JPH10219225A - Adhesive composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of improving adhesiveness under a room temperature condition, useful for bonding flexible printed board, by using a siloxane polyimide soluble in an organic solvent of general purpose as an adhesive component. SOLUTION: This composition comprises (A) a siloxane polyimide composed of a copolymer of (i) a diaminopolysiloxane-alicyclic diamine mixture and (ii) an aromatic tetracarboxylic acid dianhydride, (B) an epoxy resin, (C) a diamine- based curing agent, (D) a fluorine surfactant and (E) an organic solvent. For example, a reaction product of a compound of the formula (R is a 2-6C bifunctional hydrocarbon; R1 to R4 are each a 1-5C alkyl or phenyl; (n) is 0-30), etc., and 1,3-bis(aminomethyl)cyclohexane, etc., is preferably used as the component (i).

Description

[Detailed description of the invention]

[0001]

FIELD OF THE INVENTION This invention relates to adhesive compositions. More particularly, it relates to a polyimide-based adhesive composition that exhibits good adhesiveness even under room temperature conditions.

[0002]

2. Description of the Related Art Conventionally, a heat-resistant adhesive mainly composed of aromatic polyimide or the like is used for adhesion between a base material and a copper foil in a flexible printed circuit board. However, since aromatic polyimides generally do not dissolve in general-purpose organic solvents, they are used as solutions of their precursors, aromatic polyamic acids. In this case, there are problems such as occurrence of void phenomenon and thermal deterioration of the electronic parts themselves.

On the other hand, Japanese Patent Application Laid-Open No. 61-118424 and Japanese Patent Application Laid-Open No. 1-1
Japanese Patent No. 21325 and others disclose solvent-soluble siloxane polyimides. There is a problem that the substrate curls greatly when it is applied to the surface and dried.

[0004]

The applicant has previously used siloxane polyimide, which is soluble in general-purpose organic solvents, as the main component of adhesives for bonding between substrates and copper foils of flexible printed circuit boards. An adhesive composition containing a solvent-soluble siloxane polyimide comprising a copolymer of a diaminopolysiloxane-alicyclic diamine mixture and an aromatic tetracarboxylic dianhydride, an epoxy resin, a diamine-based curing agent, and an organic solvent. proposed a composition (Japanese Patent Application No. 8-354,825).

[0005] An adhesive composition having such a composition is
Although it has excellent heat-resistant adhesiveness, it is not necessarily satisfactory in terms of adhesiveness under room temperature conditions, and new improvements in this point have been sought.

SUMMARY OF THE INVENTION An object of the present invention is to provide an adhesive composition containing a general-purpose organic solvent-soluble siloxane polyimide as an adhesive component, which has improved adhesiveness under room temperature conditions.

[0007]

DISCLOSURE OF THE INVENTION The object of the present invention is to:
A siloxane polyimide comprising a copolymer of a diaminopolysiloxane-alicyclic diamine mixture and an aromatic tetracarboxylic dianhydride, an epoxy resin, a diamine curing agent,
This is achieved by an adhesive composition containing a fluorosurfactant and an organic solvent.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION A compound represented by the following general formula is used as the diaminopolysiloxane which is one component of the diamine compound which reacts with the aromatic tetracarboxylic dianhydride. R: a divalent hydrocarbon group having 2 to 6 carbon atoms, preferably 3 to 5 R ₁ to R ₄ : a lower alkyl group having 1 to 5 carbon atoms, a phenyl group n: an integer of 0 to 30, preferably 4 to 12 integers

Examples of this compound include compounds in which R and R ₁ to R ₄ are the following combinations of substituents. R _{R1 R2 R3 R4 ( CH2 ) 3CH3CH3CH3CH3 _ _ ( CH2 ) 4CH3CH3CH3CH3 _ _ ( CH2 ) 3CH3C6H5CH3C6H5 _ _ _ _ pC6H4CH3CH3CH3CH3 _ _ _ _ _}

In practice, commercially available products such as Toshiba Silicone Products TSL9386, TSL9346, TSL9306, Toray Dow Corning Products BY16-853U, Shin-Etsu Chemical Products X-22-161AS, Nihon Unicar Products F2-053-01, etc. can be used. can be done.

