JP2003041189A - Varnish and cross-linkable polyimide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a varnish that has at least the following effects (1) through (3): (1) The varnish can be handled in the same way as in the usual polyamidic acid varnish, as the polyamidic acid is straight-chained without crosslinkable site, in other words, can be cast and the crosslinked structure is formed at the same time when the resin is heat-treated to cause imidization; (2) The crosslinked polyimide formed by the heat treatment includes the imide bonds formed by the crosslinking reaction and the decomposition temperature of the resin becomes higher than that in the case where other crosslinking groups are employed; (3) The resultant crosslinked polyimide resin has higher heat resistance and higher chemical resistance than those of the straight-chained polyimide. SOLUTION: The varnish includes a compound represented by chemical formula (1) (wherein n is 3 or 4; Z is a trivalent or tetravalent aromatic group; R1 and R2 are independently from each other H or a monovalent group selected from alkyl or phenyl). The varnish is heat-treated to give the crosslinked polyimide and a method of producing the same is also disclosed.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a varnish and a crosslinked polyimide obtained from the varnish.

The cross-linked polyimide obtained by heat-treating the varnish of the present invention has a higher decomposition temperature than the case of using other cross-linking groups because the bond formed by cross-linking is an imide bond.

Further, due to crosslinking, it has higher heat resistance and chemical resistance than linear polyimide. Furthermore, due to the crosslinking, it is expected to have a high elastic modulus and mechanical strength not only in the temperature range above the glass transition temperature but also near room temperature.

Further, since the varnish of the present invention gives a crosslinked polyimide by heat treatment at a relatively low temperature, the substrate used and the polyimide obtained are less susceptible to deterioration by heat treatment.

[0005]

BACKGROUND OF THE INVENTION Polyimide was developed by DuPont in the United States as a material for the aerospace industry in the 1960s. This polyimide “Kapton” (DuPont) has excellent heat resistance as well as mechanical properties and electrical properties. Due to its high reliability obtained in space industry applications, it can be used in aircraft and industrial equipment. Its applications have expanded, and it is nowadays often used as a heat-resistant insulating material for electricity and electronics, and has become an essential material.

[0006] Above all, as electronics continue to develop astoundingly, high reliability of materials is required with the progress of miniaturization and weight saving of equipment, multifunction and high performance,
The market is expanding centering on applications in the electronic equipment field.

Aromatic polyimide typified by "Kapton" is often used in the form of a film in terms of quantity, and its usage in the world exceeds 1000 tons / year.

[0008] "Kapton" is an organic insulating material having the highest heat resistance, but various problems have come to be pointed out as the applications are expanded and the required characteristics are advanced.

[0009] For example, "Kapton" has a problem that the water absorption is high, the strength and dimensional change due to water absorption are large, the linear expansion is large, and the film warps when laminated with a metal foil.

In order to solve the problems associated with the expansion of applications and the sophistication of required properties, many companies and research institutions have synthesized many polyimides from various diamines and acid anhydrides. Heat resistance, chemical and physical properties have been studied. The latest research and development trends are described in detail in "Latest Trends in Polyimides II" (published by Sumitomo Techno Research Co., Ltd.). When the diamine and the acid anhydride which are the monomers are changed to give various properties to the polyimide, the heat resistance and the chemical resistance, which are the features of the polyimide, are often lowered.

For example, "Upilex" (Ube Industries, Ltd.), which is a high strength and low linear expansion polyimide, is "Kapto".
n ”is known to have lower glass transition temperature and chemical resistance (T.Nakano; 2nd Intern. Conf. on PI. 16
3 to 181 (1985)).

Further, it is known that polyimide having fluorine or silicone introduced therein has low glass transition temperature and chemical resistance.

It is known that the heat resistance and chemical resistance such as the decomposition temperature and the glass transition temperature of the resin can be improved by introducing a crosslinked structure into the resin.

However, since polyimide is generally synthesized through its precursor, polyamic acid, it is difficult to introduce a cross-linking structure.

For example, "Upilex", which is a typical polyimide film, is prepared by preparing a solution of a polyamic acid as a precursor, casting this solution to form a film, and then proceeding with an imidization reaction by heating or the like. By doing so, a polyimide film is manufactured (Yu Mori; The Fiber Society of Japan "FIBE"
R ", 50, 96-101 (1994)). Therefore, when a monomer having a trifunctional or higher functional group is used to introduce a crosslinked structure, it is crosslinked and gelated at the stage of the polyamic acid as a precursor, and is handled as a solution such as casting. I can not do it.

