JP2001139808A - Polyimide precursor solution and polyimide film obtained therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide precursor solution which has a low viscosity in spite of containing solutes in a solution at a high solids content and is hard to generate bubbles when a film is formed and do not cause the deterioration of uniformity of the film by bubbles, the occurrence of pinholes and the like, and a polyimide film having excellent surface smoothness irrespective of marks, foreign substances, and irregularities of the substrate surface. SOLUTION: The polyimide precursor solution which is obtained by dissolving 3,4'-oxydianiline and 3,3',4,4'-biphenyltetracarboxylic acid and/or its derivative as the solutes in an organic solvent contains 0.001-5 pts.wt., based on 100 pts.wt. solutes, surfactant composed of a silicone oil. The polyimide film is obtained by coating this polyimide precursor solution on a substrate and heating the coated film to effect imidation and has a thickness of <=10 μm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polyimide precursor solution containing a surfactant composed of silicone oil and a polyimide coating obtained therefrom.

[0002]

2. Description of the Related Art Conventionally, polyimide having excellent electrical insulation and high heat resistance has been used as a surface protective film and an interlayer insulating film of various electronic components such as semiconductor devices. Recently, in an organic electroluminescence display (organic EL display) that emits light by passing a current through a phosphor formed on a glass substrate or a transparent organic film, an anode, an organic EL layer, and a cathode are sequentially laminated on the substrate. In this case, a polyimide thin film is used as an insulating film between the anode and the organic EL layer. Also, polyimide is used as an insulating protective film on a metal substrate applied to a solar cell. Since these organic EL displays and solar cells have a laminated phase structure, the formed polyimide film is required to be a thin film having a thickness of 10 μm or less, having a uniform thickness, and having no pinhole.

As a method for forming these polyimide thin films, there are known a bar coater method, a spray coating method in which a coating liquid is sprayed in the form of a mist, and a spin coating method in which coating is performed by centrifugal force. . However, in the bar coater method or the spin coating method, bubbles are included when handling the polyimide coating solution (polyimide precursor solution), or bubbles are included when the coating solution is dropped on the substrate, and the formation is performed. There are problems that the uniformity of the resulting polyimide coating film is reduced and that pinholes are formed in the coating film. In addition, the spray coating method also has a problem that air bubbles are likely to be contained on the sprayed coating surface.

On the other hand, a polyimide coating solution used when forming a polyimide film is dimethylacetamide or N
-A polyimide precursor solution containing methylpyrrolidone as a solvent and dissolving a polyamic acid, in which the degree of polymerization of the polyamic acid is high and the solid content ratio in the solution is high due to the low solubility in the solvent. Was difficult.
In other words, the conventional polyamic acid is used as a polyimide precursor, and a polyimide precursor coating solution in which this is dissolved as a solute has a high viscosity despite the low solid content concentration because the polyamic acid has a high degree of polymerization. There was an essential problem of being expensive.

Therefore, when a polyimide thin film having a thickness of 10 μm or less and containing no bubbles or pinholes is to be formed from a conventional polyimide precursor solution, a low-concentration, high-viscosity polyimide precursor is diluted to form a thin film. Must be removed. However, if diluted, the solid content concentration will be too low, and as a result, slight scratches and foreign matter on the coated substrate surface will remain on the surface of the coating, and a uniform polyimide coating having surface smoothness cannot be obtained. There was a problem.

