JPH062803B2 - Epoxy resin composition - Google Patents

Description

Detailed Description of the Invention [Industrial applications]

The present invention relates to an epoxy resin composition having excellent transparency and heat discoloration resistance, and more specifically, it has excellent colorless transparency and is used for optical applications such as optical lenses, prisms, sealing of light emitting diodes, and light reception. The present invention relates to an epoxy resin composition useful for encapsulating elements, and further for substrates for optical discs such as laser discs and compact discs.

[Prior art]

Generally, an epoxy resin composition has excellent mechanical strength characteristics and electrical insulation characteristics, and further has adhesiveness, chemical resistance, water resistance,
Since it has good heat resistance and the like, it has been widely used for insulation coating of electric / electronic device parts, adhesives, civil engineering and construction. Originally, the epoxy resin causes "burning" of the resin due to the heat generated during curing and is easily colored, 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 coloring can be obtained, and in particular, a method using a strongly basic compound such as diazabicycloalkene as a tertiary amine or a carboxylate thereof has been proposed. There is. In addition, in order to obtain a cured product having no coloration and excellent transparency, for example, a method in which an organic acid metal salt such as tin octylate or zinc octylate and a tertiary amine thereof are used in combination, and an organic phosphine is used as an anticoloring agent A method of adding phytes and hindered phenols and a method of "blueing" in which a trace amount of a blue or purple coloring agent is added have been proposed. These technologies have greatly contributed to improving the functions of small electronic components such as light emitting diodes, photocouplers, and optical signal reading lenses.

[Problems to be Solved by the Invention]

However, according to the conventional technique, for example, 5 mmφ × 8 mm
In comparison with light-emitting diode casting, a colorless and transparent cured product can be obtained without any problem, whereas productivity is increased when a transparent large cured product such as a 300 mmφ x 1.8 mm laser disk substrate is manufactured in a short time. However, it is difficult to obtain a cured product having substantially no color. Further, regarding the discoloration caused by leaving the cured product in a high temperature atmosphere for a long time, a satisfactory epoxy resin composition has not been obtained.

[Means for Solving the Problems]

