JPH0770318A - Heat-resistant adhesive - Google Patents

Abstract

PURPOSE:To obtain a heat-resistant adhesive excellent not only in heat resistance but also in processibility, adhesiveness, and esp. low moisture absorption. CONSTITUTION:The title adhesive is based on a thermoplastic copolyimide which is obtd. by reacting an acid dianhydride component comprising 50-99mol% diester acid dianhydride of formula I wherein Ar1 is a divalent org. group, 1-50mol% 5-(2,5-dioxotetrahydrofuryl)-3-methyl-3-cyclohexene-1, 2-dicarboxylic dianhydride, and 0-30mol% acid dianhydride other than the foregoing two dianhydrides and represented by formula III wherein Ar2 is a tetravalent org. group with at least one diamine of the general formula: H2N-Ar3-NH2 wherein Ar3 is a divalent org. group in a molar amt. of the diamine virtually equal to that of the dianhydride component.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to heat resistant adhesives.
More specifically, the present invention relates to a heat-resistant adhesive composed of a thermoplastic polyimide copolymer having excellent heat resistance, processability and adhesiveness, and particularly excellent in low hygroscopicity.

[0002]

2. Description of the Related Art In recent years, electronic devices have been highly functionalized, highly functionalized, and miniaturized at an extremely high speed. However, weight reduction is required. For this reason, a wiring board on which electronic components are mounted is also a flexible printed circuit board (hereinafter, referred to as F
It is called a PC. ) Is attracting attention, and demand is rapidly increasing.

At present, flexible printed boards are often manufactured by bonding a polyimide film and a copper foil together using an adhesive such as epoxy resin or acrylic resin. However, flexible printed boards using these conventional adhesives have a problem that swelling or peeling may occur in the adhesive layer when exposed to high temperature in the soldering process, and improvement in heat resistance of the adhesive is desired. It was

Therefore, as a heat resistant adhesive, 3,3 ',
A substrate such as a polyimide film and a copper foil using an adhesive film obtained from a resin composition obtained by mixing an aromatic polyimide obtained from 4,4′-benzophenonetetracarboxylic dianhydride and an aromatic diamine and polymaleimide There has been proposed a method of manufacturing an FPC for adhering (see Japanese Patent Laid-Open No. 2-138789). However, this method does not improve the disadvantage of polyimide, which requires high temperature and high pressure for adhesion and has high hygroscopicity, and has a problem that the electrical characteristics after hygroscopicity are poor.

Further, in order to improve the processability of the polyimide, 5- (2,5-dioxotetrahydrofuryl) 3-methyl-3-cyclohexene-1,2 as an acid dianhydride is used.
A polyimide resin using 2-dicarboxylic acid dianhydride has been proposed. This polyimide resin is reported to be soluble in a solvent (Japanese Patent Publication No. 57-121035).
No.) had a problem that the molecular weight was lowered during imidization and sufficient mechanical strength could not be obtained.

Therefore, in view of the above situation, the present inventors consider
In order to provide a heat-resistant adhesive composed of a thermoplastic polyimide copolymer having excellent heat resistance, excellent workability, adhesiveness, and particularly excellent hygroscopicity, the above-mentioned conventional problems are solved. As a result of repeating the above, the present invention was achieved.

[0007]

To achieve this object, the gist of the heat-resistant adhesive according to the present invention is that the total amount of all acid dianhydride compounds is represented by the general formula (1)

[Chemical 9] (In the formula, Ar ₁ represents a divalent organic group.) 50 to 99 mol% of a diester dianhydride represented by

[Chemical 10] 1 to 50 of 5- (2,5-dioxotetrahydrofuryl) 3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride (hereinafter referred to as MCDA) represented by
mol%, and the general formula (2) other than the diester dianhydride represented by the general formula (1) and MCDA 11

[Chemical 11] (In the formula, Ar ₂ represents a tetravalent organic group.) 0 to 30 mol% of the acid dianhydride, and a general formula (3) in a substantially equimolar amount to the total acid dianhydride compound. H ₂ N—Ar ₃ —NH ₂ (3) (wherein, Ar ₃ represents a divalent organic group), which is a thermoplastic polyimide copolymer obtained by reacting at least one diamine compound. It consists of

In the heat-resistant adhesive, Ar ₁ in the general formula (1) is

[Chemical 12] Is at least one selected from the group of divalent organic groups shown in.

