Epoxy resins are excellent in heat resistance, adhesiveness, water resistance, mechanical strength, electrical properties and the like, and therefore are used in various fields. Particularly, in electric and electronic fields, epoxy resins are widely used in insulating casting, laminating materials, encapsulating materials and the like. However, in recent years, in accordance with miniaturization, precision and high performance of electric and electronic parts, moldability, high moisture resistance and high electrical properties are required also in epoxy resins used.

For example, recently, packaging of LSI has a tendency of high density and thin package due to progress in portable instruments such as IC cards, LCD, portable telephones and notebook computers, and the packaging method is shifting from conventional transfer molded package into that of mounting bare chips and encapsulating it with a liquid encapsulant, that is, a so-called COB (chip on board) or TAB.

Conventionally, as epoxy resin curing agents used in liquid encapsulation, amine type curing agents such as dicyandiamide, imidazoles or dihydrazide compounds, or

acid anhydride type curing agents such as tetrahydrophthali anhydride, hexahydrophthalic anhydride or methylhexahydrophthalic anhydride have been the main current. However, liquid encapsulants comprising an epoxy resin composition using the conventional amine type or acid anhydride type curing agent are poor in moisture resistance as compared with transfer molding materials using phenol novolak resin or the like, and therefore are poor in total reliability as encapsulants. For this reason, reliability improvement of liquid encapsulants has been demanded.

In order to obtain an epoxy resin composition having excellent properties in moisture resistance, a method of using an acid anhydride together with phenol novolak resin (see JP-A-4-68019, JP-A-4-132727) and a method of using a low molecular weight phenol type curing agent having at least three phenolic hydroxyl groups in an aromatic ring (see JP-A-6-128360) are proposed. However, because the former method uses an acid anhydride that is poor in moisture resistance, substantial improvement effect is small, and in particular, there is the problem because hydrolysis proceeds aggressively in a pressure cooker test. Because the latter uses a phenol compound that is highly crystalline with a high melting point, the phenol compound is difficult to dissolve in the epoxy resin and also is easy to crystallize. As a result, there are problems that heterogeneous cured product is formed, and package cracks occur.

Further, as an example of the alkenyl phenol compound as a curing agent, a liquid diallyl-substituted bifunctional compound obtained from bisphenol A is known.

Furthermore, a polyalkenyl-substituted polyphenol compound used as a curing agent of maleimide is proposed (see JP-A-2-91113). However, when the former compound is used as a curing agent of epoxy resin, cross-linking

reaction does not proceed because of being bifunctional, and heat resistance of a cured product obtained becomes very low. For this reason, there is the problem in using it as a curing agent of epoxy resin. The latter is solid at room temperature, and handling property is poor for use as a curing agent of liquid encapsulant. Thus, the latter is improper.

The present invention provides an epoxy resin composition that has solved the above-mentioned problems and can give a cured product having excellent balance between moisture resistance and heat resistance and, particularly, provides an epoxy resin composition which is very useful as a liquid resin composition for semiconductor encapsulation.

As a result of extensive investigations on the liquid phenol compound, the present inventors have found that an epoxy resin composition using as a curing agent an alkenyl phenolic resin that contains a polyalkenyl- substituted polyphenol compound and a dialkenyl- substituted bifunctional phenol compound, is excellent in handling property because of it being liquid, and that a cured product excellent in moisture resistance and heat resistance can be obtained therefrom.

The present invention relates to an epoxy resin composition comprising the following component A and component B.

Component A: an epoxy resin having at least two epoxy groups in one molecule, Component B: An alkenyl phenolic resin containing 50-99% by weight of a polyalkenyl-substituted polyphenol compound represented by the formula (1)

(where RI and R2 each represent a hydrogen atom, a halogen atom or an alkyl group having 1-4 carbon atoms, R3 and R4 each represent a hydrogen atom, an alkyl group having 1-4 carbon atoms or an alkoxy group having 1-4 carbon atoms, Y represents an alkenyl group and n is a number of 0-20), and 1-50% by weight of a dialkenyl- substituted bifunctional phenol compound.

A preferred epoxy resin composition is that one in which 5-150 parts by weight of the alkenyl phenolic resin of the component B is blended in per 100 parts by weight of the epoxy resin of the component A.

