JP7634451B2 - Coated KSF phosphor, method for producing said phosphor, curable silicone composition containing said phosphor, and optical semiconductor device - Google Patents

Description

The present invention relates to KSF phosphor (manganese-activated complex silicon fluoride phosphor) particles having a polymer surface coating, a curable silicone composition containing the phosphor particles having the polymer surface coating, and an optical semiconductor device encapsulated with a cured product of the curable silicone composition.

Currently, optical semiconductor devices (LEDs) that emit white light by combining blue light-emitting diodes with various phosphors have been put to practical use and are used in image display devices, lighting devices, and other applications.

In recent years, KSF phosphors have been used as phosphors that emit red fluorescence (Patent Documents 1 and 2), and have attracted attention as materials that can achieve both high luminous efficiency and color rendering. One of the characteristics of KSF phosphors is that they have a narrow half-width in the red emission region, and they are beginning to be effectively used in image display devices.

On the other hand, curable silicone resins with various phosphors dispersed therein are widely used as LED encapsulants. However, when an encapsulant with KSF phosphor dispersed in curable silicone is used for high-output LED applications, there is a problem that acidic substances are generated from the KSF phosphor in high-temperature environments, causing the silicone to decompose.

JP 2012-224536 A International Publication No. 2015/093430

The present invention has been made in consideration of the above circumstances, and aims to provide KSF phosphor particles that suppress the generation of acidic substances even under high temperature conditions, and a curable silicone composition that contains the phosphor particles.

In order to solve the above problems, the present invention provides
1. A coated KSF phosphor particle, comprising:
The coated KSF phosphor particles are KSF phosphor particles having a surface coating with a polymer, the polymer being a (meth)acrylic acid ester polymer, and the proportion of the polymer is in the range of 0.1 to 20 mass % of the entire coated KSF phosphor particles.

The coated KSF phosphor particles of the present invention suppress the release of acidic substances from the KSF phosphor even under high temperature conditions, and in particular, can prevent decomposition of the silicone resin in the cured product of a curable silicone composition containing the phosphor.

In the coated KSF phosphor particles of the present invention, the KSF phosphor is preferably a phosphor represented by K ₂ SiF ₆ :Mn ⁴⁺ .

Such KSF phosphors provide higher luminous efficiency.

In addition, in the coated KSF phosphor particles of the present invention, it is preferable that the (meth)acrylic acid ester polymer contains, as a constituent unit, a (meth)acrylic acid ester having at least one hydrogen atom directly bonded to a silicon atom in one molecule.

Since such polymers have high gas barrier properties, when coated onto the surface of KSF phosphor particles, they can suppress the release of acidic substances from the KSF phosphor in high-temperature environments.

The present invention also provides a method for producing the coated KSF phosphor particles, comprising the steps of:
The present invention provides a method for producing coated KSF phosphor particles, comprising the steps of: (1) preparing a coating composition containing (A) a (meth)acrylic acid ester polymer and (B) a solvent that dissolves the polymer; and (2) mixing KSF phosphor particles with the coating composition; and (3) volatilizing the solvent.

This method of manufacturing coated KSF phosphor particles allows the surface of the KSF phosphor particles to be efficiently coated.

In this case, it is preferable to use a phosphor represented by K ₂ SiF ₆ :Mn ⁴⁺ as the KSF phosphor.

By using such KSF phosphor particles, coated KSF phosphor particles with higher luminous efficiency can be obtained.

In addition, in the above manufacturing method, it is preferable to use, as the (meth)acrylic acid ester polymer, a polymer containing, as a structural unit, a (meth)acrylic acid ester having at least one hydrogen atom directly bonded to a silicon atom in one molecule.

By using such a polymer, the release of acidic substances from the KSF phosphor can be further suppressed in high-temperature environments, making it possible to obtain highly stable coated KSF phosphor particles.

The present invention also provides a curable silicone composition that contains the above-mentioned coated KSF phosphor particles.

The curable silicone composition of the present invention is useful as an encapsulant for optical semiconductor devices because it can prevent the decomposition of silicone in the cured product caused by acidic substances derived from the KSF phosphor under high temperature conditions.

