JPH08245858A - Epoxy resin composition - Google Patents

Abstract

PURPOSE: To obtain an epoxy resin composition reduced in stress and excellent in mechanical properties and heat resistance by mixing a composition mainly consisting of an epoxy resin, a curing agent and an inorganic filler with an A-B type block copolymer. CONSTITUTION: This epoxy resin composition mainly consists of an epoxy resin, a curing agent and an inorganic filler and an A-B type block copolymer composed of a polymer block A comprising recurring units of formula I and recurring units of formula II and a polymer block B comprising recurring units of formula III and recurring units of formula IV. In the formula, R is H or methyl; and n is 1-12, provided that the case in which n=4 is excluded when R is H. The weight-average molecular weight (in terms of styrene) of A-B type copolymer is 50,000-200,000. When the weight - average molecular weight is below 50,000 or above 200,000, the effect of reducing stress is insufficient.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is excellent in mechanical properties and heat resistance under low stress (that is, in a state where internal stress due to thermal causes is relaxed), and is used for adhesives, paints, electric / electronic parts. The present invention relates to an epoxy resin composition suitable for use in the above.

[0002]

BACKGROUND OF THE INVENTION Epoxy resin is widely used as a highly reliable insulating material for sealing and impregnating electronic and electrical parts such as diodes, transistors and integrated circuits because it has excellent electrical insulation and mechanical properties. ing. In particular, for sealing semiconductor devices, epoxy resin is used instead of the conventional hermetic seal method using glass, metal, or ceramic to improve the above-mentioned physical properties, productivity, and manufacturing cost. The main focus is resin encapsulation.

However, due to the trend toward larger element sizes in recent years due to the higher performance of semiconductor elements, the stress on the element during sealing molding, which has not been a problem in the past, that is, heat in the mounting process such as soldering The problem of internal stress caused by the has come to have an important influence on the reliability of semiconductors. That is, there is a problem that the semiconductor chip is damaged by internal stress due to heat, or peeling occurs at the interface between the chip and the resin.

Internal stress is generally proportional to the product of the coefficient of linear expansion and the elastic modulus. In order to reduce the linear expansion coefficient, a method of adding an inorganic filler has been proposed.

On the other hand, in order to reduce the elastic modulus, a method of adding a silicon compound such as silicone oil or silicone rubber, or urethane rubber or butadiene rubber is proposed [Journal. Adhesion "J. Adhesion"
33, p. 19 (1990)].

Further, an acrylonitrile-butadiene copolymer having good compatibility with an epoxy resin (for example, manufactured by BF Goodrich "BF Goodrich", trade name: Hiker "Hycar" CTBN 13).
00X13) is also proposed as a method of blending as a stress reducing agent [Composite. Science. Technology "Comp
s. Sci. , Technol. 31: 179 (1988)]. However, since the compatibility with the epoxy resin is too high, the high glass transition temperature and the mechanical strength which are the characteristics of the epoxy resin itself are impaired. In addition, the addition of synthetic rubber causes a problem that the crosslink density at the time of curing is lowered, so that there is a problem that the heat resistance is lowered, and in reality, a resin composition satisfying all the properties has not been obtained.

[0007]

However, the method of adding the above-mentioned inorganic filler to the epoxy resin has a problem that mechanical strength, fluidity, moisture resistance and the like are deteriorated when a large amount is blended. In addition, the method of adding the silicon compound or rubber to the epoxy resin has a problem that these stress-reducing agents have poor compatibility with the epoxy resin and bleed at the time of curing to reduce the adhesion with the lead frame or the semiconductor element. was there. Furthermore, the method of blending the acrylonitrile-butadiene copolymer has a result that the high glass transition temperature and the mechanical strength which are the characteristics of the epoxy resin itself are impaired because the compatibility with the epoxy resin is too high. In addition, the addition of synthetic rubber causes a problem that the crosslink density at the time of curing is lowered, so that there is a problem that the heat resistance is lowered, and in reality, a resin composition satisfying all the properties has not been obtained.

[0008] In view of the above, an object of the present invention is to provide an epoxy resin composition capable of suppressing bleeding at the time of curing and reducing stress without deteriorating the mechanical properties and heat resistance of the cured product. is there.

