JP5240656B2 - Luminescent color conversion member - Google Patents

Description

  The present invention relates to an emission color conversion member that converts the wavelength of light emitted from a light emitting diode (LED) or the like into a different wavelength. In particular, the present invention relates to a light emission color conversion member suitable for producing a light emission color conversion LED element such as a white LED.

  Conventionally, as an emission color conversion LED element using an inorganic phosphor, for example, an LED chip having a light emitting surface sealed using an organic binder resin (mold resin) mixed with a powdered inorganic phosphor has been proposed. ing. Thereby, a part or all of the light emission of the LED chip is absorbed by the inorganic phosphor and can be converted into a desired wavelength. However, in this method, there is a problem that the mold resin deteriorates due to heat generated by the LED chip or high-energy short wavelength (blue to ultraviolet) light, causing discoloration or deformation.

  Therefore, an emission color conversion member made of a completely inorganic solid in which an inorganic phosphor is fixed with glass instead of resin has been proposed (for example, see Patent Document 1). The luminescent color conversion member disclosed in Patent Document 1 is produced by firing a mixed powder of a glass powder having a high softening point and an inorganic phosphor powder. The light emitting color conversion member thus produced has a feature that the glass as a base material is not easily deteriorated by the heat or irradiation light of the LED chip.

By the way, YAG, oxides, nitrides, oxynitrides, sulfides, oxysulfides, halides, aluminate chlorides, halophosphates, and the like are known as the inorganic phosphors used in the luminescent color conversion member. It has been. Among these inorganic phosphors, sulfide phosphors and oxysulfide phosphors are characterized by converting near ultraviolet to blue excitation light into a wide wavelength range from green to red and having relatively high emission intensity. doing. For this reason, sulfide phosphors and oxysulfide phosphors are regarded as promising inorganic phosphors particularly used for light-emitting color conversion members for white LED elements. Sulfide phosphors and oxysulfide phosphors have relatively low heat resistance and are prone to degradation due to the heat and light of the LED chip. However, by appropriately selecting the glass composition, these phosphors can be degraded. It is known that it can be suppressed.
JP 2007-23267 A

  Even if the deterioration of the sulfide phosphor or the oxysulfide phosphor itself can be suppressed by using the glass powder having a specific composition, there is a problem that the glass powder and these phosphors react during firing. Thereby, the glass powder changes color, the light transmittance of the luminescent color conversion member decreases, and the luminous efficiency tends to be inferior.

  Accordingly, an object of the present invention is to provide a luminescent color conversion member containing a sulfide phosphor or an oxysulfide phosphor and having excellent luminous efficiency.

  As a result of various experiments, the present inventor has found that sulfur in glass is a cause of glass discoloration in a luminescent color conversion member using an inorganic phosphor containing sulfur such as a sulfide phosphor or an oxysulfide phosphor. I found out. Therefore, the present inventors have found that an emission color conversion member with high luminous efficiency can be obtained by limiting the sulfur content in the glass of the wavelength conversion member, and propose it as the present invention.

That is, the present invention is a light emitting color conversion member comprising a sintered body of a mixed powder containing glass powder and at least one inorganic phosphor powder selected from sulfides and oxysulfides, and the glass powder but, in _{mass%, SiO 2 30~70%, B} 2 O 3 1~15%, 0~10% MgO, CaO 0~25%, SrO 0~10%, BaO 8~40% ( however, MgO + CaO + SrO + BaO 10 -45%), Al ₂ O ₃ 0-20%, ZnO 0-10% composition , sulfur content in the glass in the sintered body is 1% by mass or less, emission color conversion characterized by It relates to members.

  As described above, the sulfide phosphor and the oxysulfide phosphor react with the glass powder at the time of firing and easily change the color of the glass. This is presumably because sulfur contained in the sulfide phosphor or oxysulfide phosphor diffuses into the glass as a result of the reaction between the sulfide phosphor or oxysulfide phosphor and the glass powder. Therefore, the greater the degree of reaction between the sulfide phosphor or oxysulfide phosphor and the glass, the greater the amount of sulfur diffused into the glass, and the more discoloration becomes.

  In the present invention, since the sulfur content in the glass of the sintered body is limited to 1% by mass or less, discoloration of the glass is suppressed, and as a result, a light emission color with good light transmittance and excellent light emission efficiency. A conversion member can be obtained.

  2ndly, it is preferable that content of an inorganic fluorescent substance powder is 0.01-30 mass% in the luminescent color conversion member of this invention.

Thirdly , the present invention relates to an LED element using any one of the light emission color conversion members.

