JP3572653B2 - Adhesive composition for flexible printed wiring boards - Google Patents

Description

（比較例２）
実施例１の配合を下記の様に変更した以外は実施例１と同様に行った。

（比較例３）
実施例２の配合を下記の様に変更した以外は実施例２と同様に行った。

【００２４】
【表１】

【００２５】
【発明の効果】
以上説明したように、本発明のフレキシブル印刷配線板用接着剤組成物は、重量平均分子量（Ｍｗ）が６０万≦Ｍｗ≦１２０万で、且つ分子量分布（重量平均分子量／数平均分子量＝Ｍｗ／Ｍｎ）が３．５以下と分子量が調整された官能基を有するアクリルエラストマー（Ａ）と、カチオン重合型触媒（ａ）と平均粒径が５μｍ以下の特定のマイクロカプセル化触媒もしくは平均粒径が３０μｍ以下の特定の粉末状触媒（ｂ）とを組み合わせ、かつ該硬化促進剤（Ｄ）中のカチオン重合型触媒（ａ）と該マイクロカプセル化触媒（ｂ）もしくは２−アルキルイミダゾール誘導体もしくは２−フェニルイミダゾール誘導体からなる該粉末状触媒（ｂ）とを特定範囲量で用いたことにより、
半硬化状態での貯蔵安定性と作業性に優れた特徴を持ち、比較的低温短時間で硬化可能で、接着力、半田耐熱性、耐流れ出し性、ポットライフ、タック性等が優れた、フレキシブル印刷配線板用接着剤組成物として必要とされる特性を全て満足するものである。[0001]
[Industrial applications]
The present invention relates to an improvement in an adhesive composition suitable for bonding a plastic film used for a flexible printed wiring board to a reinforcing plate.
In particular, the present invention is required for adhesion between a plastic film used for a flexible printed wiring board and a reinforcing plate by a low-temperature, short-time press while having good workability in a semi-cured state and a long pot life. The present invention relates to an adhesive composition satisfying all the following characteristics.
[0002]
[Prior art]
Conventional adhesives for flexible printed wiring boards are as follows.
That is, when a powdery curing agent is used, pressurized water cooling to room temperature is required to prevent distortion, and it is necessary to raise the temperature again to perform the next press, and the press cycle time is long (see Japanese Unexamined Patent Publication No. -2092973).
When a curing agent and a cationic polymerization type catalyst are used, pressurized water cooling is not required, but the pressing conditions are high, the life is short, and the workability is poor (Japanese Patent Laid-Open No. 3-221578).
[0003]
Further, in order to obtain a sufficient adhesive performance, an aromatic polyamine or a cationic polymerization type curing agent is used as a curing agent, so that there is a disadvantage that a high temperature, a high pressure and a long press are required.
On the other hand, by using a combination of a cationic polymerization catalyst and a microencapsulated catalyst as a curing accelerator, the adhesive strength, solder heat resistance, and resistance to run-out at low temperature and short time are excellent, and the pot life is long. the flexible printed wiring board adhesives have been proposed (Japanese Patent Application No. 4-2 No. 9 3920; JP-a 6-116366 JP).
[0004]
[Problems to be solved by the invention]
However, in the case of this adhesive, it can be cured at a low temperature for a short time and has a long pot life. However, if the surface tack in the semi-cured state is strong, that is, if the surface has a strong adhesive force, the workability of the bonding to the adherend is reduced. In such a case, there is a problem that positioning is difficult, and once bonded together, they cannot be peeled off, resulting in poor efficiency.
That is, in order to keep the pot life long, it is necessary to suppress the curing reaction in a semi-cured state, and therefore, there is a problem that the surface tack is strong and the workability is deteriorated.
In the case of curing at a low temperature for a short time, it is difficult to make the reaction uniform because the reaction time is short, and it is difficult to obtain reproducibility such as solder heat resistance because unreacted substances are likely to remain.
[0005]
[Means for Solving the Problems]
The present inventors have made various studies on the above-mentioned problems, and as a result, together with the functional group-containing acrylic elastomer (A) having an adjusted molecular weight, the epoxy resin (B), and the curing agent (C), a cationic polymerization type catalyst (a) ) And a specific powdery catalyst (b) comprising a microencapsulated catalyst (b) or a 2-alkylimidazole derivative or a 2-phenylimidazole derivative, and a specific adhesive composition containing a composite curing accelerator (D) It has been found that the product is suitable as an adhesive for flexible printed wiring boards, and the present invention has been completed.
That is, the present invention provides:
(1) (A) Acrylic having a functional group having a weight average molecular weight (Mw) of 600,000 ≦ Mw ≦ 1.2 million and a molecular weight distribution (weight average molecular weight / number average molecular weight = Mw / Mn) of 3.5 or less Based elastomer,
(B) an epoxy resin having two or more epoxy groups in one molecule,
(C) a curing agent,
