JP2001302913A - Polyimide precursor solution and polyamide coating film obtainable therefrom - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide precursor solution which has a low viscosity even when it contains the solute of a polyimide precursor in a solvent at a high solids content ratio and does not cause cissing of a coating liquid against a substrate upon coating and is difficult to be affected by the state of the substrate surface, and a polyimide coating film having no pinhole at a thickness of <=10 μm and excellent surface smoothness. SOLUTION: This polyimide precursor solution comprises a salt composed of 3,4'-oxydianiline and 3,3',4,4'-biphenyltetracarboxylic acid and/or its derivative and 4,4'-oxydiphthalic acid and/or its derivative which is dissolved as the solute in an organic solvent with a molar ratio of the tetracarboxylic acid and/or its derivative of 0:100 to 90:10, and 0.001-5 pts. mass, based on 100 pts. mass salt as the solute, surface active agent containing a siloxane unit. The polyamide coating film has a thickness of <=10 μm which can be obtained by coating this solution on a substrate and imidating the coated film.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a polyimide precursor solution containing a surfactant containing a siloxane unit, and a polyimide coating obtained therefrom.

[0002]

2. Description of the Related Art Hitherto, polyimide having excellent electrical insulation and high heat resistance has been widely used as a surface protective film and an interlayer insulating film of various electronic components such as semiconductor devices. 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. However, a polyimide thin film is used as an insulating film between the anode and the organic EL layer. Furthermore, polyimide is also 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 applied polyimide film is required to have a thickness of 10 μm or less, excellent surface smoothness and no pinholes.

As a method for forming a polyimide film, a bar coater method, a spray coating method in which a coating liquid is sprayed in a mist form onto a substrate, and a spin coating method in which coating is performed by centrifugal force are known. Among them, the spin coating method is suitably used for forming a thin film having a thickness of 10 μm or less. The viscosity of the coating liquid used in the spin coating method needs to be 10 poise or less at 20 ° C., but when the viscosity of the coating liquid is low, repelling occurs on the substrate of the coated liquid during coating, There was a problem that a pinhole was formed on the coating and minute irregularities were formed on the surface.

On the other hand, a polyimide coating solution used when forming a polyimide film is dimethylacetamide or N
-Is a polyimide precursor solution using methylpyrrolidone as a solvent and a polyamic acid as a solute, in which case the degree of polymerization of the polyamic acid is high, and the solid content in the solution is increased due to the low solubility in the solvent. It was difficult. In other words, a conventional polyimide precursor solution using a polyamic acid as a polyimide precursor has a fundamental problem that the viscosity is high because the polyamic acid has a high degree of polymerization, despite the low solid content concentration. there were. When applying a polyimide precursor solution using this polyamic acid as a polyimide precursor by spin coating,
It was necessary to extremely reduce the solid content concentration. Therefore, the polyimide thin film obtained from the conventional polyimide coating solution has a low solid content concentration, so that slight scratches, foreign substances, and traces of irregularities on the surface of the coated substrate remain on the coating surface. There was a problem of poor sex.

As described above, conventionally, when a polyimide coating having a thickness of 10 μm or less is to be obtained, a polyimide coating liquid having a low viscosity is used, and a coating liquid having a low viscosity is applied to a substrate. Coating will cause cissing on the board,
Further, as a result, there is a problem that a pinhole is generated in the obtained polyimide film. Further, when the solid content concentration of the polyimide coating solution is low, there is also a problem that the state of the substrate surface is easily affected, and the surface smoothness of the obtained polyimide film is low.

[0006]

SUMMARY OF THE INVENTION In view of such circumstances, a first object of the present invention is to provide a polyimide precursor which is a solute in a solvent at a high solid content ratio and have a low viscosity. A second object of the present invention is to provide a polyimide precursor solution which does not cause cissing of the liquid applied at the time of processing on the substrate and is not affected by the state of the substrate surface.
An object of the present invention is to provide a polyimide film having no pinholes and excellent in surface smoothness with high productivity.

[0007]

Means for Solving the Problems The present inventors have conducted intensive studies to solve the above-mentioned problems, and as a result, a salt comprising a specific diamine and a carboxylic acid and / or a derivative thereof has been dissolved in an organic solvent. Is dissolved as, and a polyimide precursor solution containing a surfactant having a specific structural unit,
It has been found that even if it has a high solid content ratio, it has a low viscosity, has no cissing of the coated liquid on the substrate, and is hardly influenced by the state of the substrate surface such as scratches, irregularities, and foreign matter on the substrate surface. Then, it was found that the polyimide film obtained from this solution did not generate pinholes and had surface smoothness, and the present invention was reached.

