JP2015071699A - Wavelength conversion material, wavelength conversion member and light-emitting device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a material which makes it possible to prepare a wavelength conversion member with little decrease in light emission intensity over time in the case of application of the light of an LED and LD.SOLUTION: A wavelength conversion material comprises (a) glass powder comprising alkali metal oxide as a glass composition, (b) inorganic phosphor powder, and (c) inorganic oxide powder having photocatalytic activity. The inorganic oxide powder is preferably at least one selected from TiO, ZnO, SrTiO, WOand FeO.

Description

  The present invention relates to a material for producing a wavelength conversion member that converts the wavelength of light emitted from a light emitting diode (LED) or a laser diode (LD) to another wavelength.

  In recent years, as a next-generation light source that replaces fluorescent lamps and incandescent lamps, attention has been focused on light sources using LEDs and LDs from the viewpoints of low power consumption, small size and light weight, and easy light quantity adjustment. As an example of such a next-generation light source, for example, Patent Document 1 discloses a light source in which a wavelength conversion member that absorbs part of light from an LED and converts it into yellow light is disposed on an LED that emits blue light. Is disclosed. This light source emits white light which is a combined light of blue light emitted from the LED and yellow light emitted from the wavelength conversion member.

  As the wavelength conversion member, a material in which an inorganic phosphor powder is dispersed in a resin matrix has been conventionally used. However, when the wavelength conversion member is used, there is a problem that the resin is deteriorated by the light from the LED and the luminance of the light source tends to be lowered. In particular, there is a problem that the mold resin deteriorates due to heat generated by the LED or high energy short wavelength (blue to ultraviolet) light, causing discoloration or deformation.

  Therefore, a wavelength conversion member made of a completely inorganic solid in which an inorganic phosphor powder is dispersed and fixed in a glass matrix instead of a resin has been proposed (see, for example, Patent Documents 2 and 3). The wavelength conversion member has a feature that glass as a base material is not easily deteriorated by heat of the LED chip or irradiation light, and problems such as discoloration and deformation hardly occur.

  However, the wavelength conversion member has a problem in that the inorganic phosphor powder deteriorates due to firing at the time of manufacture, and the luminance easily deteriorates. In particular, in applications such as general lighting and special lighting, since high color rendering properties are required, it is necessary to use inorganic phosphor powder with relatively low heat resistance such as red and green, and the deterioration of inorganic phosphor powder is remarkable. Tend to be. Then, the wavelength conversion material which reduced the softening point by containing an alkali metal oxide in a glass powder composition is proposed (for example, refer patent document 4). Since the wavelength conversion material can be sintered at a relatively low temperature, deterioration of the inorganic phosphor powder during firing can be suppressed.

JP 2000-208815 A JP 2003-258308 A Japanese Patent No. 4895541 JP 2007-302858 A

  The wavelength conversion member containing an alkali metal oxide in the glass matrix has a problem that the emission intensity tends to decrease with time. With the further increase in output of light sources such as LEDs and LDs in recent years, the decrease in light emission intensity over time has become prominent.

  Therefore, an object of the present invention is to provide a wavelength conversion member with little decrease in light emission intensity over time when irradiated with light from an LED or LD.

  The wavelength conversion material of the present invention contains (a) a glass powder containing an alkali metal oxide as a glass composition, (b) an inorganic phosphor powder, and (c) an inorganic oxide powder having photocatalytic activity. It is characterized by.

  As already described, when a wavelength conversion member containing an alkali metal oxide in a glass matrix is irradiated with light from a high-power LED or LD, the emission intensity tends to decrease with time. About the details of the cause, the present inventors infer as follows.

  When a glass matrix containing an alkali metal oxide in the composition is irradiated with excitation light, the electrons existing in the outermost shell of oxygen ions in the glass matrix are excited by the energy of the excitation light and separated from the oxygen ions. The part is combined with alkali ions in the glass matrix to form a colored center (here, after the alkali ions are released, vacancies are formed). On the other hand, the holes generated by the escape of electrons move in the glass matrix, and a part of the holes are captured by the vacancies formed after the escape of alkali ions to form a colored center. It is considered that these colored centers formed in the glass matrix serve as an absorption source of excitation light and fluorescence, and the emission intensity of the wavelength conversion member decreases.