[0006]

SUMMARY OF THE INVENTION In view of the above situation, an object of the present invention is to achieve a low viscosity despite the fact that a solvent contains a solute in a high solid content ratio.
When forming a coating, it is difficult to generate bubbles, to provide a polyimide precursor solution that does not generate pinholes or the like by reducing the uniformity of the film due to bubbles, and bubbles and pinholes obtained from this polyimide precursor solution An object of the present invention is to provide a polyimide film having excellent surface smoothness irrespective of scratches, foreign matter, or irregularities on the substrate surface.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies in order to solve the above-mentioned problems, and as a result, dissolved a specific diamine and a specific carboxylic acid and / or a derivative thereof in an organic solvent as a solute. The polyimide precursor solution containing a specific amount of a surfactant composed of silicone oil has a low viscosity even if it has a high solid content ratio, and quickly removes bubbles contained in the applied coating film. The present invention was found to be capable of foaming, and from this solution, it was possible to form a uniform polyimide film having no surface bubbles and no pinholes and having surface smoothness irrespective of scratches, foreign matter, or irregularities on the substrate surface. Reached.

That is, the gist of the present invention is that first, 3,4′-oxydianiline represented by the following structural formula (1) and 3,3 ′, 4,4′- represented by the following general formula (2) A biphenyltetracarboxylic acid and / or a derivative thereof is dissolved in an organic solvent as a solute, and a surfactant made of silicone oil is replaced with a diamine represented by the structural formula (1) and a general formula (2)
(1) A polyimide precursor solution characterized by containing 0.001 to 5 parts by weight with respect to 100 parts by weight of a solute composed of a tetracarboxylic acid and / or a derivative thereof shown in (1).

[0009]

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(Wherein R and R ₁ each represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms)

Second, the polyimide precursor solution is coated on a substrate and is imidized by heating to a thickness of 10 μm.
The following polyimide coatings.

In the polyimide precursor solution, 3,4′-oxydianiline represented by the structural formula (1), 3,3 ′, 4,4′-biphenyltetracarboxylic acid represented by the general formula (2) and And / or the concentration of the solute composed of a derivative thereof is in the range of 30 to 80% by weight and the solution viscosity is 1%.
The polyimide precursor solution of 0 poise or less is a polyimide precursor solution of a preferred embodiment, and this solution is coated on a substrate, and a polyimide film having a thickness of 10 μm or less obtained by heat imidization is a polyimide film of a preferred embodiment. is there.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail. First, terms used in the present invention will be described. (1) Polyimide An organic polymer in which 80 mol% or more of the repeating unit of the polymer chain has an imide structure. And this organic polymer shows heat resistance. (2) Polyimide precursor An organic compound which becomes a polyimide by heating or undergoing a chemical action to close the ring. In the present invention, 3,4′-oxydianiline represented by the structural formula (1) in a polyimide precursor solution And 3,3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof represented by the general formula (2). Here, ring closure means that an imide ring structure is formed.

(3) Polyimide precursor solution The polyimide precursor is dissolved in a solvent. Here, the solvent refers to a compound which is liquid at 25 ° C. (4) Viscosity The rotational viscosity at 20 ° C. was measured using a DVL-BII type digital viscometer (B type viscometer) manufactured by Tokimec Co., Ltd. (5) Solute concentration It is a numerical value expressing the weight ratio of the polyimide precursor in the solution in percentage. (6) Thickness of the polyimide film The thickness of the polyimide film was measured at 10 locations using a Digimatic Micrometer manufactured by Mitutoyo Corporation, and the average value was obtained.

The polyimide precursor solution of the present invention comprises 3,4'-oxydianiline represented by the structural formula (1) and 3,3 ', 4,4'-biphenyltetracarboxylic acid represented by the general formula (2): And / or a derivative thereof dissolved in an organic solvent as a solute and containing a surfactant composed of silicone oil.
(In the formula, R and R ₁ each represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.)

In these polyimide precursor solutions, a part of 3,3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof represented by the general formula (2) is replaced with a carboxylic acid represented by the general formula (3). Alternatively, it may be replaced by a dicarboxylic anhydride represented by the general formula (4). At this time, 3,3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof represented by the general formula (2) is combined with a carboxylic acid represented by the general formula (3) or a dicarboxylic acid represented by the general formula (4) The molar ratio of the anhydride is preferably from 100: 0 to 100: 20,
0: 0 to 100: 11 is more preferred. General formula (2)
The molar ratio of the carboxylic acid represented by the general formula (3) or the dicarboxylic anhydride represented by the general formula (4) to 3,3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof 100 shown in FIG. If it exceeds, a polyimide film having high strength tends not to be obtained.