Therefore, the crosslinked polyimide is usually synthesized by introducing a crosslinked structure into the main chain or terminal of the polyimide and crosslinking after molding (Rikio Yokota; “Reinforced Plastics”, Vol. 43, No. 6, 205 to 211). (1999), Volume 43, Issue 9, 3
18-329 (1999), Riki Takeichi; Polymer, 46 (8), 576 (19)
(1997) etc.).

However, most of the many crosslinking methods that have been developed so far are based on an addition reaction, and it is necessary to treat the resin at a higher temperature after imidization in order to crosslink the resin. There were many problems such as coloring and oxidation of the substrate. Further, since the crosslinked structure formed by the addition reaction is a bond containing an aliphatic chain having low heat resistance, it impairs the high decomposition temperature of the polyimide.

From the above, there has been a demand for a polyimide cross-linking method which can be cross-linked under general polyimide production conditions and which can improve heat resistance and chemical resistance of various polyimides.

[0019]

SUMMARY OF THE INVENTION An object of the present invention is to provide a polyimide cross-linking method which can be cross-linked under general polyimide production conditions and which can improve heat resistance and chemical resistance of various polyimides. Is to provide.

[0020]

Means for Solving the Problems As a result of intensive studies to solve the above problems, the present inventors have found that a compound having three or more dicarboxylic acids or dicarboxylic acid monoesters has an amino group at the molecular end. The present invention has been completed by reacting with a certain polyamic acid under ordinary imidization conditions to give a crosslinked polyimide, and that the obtained crosslinked polyimide has a high decomposition temperature because its crosslinked structure is an imide bond.

That is, the present invention provides a varnish comprising a compound represented by the chemical formula (1), a polyamic acid having a molecular terminal of an amino group, and a crosslinked polyimide obtained by heat-treating the varnish. The manufacturing method is related.

[0022]

[Chemical 6]

Since the polyamic acid contained in the varnish of the present invention is a straight chain having no cross-linking site, it can be handled in the same manner as a normal polyamic acid varnish, that is, cast, cast, etc. Since a crosslinked structure is formed at the same time as the imidization by the heat treatment, the crosslinked polyimide can be obtained under the conventionally known production conditions for the linear polyimide.

The cross-linked polyimide obtained by heat-treating the varnish of the present invention has a higher decomposition temperature than the case where other cross-linking groups are used because the bond formed by cross-linking is an imide bond. Further, due to crosslinking, it has higher heat resistance and chemical resistance than linear polyimide. Furthermore, due to the crosslinking, it is expected to have a high elastic modulus and mechanical strength not only in the temperature range above the glass transition temperature but also near room temperature.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention provides a method for cross-linking polyimide which can be cross-linked under general polyimide production conditions and which can improve heat resistance and chemical resistance of various polyimides.

The present invention will be specifically described below.

The present invention provides a varnish comprising a compound represented by the chemical formula (1), a polyamic acid having an amino group at the molecular end, and a crosslinked polyimide obtained by heat-treating the varnish. That is the manufacturing method.

The varnish of the present invention comprises a compound represented by the chemical formula (1) and a polyamic acid having an amino group at the molecular end.

[0029]

[Chemical 7]

In a preferred embodiment, Z in the chemical formula (1) may be a trivalent or tetravalent aromatic group selected from the chemical formula (2).

[0031]

[Chemical 8]

Since the compound represented by the chemical formula (1) does not react with the polyamic acid at room temperature (for example, 0 to 50 ° C.), the varnish does not crosslink.

The compound represented by the chemical formula (1) is dehydrated or dealcoholized under the conditions of applying a varnish, removing a solvent, and imidizing to produce three or more acid anhydride groups. The polymer is cross-linked with each other through the reaction with the amino group of 1, the formation of amic acid and its imidization.

When the compound represented by the chemical formula (8) is used, the compound reacts with the terminal amino group of the polyamic acid at room temperature, the polyamic acid crosslinks, and the varnish gels. , Not preferable.