The present invention also provides an optical semiconductor device in which an optical semiconductor element is encapsulated with a cured product of the above-mentioned curable silicone composition.

Such optical semiconductor devices are highly reliable because the optical semiconductor elements are stably sealed even in high-temperature environments.

The KSF phosphor having a surface coating made of the polymer of the present invention is useful as an encapsulant for optical semiconductor elements because it suppresses the release of acidic substances from the KSF phosphor even under high temperature conditions and can prevent decomposition of the silicone resin in the cured product of the curable silicone composition containing the phosphor.

As mentioned above, when an encapsulant in which KSF phosphor is dispersed in a curable resin is used for high-output LED applications, there is a problem in that acidic substances are generated from the KSF phosphor in high-temperature environments. For this reason, there is a demand for the development of a KSF phosphor that is stable even in high-temperature environments.

As a result of intensive research into achieving the above object, the inventors discovered that the above problems could be solved by using a KSF phosphor having a surface coating of a specific proportion of (meth)acrylic acid ester polymer, and thus completed the present invention.

That is, the present invention relates to coated KSF phosphor particles, which are KSF phosphor particles having a surface coating with a polymer, and the polymer is a (meth)acrylic acid ester polymer, and the proportion of the polymer is in the range of 0.1 to 20 mass % of the entire coated KSF phosphor particles.

The present invention is described in detail below, but is not limited to these.

[Coated KSF phosphor particles]
The coated KSF phosphor particles of the present invention are KSF phosphor particles having a surface coating with a polymer, and are characterized in that the polymer is a (meth)acrylic acid ester polymer.

The coated KSF phosphor particles may be KSF phosphor particles having a surface coating with the above-mentioned polymer, and the form is not particularly limited. For example, one KSF phosphor particle may be surface-coated with a polymer, or may be an aggregate thereof. Two or more KSF phosphor particles may be surface-coated with a polymer. The surface coating with a polymer may be a single layer or two or more layers, and the two or more surface coatings may be the same or different. Examples of two or more KSF phosphor particles surface-coated with a polymer include those in which the aggregated secondary particles of KSF phosphor particles are coated with a polymer to form one particle.
Each component constituting the coated KSF phosphor particles will be described below.

[KSF phosphor]
KSF phosphor (manganese-activated silicon complex fluoride phosphor) is a red phosphor in which Mn is added to K ₂ SiF ₆ crystal.

The KSF phosphor preferably used in the present invention is a phosphor represented by _{( K2SiF6} :Mn4 ⁺ ) in which tetravalent Mn is added as a luminescent ion _{to K2SiF6} , and emits light of 600 nm to 660 nm when excited with light having a peak wavelength of 455 nm. With such a phosphor represented _{by K2SiF6} :Mn4 ⁺ , higher luminous efficiency can be obtained.

The average particle size of the KSF phosphor is preferably 10 to 100 μm, and more preferably 20 to 50 μm.
The average particle size in the present invention is the median diameter (D50) in a volume-based particle size distribution obtained by a laser diffraction/scattering method.

The KSF phosphor may be manufactured by a conventional method, for example, by dissolving or dispersing metal fluoride raw materials such as silicon fluoride and manganese fluoride in hydrofluoric acid, and then heating and evaporating to dryness.

[Component (A): (meth)acrylic acid ester polymer]
The polymer that coats the surfaces of the KSF phosphor particles of the present invention is a (meth)acrylic acid ester polymer (hereinafter, referred to as component (A)).
This component has high gas barrier properties, so when it is coated on a KSF phosphor, it suppresses the release of acidic substances from the KSF phosphor in a high-temperature environment.