[0017]

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(Wherein R ₂ represents a divalent aromatic residue containing at least one 6-membered ring in which two carbonyl groups are directly linked to adjacent carbon atoms, and R ₃ is a hydrogen atom, a carbon atom Represents a 1 to 5 alkyl group, and R ₄ represents a divalent aromatic residue containing at least one 6-membered ring in which two carbonyl groups are directly connected to adjacent carbon atoms.)

Further, 3,3 ′,
Part of 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof is 3,3 ′, 4,4 ′ represented by the structural formula (5).
-May be replaced by biphenyltetracarboxylic dianhydride. At this time, 3,3 ′, 4 shown in the general formula (2)
The molar ratio of 4'-biphenyltetracarboxylic acid and / or a derivative thereof to 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride represented by the structural formula (5) is 100: 0 to 0.
A range of 70:30 is preferred. By adjusting this molar ratio, the viscosity of the polyimide precursor solution can be finely adjusted. 3,3 ′, 4,4′- represented by the structural formula (5)
When the amount of biphenyltetracarboxylic dianhydride exceeds 30 mol%, a polyimide precursor solution having a low viscosity, which is a feature of the present invention, tends to be unable to be obtained.

[0020]

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Further, 3,4 ′ shown in the structural formula (1)
Part of oxydianiline may be replaced by a monofunctional amine represented by the general formula (6). In this case, the molar ratio of 3,4′-oxydianiline represented by the structural formula (1) to the amine represented by the general formula (6) is 100: 0 to 100: 2.
The range of 0 is preferable, and 100: 0 to 100: 11 is more preferable. When the amount of the amine represented by the general formula (6) exceeds 20 mol%, a high-strength polyimide film tends not to be obtained.

[0022]

Embedded image

(Wherein R ₅ represents an aromatic residue containing at least one 6-membered ring)

In the polyimide precursor solution, 3,4'-oxydianiline represented by the structural formula (1) and 3,3 ', 4,4'-biphenyltetracarboxylic acid represented by the general formula (2) and / or It is preferable that the concentration of the solute composed of the derivative is in the range of 30 to 80% by weight. If the concentration is lower than 30% by weight, scratches or foreign substances on the surface of the substrate to be coated may remain as irregularities on the surface of the coating. On the other hand, if the concentration is higher than 80% by weight, it may be difficult to stably dissolve the solute depending on the type of the selected solvent, which is not preferable.

The polyimide precursor solution in the present invention comprises:
3,4'-oxydianiline represented by the structural formula (1) and 3,3 ', 4,4'-biphenyltetracarboxylic acid represented by the general formula (2) and / or a derivative thereof are added to a solvent, and silicone oil is added. Can be produced by adding a surfactant consisting of The order of addition may be any order.

The solution viscosity of the polyimide precursor solution of the present invention is preferably 10 poise or less. With 10 poise or more,
It is not preferable to form a coating having a thickness of 10 μm or less because the fluidity of the coating liquid is not sufficient, because thickness unevenness is likely to occur and a coating having a uniform thickness cannot be formed.

The content of the surfactant composed of silicone oil in the polyimide precursor solution is determined by the diamine represented by the structural formula (1) and the tetracarboxylic acid represented by the general formula (2) and / or
Or with respect to 100 parts by weight of a solute composed of a derivative thereof,
It is in the range of 0.001 to 5 parts by weight, preferably 0.0
It is 0.5 to 1 part by weight. When the amount of the surfactant is less than 0.001 part by weight based on 100 parts by weight of the solute, bubbles and pinholes may be generated in the obtained polyimide coating. On the other hand, when the amount of the surfactant exceeds 5 parts by weight. In addition, the film-forming properties may be reduced, cracks and cracks may occur, and a uniform film may not be obtained.