  The luminescent color conversion member of the present invention emits fluorescence in the visible light range of 380 to 780 nm when irradiated with light having a light emission peak in a wavelength range of 250 to 500 nm, for example. In other words, when irradiated with ultraviolet (250 to 400 nm) or blue (400 to 500 nm) excitation light, it is a member that absorbs at least part of it and converts it into visible fluorescence. The shape of the luminescent color conversion member referred to in the present invention is not particularly limited as long as it is a sintered body of glass powder and inorganic phosphor powder. For example, a plate shape, a columnar shape, a hemispherical shape, etc. itself has a specific shape. In addition to the members having, a film-like sintered body formed on the substrate surface is also included.

In the present invention, the glass powder serves as a medium for stably holding the inorganic phosphor powder. In the present invention, as the glass powder _{SiO 2 -B 2 O 3 -RO (} RO is, MgO, CaO, at least one selected from SrO and BaO) that use silicate glass containing the composition of the system. Since this type of glass has a high softening point, it is characterized in that it hardly reacts with the inorganic phosphor powder during firing. In addition, when this type of glass is used, the inorganic phosphor powder is less likely to deteriorate even when baked at a temperature higher than the heat resistant temperature of the inorganic phosphor powder . Your name, the "~ based glass" in the present invention, refers to the glass containing the appropriate component as an essential component.

The SiO ₂ -B ₂ O ₃ -RO based glass, in _{mass%, SiO 2 30~70%, B} 2 O 3 1~15%, 0~10% MgO, CaO 0~25%, SrO 0~10 %, BaO 8-40% (however, MgO + CaO + SrO + BaO 10-45%), Al ₂ O ₃ 0-20%, and ZnO 0-10% are used . The reason for limiting the composition range as described above is as follows.

SiO ₂ is a component that forms a glass network. The content of SiO ₂ is 30 to 70%, preferably 40 to 60%. When the content of SiO ₂ is less than 30% by mass, chemical durability tends to be lowered. On the other hand, when the content of SiO ₂ is more than 70% by mass, the sintering temperature becomes high and the inorganic phosphor powder tends to be deteriorated.

B ₂ O ₃ is a component that significantly improves the meltability by lowering the melting temperature of the glass. The content of B ₂ O ₃ is 1 to 15%, preferably 2 to 10%. When the content of B ₂ O ₃ is less than 1% by mass, the above effect is hardly obtained. On the other hand, when the content of B ₂ O ₃ exceeds 15% by mass, the chemical durability tends to decrease.

  MgO, CaO, SrO, and BaO are components that improve the meltability by lowering the melting temperature of the glass.

  The content of MgO is 0 to 10%, preferably 0.1 to 5%. When the content of MgO exceeds 10% by mass, the chemical durability tends to deteriorate.

  The content of CaO is 0 to 25%, preferably 3 to 20%. When the content of CaO is more than 25% by mass, chemical durability tends to deteriorate.

  The content of SrO is 0 to 10%, preferably 0.1 to 5%. When the content of SrO is more than 10% by mass, chemical durability tends to deteriorate.

  BaO is a component having an effect of suppressing the reaction between the glass powder and the inorganic phosphor powder in addition to the above effect. The content of BaO is 8 to 40%, preferably 10 to 35%. When the content of BaO is less than 8% by mass, the reaction suppression effect between the glass powder and the inorganic phosphor powder tends to decrease. On the other hand, when the content of BaO exceeds 40% by mass, chemical durability tends to deteriorate.

  In order to improve the meltability without deteriorating the chemical durability of the glass, the total amount (RO content) of MgO, CaO, SrO and BaO is 10 to 45%, more preferably 11 to 40%. It is preferable to limit to. When the RO content is less than 10% by mass, it is difficult to obtain the effect of improving the meltability. On the other hand, when the RO content exceeds 45% by mass, the chemical durability tends to deteriorate.

Al ₂ O ₃ is a component that improves chemical durability. The content of Al ₂ O ₃ is 0 to 20%, preferably 2 to 15%. When the content of Al ₂ O ₃ exceeds 20% by mass, the meltability of the glass tends to deteriorate.

  ZnO is a component that improves the meltability by lowering the melting temperature of the glass. The content of ZnO is 0 to 10%, preferably 1 to 7%. When the content of ZnO exceeds 10% by mass, chemical durability tends to deteriorate.

In addition to the above components, various components can be added as long as the effects of the present invention are not impaired. For example, alkali metal oxides, P ₂ O ₅ , La ₂ O _{3 and the} like may be added in a total amount of 30% by mass or less.