Alicyclic diamines, which are the other diamine compounds, generally include diamines having one or more cyclohexane rings, such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, 1,
3-diaminocyclohexane and the like are used alone or as a mixture.

These diaminopolysiloxanes and alicyclic diamines contain about 95 to 5 mol %, preferably about 80 to 80 mol % of the former.
It is used in a proportion of 40 mol % and of the latter in a proportion of about 5 to 95 mol %, preferably about 20 to 60 mol %. If the ratio of the latter is less than this range, an adhesive composition having excellent heat-resistant adhesive effect cannot be obtained, whereas if the ratio is greater than this range, the adhesive composition lacks flexibility.

Aromatic tetracarboxylic dianhydrides reacting with these diamine compound mixtures include 3,3',4,4
´-benzophenonetetracarboxylic dianhydride, 3,3´,
4,4´-diphenylsulfonetetracarboxylic dianhydride,
4,4'-oxydiphthalic dianhydride, 4,4'-biphthalic dianhydride, 2,2'-diphthalic dianhydride propane, diphthalic dianhydride methane, pyromellitic dianhydride, 2, 2´-
(Hexafluoroisopropylidene)diphthalic dianhydride or the like is used in an equimolar ratio with respect to the diamine compound mixture.

The reaction between the diamine compound mixture and the aromatic tetracarboxylic dianhydride is preferably carried out in an aprotic polar solvent such as dimethylformamide, dimethylacetamide, N-methylpyrrolidone, cresol, It is also carried out in a polar solvent such as pyridine. In practice, it is carried out by dropping the diamine compound mixture at about 0 to 10°C into a polar solvent solution of the aromatic tetracarboxylic dianhydride.

Since this reaction product is a polyamic acid which is a polyimide precursor, a dehydration reaction is carried out to convert it into a polyimide. The dehydration reaction is preferably carried out by using a dehydrating agent such as acetic anhydride and reacting at about 100 to 200°C.

The siloxane polyimide, which is the product of the polyimidation reaction, has repeating units (a) and (b) represented by the following general formula, for example when the alicyclic diamine is bis(aminomethyl)cyclohexane It is also considered a block copolymer, and its weight average molecular weight Mw (measured by GPC; polystyrene conversion) is about 10,000 to 100,000, preferably about 25,000 to 75,000. and Ar: Aromatic tetracarboxylic acid residue

An adhesive composition is formed by adding an epoxy resin, a diamine curing agent, a fluorosurfactant and an organic solvent to the resulting siloxane polyimide.

As the epoxy resin, bisphenol A
type, biphenyl type, glycidylamine type, novolak type, etc. are used.
28 etc. is used. These epoxy resins are used in a proportion of about 0.1 to 30 parts by weight, preferably about 0.1 to 10 parts by weight, per 100 parts by weight of siloxane polyimide. If the proportion of the epoxy resin used is less than this, the adhesiveness will be lowered, while if it is used more than this, the heat resistance will be reduced.

Diamine-based curing agents are used as curing agents for epoxy resins. Isophoronediamine, diethylenetriamine, triethylenetetramine and the like are used in a proportion of about 0.1 to 30 parts by weight, preferably about 0.1 to 10 parts by weight, per 100 parts by weight of the siloxane polyimide.

[0020] As the fluorosurfactant, ammonium perfluoroaliphatic carboxylate such as ammonium perfluorooctanoate and ammonium perfluorononanoate, sodium perfluorohexenyloxybenzenesulfonate and the like are used. Commercially available products, such as PFE type, DFE type, and FT type NEOS products, contain about 0.1 to 10% per 100 parts by weight of siloxane polyimide.
It is used in proportions by weight, preferably about 1 to 5 parts by weight.
If the proportion is less than this, no improvement in adhesion under room temperature conditions is achieved, while if the proportion is greater than this, phase separation from the siloxane polyimide will occur, making it impossible to obtain a clean film.

[0021] Each of the above components is added to a general-purpose low-boiling organic solvent such as methyl ethyl ketone, chloroform, tetrahydrofuran, toluene and the like in an amount of about 10 to 50% by weight, preferably about 20 to 40% by weight.
The weight percent solids concentration is dissolved to form an adhesive composition solution therein.

