JPS62280257A - Low-viscosity varnish - Google Patents

Abstract

PURPOSE:To provide a low-viscosity varnish which has a high concn. and gives a lowly expanded resin material by a heat treatment, by mixing two oligomers having specified structures in equal amounts. CONSTITUTION:An oligomer (a) is mixed with an equal amount of another oligomer (b). Said oligomer (a) is one having acid anhydride groups at terminals (a compd. of formula VII), obtd. by reacting an acid anhydride of formula I [wherein Ar is a group of formula II, III or IV; R is a member selected from the group consisting of a fluoroalkyl, a fluoroalkoxy, an acyl and a halogen; lis an integer of 0-2; m is an integer of 0-3; and n is an integer of 0-4] with a diamine of the formula H2N-Ar'-NH2 [wherein Ar' is a group of V or VI; R is a member selected from the group consisting of an alkyl, a fluoroalkyl, an alkoxyl, a fluoroalkoxy, an acyl and a halogen; and n is an integer of 0-4]. Said oligomer (b) is, e.g., a compd. of formula VIII, obtd. by reacting an acid anhydride of formula I with an excess of said diamine.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a highly concentrated, low viscosity varnish having a specific chemical structure and which upon heat treatment provides a low thermal expansion resin material.

[Conventional technology]

Conventional low thermal expansion polyimide is disclosed in Japanese Patent Application Laid-Open No. 60-21242.
As described in Publication No. 8, even though it has an organic structure that provides a polyimide with low thermal expansion, there is no mention of how to provide properties suitable for individual products.

Conventional oligomerization technology is simply aimed at providing a low viscosity varnish, and the purpose is to develop low thermal expansion and
There was no mention of a method for obtaining high-quality films by increasing the molecular weight of oligomers.

[Problem that the invention seeks to solve]

The thermal expansion coefficient (linear expansion coefficient) of most organic polymers is 4X10- even in the temperature range below the glass transition temperature.
At more than 1 in 3, this is a much larger value than metals and inorganic materials. There are many problems caused by the large coefficient of linear expansion of organic materials, and it is no exaggeration to say that these are all the reasons why the use of organic polymers has not progressed as expected. For example, in a flexible printed circuit board (FPC) consisting of a film and a conductor, a film obtained by coating or heat-pressing a flexible film material on a metal foil is desired, but after coating, it is hardened at high temperature, dried, or Since thermocompression bonding is required, there is a problem that curling occurs due to thermal stress caused by a difference in thermal expansion coefficient after cooling to room temperature.

Usually, to prevent this phenomenon from occurring, an adhesive that can be cured at low temperature is used to attach the parts together. However, in the case of FPCs that require heat resistance, adhesives that can be cured at low temperatures generally have poor heat resistance, so even if heat-resistant films such as polymide films are used as the base material, the original heat resistance cannot be developed. . In addition, in the case of coating films, if they are applied onto metal plates or inorganic materials whose coefficient of thermal expansion is much smaller than that of ordinary organic polymers, thermal stress caused by the difference in coefficient of thermal expansion may cause deformation, cracks in the film, or Exposure and destruction of the base material may occur. For example, L
When a coating film is formed on a silicon wafer as a protective film for SI or IC, the wafer may warp, making it impossible to perform photolithography for patterning, or when the resolution becomes extremely poor, or when thermal stress is large. This may destroy the passivation film or cause cleavage damage to the silicon wafer itself.

As described above, there are many problems due to the large coefficient of linear expansion of organic polymers, and organic polymers with low coefficients of expansion have been strongly desired for quite some time.

The present invention is an invention that meets such demands.

This low thermal expansion polyimide has greatly expanded the applications of organic polymers. Furthermore, it is expected that its use in electronic devices will expand dramatically in the future. Promising fields include interlayer insulating films such as LSI multilayer wiring and thin film magnetic heads. The characteristics of the glabella insulating film are mainly due to its ability to flatten the varnished surface, in addition to its ability to match with inorganic substances due to its low thermal expansion. The present invention obtains a low thermal expansion polyimide film with excellent flattening performance on a varnished surface by heat treatment. The company provides a low-viscosity varnish that can be used in electronic materials, primarily interlayer insulation films.