  Therefore, in order to suppress the above phenomenon, the wavelength conversion material of the present invention contains an inorganic oxide powder having photocatalytic activity. The inorganic oxide powder having photocatalytic activity receives energy from the excitation light source and supplies electrons and holes into the glass matrix. The electrons and holes supplied from the inorganic oxide powder cancel each other with the electrons and holes generated in the glass matrix. This suppresses electrons and holes generated in the glass matrix from acting on alkali ions and vacancies in the glass matrix. As a result, it is possible to suppress a decrease in light emission intensity with time of the wavelength conversion member.

In the wavelength conversion material of the present invention, the inorganic oxide powder is preferably at least one selected from TiO ₂ , ZnO, SrTiO ₃ , WO ₃ and Fe ₂ O ₃ .

  In the wavelength conversion material of the present invention, the inorganic oxide powder preferably has an average particle size of 2 nm to 150 μm.

  In the wavelength conversion material of the present invention, the content of the inorganic oxide powder is preferably 0.001 to 10% by mass.

  In the wavelength conversion material of the present invention, the content of the alkali metal oxide contained in the glass powder is preferably 0.1 to 35 mol%.

In the wavelength conversion material of the present invention, the content of Li ₂ O among the glass powder is preferably 0.1 mol% or more.

In the wavelength conversion material of the present invention, the glass powder is, in mol%, SiO ₂ 30-80%, B ₂ O ₃ 1-40%, Li ₂ O + Na ₂ O + K ₂ O 0.1-20%, and MgO + CaO + SrO + BaO 0. It is preferable to contain 1 to 45%.

  In the wavelength conversion material of the present invention, the inorganic phosphor powder includes nitride phosphor, oxynitride phosphor, oxide phosphor, sulfide phosphor, oxysulfide phosphor, halide phosphor, and aluminate phosphor. It is preferably at least one selected from the body.

  The wavelength conversion member of the present invention is obtained by firing any one of the wavelength conversion materials.

  The wavelength conversion member of the present invention comprises an inorganic phosphor powder and an inorganic oxide powder having photocatalytic activity dispersed in a matrix composed of a sintered body of glass powder containing an alkali metal oxide as a glass composition. It is characterized by that.

  The light emitting device of the present invention includes any one of the wavelength conversion members and a light source that irradiates the wavelength conversion member with excitation light.

  According to the present invention, even when a high-power LED or LD is used as a light source, it is possible to provide a wavelength conversion material capable of producing a wavelength conversion member with little decrease in light emission intensity over time. .

It is a schematic diagram which shows one Embodiment of the light-emitting device of this invention.

  The wavelength conversion material of the present invention contains (a) a glass powder containing an alkali metal oxide as a glass composition, (b) an inorganic phosphor powder, and (c) an inorganic oxide powder having photocatalytic activity. It is characterized by. Below, each component is demonstrated in detail.

  The glass powder serves as a medium for stably holding the inorganic phosphor powder in the wavelength conversion member after firing. Here, since the reactivity with the inorganic phosphor powder during firing varies depending on the composition of the glass powder, it is preferable to select a glass composition suitable for the inorganic phosphor powder to be used.

The glass powder contains an alkali metal oxide (at least one selected from Li ₂ O, Na ₂ O and K ₂ O) as a glass composition for the purpose of lowering the softening point. _{Further, SiO 2, B 2 O 3} , P 2 O 5, Bi 2 O 3 and at least one member selected from the TeO ₂ those containing 10 to 99 mol% are preferred. Specifically, SiO ₂ —B ₂ O ₃ —RO (R is at least one selected from Mg, Ca, Sr and Ba) —R ′ ₂ O (R ′ is selected from Li, Na and K) At least one) glass, SnO—P ₂ O ₅ —R ′ ₂ O glass, SiO ₂ —B ₂ O ₃ —R ′ ₂ O glass, SiO ₂ —B ₂ O ₃ —ZnO—R ′ ₂ O System glass and the like.

Examples of the SiO ₂ —B ₂ O ₃ —RO—R ′ ₂ O glass include, as a glass composition, mol%, SiO ₂ 30 to 80%, B ₂ O ₃ 1 to 40%, Li ₂ O + Na ₂ O + K. ₂ O 0.1 to 20%, and those containing 0.1~45% MgO + CaO + SrO + BaO are preferred. The reason for limiting the glass composition in this way will be described below.