A more preferred embodiment of said epoxy resin composition is that one in which the component A is a liquid epoxy resin at 25 °C selected from a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a naphthalene type epoxy resin, a glycidyl amine type epoxy resin, an aliphatic epoxy resin and an alicyclic epoxy resin.

More preferred are epoxy resin compositions, in which the polyalkenyl-substituted polyphenol compound represented by the formula (1) and contained in the component B is a compound where Rl, R2, R3 and R4 are all hydrogen atoms and Y is an allyl group in the formula (1).

More preferred are epoxy resin compositions, in which the polyalkenyl-substituted polyphenol compound represented by the formula (1) in the alkenyl phenolic

resin is a polyalkenyl-substituted polyphenol compound containing 50-100% by weight of a component of n=0 in the formula (1).

More preferably the dialkenyl-substituted bifunctional phenol compound is a diallyl substituted compound of any one of bisphenol A, bisphenol F and naphthalene diol.

It will be appreciated that the hereinbefore mentioned alkenyl phenolic resin and a curing accelerator are blended in an amount of 5-150 parts by weight and an amount of 0.01-10 parts by weight, respectively, per 100 parts by weight of the epoxy resin.

Most preferred are epoxy resin compositions, wherein the curing accelerator is a compound selected from tertiary amines, imidazoles and organophosphines.

Component A: Epoxy resin General epoxy resins are used as an epoxy resin having at least two epoxy groups in one molecule, which is a component A in an epoxy resin composition of the present invention. Examples of usable epoxy resin include the following materials.

Aromatic diglycidyl ethers: Diglycidyl ether of bisphenol A, diglycidyl ether of bisphenol F, diglycidyl ether of 3,3', 5,5'-tetramethyl bisphenol A, diglycidyl ether of 3,3', 5,5'-tetramethyl bisphenol F, diglycidyl ether of bisphenol S, diglycidyl ether of dihydroxyphenyl ether, diglycidyl ether of biphenol, diglycidyl ether of 3,3', 5,5'-tetramethyl biphenol, diglycidyl ether of naphthalene diol, and the like.

Multifunctional epoxies: A phenol novolak type epoxy resin, a cresol novolak type epoxy resin, a naphthol novolak type epoxy resin, a novolak epoxy resin of bisphenol A, an epoxy resin

obtained from triphenol methane, an epoxy resin obtained from tetraphencl ethane, and the like.

Others: Glycidyl esters obtained from phthalic acid, hexahydrophthalic acid, dimer acid or the like, glycidyl amines obtained from aminophenol, diaminodiphenyl methane or the like, aliphatic epoxies obtained from 1,4- butanediol, 1, 6-hexanediol or the like, alicyclic epoxies obtained from cyclohexane dimethanol, hydrogenated bisphenol A or the like, cycloaliphatic epoxies obtained from cycloolefin such as 3,4-epoxycyclohexylmethyl-3', 4'- epoxycyclohexanecarboxylate, and peracetic acid, and the like.

Of those, liquid epoxy resins at 25 °C selected from a bisphenol A type epoxy resin, a bisphenol F type epoxy resin, a naphthalene type epoxy resin, a glycidyl amine type epoxy resin, an aliphatic epoxy resin and an alicyclic epoxy resin are preferable from the point that workability is improved when used as a liquid encapsulant.

Component B: alkenyl phenolic resin The alkenyl phenolic resin that is a component B in the epoxy resin composition of the present invention functions as a curing agent of the epoxy resin of the component A, and contains 50-99% by weight of a polyalkenyl-substituted polyphenol compound represented by the formula (1)

(where R1 and R2 each represent a hydrogen atom, a halogen atom or an alkyl group having 1-4 carbon atoms, R3 and R4 each represent a hydrogen atom, an alkyl group having 1-4 carbon atoms or an alkoxy group having 1-4 carbon atoms, Y represents an alkenyl group and n is a number of 0-20), and 1-50% by weight of a dialkenyl- substituted bifunctional phenol compound.