That is, the gist of the present invention is to firstly disclose 3,4'-oxydianiline represented by the following formula (1) and 3,3 ', 4,4'-biphenyltetrane represented by the following formula (2) A salt comprising a carboxylic acid and / or a derivative thereof and 4,4′-oxydiphthalic acid and / or a derivative thereof represented by the following formula (3) is dissolved in an organic solvent as a solute;
The molar ratio of 3,3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof represented by the formula (2) to 4,4′-oxydiphthalic acid and / or a derivative thereof represented by the formula (3) is as follows. 0: 100 to 90:10, and 0.001 to 5 parts by mass of a surfactant containing a siloxane unit represented by the following formula (4) based on 100 parts by mass of a salt as a solute. Is a polyimide precursor solution.

[0009]

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Wherein R, R ₁ , R ₂ , and R ₃ are each independently selected from a hydrogen atom and an alkyl group having 1 to 5 carbon atoms, and R ₄ and R ₅ are each independently a hydrogen atom and 1 carbon atom. ~
5 selected from an alkyl group, an alkoxy group and a phenyl group. Second, the polyimide precursor solution is characterized in that the concentration of the salt as a solute in the polyimide precursor solution is 30 to 80% by mass and the solution viscosity is 10 poise or less. Third, a polyimide precursor solution is coated on a substrate, and the thickness obtained by heating and imidization is 10 μm.
m or less.

[0011]

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 that becomes a polyimide by ring closure by heating or chemical action. 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 mass 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. (7) Surface smoothness Three-dimensional surface roughness measuring device (ET-30 manufactured by Kosaka Laboratory Co., Ltd.)
K, stylus measurement), the center plane average roughness (SRa) of the substrate surface or the surface of the polyimide film formed on the substrate was measured, and the smoothness of the substrate surface or the surface of the polyimide film was evaluated from the numerical value. .

Further, the present invention will be described. In the polyimide precursor solution of the present invention, the solute salt is 3,4′-oxydianiline represented by the formula (1) and a salt represented by the formula (2)
3,3 ', 4,4'-biphenyltetracarboxylic acid and / or a derivative thereof shown in Formula (3) and 4,3'
4'-oxydiphthalic acid and / or a derivative thereof [in the formulas (2) and (3), R, R ₁ , R ₂ ,
R ₃ is independently selected from a hydrogen atom and an alkyl group having 1 to 5 carbon atoms. ]. Then, 3 shown in equation (2)
The molar ratio of 3 ′, 4,4′-biphenyltetracarboxylic acid and / or a derivative thereof to 4,4′-oxydiphthalic acid and / or a derivative thereof represented by the formula (3) is 0: 100 to
90:10 is preferred. When the molar ratio of 4,4′-oxydiphthalic acid and / or a derivative thereof represented by the formula (3) is less than 10, the adhesion of the obtained polyimide film to the substrate decreases, and the film peels from the substrate. There are cases.

In the polyimide precursor solution of the present invention, tetracarboxylic acids represented by the formulas (2) and (3) and / or
Alternatively, part of the derivative thereof may be replaced with a carboxylic acid represented by the general formula (5) or a dicarboxylic anhydride represented by the general formula (6). At this time, the sum of the number of moles of the tetracarboxylic acid and / or the derivative thereof represented by the formulas (2) and (3) and the carboxylic acid represented by the general formula (5) or the dicarboxylic anhydride represented by the general formula (6) Is a molar ratio of 100: 0 to 100: 2
0 is preferable, and 100: 0 to 100: 11 is more preferable. The molar ratio of the carboxylic acid represented by the general formula (5) or the dicarboxylic anhydride represented by the general formula (6) to the sum of 100 moles of the tetracarboxylic acid and / or the derivative thereof represented by the formulas (2) and (3) is 20. When it exceeds, only a polyimide film having low strength may be obtained.