In the present invention, (meth)acrylic acid ester refers to an acrylic acid ester, a methacrylic acid ester, or both. Examples of acrylic acid esters include methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutyl acrylate, isopentyl acrylate, n-hexyl acrylate, isooctyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, isononyl acrylate, n-decyl acrylate, isodecyl acrylate, etc. Examples of methacrylic acid esters include methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, isopentyl methacrylate, n-hexyl methacrylate, isooctyl methacrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, isononyl methacrylate, n-decyl methacrylate, isodecyl methacrylate, etc. Among these, alkyl acrylates and alkyl methacrylates in which the alkyl group has 1 to 12 carbon atoms, and particularly 1 to 4 carbon atoms, are preferred. These can be used alone or in combination of two or more.

The (A) component preferably contains a (meth)acrylic acid ester having at least one hydrogen atom directly bonded to a silicon atom (hereinafter referred to as a SiH group) in one molecule as a constituent unit. Such an (A) component can be a polymer or copolymer containing a (meth)acrylic acid ester having at least one SiH group in one molecule as a monomer component.

（式中、Ｒは、水素原子またはメチル基であり、Ｒ^１は、独立に、炭素原子数１～１０の１価炭化水素基であり、Ｒ^２は、炭素原子数１～１０のアルキレン基であり、ｎは、０、１または２である。） An example of the (meth)acrylic acid ester having at least one SiH group in one molecule is a compound represented by the following formula (1).

(In the formula, R is a hydrogen atom or a methyl group, ^R1 is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, ^R2 is an alkylene group having 1 to 10 carbon atoms, and n is 0, 1, or 2.)

Specific examples of ^R1 include alkyl groups having 1 to 10 carbon atoms, preferably 1 to 6 carbon atoms, such as a methyl group, an ethyl group, and a propyl group, and aryl groups having 6 to 10 carbon atoms, such as a phenyl group, and the like, with a methyl group and a phenyl group being preferred.

Examples of ^R2 include alkylene groups having 1 to 10 carbon atoms, such as a methylene group, an ethylene group, a propylene group, and a butylene group, and an alkylene group having 1 to 3 carbon atoms is preferable.

The content of (meth)acrylic acid ester units having at least one SiH group per molecule in component (A) is preferably 10 to 100% by mass, and more preferably 20 to 50% by mass.

Component (A) is obtained by (co)polymerizing the above (meth)acrylic acid ester using a radical polymerization initiator such as 2,2'-azobisisobutyronitrile (AIBN).

The molecular weight of component (A) is preferably 1,000 to 1,000,000, more preferably 10,000 to 100,000, in terms of polystyrene equivalent number average molecular weight (Mn) measured by gel permeation chromatography (GPC) (developing solvent: tetrahydrofuran).

The amount of polymer (A) coated on the KSF phosphor (proportion of polymer) is 0.1 to 20% by mass, preferably 1 to 10% by mass, and particularly preferably 1 to 5% by mass, of the total coated KSF phosphor particles (KSF phosphor particles with a surface coating). If the amount of coating is small, the ability to block acidic substances generated by the KSF phosphor is poor, and if the amount of coating is large, the KSF phosphors may aggregate together, affecting the optical properties of the LED or causing discoloration due to heat.

[Method of manufacturing coated KSF phosphor particles]
The method for producing the KSF phosphor having a surface coating with the polymer of the present invention is not particularly limited, and any known technique may be appropriately adopted.

The KSF phosphor particles having a surface coating with the polymer of the present invention preferably have
The phosphor particles can be obtained by a manufacturing method including the steps of: (1) preparing a coating composition containing (A) a (meth)acrylic acid ester polymer and (B) a solvent that dissolves the polymer (hereinafter referred to as component (B)); mixing the coating composition with KSF phosphor particles; and (2) volatilizing the solvent.

Step (2) may be performed after step (1), or steps (1) and (2) may be performed simultaneously. Furthermore, steps (1) and (2) may be performed repeatedly depending on the desired amount of coating. Coated KSF phosphor particles having different coating layers can also be obtained by repeatedly performing steps (1) and (2) while changing the composition of component (A).

