JPH07109438A - Polyimide varnish - Google Patents

Abstract

PURPOSE:To obtain a polyimide varnish which can form a smooth coating film by dissolving a polyimide(precursor) in an organic solvent comprising a specified compound in a specified percentage. CONSTITUTION:A polyimide varnish which is to be applied to a supporting substrate and heat treated to form a polyimide coating film thereon and which is obtained by dissolving a polyimide (precursor) {e.g. a polyimide precursor obtained from 2,2-bis[4-(4-aminophenoxy)phenyl]propane and 1,2,3,4- cyclobutanetetracarboxylic dianhydride} in an organic solvent (e.g. M- methylpyrrolidone), wherein a propylene glycol derivative of the formula (wherein (n) is 1 or 2; and R is H, a 1-4C alkyl, an alkenyl or an alkenoyl) accounts for 5-60wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide varnish, more specifically, a polyimide and / or a polyimide precursor is dissolved in an organic solvent, the solution is applied onto a supporting substrate, and heat treatment is performed. The present invention relates to a polyimide varnish that can be applied to form a smooth polyimide coating film on a supporting substrate.

[0002]

2. Description of the Related Art Polyimide has been widely used as a protective material and an insulating material in the electric and electronic fields because of its high mechanical strength, heat resistance and solvent resistance. Specifically, when used as an insulating film for a semiconductor, a polyimide coating film having a thickness of 1 to 10 μm is formed on a silicon support substrate on which wiring is processed, and when used as a liquid crystal alignment film, a transparent electrode with a transparent electrode is provided. 0.05 ~ on transparent support substrate
Generally, a thin polyimide coating film is formed on various supporting substrates such as a 0.2 μm polyimide coating film to be used. To form such a polyimide coating film, a polyimide varnish obtained by dissolving a polyimide or a polyimide precursor in a suitable organic solvent, spin coating,
It is common to apply a heat treatment on the supporting substrate by a method such as offset printing or gravure printing.

[0003]

When a polyimide coating film is formed on a substrate, the fluidity of the solution after coating is important for forming a smooth film. This is because the unevenness on the surface of the coating film is made smooth by flowing the solution. However, what is currently used as a solvent for polyimide has a large surface tension and its fluidity is not so good. Also,
Japanese Patent Publication No. 4-81167 discloses a method of adding butyl cellosolve in order to reduce the surface tension of a solution, but butyl cellosolve is pointed out to be toxic,
Not very desirable for use.

An object of the present invention is to form a polyimide coating film which is used as an insulating film / protective film for electric / electronic elements or a liquid crystal alignment film by coating a solution of polyimide and / or a polyimide precursor on a substrate. The present invention provides a polyimide varnish capable of forming a smooth polyimide coating film.

[0005]

That is, the present invention is to dissolve a polyimide and / or a polyimide precursor in an organic solvent,
In the polyimide varnish used for forming the polyimide coating film on the supporting substrate by applying the solution on the supporting substrate and applying heat treatment, 5 to 60% by weight of the organic solvent is
General formula [I]

[0006]

[Chemical 2]

(In the formula, n is 1 or 2, R is hydrogen,
It represents a C _1-4 alkyl group, a C _1-4 alkenyl group, or a C _1-4 alkanoyl group. The present invention relates to a polyimide varnish containing a propylene glycol derivative represented by By adding the propylene glycol derivative represented by the general formula [I] of the present invention,
It is possible to apply the polyimide varnish to the supporting substrate uniformly and evenly.