SiO ₂ is a component that forms a glass network. The content of SiO ₂ is preferably 30 to 80%, more preferably 40 to 60%. When the content of SiO ₂ is too small, chemical durability tends to decrease. On the other hand, if the content of SiO ₂ is too large, the softening point becomes high, so that high-temperature firing is necessary for sufficient sintering. As a result, the inorganic phosphor powder tends to deteriorate during firing.

B ₂ O ₃ is a component having a great effect of improving the meltability by lowering the melting temperature. Further, it becomes likely to undergo phase separation by the inclusion of B ₂ O _3, an effect of improving a light diffusing property. The content of B ₂ O ₃ is preferably 1 to 40%, more preferably 5 to 30%. If the content of B ₂ O ₃ is too small, the effect is difficult to obtain. On the other hand, when the content of B ₂ O ₃ is too large, chemical durability tends to decrease.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the softening point. The content (total amount) of Li ₂ O, Na ₂ O and K ₂ O is preferably 0.1 to 35%, more preferably 1 to 25%, and still more preferably 2 to 20%. When there is too little content of these components, it will become difficult to reduce a softening point. On the other hand, when there are too many these components, chemical durability will fall easily. In addition, the phase separation becomes too large, and the light scattering loss tends to increase. Among them, Li 2 _O is a prominent component the effect of lowering the softening point. The Li ₂ O content is preferably 0.1 to 20%, more preferably 0.5 to 15%, and still more preferably 1 to 10%. The contents of Na ₂ O and K ₂ O are each preferably 0 to 20%, more preferably 0.1 to 15%, and still more preferably 0.5 to 10%.

  MgO, CaO, SrO and BaO are components that improve the meltability by lowering the melting temperature. It also has the effect of promoting phase separation. BaO also has an effect of suppressing the reaction with the inorganic phosphor powder. The content (total amount) of MgO, CaO, SrO and BaO is preferably 0.1 to 45%, more preferably 1 to 40%, and still more preferably 2 to 35%. If the content of these components is too small, the above effects are difficult to obtain. On the other hand, when there is too much content of these components, it exists in the tendency for chemical durability to fall. Further, the phase separation property becomes too large, and the phase separation state tends to fluctuate greatly even with a small change in the heat treatment temperature. As a result, the light diffusibility between lots of the obtained wavelength conversion member tends to vary.

  Preferred ranges for the above components are as follows. The content of MgO is preferably 0 to 10%, more preferably 0 to 5%. The content of CaO is preferably 0 to 30%, more preferably 0 to 20%. The content of SrO is preferably 0 to 20%, more preferably 0 to 10%. The content of BaO is preferably 0 to 40%, more preferably 0.1 to 30%.

  In addition to the above components, the glass powder may contain the following components.

Al ₂ O ₃ is a component that improves chemical durability. The content of Al ₂ O ₃ is preferably 0 to 20%, more preferably 1 to 18%. When the content of Al ₂ O ₃ is too large, there is a tendency that the melting is lowered.

  ZnO is a component that significantly promotes phase separation and lowers the melting temperature to improve the meltability. The content of ZnO is preferably 0 to 20%, more preferably 0.1 to 10%. When there is too much content of ZnO, chemical durability will fall easily. Also, the phase separation tends to be too large.

In addition to the above components, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , Gd ₂ O ₃ , La ₂ O ₃ , Y ₂ O ₃ , CeO ₂ , for the purpose of improving chemical durability, etc. Sb ₂ O ₃ , SnO ₂ , Bi ₂ O ₃ or ZrO ₂ may be incorporated up to 15% each.

The _{SnO-P 2 O 5 -R '} 2 O -based glass, for example, in _{mol%, SnO 35~80%, P 2} O 5 5~40%, B 2 O 3 0~30%, and, Li ₂ O ₊ Na ₂ O ₊ K ₂ those containing O 0.1 to 5% are preferred. The reason for limiting the glass composition in this way will be described below.

  SnO is a component that forms a glass network and lowers the softening point. The content of SnO is preferably 35 to 80%, more preferably 45 to 75%. When there is too little content of SnO, there exists a tendency for a softening point to become high or for a weather resistance to fall. On the other hand, when there is too much content of SnO, the devitrification thing resulting from Sn will precipitate and it will exist in the tendency for the transmittance | permeability to fall, As a result, the emitted light intensity of a wavelength conversion member will fall easily. Moreover, it becomes difficult to vitrify.

P ₂ O ₅ is a component that forms a glass network. The content of P ₂ O ₅ is preferably 5 to 40%, more preferably 10 to 30%. When the content of P ₂ O ₅ is too small, it is difficult to vitrify. On the other hand, when the content of P ₂ O ₅ is too large, or higher the softening point tends to weather resistance is remarkably lowered.