In step (1), a coating composition containing the (A) component and the (B) solvent can be obtained by using a known stirring, mixing, and dissolving device. The device for mixing the KSF phosphor particles and the coating composition can be set according to the production scale, and examples of the device include a combination of a spatula and a flask or an evaporating dish, a Henschel mixer, a super mixer, and other stirring and mixing devices. In step (2), a known stirring and drying device can be used to volatilize the solvent from the mixture of the KSF phosphor particles and the coating composition. If the stirring and drying device is equipped with a heating means or a decompression means, the solvent can be efficiently volatilized. When steps (1) and (2) are performed simultaneously, a device equipped with a means for thoroughly stirring, mixing, and drying the coating composition containing the KSF phosphor particles, the (A) (meth)acrylic acid ester polymer, and the (B) solvent can be used. In this case, the device can also be equipped with a heating means or a decompression means.

For example, in the case of a small amount, the KSF phosphor particles can be placed in a container, the coating composition can be added, and the solvent can be volatilized while stirring with a spatula, etc. On the other hand, in the case of polymer-coating a large amount of KSF phosphor particles, it is possible to coat them using a stirring device equipped with a degassing device such as an evaporator.
Furthermore, if the KSF phosphor particles aggregate during the polymer coating, it is possible to obtain non-aggregated KSF phosphor particles by temporarily removing the particles from the container, pulverizing the particles, and then drying the particles.

[Coating composition]
The coating composition used in the method for producing coated KSF phosphor particles of the present invention contains KSF phosphor particles, the above-mentioned component (A), and a solvent (component (B)) that dissolves component (A). The coating composition may contain components other than components (A) and (B) as necessary.

[Component (B)]
The solvent for component (B) is not limited as long as it dissolves component (A) and the coating composition can be obtained as a uniform solution, and known organic solvents can be used. For example, aromatic hydrocarbon solvents such as xylene, toluene, benzene, etc., aliphatic hydrocarbon solvents such as heptane, hexane, etc., halogenated hydrocarbon solvents such as trichloroethylene, perchloroethylene, methylene chloride, etc., ester solvents such as ethyl acetate, ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, cyclohexanone, etc., alcohol solvents such as ethanol, isopropanol, butanol, petroleum solvents such as ligroin, ether solvents such as diethyl ether, rubber volatile oil, silicone solvents, etc. are listed. Among these, aromatic hydrocarbon solvents and ester solvents are preferred. Depending on the desired evaporation rate, one type can be used alone, or two or more types can be combined to form a mixed solvent.

The amount of component (B) may be any amount that suits workability, but is preferably 70 to 99.9% by mass, and particularly preferably 80 to 99.5% by mass, of the total coating composition.

[Other ingredients]
Other ingredients include antioxidants.

[Curable Silicone Composition]
The curable silicone composition of the present invention contains a curable silicone resin and the coated KSF phosphor particles. The curable silicone resin is not particularly limited, but examples thereof include those for LED encapsulation, such as KER-2936-A/B (manufactured by Shin-Etsu Chemical Co., Ltd.).

The curable silicone composition of the present invention is useful, for example, as an encapsulant for optical semiconductor devices, because it can prevent the decomposition of silicone in the cured product caused by acidic substances derived from the KSF phosphor under high temperature conditions.

[Optical semiconductor device]
The present invention also provides an optical semiconductor device in which an optical semiconductor element is encapsulated with a cured product of the above-described curable silicone composition.

The coated KSF phosphor particles of the present invention suppress the release of acidic substances from the KSF phosphor even under high temperature conditions, and can prevent decomposition of the silicone resin in the cured product of the curable silicone composition containing the phosphor. Therefore, an optical semiconductor device in which an optical semiconductor element is encapsulated with the cured product of the curable silicone composition is highly reliable and does not easily deteriorate over time, because the optical semiconductor element is stably encapsulated even in high temperature environments.

The present invention will be specifically described below using examples, but these examples do not limit the present invention in any way. The non-volatile content of the coating composition was calculated from the mass difference before and after weighing 1.5 g of the composition into a petri dish and heating it at 105°C for 3 hours. The molecular weight (number average molecular weight Mn, weight average molecular weight Mw) is the value converted to polystyrene in GPC measurement (developing solvent: tetrahydrofuran). The average particle size is the median diameter (D50) in the volume-based particle size distribution obtained by the laser diffraction/scattering method.