The inventors of the present invention have conducted research for the purpose of providing an epoxy resin composition which is fast-curing and has excellent transparency that enables casting or molding of a large volume, and as a result, the epoxy resin has an organic polybasic acid. By adding an anhydride-based curing agent and a specific curing accelerator, it was found that an epoxy resin composition having excellent properties of colorless transparency and heat discoloration immediately after curing can be obtained, and the present invention is completed. I arrived. That is, the present invention comprises (a) one or more selected from epoxy resins having an average of one or more epoxy groups in one molecule, (b) organic polybasic acid anhydride compounds and polyhydric phenol compounds. An epoxy resin composition comprising a curing agent composed of a mixture of (1) and (c) a curing accelerator, which achieves the intended purpose by using 1-benzyl-2-phenylimidazole / organic carboxylate as a curing accelerator. Is. The epoxy resin used in the present invention is a colorless or light-colored transparent transparent liquid or solid epoxy resin among known epoxy resins, and typical examples thereof include bisphenol A, bisphenol F, bisphenol AD and Polyglycidyl ether compounds obtained from polyhydric phenols such as novolac resins, polyglycidyl ester compounds obtained from polycarboxylic acids such as phthalic acid and adipic acid, polyglycols obtained from polyhydric alcohols such as polyethylene glycol, polypropylene glycol or glycerin Glycidyl ether compounds, hydrogenated bisphenol A cyglycidyl ethers, alicyclic epoxy resins such as 3,4-epoxycyclohexylmethyl- (3,4-epoxy) cyclohexanecarboxylate,
Examples include trisglycidyl isocyanurate and epoxidized polyolefin, which may be used alone or 2
You may use it in mixture of 2 or more types. If necessary, a low-viscosity monoepoxy compound or the like may be blended as a reactive diluent, or a halogenated epoxy resin may be used to achieve flame retardancy. Examples of the organic polybasic acid anhydride used in the present invention include succinic anhydride, polyadipic anhydride, trimellitic anhydride, and the like, particularly hexahydrophthalic anhydride,
Methylhexahydrophthalic anhydride (the substitution position of the methyl group is arbitrary) is preferable. 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 alone or in combination of two or more. The polyhydric phenol compound used as the curing agent in the present invention is a colorless to light-colored transparent solid novolac resin obtained by polycondensation of a phenol compound and formaldehyde in the presence of an acidic catalyst. As the curing agent used in the present invention, an organic acid anhydride compound and a polyhydric phenol compound may be used alone, or an organic acid anhydride compound and a polyhydric phenol compound may be used in combination. The compounding amount (equivalent ratio) of the curing agent compounded in the epoxy resin is Is preferred. That is, below this value, it becomes a cured product with poor thermal stability that is somewhat colored by long-term heat aging,
On the other hand, above this value, only a cured product with poor moisture resistance can be obtained. Representative examples of the organic carboxylate compound of 1-benzyl-2-phenylimidazole (hereinafter referred to as 1B2PZ) used as a curing accelerator in the present invention include 1B2PZ · monochloroacetate, 1B2PZ · phthalate, 1B2PZ · Trimellitic acid salt, 1B2PZ
Pyromellitate, 1B2PZ, adipate and the like are included, but are not limited thereto. 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. Also useful for maintaining transparency of hindered phenols having radical scavenging action, organic sulfides having peroxide decomposing action, or polyvinyl chloride, which are conventionally used as antioxidants for plastics such as polyolefins for preventing coloration. You may add organic phosphite etc. which are various plasticizers. The hindered phenols used in the present invention include:
Those which are easily soluble in the epoxy resin and the curing agent (organic acid anhydride compound or polyhydric phenol compound), respectively, or those which are compatible with the mixture thereof are preferable, and the representative one is 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-tert-
Butylphenol}, 2,2'-thiobis {4-methyl-
6-tert-butylphenol}, 1,3,5-trismethyl-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, in order to improve the workability of an internal release agent, a lubricant, an antifoaming agent, a leveling agent, a penetrating agent, etc., a commonly used additive is used within a range that does not adversely affect the effects of the present invention. Needless to say, it can be used in. Hereinafter, the present invention will be specifically described with reference to Examples and Comparative Examples.

[Examples and Comparative Examples]