The organic solvent used in the present invention is not particularly limited as long as it dissolves a solute and a surfactant. For example, N-methylpyrrolidone, dimethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylphosphoryltriamide , Sulfolane, N,
Polar solvents containing N, S, P atoms in the molecule such as N'-dimethylimidazolidinone, N-methylcaprolactam, and cellsolves such as cellsolve and phenylcellsolve;
Ethyl acetate cellosolve, butyl acetate cellosolve such as cellosolves, methyl carbitol, carbitols such as ethyl carbitol, ethyl carbitol,
Carbitol acetates such as butyl carbitol acetate, carbitol diethers such as dimethyl carbitol (diglyme) and diethyl carbitol, alcohols such as cyclohexanol and benzyl alcohol, ketones such as cyclohexanone and isophorone, γ-butyrolactone And the like.

Examples of the surfactant comprising a silicone oil used in the present invention include those having a structure represented by the following general formula (7), which is the main structure of the silicone oil. There is no particular limitation as long as it dissolves stably without releasing.

[0030]

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(In the formula, R _{6 to} R ₁₃ each independently represent a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group or a phenyl group, and n represents an integer of 1 to 10.)

The surfactant comprising silicone oil which can be used in the present invention includes, for example, a leveling agent, an antifoaming agent, a foam stabilizer and the like, which are easily available.

The method for applying the polyimide precursor solution of the present invention is not particularly limited, and examples thereof include general methods such as spin coating, spray coating and bar coater. In any of the coating methods, the polyimide precursor solution of the present invention contains a specific amount of a surfactant composed of silicone oil, and has a high concentration and low viscosity. A polyimide film having excellent surface smoothness can be obtained irrespective of scratches, foreign matter, and irregularities. In particular, the polyimide precursor solution of the present invention can be suitably used as a coating solution for a spin coating method in which bubbles or pinholes are likely to be contained in a polyimide film.

After the polyimide precursor solution of the present invention is applied on a substrate, dried and the solvent is removed, a polyimide precursor coating film is obtained and imidized to obtain a polyimide coating film. Also, when the polyimide film is peeled from the substrate,
Alternatively, when the polyimide precursor coating film is peeled off from the substrate and imidized, a polyimide film is obtained. The imidization is performed at 150 ° C. or higher, preferably 200 ° C. or higher, more preferably 250 ° C. or higher, by heating for 10 minutes or longer, preferably 30 minutes or longer.

Further, the polyimide precursor solution of the present invention may contain, if necessary, fillers such as organosilane, pigment, conductive carbon black and metal particles, abrasives, dielectrics, lubricants and the like. Other known additives can be added as long as the effects of the present invention are not impaired. Also, other polymers and, for example, water-insoluble ethers, alcohols,
Solvents such as ketones, esters, halogenated hydrocarbons, and hydrocarbons can be added as long as the effects of the present invention are not impaired.

When the thickness of the polyimide film obtained from the polyimide precursor solution of the present invention is 10 μm or less, it can be used as an interlayer insulating film for a solar cell substrate having a laminated structure, an EL element, a capacitor and the like. Coating obtained from the polyimide precursor solution of the present invention, particularly 10
In a coating having a thickness of μm or less, uniformity of the coating due to bubbles at the time of coating is not impaired, and does not include pinholes.
Alternatively, it has a surface smoothness irrespective of scratches, foreign matter, or irregularities on the substrate surface, and is therefore suitably used as a surface protective film, an interlayer insulating film, and the like. Used in the manufacture of

[0037]

EXAMPLES Hereinafter, the present invention will be described specifically with reference to examples, but the present invention is not limited to these examples.