(D) A curing accelerator comprising a combination of (a) a cationic polymerization type catalyst and (b) a microencapsulated catalyst having an average particle size of 5 μm or less or a powdery catalyst having an average particle size of 30 μm or less is an essential component. And the weight of the cationic polymerization type catalyst (a) in the curing accelerator (D) is 0.5 to 5.0% by weight based on the weight of the solid content of the epoxy resin (B). (B) or the weight of the powder catalyst (b) is 1.0 to 10.0% by weight based on the weight of the solid content of the epoxy resin (B), and the powder catalyst is a 2-alkylimidazole derivative Alternatively , the present invention provides an adhesive composition for a flexible printed wiring board, which is a powdery catalyst comprising a 2-phenylimidazole derivative .
[0006]
Hereinafter, the present invention will be described in detail.
In the present invention, a cationic polymerization catalyst (a) is added to an acrylic elastomer (A) having a functional group having a weight average molecular weight (Mw) of 600,000 ≦ Mw ≦ 1.2 million and a molecular weight distribution of 3.5 or less. ) And a specific microencapsulated catalyst (b) or a powdery catalyst (b) comprising a 2-alkylimidazole derivative or a 2-phenylimidazole derivative were used as the curing accelerator (D), so that a long pot was used. While maintaining the life, the workability in the semi-cured state is good, and all other required properties are exerted by pressing at a low temperature for a short time.
In this case, by using a specific acrylic elastomer having a low molecular weight component considered to be a cause of surface tack and having a uniform molecular weight as much as possible, the curing is accelerated and the pot life is shortened without shortening the pot life. The surface tackiness is suppressed, the workability and the flowability are good, and the reaction occurs uniformly, so that it is effective in reproducibility and the like.
[0007]
Hereinafter, each of (A), (B), (C), and (D) constituting the adhesive composition of the present invention will be described.
The specific acrylic elastomer (A) used in the present invention has a weight average molecular weight of 600,000 to 1,200,000, preferably 600,000 to 1,000,000 and a molecular weight distribution of 3.5 or less, preferably 3.3 or less. And the component composition is an acrylic polymer containing one or more acrylates or α-substituted acrylates as a main component and containing at least one functional group as a crosslinking point, or An acrylic polymer in which at least one of the functional group-containing monomers is (grafted) copolymerized with the above main component monomer is included.
[0008]
More specifically, the acrylic elastomer (A) comprises (a) one or more of an acrylate ester or an α-substituted acrylic elastomer as a large proportion of components, and (b) an epoxy group, (c) a carboxyl group, (D) An acrylic elastomer obtained by copolymerizing a monomer having one or more functional groups selected from the group of hydroxyl groups can be used.
Examples of the acrylate or α-substituted acrylic elastomer (a) include methyl acrylate, ethyl acrylate, propyl acrylate, butyl acrylate, octyl acrylate and the like.
Examples of the epoxy group (b) include glycidyl ethers such as vinyl glycidyl ether and acrylic glycidyl ether, and glycidyl (meth) acrylates.
Examples of the carboxyl group (c) include (meth) acrylic acid, itaconic acid, maleic acid, and maleic anhydride.
Examples of the hydroxyl group (d) include dimethacrylates of polyhydric alcohols such as 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, ethylene glycol dimethacrylate, propylene glycol dimethacrylate, and polyethylene glycol dimethacrylate; methoxymethyl And alkoxyalkyl acrylates such as acrylate.
Further, if necessary, (e) other vinyl monomers such as vinyl chloride, vinylidene chloride, styrene, methacrylonitrile, and vinyl acetate may be copolymerized.
[0009]
If this acrylic elastomer (A) has a weight average molecular weight of less than 600,000, it will contain a large amount of low molecular weight components in the acrylic elastomer (A) . In other words, this adhesive composition contains a capsule-shaped curing accelerator to prolong the pot life, so that the promotion of reaction in a semi-cured state is suppressed. And the workability is poor, which has an adverse effect on the resistance to runoff.
On the other hand, when the weight average molecular weight of the acrylic elastomer (A) exceeds 1.2 million, the viscosity of the elastomer (A) increases, and it becomes difficult to mix with other components, and it is difficult to obtain reproducibility.
Furthermore, even when the weight average molecular weight (Mw) of the acrylic elastomer (A) is within the specified range of 600,000 ≦ Mw ≦ 1.2 million, a uniform reaction occurs when the molecular weight distribution exceeds 3.5 and becomes wide. And reproducibility deteriorates.
[0010]
Next, the compounding ratio of the acrylic elastomer (A) is in the range of 1 / 1-10 / 1 at a solid content weight ratio to the epoxy resin (B), the preferred range of 2 / 1-6 / 1 Is good.
If the blending ratio of the acrylic elastomer (A) is less than 1/1, the solder heat resistance is reduced, and if it is more than 10/1, the adhesive strength is reduced.