The evaluations in Examples and Comparative Examples were carried out by cutting the cured products obtained by casting or molding into predetermined dimensions to obtain test pieces under the following test standards and conditions. Bending strength JIS K-7203 25 ℃ Bending elastic modulus JIS K-7203 25 ℃ Heat deformation temperature JIS K-7207 2 ℃ / min Volume resistivity JIS K-6911 25 ℃ Volume resistivity after boiling JIS K-6911 1 hour boiling After that, 25 ℃ dielectric constant JIS K-6911 25 ℃, 60Hz dielectric loss tangent JIS K-6911 25 ℃, 60Hz boiling water absorption rate JIS K-7209 after boiling for 1 hour dielectric breakdown voltage JIS K-6911 test variable thickness: 1.5mm 20 ° C. Example 1 100 parts by weight of epoxy resin (epoxy resin manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: AER-331, bisphenol A diglycidyl ether) and 4-methylhexahydrophthalic anhydride (Shin Nippon Rika Co., Ltd.) Acid anhydride, trade name: RIKACID
MH-700) 90 parts by weight of the mixture, 1B2 as a curing accelerator
1 part by weight of PZ / trimellitic acid salt was added and mixed by stirring to prepare a formulation. The above composition was cast into a 5 mmφ × 8 mm polymethylpentene casting mold (size of an ordinary light emitting diode lamp, hereinafter referred to as “mold 1”) and 25 mm × 25 mm × 50.
mm aluminum casting mold (hereinafter referred to as "mold 2")
After pouring so as to satisfy the above conditions, it was heated and cured at a temperature of 120 ° C. for 30 minutes. The obtained cured product is colorless and transparent in both molds 1 and 2,
It could be used for optical applications. Pour the above mixture into a 3 mm thick × 100 mm × 150 mm mold 12
After thermosetting for 60 minutes at a temperature of 0 ° C., it was cut into a predetermined size and various properties were examined. The results are shown below. Flexural strength, 14.2kg / mm ² Flexural modulus, 290kg / mm ² Heat distortion temperature, 143 ℃ Volume resistivity, 9.6x10 ¹⁶ Ω-cm Volume resistivity after boiling, 1.4x10 ¹⁶ Ω-cm Dielectric constant, 60Hz 3.0 Dielectric loss tangent, 60Hz 0.002 Boiling water absorption rate, 0.22% Dielectric breakdown voltage, 24.5 KV / mm Comparative Example 1 In Example 1, 1,8-diazabicyclo (4) was used as a curing accelerator instead of 1B2P.Z.trimellitic acid salt. ,
5,0) Undecene-7 [manufactured by San Abbott Co., Ltd., trade name: DBU] was used to prepare a formulation by the same treatment method as in Example 1, and the formulation was prepared as in Example 1. It was heat-cured by the Pope. The cured product of the mold 1 was colorless and transparent, but the cured product of the mold 2 was scorched black in the central part of the cured product due to the heat generated during curing, and a colorless and transparent product was not obtained. In addition, in order to heat-cure this compound into a colorless and transparent uniform state in the size of the mold 2, it was necessary to heat-cure for 16 hours at a temperature of 60 ° C. and for 3 hours at a temperature of 100 ° C. Examples 2 to 4 and Comparative Examples 2 to 3 An epoxy resin, an organic polybasic acid anhydride, and a curing accelerator were mixed in the proportions shown in Table 1, and the same treatment as in Example 1 was performed. The results are as shown in Table 2. Example 5 100 parts by weight of an epoxy resin (Epoxidized cresol novolac resin manufactured by Asahi Kasei Kogyo Co., Ltd., trade name: AER-ECN-273) and hexahydrophthalic anhydride (an acid anhydride compound manufactured by Shin Nippon Rika Co., Ltd., a product) Name: RIKACID HH) 37 parts by weight, polyphenolic compound (Novolak resin manufactured by Showa Union Gosei Co., Ltd., trade name: Shonor BR-558 26 parts by weight and 1B2PZ / trimellitic acid salt 1 part by weight as a curing accelerator. After mixing, the mixture was kneaded using a hot two-roll machine in which the roll surface temperature was adjusted to 100 ° C. in advance, cooled, and then pulverized to obtain a transfer molding compound. The 80 mmφ × 3 mm disk-shaped cured product obtained by pressure-molding for 2 minutes at the above temperature was colorless and transparent and extremely tough, and was suitable for practical use as an optical disk substrate.

【The invention's effect】

The epoxy resin composition of the present invention is not only excellent in colorless transparency and heat discoloration resistance, but also excellent in workability because it is fast-curing,
Moreover, since it has low heat generation, it is suitable for castings that require relatively large transparency with very little coloring or discoloration.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁵ Identification number Office reference number FI technical display location G11B 7/24 P 7215-5D (56) References JP-A-57-100128 (JP, A) Special features Kai 57-190018 (JP, A) JP 59-27914 (JP, A) JP 60-137046 (JP, A) JP 60-121551 (JP, A)

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, (b) an organic polybasic acid anhydride compound and a polyhydric phenol compound. A curing agent consisting of a mixture of
An epoxy resin composition comprising a curing accelerator, wherein an organic carboxylic acid salt of 1-benzyl-2-phenylimidazole is used as a curing accelerator. 2. The epoxy resin composition according to claim 1, wherein the curing accelerator is 1-benzyl-2-phenylimidazole trimellitate.