JP2003277586A - Epoxy resin composition for encapsulating optical semiconductor element and optical semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for encapsulating an optical semiconductor element capable of contributing not only to light transmittance at the time of light receiving and emitting of an optical semiconductor device but also to ensuring light diffusion, and light using the same A semiconductor device is provided. SOLUTION: The epoxy resin composition for encapsulating an optical semiconductor element, comprising an epoxy resin, a curing agent, and a curing accelerator, and having a filler made of a translucent organic substance, The difference between the refractive index of the cured product composed of the resin, the curing agent, and the curing accelerator, and the refractive index of the filler is ± 0.01 or more, and the optical semiconductor element sealing having a thickness of 1 mm. Since the light transmittance of the molded article made of the cured product of the epoxy resin composition is in the range of 30 to 85% and the light reflectance is in the range of 2 to 70%, sufficient light diffusing property is provided together with good light transmittance. It becomes possible to secure.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an epoxy resin composition for encapsulating an optical semiconductor element and an optical semiconductor device.

[0002]

2. Description of the Related Art Conventionally, an epoxy resin composition has been generally used as a sealing material for an optical semiconductor element such as a light receiving element or a light emitting element. As a filler for the material, various studies such as using silica powder with a reduced difference in refractive index from the cured epoxy resin from the viewpoint of a balance between reduction of internal stress and securing of light transmittance have been vigorously made. ing.

[0003]

On the other hand, as described above,
By studying adjustment of the refractive index of silica powder, mainly
In contrast to the conventional technological trend of pursuing the securing of light transmittance, in recent years, optical semiconductor devices such as LEDs have been researched to be applied to a wider range of applications such as lighting applications. In addition to the characteristics, there is an increasing need for application to devices that require optical diffusivity and optical interference prevention.

The present invention has been made in view of the above circumstances, and an object thereof is to provide an epoxy resin composition for optical semiconductor element encapsulation that can contribute not only to light transmission but also to light diffusion. An object is to provide an object and an optical semiconductor device using the same.

[0005]

In order to solve the above problems, the epoxy resin composition for optical semiconductor element encapsulation according to claim 1 contains an epoxy resin, a curing agent, and a curing accelerator. And an epoxy resin composition for encapsulating an optical semiconductor element, which comprises a filler made of a translucent organic material, wherein the epoxy resin, the curing agent, and the curing accelerator are cured products. And the refractive index of the filler are different.

An epoxy resin composition for encapsulating an optical semiconductor element according to claim 2 is the epoxy resin composition for encapsulating an optical semiconductor element according to claim 1, wherein the epoxy resin, the curing agent, and the From the cured product of the epoxy resin composition for optical semiconductor element encapsulation, the difference between the refractive index of the cured product of the curing accelerator and the refractive index of the filler is ± 0.01 or more, and the thickness is 1 mm. The molded product has a light transmittance of 30 to 85% and a light reflectance of 2 to 70%.

In the epoxy resin composition for optical semiconductor element encapsulation according to claim 3, in the epoxy resin composition for optical semiconductor element encapsulation according to claim 1 or 2, the filler is at least , A condensation reaction product of melamine and formaldehyde.

In the epoxy resin composition for optical semiconductor element encapsulation according to claim 4, in the epoxy resin composition for optical semiconductor element encapsulation according to claim 1 or 2, the filler is at least And a methacrylic acid ester polymerization reaction product.

The epoxy resin composition for optical-semiconductor element encapsulation according to claim 5 is the epoxy resin composition for optical-semiconductor element encapsulation according to any one of claims 1 to 4, wherein the filling is performed. The amount of the material added is 0.5 to 30 mass% of the entire epoxy resin composition.

In the optical semiconductor device according to claim 6,
An optical semiconductor element is encapsulated by using the epoxy resin composition for encapsulating an optical semiconductor element according to any one of claims 1 to 5.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below. The epoxy resin composition for encapsulating an optical semiconductor element according to the present invention contains an epoxy resin, a curing agent, and a curing accelerator, and uses a filler made of a light-transmitting organic material. is there. Furthermore, the epoxy resin, the curing agent, and the cured product of the curing accelerator and the refractive index of the cured material, the refractive index of the filler is different, the epoxy resin,
The difference between the refractive index of a cured product composed of the curing agent and the curing accelerator and the refractive index of the filler is ± 0.01 or more, and in addition, the epoxy for optical semiconductor element encapsulation having a thickness of 1 mm is used. The light transmittance of a molded article made of a cured product of the resin composition,
It is characterized by a light reflectance of 30 to 85% and a light reflectance of 2 to 70%. As a result, it is possible to ensure a sufficient light diffusion property as well as a good light transmission property.