[0011]
The epoxy resin (B) used in the present invention is not particularly limited, but generally may be any resin having two or more epoxy groups in one molecule.
For example, bisphenol A type epoxy resin, phenol novolak type epoxy resin, brominated epoxy resin and the like can be mentioned.
[0012]
The curing agent (C) is not particularly limited, and examples thereof include generally used aliphatic polyamines, acid anhydrides, and aromatic polyamines.
The amount of the curing agent (C) to be added is (epoxy) equivalent to 1/2 (epoxy) equivalent based on the amount of the functional group (including epoxy group) in the acrylic elastomer (A) and the epoxy resin (B). Is preferred.
If the compounding amount of the curing agent (C) is less than 1/2 (epoxy) equivalent, a sufficient degree of curing cannot be obtained, resulting in deterioration of solder heat resistance. Further, even if the amount is more than the (epoxy) equivalent, decomposition gas is generated in the soldering heat test, which is not preferable.
[0013]
The cationic polymerization catalyst constituting curing accelerator (D) (a), for example, _{BF 3 -MEA, SbF 5 -MEA,} FeCl 3, PF 5 -MEA, AlCl 3 or the like; quaternary ammonium salts, 4th Grade sulfonium salts and alkali metal salts of organic weak acids.
The addition amount of the cationic polymerization catalyst (a) is 0.5 to 5.0% by weight relative to the solid weight of the epoxy resin (B), the preferably 1.0 to 3.0 wt%.
When the amount of the cationic polymerization type catalyst (a) is less than 0.5% by weight, the pot life is prolonged, but the initial performance is not sufficient. Conversely, if the content exceeds 5.0% by weight, the pot life is reduced, and it is practically unusable.
[0014]
The amount of the microencapsulated catalyst or the powdery catalyst (b) constituting the curing accelerator (D) together with the cationic polymerization type catalyst (a) is 1.0 to 1.0% by weight of the solid content of the epoxy resin (B). To 10.0% by weight , and preferably 3.0 to 6.0% by weight.
If the addition amount of the microencapsulated catalyst or the powdered catalyst (b) is less than 1.0% by weight, the initial performance as a curing accelerator cannot be sufficiently exhibited. Further, if it is added in excess of 10.0% by weight, the pot life is undesirably reduced.
[0015]
Examples of the powdery catalyst (b) comprising the 2-alkylimidazole derivative or the 2-phenylimidazole derivative of the present invention include Cureazole C17Z (trade name, manufactured by Shikoku Chemicals Co., Ltd.) and Curezole 2PHZ (trade name, manufactured by Shikoku Chemicals Co., Ltd.) name), Curesol 2MZA (Shikoku Kasei Co., Ltd., can be exemplified powdery catalyst represented by trade name).
The average particle size of the powdered catalyst is 30 μm or less, and preferably 3 to 15 μm.
If the average particle size of the powdery catalyst exceeds 30 μm, the area in contact with the resin composition constituting the adhesive composition decreases, so that a high temperature and a long time are required for bonding, and the average particle size is too large. If it is too small, the contact area with the cationic polymerization catalyst becomes too large, and the pot life becomes short.
[0016]
The microencapsulated catalyst (b) of the present invention is a thin layer coated with a coating agent such as polyurethane to such an extent that the microencapsulation is easily broken by application of pressure or temperature, and is made of NOVACURE HX-3612. , -3722, -3741 and -3748 (trade names, manufactured by Asahi Kasei Corporation).
The average particle size of the microencapsulated catalyst (b) is 5 μm or less , and preferably is finely divided to 1 to 3 μm.
Further, when the average particle size of the microencapsulated catalyst (b) exceeds 5 μm, the area in contact with the resin composition constituting the adhesive composition decreases, so that a high temperature and a long time are required for adhesion, and If the average particle size is too small, the contact area with the cationic polymerization catalyst becomes too large, and the pot life is shortened.
[0017]
The adhesive composition of the present invention is desirably blended with a fine inorganic filler or the like, if necessary. These are not particularly limited, but ultrafine anhydrous silica, aluminum hydroxide, talc (hydrated magnesium silicate) may be used. ), Clay (pyrophyllite) and the like, and these can be used alone or in combination of two or more.
The fine particles of the inorganic filler and the like in this case have a particle size of 10 μm or less, preferably 1 to 5 μm.
When the particle size exceeds 10 μm , the adhesive strength is reduced, and when the particle size is 1 μm or less, mixing with other compositions becomes difficult.