In the heat-resistant adhesive, Ar ₂ in the general formula (2) is

[Chemical 13] At least 1 selected from the group of tetravalent aromatic groups shown in
It is to be a seed.

In the heat-resistant adhesive, Ar ₃ in the general formula (3) is

[Chemical 14] At least 1 selected from the group of divalent aromatic groups shown in
It is to be a seed.

Further, in such a heat resistant adhesive, a compound represented by the general formula (4) is used with respect to the total amount of all diamine compounds.

[Chemical 15] (In the formula, Ar ₄ represents a divalent organic group.) It is composed of a thermoplastic polyimide copolymer obtained by using 1 to 50 mol% of a diester diamine compound.

Further, in such a heat resistant adhesive, Ar ₄ in the general formula (4) is

[Chemical 16] Is at least one selected from the group of divalent organic groups shown in.

[0013]

EXAMPLES The heat-resistant adhesive according to the present invention will be described below along with its manufacturing method.

First, a method for producing a solution of a polyamic acid copolymer which is a precursor of a thermoplastic polyimide copolymer used as a heat resistant adhesive according to the present invention will be described. A diamine represented by the general formula (3) H ₂ N—Ar ₃ —NH ₂ (3) (wherein Ar ₃ represents a divalent organic group) in an atmosphere of an inert gas such as argon or nitrogen. The compound is dissolved or diffused in an organic solvent.
The solution of the general formula (1)

[Chemical 17] (In the formula, Ar ₁ represents a divalent organic group.)

[Chemical 18] A mixture of 5- (2,5-dioxotetrahydrofuryl) 3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride (hereinafter referred to as MCDA) represented by Can be added in the form of to obtain a polyamic acid solution which is a precursor of polyimide.

At this time, in order to obtain another copolymer,

[Chemical 19] (In the formula, Ar ₂ represents a tetravalent organic group.) The organic tetracarboxylic dianhydride represented by the formula should be added in a proportion of 0 to 30 mol% with respect to the total amount of all acid dianhydride compounds. Is also possible.

At this time, in order to obtain another copolymer, the compound represented by the general formula (4):

[Chemical 20] (In the formula, Ar ₄ represents a divalent organic group.) The diester diamine compound represented by the formula (1) may be previously dissolved in a solvent at a ratio of 1 to 50 mol% based on the total amount of all diamine compounds. Is.

In these reactions, contrary to the above, first, a solution of an acid dianhydride component may be prepared, and a solution or slurry of a solid or organic solvent of a diamine component may be added to this solution.

Here, the ratio of the acid dianhydride component is such that the diester acid dianhydride represented by the general formula (1) and MCDA.
And the molar ratio of the acid dianhydride represented by the general formula (2) is preferably 90: 10: 0 to 50:30:20, and more preferably 70:20:10 to 60 :.
20:20 is preferred.

The reaction temperature at this time is -10 to 50 ° C, more preferably -5 to 20 ° C. Reaction time is from 30 minutes
6 hours.

By such a reaction, a polyamic acid copolymer, which is a precursor of the thermoplastic polyimide copolymer which is the heat resistant adhesive of the present invention, is produced.

Examples of the organic solvent used in the reaction for producing the polyamic acid copolymer solution include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, N, N-dimethylformamide, N, N-.
Formamide solvents such as diethylformamide, N, N
Examples thereof include acetamide-based solvents such as dimethylacetamide and N, N-diethylacetamide. These may be used alone or as a mixed solvent of two or three or more. Further, it can be used as a mixed solvent with a non-solvent of polyamic acid such as acetone, methanol, ethanol, isopropanol, and benzenemethylcellosolve together with these polar solvents.