[0009]

The present invention provides a composition (1) containing an epoxy resin, a curing agent and an inorganic filler as main components.
(Hereinafter abbreviated as composition (1)), the general formula (1)

Embedded image And a polymer unit represented by the general formula (2)

[Chemical 6] (In the formula, R is hydrogen or a methyl group, and n is an integer of 1 to 12. However, when R is hydrogen, n = 4 is excluded.) And the general formula (3)

[Chemical 7] And a polymer unit represented by the general formula (4)

Embedded image The present invention relates to an epoxy resin composition comprising an AB type block copolymer composed of a polymer unit B represented by and a polymer portion B formed from the polymer unit B.

Various known epoxy resins can be used as the epoxy resin in the composition (1) used in the epoxy resin composition of the present invention, and the molecular structure thereof can be any one having at least two epoxy bonds in the molecule. The molecular weight is not particularly limited. Examples thereof include bisphenol A type epoxy resin, phenol novolac type epoxy resin, cresol novolac type epoxy resin, and the like, and those having less impurities and hydrolyzable chlorine are preferable. The proportion of the epoxy resin in the composition (1) is 5 to 90% by weight, preferably 15 to
It is 70% by weight. If it is less than 5% by weight, the mechanical properties are deteriorated, and if it exceeds 90% by weight, the moldability is poor and it is not suitable for practical use.

Further, as the curing agent in the composition (1),
For example, various conventionally known hardeners for epoxy resins such as phenolic hardeners such as phenol novolac resin and cresol novolac resin, amine hardeners and acid anhydride hardeners may be mentioned. Two or more of these may be used in combination, and the amount used is not particularly limited, but it is necessary to add stoichiometry to the epoxy group.

Known inorganic fillers can be used as the inorganic filler in the composition (1). Examples thereof include powders of aluminum hydroxide, crystalline silica, fused silica, calcium silicate, calcium carbonate, talc, barium sulfate, and glass fibers. The amount of the inorganic filler compounded is epoxy resin,
15% of the total amount of curing agent and inorganic filler
˜90 wt%, preferably 20-80 wt%. The composition (1) containing less than 15% by weight of the inorganic filler impairs moisture resistance, heat resistance, mechanical properties and moldability,
If it exceeds 90% by weight, the moldability is poor and it is not suitable for practical use.

If necessary, the composition (1) includes, for example, natural waxes, synthetic waxes, metal salts of straight chain fatty acids, acid amides, esters, release agents such as paraffins, chlorinated paraffins, bromotoluene. , Hexabromobenzene,
A flame retardant such as antimony trioxide, a colorant such as carbon black and red iron oxide, a silane coupling agent, a curing accelerator such as benzyldimethylamine and imidazole may be appropriately added and blended. The proportion thereof in the composition (1) is usually 0.01 to 20% by weight. Preferably 0.
It is 2 to 15% by weight.

If necessary, an epoxy resin diluent may be used in the composition (1). Examples of the diluent include organic solvents such as benzene, toluene, xylene, alcohol, ketone, and cellosolve, and n-butyl glycidyl ether called allyl glycidyl ether, reactive glycidyl ether, glycidyl methacrylate, diglycidyl ether, and trimethylolpropane trihydrate. It is possible to use glycidyl ether or the like. If a diluent is added in a large amount, the cross-linking density decreases, so that the effect characteristics of the epoxy resin tend to be deteriorated. Therefore, it is desirable that the viscosity can be reduced to a predetermined value with a small amount of addition and the curing characteristics are not impaired. Usually 1-3 for epoxy resin
0% by weight. It is preferably 5 to 20% by weight.

Next, the AB block copolymer used in the epoxy resin composition of the present invention will be described in detail.
The weight average molecular weight (in terms of styrene, the same applies hereinafter) of the AB block copolymer of the present invention is 50,000 to 20.
10,000, preferably 70,000 to 150,000. When the weight average molecular weight is less than 50,000 or more than 200,000, the effect of low stress is insufficient. In the AB block copolymer of the present invention, the polymer portion A has the general formula (1)
Is a random copolymer formed from a polymer unit represented by the formula (1) and a polymer unit represented by the general formula (2), wherein the polymer unit represented by the general formula (1) is butyl acrylate and the general formula ( The polymer unit represented by 2) is synthesized from (meth) acrylic acid ester as a starting material.
And preferably 1 to 70% by weight of the polymer portion A is formed from the polymer unit represented by the general formula (1). It is more preferably 5 to 50% by weight. When the polymer unit represented by the general formula (1) exceeds 70% by weight, the glass transition temperature of the polymer portion A becomes low and the glass transition temperature of the cured resin becomes low. In addition, the coalescence of the polymers occurs during the production of the AB block copolymer, and it is substantially difficult to produce the AB block copolymer that can be used in the present invention. Further, when the polymer unit represented by the general formula (1) is less than 1% by weight, the effect of lowering the stress is insufficient.