B ₂ O ₃ is a component that improves weather resistance and promotes phase separation. It also has the effect of stabilizing the glass. The content of B ₂ O ₃ is preferably 0 to 30%, more preferably 1 to 25%. If the B ₂ O ₃ content is too large, the weather resistance tends to lower. Also, the softening point tends to be too high.

Li ₂ O, Na ₂ O and K ₂ O are components that lower the softening point. The content (total amount) of Li ₂ O, Na ₂ O and K ₂ O is preferably 0.1 to 5%, more preferably 1 to 4%. When there is too little content of these components, it will become difficult to reduce a softening point. On the other hand, when there are too many these components, chemical durability will fall easily. In addition, the phase separation becomes too large, and the light scattering loss tends to increase. The content of each component of Li ₂ O, Na ₂ O and K ₂ O is preferably 0 to 5%, more preferably 0.1 to 4%, and still more preferably 1 to 4%.

In addition to the above components, CaO, MgO, SrO or BaO can be contained in a total amount of up to 5% in order to improve the meltability or reduce the softening point to facilitate low-temperature firing. In addition, for the purpose of improving chemical durability, etc., Al ₂ O ₃ , ZrO ₂ , ZnO, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , Gd ₂ O ₃ , Bi ₂ O ₃ , TeO _{2 are used.} or _La 2 _{O 3} may be contained up to 15%, respectively.

Examples of the SiO ₂ —B ₂ O ₃ —R ′ ₂ O glass include mol%, SiO ₂ 30 to 80%, B ₂ O _{3 1 to} 55%, Li ₂ O 0 to 20%, and Na ₂ O. _{0~25%, K 2 O 0~25%} , Li 2 O + Na 2 O + K 2 O 0.1~35%, Al 2 O 3 0~10%, and preferably one containing 0% ZnO.

In addition to the above components, MgO, CaO, SrO, and BaO can be added up to 30% in total in order to improve the meltability. Besides, P ₂ O ₅ is increased to 5% for improving the meltability, and Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , Gd ₂ O ₃ or La ₂ O for improving the chemical durability. ₃ may be contained up to 15% each.

Examples of the SiO ₂ —B ₂ O ₃ —ZnO—R ′ ₂ O glass include mol%, SiO ₂ 5-50%, B ₂ O ₃ 10-55%, ZnO 30-80%, Li ₂ O. _{0~20%, Na 2 O 0~20%} , K 2 O 0~20%, Li 2 O + Na 2 O + K 2 O 0.1~25%, 0~10% MgO, CaO 0~10%, SrO 0~ Those containing 10% and 0-10% BaO are preferred.

In addition to the above components, in order to improve chemical durability, Al ₂ O ₃ is added up to 5%, Ta ₂ O ₅ , TiO ₂ , Nb ₂ O ₅ , Gd ₂ O ₃ or La ₂ O ₃ is added to 15%. % May be included.

The particle size of the glass powder is not particularly limited, for example, the maximum particle diameter _{D 99} is 200μm or less (especially 150μm or less, more 105μm or less), and an average particle diameter _{D 50} of more than 0.1 [mu] m (in particular 1μm or more, further Is preferably 2 μm or more. If the maximum particle diameter D ₉₉ of the glass powder is too large, in the wavelength conversion member obtained, luminous efficiency becomes excitation light is less likely to scatter tends to decrease. When the average particle diameter D ₅₀ is too small, in the wavelength conversion member obtained, luminous efficiency tends to decrease with the excitation light is excessively scattered.

In the present invention, the average particle diameter D ₅₀ and the maximum particle diameter D ₉₉ indicate values measured by a laser diffraction method.

  The inorganic phosphor powder is not particularly limited as long as it is generally available on the market. For example, nitride phosphor powder, oxynitride phosphor powder, oxide phosphor powder (including garnet phosphor powder such as YAG phosphor powder), sulfide phosphor powder, oxysulfide phosphor powder, halogen Fluoride phosphor powder (halophosphate chloride, etc.) and aluminate phosphor powder. Of these inorganic phosphor powders, nitride phosphor powders, oxynitride phosphor powders and oxide phosphor powders are preferable because they have high heat resistance and are relatively unlikely to deteriorate during firing. The nitride phosphor powder and the oxynitride phosphor powder are characterized by converting near-ultraviolet to blue excitation light into a wide wavelength region from green to red and having a relatively high emission intensity. Therefore, the nitride phosphor powder and the oxynitride phosphor powder are particularly effective as inorganic phosphor powders used for the wavelength conversion member for white LED elements.