[0015]

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Wherein R ₆ 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 ₇ is a hydrogen atom or a carbon atom; Represents an alkyl group of 1 to 5, and R ₈ 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, a part of the tetracarboxylic acid represented by the formulas (2) and (3) and / or a derivative thereof is converted to 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride represented by the formula (7). And / or 4,4′-oxydiphthalic dianhydride shown in formula (8). At this time, the sum of the number of moles of the tetracarboxylic acid and / or its derivative shown in the formulas (2) and (3) and the sum of the number of moles of the tetracarboxylic dianhydride shown in the formulas (7) and (8) The molar ratio is 10
0: 0 to 70:30 is preferred. By adjusting this molar ratio, the viscosity of the polyimide precursor solution can be finely adjusted. If the sum of the number of moles of the tetracarboxylic dianhydride represented by the formulas (7) and (8) exceeds 30 mol%, a low-viscosity polyimide precursor solution which is a feature of the present invention may not be obtained.

[0018]

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Furthermore, a part of the 3,4′-oxydianiline represented by the formula (1) may be replaced with a monofunctional amine represented by the formula (9). In this case, the molar ratio of the amine represented by the general formula (9) to the 3,4′-oxydianiline represented by the formula (1) is preferably 100: 0 to 100: 20, and 100: 0 to 100: 11. Is more preferred. When the amine represented by the general formula (9) exceeds 20 mol%, only a polyimide film having low strength may be obtained. Wherein R ₉ represents an aromatic residue containing at least one 6-membered ring. ]

[0020]

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The polyimide precursor solution of the present invention comprises a surfactant containing a siloxane unit represented by the formula (4) with respect to 100 parts by mass of a solute salt [wherein R ₄ and R ₅ are each independently It is selected from a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group and a phenyl group. Is 0.00
1 to 5 parts by mass, preferably 0.001 to 1 part by mass. When the content of the surfactant is less than 0.001 part by mass, when the polyimide precursor solution is applied to the substrate, repelling of the applied liquid to the substrate may occur.
On the other hand, when the amount of the surfactant exceeds 5 parts by mass, the film-forming property is reduced, cracks and cracks are generated, and a uniform film may not be obtained.

The polyimide precursor solution of the present invention contains a surfactant containing a siloxane unit in the above-described ratio, so that a glass substrate, a ceramic substrate, an organic material substrate such as polyimide, aluminum, copper, gold, Repelling of the liquid applied to a metal substrate such as silver or nickel does not occur.

Examples of the surfactant containing a siloxane unit that can be used in the present invention include easily available leveling agents, defoamers, foam stabilizers, and the like. Specifically, polyether-modified dimethylpolysiloxane, polyether Examples include ether-modified methylalkylpolysiloxane, polyester-modified dimethylpolysiloxane, polyester-modified methylalkylpolysiloxane, and aralkyl-modified methylpolysiloxane.

The concentration of the polyimide precursor in the polyimide precursor solution of the present invention is preferably 30 to 80% by mass. More preferably, it is 40 to 80% by mass.
If the concentration is lower than 30% by mass, scratches, foreign matter, and irregularities on the surface of the substrate to be coated may remain as irregularities on the coating surface. On the other hand, if the concentration is higher than 80% by mass, it may be difficult to stably dissolve the polyimide precursor depending on the type of the selected solvent, which is not preferable.

The solution viscosity of the polyimide precursor solution of the present invention is preferably 10 poise or less. With 10 poise or more,
When the fluidity of the coating liquid is not sufficient, especially when a film having a thickness of 10 μm or less is produced by a spin coating method,
It is not preferable because thickness unevenness easily occurs and a film having a uniform thickness cannot be produced.

The polyimide precursor solution in the present invention comprises:
3,4′-oxydianiline represented by formula (1) and formula (2)
3,3 ', 4,4'-biphenyltetracarboxylic acid and / or a derivative thereof shown in Formula (3) and 4,3'
It can be produced by sequentially adding 4'-oxydiphthalic acid and / or a derivative thereof to an organic solvent.
The order of addition may be any order.

The organic solvent used in the present invention is not particularly limited as long as it can dissolve the solute polyimide precursor and the surfactant. For example, N-methylpyrrolidone,
N, S, N, S, and N are contained in molecules such as dimethylformamide, dimethylacetamide, dimethylsulfoxide, hexamethylphosphoryltriamide, sulfolane, N, N'-dimethylimidazolidinone, and N-methylcaprolactam.
Polar solvents containing P atoms, cellosolves such as cellosolve, phenyl cellosolve, cellosolves such as ethyl acetate cellosolve, butyl acetate cellosolve, carbitols such as methyl carbitol and ethyl carbitol, ethyl carbitol acetate, 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.