Polyalkenyl phenol compound: The polyalkenyl-substituted polyphenol compound of the formula (1) is produced as an oligomerization product mainly comprising trinuclides in which n=0 in the formula (2) mentioned below that is obtained by heating 1 mol of hydroxybenzaldehyde compound and excess phenol compound at 80-200 °C in the presence of an acidic catalyst, and by subsequent dehydration-condensing.

The polyalkenyl-substituted polyphenol compound of the formula (1) can be produced as follows.

The polyphenol compound represented by the formula (2) is reacted with an alkali metal such as sodium hydroxide or potassium hydroxide in water or an alcohol solvent to obtain a phenolate corresponding to the respective phenol compound. A halogenated alkenyl such as allyl chloride, allyl bromide, methallyl chloride, methallyl bromide, 1-propenyl chloride or 1- propenyl bromide is then added to the reaction mixture, and condensation reaction is conducted at a temperature of 40-120 °C for 1-10 hours to obtain alkenyl ether of the polyphenol compound of the formula (2).

After completion of the reaction, salts by-produced are washed with water or the like to be removed, and purification is conducted. Claisen rearrangement reaction is then conducted at a temperature of 130-250 °C for 1-20 hours to obtain a polyalkenyl-substituted product of the polyphenol compound represented by the formula (2).

(where R1, R2, R3, R4 and n are the same as defined above).

Dialkenyl-substituted bifunctional phenol compound: Further, the dialkenyl-substituted bifunctional phenol compound that can be used as the component B together with the polyalkenyl-substituted polyphenyl compound of the formula (1) can be produced as follows.

Similar to the case of the production of the polyalkenyl-substituted polyphenol compound of the formula (1), bifunctional phenol as a raw material is reacted with an alkali metal such as sodium hydroxide or potassium hydroxide in water or an alcohol solvent to obtain a phenolate corresponding to the bifunctional phenol compound. A halogenated alkenyl such as allyl chloride, allyl bromide, methallyl chloride, methallyl bromide, 1-propenyl chloride or 1-propenyl bromide is then added to the reaction mixture, and condensation reaction is conducted at a temperature of 40-120 °C for 1-10 hours to obtain dialkenyl ether of the bifunctional phenol. Salts by-produced are thereafter washed with water or the like to be removed, and purification is conducted. Claisen rearrangement reaction is then conducted at a temperature of 130-250 °C for 1-20 hours to obtain a polyalkenyl-substituted polyphenol compound.

As the alkenyl phenolic resin that is component B in the epoxy resin composition of the present invention, the polyalkenyl-substituted polyphenol compound represented by the formula (1) and the dialkenyl-substituted bifunctional phenol may be used after being produced separately and mixed in appropriate proportions, as mentioned above.

However, it is preferable from the point that a liquid alkenyl phenolic resin is obtained, to use a mixture of the polyalkenyl-substituted polyphenol compound represented by the formula (1) and the dialkenyl-substituted bifunctional phenol, the mixture prepared by using a mixture of the polyphenol compound of the formula (2) and the bifunctional phenol compound as raw materials, by conducting the same alkenyl etherification reaction as mentioned above, and by conducting subsequently Claisen rearrangement reaction.

The polyalkenyl-substituted polyphenol compound represented by the formula (1) obtained by the above reaction is preferred when Rl, R2, R3 and R4 are all hydrogen atoms and Y is an allyl group, from the points that raw materials in producing the polyalkenyl- substituted polyphenol compound are readily available and that an epoxy cured product having excellent heat resistance is obtained.

Further, it is preferable to use the polyalkenyl- substituted polyphenol compound represented by the formula (1) and containing 50-100% by weight of the component of n=0 from the point that viscosity of the alkenyl phenol resin can be further decreased.

If the amount of the polyalkenyl-substituted polyphenol compound represented by the formula (1) is less than 50% by weight in the alkenyl phenol resin, heat resistance of epoxy cured product becomes lower, which is

not preferable. urther, if the amount exceeds 99% by weight, the alkenyl phenolic resin is not present in the form of a liquid, and handling property becomes poor when using it as a liquid encapsulant, which is not preferable.