As the solvent used in the adhesive composition of the present invention, methyl ethyl ketone, acetone, toluene, dioxane, methyl cellosolve acetate, ethylene glycol monomethyl ether, and the like, and a mixture thereof can be used.
[0018]
To apply the adhesive composition of the present invention to a film or a reinforcing plate, components of the adhesive composition are first mixed by a known mixing means, then dissolved in a solvent, and applied in a solution state. In this case, after being applied to one of the adherends, lamination and curing are performed by an arbitrary heating and curing means.
For example, the coated material is dried in a hot-air oven to dry the solvent, or is pre-cured to a semi-cured state, then combined with another object to be bonded, and heated to 130 to 180 ° C. in a method of thermocompression bonding at a pressure of ^5kg / cm ^{2 ~40kg} / cm 2 is employed.
Examples of the reinforcing plate to which the adhesive composition of the present invention is applied include an aluminum plate, a silicon steel plate, a paper phenol laminate, a glass epoxy laminate, polypropylene, and polyethylene.
Further, the film to which the adhesive composition of the present invention is applied is not particularly limited as long as it is a polymer film, but particularly refers to a film used for FPC, a polyimide film, a polyester film, a polyethersulfone film, an ultrathin laminate And the like.
[0019]
【Example】
The present invention will now be described specifically by way of examples, which do not limit the scope of the present invention.
The present invention is specifically described by the following evaluations.
(1) Adhesive strength: conforms to JIS C6481 (2) Solder heat resistance: conforms to JIS C6483 (3) Flow resistance: A 08 mm hole is formed in the FPC, and the amount of adhesive bleeding after pressing is measured. .
(4) Pot life: days until the adhesive strength becomes 0.8 kg / cm (5) Tackiness: An adhesive solution is applied on a release paper so as to have a solid content of 40 μm thick, and 100 ° C. × 5 minutes The semi-cured state is obtained by drying, and a polyimide film is superimposed on the adhesive in this state, and a weight of 1 g / cm ² is applied for 12 hours, and whether or not the polyimide film is separated from the adhesive is evaluated.
[0020]
(Example 1)
SG-70 (trade name, manufactured by Teikoku Chemical Industry Co., Ltd.) as an acrylic elastomer was dissolved in toluene and then reprecipitated in methanol to give a molecular weight distribution of 3.3 and a weight average molecular weight of 930,000. / Toluene = 93.5 parts by weight dissolved in 1/1, 6.25 parts of Epikote 828 (trade name, manufactured by Yuka Shell Epoxy Co., Ltd.) as an epoxy resin, 4,4-diaminodiphenylmethane (4,4-diaminodiphenylmethane as an aromatic polyamine) 0.7 parts of Sumitomo Chemical Co., Ltd., trade name), 0.125 parts of cation polymerization type catalyst BF ₃ -MEA (trade name, made by Hashimoto Kasei Co., Ltd.) as a curing accelerator, and 5 μm particle size microcapsules 0.60 parts of the catalyzed catalyst NOVACURE HX-3741 (trade name, modified imidazole coated with polyurethane, manufactured by Asahi Kasei Corporation) as an inorganic filler Then, 7 parts of talc (manufactured by Mistron Co., Ltd.) having a particle size of 5 μm were mixed and stirred to obtain a viscous adhesive solution.
Then, it was applied on a release paper so as to have a thickness of 40 μm in solid content, and dried at 100 ° C. for 5 minutes to obtain a semi-cured film. Using this, an aluminum reinforcing plate and a flexible printed wiring board were bonded together and pressed under the conditions of 160 ° C. × 10 kg / cm / 5 minutes.
[0021]
(Example 2)
After dissolving SG-80 (trade name, manufactured by Teikoku Chemical Industry Co., Ltd.) in toluene as an acrylic elastomer, reprecipitating in methanol to give a molecular weight distribution of 2.9, a weight average molecular weight of 1.1 million, and epicoat as an epoxy resin 154, aromatic polyamines 4,4-diaminodiphenyl sulfone (Sumitomo chemical Co., Ltd., trade name), a cationic polymerization catalyst _Sb 5-MEA and a particle size of 2μm microencapsulated catalysts NOVACURE HX as a curing accelerator Except using -3742, it carried out similarly to Example 1.
[0022]
(Example 3)
As an acrylic elastomer, WS-023 (trade name, manufactured by Teikoku Chemical Industry Co., Ltd.) is dissolved in toluene, and then reprecipitated in methanol to give a molecular weight distribution of 3.1, a weight average molecular weight of 850,000, and an epoxy resin. Epikote 1004, 4,4-diaminodiphenyl ether as aromatic polyamines, cationic polymerization catalyst _PF 5 0.125 parts of particle size 25μm to -MEA powdery catalyst Curezol C17-Z (Shikoku Kasei Co., Ltd. as a curing accelerator, Example 1 was repeated except that 0.3 parts of (trade name) were used.
[0023]
(Comparative Example 1)
Example 1 was repeated except that the composition of Example 1 was changed as follows.