As a coating method for obtaining a polyimide film from the polyimide precursor solution of the present invention, a usual method is adopted, for example, a method such as a spin coating method, a spray coating method and a bar coater method. Is 10 μm
When a thin film having the following excellent surface smoothness is produced, a spin coating method is suitably used. Even in coating methods other than the spin coating method, when the polyimide precursor solution of the present invention is used, a polyimide film having excellent surface smoothness, compared to the case of producing a polyimide film using a conventional polyimide precursor solution Can be obtained.

The polyimide film is obtained by applying a polyimide precursor solution onto a substrate or a substrate, drying the solvent and removing the solvent, obtaining a polyimide precursor film, and imidizing the film to obtain a polyimide film. In addition, peel from the substrate,
Alternatively, a polyimide film is obtained by peeling the coating film of the polyimide precursor from the substrate and imidating the same. In the present invention, the polyimide film falls under the category of polyimide coating. The imidization is performed at 150 ° C. or higher, preferably 2
The heating is performed at a temperature of 00 ° C. or higher, more preferably 250 ° C. or higher, for 10 minutes or longer, preferably 30 minutes or longer.

Further, if necessary, the polyimide precursor solution of the present invention may contain other known additives such as fillers such as pigments, conductive carbon black and metal particles, abrasives, dielectrics and lubricants. Additives can be added as long as the effects of the present invention are not impaired. In addition, other polymers and solvents such as water-insoluble ethers, alcohols, ketones, esters, halogenated hydrocarbons, hydrocarbons and the like can be added within a range not to impair the effects of the present invention.

The polyimide coating obtained from the polyimide precursor solution of the present invention, particularly the polyimide coating having a thickness of 10 μm or less, does not contain pinholes and has excellent surface smoothness irrespective of scratches, foreign matter, or irregularities on the substrate surface. Therefore, it is suitably used as a surface protective film, an interlayer insulating film, and the like, and is used for, for example, a solar cell substrate, an EL element substrate, a heat-resistant insulating element, a capacitor and the like. The polyimide precursor solution of the present invention can also be used for producing these products.

[0032]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to embodiments. Example 1 4,4 ′ was added to 500 g of N-methylpyrrolidone as a solvent.
-270.0 g of oxydiphthalic acid (ODPA) (0.8
7 mol) and then 83.56 g of methanol
(2.61 mol) and 4.18 g of triethylamine were added. This solution was stirred in a hot water bath at an internal temperature of 80 ° C. for 2 hours.
The esterification reaction was carried out over a period of time to obtain a solution containing 4,4'-oxydiphthalic acid dimethyl ester. After the reaction solution was cooled to 50 ° C., 174.29 g (0.87 mol) of 3,4′-oxydianiline was added, and the mixture was stirred and dissolved for 2 hours to obtain a uniform polyimide precursor solution. Furthermore, a surfactant BYK-302 containing a siloxane unit.
(Polyether modified dimethylpolysiloxane manufactured by Big Chemie Japan KK) is 0.5% by mass based on the solid content of the obtained polyimide precursor solution.
5 g was added, and the mixture was stirred and dissolved at 25 ° C. until the system became uniform to obtain a polyimide precursor solution (black) (solid content concentration: 50% by mass). When the viscosity of this solution was measured,
It was 1.8 poise at 0 ° C. Further, this solution was applied on an 8-inch silicon wafer substrate at 4,000 rpm for 30 seconds using a spin coater (1H-DX, manufactured by Mikasa Corporation). At this time, no repelling of the applied liquid to the substrate occurred. Thereafter, the applied liquid was dried at 80 ° C. for 5 hours in a nitrogen atmosphere, and then heated and imidized at 300 ° C. for 5 hours in a nitrogen atmosphere to obtain a polyimide film having a thickness of 2 μm. No pinholes were observed in the polyimide coating.

Further, the solution was subjected to a center plane average roughness (SR
Aluminum substrate with a) of 50 nm (diameter 100 mm)
Was similarly spin-coated and thermally imidized to obtain a polyimide film. The obtained polyimide film had a thickness of 2 μm, no pinholes were observed, and SRa was 0.5 nm, which was very excellent in surface smoothness.

Example 2 The coated substrate had a center plane average roughness (SRa) of 40 nm.
A polyimide film was formed in the same manner as in Example 1 except that a glass substrate having a diameter of 100 mm was used. At the time of coating, no cissing of the coated liquid on the substrate occurred. The resulting polyimide film has a thickness of 2 μm.
m, no pinhole was observed, and SRa was 0.7 n
m and excellent surface smoothness.