By the way, as the diamine component used in the present invention, although a diamine compound of any structure represented by the general formula (3) is available, the Ar ₃ group is 2
It is preferably a valent organic group, and particularly preferably an aromatic group. Illustrative examples of this Ar ₃ group include Chemical formula 21 and Chemical formula 22

[Chemical 21]

[Chemical formula 22] Can be mentioned. More specifically, from the viewpoint of the balance of various characteristics,

[Chemical formula 23] It is preferable to use at least one selected from

In the present invention, it is also possible to use a diester diamine compound having any structure represented by the general formula (4) in combination with the diamine compound represented by the general formula (3). That is, the Ar ₄ group is available everything if divalent organic group, specific examples, of 24

[Chemical formula 24] Can be mentioned. More specifically, from the viewpoint of the balance of various characteristics,

[Chemical 25] It is preferable to use at least one selected from

As the acid dianhydride component used in the present invention, a diester acid dianhydride having any structure represented by the above general formula (1) can be used, but this Ar ₁ group is divalent. Is an organic group, and particularly preferably an aromatic group. A concrete example of this Ar ₁ group is:

[Chemical formula 26] Can be mentioned. More specifically, from the viewpoint of balancing various characteristics, 27

[Chemical 27] It is preferable to use at least one selected from

Further, in the present invention, as the acid dianhydride component,
It is also possible to simultaneously use an organic tetracarboxylic dianhydride having another structure. In essence, organic tetracarboxylic dianhydrides of any structure can be used,
In particular, those represented by the above general formula (2) are preferable, and the Ar ₂ group is preferably a tetravalent organic group and is preferably an aromatic group. Specific examples of this Ar ₂ group are Chemical formula 28 and Chemical formula 29

[Chemical 28]

[Chemical 29] Can be mentioned. More specifically, from the viewpoint of the balance of various characteristics,

[Chemical 30] It is preferable to use at least one selected from

Next, in order to obtain a polyimide copolymer from the polyamic acid copolymer solution obtained by the above method, a method of thermally and / or chemically performing dehydration ring closure (imidization) may be used.

Explaining by way of example, in the method of thermal dehydration ring closure (imidization), the solution of the polyamic acid copolymer is supported on a support plate, an organic film such as PET, or a support such as a drum or an endless belt. It is cast or coated on to form a film, and dried to obtain a film having self-supporting property.
This drying is preferably carried out at a temperature of 150 ° C. or lower for about 5 to 90 minutes. Next, this is further heated and dried to imidize to obtain a polyimide film made of the polyimide copolymer used in the present invention. The temperature during heating is 150-350 ° C
Temperatures in the range of are preferred. There is no limitation on the rate of temperature increase during heating, but it is preferable that the maximum temperature reaches the above temperature by gradually heating. The heating time varies depending on the film thickness and the maximum temperature, but is generally preferably in the range of 10 seconds to 5 minutes after the maximum temperature is reached. When the film having the self-supporting property is heated, it is preferable to peel the film from the support, fix the end portion in this state and heat the film to obtain a polymer having a small linear expansion coefficient.

In the chemical dehydration ring closure (imidization) method, a dehydrating agent in a stoichiometric amount or more and a catalytic amount of a tertiary amine are added to the solution of the polyamic acid copolymer to thermally dehydrate. When treated in the same manner as in the above case, a desired polyimide film can be obtained in a shorter time than in the case of thermally dehydrating.

Comparing the thermal imidization method and the chemical imidization method, the chemical method has the advantage that the mechanical strength of the obtained polyimide is large and the linear expansion coefficient is small. . In addition, it is also possible to use the method of thermally imidizing and the method of chemically imidizing together.

Thus, by thermally and / or chemically imidizing the above polyamic acid copolymer, a thermoplastic polyimide copolymer, which serves as the heat resistant adhesive of the present invention, can be obtained.

By the way, the molecular weights of the polyamic acid copolymer and the polyimide copolymer are not particularly limited, but in order to maintain the strength of the polyimide resin produced, a number average molecular weight of 50,000 or more, Further, it is preferably 80,000 or more, particularly preferably 100,000 or more, further preferably 120,000 or more.

By the way, it is often difficult to directly measure the molecular weight of the polyimide polymer. In such a case, an indirect method is used to make a speculative measurement. For example, when a polyimide polymer is synthesized from polyamic acid, the value corresponding to the molecular weight of polyamic acid is the molecular weight of polyimide.