The polyimide and / or polyimide precursor used in the polyimide varnish of the present invention is not particularly limited. Usually, a tetracarboxylic acid derivative and a primary diamine are reacted and polymerized to form a polyimide precursor, and a ring-closing imidation is performed to form a polyimide. Specific examples of the tetracarboxylic acid derivative used for obtaining the polyimide and / or the polyimide precursor of the present invention include pyromellitic acid, 2,3,6,7-naphthalene tetracarboxylic acid, and 1.
2,5,6-naphthalene tetracarboxylic acid, 1,4,5,8-naphthalene tetracarboxylic acid, 2,3,6,7-anthracene tetracarboxylic acid, 1,2,5,6-anthracene tetracarboxylic acid, 3,3
′, 4,4′-Biphenyltetracarboxylic acid, 2,3,3 ′,
4'-biphenyltetracarboxylic acid, bis (3,4-dicarboxyphenyl) ether, 3,3 ', 4,4'-benzophenone tetracarboxylic acid, bis (3,4-dicarboxyphenyl) sulfone, bis (3 , 4-Dicarboxyphenyl) methane, 2,2-bis (3,4-dicarboxyphenyl) propane,
1,1,1,3,3,3-hexafluoro-2,2-bis (3,4-dicarboxyphenyl) propane, bis (3,4-dicarboxyphenyl) dimethylsilane, bis (3,4- Aromatic tetracarboxylic acids such as dicarboxyphenyl) diphenylsilane, 2,3,4,5-pyridinetetracarboxylic acid, and 2,6-bis (3,4-dicarboxyphenyl) pyridine, and their dianhydrides and these Dicarboxylic acid diacid halide, 1,2,3,4-
Cyclobutane tetracarboxylic acid, 1,2,3,4-cyclopentane tetracarboxylic acid, 1,2,4,5-cyclohexane tetracarboxylic acid, 2,3,5-tricarboxycyclopentyl acetic acid,
3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic acid and other alicyclic tetracarboxylic acids and their dianhydrides and their dicarboxylic acid diacid halides, 1,2, Examples thereof include aliphatic tetracarboxylic acids such as 3,4-butanetetracarboxylic acid, dianhydrides thereof, dicarboxylic acid diacid halides thereof, and the like.

Specific examples of the diamine used to obtain the polyimide and / or the polyimide precursor of the present invention include p-phenylenediamine, m-phenylenediamine, 2,5-diaminotoluene and 2,6 -Diaminotoluene, 4,
4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-
Diaminobiphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, diaminodiphenylmethane, diaminodiphenyl ether, 2,2-diaminodiphenylpropane, bis (3,5-diethyl-4-aminophenyl) methane,
Diaminodiphenyl sulfone, diaminobenzophenone, diaminonaphthalene, 1,4-bis (4-aminophenoxy) benzene, 1,4-bis (4-aminophenyl) benzene, 9,10-bis (4-aminophenyl) anthracene, 1 ,
3-bis (4-aminophenoxy) benzene, 4,4′-bis
(4-aminophenoxy) diphenyl sulfone, 2,2-bis
[4- (4-aminophenoxy) phenyl] propane, 2,2-bis (4-aminophenyl) hexafluoropropane, 2,2-
Bis [4- (4-aminophenoxy) phenyl] aromatic diamines such as hexafluoropropane, alicyclic diamines such as bis (4-aminocyclohexyl) methane, bis (4-amino-3-methylcyclohexyl) methane, and tetra Aliphatic diamines such as methylenediamine and hexamethylenediamine, as well as general formula [II]

[0010]

[Chemical 3]

Examples thereof include diaminosiloxane represented by the formula (n represents an integer of 1 to 10). A tetracarboxylic acid derivative and a diamine are reacted and polymerized to obtain a polyimide precursor, and a tetracarboxylic acid dianhydride is generally used as the tetracarboxylic acid derivative used at this time. The molar ratio of tetracarboxylic dianhydride and diamine is preferably 0.8 to 1.2. As in the usual polycondensation reaction, the closer the molar ratio is to 1, the higher the degree of polymerization of the polymer produced.

If the degree of polymerization is too small, the strength of the polyimide coating film is insufficient, and if the degree of polymerization is too large, the workability in forming the polyimide coating film may be deteriorated. Therefore, the degree of polymerization of the product in this reaction is preferably 0.05 to 5.0 dl / g (concentration 0.5 g / dl in N-methylpyrrolidone at a temperature of 30 ° C.) in terms of reduced viscosity of the polyimide precursor solution.

