JP2001064613A - Thermosetting adhesive - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a thermosetting adhesive improved in storage stability and easily convertible to film by including an epoxy resin, a latent curing agent and a specific alkylene glycol monoether acetate. SOLUTION: This thermosetting adhesive is obtained by including (A) 100 pts.wt. of an epoxy resin [pref. a bisphenol A-type epoxy resin 1,000-5,000 in epoxy equivalent (g/ep)], (B) pref. 10-200 pts.wt. of a latent curing agent (pref. an imidazole-based latent curing agent with a curing temperature of about 170 deg.C) and (C) pref. 10-280 pts.wt. of a compound of the formula CH3COOR1OR2 (R1 is a lower alkylene; R2 is a lower alkyl) (e.g. 2-ethoxyethyl acetate).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a curable adhesive useful as an adhesive component of an anisotropic conductive adhesive.

[0002]

2. Description of the Related Art A liquid or paste-like anisotropic conductive adhesive in which conductive fine particles are dispersed in an insulating thermosetting adhesive or an anisotropic conductive adhesive film formed from the same is used to electrically connect electronic components to each other. It is widely used when making a connection.

[0003] As such an insulating thermosetting adhesive, those containing an epoxy resin, a latent curing agent and a solvent are widely used. Here, for the solvent,
(i) When the thermosetting adhesive is stored, the solid component of the thermosetting adhesive is uniformly dissolved, but the latent curing agent is not substantially dissolved. (ii) The thermosetting adhesive is applied. When applied to a body and dried to form a film, the latent curing agent is required to easily evaporate in an oven set at a temperature (usually 100 ° C. or less) at which the curing reaction does not substantially start. I have.

Conventionally, solvents selected in consideration of such requirements include toluene (boiling point: 111 ° C.) and ethyl acetate (boiling point: 77 ° C.).

[0005]

However, in the case of a thermosetting adhesive using toluene or ethyl acetate as a solvent, the solvent, such as toluene or ethyl acetate, gradually dissolves the latent curing agent and changes its quality. There is a problem that the storage stability of the curable adhesive itself decreases. Moreover, when such a thermosetting adhesive was formed into a film, the storage stability (40 ° C., 7 days) of the obtained thermosetting adhesive film itself was insufficient. For this reason, immediately after preparing a thermosetting adhesive using toluene or ethyl acetate (within several hours)
In addition, since it is necessary to perform a film forming operation and the like, the operation is complicated and the waste of the adhesive is increased.

The present invention has been made to solve the above-mentioned problems of the prior art, and improves the storage stability of an insulating thermosetting adhesive containing an epoxy resin, a latent curing agent and a solvent. Another object of the present invention is to improve the storage stability of the obtained adhesive film by easily forming it into a film.

[0007]

SUMMARY OF THE INVENTION The present inventors have used a specific alkylene glycol monoether acetate having an SP value relatively close to that of toluene or ethyl acetate, but exhibiting a relatively low vapor pressure and a relatively high boiling point. By doing so, it is possible to unexpectedly improve the storage stability of the thermosetting adhesive itself, and furthermore, it is possible to easily form a film, and it is also possible to improve the storage stability of the obtained adhesive film. This led to the completion of the present invention.

That is, the present invention relates to a thermosetting adhesive containing an epoxy resin, a latent curing agent and a solvent, wherein the solvent is of the formula (1)

[0009]

Embedded image containing an alkylene glycol monoether acetate represented by CH ₃ COOR ¹ OR ² (1) wherein R ¹ is a lower alkylene group and R ² is a lower alkyl group. A thermosetting adhesive is provided.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.

[0011] The thermosetting adhesive of the present invention contains an epoxy resin, a latent curing agent and a solvent. Here, as the solvent, the formula (1)

[0012]

## STR3 ## _{^{CH 3 COOR 1 OR 2 (1}} ) ( wherein, R ¹ represents a lower alkylene group, preferably an ethylene group, a propylene group, R ² is a lower alkyl group, preferably a methyl group, an ethyl group, a propyl Alkylene glycol monoether represented by the following formula: isopropyl group, butyl group, isobutyl group). This alkylene glycol monoether acetate has an SP value of 7 to
10, boiling point = 140-200 ° C, vapor pressure (25 ° C) = 1
A solvent that has physical properties of 0 mmHg or less and that uniformly dissolves the epoxy resin but does not substantially dissolve the latent curing agent. Therefore, by using this solvent, the storage stability of the prepared thermosetting adhesive itself is improved, and as a result, the storage stability when formed into a film is also improved. The alkylene glycol monoether acetate can be used under temperature conditions for forming a thermosetting adhesive into a film (that is, at a temperature at which the latent curing agent does not substantially start the curing reaction (usually 100 ° C).
It can be evaporated at a rate that does not pose a practical problem in an oven set at (C) or lower)).