The thermoplastic polyimide copolymer used in the present invention thus obtained has a composition of 100%.
Since it has a clear glass transition point between ℃ and 350 ℃,
The film made of the heat-resistant adhesive according to the present invention can be used as an adhesive layer for other films having no adhesive property.

That is, an adhesive film is formed from such a thermoplastic polyimide copolymer, and the polyimide film serving as the base, the film-like heat-resistant adhesive film according to the present invention, and the copper foil are superposed on each other to form a glass. By laminating at a temperature close to the transition point, the polyimide film and the copper foil can be bonded relatively easily to produce a copper clad laminate.

A polyimide film having an adhesive layer may be prepared by applying a polyamic acid copolymer, which is a precursor of the heat-resistant adhesive according to the present invention, to a polyimide film serving as a base to imidize the polyimide film.

The film made of the heat-resistant adhesive according to the present invention has sufficient mechanical strength, and has a low water absorption rate of about 1% when immersed in pure water at 20 ° C. for 24 hours. Therefore, a flexible printed circuit board or the like can be manufactured based on the film itself made of such a heat-resistant adhesive.

That is, a one-sided flexible printed wiring board can be manufactured by disposing a copper foil or the like on one surface of such a film and a release paper or the like on the other surface and adhering the copper foil or the like on only one surface. Further, a double-sided flexible printed wiring board can be manufactured by arranging and adhering copper foil or the like on both sides of such a film without using an adhesive. Further, such a polyimide film is particularly effective as a substrate such as a multilayer printed wiring board. Further, it may be directly fused to the circuit surface for the purpose of protecting the conductor surface of the flexible printed board and used as a coverlay film.

The heat-resistant adhesive according to the present invention has excellent heat resistance, processability, thermoplasticity, adhesiveness, and low water absorption rate, and in these applications, it is supplied in the state of a polyimide film. It is possible and convenient to handle. Other uses are not particularly limited.

Although the examples of the heat-resistant adhesive and the method for producing the same according to the present invention have been described above, the present invention is not limited to these examples, and the scope of the present invention does not depart from the gist thereof. It can be carried out in a mode in which various improvements, changes and modifications are made based on the knowledge of those skilled in the art.

The present invention will be further described below with reference to examples, but the present invention is not limited to these examples.

Example 1 In a 500 ml three-neck separable flask equipped with a stirrer, 2,2-bis [4- (4-aminophenoxy)] was added.
Phenyl] propane (hereinafter referred to as BAPP) 16.
73.1 g (40 mmol) and 123.1 g of dimethylformamide (hereinafter referred to as DMF) were added, and the atmosphere in the separable flask was agitated while substituting the atmosphere with nitrogen and sufficiently dissolved. Next, make a 50 ml eggplant flask.
1

[Chemical 31] 15.0 g of 2,2-bis (4-hydroxyphenyl) propanedibenzoate-3,3'4,4'-tetracarboxylic acid dianhydride (hereinafter referred to as ESDA) represented by
(26 mmol) and 5- (2,5-dioxotetrahydrofuryl) 3-methyl-3-cyclohexene-1,2.
-Dicarboxylic acid dianhydride (hereinafter referred to as MCDA)
3.2 g (12 mmol) was taken and added as a solid in the BAPP solution. The wall in the eggplant flask is 5g DM
It was washed with F and poured into a separable flask. After leaving it for about 1 hour while stirring, a solution prepared by dissolving 1.2 g of ESDA in 15.9 g of DMF was gradually added to the separable flask while paying attention to the viscosity of the varnish in the separable flask. After reaching the maximum viscosity, E
The addition of the SDA solution was completed, and a polyamic acid solution was obtained.