  Examples of the inorganic phosphor powder include those having an excitation band at a wavelength of 300 to 500 nm and an emission peak at a wavelength of 380 to 780 nm, particularly blue (wavelength 440 to 480 nm), green (wavelength 500 to 540 nm), yellow (wavelength 540). ˜595 nm) or red light (wavelength 600 to 700 nm).

Examples of inorganic phosphor powder that emits blue light when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm include (Sr, Ba) MgAl ₁₀ O ₁₇ : Eu ²⁺ , (Sr, Ba) ₃ MgSi ₂ O _8. : Eu ^{2+ and the} like.

As inorganic phosphor powders that emit green fluorescence when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm, SrAl ₂ O ₄ : Eu ²⁺ , SrBaSiO ₄ : Eu ²⁺ , Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ²⁺ , SrSiO _n : Eu ²⁺ , BaMgAl ₁₀ O ₁₇ : Eu ²⁺ , Mn 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⁺ , BaAl ₂ O ₄ : Eu ^{2+ and the} like.

As inorganic phosphor powders that emit green fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm, SrAl ₂ O ₄ : Eu ²⁺ , SrBaSiO ₄ : Eu ²⁺ , Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ³⁺ , SrSiOn: Eu ²⁺ , β-SiAlON: Eu ^{2+ and the} like.

Examples of the inorganic phosphor powder that emits yellow fluorescence when irradiated with excitation light having a wavelength of 300 to 440 nm include La ₃ Si ₆ N ₁₁ : Ce ³⁺ .

Examples of the inorganic phosphor powder that emits yellow fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm include Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ³⁺ and Sr ₂ SiO ₄ : Eu ²⁺ .

Inorganic phosphor powders that emit red fluorescence when irradiated with ultraviolet to near-ultraviolet excitation light having a wavelength of 300 to 440 nm include CaGa ₂ S ₄ : Mn ²⁺ , MgSr ₃ Si ₂ O ₈ : Eu ²⁺ , Mn ²⁺ , Ca _{2. ^{MgSi 2 O 7: Eu 2+,}} Mn 2+ , and the like.

Inorganic phosphor powders that emit red fluorescence when irradiated with blue excitation light having a wavelength of 440 to 480 nm include CaAlSiN ₃ : Eu ²⁺ , CaSiN ₃ : Eu ²⁺ , (Ca, Sr) ₂ Si ₅ N ₈ : Eu ²⁺ , α-SiAlON: Eu ^{2+ and the} like can be mentioned.

  A plurality of inorganic phosphor powders may be mixed and used in accordance with the wavelength range of excitation light or light emission. For example, when white light is obtained by irradiation with ultraviolet excitation light, inorganic phosphor powders emitting blue, green, yellow, and red fluorescence may be mixed and used.

  When there is too much content of the inorganic fluorescent substance powder in a wavelength conversion material, it will become difficult to sinter or there exists a tendency for a porosity to become large. As a result, in the obtained wavelength conversion member, problems such as it becomes difficult for the excitation light to be efficiently irradiated onto the inorganic phosphor powder, and the mechanical strength tends to decrease. On the other hand, when there is too little content of inorganic fluorescent substance powder, it will become difficult to obtain desired luminescence intensity. From such a viewpoint, the content of the inorganic phosphor powder in the wavelength conversion material is mass%, preferably 0.01 to 50%, more preferably 0.05 to 40%, and still more preferably 0.1 to 30. % Is adjusted.

  Note that the wavelength conversion member for the purpose of reflecting the fluorescence generated in the wavelength conversion member to the excitation light incident side and mainly taking out only the fluorescence to the outside is not limited to the above, and the emission intensity is maximized. As described above, the content of the inorganic phosphor powder can be increased (for example, in mass%, 50% to 80%, and further 55 to 75%).

As the inorganic oxide powder, crystal powder having photocatalytic activity is used. Specific examples include TiO ₂ , ZnO, SrTiO ₃ , WO ₃ or Fe ₂ O ₃ . These may be used alone or in combination of two or more. Of these, TiO ₂ or ZnO having high photocatalytic activity is preferable. In particular, TiO ₂ that is non-toxic and does not decompose even when irradiated with excitation light and is semipermanently stable is preferred. As TiO ₂ , anatase type, rutile type, or a mixture of anatase type and rutile type can be used.