[Means for solving problems]

The flattening performance of a varnish applied on an uneven surface after curing depends on the concentration of the varnish and the melt flow characteristics during curing. That is, the higher the concentration of the varnish, the smaller the shrinkage of the varnish volume during curing;

This is because melt flow can eliminate the level difference caused by volumetric contraction. In a varnish with a structure that provides a low thermal expansion polyimide, the molecular chain is rigid and melt flow properties cannot be expected when it hardens.On the other hand, the concentration of a varnish with a structure that provides a low thermal expansion polyimide that is currently commonly used is based on the weight fraction. According to this idea, the present invention aims to improve the flattening performance by increasing the concentration of the varnish. It is.

However, the relationship between the concentration and viscosity of a concentrated polymer solution is expressed by the equation (1
2) % Formula % (12) It has been proposed that φ is related to the volume fraction of the polymer. In other words, when the concentration of the varnish is increased, its viscosity increases rapidly, resulting in extremely poor working performance, making it virtually impossible to use it as a varnish. The present invention was achieved by solving this problem by reducing the molecular weight of varnish. That is, the formula (1
As proposed in succeeded in obtaining a varnish.

By reacting acid anhydride and diamine while shifting the equivalence ratio, in the case of excess acid anhydride as shown in formulas (2) and (3), oligomers having acid anhydride at both ends, or conversely diamine In the case of excess, oligomers having amino groups at both ends can be obtained. In this case, the degree of polymerization can be freely adjusted by changing the deviation from one point.

At this time, the viscosity of the oligomer also decreases significantly as the degree of polymerization decreases, and it comes to exhibit sufficient workability.

On the other hand, in general, the flexibility and heat resistance of polymers show better values as the molecular weight increases. At this point, the formula (8
), (9) It is difficult to cure the oligomer shown in (9) as it is to obtain a resin that can be used for practical purposes.
It is necessary to increase the molecular weight in some way. This purpose is shown in equations (8) and (9). This can be achieved by mixing equal amounts of oligomers. By mixing, formula (9)
The electron-withdrawing group of the activated anhydride terminal and the formula (8
) reacts to obtain a polyamic acid with a high degree of polymerization. At this time, the time required for increasing the molecular weight is several minutes or more after mixing at room temperature, and most of the work such as varnish application can be completed during this time. Furthermore, in cases where working time is required or when use as a -liquid varnish is desired, oligomers of formula (io), in which the acid anhydride terminal shown in formula (8) is hydrogenated or esterified, may be used. By mixing 11) with the amino-terminated oligomer of formula (9), a low-viscosity varnish that is stable at refrigerator temperature can be obtained. This varnish has a long reaction time at room temperature, providing sufficient working time. To increase the molecular weight of the varnish, after completing one operation, the activated carbonyl carbon is converted into the formula (12
) reaction.

By curing the high molecular weight polyamic acid thus obtained, a polyimide film having excellent unevenness flattening performance and low thermal expansion property can be obtained.

[Effect]

The acid anhydride represented by the formula (1) is in a state where the carbon of the carbonyl group has a large δ-earth property due to the electron-withdrawing group contained in Ar, making it susceptible to a nucleophilic reaction by the nitrogen of the amino group. The same is true for oligomers with anhydride ends. Due to this high reactivity, it is possible to complete the reaction with an oligomer having an amino group terminal and obtain a high molecular weight polyamic acid.

When the terminal of an acid anhydride is hydrogenated or esterified, the δ earth property of carbonyl reversion generally becomes smaller, making the amino group less susceptible to attack by nitrogen, and making it possible to obtain a high molecular weight polyamic acid even by heating. I can't. The present invention solves this problem by imparting high electron-withdrawing properties to Ar and, if necessary, also imparting electron-withdrawing properties to ester groups, increasing the δ-earth property of carbonyl carbon and easily converting it into amino groups by heating. The reaction progresses and it is possible to achieve high molecular weight.

〔Example〕

The varnish was synthesized as follows.

1) Oligomer with acid anhydride end (concentration 30%) 2.3
, 5.6-penzotrifluoridetetocarboxylic acid dianhydride 0.156 moff and 140 g of N-methylpyrroline were placed in a four-hole flask.