If the amount of the alkylene glycol monoether acetate of the formula (1) is too small, the viscosity becomes too high and the handleability decreases. If the amount is too large, pinholes tend to be formed during film formation. The amount is preferably from 10 to 280 parts by weight, more preferably from 40 to 150 parts by weight, based on 100 parts by weight of the resin.

In the present invention, in addition to the alkylene glycol monoether acetate of the formula (1), if necessary, other general solvents (for example, toluene, ethyl acetate, etc.) do not impair the effects of the present invention. You may use together in the range.

The epoxy resin used in the present invention comprises:
What has been used as a film-forming component of a known thermosetting adhesive (for example, an insulating thermosetting adhesive for an anisotropic conductive adhesive) can be preferably used. In particular,
It is preferable to use a high-molecular-weight epoxy resin that is solid at room temperature and an epoxy resin that is liquid at room temperature in consideration of film-forming properties and film strength.

As a solid epoxy resin at room temperature, a BPA (bisphenol A) type epoxy resin having an epoxy equivalent (g / ep) of 1,000 to 5,000 can be preferably used. Specifically, EP1010 (3,000 to 5,000) is used.
g / ep), EP1009 (2400-3300 g / ep), E
P1007 (1750 to 2200 g / ep) (all manufactured by Yuka Shell Epoxy Co., Ltd.) and the like can be used. In addition, epoxy equivalent which is liquid at room temperature,
A BPA type epoxy resin having a (g / ep) of 180 to 200 can be preferably used, and specifically, EP828 (1
90 g / ep) or the like can be used.

The mixing ratio of the liquid epoxy resin to the solid epoxy resin at normal temperature can be appropriately determined according to the required performance of the thermosetting adhesive.

In the case where the degree of flexibility of a film formed from a thermosetting adhesive containing a solid or liquid epoxy resin as described above is further improved and the peel strength of the film is further improved. It is particularly preferable to use a flexible epoxy resin in addition to those epoxy resins. In this case, the blending amount of the flexible epoxy resin in all the epoxy resins is too small, the effect of adding the flexible epoxy resin is not sufficiently obtained, and if too large, the heat resistance is reduced. Preferably it is 5 to 35% by weight, more preferably 5 to 25% by weight.

As such a flexible epoxy resin,
BPA type side chain type epoxy resins having an epoxy equivalent (g / ep) of 300 to 700 can be preferably used, and specifically, EP4000 (310 to 340 g / ep), EP400
5 (475-575 g / ep), EP 1307 (630 g / e)
p) (all manufactured by Asahi Denka Co., Ltd.) and the like can be preferably used.

As the latent curing agent, an imidazole-based latent curing agent having an action (curing) temperature of about 170 ° C. can be preferably used. By using an imidazole-based latent curing agent exhibiting such a curing temperature, when the thermosetting adhesive of the present invention is applied to an anisotropic conductive adhesive, the terminals can be securely adhered to each other and an electrical connection can be made. Can also be connected. In addition, the tact time during thermocompression bonding can be set to about several seconds, and good heat resistance can be imparted to the anisotropic conductive adhesive.

Here, as the imidazole-based latent curing agent, a conventionally known imidazole-based latent curing agent can be used. Among them, a microencapsulated imidazole-based latent curing agent is preferably used. it can. Examples of such a microencapsulated imidazole-based latent curing agent include an imidazole-based latent curing agent obtained by adducting imidazole with a urea or isocyanate compound, and further blocking the surface with an isocyanate compound to form a microencapsulated imidazole-based latent curing agent. Is preferably adducted with an epoxy compound, and the surface thereof is further blocked with an isocyanate compound to form a microencapsulated imidazole-based latent curing agent. Specifically, Novacure HX3941
HP, NOVACURE HX3921HP, NOVACURE HX3
721, NOVACURE HX3722, NOVACURE HX37
48, NOVACURE HX3088, NOVACURE HX374
1, Novacure HX3742, Novacure HX3613
(All manufactured by Asahi Ciba).

