JPH062805B2 - Epoxy resin composition - Google Patents

Description

TECHNICAL FIELD The present invention relates to an epoxy resin composition having excellent transparency and thermal discoloration resistance, and more specifically, it has excellent colorless transparency and is used for optical applications such as optical applications. The present invention relates to an epoxy resin composition useful for encapsulating lenses, prisms, light emitting diodes and the like, encapsulating light receiving elements, and substrates for optical disks such as laser disks and compact disks.

2. Description of the Related Art Epoxy resin compositions generally have excellent mechanical strength properties and electrical insulation properties, as well as adhesiveness, chemical resistance, water resistance, and
Since it has good heat resistance, it is widely used for insulation coating of electric / electronic devices and parts, adhesives, civil engineering and construction.

Originally, an epoxy resin is liable to be colored such as "burn" of the resin due to heat generated during curing, so that it is not easy to obtain a colorless and transparent cured product.

In recent years, in a thermosetting resin composition mainly composed of a mixture of an epoxy resin and an organic polybasic acid anhydride-based curing agent, when a specific tertiary amine or an organic acid salt thereof is used as a curing accelerator, It has become widely known that a cured product with relatively little coloration can be obtained, and in particular, a method using a strongly basic compound such as diazobicycloalkene or a carboxylic acid salt thereof as a tertiary amine has been proposed. . Furthermore, in order to obtain a cured product which is more colorless and excellent in transparency, for example, a method of using a combination of the tertiary amine and an organic acid metal salt such as tin octylate or zinc octylate, or an organic phosphite as a coloring inhibitor. There is also proposed a method of adding a soda or a hindered phenol, and a method of performing so-called "blueing" in which a trace amount of a blue or purple coloring agent is added.

These technologies have greatly contributed to improving the functions of small electronic components such as light emitting diodes, photo couplers, and optical signal reading lenses.

However, according to the conventional technique, for example, 5 mmφ × 8 mm
Although a colorless transparent cured product can be obtained without any problem by casting a light emitting diode of about a certain degree, it is said that it is possible to produce a transparent large cured product such as a 300 mmφ × 1.6 mm laser disk substrate in a short time. However, the present situation is that a cured product which is virtually colorless has not been obtained. Further, it cannot be said that the prevention of discoloration caused by leaving the cured product in a high temperature atmosphere for a long time is in a satisfactory state.

Means for Solving the Problem As a result of repeated studies aimed at providing an epoxy resin composition having excellent transparency, which is fast-curing and can be cast or molded with a large capacity, It has been found that an epoxy resin composition having excellent properties of colorless transparency and heat discoloration immediately after curing can be obtained by blending an organic polybasic acid anhydride curing agent and a specific curing accelerator with an epoxy resin. The present invention has been completed based on this finding.

That is, the present invention is (a) one or more kinds selected from an epoxy resin having an average of one or more epoxy groups in one molecule, (b) an organic polybasic acid anhydride compound or a polyhydric phenol compound. In an epoxy resin composition containing the curing agent of (c) and a curing accelerator (3) as essential components,
The initial purpose was achieved by using a 2-aryl group-substituted imidazole hydrohalide as a curing accelerator.

The epoxy resin that can be used in the present invention is a colorless or light-colored transparent transparent liquid or solid epoxy resin among known epoxy resins. Typical examples thereof are polyglycidyl ether compounds obtained from polyphenols such as bisphenol A, bisphenol F, bisphenol AD and novolac resins, and polyglycidyl esters obtained from polycarboxylic acids such as phthalic acid and adipic acid. Compound, polyethylene glycol,
Polyglycidyl ether compounds obtained from polyhydric alcohols such as polypropylene glycol or glycerin, alicyclic epoxy resins, triglycidyl isocyanurate, epoxidized polyolefins, etc., which may be used alone or in combination of two or more. You may use it. Further, if necessary, a low-viscosity monoepoxy compound or the like may be added as a reactive diluent. Further, flame retardation may be achieved by using a halogenated epoxy resin.