The method of reacting and polymerizing tetracarboxylic dianhydride and diamine is not particularly limited, and generally, N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide and the like are used. A diamine is dissolved in an organic polar solvent, and tetracarboxylic dianhydride is added to the solution and reacted to synthesize a polyimide precursor. The reaction temperature at that time is -20 to 150 ° C, preferably -5.
Any temperature from 1 to 100 ° C can be selected.

In general, polyimide is often insoluble in an organic solvent after imidization. Therefore, a method of dissolving a polyimide precursor in an organic solvent to prepare a varnish, applying this varnish to a supporting substrate, then performing a heat treatment on the substrate for imidization, and forming a polyimide coating film on the supporting substrate is a method. It is common. At this time, the temperature for imidization on the substrate by heating can be any temperature of 100 to 400 ° C.
The range of ~ 350 ° C is preferred.

On the other hand, when the polyimide is dissolved in a solvent, the polyimide precursor is imidized, the obtained polyimide is dissolved in an organic solvent to prepare a varnish, and the varnish is applied to a supporting substrate, and then the substrate is coated. It is also possible to employ a method of forming a polyimide coating film on the supporting substrate by heat treatment to volatilize the solvent. At this time, as a method of imidizing the polyimide precursor, a method of dehydrating and ring-closing by heating in a solution is adopted. The ring-closing temperature due to this heat dehydration is
Any temperature from 100 to 350 ° C, preferably 120 to 250 ° C can be selected.

As another method for converting the polyimide precursor into polyimide, a known dehydration ring-closing catalyst may be used to chemically perform ring closure. The polyimide varnish of the present invention comprises a varnish obtained by dissolving the above-mentioned polyimide and / or polyimide precursor in an organic solvent, and further 5 to 60% by weight of the organic solvent constituting the varnish, preferably 1
0 to 50% by weight must be the propylene glycol derivative represented by the general formula [I].

Specific examples of the propylene glycol derivative include 1-methoxy-2-propanol and 1-ethoxy-2-
Propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate,
Propylene glycol-1-monoethyl ether-2-acetate, dipropylene glycol, 2- (2-methoxypropoxy) propanol, 2- (2-ethoxypropoxy) propanol, 2- (2-butoxypropoxy) propanol, etc. Of these, 1-butoxy-2-propanol and 2- (2-methoxypropoxy) propanol are particularly preferable.

These propylene glycol derivatives are
If the amount of the solvent constituting the polyimide varnish of the present invention is not less than 5% by weight, the effect of smoothing the coating film is not sufficient. Further, since these propylene glycol derivatives usually do not dissolve the polyimide and / or the polyimide precursor by themselves, when the amount exceeds 60% by weight of the total amount of the solvent, precipitation of the polymer occurs and the stability of the varnish decreases. It is not preferable because

Of all the solvents constituting the polyimide varnish of the present invention, the solvent other than the propylene glycol derivative is not particularly limited as long as it dissolves the polyimide and / or the polyimide precursor. As an example
2-pyrrolidone, N-methylpyrrolidone, N, N-dimethylacetamide, N, N-dimethylformamide, dimethylsulfoxide, hexamethylphosphoramide, γ-butyrolactone and the like can be mentioned.

In addition, even a solvent which does not dissolve the polyimide and / or the polyimide precursor by itself may be added to the above solvent as long as the solubility is not impaired. A method of dissolving these polyimides and / or polyimide precursors in the above solvent to form a polyimide varnish is
There is no particular limitation.

For example, the reaction / polymerization solution of the above-mentioned polyimide and / or polyimide precursor may be used as it is, or the produced polyimide and / or polyimide precursor may be added to a large excess of water or a poor solvent such as methanol. It may be used by re-dissolving it in the above solvent after throwing in and collecting the precipitate. The amount of the resin component in the polyimide varnish varies depending on the purpose of use of the varnish and is not particularly limited. For example, it is 2 to 15% by weight in the case of a liquid crystal alignment film and 5 to 3 in the case of an insulating film.
It is 0% by weight.