[0035]

[Chemical 9]

Specific examples of the compound represented by the chemical formula (1) include, for example, 4,4 ', 4 "-(1,3,5-triazine-2,4,6-triyl) tris-1,2. -Benzene dicarboxylic acid, 4,4 ', 4 "-
[1,3,5-benzenetriyltris (carbonylimino)] tris-1,2-benzenedicarboxylic acid, 4,
4 ′, 4 ″-(2,4,6-pyridinetriyl) triphthalic acid and the like can be mentioned.

Further, for example, 1,3-dihydro-1,3
-Dioxo-5-isobenzofurancarboxylic acid ethylidyne tri-4,1-phenylene ester, 1,3-dihydro-1,3-dioxo-5-isobenzofurancarboxylic acid 1,3,5-benzenetriyl ester, 5, 5 ', 5 ", 5'"-
Silane tetrayl tetrakis-1,3-isobenzofurandione, 5,5 ', 5 "-(phenylsilylidine) tris-1,3-isobenzofurandione, 1,3-dihydro-1,3-dioxo-5- Isobenzofurancarboxylic acid 1,2,3-benzenetriyl ester, 5,5 ', 5 "-(1,3,5-triazine-
Examples of the hydrolyzate or ester include 2,4,6-triyl) tris-1,2-isobenzofurandione. These can be used alone or in combination of two or more.

In the present invention, the amount of the compound represented by the chemical formula (1) is the amino group 1 of the polyamic acid used.
0.2-0.5 mol, preferably 0.3-
It is 0.4 mol. When the amount of the compound used is large or small, the resulting polyimide has many uncrosslinked molecular chains, and the effect of improving heat resistance and chemical resistance is small.

In the present invention, the polyamic acid having an amino group at the molecular end is not particularly limited and can be arbitrarily selected from conventionally known polyamic acids.

The polyamic acid of the present invention preferably has a repeating structure represented by the chemical formula (4).

[0041]

[Chemical 10]

In a preferred embodiment of formula (4),
X may be a divalent aromatic group selected from the chemical formula (5).

[0043]

[Chemical 11]

In a preferred embodiment of formula (4),
Y may be a tetravalent aromatic group selected from the chemical formula (7).

The molecular weight of the polyamic acid having an amino group at the molecular end of the present invention is not particularly limited, and can be arbitrarily set according to the viscosity of the varnish, the physical properties of the crosslinked polyimide to be obtained, and the like. In this case, it is preferably in the range of 0.2 to 2.0 dl / g (measured in N, N-dimethylacetamide at a concentration of 0.5 g / dl at 35 ° C.).

When the logarithmic viscosity is less than 0.2, the strength of the polymer is low and the coating film may be broken when the varnish is applied and imidized.

On the other hand, when it is 2.0 or more, the resulting polyamic acid has a very small number of amino groups at the terminals, and there is a possibility that sufficient crosslinking cannot be achieved.

The polyamic acid having an amino group at the molecular end of the present invention can be obtained by using less than an equal amount of tetracarboxylic acid anhydride with respect to the aromatic diamine used. By adjusting the amount, the amount of terminal groups of the polyamic acid obtained, the viscosity of the varnish,
The crosslink density (distance between crosslink points) of the obtained crosslinked polyimide can be controlled.

In the present invention, it is preferable to use 0.8 to 0.99 mol of tetracarboxylic dianhydride per 1 mol of diamine.

When the amount of tetracarboxylic dianhydride used is small, the strength of the obtained polymer is low and the coating film is broken when the varnish is applied or imidized, which is not preferable.

In many cases, the terminal group of the obtained polyamic acid becomes an acid anhydride group, so that sufficient crosslinking cannot be achieved. When 1 mol of diamine and α mol of tetracarboxylic dianhydride are used, the amount of terminal amino groups of the obtained polyamic acid is (1-α) × 2 mol.

The method for producing the polyamic acid is not particularly limited, and it can be obtained from a conventionally known aromatic diamine and an aromatic tetracarboxylic dianhydride by a conventionally known method,
There are no restrictions on the order of charging the raw materials, the concentration of the reaction, the temperature and the time.

The polyamic acid is usually obtained by reacting a diamine and a tetracarboxylic acid dianhydride in an aprotic polar solvent at room temperature to about 60 ° C. for several hours in an inert gas atmosphere. The polyamic acid of the present invention may be one synthesized in a solvent and still dissolved in the solvent, or one precipitated by using a poor solvent to be in a solid state.