Film formation was carried out as follows using this polyamic acid solution. First, in a 100 ml volumetric flask, 10.0 g of isoquinoline, 10.0 g of acetic anhydride,
DMF 10.0g was taken and stirred well. Next, this solution was added to 100 g of the obtained polyamic acid solution and well stirred for 2 minutes. After degassing, apply it on PET film, 80 ℃
After peeling off the PET film by heating at 25 ° C for 25 minutes, the end is fixed and the temperature is continuously raised from 100 ° C to 250 ° C. An adhesive was obtained. Furthermore, a copper foil (thickness of 35 μm) is placed on both sides of the obtained heat resistant adhesive, and the temperature is 300 ° C. and 20 kg /
A double-sided copper-clad laminate was obtained by heating and pressing at cm ² for 1 hour.

Regarding the obtained heat-resistant adhesive, glass transition point (° C), peel strength (kg / cm), water absorption rate (%)
I checked. The glass transition point was measured by TMA, and the peel strength was measured using a double-sided copper clad laminate.
It was measured according to IS K6481. Regarding the water absorption rate, the weight change rate after immersion in pure water at 20 ° C. for 24 hours was measured according to ASTM D-570. The results are shown in Table 1.

[0044]

[Table 1]

Example 2 In a 500 ml three-neck separable flask equipped with a stirrer, 16.7 g (40 mmol) of BAPP and DM were added.
120.0 g of F was added, and the atmosphere in the separable flask was stirred while substituting with nitrogen to thoroughly dissolve it. Then 50
12.6 g of ESDA (2
2 mmol), 2.1 g (8 mmol) of MCDA and 2.6 g (8 mm) of 3,3 ', 4,4'-benzophenone tetracarboxylic dianhydride (hereinafter referred to as BTDA).
ol) was taken and added as a solid in the BAPP solution.
The wall surface in the eggplant flask was washed with 5 g of DMF and poured into a separable flask. After leaving it for about 1 hour with stirring, 1.2 g of ESDA was added in advance to DMF1.
The solution dissolved in 5.9 g was gradually charged into the separable flask while paying attention to the viscosity of the varnish in the separable flask. After reaching the maximum viscosity, the addition of the ESDA solution was terminated to obtain a polyamic acid solution.

Using this polyamic acid solution, Example 1
After performing film formation in the same manner as above to obtain a film-shaped heat-resistant adhesive by imidization, further arranging copper foils (35 μm thick) on both surfaces of the obtained heat-resistant adhesive, 300 ° C., 20 kg /
A double-sided copper-clad laminate was obtained by heating and pressing at cm ² for 1 hour.

Regarding the obtained heat-resistant adhesive, Example 1
Measure the glass transition point, peel strength and water absorption in the same manner as
The results are shown in Table 1.

Example 3 Conversion to a 500 ml three-neck separable flask equipped with a stirrer 32

[Chemical 32] 6.3 g (20 mmol) of 1,3-bis- (4-aminobenzyloxy) propane represented by and BAPP
8.4 g (20 mmol) and DMF115.1g were put, and it fully stirred, stirring the atmosphere in a separable flask, substituting nitrogen. Next, in a 50 ml eggplant flask, 15.0 g (26 mmol) of ESDA and M
3.2 g (12 mmol) of CDA was taken and added as a solid in the diamine solution. The wall in the eggplant flask is 5g
It was washed with DMF, and poured into a separable flask. After leaving for 1 hour under stirring, 1.
A solution prepared by dissolving 2 g of ESDA in 15.9 g of DMF was gradually charged into the separable flask while paying attention to the viscosity of the varnish in the separable flask. After reaching the maximum viscosity, the addition of the ESDA solution was terminated to obtain a polyamic acid solution.

Using this polyamic acid solution, Example 1
After performing film formation in the same manner as above to obtain a film-shaped heat-resistant adhesive by imidization, further arranging copper foils (35 μm thick) on both surfaces of the obtained heat-resistant adhesive, 300 ° C., 20 kg /
A double-sided copper-clad laminate was obtained by heating and pressing at cm ² for 1 hour.

Regarding the obtained heat-resistant adhesive, Example 1
Measure the glass transition point, peel strength and water absorption in the same manner as
The results are shown in Table 1.