The average particle diameter _{D 50} of the inorganic oxide powder is preferably 2Nm～150myuemu, more preferably 5Nm～100myuemu, more preferably 10Nm～50myuemu. When the average particle size D ₅₀ of the inorganic oxide powder is too small, easily penetration into the glass powder during firing, the desired effect is difficult to obtain. On the other hand, when the average particle size D ₅₀ of the inorganic oxide powder is too large, the surface area is small, the desired effect is difficult to obtain.

  The content of the inorganic oxide powder in the wavelength conversion material is preferably 0.001 to 10% by mass, more preferably 0.01 to 8% by mass, and still more preferably 0.1 to 5% by mass. As described above, the inorganic oxide powder suppresses a decrease in light emission intensity over time of the wavelength conversion member. In addition, it also has the function of increasing the scattering of excitation light in the wavelength conversion member. As a result, the excitation light is efficiently applied to the inorganic phosphor powder, so that the emission intensity can be improved. If the content of the inorganic oxide powder is too small, it is difficult to obtain the above effect. On the other hand, when the content of the inorganic oxide powder is too large, scattering becomes excessive, and on the contrary, excitation light is not efficiently irradiated onto the inorganic phosphor.

  A wavelength conversion member can be obtained by baking the wavelength conversion material of the present invention. The wavelength conversion member of the present invention comprises an inorganic phosphor powder and an inorganic oxide powder having photocatalytic activity dispersed in a matrix composed of a sintered body of glass powder containing an alkali metal oxide as a glass composition. It is characterized by that.

  The firing temperature is appropriately adjusted within the softening point of the glass powder within ± 150 ° C, preferably within ± 100 ° C. If the firing temperature is too low, the glass powder does not flow sufficiently and it is difficult to obtain a dense sintered body. On the other hand, if the firing temperature is too high, the inorganic phosphor powder may elute into the glass powder and the emission intensity may decrease. Or the component contained in inorganic fluorescent substance powder may diffuse and color in glass powder, and there exists a possibility that emitted light intensity may fall.

Note that firing is preferably performed in a reduced-pressure atmosphere. Specifically, the firing is preferably performed in an atmosphere of less than 1.013 × 10 ⁵ Pa, more preferably 1000 Pa or less, and even more preferably 400 Pa or less. Thereby, the amount of bubbles remaining in the wavelength conversion member can be reduced. As a result, the light scattering factor in the wavelength conversion member can be reduced, and the luminous efficiency can be improved. In addition, you may perform the whole baking process in a pressure-reduced atmosphere, for example, only a baking process is performed in a pressure-reduced atmosphere, and the temperature raising process and temperature-falling process before and behind that are performed in the atmosphere (for example, under atmospheric pressure) which is not a pressure-reduced atmosphere. You may go.

  The shape of the wavelength conversion member of the present invention is not particularly limited. For example, a plate shape, a column shape, a spherical shape, a hemispherical shape, a hemispherical dome shape, etc. It may be a film formed on the surface of the substrate.

FIG. 1 shows an embodiment of a light emitting device of the present invention. As shown in FIG. 1, the light emitting device 1 includes a wavelength conversion member 2 and a light source 3. Light source 3 irradiates the excitation light _{L in} respect to the wavelength conversion member 2. Excitation light L _in incident to the wavelength conversion member 2 is converted into light of another wavelength, the light source 3 emits as L _out from the opposite side. At this time, the combined light of the light after wavelength conversion and the excitation light transmitted without wavelength conversion may be emitted.

  Hereinafter, the present invention will be described in detail based on examples, but the present invention is not limited to these examples.

(1) Production of glass powder Table 1 shows the composition of the glass powder used in this example.

First, the raw materials were prepared so as to have the composition shown in Table 1. The raw material was melted and vitrified in a platinum crucible at a temperature of 800 to 1500 ° C. for 1 to 2 hours, and the molten glass was cast between a pair of cooling rollers to form a film. After the film-shaped glass was pulverized by a ball mill, the average particle diameter D ₅₀ and classified to obtain a glass powder 2.5 [mu] m.

The density and softening point of each glass powder were measured using a sample obtained by forming molten glass into a block shape or a cylindrical shape according to each measurement and annealing. For the softening point, a fiber elongation method was used, and a temperature at which the viscosity was 10 ^7.6 dPa · s was adopted. The density was determined by the Archimedes method.

