitting surface of the light source.

  As the light source described above, a light emitting element chip having a flat light emitting surface is preferable, and a semiconductor light emitting element chip is more preferable. A semiconductor light emitting element chip that emits blue light is particularly preferable. An illumination light source in which a semiconductor light emitting element chip and a light conversion member are combined is also called an LED.

  Hereinafter, specific embodiments of the present invention will be described. However, the present invention is not construed as being limited to these. Examples 1 to 3 are examples of the present invention, and examples 4 and 5 are comparative examples.

(Example 1)
The glass raw materials were mixed so as to be 15% of SiO ₂ , 31% of B ₂ O ₃ , 34% of ZnO, 11% of BaO, and 9% of Bi ₂ O _{3 in} terms of mol% based on oxide. This was heated in an electric furnace to 1200 to 1400 ° C. in a platinum crucible and melted, and the melt was quenched with a rotating roll to form a glass ribbon. The glass ribbon was pulverized with a ball mill, passed through a sieve having a mesh with an opening of 150 μm, and further subjected to air classification to obtain a glass powder.

  The refractive index nd of the glass was 1.79, and the softening point Ts was 591 ° C.

A YAG inorganic phosphor was prepared as the inorganic phosphor. _{D 50} of the YAG inorganic phosphor was 10 [mu] m.

  The glass powder and the inorganic phosphor were mixed with 84% by volume of the glass powder and 16% by volume of the inorganic phosphor, kneaded with the vehicle, and defoamed to obtain a slurry. This slurry was applied to a PET film (manufactured by Teijin Limited) by the doctor blade method. This was dried in a drying furnace for about 30 minutes, cut into a size of about 7 cm square, and the PET film was peeled off to obtain green sheets having a thickness of 600 μm and 300 μm, respectively.

  Two of these green sheets were laminated and pressed. This was placed on a mullite substrate coated with a release agent, deburied at 380 ° C. for 4 hours in the atmosphere, and further fired at 570 ° C. under reduced pressure for 1 hour.

  The light conversion member thus obtained was measured for surface roughness Ra, quantum conversion efficiency (QE), haze, and transmittance of the first surface. These results are shown in Table 1. In Table 1, “-” indicates that it has not been evaluated.

  The plate thickness of the light conversion member was measured with a micrometer. The surface roughness Ra of the first surface of the light conversion member was measured with a surface roughness / contour shape measuring instrument (trade name: Surfcom 1400D, manufactured by Tokyo Seimitsu Co., Ltd.). The quantum conversion efficiency was measured at an excitation light wavelength of 460 nm using an absolute PL quantum yield measuring apparatus (manufactured by Hamamatsu Photonics, trade name: Quantauru-QY). Excitation light was made incident from the second surface, and converted light emitted from the first surface was detected by an integrating sphere, and QE was calculated as in equation (2). The haze and transmittance of the light conversion member were measured with a C light source using a haze measuring device (manufactured by Suga Test Instruments Co., Ltd., trade name: haze meter HZ-2).

(Example 2)
A light conversion member was produced in the same manner as in Example 1 except that the glass powder and the inorganic phosphor were mixed at 80% by volume of the glass powder and 20% by volume of the inorganic phosphor.

  About the obtained light conversion member, the thickness of the member, the surface roughness Ra of the first surface, the quantum conversion efficiency (QE), the haze, and the transmittance were measured in the same manner as in Example 1. These results are shown in Table 1.

(Example 3)
A light conversion member was produced in the same manner as in Example 1 except that glass powder and inorganic phosphor were mixed with glass powder 1 at 76% by volume and inorganic phosphor at 24% by volume.

  About the obtained light conversion member, the thickness of the member, the surface roughness Ra of the first surface, the quantum conversion efficiency (QE), the haze, and the transmittance were measured in the same manner as in Example 1. These results are shown in Table 1.

(Example 4)
A light conversion member was produced in the same manner as in Example 2 except that the first surface was polished with a free abrasive grain.

  About the obtained light conversion member, the thickness of the member, the surface roughness Ra of the first surface, the quantum conversion efficiency (QE), the haze, and the transmittance were measured in the same manner as in Example 1. These results are shown in Table 1.

(Example 5)
A light conversion member was produced in the same manner as in Example 3 except that the first surface was polished with a free abrasive grain.

  About the obtained light conversion member, the thickness of the member, the surface roughness Ra of the first surface, the quantum conversion efficiency (QE), the haze, and the transmittance were measured in the same manner as in Example 1. These results are shown in Table 1.

(Comparison of Example and Comparative Example)
Although Examples 1-3 differ in content of inorganic fluorescent substance, all have QE as high as 90% or more, and the light conversion member with high light extraction efficiency is obtained.

  Examples 4 and 5 both have a QE of less than 90%. Since the surface Ra of the first surface is smaller than 0.75 μm, it is considered that the emitted light on the first surface is reflected and the number of detected photons is reduced.

  The light conversion member of the present invention is used as a light conversion member in which an inorganic phosphor used as a light conversion member emitted from a light source such as an LED is dispersed.

Claims (11)

A light conversion member containing an inorganic phosphor and glass,
The refractive index nd of the glass is 1.7 to 2.8,
A light conversion member, wherein the surface roughness Ra of one or more surfaces of the light conversion member is 0.75 μm or more.   The light conversion member according to claim 1, wherein the light conversion member has a plate shape.   The light conversion member according to claim 1, wherein the thickness is 50 to 300 μm.   2. The inorganic phosphor is at least one selected from the group consisting of oxides, nitrides, oxynitrides, sulfides, oxysulfides, rare earth sulfides, aluminate chlorides, and halophosphates. The light conversion member according to any one of 1 to 3.   The light conversion member according to claim 1, wherein the glass has a softening point of 850 ° C. or less.   The light conversion member according to any one of claims 1 to 5, wherein the quantum conversion efficiency is 90% or more.   The light conversion member according to any one of claims 1 to 6, wherein the total light transmittance is 75% or more.   The light conversion member according to any one of claims 1 to 7, comprising a sintered body of a mixture containing an inorganic phosphor and glass powder.   The light conversion member according to claim 8, wherein the content ratio of the inorganic phosphor and the glass powder is, by volume ratio, inorganic phosphor: glass powder = 1: 99 to 40:60. An illumination light source comprising the light conversion member according to claim 1 and a light source,
An illumination light source, wherein the light conversion member is in contact with the light emitting surface of the light source and the surface roughness Ra of the surface not in contact with the light source is 0.75 μm or more.   The illumination light source according to claim 10, wherein the light source is a light emitting element chip.