That is, the difference between the refractive index of the cured material composed of the epoxy resin, the curing agent, and the curing accelerator, and the refractive index of the filler is used as the filler composed of the light-transmitting organic material. However, it is necessary that the difference is ± 0.01 or more. Those having the same refractive index (for example, the epoxy resin,
If a hardened product of the above-mentioned curing agent and the above-mentioned curing accelerator, etc.) or having a refractive index of ± 0.01 or less, a sufficient light diffusing effect cannot be obtained even though the translucency can be secured. Is.

The above-mentioned translucent organic substance is specifically an organic polymer such as one containing a condensation reaction product of melamine and formaldehyde and one containing a polymerization reaction product of methacrylic acid ester. A compound can be illustrated.
All of these can be obtained as a solid having a light-transmitting property, and if the one containing a condensation reaction product of melamine and formaldehyde is taken as an example, the component ratio of melamine and formaldehyde, which are the starting materials involved in the condensation reaction, Or the addition of N-alkyl-substituted melamines, benzoguanamine, etc., and further examination of condensation reaction conditions such as reaction temperature and reaction time, etc., enables fine adjustment and optimization of the refractive index of the filler. Is to be.

Similarly, in the case of containing a polymerization reaction product of methacrylic acid ester, investigation of components such as methacrylic acid ester as a starting material for the polymerization reaction, addition of divinylbenzenes, etc. It is possible to finely adjust and optimize the refractive index of the filler by studying polymerization reaction conditions such as reaction temperature and reaction time.

Further, in the epoxy resin composition for encapsulating an optical semiconductor device of the present invention, the filler made of the above-mentioned organic material having a light-transmitting property has a maximum particle diameter of 150 μm or less and an average particle diameter of 0. It has been found that the optical characteristics and the moldability can be made compatible with each other if the constitution is made to be 1 micron or more and 50 microns or less. That is, the maximum particle size is 150
When the average particle size of the above filler is 0.1 micron or less, light transmission is caused unless a considerably large amount is added. Since it is not possible to achieve both compatibility and diffusibility, it is easy to affect the formability. On the other hand, when the average particle size is 50 microns or more, the transparency and the light transmittance are significantly lowered, which is not preferable.

Further, by using a filler made of these organic substances as the filler, it is possible to contribute to the reduction of mold wear and the prevention of damage to the mold, and the line of the epoxy resin composition and the filler made of these organic substances. Since the difference in expansion coefficient can be designed to be sufficiently small, it is possible to reduce cracks inside the molded product of the resin composition and to improve mounting reliability by reducing stress concentration.

In particular, in the technical field of resin encapsulation in transfer molding using an epoxy resin composition which is an encapsulating material for optical semiconductors such as light emitting elements and light receiving elements, in the post-molding step, solder mounting is performed in the subsequent steps. For the purpose of improving solder wettability or coating the lead frame,
An optical semiconductor device in which a lead portion is solder-coated or solder-plated has been commercialized. Conventionally, these optical semiconductor devices have been mainly mounted by lead insertion mounting by solder dipping, but with the recent shift in technology trends toward miniaturization and high-density mounting, they are compatible with surface mounting by IR reflow. There is an increasing need for materials having high solder heat resistance that can be used, and the epoxy resin composition for optical semiconductor element encapsulation according to the present invention has a small difference in linear expansion coefficient between the epoxy resin composition and the filler made of these organic materials, It can be said that it can sufficiently meet such needs. Furthermore, the epoxy resin composition for optical semiconductor element encapsulation according to the present invention having such high solder heat resistance uses a high melting point lead-free solder which has been attracting attention from the viewpoint of reducing the load on the global environment in recent years. It can be said that it can be applied to assembly.