The amount of the imidazole latent curing agent used is
If the amount of the imidazole-based latent curing agent is too small, the heat resistance decreases and the conduction reliability deteriorates.If the amount is too large, the peel strength after heating and pressurization decreases and the storage stability deteriorates. , Preferably 10 to 200 parts by weight, more preferably 20 to 100 parts by weight.

As the latent curing agent, an amine-based latent curing agent can be used alone or simultaneously, in addition to the imidazole-based latent curing agent. Examples of the amine-based latent curing agent include polyamine-based latent curing agents (for example, EH
-4070S, EH-3731S, manufactured by Asahi Denka Co., Ltd.), 3rd
Grade amine-based latent curing agent (for example, EH3849S, manufactured by Asahi Denka Co., Ltd.), alkylurea-based latent curing agent (for example, E
H-3366S, manufactured by Asahi Denka Co., Ltd.).

On the other hand, if the amount of the amine-based latent curing agent is too small, the peel strength after heating and pressurization is lowered, and the conduction reliability is deteriorated. If it is too large, the storage stability is deteriorated.
25 to 5 parts by weight per 100 parts by weight of epoxy resin
5 parts by weight, more preferably 25 to 45 parts by weight.

The thermosetting adhesive of the present invention includes a known additive compounded in a conventional anisotropic conductive adhesive film and the like,
For example, an isocyanate-based crosslinking agent, a coupling agent such as an epoxysilane compound, an epoxy-modified silicone resin, or a thermosetting insulating resin such as a phenoxy resin can be appropriately compounded.

The thermosetting adhesive of the present invention can be produced by a conventional method. For example, it can be produced by uniformly mixing an epoxy resin and a latent curing agent in an alkylene glycol acetate monoether of the formula (1).

The thermosetting adhesive of the present invention can be used as a thermosetting adhesive film by forming a film. In this case, it can be manufactured by applying a thermosetting adhesive in a film shape on a release sheet (for example, a polyester sheet) and drying at a temperature at which the latent curing agent does not start the curing reaction.

The thermosetting adhesive of the present invention includes conductive particles (eg, metal particles such as solder particles and nickel particles, and gold-plated surfaces) as used in known anisotropic conductive adhesives. Composite particles such as styrene resin particles having a film formed thereon), and the storage stability of the obtained anisotropic conductive adhesive and further the anisotropic conductive adhesive film becomes good.

[0029]

The present invention will be described below in more detail with reference to examples.

Examples 1 to 5 and Comparative Examples 1 to 2 Paste thermosetting anisotropic conductive adhesives were prepared by uniformly mixing the components shown in Table 1.

[0031]

Table 1 Component parts by weight Solid BPA epoxy resin (EP1009, manufactured by Yuka Shell) 40 Liquid BPA epoxy resin (EP828, manufactured by Yuka Shell) 10 Latent curing agent (HX3941HP, manufactured by Asahi Ciba) 50 Au plating Resin particles (5 μm diameter) 5 Solvent 55 Example Boiling point Vapor pressure (25 ° C.) SP value 1 2-ethoxyethyl acetate 156.3 ° C. 2.0 mmHg 9.4 2 2-Methoxyethyl acetate 145.1 ° C. 5.0 mmHg−3 2-ethoxyethyl acetate 191.5 ° C. 0.3mmHg-4 1-Methoxyfluoro-2-acetate 146.0 ℃ 3.8mmHg 9.2 5 1-Ethoxyfluoro-2-acetate 158.0 ℃ 1.7mmHg 7.5 Comparative example 1 Toluene 110.6 ℃ 30mmHg 8.9 2 Ethyl acetate 77.1 ℃ 92mmHg 9.0

The obtained anisotropic conductive adhesive was placed in a room at 25 ° C. for a predetermined period (4 hours, 1 day, 7 days, 30 days).
After a day or 60 days), the resulting film was applied on a polyester release sheet and dried at 80 ° C. for 5 minutes to produce a 25 μm-thick anisotropic conductive adhesive film.

(Evaluation) "DSC heat value", "conduction resistance" and "residual solvent amount" of the obtained anisotropic conductive adhesive film
An evaluation test was carried out for and as described below.
Tables 2 and 3 show the obtained results.

In Comparative Examples 1 and 2, the results when the anisotropic conductive adhesive was left for one day were not good, so that the anisotropic conductive adhesive was left for 7 days, 30 days, and 6 days.
No measurements were taken after 0 days.

DSC The calorific value of the anisotropic conductive adhesive film immediately after preparation and the anisotropic conductive adhesive film aged for 7 days at 40 ° C.
The SC calorific value (mJ / mg) was measured. The less the difference between the two, the better the storage stability.