The polymer portion B of the AB block copolymer in the present invention is a random unit formed from a polymer unit represented by the general formula (3) and a polymer unit represented by the general formula (4). It is a copolymer, and the polymer unit represented by the general formula (3) is synthesized by using methyl methacrylate, and the polymer unit represented by the general formula (4) is synthesized by using glycidyl methacrylate as a starting material. Preferably polymer portion B
70 to 99% by weight is formed from the polymer unit represented by the general formula (3), and more preferably 80 to 90% by weight. The polymer unit represented by the general formula (3) is 70
When the amount is less than wt%, the heat resistance of the epoxy resin cured product containing the AB block copolymer is impaired, and conversely, when the amount is more than 99 wt%, the stress reducing effect is insufficient. In addition, if necessary, (meth) may be added to the raw material monomer.
By adding an acrylate ester, the general formula (5)

[Chemical 9] (In the formula, R is hydrogen or a methyl group, and n is an integer of 2 to 12.) The polymer unit B can be contained in the polymer portion B in an amount of 10% by weight or less. Is.

As the (meth) acrylic acid ester used for forming the polymer part A and the polymer part B, methyl (meth) acrylate, ethyl (meth) acrylate,
Propyl (meth) acrylate, hexyl (meth) acrylate, lauryl (meth) acrylate, etc. Excluding butyl acrylate (meth) acrylic acid ester having 1 to 12 carbon atoms
Alkyl ester of.

Further, in the AB type block copolymer of the present invention, the proportion of AB is A / B, preferably 1/99 to 50/50% by weight. More preferably, it is 5/95 to 40/60. When the polymer portion A is less than 1% by weight, the effect of lowering the stress is insufficient, and
If it exceeds 5% by weight, the softening temperature of the AB block copolymer becomes low and coalescence occurs during drying and storage, which makes the polymer difficult to handle and is not suitable for practical use. Random copolymers cannot be used in the present invention. This is because the effect of reducing the stress becomes insufficient. Further core
Shell polymers are also not suitable because they have a smaller stress lowering effect than block bodies. Acrylonitrile-butadiene copolymer is not suitable because the mechanical strength is extremely reduced.

The content of the AB block copolymer in the present invention is preferably 0.1 based on 100 parts by weight of the composition (1) containing an epoxy resin, a curing agent and an inorganic filler as main components. 10 to 10 parts by weight. More preferably 0.5
~ 8 parts by weight. If it is less than 0.1 part by weight, the effect of reducing stress is insufficient, and if it exceeds 10 parts by weight, the mechanical properties tend to be impaired.

The AB block copolymer in the present invention is a production process known as a two-step polymerization method using a polymeric peroxide as a polymerization initiator (for example, JP-B-60-3327 and JP-B-63-30956). It is manufactured by the method described in the publication. At this time, the polymer having a peroxy bond in the molecule generated in the first stage polymerization reaction of either one of the monomer mixtures constituting the polymer portion A or B is taken out from the reaction system as an intermediate and It can be used as a raw material of the block copolymer (mixture), or can be continuously used for the second stage block copolymerization reaction without being taken out from the reaction system. Further, as the polymerization method, any polymerization method such as a bulk polymerization method, a suspension polymerization method, an emulsion polymerization method or a solution polymerization method is adopted, but the suspension polymerization method is most preferable industrially.

As the above-mentioned polymeric peroxide, various polymeric peroxides (for example, those described in Japanese Examined Patent Publication No. 60-3327) are used, and one or more of them are used. Most preferred are those represented by 6) and (7).

[0022]

[Chemical 10] (N represents an integer of 2 to 20.)

[0023]

[Chemical 11] (N represents an integer of 2 to 20.)