For the purpose of further improving the adhesion between the finally formed polyimide coating film and the supporting substrate, an additive such as a coupling agent may be added as one of the components of the polyimide varnish of the present invention. It is possible. The polyimide varnish of the present invention is applied on a supporting substrate and subjected to heat treatment to form a polyimide coating film having a uniform film thickness on the supporting substrate, an insulating film of an electric / electronic element, a protective film, and further a liquid crystal. It can be used as an alignment film of a display element.

The coating method at this time is not particularly limited, but spin coating, roll coating, offset printing, gravure printing and the like are common. The heat treatment temperature for forming the polyimide coating film is, if the polyimide varnish is a polyimide precursor solution, a temperature for converting the polyimide precursor into polyimide, and the temperature is from 100 to 350 ° C., preferably from 120. Any temperature of 250 ° C can be selected. Further, when the polyimide varnish is a polyimide solution, the heat treatment temperature should be 80 to 150 ° C., as long as the solvent evaporates.

The supporting substrate for forming the polyimide coating film can be appropriately selected according to the application for which the polyimide coating film is used. For example, in the case of an insulating film for a semiconductor element, a protective film is a silicon substrate on which various wirings are processed,
In the case of a liquid crystal alignment film, glass with a transparent electrode, or
For example, a plastic film.

[0025]

The present invention will be described below with reference to examples.
The present invention is not limited to these. Example 1 2,2-bis [4- (4-aminophenoxy) phenyl] propane (hereinafter abbreviated as BAPP) 41.0 g (0.1 mol), and
1,2,3,4-Cyclobutanetetracarboxylic dianhydride 19.2
g (0.098 mol) was reacted in 340 g of N-methylpyrrolidone (hereinafter abbreviated as NMP) at room temperature for 10 hours to prepare a polyimide precursor solution. The reduced viscosity (ηsp / c) of the obtained polyimide precursor was 1.02 dl / g (0.5 wt% NMP solution, 30
℃).

12 g of this solution was added to 12 g of NMP and 1-butoxy-2.
-By adding 6 g of propanol and making the total resin content 6%, a glass substrate with a transparent electrode was spin-coated at 2000 rpm, dried, and cured to obtain a polyimide coating film with a thickness of about 3000 Å. The obtained coating film was a smooth film without irregularities.

Example 2 41.0 g (0.1 mol) of BAPP and 3,4-dicarboxy-
A polyimide precursor solution was prepared by reacting 1,2,3,4-tetrahydro-1-naphthalene succinic dianhydride (29.9 g, 0.0995 mol) in 400 g of NMP at room temperature for 10 hours. The reduced viscosity (ηsp / c) of the obtained polyimide precursor is 1.14dl / g
(0.5 wt% NMP solution, 30 ° C.).

To 50 g of the obtained polyimide precursor solution, 10.8 g of acetic anhydride and 5.0 g of pyridine as an imidization catalyst were added and reacted at 50 ° C. for 3 hours to prepare a polyimide solution. This solution was put into 500 ml of methanol, and the obtained white precipitate was filtered and dried to obtain a white polyimide powder. The reduced viscosity (ηsp / c) of the obtained polyimide is 1.04.
It was dl / g (0.5 wt% NMP solution, 30 ° C.).

6 g of this powder was dissolved in a mixed solvent of 74 g of γ-butyrolactone and 20 g of 2- (2-methoxypropoxy) propanol to make the total resin content 6%, and flexographically printed on a glass substrate with a transparent electrode and dried. By curing, a polyimide coating film having a thickness of about 1000Å was obtained. The obtained coating film was a smooth film without irregularities.

