JP2697169B2 - adhesive - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a heat-resistant adhesive excellent in low-temperature moldability and solvent resistance.

[Conventional technology]

Polyimide has the highest heat resistance among various resins, and is therefore widely used in the aerospace and electronics fields. Flexible printed wiring board (FP
C) is obtained by bonding a polyimide film, a copper foil and an adhesive. Conventionally, resins with low heat resistance such as epoxy resin and acrylic rubber are used as adhesives,
The heat resistance of the polyimide film cannot be exploited, and its use at high temperatures has been limited. To solve this problem, as disclosed in JP-A-57-181857, JP-A-57-63254, JP-A-61-551777, JP-A-62-275181, etc. A method has been proposed in which a polyimide film is adhered to each other or a polyimide film and a copper foil by using a plastic polyimide film as an adhesive.

[Problems to be solved by the invention]

JP-A-57-181857, JP-A-57-63254,
The method disclosed in JP-A-61-55177 and the like uses polyimide as an adhesive and thus has excellent heat resistance, but requires a bonding temperature of 320 ° C. or higher because the softening point of polyimide is high. . For this reason, there is a disadvantage that it cannot be used for bonding a material having low heat resistance.

Polyimides shown in JP-A-62-275181 can be bonded at 230 ° C. to 350 ° C. because of their low softening points.
Since this polyimide is dissolved in a solvent such as methylene chloride, there is a disadvantage that the molded article has poor solvent resistance.

The present invention provides a heat-resistant adhesive which can be molded at low temperature and has excellent solvent resistance.

[Means for solving the problem]

The adhesive in the present invention has the general formula (I) (Where R is the formula (a) Or formula (b) And a polyimide resin having a repeating unit represented by the formula:

The polyimito resin preferably has a softening point of 130 to 180.
° C. If the softening point is too low, the physical properties of the polyimide resin tend to decrease.

Among the above precursors, polyamic acid has the general formula (II) (Wherein, R is the same as in the general formula (I)).

Further, as another precursor, there is a polyimide precursor in which polyamic acid is partially imidized.

In the present specification, the polyimide resin, the polyamic acid, and the partially imidized polyimide precursor are collectively referred to as a polyimide resin.

The polyimide resin is composed of 4,4 [1,4-phenylenebis (1-methylethylidene)] bisaniline (BAP) and 4,4 [1,4-phenylenebis (1-methylethylidene)] bisaniline (BAP).
4 '-[1,4-phenylenebis (1-methylethylidene)] bisphenylbistrimellitate dianhydride (PAPB
T) or 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisaniline (BAM)
4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenylbistrimellitate dianhydride (BAMB
It can be produced by reacting T).
In this case, the degree of imidization can be appropriately adjusted by selecting and reacting BAP or BAM as a diamine and BAPBT or BAMBT as an acid dianhydride under appropriate conditions. For example, in an organic solvent, at 100 ° C or higher, particularly at 180 ° C or higher,
If necessary, an almost completely imidized polyimide resin can be produced by reacting in the presence of a catalyst such as tributylamine, triethylamine, triphenyl phosphite, etc. (The catalyst is based on the total amount of the reaction components.) It is preferable to use 0 to 15% by weight, particularly preferably 0.01 to 15% by weight).
In particular, when the reaction is carried out at 50 ° C. or lower, a polyamic acid which is a precursor of the polyimide resin and hardly imidized can be produced. Further, a polyimide resin precursor in which imidization has partially progressed can be produced.

The polyamic acid or the polyimide precursor partially undergoing imidization is further imidized by heating to 100 ° C. or higher, particularly 120 ° C. or higher, or acid anhydrides such as acetic anhydride, propionic anhydride, and benzoic anhydride. A ring-closing agent such as carbodiimide such as dicyclohexylcarbodiimide, and, if necessary, a ring-closing catalyst such as pyridine, isoquinoline, trimethylamine, aminopyridine, imidazole and the like to chemically ring-close (imidize) (the ring-closing agent and the ring-closing catalyst are
Each of them is preferably used in an amount of 1 to 8 mol per 1 mol of the acid anhydride) to produce a polyimide resin.