On the other hand, when the epoxy resin composition for encapsulating an optical semiconductor element in which the particle shape of the filler made of these organic substances is substantially spherical is used, compared with the case where the particle shape is crushed, It is possible to further reduce die wear and chip damage due to the filler.

Further, in the epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, in order to secure translucency, light diffusibility and good molding characteristics, a filler made of the above organic substance is used. The amount added is 0.5 based on the total amount of the epoxy resin composition.
It is preferably in the range of -30% by mass. That is, when the added amount is less than 0.5% by mass, a sufficient effect of the light diffusivity cannot be obtained, and when the added amount is 30% by mass or more, the light transmittance is remarkably lowered, the fluidity is lowered during molding of the material, voids, etc. This is because there is a risk of causing problems such as molding defects. In other words, the amount of the filler added is 0.5 to 0.5% of the total amount of the epoxy resin composition.
By setting the content to 30% by mass, it is possible to secure the translucency, the light diffusion property, and the good molding characteristics.

[Production Method] In the above epoxy resin composition, an epoxy resin, a curing agent, a curing accelerator, a filler, and other additive components are melt-mixed or uniformly mixed with a mixer, a blender or the like, and then three It can be produced by melt-kneading with a roll or the like, cooling and solidifying this, crushing, and if necessary, tableting into a tablet. When the properties of the above epoxy resin composition are liquid at room temperature,
It can be produced by melt mixing or melt kneading. Then, the epoxy resin composition thus obtained,
The optical semiconductor device is manufactured by transfer molding a tablet in the case of a solid and using it for encapsulating an optical semiconductor element, and in the case of a liquid, casting and curing by a method such as casting, potting, printing, etc. can do.

In the epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, the usable epoxy resin is not particularly limited as long as it has two or more epoxy groups in one molecule, but it is for an optical semiconductor. It is preferable that the epoxy resin composition has relatively little coloring. For example, bisphenol A type epoxy resin, bisphenol F type epoxy resin,
Examples thereof include bisphenol S type epoxy resin, orthocresol novolac type epoxy resin, alicyclic epoxy resin, triglycidyl isocyanurate, and aliphatic epoxy resin. Further, an epoxy resin obtained by hydrogenating an aromatic ring of the above-mentioned epoxy resin having an aromatic ring can also be used. Furthermore, even if these epoxy resins are used alone,
It can be used together.

In the epoxy resin composition for optical semiconductor element encapsulation according to the present invention, usable curing agent is not particularly limited as long as it reacts with the above epoxy resin, but epoxy resin composition for optical semiconductors It is preferable to use those having relatively little coloring. For example, hexahydrophthalic anhydride, acid anhydride such as tetrahydrophthalic anhydride, phenol, cresol, xylenol, novolak type phenol resin obtained by condensation reaction with resorcin and formaldehyde, liquid polymercaptan or polysulfide resin There are mercaptan-based curing agents and the like. In addition to these, amine-based curing agents can also be used, but since the discoloration at the time of curing is large, it is necessary to pay attention to the addition amount when used. Further, these may be used alone or in combination. With respect to the equivalent ratio of these epoxy resin and curing agent, the epoxy / curing agent equivalent ratio is preferably 0.8 to 2.0.

In the epoxy resin composition for optical semiconductor element encapsulation according to the present invention, usable curing accelerators are:
There is no particular limitation as long as it has an action of promoting the reaction between the epoxy resin and the curing agent, but a resin having relatively little coloring is preferable. For example, organic phosphine-based curing accelerators such as triphenylphosphine and diphenylphosphine, 1,8-diazabicyclo (5,4,0) undecene-7 [1,8-Diazabicyclo [5.4.
0] undec-7-ene] (DBU), triethanolamine, benzyldimethylamine and other tertiary amine curing accelerators, tetraphenylphosphonium / tetraphenylborate, tetraphenylphosphonium / bromide and other organic salts, 1-benzyl Examples thereof include imidazoles such as 2-phenylimidazole. Further, these may be used alone or in combination. The content of these curing accelerators is preferably 0.05 to 5.0% by mass. When the addition amount is 0.01% by mass or less, a sufficient effect of accelerating the reaction between the epoxy resin and the curing agent cannot be obtained, the curing time becomes long, and the molding time cannot be shortened. Further, when the content of the curing accelerator is 5.0% by mass or more, the curing time becomes too short, so that voids are generated in the molded body or the epoxy resin composition is not filled in the molding die. It also causes problems in the molding process.