The anisotropic conductive adhesive film immediately after the conduction resistance was prepared and the anisotropic conductive adhesive film aged at 40 ° C. for 7 days were respectively
The continuity test IC chip and the continuity test wiring board were connected in accordance with a conventional method, and the continuity resistance was measured. If the conduction resistance value when using the anisotropic conductive adhesive film aged at 40 ° C. for 7 days is 1.2 times or less the conductive resistance value when using the anisotropic conductive adhesive film immediately after production, “ A "
It was evaluated as "B" if it was more than 1.2 times and not more than 2 times, and "C" if it was more than 2 times.

Residual Solvent Amount When the weight of the anisotropic conductive adhesive film immediately after preparation is a and the weight after heating it at 150 ° C. for 1 hour is b, [{(ab) / a} × 100] was determined as the residual solvent amount (wt%). The residual solvent amount at a level that does not cause any practical problem is 1% or less.

[0038]

[Table 2] Example 1 2 3 4 5 (Leaving time of anisotropic conductive adhesive = 4 hours) DSC heating value (immediately) 204.0 201.2 205.6 202.2 203.7 DSC heating value (after authentication) 202.5 202.8 201.3 203.9 205.1 Conduction resistance A A A A A A (Leaving time of anisotropic conductive adhesive = 1 day) DSC calorific value (immediately after production)-----DSC calorific value (after challenge)-----Conducting resistance AAAAA (anisotropic conductive adhesive) DSC heating value (immediately after production)-----DSC heating value (after challenge)-----Conducting resistance A A A A A A (Anisotropic conductive adhesive standing time = 30 days) ) DSC calorific value (immediately after fabrication)---209.7-DSC calorific value (after challenge)---203.3-Conduction resistance AAAAA (anisotropic conductive adhesive leaving time = 60 days) DSC calorific value (immediately) ) 201.4 202.0 201.1 210.8 198.8 DSC calorific value (after attack) 197.5 199.8 200.4 205.0 196.3 Conduction resistance A A A A A A Residual solvent amount (wt%) 0.52 0.48 0.70 0.50 0.65

[0039]

[Table 3]

From Table 3, it can be seen that the anisotropic conductive adhesive of Comparative Example 1 or Comparative Example 2 using toluene or ethyl acetate as a solvent can only secure storage stability of about 4 hours at 25 ° C. In contrast, the results in Table 2 indicate that the anisotropic conductive adhesives of Examples 1 to 5 using the specific alkylene glycol monoether acetate as the solvent had the intended storage even when stored at 25 ° C. for 60 days. It can be seen that stability can be obtained.

Further, from the results of the residual solvent amount in Tables 2 and 3, it can be seen that even when a specific alkylene glycol monoether acetate is used as the solvent, it can be sufficiently dried at a practically satisfactory level.

[0042]

According to the present invention, the storage stability of an insulating thermosetting adhesive itself containing an epoxy resin, a latent curing agent and a solvent can be improved, and it can be easily formed into a film. Moreover, the storage stability of the obtained adhesive film can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 5/14 H01B 5/14 Z F-term (Reference) 4J004 AA13 AA17 AA19 AB05 DB03 FA05 4J040 EC061 HB31 HC24 JA09 JB02 JB10 KA03 KA16 KA23 KA32 LA05 LA09 PA42 5G301 DA05 DA29 DA57 DD03 DD08 5G305 AA11 AB27 AB36 BA09 BA18 CA15 CB09 CD08 CD12 CD16 5G307 GA02 GC02 HA02 HB03 HC01

Claims (5)

[Claims] 1. A epoxy resin, in the heat-curable adhesive containing a latent curing agent and a solvent, said solvent has the formula (1) ## STR1 ## CH ₃ COOR ¹ OR ² (1) (In the formula, R ¹ Is a lower alkylene group, and R ² is a lower alkyl group.). 2. The thermosetting adhesive according to claim 1, wherein R ¹ is an ethylene group or a propylene group, and R ² is a methyl group or an ethyl group. 3. A thermosetting adhesive film obtained by applying the thermosetting adhesive according to claim 1 on a release sheet and drying. 4. An anisotropic conductive adhesive comprising conductive fine particles dispersed in the thermosetting adhesive according to claim 1. 5. An anisotropic conductive adhesive film obtained by applying the thermosetting adhesive according to claim 4 on a release sheet and drying.