Examples of the dialkenyl-substituted bifunctional phenol compound that can be added to the alkenyl phenolic resin of component B that can be obtained by the above- mentioned reaction include dialkenyl substituted materials of bisphenol A, dialkenyl substituted materials of bisphenol F, dialkenyls of naphthalene diol, dialkenyl substituted materials of bisphenol S, dialkenyl substituted materials of thiodiphenol, dialkenyl substituted materials of biphenol, dialkenyl substituted materials of hydroquinone, dialkenyl substituted materials of resorcin, dialkenyl substituted materials of catechol, dialkenyl substituted materials of terpene diphenol and dialkenyl substituted materials of diphenol ether.

Of those, dialkenyl substituted materials of bisphenol A, dialkenyl substituted materials of bisphenol F and dialkenyl substituted materials of naphthalene diol are preferable in the points that raw materials are easily available, low viscosity alkenyl phenol resins are obtained, and a cured product having excellent heat resistance is obtained.

In the case of using bisphenol F as the bifunctional phenol compound in the case of producing the dialkenyl- substituted bifunctional phenol compound by the above- mentioned reaction, a polyphenol compound represented by the following formula (3) may be contained in a proportion of 50% by weight or less in bisphenol F. The polyphenol compound of the formula

wherein n is a number in the range of from 1 to 20, and preferably from 1 to 10, is converted into the corresponding polyalkenyl-substituted material by the above-mentioned reaction.

Further, the blending proportion of the epoxy resin of component A and the alkenyl phenolic resin of component B is such that the alkenyl phenolic resin of component B falls within a range of 5-150 parts by weight, preferably 20-120 parts by weight, per 100 parts by weight of the epoxy resin of component A. If the blending proportion is outside this range, the balance between heat resistance and moisture resistance of the epoxy resin cured product deteriorates, which is not preferable.

For the purpose of accelerating curing, a curing accelerator can be blended with the epoxy resin composition of the present invention. Preferable examples of the curing accelerator to be blended include the following materials.

Tertiary amines: Tri-n-butylamine, benzyldimethylamine, 2,4,6-tris (di- methylaminomethyl) phenol, 1,8-diazabicyclo (5,4,0)-unde- cene-7,1,5-diazabicyclo (4,3,0) nonen-7, salts thereof, and the like.

Imidazoles: 2-Methyl imidazole, 2-ethyl-4-methyl imidazole, 1- benzyl-2-methyl imidazole, 2-undecyl imidazole, 2-phenyl imidazole, salts thereof, and the like.

Organophosphines : Tributyl phosphine, tricyclohexyl phosphine, triphenyl phosphine, tris (dimethoxyphenyl) phosphine, salts thereof, and the like.

Those curing accelerators may be used alone, but can also be used as a mixture of two kinds or more.

The amount of the curing accelerator used is 0.01-10 parts by weight, preferably 0.05-5 parts by weight, per 100 parts by weight of the epoxy resin of component A.

If the amount of curing accelerator is less than 0.01 part by weight, cure accelerating effect of the epoxy resin of the present invention is small, and if the amount exceeds 10 parts by weight, water resistance of a cured product becomes poor, which is not preferable.

If necessary, the following components can be added to the epoxy resin composition of the present invention.

Powdery reinforcements or fillers, such as metal oxides (e. g., aluminum oxide, magnesium oxide or the like), metal carbonates (e. g., calcium carbonate, magnesium carbonate or the like), silicon compounds (e. g., diatomaceous earth powder, basic magnesium silicate, calcined clay, silica fine powder, fused silica, crystalline silica or the like), metal hydroxides (e. g., aluminum hydroxide) kaolin, mica, ground quartz, graphite, molybdenum disulfide, and the like; fibrous reinforcements or fillers, such as glass fibers, ceramic fibers, carbon fibers, alumina fibers, silicon carbide fibers, boron fibers, polyester fibers, polyamide fibers, and the like.

Those are blended in an amount of 10-900 parts by weight per 100 parts by weight of the sum of the epoxy resin and the curing agent.

Additionally, there are coloring materials, pigments and flame retardants, such as titanium dioxide, iron black, molybdenum red, Prussian blue, ultramarine blue,

cadmium yellow, cadmium red, antimony trioxide, red phosphorus, bromo compounds, triphenylphosphate, and the like.

Those are blended in an amount of 0.1-20 parts by weight per 100 parts by weight of the sum of the epoxy resin and the curing agent.