Although the particle size of the glass powder is not particularly limited in the present invention, for example, the maximum particle diameter _{D max} is 200μm or less (in particular 45～150Myuemu, further 45～105Myuemu), and an average particle diameter _{D 50} more than 1 [mu] m (especially 2~20μm ) Is preferable. If the maximum particle diameter of the glass powder exceeds 150 μm, transparent portions formed by coarse glass particles will be scattered in the obtained wavelength conversion member, and it will be difficult to scatter light. Therefore, the color of the excitation light tends to be strong. In addition, when the average particle diameter D ₅₀ is less than 1 μm, the obtained wavelength conversion member scatters light excessively, so that the transmittance of the excitation light is remarkably lowered and the luminous efficiency is lowered. The conversion wavelength due to powder tends to be strong. Thus, when it is desired to increase the light scattering of the luminescent color conversion member, a glass powder with a small particle size may be used, and when it is desired to reduce the light scattering, a glass powder with a large particle size may be used. In the present invention, the maximum particle diameter D _max and the average particle diameter D ₅₀ refers to a value measured by a laser diffraction method.

  As the inorganic phosphor powder, at least one of a sulfide phosphor and an oxysulfide phosphor can be used.

Examples of the sulfide phosphor include ZnS: Cu ⁺ , Al ³⁺ , SrS: Eu ²⁺ , CaS: Eu ²⁺ , SrGa ₂ S ₄ : Eu ^{2+ and the} like. Examples of the oxysulfide phosphor include Y ₂ O ₂ S: Eu ³⁺ . Many of these inorganic phosphors have low chemical durability, and when used alone for a long time, they tend to deteriorate due to moisture, heat and light. Therefore, it is usually necessary to handle in a vacuum or a rare gas. However, when a sintered body with glass powder is used, these inorganic phosphors are not directly exposed to the atmosphere, and deterioration due to the influence of the atmosphere hardly occurs.

  In addition to the inorganic phosphor, a YAG phosphor, an oxide phosphor, a nitride phosphor, an oxynitride phosphor or the like may be used in combination.

  The luminous efficiency (lm / W) of the luminescent color conversion member varies depending on the type and content of the inorganic phosphor powder dispersed in the glass, the thickness of the luminescent color conversion member, and the like. What is necessary is just to adjust suitably content of an inorganic fluorescent substance powder, and the thickness of the luminescent color conversion member so that luminous efficiency may become optimal. If the content of the inorganic phosphor powder becomes too large, it becomes difficult to sinter, the porosity increases, and the inorganic phosphor is not easily irradiated with the excitation light, or the mechanical strength of the luminescent color conversion member This causes problems such as being easily lowered. 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 luminescent color conversion member of the present invention is 0.01 to 30% by mass, preferably 0.05 to 20% by mass, and 0.08 to 15% by mass. Adjusted.

  Moreover, in order to produce a luminescent color conversion member with high luminous efficiency, it is important that the sulfur content in the sintered glass is 1% by mass or less. When the sulfur content in the glass is more than 1% by mass, the glass tends to be colored, and as a result, the light transmittance of the luminescent color conversion member tends to decrease and the luminous efficiency tends to be inferior. In order to produce a light emitting color conversion member whose sulfur content in the glass after sintering is 1% by mass or less, for example, the amount of moisture attached to the inorganic phosphor powder, the amount of moisture attached to the glass powder, the firing temperature, the firing The atmosphere or the like may be controlled. By controlling these parameters, the reaction between the inorganic phosphor powder and the glass powder can be suppressed, and the diffusion of sulfur contained in the inorganic phosphor powder into the glass can be reduced.

  Moisture adhering to the sulfide phosphor or oxysulfide phosphor may oxidize these inorganic phosphors and generate hydrogen sulfide gas. Hydrogen sulfide gas is considered to be one of the causes that facilitate the diffusion of sulfur into the glass during firing. From such a viewpoint, the amount of water adhering to the inorganic phosphor powder is preferably 1% by mass or less.

  The water adhering to the glass powder may oxidize the sulfide phosphor or oxysulfide phosphor and generate hydrogen sulfide gas. Hydrogen sulfide gas is considered to be one of the causes that facilitate the diffusion of sulfur into the glass during firing. From such a viewpoint, the amount of water adhering to the powder glass is preferably 1% by mass or less.

  Examples of the method for adjusting the amount of water adhering to the inorganic phosphor powder and the powder glass to the above range include a method of performing a drying treatment at 100 to 300 ° C. for 3 to 10 hours.

  The firing temperature is adjusted in the range of the softening point of the glass powder ± 150 ° C., preferably ± 100 ° C. If the firing temperature is lower than the softening point of the glass powder of −150 ° C., the glass does not flow and it is difficult to obtain a dense sintered body. On the other hand, if the firing temperature is higher than the softening point + 150 ° C., the inorganic phosphor powder elutes into the glass and the emission intensity becomes weak, or the sulfur in the inorganic phosphor powder diffuses into the glass and the glass coloring It can be a cause.