Example 1 100 g (339.88 mmol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride was dissolved in 228.242 g of N-methylpyrrolidone as a solvent, and then 22.868 g of methanol (22.868 g). 713.748mmo
l) and 1.72 g of triethylamine (16.994 mm
ol) was added. This solution was heated at a temperature of 80 ° C in a hot water bath.
Then, the esterification reaction was carried out for 2 hours with stirring, and the 3,3 ′,
4,4'-biphenyltetracarboxylic acid dimethyl ester was obtained. After cooling the reaction solution to 50 ° C.,
68.04 g of 4'-oxydianiline (339.88 m
mol) was added and stirred and dissolved for 2 hours to obtain a uniform polyimide precursor solution. Further, 0.955 g, which is 0.5% by weight based on the solid content of the obtained polyimide precursor solution, was added to a surfactant SH193 (a silicone foam stabilizer manufactured by Dow Corning Toray Co., Ltd.) composed of silicone oil, Stir and dissolve at 25 ° C until the system is homogeneous,
A polyimide precursor solution (black) was obtained (solid concentration 45
weight%). When the viscosity of this solution was measured, it was 2 poise at 20 ° C. The solution was further rotated at 30 rpm using a spin coater (1H-DX, manufactured by Mikasa Corporation).
After coating on a 4-inch silicon substrate at 00 rpm, and then drying at 80 ° C. for 5 hours in a nitrogen atmosphere, heat imidization was performed at 300 ° C. for 5 hours in a nitrogen atmosphere to give a thickness of 2 μm.
m was obtained. No pinhole in the wafer surface of this polyimide film was observed.

Example 2 A polyimide coating was formed from the polyimide precursor solution obtained in Example 1 in the same manner as in Example 1 except that the coated substrate was a glass substrate having a diameter of 100 mm. In addition,
3D surface roughness measuring device (ET-30 manufactured by Kosaka Laboratory Co., Ltd.)
Center plane average roughness of glass substrate measured in K) (SRa)
Was 50 nm. The thickness of the obtained polyimide film was 2 μm, and no pinhole was observed. The SRa was 1.2 nm, and the polyimide coating obtained from this polyimide precursor solution did not contain pinholes and had excellent surface smoothness.

Example 3 The weight of the solvent, N-methylpyrrolidone, was 190.90.
The reaction was carried out under the same preparation and conditions as in Example 1 except that the amount was changed to 8 g, to obtain a polyimide precursor solution (black) (solid content concentration: 50% by weight). The viscosity of the solution was 7 poise at 20 ° C. Further, this solution was applied on a glass substrate having a diameter of 100 mm (SRa 30 nm) at a rotation speed of 1000 rpm by using a spin coater [1H-DX manufactured by Mikasa Corporation], and then at 80 ° C. for 5 hours in a nitrogen atmosphere. After drying, 5 minutes at 300 ° C under nitrogen atmosphere
Heat imidization was carried out for an hour to obtain a polyimide film having a thickness of 8 μm. No pinhole in the wafer surface of this polyimide film was observed. Further, SRa was 1.0 nm.

Example 4 A surfactant composed of silicone oil was used as BYK-302.
The reaction was carried out under the same preparation and conditions as in Example 1 except that [Big Chemie Japan Co., Ltd.] was used to obtain a polyimide precursor solution (black) (solid content: 45% by weight). When the viscosity of this solution was measured, it was 2 poise at 20 ° C. Further, this solution was used to form a polyimide film on a 4-inch silicon wafer substrate in the same manner and under the same conditions as in Example 1. The thickness of the obtained polyimide film was 2 μm, and no pinhole in the wafer surface was observed.

Example 5 A polyimide precursor solution (black) was prepared by conducting the reaction under the same conditions and conditions as in Example 1 except that the surfactant composed of silicone oil was changed to KP340 (manufactured by Shin-Etsu Chemical Co., Ltd.). (Solid content: 45% by weight). When the viscosity of this solution was measured, it was 2 poise at 20 ° C. Further, this solution was prepared in the same manner and under the same conditions as in Example 1.
A polyimide coating was formed on an inch-silicon wafer substrate. The thickness of the obtained polyimide film was 2 μm, and no pinhole in the wafer surface was observed.