[Synthesis Example 1]
60 parts by mass of methyl methacrylate, 600 parts by mass of a mixed solvent of isopropyl alcohol (IPA):ethyl acetate = 100:500 (mass ratio), and 0.5 parts by mass of AIBN were stirred at 80 ° C. for 3 hours to obtain a coating composition (non-volatile content 8.0 mass %) containing a methyl methacrylate polymer (Mn: 83,540, Mw: 124,550).

[Synthesis Example 2]
43 parts by mass of methyl methacrylate, 22 parts by mass of a SiH-containing methacrylic acid ester represented by the following formula, 600 parts by mass of a mixed solvent of IPA:ethyl acetate = 100:500 (mass ratio), and 0.5 parts by mass of AIBN were stirred at 80 ° C. for 3 hours to obtain a coating composition (non-volatile content 6.0 mass %) containing a SiH group-containing methacrylic acid ester-methyl methacrylate copolymer (Mn: 49,240, Mw: 103,130).
0% by mass) was obtained.

[Example 1]
5 g of KSF phosphor (K ₂ SiF ₆ :Mn ⁴⁺ , D50:25 μm) was placed in a flask, and 1 g of the coating composition containing the methyl methacrylate polymer obtained in Synthesis Example 1 was added and mixed using a spatula. Mixing was continued for 5 minutes while volatilizing the solvent, to obtain a KSF phosphor having a surface coating with a polymer. The coating amount of the methyl methacrylate polymer relative to the entire KSF phosphor having a polymer coating was 1.6 mass %.

[Example 2]
5 g of KSF phosphor (K ₂ SiF ₆ :Mn ⁴⁺ , D50:25 μm) was placed in a flask, and 1 g of the coating composition containing the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer obtained in Synthesis Example 2 was added and mixed using a spatula. Mixing was continued for 5 minutes while volatilizing the solvent, to obtain a KSF phosphor having a polymer surface coating. The coating amount of the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer relative to the entire KSF phosphor having a polymer coating was 1.2 mass %.

[Example 3]
The same operation as in Example 2 was repeated three times to obtain a KSF phosphor having a surface coating with a polymer. The coating amount of the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer relative to the entire KSF phosphor having a polymer coating was 3.6 mass %.

[Comparative Example 1]
5 g of KSF phosphor (K ₂ SiF ₆ :Mn ⁴⁺ , D50:25 μm) was placed in a flask, and 0.05 g of the coating composition containing the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer obtained in Synthesis Example 2 was added and mixed using a spatula. Mixing was continued for 5 minutes while volatilizing the solvent, to obtain a KSF phosphor having a polymer surface coating. The coating amount of the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer relative to the entire KSF phosphor having a polymer coating was 0.06 mass %.

[Comparative Example 2]
5 g of KSF phosphor (K ₂ SiF ₆ :Mn ⁴⁺ , D50:25 μm) was placed in a flask, and 20 g of the coating composition containing the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer obtained in Synthesis Example 2 was added and mixed using a spatula. After continuing mixing for 30 minutes while volatilizing the solvent, the mixture was thinly spread on a petri dish and naturally dried at 25° C. for 12 hours to obtain a KSF phosphor having a polymer surface coating. The coating amount of the SiH group-containing methacrylic acid ester-methyl methacrylate copolymer relative to the entire KSF phosphor having a polymer coating was 26 mass %.

[Comparative Example 3]
5 g of KSF phosphor (K ₂ SiF ₆ :Mn ⁴⁺ , D50:25 μm) was placed in a flask, 10 g of a 1 mass % acetone solution of methacryloxypropyltrimethoxysilane was added, and mixing was performed using a spatula. After continuing mixing for 30 minutes while volatilizing the solvent, the mixture was thinly spread on a petri dish and naturally dried at 25° C. for 12 hours to obtain a KSF phosphor having a surface coating with a silane coupling agent. The coating amount of the silane coupling agent relative to the entire KSF phosphor was 2 mass %.