Here, as the conventionally known aromatic diamine that can be used, for example, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, 4,
4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, bis (3-aminophenyl) sulfide, bis (4-aminophenyl) sulfide, (3-aminophenyl) (4-amino (Phenyl) sulfide, bis (3-aminophenyl) sulfoxide, bis (4-aminophenyl) sulfoxide, (3-aminophenyl) (4-aminophenyl) sulfoxide, bis (3-aminophenyl) sulfone, bis (4-amino (Phenyl) sulfone, (3-aminophenyl) (4-aminophenyl) sulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 1,3-bis
(3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4 -
Bis (4-aminophenoxy) benzene, 4,4'-bis (3-aminophenoxy) biphenyl, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide, bis [4- (3-aminophenoxy) ) Phenyl] sulfoxide, bis [4- (4-aminophenoxy) phenyl] sulfoxide, bis [4- (3-aminophenoxy) phenyl] sulfone,
Bis [4- (4-aminophenoxy) phenyl] sulfone, bis
[4- (3-aminophenoxy) phenyl] ether, bis [4-
(4-Aminophenoxy) phenyl] ether, 3,3′-diamino-4,4′-diphenoxybenzophenone, 4,4′-diamino-
5,5'-diphenoxybenzophenone, 3,4'-diamino-4,
5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino- 5'-phenoxybenzophenone, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'- Dibiphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,
4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino
-5'-biphenoxybenzophenone, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2-trifluoromethyl-4,4'-diaminodiphenyl ether, 2'-trifluoromethyl-3 , 4'-diaminodiphenyl ether, 2,
2-bis (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-bis (4-aminophenyl) -1,1,1,3,3,3
-Hexafluoropropane, 1,3-bis (3-aminophenoxy) -4-trifluoromethylbenzene, 1,3-bis (3-aminophenoxy) -5-trifluoromethylbenzene, 1,3-bis (3 -Amino-5-trifluoromethylphenoxy) benzene, 1,4-bis (3-amino-5-trifluoromethylphenoxy) benzene, 1,3-bis (3-amino-5-trifluoromethylphenoxy) -5 -Trifluoromethylbenzene, 1,3-bis (3-amino-5-trifluoromethylphenoxy) -4-trifluoromethylbenzene, 1,3-bis (4-amino-2-trifluoromethylphenoxy) benzene, 1,4-bis (4-amino
-2-Trifluoromethylphenoxy) benzene, 2,2-bis
[4- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1 , 3,3,3-hexafluoropropane and the like can be mentioned, and these can be used alone or in combination of two or more kinds.

Here, as the conventionally known aromatic tetracarboxylic dianhydride that can be used, for example, pyromellitic dianhydride and 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride can be used. , 2,3 ', 3,4'-benzophenone tetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,3 ', 3,4'-biphenyltetracarboxylic Acid dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride Anhydrous, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,
Examples thereof include 3,3-hexafluoropropane dianhydride, and these can be used alone or in combination of two or more.

There are no particular restrictions on the reaction solvent that can be used to synthesize the polyamic acid. For example, N, N
-Dimethylformamide, N, N-dimethylacetamide, N, N-diethylacetamide, N-methyl-2-
Pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-methylcaprolactam, hexamethylphosphorotriamide, 1,2-dimethoxyethane, bis (2-methoxyethyl) ether, 1,2-bis (2-methoxy) Ethoxy) ethane, tetrahydrofuran, bis [2-
(2-Methoxyethoxy) ethyl] ether, 1,4-
Examples thereof include dioxane, dimethyl sulfoxide, dimethyl sulfone, diphenyl ether, sulfolane, diphenyl sulfone, tetramethylurea and anisole.
These solvents may be used alone or in combination of two or more.

The varnish of the present invention comprises a compound represented by the chemical formula (1) and a polyamic acid having an amino group at the molecular end, and its production method is not particularly limited,
Usually, it can be obtained by dissolving the compound represented by the chemical formula (1) in the polyamic acid solution obtained by the above-mentioned method for producing polyamic acid. Further, in the above-mentioned solvents, solid polyamic acid and polyamic acid solution,
It can be prepared by dissolving the compound represented by the chemical formula (1).

The concentration of the compound represented by the chemical formula (1) and the polyamic acid contained in the varnish of the present invention is not particularly limited, and can be arbitrarily adjusted depending on the storage stability and the coating property of the varnish. it can.