[0022] This adhesive composition solution is effectively used for adhesion between the base material of a flexible printed circuit board and a copper foil. In use, this solution is applied to a flexible base material such as a polyimide film, and a copper foil that constitutes the printed wiring is laminated thereon. Effective adhesion is achieved by curing for about 12 hours.

[0023]

Effect of the Invention The adhesive having the novel siloxane polyimide as an effective adhesive component provided by the present invention is an aromatic polyimide that is insoluble even in aprotic polar solvents and is soluble in general-purpose low-boiling-point organic solvents. As a result, mild adhesive application conditions are possible, and unlike conventional aromatic polyimide adhesives, high temperature and long time pressure bonding are not required, and low temperature and short time adhesion is possible. Excellent effects are also shown in terms of adhesiveness under room temperature conditions. Further, the flexible printed circuit board in which the base material and the copper foil are effectively bonded using this adhesive composition does not exhibit a phenomenon such as large curling of the circuit board.

[0024]

EXAMPLES The present invention will now be described with reference to examples.

Examples 1 to 3 In a separable flask with a capacity of 100 ml, 3,3
´,4,4´-benzophenonetetracarboxylic dianhydride 1.6
1 g (5 mmol) and 15 ml of N-methylpyrrolidone are charged and the solution is cooled with ice. A predetermined amount of diaminopolysiloxane [Toshiba Silicone Products TSL938
6; in the general formula, R is a ( _CH2 ) ₃ group, and _R1 to _R4 are all _CH3 groups]
and 1,3-bis(aminomethyl)cyclohexane from about 0 to 1
After adding while maintaining the temperature at 0° C., the solution was dissolved by stirring at room temperature for 30 minutes. After that, the temperature was raised to 50° C. and stirred for 3 hours, and then the temperature was raised to 200° C. and stirred for 3 hours to cause a dehydration reaction. After completion of the reaction, siloxane polyimide was obtained by reprecipitation in water.

To 100 parts by weight of the obtained siloxane polyimide, 1 part by weight of an epoxy resin (Epikote 604), 4,4'
- Add 1 part by weight of diaminodiphenyl sulfone and 1 part by weight of a fluorosurfactant (NEOS PFE-800B),
It was prepared as a methyl ethyl ketone solution with a solid concentration of 40% by weight. This solution was applied to a polyimide film and 14
After drying at 0°C for 5 minutes, under the conditions of 37 kg/cm ² G and 185°C
After preheating for 30 seconds, press for 70 seconds and bond with copper foil.
Further at 180° C. for 4 hours (Example 1), 12 hours (Example 2) or
After curing for 24 hours (Example 3), the 90° peel strength (tensile strength) under room temperature conditions was measured.

Examples 4-6 In Examples 1-3, Epicoat was used as the epoxy resin.
154 was used at 5 parts by weight.

Example 7 In Example 2, the diaminopolysiloxane was BY16-853U manufactured by Toray Dow Corning [wherein R is (CH ₂ )
₃ groups, R ₁ to R ₄ are CH ₃ groups] in the same amount to produce a siloxane polyimide, prepare an adhesive composition using it, and measure the 90° peel strength under room temperature conditions. rice field.

The results obtained are shown in the following table. The values in parentheses are measured values for an adhesive composition containing no fluorosurfactant. Example peel strength (kg/cm) 1 1.24 (0.89) 2 1.33 (0.81) 3 1.38 (0.81) 4 1.53 (0.95) 5 1.30 (0.95) 6 1.41 (0.95) 7 1.13 (0.93)

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Claims (2)

[Claims] [Claim 1] Contains a siloxane polyimide comprising a copolymer of a diaminopolysiloxane-alicyclic diamine mixture and an aromatic tetracarboxylic dianhydride, an epoxy resin, a diamine-based curing agent, a fluorine-based surfactant, and an organic solvent. An adhesive composition formed by 2. The adhesive composition according to claim 1, which is used for bonding between a base material and a copper foil of a flexible printed circuit board.