Example 3 To 12 g of the polyimide precursor solution prepared in Example 1, 3 g of 1-butoxy-2-propanol was added, and a total resin content of 12% was spin-coated at 2000 rpm on a glass substrate with a transparent electrode, followed by dry curing. By doing so, a polyimide coating film having a thickness of about 3 μm was obtained. The obtained coating film was a smooth film without irregularities.

Example 4 NMP was added to 12 g of the polyimide precursor solution prepared in Example 1.
24 g and 1 g of 1-butoxy-2-propanol were added, and a total resin content of 4% was spin-coated on a glass substrate with a transparent electrode at 3500 rpm and dried and cured to obtain a polyimide coating film having a thickness of about 1000 Å. The obtained coating film was a smooth film without irregularities.

Comparative Example 1 NMP was added to 12 g of the polyimide precursor solution prepared in Example 1.
By adding 18 g to make the total resin content 6% and spin-coating on a glass substrate with a transparent electrode at 2000 rpm, and drying and curing, a polyimide coating film with a thickness of about 3000 Å was obtained. The obtained coating film had fine irregularities and cissing on the surface, and a smooth film could not be obtained.

Comparative Example 2 NMP was added to 12 g of the polyimide precursor solution prepared in Example 1.
3 g was added to make the total resin content 12%, and spin coating was performed at 2000 rpm on a glass substrate with a transparent electrode, followed by drying and curing to obtain a polyimide coating film having a thickness of about 3 μ. The obtained coating film had fine irregularities on the surface, and a smooth film could not be obtained.

Comparative Example 3 NMP was added to 12 g of the polyimide precursor solution prepared in Example 1.
33 g was added to make the total resin content 4%, and spin coating was performed on a glass substrate with a transparent electrode at 3500 rpm, followed by drying and curing to obtain a polyimide coating film having a thickness of about 1000Å. The obtained coating film had fine irregularities and cissing on the surface, and a smooth film could not be obtained.

Comparative Example 4 6 g of the polyimide powder obtained in Example 2 was dissolved in 94 g of γ-butyrolactone to make the total resin content 6%, and flexographic printing was performed on a glass substrate with a transparent electrode and drying. The obtained coating film had fine irregularities on the surface, and a smooth film could not be obtained.

[0036]

EFFECT OF THE INVENTION The polyimide varnish of the present invention is used as an insulating film / protective film or liquid crystal alignment film for electric / electronic elements by forming a polyimide coating film by coating and heat treatment on various supporting substrates. Therefore, it is possible to form a smooth coating film having no unevenness.

Claims (7)

[Claims] 1. Used to form a polyimide coating film on a supporting substrate by dissolving a polyimide and / or a polyimide precursor in an organic solvent, coating the solution on the supporting substrate, and subjecting the solution to heat treatment. In the polyimide varnish, 5 to 60% by weight of the organic solvent is represented by the general formula [I] (In the formula, n is 1 or 2, and R represents hydrogen, an alkyl group having 1 to 4 carbon atoms, an alkenyl group, and an alkanoyl group.) A propylene glycol derivative represented by the formula: varnish. 2. The propylene glycol derivative represented by the general formula [I] is 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-
Phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2
-At least one propylene glycol derivative selected from acetate, dipropylene glycol, 2- (2-methoxypropoxy) propanol, 2- (2-ethoxypropoxy) propanol and 2- (2-butoxypropoxy) propanol. Item 1. The polyimide varnish according to Item 1. 3. The propylene glycol derivative represented by the general formula [I] is at least one propylene glycol derivative selected from 1-butoxy-2-propanol and 2- (2-methoxypropoxy) propanol. Of polyimide varnish. 4. The polyimide varnish according to claim 1, which is for forming a liquid crystal alignment film. 5. The resin content in the polyimide varnish is 2 to 15
The polyimide varnish of claim 4, wherein the polyimide varnish is in% by weight. 6. The polyimide varnish according to claim 1, which is for forming an insulating film. 7. The resin content in the polyimide varnish is 5 to 30.
% Of the polyimide varnish of claim 6.