In addition to the compound represented by the chemical formula (1) and the polyamic acid having an amino group at the molecular end, the varnish of the present invention has a catalyst for promoting imidization, solvent removability and varnish viscosity. Solvent for changing storage stability,
It may contain a coupling material for adjusting the adhesiveness to the base material, and fillers (for example, fiber reinforcing agent, silica, alumina, mica, talc, fine metal particles, etc.) that change the properties of the resulting crosslinked polyimide.

The crosslinked polyimide of the present invention has the chemical formula (1)
The compound represented by is dehydrated or dealcoholized to form three or more acid anhydride groups, which is a crosslinked polyimide formed by reacting with an amino group at the polymer terminal, forming an amic acid and imidizing the same. The crosslinked polyimide of the present invention is
It has a higher glass transition temperature and higher chemical resistance than uncrosslinked linear polyimide. Further, since its crosslinked structure is an imide bond, it exhibits a higher decomposition temperature than crosslinked polyimides obtained by other crosslinking methods.

Further, the cross-linked polyimide of the present invention has higher mechanical strength, sliding, and
Expected to have wear and fatigue properties.

The crosslinked polyimide of the present invention can be obtained by imidizing the varnish of the present invention.

In the present invention, the imidization method is not particularly limited, and a conventionally known chemical or thermal imidization method can be used. As the imidization method,
For example, after varnish applied on a substrate is dried with hot air, it is peeled from the substrate and further heat-treated at a high temperature, heat treated at a high temperature with the substrate still attached, and immersed in a dehydrating agent such as acetic anhydride to chemically And a method of dehydration imidization.

When the varnish of the present invention is thermally imidized to produce a crosslinked polyimide, the usual imidization conditions of the polyamic acid are sufficient, and further high temperature treatment for crosslinking and long time treatment are required. No annealing treatment is required. There is no limitation on the temperature at the time of thermal imidization, but in order to suppress the deterioration of the resulting resin or substrate due to oxidation, etc., 300 ° C
The following is particularly preferable.

Since the polyamic acid contained in the varnish of the present invention is a straight chain having no cross-linking site, it can be handled in the same manner as a normal polyamic acid varnish, that is, cast, cast and the like. Since a crosslinked structure is formed at the same time as the imidization by the heat treatment, the crosslinked polyimide can be obtained under the conventionally known production conditions for the linear polyimide.

The crosslinked polyimide of the present invention is a film, a coating material for electric wires and optical fibers, a coating material for electronics (interlayer insulating film, passivation film, etc.), a circuit board laminated with a metal foil, a base film for magnetic tape, fiber reinforced. It is useful as a matrix resin for composite materials and sliding members.

[0067]

EXAMPLES The present invention will now be described in more detail with reference to examples, but the present invention is not limited to these examples. Each evaluation method in the examples is shown below.

Logarithmic viscosity (ηinh) The logarithmic viscosity (ηinh) is obtained by dissolving a polyamic acid solution in an amount corresponding to a resin amount of 0.5 g in dimethylacetamide.
After making it 00 ml, it measured at 35 degreeC with the Ubbelohde viscometer.

Glass transition temperature (Tg) The glass transition temperature (Tg) was measured by a DSC (differential scanning calorimeter, Shimadzu DSC-60) at a temperature rising rate of 10 ° C./minute from 25 ° C. to 430 ° C. did.

5% weight loss temperature (Td5%) The 5% weight loss temperature (Td5%) was measured in air by TGA (thermogravimetric measuring device, Shimadzu TGA-50).

Light transmittance (T%) The light transmittance (T%) was measured by using UV (ultraviolet-visible absorption spectrophotometer, V-550 manufactured by JASCO Corporation) at 420 nm of a cast film having a thickness of 50 μm. The light transmittance was measured.

Elongation Elongation is TMA (Thermo-mechanical analyzer, Shimadzu TM
A-50) was used to measure the tensile elongation of a strip-shaped film (thickness 50 micrometers, width 5.0 mm, measurement length 15.0 mm) (weight 3.0 g, heating rate 5 ° C./min). . Chemical resistance: 0.5 g of a polyimide film was placed in 100 ml of a mixed solvent of 90% by weight of p-chlorophenol / 10% by weight of phenol, and the mixture was heated and stirred at 180 ° C. for 10 minutes, and the presence or absence of dissolution was visually observed.