As the organic solvent, N-methyl-pyrrolidone (NM
P), N, N'-dimethylacetamide, N, N'-dimethylformamide (DMF, dimethylsulfoxide, sulfolane, hexamethylphosphoric triamide, 1,3-dimethyl-
Examples include aprotic polar solvents such as 2-imidazolidone and the like, and phenol solvents such as phenol, cresol, xylenol and p-chlorophenol.

These solvents include benzene, toluene, xylene, methyl ethyl ketone, acetone, tetrahydrofuran, dioxane, monoglyme, diglyme, methyl cellosolve, cellosolve acetate, methanol, ethanol,
Solvents such as isopropanol, methylene chloride, chloroform, tricrene, tetrachloroethane and the like can be used as a mixture.

In producing the above-mentioned polyimide resin and its precursor (including polyamic acid), a solid-phase reaction,
It is also possible to use a melting reaction at a temperature of not more than ° C.

The polyimide resin is a diisocyanate corresponding to the diamine BAP or BAM and BAPT or acid dianhydride
It can be manufactured in one step using BAMBT. At this time, it is sufficient that the reaction temperature is at least room temperature, especially at least 60 ° C.

In the present invention, the acid dianhydride and its reaction partner are preferably used in approximately equimolar amounts, but an excess amount of any one is allowed to be 10 mol%, particularly preferably up to 5 mol%.

In the above, the acid dianhydride may be used in the form of an acid derivative such as a diester.

The polyimide resin used in the present invention is also N, N '
-[4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline] bistrimellitimide (hereinafter referred to as "imidodicarboxylic acid I") and 4,4'-[1,4-phenylenebis (1- Methylethylidene)] bisphenol, or N, N '-[4,4'-[1,3-phenylenebis (1-methylethylidene)] bisaniline] bistrimellitimide (hereinafter referred to as "imidodicarboxylic acid II")
) And 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenol. In this case, the above-mentioned imidodicarboxylic acid I or II and the above-mentioned bisphenol are subjected to a heat polycondensation reaction or a direct polycondensation reaction using a condensing agent such as a phosphite or tosyl chloride, a diacid chloridone of the above-mentioned imidodicarboxylic acid I or II And a low-temperature polymerization reaction of the above-mentioned bisphenol and the like.

The methods (1) and (2) may be performed in the same manner as in the ordinary polyester polycondensation method. In the case of direct polycondensation, the above-mentioned charge, Polymer 35 (2) 128 (1986), Higashi Fukuji, Journal of the Adhesion Society of Japan, 24 (12) 504 (1988), Ryuichi Takazawa et al., Polyme
r preprints, Japan, 34 (6) 1345 (1985).

Further, the polyimide resin in the present invention can be produced as polyamic acid by reacting metrimetic anhydride, BAP or BAM and the bisphenol in the same vessel using a condensing agent such as tosyl chloride, and further thereafter. It can be obtained as a polyimide by a method of heat ring closure or chemical ring closure. See Hozumi Tanaka et al., Proceedings / Abstructs of
Third International Conference on Polyimide p.64
(1988).

The adhesive in the present invention contains the above-mentioned polyimide resin, but may be in any form such as a powder, a solution, a film and the like. When used in the form of a solution, the precursor of the polyimide-based resin is selected from the above-mentioned organic solvents and dissolved therein.

The form of the adhesive in the present invention is preferably in the form of a film from the viewpoint of easy handling.