(Comparative Example 2)
Example 1 was repeated except that the composition of Example 1 was changed as follows.

(Comparative Example 3)
Example 2 was carried out in the same manner as in Example 2 except that the composition was changed as follows.

[0024]
[Table 1]

[0025]
【The invention's effect】
As described above, the adhesive composition for a flexible printed wiring board of the present invention has a weight average molecular weight (Mw) of 600,000 ≦ Mw ≦ 1.2 million and a molecular weight distribution (weight average molecular weight / number average molecular weight = Mw / An acrylic elastomer (A) having a functional group whose molecular weight is adjusted to 3.5 or less, a cationic polymerization type catalyst (a), and a specific microencapsulated catalyst having an average particle size of 5 μm or less or an average particle size of 5 μm or less. Combination with a specific powdery catalyst (b) having a particle size of 30 μm or less, and the cationic polymerization type catalyst (a) in the curing accelerator (D) and the microencapsulation catalyst (b) or a 2-alkylimidazole derivative or 2-alkylimidazole derivative By using the powdered catalyst (b) comprising a phenylimidazole derivative in a specific range,
Flexible with excellent storage stability and workability in a semi-cured state, can be cured in a relatively low temperature and short time, and has excellent adhesive strength, solder heat resistance, run-out resistance, pot life, tackiness, etc. It satisfies all the properties required for the adhesive composition for printed wiring boards.

Claims (1)

(A) an acrylic elastomer having a functional group having a weight average molecular weight (Mw) of 600,000 ≦ Mw ≦ 1.2 million and a molecular weight distribution (weight average molecular weight / number average molecular weight = Mw / Mn) of 3.5 or less;
(B) an epoxy resin having two or more epoxy groups in one molecule,
(C) a curing agent,
(D) A curing accelerator comprising a combination of (a) a cationic polymerization type catalyst and (b) a microencapsulated catalyst having an average particle size of 5 μm or less or a powdery catalyst having an average particle size of 30 μm or less is an essential component. And the weight of the cationic polymerization type catalyst (a) in the curing accelerator (D) is 0.5 to 5.0% by weight based on the weight of the solid content of the epoxy resin (B), (B) or the weight of the powder catalyst (b) is 1.0 to 10.0% by weight based on the weight of the solid content of the epoxy resin (B), and the powder catalyst is a 2-alkylimidazole derivative Alternatively , the adhesive composition for a flexible printed wiring board is a powdery catalyst comprising a 2-phenylimidazole derivative .