In the epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, in addition to the above, if necessary, a discoloration preventing agent, a deterioration preventing agent, a dye, an ultraviolet absorber, a silane coupling agent, a modifying agent. There is no problem even if agents, plasticizers, diluents and the like are added. In particular, even in the filler made of the above-mentioned organic material, it is possible to use a filler treated with a known silane coupling agent (aminosilane type, epoxysilane type, mercaptosilane type coupling agent, etc.),
It goes without saying that there is no limitation as long as it can contribute to solving the above problems.

On the other hand, as an optical semiconductor device in which an optical semiconductor element is encapsulated by using the epoxy resin composition for encapsulating an optical semiconductor element of the present invention, an optical semiconductor element having a light emitting portion is provided, and the optical semiconductor element of the present invention is used. Examples of the epoxy resin composition for semiconductor element encapsulation include those obtained by encapsulating such an optical semiconductor element.

FIG. 1 is a sectional view showing a typical embodiment of such an optical semiconductor device of the present invention. That is, in FIG. 1, an optical semiconductor device 1 mounts an LED chip 5, which is a semiconductor element having an electrode 2, an electrode 3 and a light emitting portion 8 electrically connected to a metal wire 4, on the electrode 2, This is a cured product 6 of the epoxy resin composition for optical semiconductor element encapsulation of the present invention.
It is sealed in and enclosed in the case 7. In an optical semiconductor device in which an optical semiconductor element is encapsulated by using the epoxy resin composition for encapsulating an optical semiconductor element of the present invention,
Enables encapsulation of optical semiconductor devices that ensure good light transmission and sufficient light diffusion, and is applied to devices that require not only light transmission but also light diffusion and optical interference prevention. It is possible to meet the new needs mentioned above.

[0027]

[Examples] Epoxy resin, curing agent, curing accelerator,
The epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, which contains a filler and the like, was evaluated. This will be specifically described by the following examples.

(Preparation of Resin Composition) Epoxy Resin (Table 1
As component A) therein, "Epicoat 1" which is a bisphenol A type epoxy resin manufactured by Japan Epoxy Resin Co., Ltd.
001 ”(equivalent 475) was used. As the curing agent (Component B in Table 1), "THPA" (equivalent weight 152) manufactured by Shin Nippon Rika Co., Ltd. was used. Furthermore, 1-benzyl-2-phenylimidazole was used as a curing accelerator (component C in Table 1). The alkali-free glass (refractive index: 1.583) used as the filler [Comparative Example] has a refractive index with the cured product composed of the above epoxy resin, curing agent, and curing accelerator, by adjusting the glass components. The refractive index was adjusted so that the difference was within ± 0.01. On the other hand, the "translucent organic substance" used as the filler is a cured product (resin component (component A in Table 1) composed of the above-mentioned epoxy resin, curing agent, and curing accelerator, obtained by the method described above.
+ Component B + component C) cured product only)
The refractive index is adjusted to be 0.01 or more, "containing a condensation reaction product of melamine and formaldehyde (hereinafter referred to as" melamine-based organic filler ")", and similar refractive index adjustment. The "comprising the methacrylic acid ester polymerization reaction product (hereinafter referred to as" PMMA-based organic filler ")" was used.

Then, the epoxy resin, the curing agent, the curing accelerator, and the filler described above were mixed in a mass ratio shown in Table 1, a coupling agent was added, and then the mixture was mixed with a planetary mixer or the like.
The epoxy resin compositions of Examples 1 and 2 and Comparative Example were obtained by stirring, mixing and dispersing.

(Evaluation) A test piece was prepared from the cured product of the epoxy resin composition, and the refractive index and the light transmittance were measured.
[%], Light reflectance [%], and mounting reliability were evaluated, and the results are shown in Table 1.

All the test pieces (both with and without filler) had a mold temperature of 1
The epoxy resin composition was transfer-molded at 50 ° C. for 2 minutes for curing, and then post-cured at 150 ° C. for 2 hours to prepare. With respect to the refractive index, the refractive index of the above test piece (which does not contain a filler) was measured by an Abbe method using a refractive index measuring device.