The sulfide phosphors and oxysulfide phosphors are deteriorated by firing mainly due to the reaction with glass. In addition, these inorganic phosphor powders themselves may be oxidized. This is considered to be one of the causes. Therefore, the deterioration of the inorganic phosphor powder can be further suppressed by reducing the amount of oxygen in the firing atmosphere. Therefore, a firing atmosphere with less oxygen and moisture is preferable. Specifically, firing in an inert atmosphere (dry N ₂ , Ar, etc.) or a reduced pressure atmosphere is preferable.

Moreover, when the reduced pressure atmosphere is selected as the firing atmosphere, bubbles generated when the glass powder is softened and fused are easily removed. As a result, the obtained luminescent color conversion member also has an effect that the porosity (the proportion of bubbles remaining in the luminescent color conversion member) can be reduced to, for example, 2% or less. If there are few bubbles remaining in the luminescent color conversion member, light scattering is reduced, the transmittance is increased, and the luminous efficiency is likely to be increased. Note that the reduced-pressure atmosphere is specifically less than 1.013 × 10 ⁵ Pa, preferably 0.9 × 10 ⁵ Pa or less, more preferably 1000 Pa or less, and even more preferably 200 Pa or less. Although it does not specifically limit about a minimum, It is 0.001 Pa or more practically.

  The luminescent color conversion member of the present invention is particularly suitable for producing a luminescent color conversion LED element such as a white LED.

  Although the luminescent color conversion member of the present invention will be described in detail below based on examples, the present invention is not limited to these examples.

  Table 1 shows examples of the present invention and comparative examples.

  The luminescent color conversion member was produced as follows.

Glass materials of various oxides were prepared so that the composition was 50% by mass, SiO ₂ 50%, B ₂ O ₃ 5%, CaO 10%, BaO 25%, Al ₂ O ₃ 5%, ZnO 5%. . After mixing glass raw materials uniformly, it was put into a platinum crucible and melted at 1400 ° C. for 2 hours to obtain a uniform glass. The obtained glass was pulverized with alumina balls and classified to obtain glass powder (softening point 800 ° C.) having an average particle diameter D ₅₀ of 2.5 μm. In Examples 1 to 4, the obtained glass powder was dried at 200 ° C. for 6 hours, and the amount of attached water was 1% by mass or less. On the other hand, in Comparative Examples 1 and 2, the obtained glass powder was used without being subjected to a drying treatment.

  Next, an inorganic phosphor powder was mixed with the obtained glass powder at a mass ratio shown in Table 1 to prepare a mixed powder. The mixed powder was pressure-molded with a mold to prepare a cylindrical preform with a diameter of 1 cm. The preform was fired at the sintering temperature shown in Table 1 and then processed to obtain a disk-like light emitting color conversion member having a diameter of 8 mm and a thickness of 1 mm. About the obtained luminescent color conversion member, the emission spectrum was measured and the luminous efficiency was computed. The results are shown in Table 1.

  The emission spectrum was measured using a general-purpose emission spectrum measuring device with light having an excitation wavelength of 460 nm incident on one side of the emission color conversion member and emitted from the opposite side. The luminous efficiency was calculated by obtaining the total luminous flux of the emitted light using an integrating sphere, multiplying it by the standard relative luminous sensitivity, and then dividing by the power of the light source.

  The amount of water adhering to the glass powder was calculated from the difference in mass before and after drying when the glass powder was dried.

  The sulfur content in the glass portion of the luminescent color conversion member was measured using EPMA (Electron Probe Microanalyzer).

  As is clear from the results shown in Table 1, the luminescent color conversion members of Examples 1 to 4 show high luminous efficiency, but the luminescent color conversion members of Comparative Examples 1 and 2 have a sulfur content in the glass. Since it is more than 1% by mass, high luminous efficiency could not be obtained.

Claims (3)

A luminescent color conversion member comprising a sintered powder of a mixed powder containing glass powder and at least one inorganic phosphor powder selected from sulfides and oxysulfides, wherein the glass powder is, by mass, _{SiO 2 30~70%, B 2 O} 3 1~15%, 0~10% MgO, CaO 0~25%, SrO 0~10%, BaO 8~40% ( however, MgO + CaO + SrO + BaO 10~45%), Al A luminescent color conversion member comprising a composition of ₂ O ₃ 0 to 20% and ZnO 0 to 10%, and having a sulfur content of 1% by mass or less in glass in the sintered body.   2. The luminescent color conversion member according to claim 1, wherein the content of the inorganic phosphor powder is 0.01 to 30% by mass. The LED element which uses the luminescent color conversion member of Claim 1 or 2 .