The results of the following heat resistance test performed on the KSF phosphors with surface coatings using the polymer and silane coupling agent obtained in Examples 1 to 3 and Comparative Examples 1 to 3, and the KSF phosphor without surface coating (Comparative Example 4), are shown in Table 1.

[Heat resistance test]
2 g of LED curable silicone resin (KER-2936-A/B, Shin-Etsu Chemical Co., Ltd.) and 0.4 g of KSF phosphor were placed in a polyethylene container and mixed, after which 0.8 g was weighed out and placed in an aluminum petri dish, and heat resistance was evaluated based on the change in appearance and mass after exposure to an environment of 200° C. for 100 hours and 300 hours. The appearance was observed visually for color, and the rate of mass change was calculated as (mass after a specified time - mass at 0 hours) / mass at 0 hours x 100 (%).

As shown in Table 1, the KSF phosphor particles with a polymer surface coating obtained in Examples 1 to 3 had the same appearance and very little weight change even after 300 hours at 200°C, which is a good result. However, when KSF phosphor particles with a small amount of coating were used as in Comparative Example 1, when a KSF phosphor with a silane coupling agent surface coating was used as in Comparative Example 3, and when a KSF phosphor without a surface coating was used as in Comparative Example 4, the mass loss due to decomposition of the silicone resin was very large. Furthermore, when KSF phosphor particles with too much coating were used as in Comparative Example 2, the methacrylic acid ester polymer itself discolored, making it difficult to apply it to an encapsulant for optical semiconductor devices.

The present invention is not limited to the above-described embodiment. The above-described embodiment is merely an example, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and exhibits similar effects is included within the technical scope of the present invention.

Claims (8)

1. A coated KSF phosphor particle, comprising:
The coated KSF phosphor particles are KSF phosphor particles having a surface coating with a polymer, the polymer being a (meth)acrylic acid ester polymer, and the proportion of the polymer is in the range of 0.1 to 20 mass % of the entire coated KSF phosphor particles;
The coated KSF phosphor particles are characterized in that the (meth)acrylic acid ester polymer is a polymer of a (meth)acrylic acid alkyl ester having an alkyl group having 1 to 12 carbon atoms . 2. The coated KSF phosphor particle according to claim 1, wherein the KSF phosphor is a phosphor represented by K ₂ SiF ₆ :Mn ⁴⁺ . 3. The coated KSF phosphor particle according to claim 1, characterized in that the (meth)acrylic acid ester polymer contains, as a constituent unit, a (meth)acrylic acid ester represented by the following formula (1) having at least one hydrogen atom directly bonded to a silicon atom in one molecule:

(In the formula, R is a hydrogen atom or a methyl group, R1 ^is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, R2 ^is an alkylene group having 1 to 10 carbon atoms, and n is 0, 1, or 2.) A method for producing the coated KSF phosphor particles according to claim 1, comprising the steps of:
A method for producing coated KSF phosphor particles, comprising the steps of: (1) preparing a coating composition containing (A) a (meth)acrylic acid ester polymer and (B) a solvent that dissolves the polymer; and (2) mixing KSF phosphor particles with the coating composition. 5. The method for producing coated KSF phosphor particles according to claim 4, wherein a phosphor represented by K ₂ SiF ₆ :Mn ⁴⁺ is used as the KSF phosphor. 6. The method for producing coated KSF phosphor particles according to claim 4 or 5, characterized in that the (meth)acrylic acid ester polymer is a polymer containing, as a structural unit, a (meth)acrylic acid ester represented by the following formula (1) having at least one hydrogen atom directly bonded to a silicon atom in one molecule:

(In the formula, R is a hydrogen atom or a methyl group, R1 ^is independently a monovalent hydrocarbon group having 1 to 10 carbon atoms, R2 ^is an alkylene group having 1 to 10 carbon atoms, and n is 0, 1, or 2.) A curable silicone composition comprising the coated KSF phosphor particles according to any one of claims 1 to 3. 8. An optical semiconductor device comprising an optical semiconductor element encapsulated with a cured product of the curable silicone composition according to claim 7.