Further, for the purpose of improving properties of the resin in final coating film, adhesive layer, molded article or the like, various curable monomers, oligomers and synthetic resins can be blended. Examples thereof include epoxy resin diluents such as monoepoxy compound, maleimides, cyanic acid esters, alkyd resins, melamine resins, fluorine resins, acrylic resins, silicone resins, polyester resins, and others that are used alone or as mixtures of two kinds or more thereof. The blending proportion of those resins is an amount that does not impair the inherent properties of the resin composition of the present invention, that is, preferably 50 parts by weight or less per 100 parts by weight of the sum of the epoxy resin and the curing agent.

Examples of blending means of the epoxy resin, the alkenyl phenolic resin and optional components in the present invention include heat-melt mixing, melt kneading with rolls or kneaders, wet mixing using an appropriate organic solvent and dry mixing.

The present invention is explained in more detail with reference to the Examples and Comparative Examples, however without restricting its scope to these specific embodiments. In each example, parts means parts by weight.

EXAMPLES Production Example 1 of Alkenyl Phenolic Resin (Component B)

263 g of a polyphenol compound (R1=R2=R3=R4=H in the formula (1), containing 95% by weight of the component of n=0, the remainder being the components of n=1 and 2) obtained by dehydration condensation reaction of 1 mol of p-hydroxybenzaldehyde and 10 mols of phenol, 30 g of a phenolic resin containing 90% by weight of bisphenol F (the remainder being the components of n=1 and 2 in the formula (3), a product of Mitsui Chemical Inc.) and 730 g of isopropyl alcohol were charged into a 2 liters four- necked flask equipped with a stirrer and a thermometer, and were dissolved by stirring to form a uniform solution. Next, 120 g of 48.5 wt% sodium hydroxide was added dropwise at a temperature of 25-40 °C to obtain the corresponding sodium phenolate. 242 g of allyl chloride was then added to the reaction system, and condensation reaction was conducted at a reflux temperature (50-80 °C) of allyl chloride for 5 hours to obtain a polyallylphenyl ether compound.

After completion of the reaction, isopropyl alcohol was distilled off at a temperature of 130 °C under reduced pressure, and 800 g of methyl isobutyl ketone was then added and dissolved. Subsequently, after washing with 250 g of pure water four times, methyl isobutyl ketone was distilled off, and Claisen rearrangement reaction was conducted at a temperature of 180 °C for 7 hours under nitrogen stream to obtain 406 g of reddish brown liquid allyl phenolic resin. This allyl phenolic resin was a mixture of 90% by weight of a polyallyl- substituted polyphenol compound and 9% by weight of a diallyl phenol compound, and had a viscosity of 35 Pa s at 30 °C and a hydroxyl equivalent of 158 (g/eq.).

Production Example 2 of Alkenyl Phenolic Resin: 415 g of a reddish brown liquid allyl phenolic resin was obtained by conducting the same procedure as in

Production Example 1 above except for using as the polyphenol compound 270 g of polyphenol compound (R1=R2=R3=R4=H in the formula (2), containing 73% by weight of the component of n=0, the remainder being the components of n=1 and 2) obtained by dehydration condensation reaction of 1 mol of salicylaldehyde and 10 mols of phenol, and 34 g of bisphenol A (a product of Mitsui Chemical Inc.).

This allyl phenolic resin was a mixture of 91% by weight of a polyallyl-substituted polyphenol compound and 9% by weight of a diallyl-substituted bifunctional phenol compound, and had a viscosity of 41 Pa s at 30 °C and a hydroxyl equivalent of 163 (g/eq.).

Comparative Production Example 1 of Alkenyl Phenolic Resin: 400 g of a reddish and blackish brown solid allyl phenolic resin was obtained by conducting the same procedure as in Production Example 1 above except for using as the polyphenol compound 292 g of polyphenol compound (R1=R2=R3=R4=H in the formula (2), containing 95% by weight of the component of n=0, the remainder being the components of n=1 and 2) obtained by dehydration condensation reaction of 1 mol of p-hydroxy- benzaldehyde and 10 mols of phenol.