Further, regarding the light transmittance, an integrating sphere type spectrophotometer (manufactured by Shimadzu Corporation) was used, and 700 to 11 of a 1 mm-thick test piece (containing a filler) was used.
The light transmittance [%] in the wavelength range of 00 nm is calculated, and this is
30 to 85% for ○, 85% or more for ●, 30
Those less than% were defined as x.

Regarding the light reflectance, an integrating sphere type spectrophotometer (manufactured by Shimadzu Corp.) was used to measure a test piece having a thickness of 1 mm (containing a filler) at 700 to 1100 nm.
The light reflectance [%] in the wavelength range of
% Is ◯, 70% or more is ●, and less than 2% is x.

On the other hand, regarding the mounting reliability, the optical pickup PKG (4 mm × 5 mm × 1.8 mm) was used, and a temperature of 85 was applied to the test piece (containing the filler).
After performing a moisture absorption treatment for 20 hours at a temperature of 85 ° C and a humidity of 85%, a reflow test treatment of 260 ° C peak is performed, and the presence or absence of peeling and cracks is confirmed by observing with a microscope to check the number of test pieces having these defects. The percentage of the number of pre-test sample pieces was defined as a defect rate [%], and 0% was ○, less than 5% was Δ, and 5% or more was ×.

[0035]

[Table 1] From the evaluation results of Example 1 in which a melamine-based organic filler was used as the filler in Table 1 and Example 2 in which the PMMA-based organic filler was used as the filler, the above epoxy resin, curing agent, and curing acceleration were obtained. The difference between the refractive index of the cured product composed of the agent and the refractive index of the filler is ± 0.01 or more, and the molded product is composed of the cured product of the epoxy resin composition for optical semiconductor element encapsulation having a thickness of 1 mm. Has a light transmittance of 30 to 85% and a light reflectance of 2 to 70%, and achieves both light transmittance and light diffusivity. Material design of resin composition is possible, and as a result,
It has been clarified that it is possible to secure a sufficient light diffusion property as well as a good light transmission property.

Further, in the epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, by using the above-mentioned melamine-based organic filler in which the filler contains at least a condensation reaction product of melamine and formaldehyde. Of the epoxy resin composition for optical semiconductor element encapsulation by adjusting the refractive index of the filler by examining the components and component ratios of the starting materials in the condensation reaction, or examining the condensation reaction conditions while ensuring the translucency. It has become clear that optimization of light transmission and light diffusion is possible.

Further, in the epoxy resin composition for encapsulating an optical semiconductor element according to the present invention, the filler contains at least the polymerization reaction product of methacrylic acid ester.
By using the MA-based organic filler, while maintaining the light-transmitting property, it is possible to adjust the refractive index of the filler by studying the components and component ratios of the starting materials in the polymerization reaction or by studying the polymerization reaction conditions. It has been clarified that the light transmittance and the light diffusivity of the epoxy resin composition for semiconductor element encapsulation can be optimized.

Therefore, in an optical semiconductor device in which an optical semiconductor element is encapsulated by using the epoxy resin composition for encapsulating an optical semiconductor element of the present invention having such characteristics, good light transmittance and sufficient light diffusion are obtained. It is possible to seal the optical semiconductor device that secures the property, and respond to the above new needs such as application to devices that require not only light transmission but also light diffusion and light interference prevention. It will be possible.

[0039]

As described above, the epoxy resin composition for optical semiconductor element encapsulation according to claims 1 and 2 of the present invention contains an epoxy resin, a curing agent, and a curing accelerator. And an epoxy resin composition for encapsulating an optical semiconductor element, which comprises a filler made of a translucent organic material, wherein the epoxy resin, the curing agent, and the curing accelerator are cured products. And the refractive index of the filler are different, and the difference between the refractive index of the cured material made of the epoxy resin, the curing agent, and the curing accelerator and the refractive index of the filler is ± 0.01. The light transmittance of the molded product made of the cured product of the epoxy resin composition for optical semiconductor element encapsulation having a thickness of 1 mm is 30 to 85% and the light reflectance is 2 to 70%. It is characterized by good translucency and sufficient light. Dispersion of ensuring an excellent effect that it becomes possible.