The organic polybasic acid anhydride used in the present invention is most preferably hexahydrophthalic anhydride or methylhexahydrophthalic anhydride (the substitution position of the methyl group is arbitrary),
In addition to these, succinic anhydride, polyadipic anhydride, trimellitic anhydride and the like are also suitable. When slight coloration is allowed in the cured product, tetrahydrophthalic anhydride, methyltetrahydrophthalic anhydride (the substitution position of the methyl group is optional), etc. can be used. These organic polybasic acid anhydrides may be used singly or as a mixture of arbitrary several kinds.

The acid anhydride compounded in the epoxy resin preferably has an acid anhydride group / epoxy group (equivalent ratio) ratio of 0.9 to 1.1. That is, below this value, a cured product which is somewhat inferior in thermal stability and is colored by long-term heat aging is obtained, and above this value, only a cured product having poor moisture resistance can be obtained.

Typical examples of the 2-aryl group-substituted imidazole compound / hydrogen halide used as the curing accelerator in the present invention include 2-phenylimidazole / hydrofluoride, 1-benzyl-2-phenylimidazole / chloride. Hydrochloride, 2-phenylimidazole hydrobromide, 1
-Benzyl-2-phenylimidazole, hydroiodide, etc. 2-Methylimidazole / hydrochloride and 2
-Ethyl-4-methylimidazole hydrobromide, 2
-Undecyl imidazole / hydrochloride, etc. can give cured products with good transparency, but these curing accelerators have deliquescent properties and are difficult to handle. Not suitable for insulation applications.

The compounding amount of these curing accelerators should be 0.05 to 5 parts by weight with respect to 100 parts by weight of the epoxy resin.

In carrying out the present invention, a dye or pigment for coloring, a transparent extender pigment for strengthening a cured product, and a light scattering agent (finely divided pigment) for scattering light can be added.

In addition, it is used as an antioxidant for polyolefin plastics to prevent coloration. For example, hindered phenols having a radical scavenging action, organic sulfides having a peroxide decomposing action, or transparent polyvinyl chloride and the like. An organic phosphite ester which is a plasticizer useful for maintaining the sex may be added.

The hindered phenols used in the present invention include:
Epoxy resins and organic polybasic acid anhydrides which are each easily soluble, or those which are compatible with a mixture thereof are preferable, for example, 2,6-di-tert-butylphenol,
2,6-di-tert-butyl-4-methylphenol, 2,2 '
-Methylenebis {4-methyl-6-tert-butylphenol}, 4,4'-butylidenebis {3-methyl-6-ter
t-butylphenol}, 2,2'-thiobis {4-methyl-6-tert-butylphenol}, 1,3,5-trimethyl-2,4,6-tris {3,5-di-tert-butyl-4 -Hydroxybenzyl} benzene and the like.

Examples of the organic sulfides used in the present invention include thiodipropionic acid diesters, and diesters of aliphatic higher alcohols having 4 to 18 carbon atoms are particularly preferable.

In curing the resin composition of the present invention, a release agent,
In order to improve the workability of internal mold release agents, lubricants, defoaming agents, leveling agents, penetrating agents, etc., these additives can be used within a range that does not adversely affect the effects of the present invention.

Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

Examples and Comparative Examples Evaluations in Examples and Comparative Examples were performed by cutting the cured products obtained by casting or molding into predetermined dimensions to prepare test pieces, and performing the following test standards and conditions.

Bending strength JIS K-7203 25 ℃ Flexural modulus JIS K-7203 25 ℃ Heat deformation temperature JIS K-7207 2 ℃ / min Volume resistivity after boiling JIS K-6911 Volume resistivity after boiling for 1 hour JIS K-6911 25 Dielectric constant JIS K-6911 25 ° C, 60Hz Dielectric loss tangent JIS K-6911 25 ° C, 60Hz Water absorption of boiling water JIS K-7209 Dielectric breakdown voltage after boiling for 1 hour JIS K-6911 Test thickness change: 1.5mm, 20 ° C Example 1 100 parts by weight of epoxy resin [epoxy resin manufactured by Asahi Chemical Industry Co., Ltd., trade name: AER-331, bisphenol A diglycidyl ether] and 4-methylhexahydrophthalic anhydride [acid anhydride manufactured by Nippon Rika Co., Ltd.] , Product Name: RIKACID MH
-700] 90 parts by weight was mixed with 1 part by weight of 1-benzyl-2-phenylimidazole hydrobromide as a curing accelerator, and mixed by stirring to obtain a formulation.