In order to prepare a film-like adhesive, an appropriate one of the above-mentioned organic solvents is selected from the above-mentioned organic solvents and the resulting resin is dissolved (varnish) in a drum, steel belt, glass plate, resin, or the like. It can be made by casting on a support such as a film and removing most of the solvent by heating.After that, the formed film is peeled off.
It can be a self-supporting film. in this case,
The polyimide resin is a polyamic acid or a partially imidized precursor, but is further heated by a method of immersing the film in a solution in which the ring-closing agent and a ring-closing catalyst are dissolved if necessary. These can be made into a polyimide resin. Further, when the polyimide resin is a polyimide resin, it can be formed into a film by dissolving and forming the polyimide resin.

Further, the adhesive of the present invention may be in a form (prepreg) in which a woven or non-woven fabric made of glass fiber, carbon fiber, aramid fiber or the like is impregnated with a polyimide resin.
These impregnate the woven or nonwoven fabric with the varnish described above,
Created by drying. Also in this case, the polyimide resin is a polyamic acid or a partially imidized polyimide precursor, but can be a polyimide resin as in the case of the self-supporting film described above.

In the present invention, it is preferable to use a polyimide resin as the polyimide resin because there is little danger of generating a void.

In the adhesive of the present invention, in addition to the polyimide resin, ceramics such as alumina, silica, glass, metal powder, whiskers, short fibers such as carbon fiber, glass fiber, and aramid fiber, fluorine resin particles, pigments, and the like are mixed. It may be. Further, a coupling agent such as silane or titanium may be mixed in order to further improve the adhesiveness.

Examples of the adherend to which the adhesive of the present invention is applied include a polyimide film, a metal foil such as copper, iron, and aluminum, a metal plate, and a ceramic plate.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to examples, but the present invention is not limited to these ranges.

Example 1 34.4 g of BAP and 415 g of N, N-dimethylformamide were placed in a four-necked flask equipped with a stirrer, a thermometer, a calcium chloride tube, and a nitrogen gas inlet tube and dissolved.
T69.4g was added little by little. The reaction was performed at 10 ° C. or lower for 3 hours to obtain a polyamic acid varnish.

The varnish was cast on a glass plate using an applicator, and dried at 80 ° C. for 30 minutes. After the film was peeled off from the glass plate, it was dried at 150 ° C. for 2 hours to obtain an adhesive film (thickness: 25 μm) made of a polyimide resin having a softening point of 165 ° C.

This adhesive film is coated with a 35μm thick single-sided roughened copper foil
Sandwich between 50μm polyimide film, 250 ℃, 30kg
Heat and pressure were applied for 15 minutes at f / cm ² . According to JIS-C-6481,
Measured 90 ゜ copper foil peel strength, 2.1kg at room temperature
f / cm, 1.3 kg f / cm at 150 ° C. When the copper-clad substrate was immersed in methylene chloride, the appearance did not change.

Example 2 An adhesive film (thickness: 30 μm) made of polyimide resin having a softening point of 150 ° C. was obtained in the same manner as in Example 1 except that 34.4 g of BAM and 69.4 g of BAMBT were used.

This adhesive film is coated with a 35μm thick single-sided roughened copper foil
Sandwiched between 1mm aluminum plates, 200 ℃, 50kg f / c
Heating and pressurizing was performed at m ² for 30 minutes to obtain a copper-clad substrate. Peel strength of this board and copper foil is 2.2kg f / cm at room temperature, 1.4kg f / cm at 150 ℃
It was. When the copper-clad substrate was immersed in methylene chloride, the appearance did not change.

Comparative Example 1 A 50 μm-thick polyimide resin was prepared in the same manner as in Example 1, except that metaphenylenediamine and 2,2-bis (p-trimethoxyphenyl) propane dianhydride were used in equimolar amounts.
Example 2 was obtained by using this adhesive film.
In the same manner as described above, a copper-clad substrate was obtained by heating and pressing at 250 ° C. and 50 kgf / cm ² for 30 minutes. The copper foil peel strength of this board is 1.
It was 8 kg f / cm. When the copper-clad substrate was immersed in methylene chloride, the adhesive layer was dissolved.

Comparative Example 2 Equimolar amounts of 3,3'-diaminobenzophenone and 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride were used.
25 μm thick made of polyimide resin in the same manner as in Example 1.
m of the adhesive film was produced.