[0073]

[Synthesis Example 1] A tris acid anhydride represented by the chemical formula (9) was synthesized according to JP-A-5-112551. This is 6
It was dissolved in methanol at 0 ° C, and methanol was distilled off under reduced pressure at 30 ° C using an evaporator to obtain a white solid tris-anhydride triester compound represented by the chemical formula (10). The obtained triester of tris-anhydride is NMR
Was confirmed to have 3 methyl ester groups.

[0074]

[Chemical 12]

[0075]

Example 1 A flask equipped with a stirrer, a nitrogen introducing tube, and a thermometer was charged with 100 mmol of 4,4′-bis (3-aminophenoxy) biphenyl and 248.2 g of N, N-dimethylacetamide and charged with nitrogen. It was dissolved by stirring for 30 minutes in the atmosphere. Thereafter, 98 mmol of bis (3,4-dicarboxyphenyl) ether dianhydride was added in portions while paying attention to the increase in solution temperature, and the mixture was stirred at room temperature for 6 hours to obtain a polyamic acid solution having a polyamic acid concentration of 20% by weight. It was Ηinh of the obtained polyamic acid was 0.78 dl / g. 50 g of the obtained polyamic acid solution (equivalent to 10.0 g of polyamic acid and 0.645 mmol of amino group at the molecular end) and Synthesis Example 1 were placed in a flask equipped with a stirrer and a nitrogen introducing tube.
Tris-anhydride triester product obtained in step 0.215
Then, mmol was charged and dissolved by stirring for 2 hours under a nitrogen atmosphere to obtain a varnish of the present invention. Ηinh of the polyamic acid in the obtained varnish was 0.78 dl / g. A part of the obtained varnish was cast on a glass plate and heated to a curing temperature of 250 ° C. for 4 hours under a nitrogen stream to desolvate and imidize the varnish. The obtained polyimide film was peeled from the glass plate, and Tg (glass transition temperature), T
d5% (5% weight loss temperature), T% (light transmittance at 420 nm, TMA (tensile elongation measurement), and chemical resistance were evaluated. The results are shown in Table 1 and FIG. It can be seen that the obtained polyimide film does not extend even at a temperature of Tg or higher and is sufficiently crosslinked.

[0076]

[Examples 2 and 3] A polyimide film was obtained in the same manner as in Example 1 except that the curing temperature was 300 ° C and 350 ° C. The evaluation results are shown in Table 1.

[0077]

Comparative Example 1 A part of the polyamic acid solution obtained in Example 1 was cast on a glass plate without adding tris anhydride anhydride triester, and the temperature was raised to 250 ° C. for 4 hours under a nitrogen stream. Then, the temperature was raised and the varnish was desolvated and imidized. Table 1 shows each evaluation result of the obtained polyimide film.
And shown in FIG. From the measurement results of TMA, it can be seen that the obtained polyimide film remarkably stretched at Tg or higher and did not retain its shape.

[0078]

Comparative Example 2 Polyamic acid solution 50 obtained in Example 1
g (polyamic acid 10.0 g, molecular terminal amino group 0.6
(Corresponding to 45 mmol) and 0.323 mmol of pyromellitic acid dimethyl ester were charged and dissolved in a nitrogen atmosphere with stirring for 2 hours to obtain a varnish. Ηinh of the polyamic acid in the obtained varnish was 0.80 dl / g. A polyimide film was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1 and FIG.

[0079]

Comparative Example 3 Polyamic acid solution 50 obtained in Example 1
g (polyamic acid 10.0 g, molecular terminal amino group 0.6
45 mmol) and maleic anhydride 0.645 m
mol and charged under nitrogen atmosphere for 2 hours to dissolve,
I got a varnish. Ηin of polyamic acid in the obtained varnish
h was 0.78 dl / g. A polyimide film was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1 and FIG.

[0080]

[Comparative Examples 4 and 5] A polyimide film was obtained in the same manner as in Comparative Example 3 except that the curing temperature was 300 ° C and 350 ° C. The evaluation results are shown in Table 1 and FIG.

[0081]

Comparative Example 6 Polyamic acid solution 50 obtained in Example 1
g (polyamic acid 10.0 g, molecular terminal amino group 0.6
45 mmol) and 0.215 mmol of tris-anhydride represented by the formula (Formula 9) obtained in Synthesis Example 1 and stirred under a nitrogen atmosphere. I can no longer. It seems that the polyamic acid was crosslinked, and the reaction mass was gelled in a jelly form.