The amount of the polymeric peroxide used is 0.1 to 10 parts by weight based on 100 parts by weight of the monomer alone or the monomer mixture constituting the polymer portion A or B used in the one-step polymerization reaction, and the polymerization temperature. Is 40 to 80 ° C. for the first stage polymerization reaction and 60 for the second stage polymerization reaction.
It is preferable that the polymerization temperature is -100 ° C and the polymerization temperature in the second-stage polymerization reaction is higher than the polymerization temperature in the first-stage polymerization reaction.

By the way, a homopolymer is by-produced during the production of the AB block copolymer. According to the above production method,
Since the ratio of the net AB block copolymer in the total polymer, that is, the block ratio is as high as 80% or more, it is particularly purified when used as a stress reducing agent for the epoxy resin in the present invention. It can be used as it is without need.

If necessary, a chain transfer agent such as 1-dodecanethiol may be used in the range of less than 1% by weight.

The molding method using the epoxy resin composition of the present invention may be a usual casting method, compression molding method, or
Any of an injection molding method, a transfer molding method, an injection molding method and the like can be used.

[0028]

According to the present invention, by incorporating a specific AB type block copolymer having a segment compatible with an epoxy resin and a rubber segment, low stress, mechanical properties and heat resistance can be obtained. An excellent epoxy resin composition is obtained.

[0029]

EXAMPLES The present invention will be specifically described below with reference to Examples, Reference Examples and Comparative Examples. In addition, in each example, a part and% show a weight part and weight% unless there is particular notice. The abbreviations of the compounds in Table 1 and Table 2 indicate the following compounds. BA: Butyl acrylate MMA: Methyl methacrylate GMA: Glycidyl methacrylate PMA: Propyl methacrylate HMA: Hexyl methacrylate The test method is as follows.

[Measurement Method of Epoxy Equivalent] Epoxy equivalent is measured by titration using a perchloric acid / acetic acid solution according to JIS K 7236.

[Strain measurement] Strain gauge (Kyowa Denki Co., Ltd.)
Product number: KFG-5-120-C1-11L1M
2R) installed on a Teflon plate with an inner diameter of 80 mm and a height of 2
Fix in a 5 mm stainless ring. About 100 g of the epoxy resin composition was cast into the mold and cured at room temperature to measure the strain value after curing. Note that here, the larger the numerical value is, the larger the distortion is.

[Flexural Strength] [Flexural Modulus] The epoxy resin composition was cured by a casting method at 80 ° C. for 4 hours and then at 180 ° C. for 4 hours to obtain 80 mm × 10 mm.
A test piece of x4 mm was prepared and measured according to JIS K 6911.

[Heat Deformation Temperature] A test piece of 110 mm × 10 mm × 4 mm was prepared in the same manner as the measurement of the bending strength, and J
It was measured according to IS K 6911.

Synthesis Example 1 [Production of AB Block Copolymer] 100 ml of water was added to a stainless reactor equipped with a thermometer, a mixer and a condenser.
Part, partially saponified polyvinyl alcohol (Nippon Kagaku Kogyo KK, trade name: Gohsenol GH-20) 1% aqueous solution 10 parts, oxyethylene-oxypropylene block polymer (Nippon Oil & Fats Co., Ltd. trade name: Pronone 20)
10 parts of a 1% aqueous solution of 8) was charged as a suspension. Next, 0.5 parts of the polymeric peroxide represented by the general formula (5), 13.5 parts of butyl acrylate and 13.5 parts of methyl methacrylate were charged into the above suspension and dispersed for about 30 minutes. Then, the oil droplets were dispersed with a homomixer (TK homomixer manufactured by Tokushu Kika Kogyo Co., Ltd.) at 10,000 rpm for about 10 minutes. Next, under nitrogen substitution, 60 ℃
Polymerization was carried out for 4 hours to complete the first stage polymerization. Next, after cooling to room temperature, 63 parts of methyl methacrylate and 10 parts of glycidyl methacrylate were added to the reactor and impregnation operation was carried out at room temperature for about 1 hour, and 10000 rp with a homomixer as in the first stage.
The mixture was stirred for 1 hour at m.
Polymerization was continued at 2 ° C for 2 hours and then at 90 ° C for 30 minutes. After cooling to room temperature to complete the polymerization operation, the obtained polymer was filtered off, washed sufficiently with water, and air-dried to form a white pearl type AB block copolymer (weight average molecular weight: 80,000-10). Ten thousand). The epoxy equivalent of the AB block copolymer obtained by titration using a perchloric acid / acetic acid solution was measured according to JIS K 7236. The results are shown in Table 1.
It was shown to.