In the epoxy resin composition for encapsulating an optical semiconductor element according to claim 3, in the epoxy resin composition for encapsulating an optical semiconductor element according to claim 1 or 2, the filler is at least , Which comprises a condensation reaction product of melamine and formaldehyde, so as to secure the translucency, the components of the starting materials and the component ratio in the condensation reaction, or by examining the condensation reaction conditions, etc. By adjusting the refractive index of the filler, it is possible to optimize the light transmittance and light diffusivity of the epoxy resin composition for optical semiconductor element encapsulation.

In the epoxy resin composition for encapsulating an optical semiconductor element according to claim 4, in the epoxy resin composition for encapsulating an optical semiconductor element according to claim 1 or 2, the filler is at least Since it contains a polymerization reaction product of methacrylic acid ester, while ensuring the light-transmitting property, the above-mentioned filling by examining the components and component ratios of the starting materials in the polymerization reaction, or by examining the polymerization reaction conditions, etc. By adjusting the refractive index of the material, it is possible to optimize the light transmittance and the light diffusivity of the epoxy resin composition for optical semiconductor element encapsulation.

The epoxy resin composition for encapsulating an optical semiconductor element according to claim 5 is the epoxy resin composition for encapsulating an optical semiconductor element according to any one of claims 1 to 4. Since the amount of the material added is 0.5 to 30% by mass of the whole epoxy resin composition, it is possible to ensure the translucency, the light diffusivity, and the good molding characteristics. Play.

In the optical semiconductor device according to claim 6,
An optical semiconductor element is encapsulated by using the epoxy resin composition for encapsulating an optical semiconductor element according to any one of claims 1 to 5, so that good optical transparency and sufficient optical transparency can be obtained. The excellent effect that the optical semiconductor device in which the light diffusion property is secured can be sealed is exhibited.

[Brief description of drawings]

FIG. 1 is a sectional view showing a typical embodiment of an optical semiconductor device of the present invention.

[Explanation of symbols]

1 Optical semiconductor device 2 electrodes 3 electrodes 4 metal wire 5 LED chip 6 Epoxy resin composition cured product 7 cases 8 light emitting part

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 33/00 H01L 23/30 F (72) Inventor Takanori Kushida 1048 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Works Ltd. Formula In-house F-term (reference) 4J002 BG052 CC033 CC043 CC053 CC063 CC182 CD021 CD051 CD061 CD141 EL136 EN027 EN107 EU117 EU137 EW177 FD012 FD143 FD146 FD157 GP03 GQ05 HA05 4M109 AA01 BA01 CA21 EA02 EB02 DA01 DA04 EA02 EA04 EB02 EA04 EB02 EA04 EB02 EA04 EB02 EA04 EB02 EA04 EB02 EA04 EB02 EA04 EB02 EA02 EB04 EF02

Claims (6)

[Claims] 1. An epoxy resin composition for optical semiconductor element encapsulation, comprising an epoxy resin, a curing agent, and a curing accelerator, and using a filler made of a light-transmitting organic material. An epoxy resin composition for optical-semiconductor element encapsulation, wherein a refractive index of a cured product composed of the epoxy resin, the curing agent, and the curing accelerator is different from that of the filler. 2. The difference between the refractive index of the cured material composed of the epoxy resin, the curing agent, and the curing accelerator and the refractive index of the filler is ± 0.01 or more, and the thickness is 1 m.
The light transmittance of the molded product made of the cured product of the epoxy resin composition for optical semiconductor element encapsulation of m is 30 to 85%, and the light reflectance is 2 to 70%. An epoxy resin composition for encapsulating an optical semiconductor element as described in the above. 3. The epoxy resin composition for encapsulating an optical semiconductor element according to claim 1 or 2, wherein the filler contains at least a condensation reaction product of melamine and formaldehyde. 4. The epoxy resin composition for optical semiconductor element encapsulation according to claim 1, wherein the filler contains at least a methacrylic acid ester polymerization reaction product. 5. The optical semiconductor element encapsulation according to claim 1, wherein the amount of the filler added is 0.5 to 30% by mass of the whole epoxy resin composition. Epoxy resin composition for use. 6. An optical semiconductor device obtained by encapsulating an optical semiconductor element using the epoxy resin composition for encapsulating an optical semiconductor element according to any one of claims 1 to 5.