[0082]

Example 4 4,4′-bis (3-aminophenoxy)
Using 100 mmol of biphenyl, 244.4 g of N, N-dimethylacetamide and 95 mmol of bis (3,4-dicarboxyphenyl) ether dianhydride, a polyamic acid solution having a polyamic acid concentration of 20% by weight was prepared in the same manner as in Example 1. Got Ηinh of the obtained polyamic acid was 0.40 dl / g. The same procedure as in Example 1 was performed using 50 g of the obtained polyamic acid solution (equivalent to 10.0 g of polyamic acid and 1.636 mmol of the terminal amino group in the molecule) and 0.545 mmol of the tris-anhydride triester compound obtained in Synthesis Example 1. Then, the varnish of the present invention was obtained.
Ηinh of polyamic acid in the obtained varnish is 0.41d
It was 1 / g. A polyimide film was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1 and FIG.

[0083]

Example 5 4,4′-bis (3-aminophenoxy)
Using 100 mmol of biphenyl, 244.4 g of N, N-dimethylacetamide and 90 mmol of bis (3,4-dicarboxyphenyl) ether dianhydride, a polyamic acid solution having a polyamic acid concentration of 25% by weight was prepared in the same manner as in Example 1. Got Ηinh of the obtained polyamic acid was 0.29 dl / g. The same procedure as in Example 1 was carried out using 40 g of the obtained polyamic acid solution (10.0 g of polyamic acid and 3.358 mmol of a molecular terminal amino group) and 1.119 mmol of the tris-anhydride triester compound obtained in Synthesis Example 1. Then, the varnish of the present invention was obtained.
Ηinh of polyamic acid in the obtained varnish is 0.29d
It was 1 / g. A polyimide film was obtained in the same manner as in Example 1. The evaluation results are shown in Table 1.

[0084]

[Table 1]

[0085]

INDUSTRIAL APPLICABILITY Since the varnish of the present invention contains the polyamic acid having a straight chain having no cross-linking site, it can be handled in the same manner as ordinary polyamic acid varnish, that is, cast, cast, etc. Since a crosslinked structure is formed simultaneously with imidization by ordinary heat treatment, a crosslinked polyimide can be obtained under the conventionally known production conditions for a linear polyimide.

The cross-linked polyimide obtained by heat-treating the varnish of the present invention has a higher decomposition temperature than the case where other cross-linking groups are used because the bond formed by cross-linking is an imide bond. Further, due to crosslinking, it has higher heat resistance and chemical resistance than linear polyimide.

[Brief description of drawings]

[Figure 1] Tensile elongation measurement results of polyimide film

Continued front page    F-term (reference) 4J038 DJ031 KA06 NA04 NA11                       NA14 PB09 PC02 PC08                 4J043 PA15 QB15 QB21 RA34 RA36                       RA37 SA06 SA47 SA61 SA62                       SB01 TA15 TA17 TA33 TA71                       TB01 UA131 UA141 UA151                       UA152 UA161 UA162 UA171                       UA172 UA182 UA332 UA362                       UA392 UB011 UB051 UB121                       UB151 UB161 UB221 UB281                       UB301 UB401 ZA11 ZA12                       ZA23 ZA31 ZA34 ZA51 ZA52                       ZB03

Claims (7)

[Claims] 1. A varnish comprising a compound represented by the chemical formula (1) and a polyamic acid having a molecular terminal of an amino group. [Chemical 1] 2. The varnish according to claim 1, wherein Z is a trivalent or tetravalent aromatic group selected from the chemical formula (2). [Chemical 2] 3. The varnish according to claim 1, wherein the polyamic acid is a polyamic acid having a repeating structure represented by the chemical formula (4). [Chemical 3] 4. The varnish according to any one of claims 1 to 3, wherein X is a divalent aromatic group selected from the chemical formula (5). [Chemical 4] 5. The varnish according to any one of claims 1 to 4, wherein Y is a tetravalent aromatic group selected from the chemical formula (Formula 7). [Chemical 5] 6. A cross-linked polyimide obtained by imidizing the varnish according to any one of claims 1 to 5. 7. The method for producing a crosslinked polyimide according to claim 6, wherein the imidization method is a heat treatment, and the heat treatment temperature is 300 ° C. to 150 ° C.