Comparative Example 1 For comparison, a heat-resistant adhesive made of a thermoplastic polyimide polymer using BTDA and BAPP was prepared. In a 500 ml three-necked separable flask equipped with a stirrer, 16.7 g (40 mmol) of BAPP and DMF1 were added.
05.4 g was added thereto, and the atmosphere in the separable flask was agitated while substituting the atmosphere with nitrogen to sufficiently dissolve it. Next, 12.3 g (38 m) of BTDA was placed in a 50 ml eggplant flask.
mol) was collected and added to the BAPP solution as a solid. The wall surface in the eggplant flask was washed with 5 g of DMF and poured into a separable flask. After standing for about 1 hour with stirring, DM 0.6 g of BTDA in advance.
The solution dissolved in 8.0 g of F was gradually charged into the separable flask while paying attention to the viscosity of the varnish in the separable flask. After reaching the maximum viscosity, the addition of the BTDA solution was terminated to obtain a polyamic acid solution.

Using this polyamic acid solution, Example 1
After performing film formation in the same manner as above to obtain a film-shaped heat-resistant adhesive by imidization, further arranging copper foils (35 μm thick) on both surfaces of the obtained heat-resistant adhesive, 300 ° C., 20 kg /
A double-sided copper-clad laminate was obtained by heating and pressing at cm ² for 1 hour.

Regarding the obtained heat-resistant adhesive, Example 1
Measure the glass transition point, peel strength and water absorption in the same manner as
The results are shown in Table 1.

[0054]

As described above, according to the present invention, by using a thermoplastic polyimide copolymer as a heat resistant adhesive,
Excellent heat resistance, processability, and adhesiveness can be realized, and in particular, an adhesive film with low water absorption can be obtained. Further, the heat-resistant adhesive according to the present invention can be supplied as a polyimide film, and is easy to handle. Furthermore, the heat-resistant adhesive according to the present invention has been confirmed to have radiation resistance that does not cause deterioration or discoloration upon irradiation with radiation, and can be used for equipment that may receive radiation.

Claims (6)

[Claims] 1. A compound represented by the general formula (1): ## STR1 ## with respect to the total amount of all acid dianhydride compounds. (In the formula, Ar ₁ represents a divalent organic group.) A diester acid dianhydride represented by the formula: 50 to 99 mol%, and 1 to 50 of 5- (2,5-dioxotetrahydrofuryl) 3-methyl-3-cyclohexene-1,2-dicarboxylic acid dianhydride (hereinafter referred to as MCDA) represented by
mol% and the general formula (2) other than the diester acid dianhydride represented by the general formula (1) and MCDA. (In the formula, Ar ₂ represents a tetravalent organic group.) 0 to 30 mol% of the acid dianhydride, and a general formula (3) in a substantially equimolar amount to the total acid dianhydride compound. H ₂ N—Ar ₃ —NH ₂ (3) (wherein, Ar ₃ represents a divalent organic group), which is a thermoplastic polyimide copolymer obtained by reacting at least one diamine compound. A heat-resistant adhesive characterized by comprising: 2. Ar ₁ in the general formula (1) is represented by the following formula: The heat-resistant adhesive according to claim 1, which is composed of a thermoplastic polyimide copolymer which is at least one selected from the group of divalent organic groups shown in. 3. Ar ₂ in the general formula (2) is represented by the following formula: At least 1 selected from the group of tetravalent aromatic groups shown in
The heat-resistant adhesive according to claim 1 or 2, which is made of a thermoplastic polyimide copolymer as a seed. 4. Ar ₃ in the general formula (3) is represented by the following chemical formula: At least 1 selected from the group of divalent aromatic groups shown in
The heat-resistant adhesive according to any one of claims 1 to 3, which is composed of a thermoplastic polyimide copolymer as a seed. 5. A compound represented by the general formula (4): embedded image with respect to the total amount of all diamine compounds. (In the formula, Ar ₄ represents a divalent organic group.) A thermoplastic polyimide copolymer obtained by using 1 to 50 mol% of a diesterdiamine compound represented by the formula 1. The heat-resistant adhesive according to claim 4. 6. Ar ₄ in the general formula (4) is represented by the following formula: The heat-resistant adhesive according to any one of claims 1 to 5, which is composed of a thermoplastic polyimide copolymer which is at least one selected from the group of divalent organic groups shown in.