[0035]

[Table 1]

Synthesis Example 2 1 as a chain transfer agent during the first-stage polymerization and the second-stage polymerization
-Synthesis example 1 except that 0.5 part of dodecanethiol was added
Polymerization was performed according to the procedure described above to obtain a white pearl type AB block copolymer. The results are shown in Table 1.

Synthesis Examples 3 to 14 Polymerization was carried out according to Synthesis Example 1 except that the charged amounts of butyl acrylate, methyl methacrylate and glycidyl methacrylate were changed as shown in Tables 1 and 2, and white pearly A was polymerized. −
A B-type block copolymer was obtained. The results are shown in Tables 1 and 2.

Synthesis Example 15 Polymerization was carried out in the same manner as in Synthesis Example 1 except that propyl methacrylate was used in place of methyl methacrylate in the first-stage polymerization to obtain a white pearl type AB block copolymer. . The results are shown in Table 2.

Synthesis Example 16 White pearl type AB block copolymer was polymerized according to Synthesis Example 1 except that hexyl methacrylate was used in addition to methyl methacrylate and glycidyl methacrylate during the second stage polymerization. Got The results are shown in Table 2.

[0040]

[Table 2]

Synthesis Example 17 Polymerization was carried out according to Synthesis Example 1 except that the polymeric peroxide represented by the general formula (7) was used to obtain a white pearl type AB block copolymer. The results are shown in Table 2.

[Production of Comparative Stress Reducing Agent] Synthesis Example 18 [Production of Random Copolymer] In a stainless reactor equipped with a thermometer, a mixer and a condenser, water 500, partially saponified polyvinyl alcohol (Nippon Kagaku Kogyo) Suspended 10 parts of a 1% aqueous solution of trade name: Gohsenol GH-20) and 1% aqueous solution of oxyethylene-oxypropylene block polymer (NOF Corporation, trade name: Pronone 208). It was prepared as a liquid. 0.3 parts of benzoyl peroxide as a polymerization initiator was dispersed in the above suspension at room temperature for about 1 hour, and then 13.5 parts of butyl acrylate,
After charging 76.5 parts of methyl methacrylate and 10 parts of glycidyl methacrylate, the mixture was heated at 80 ° C. for 1.5 hours and then 9 parts.
Polymerization was continued at 0 ° C for 30 minutes. After cooling to room temperature to complete the polymerization operation, the obtained polymer was filtered off, washed sufficiently with water, and air-dried to obtain a white pearl-like random copolymer. It was used as a comparative stress reducing agent. The composition ratio of the obtained random copolymer is the same as that of the AB block copolymer of Synthesis Example 1.

Synthesis Example 19 [Production of core-shell polymer] 400 parts of pure water and dodecylbenzenesulfonic acid (trade name, manufactured by NOF CORPORATION) in a glass reactor equipped with a thermometer, a mixer and a condenser.
5 parts of a 5% aqueous solution of Nuperex paste H) was charged as an emulsion. Butyl acrylate 13.5 parts and 1-
Charge 0.5 parts of dodecyl mercaptan and replace under nitrogen with 7
The temperature was raised to 5 ° C., potassium persulfate as a polymerization initiator was added, and polymerization was carried out for 6 hours to complete the first stage polymerization. Next, the emulsion, 400 parts of pure water, and 5 parts of a 5% aqueous solution of dodecylbenzenesulfonic acid were added and emulsified. Methyl methacrylate 76.5 parts, glycidyl methacrylate 10 parts and 1-
0.5 part of dodecyl mercaptan was charged, 0.6 part of potassium persulfate was added after the temperature was raised to 75 ° C., and polymerization was carried out for 6 hours to complete the second stage polymerization under nitrogen substitution. The obtained polymer was salted out with a 1% aqueous solution of aluminum sulfate, filtered and air-dried to obtain a core-shell polymer having polybutyl acrylate as a core and polymethyl methacrylate and polyglycidyl methacrylate as a shell. . The composition ratio of the obtained random copolymer is the same as that of the AB block copolymer of Synthesis Example 1.