After purging the inside of the flask with nitrogen and stirring and dissolving at 30°C, P
-Phenylenediamine (P-PDA) 0.133 mo
(1) was added in small portions over about an hour under stirring.

After the addition of P-phenylenediamine is completed, the reaction is further continued for 2 hours, and then stirred at 80°C for 2 hours to obtain the desired oligomer a. The viscosity of the solution was 28 poise at 25°C.

2) Oligomer with diamine end ('e3 degree 30%) P
- phenylenediamine 0.177 moQ, and 140 g
3. N-methylpyrrolidone was charged into a four-hole flask, the inside of the flask was purged with nitrogen, and the mixture was stirred and dissolved at 30°C.
3',4.4'-Biphenyltetracarboxylic dianhydride (S BPDA) 0.147m.

Q was added in small portions over about an hour. After addition,
The reaction was continued for several hours, and then at 80° C. for several hours to obtain the desired oligomer b. The viscosity of the solution was 12 poise at 25°C.

3) Oligomer with esterified end (f: A degree 3)
2.5%) 5-BPDA O,163moQ and P-P
Using DA O, 136moQ and 140g of NMP, (
In the same manner as in 1), oligomer (C) having an acid anhydride end was added to 1! ). This solution is heated to 80°C, 0.054 mo Q of P-nitrophenol is added under stirring, and the mixture is reacted for 2 hours to obtain the desired oligomer (a').

The viscosity of this solution at 25°C was 3 o poise.

Preparation of polyimide film 1) 113 g of oligo 7 (a) and 100 g of oligomer (b)
After mixing and stirring at room temperature, the mixture was uniformly applied onto a glass substrate using an applicator. The applicator gap was 200μ. Next, this was dried and cured under a nitrogen stream to obtain a film. The coefficient of thermal expansion is 1.53
It was IO-'/deg.

2) 113 g of oligomer (a') and 100 g of oligomer (b)
A film was obtained by changing g in the same manner as in 1.

The coefficient of thermal expansion was 1.31 x 10-5788 g.

〔Effect of the invention〕

Claims (1)

[Claims] 1. When synthesizing varnish, excess acid anhydride having the structure of formula (1) ▲ Numerical formula, chemical formula, table, etc. ▼ (wherein R is a fluorinated alkyl group, fluorinated selected from alkoxyl group, acyl group, halogen, l is an integer of 0 to 2, m is an integer of 0 to 3, n is 0
It is an integer of ~4. ) Formula (5) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ Diamine having the structure (wherein R is an alkyl group, a fluorinated alkyl group, an alkoxyl group, a fluorinated alkoxyl group, an acyl group, a halogen, and n is an integer from 0 to 4). Oligomer (a) with an acid anhydride end and formula (8) ▲Mathematical formulas, chemical formulas, tables, etc. are available▼ React the acid anhydride with the structure of formula (1) and excess diamine with the structure of formula (5) A low viscosity varnish obtained by mixing equal amounts of oligomer (b) obtained by formula (9). 2. In claim 1, a low-carbon compound obtained by using an oligomer (a') having the structure of formula (10) obtained by hydrogenating or esterifying the terminal of the oligomer (a) viscosity varnish. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ 3. In claim 1, oligomers (a) and (b) having the structures of formulas (8) and (9)
Low viscosity varnish using (in the formula, n is 0 to 20, n' is 2 to
A combination of 20 integers, or n is 2 to 20, n' is 0 to 2
combination of integers of 0). 4. In the second claim, a low viscosity varnish obtained using an oligomer (a″) having the structure of formula (11) ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (in the formula, R_1 and R_2 are respectively selected from hydrogen, fluorinated alkyl, ▲numerical formula, chemical formula, table, etc.▼, and R_5 is selected from methyl group, fluorine, and nitro group. O is an integer from 0 to 5). 5. Claim 2 In terms, oligomers (a) and (b) having the structures of formulas (8) and (9)
A low viscosity varnish obtained using
0, a combination of integers from 0 to 20). 6. In the fourth claim, oligomers (b), (
a'') obtained using a low viscosity varnish (in the formula, n is 0 to 2
A combination of integers up to 0 and n' is an integer from 2 to 20,
or n is a combination of an integer from 2 to 20 and an integer from 0 to 20).