This allyl phenolic resin contained 100% by weight of a polyallyl-substituted polyphenol compound, was a solid having a softening temperature of 55 °C and had a hydroxyl equivalent of 166 (g/eq.).

Comparative Production Example 2 of Alkenyl Phenolic Resin: 451 g of a polyallyl phenolic resin composed of a yellowish brown liquid diallyl-substituted bifunctional phenol compound was obtained by conducting the same

procedure as in Production Example 1 above except for changing the polyphenol content to 336 g of bisphenol A.

This polyallyl phenolic resin had a viscosity of 1 Pa s at 30 °C and a hydroxyl equivalent of 162 (g/eq.).

Example 1 100 parts of diglycidyl ether of bisphenol A (EPIKOTE 828 EL; trade name of Yuka Shell Epoxy K. K., epoxy equivalent 186 g/eq.) and 85 parts of the allyl phenolic resin obtained by Production Example 1 were mixed at a temperature of 60 °C. After defoaming, a uniform solution was prepared. 1 part of triphenyl- phosphine was added, and the mixture was mixed by stirring to obtain a liquid epoxy resin composition.

The composition was poured into a mold and cured at 100 °C for 4 hours and then at 150 °C for 6 hours in an oven to obtain a cured product. Physical properties of this cured product are shown in Table 1.

Examples 2-6 and Comparative Examples 1-2 Compositions were obtained by conducting the same procedure as in Example 1 except for changing the epoxy resin and the alkenyl phenolic resin as shown in Table 1, and cured products were obtained. Physical properties of those cured products are shown in Table 1.

Table 1 Example Example Example Example Example Example Compara-Compara- 1 2 3 4 5 6 tive tive Example Example 1 2 *4 *5 *6 The The The The same Epoxy Resin E828EL same as E807 same as E154 same as E828EL as the 100 the 100 the 100 the 100 left parts left parts left parts left parts 100 100 100 100 parts parts parts parts Compara-Compara- AlkenylProduc-Produc-Produc-Produc-Produc-Produc-tive tive Phenolic tion tion tion tion tion tion Produc-Produc- Resin Example Example Example Example Example Example tion tion 1 2 1 2 1 2 Example Example 85 88 92 95 90 93 1 2 parts parts parts parts parts parts 89 parts 87 parts Table 1 (continued) example example Example Example Example Example Compara-Compara- 1 2 3 4 5 6 tive tive Example Example 1 2 *7 The *8 The The The same The same Curing TPP same as EMI24 same as TPP same as as the as the Accelerator 1 part the 1 part the 1 part the left left left left left 1 part 1 part 1 part 1 part 1 part Gelation Time *1 160 165 138 140 132 140 150 > 600 (sec) Curing 100 °C, 4 hours + 150 °C, 6 hours Conditions Glass-*2 Transition 82 80 77 76 110 107 87 < 25 Temperature (°C) a<BR> o<BR> Q EH Example Example Example Example Example Example Compara-Compara- 1 2 3 4 5 6 tive tive Example Example 1 2 Moisture *3 Absorption 1.3 1.2 1.2 1.2 1.5 1.4 1.8 3.3 (%) *1 : Hot plate method, gelation time at temperature of 170 °C<BR> *2: TMA method, temperature rising at 5 °C/min<BR> *3: Increasing ratio from an initial weight after storage for 100 hours under conditions<BR> of 130 °C and relative humidity 100%<BR> *4: Bisphenol A type epoxy resin (trade name of Yuka Shell Epoxy K. K.)<BR> *5: Bisphenol F type epoxy resin (trade name of Yuka Shell Epoxy K. K.)<BR> *6: Phenol novolak type epoxy resin (trade name of Yuka Shell Epoxy K. K.)<BR> *7: Triphenylphosphine<BR> *8: 2-Ethyl-4-methylimidazole (trade name of Yuka Shell Epoxy K. K.)

The epoxy resin composition of the present invention uses a novel liquid alkenyl phenolic resin as a curing agent, and an epoxy resin cured product obtained by curing the same with the curing agent is a cured product having well-balanced heat resistance and moisture resistance. Therefore, the composition can be applied to various uses, and in particular can advantageously be used for applications in electric and electronic fields of a liquid semiconductor encapsulant or the like.