Synthesis Example 20 Acrylonitrile-butadiene copolymer (B / F
Product made by Goodrich "BF Goodrich", product name:
Hiker "Hycar" CTBN 1300X13)
Was used as a stress reducing agent for comparison.

[Preparation of Epoxy Resin Composition and Preparation of Cured Product] Examples 1 to 13, 17 to 23 and Comparative Examples 1 to 4 Bisphenol A glycidyl ether type epoxy resin (epoxy equivalent; 190) (oiled shell epoxy ( stock)
Made, trade name: Epicoat 828) 58.5%, triethylenetetramine (Sumitomo Chemical Co., Ltd., trade name: triethylenetetramine) 10.5%, aluminum hydroxide (Showa Denko KK, trade name: Heidilite H-42) 29.2%
And 100 parts of a composition consisting of 1.8% of zinc stearate (trade name; zinc stearate, manufactured by NOF CORPORATION), and each of the AB block copolymers shown in the synthesis examples and a comparative example. After adding the stress-reducing agent in the proportions shown in Tables 3 to 6, mixing and defoaming were performed to prepare epoxy resin compositions. Tables 3 to 6 show the results of strain measurement using these compositions by the method described below and evaluation of mechanical properties using the obtained cured products.

[0046]

[Table 3]

[0047]

[Table 4]

[0048]

[Table 5]

[0049]

[Table 6]

Example 14 An epoxy resin composition was prepared according to Example 1 except that fused silica was used as the filler, and the results of evaluation by the same method are shown in Table 4.

Example 15 Phenol novolac type epoxy resin (epoxy equivalent 2
20) 17.9%, phenol novolac resin (hydroxyl equivalent 110) 8.9%, triphenylphosphine 1.8
%, Antimony trioxide 3.2%, carnauba wax 0.
To 100 parts of a composition composed of 4% and fused silica of 67.8%, 5 parts of an AB block copolymer was added, and 70-
The mixture was roll-kneaded at 100 ° C., cooled and pulverized to obtain a molding material. The obtained molding material was tabletted, molded by low-pressure transfer molding, and evaluated by the same method. The results are shown in Table 4.

Example 16 Example 15 except that a cresol novolac type epoxy resin (epoxy equivalent 210) was used as the epoxy resin.
The composition was prepared and molded according to. Evaluation was carried out by the same method, and the results are shown in Table 4.

In comparison with the above examples and comparative examples, by blending the AB block copolymer of the present invention with an epoxy resin, a cured product having low stress, excellent mechanical properties and heat resistance can be obtained. That is clear.

The technical idea other than the claims grasped from the embodiment will be described below. (1) The composition represented by the general formula (1) based on 100 parts by weight of the composition (1) containing an epoxy resin, a curing agent and an inorganic filler as main components.
A polymer unit A formed from a polymer unit represented by the formula (1) and a polymer unit represented by the formula (2), a polymer unit represented by the formula (3) and a polymer unit represented by the formula (4). The epoxy resin composition according to claim 1, wherein the epoxy resin composition comprises 0.1 to 10 parts by weight of an AB block copolymer composed of a polymer portion B formed of a unit. (2) The epoxy resin composition according to claim 1, wherein the polymer portion A of the AB block copolymer has 1 to 70% by weight of the polymer unit represented by the general formula (1). (3) The proportion of the polymer portion B of the AB block copolymer is 70 to 9 for the polymer unit represented by the general formula (3).
9% by weight, the polymer unit represented by the general formula (4) is 1 to 3
The epoxy resin composition according to claim 1, wherein 0% by weight and the content of the polymer unit represented by the general formula (9) are 10% by weight or less. (4) The composition ratio of the polymer portion A and the polymer portion B of the AB type block copolymer is such that A / B is 1/99 to 5 by weight.
The epoxy resin composition according to claim 1, which is 0/50.

Claims (1)

[Claims] 1. A composition represented by the general formula (1): embedded image with respect to the composition (1) containing an epoxy resin, a curing agent and an inorganic filler as main components. And a polymer unit represented by the general formula (2): (In the formula, R is hydrogen or a methyl group, and n is an integer of 1 to 12. However, when R is hydrogen, n = 4 is excluded.) And the general formula (3): And a polymer unit represented by the general formula (4): An epoxy resin composition comprising an AB type block copolymer comprising a polymer unit B formed from the polymer unit represented by