Using this film, 250
At 30 ° C., 30 kg f / cm ² and heating and pressing for 30 minutes, no adhesion was observed. The copper-clad substrate obtained by heating and pressing at 300 ° C., 30 kg f / cm ² for 30 minutes had a very low peel strength of 0.2 kg f / cm at room temperature.

Example 3 After the polyamic acid varnish of Example 1 was applied to an aluminum plate having a thickness of 1 mm, the coating was placed at 100 ° C. for 30 minutes in a vacuum drier.
After drying at 1 ° C. for 1 hour, an adhesive layer made of a polyimide resin having a thickness of 30 μm was formed. A single-sided roughened copper foil having a thickness of 35 μm was overlaid on the adhesive layer and heated and pressed at 200 ° C., 50 kgf / cm ² for 30 minutes to obtain a copper-clad substrate. The copper foil peeling strength of this substrate was 2.0 kg f / cm at room temperature and 1.2 kg f / cm at 150 ° C. Also,
When this copper-clad substrate was immersed in methylene chloride, the appearance did not change.

Example 4 A polyamide acid varnish was obtained in the same manner as in Example 1 except that 34.2 g of BAM and 69.4 g of BAMBT were used.

This varnish was applied on the roughened side of a single-side roughened copper foil having a thickness of 35 μm, and dried at 80 ° C. for 30 minutes and at 150 ° C. for 2 hours to obtain a thickness of 2 μm.
An adhesive layer made of a 5 μm polyimide resin was formed.
This copper foil with adhesive was laminated on a polyimide film having a thickness of 25 μm, and then heated and pressed at 230 ° C. and 30 kgf / cm ² for 1 hour to obtain a copper-clad substrate. The copper foil peeling strength of this board at room temperature
It was 1.4 kg f / cm at 2.3 kg f / cm and 150 ° C, and the appearance did not change even when immersed in methylene chloride.

A part of the adhesive film (polyimide resin) obtained in Example 1 and Example 2 was sampled, and the following physical properties were measured.

Resin obtained in Example 1: (1) Thermal decomposition temperature 431 ° C. (2) Main absorption in IR spectrum (KBr method) 1785 cm ⁻¹ (imide group) 1730 cm ⁻¹ (ester group) 2970,2880 cm ⁻¹ ( (Methyl group) Resin obtained in Example 2: (1) Thermal decomposition temperature 418 ° C (2) Main absorption in IR spectrum (KBr method) 1790 cm ^-1 (imide group) 1730 cm ^-1 (ester group) 2980,2880 cm ^-1 (Metal group) As described above, the resin obtained in Example 1 is represented by the general formula (I)
Is a polyimide resin having a repeating unit in which R is represented by the formula (a), and the resin obtained in Example 2 is a resin in which R in the general formula (I) is represented by the formula (b) It was a polyimide resin having a repeating unit.

〔The invention's effect〕

The adhesive of the present invention has excellent low-temperature moldability, solvent resistance and heat resistance.

Claims (4)

(57) [Claims] (1) a repeating unit represented by the general formula (I): (Where R is the formula (a) Or formula (b) An adhesive containing a polyimide resin represented by: (2) a repeating unit represented by the general formula (II): However, in the formula, R is the formula (a) Or formula (b) An adhesive containing a polyamic acid represented by: (3) 4,4 '-[1,4-phenylenebis (1-methylethylidene)] bisaniline and 4,4'-[1,4-phenylenebis (1-methylethylidene)] bisphenylbistrimellitate Reaction of dianhydride or 4,4 '-[1,3
-Phenylenebis (1-methylethylidene)] binaniline and a polyimide resin obtained by reacting 4,4 '-[1,3-phenylenebis (1-methylethylidene)] bisphenylbistrimellitate dianhydride. Including adhesive. 4. The adhesive according to claim 1, wherein the adhesive is in the form of a film.