(2) Production of Wavelength Conversion Member Tables 2 to 6 show Examples (Sample Nos. 1 to 12) and Comparative Examples (Sample Nos. 13 to 15) of the present invention.

Y ₃ (Al, Gd) ₅ O ₁₂ : Ce ³⁺ (YAG) phosphor powder and TiO ₂ powder (average particle diameter D ₅₀ : 20 nm mixture of rutile type and anatase type, average A predetermined amount of particle diameter D ₅₀ : 800 nm anatase type, average particle diameter D ₅₀ : 113 μm anatase type) was mixed to obtain a wavelength conversion material. In addition, No. The 13-15 samples were not added TiO ₂ powder. The wavelength conversion material was pressure-molded with a mold to prepare a cylindrical preform with a diameter of 1 cm. By processing the sintered body obtained by firing the preform at a temperature shown in the table, a wavelength conversion member having a 1.2 mm square and a thickness of 0.2 mm was obtained. The obtained wavelength conversion member was mounted on an LED chip having a wavelength of 445 nm, and was continuously irradiated for 100 hours with energization at 700 mA. Irradiation was performed in an integrating sphere, and the energy distribution spectrum of light emitted from the upper surface of the wavelength conversion member was measured using a general-purpose emission spectrum measuring device. The total luminous flux value was calculated by multiplying the obtained spectrum by the standard relative luminous sensitivity. Total luminous flux values were calculated before irradiation and after 100 hours of irradiation. Tables 2 to 6 show the ratio of the total luminous flux value after 100 hours irradiation to the total luminous flux value before irradiation ((total luminous flux value after 100 hours irradiation / total luminous flux value before irradiation) × 100 (%)).

  As is apparent from Tables 2 to 5, the total light flux value of the wavelength conversion member of the example hardly decreased even after 100 hours of excitation light irradiation. On the other hand, as apparent from Table 6, the total light flux value of the wavelength conversion member of the comparative example was greatly reduced after 100 hours of excitation light irradiation.

  The wavelength conversion material of the present invention is suitable as a material for wavelength conversion members used for general illumination such as white LED, special illumination (for example, projector light source, automobile headlamp light source) and the like.

DESCRIPTION OF SYMBOLS 1 Light emitting device 2 Wavelength conversion member 3 Light source

Claims (11)

  A wavelength conversion material comprising (a) a glass powder containing an alkali metal oxide as a glass composition, (b) an inorganic phosphor powder, and (c) an inorganic oxide powder having photocatalytic activity. The wavelength conversion material according to claim 1, wherein the inorganic oxide powder is at least one selected from TiO ₂ , ZnO, SrTiO ₃ , WO ₃ and Fe ₂ O ₃ .   The wavelength conversion material according to claim 1 or 2, wherein the inorganic oxide powder has an average particle size of 2 nm to 150 µm.   4. The wavelength conversion material according to claim 1, wherein the content of the inorganic oxide powder is 0.001 to 10% by mass.   The wavelength conversion material according to any one of claims 1 to 4, wherein the content of the alkali metal oxide contained in the glass powder is 0.1 to 35 mol%. The wavelength conversion material according to claim 1, wherein the content of Li ₂ O contained in the glass powder is 0.1 mol% or more. Glass powder, in _{mol%, SiO 2 30~80%, B} 2 O 3 1~40%, Li 2 O + Na 2 O + K 2 O 0.1~20%, and containing 0.1~45% MgO + CaO + SrO + BaO The wavelength conversion material according to any one of claims 1 to 6, wherein:   The inorganic phosphor powder is at least one selected from a nitride phosphor, an oxynitride phosphor, an oxide phosphor, a sulfide phosphor, an oxysulfide phosphor, a halide phosphor, and an aluminate phosphor The wavelength conversion material according to claim 1, wherein the wavelength conversion material is a material for wavelength conversion.   A wavelength conversion member obtained by firing the wavelength conversion material according to claim 1.   A wavelength conversion member comprising an inorganic phosphor powder and an inorganic oxide powder having a photocatalytic activity dispersed in a matrix composed of a sintered body of glass powder containing an alkali metal oxide as a glass composition. .   A light emitting device comprising: the wavelength conversion member according to claim 9 or 10; and a light source that irradiates the wavelength conversion member with excitation light.