Example 6 A surfactant consisting of silicone oil was used as BYK-333.
The reaction was carried out under the same preparation and conditions as in Example 1 except that (made by Big Chemie Japan Co., Ltd.), to obtain a polyimide precursor solution (black) (solid content concentration: 45% by weight). The viscosity was measured and found to be 2 poise at 20 ° C. Further, this solution was used to form a polyimide coating on a 4-inch silicon wafer substrate in the same manner and under the same conditions as in Example 1. The thickness was 2 μm, and no pinhole in the wafer surface was observed.

Comparative Example 1 A reaction was carried out under the same preparation and conditions as in Example 1 except that the surfactant consisting of silicone oil was not added to obtain a polyimide precursor solution (black) (solid content: 45% by weight). ). When the viscosity of this solution was measured,
Poise. Further, this solution was used to form a polyimide film on a 4-inch silicon wafer substrate in the same manner and under the same conditions as in Example 1. The thickness of the obtained polyimide film was 2 μm, and eight pinholes were observed in the wafer surface.

Comparative Example 2 The reaction was carried out under the same preparation and conditions as in Example 1 except that the amount of the surfactant composed of silicone oil was changed to 7% (13.37 g) with respect to the solid content. A body solution (black) was obtained (solid content: 45% by weight). When the viscosity of this solution was measured, it was 1.2 poise at 20 ° C. Further, this solution was used to form a polyimide film on a 4-inch silicon wafer substrate in the same manner and under the same conditions as in Example 1. Cracks and cracks occurred in the obtained polyimide coating, and a uniform coating could not be obtained.

Comparative Example 3 100 g (339.88 mmol) of 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride was dissolved in 392.093 g of N-methylpyrrolidone as a solvent and kept at room temperature. Next, 68.04 g (339.88 mmol) of 3,4′-oxydianiline was gradually added to the solution over 2 hours, and stirring was further continued for 6 hours.
The solution gelled. (Solid content 30% by weight)

[0047]

As described above, the polyimide precursor solution of the present invention has a low viscosity and a surface active agent composed of silicone oil, despite the fact that the solute is contained in the solvent at a high solid content ratio. Since it contains the agent, bubbles are hardly generated when forming a film, and the uniformity of the film is not reduced by the bubbles, and pinholes are not generated. Further, the polyimide coating of the present invention does not contain bubbles or pinholes, and has excellent surface smoothness regardless of scratches, foreign matter, or irregularities on the substrate surface.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Shigeta 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory F-term (reference) 4J002 CM041 CP032 FD312 GH02 GQ01 4J038 DJ021 DJ031 NA14 NA21 PB09

Claims (3)

[Claims] 1. A 3,4′-oxydianiline represented by the following structural formula (1) and a 3,3 ′, 4 represented by the following general formula (2).
4′-biphenyltetracarboxylic acid and / or a derivative thereof is dissolved in an organic solvent as a solute, and a surfactant composed of silicone oil is replaced with a diamine represented by the structural formula (1) and a tetraol represented by the general formula (2). With respect to 100 parts by weight of a solute composed of a carboxylic acid and / or a derivative thereof, 0.0
A polyimide precursor solution, which is contained in the range of 01 to 5 parts by weight. Embedded image (In the formula, R and R ₁ each represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.) 2. A solute comprising 3,4′-oxydianiline represented by the structural formula (1) and 3,3 ′, 4,4′-biphenyltetracarboxylic acid represented by the general formula (2) and / or a derivative thereof. The polyimide precursor solution according to claim 1, wherein the concentration of the polyimide precursor is in the range of 30 to 80% by weight and the solution viscosity is 10 poise or less. 3. A polyimide film having a thickness of 10 μm or less obtained by applying the polyimide precursor solution according to claim 1 or 2 on a substrate and heating and imidizing the solution.