A 5 mmφ × 8 mm polymethylpentene casting mold (size of a normal light emitting diode lamp, hereinafter referred to as “mold 1”) and a 25 mm × 25 mm × 50 mm aluminum casting mold (hereinafter “ Mold 2 ”) and then heated at 120 ° C. for 30 minutes to cure.

The obtained cured product was colorless and transparent in both molds 1 and 2, and was usable for optical applications.

Comparative Example 1 100 parts by weight of the same epoxy resin as used in Example 1 and 90 parts by weight of 4-methylhexahydrophthalic anhydride were mixed, and 1,8-diazobicyclo (4,5,4) was added as a curing accelerator. , 0) Undecen-7 [manufactured by San Abbott Co.,
Brand name: DBU] 1 part by weight is added, the mixture obtained by performing the same treatment is cast into the mold 1 and the mold 2 similar to those in Example 1, and then they are heated and cured at a temperature of 120 ° C. for 30 minutes respectively. It was

The obtained cured product was colorless and transparent in the case of the mold 1, but the mold 2 was not ready for use because the center of the interior of the cured product was burnt black because of the heat generated during curing.

It should be noted that, in order to heat cure this preparation into a colorless and transparent state in the size of the mold 2, it should be heated at 60 ° C for 16 hours and then at 100 ° C for 3 hours.
Heat treatment for hours was required.

Example 2 A formulation obtained as in Example 1 was prepared as 3 mm thick x 100 mm x 150
It was poured into a mold of mm and heat-cured at a temperature of 120 ° C. for 30 minutes, and then cut into predetermined dimensions, and various properties were examined. The results are shown below.

Bending strength 14.6 kg / mm ² Flexural modulus 320 kg / mm ² Heat deformation temperature 140 ℃ Volume resistivity 8.3 × 10 ¹⁶ Ω−cm Volume resistivity after boiling 1.6 × 10 ¹⁶ Ω−cm Dielectric constant, 60 Hz 3.0 Dielectric loss tangent , 60Hz 0.002 Boiling water absorption rate 0.24% Dielectric breakdown voltage 28.8KV / mm Examples 3-5 and Comparative Examples 2-3 Epoxy resin, organic polybasic acid anhydride and curing accelerator were mixed in the proportions shown in Table 1. When the same treatments as those in Examples 1 and 2 were performed, the test results were as shown in Table 2.

Example 6 100 parts by weight of an epoxy resin [epoxidized cresol novolac resin manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: AER-ECN-273], hexahydrophthalic anhydride [an acid anhydride compound manufactured by Shin Nippon Rika Co., Ltd., a commercial product] Name: RIKACID HH] 37 parts by weight, polyhydric phenol compound [Novolak resin manufactured by Showa Union Gosei Co., Ltd., trade name: Shonor BR-558] 26 parts by weight, and 1-benzyl-2-phenylimidazole as a curing accelerator. After 1 part by weight of hydrobromide was powder-mixed, it was kneaded using a hot two-roll mill, cooled and pulverized to obtain a transfer molding composition.

The 80 mmφ × 3 mm disk-shaped cured product obtained by press-molding the above-mentioned composition with a transfer molding machine at a temperature of 150 ° C. for 2 minutes is colorless and transparent and extremely strong, and is suitable for an optical disk substrate. Admitted.

EFFECTS OF THE INVENTION The epoxy resin composition of the present invention is not only excellent in colorless transparency and heat discoloration resistance, but also excellent in workability due to its rapid curing property, and as a relatively large cast product due to low heat generation. Even when used, there is very little coloring or discoloration.

Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI Technical display location G11B 7/24 P 7215-5D

Claims (2)

[Claims] 1. One or more selected from (a) an epoxy resin having an average of one or more epoxy groups in one molecule, and (b) an organic polybasic acid anhydride compound or a polyhydric phenol compound. In the epoxy resin composition containing the curing agent of (3) and the curing accelerator (c) as essential components, a hydrohalide of a 2-aryl group-substituted imidazole compound is used as a curing accelerator. Epoxy resin composition. 2. As a curing accelerator, 1-benzyl-2-phenylimidazole hydrofluoride, hydrogen chloride,
The epoxy resin composition according to claim 1, wherein one or more compounds selected from hydrobromide and hydroiodide are used.