Example 3 The surfactant was changed to BYK-333 containing a siloxane unit.
The reaction was carried out under the same conditions and conditions as in Example 1 except that (polyether modified dimethylpolysiloxane manufactured by Big Chemie Japan KK) was used to obtain a polyimide precursor solution (black). When the viscosity of this solution was measured, it was 20 ° C. and 1.8 poise. Further, this solution was prepared in the same manner and under the same conditions as in Example 1 to obtain an SRa of 50%.
A polyimide film was formed on an aluminum substrate (diameter 100 mm) having a diameter of nm. At the time of coating, no cissing of the coated liquid on the substrate occurred. The thickness of the obtained polyimide film was 2 μm, no pinhole was observed in the film surface, and SRa was 0.4 nm.

Example 4 A reaction was carried out under the same preparation and conditions as in Example 1 except that the surfactant was SH193 containing a siloxane unit (modified silicone oil, manufactured by Dow Corning Toray Co., Ltd.).
A polyimide precursor solution (black) of the present invention was obtained. The viscosity of this solution was 1.8 poise at 20 ° C. Further, this solution was prepared in the same manner and under the same conditions as in Example 1 using SRa.
Was formed on an aluminum substrate (diameter 100 mm) having a thickness of 50 nm. At the time of coating, no cissing of the coated liquid on the substrate occurred. The thickness of the obtained polyimide film was 2 μm, no pinhole was observed in the film surface, and SRa was 0.5 nm.

Example 5 N-methylpyrrolidone as a solvent was added to 500 g of 3,
3 ', 4,4'-biphenyltetracarboxylic acid (BPD
A) 70.9 g (0.24 mol) and 4,4′-
174.5 g of oxydiphthalic acid (ODPA) (0.56
mol), and then 77.13 g of methanol
(0.24 mol) and 3.86 g of triethylamine (the molar ratio between BPDA and ODPA was 7: 3). This solution was subjected to an esterification reaction in a hot water bath at an internal temperature of 80 ° C. for 2 hours with stirring, and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester and 4,4′-oxydiphthalic acid dimethyl ester A solution containing (3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester and 4,4′-oxydiphthalic acid dimethyl ester in a molar ratio of 7: 3) was obtained. After the reaction solution was cooled to 50 ° C., 160.9 g of 3,4′-oxydianiline (0.
80 mol), and dissolved by stirring for 2 hours to obtain a uniform polyimide precursor solution. Furthermore, a surfactant BYK-302 (manufactured by Big Chemie Japan KK, polyether-modified dimethylpolysiloxane) containing a siloxane unit was added in an amount of 0.5% by mass based on the solid content of the obtained polyimide precursor solution. Was added and stirred and dissolved at 25 ° C. until the system became uniform to obtain a polyimide precursor solution (black) (solid content concentration: 48% by mass). The viscosity of this solution was measured and found to be 1.20 at 20.degree.
It was 7 poise. Further, this solution was applied on an 8-inch silicon wafer substrate using a spin coater under the same conditions as in Example 1. At this time, no repelling of the applied liquid to the substrate occurred. Thereafter, the coated product was dried at 80 ° C. for 5 hours under a nitrogen atmosphere, and then dried under a nitrogen atmosphere for 30 hours.
Heat imidation was performed at 0 ° C. for 5 hours to obtain a 2 μm-thick polyimide film. No pinholes were observed in this polyimide film. Further, the solution was treated with 50 n of SRa.
Similarly, an aluminum substrate (diameter: 100 mm) was spin-coated and thermally imidized to obtain a polyimide film. The obtained polyimide film had a thickness of 2 μm, no pinholes were observed, and SRa was 0.5 nm, which was very excellent in surface smoothness.

Example 6 To 500 g of N-methylpyrrolidone as a solvent,
3 ', 4,4'-biphenyltetracarboxylic acid (BPD
A) 104.8 g (0.36 mol) and 4,4 ′
-Oxydiphthalic acid (ODPA) 110.5 g (0.3
6 mol) and then 68.37 g of methanol
(2.13 mol) and 3.42 g of triethylamine were added (the molar ratio of BPDA to ODPA was 5: 5). This solution was subjected to an esterification reaction in a hot water bath at an internal temperature of 80 ° C. for 2 hours with stirring, and 3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester and 4,4′-oxydiphthalic acid dimethyl ester A solution containing (3,3 ′, 4,4′-biphenyltetracarboxylic acid dimethyl ester and 4,4′-oxydiphthalic acid dimethyl ester in a molar ratio of 5: 5) was obtained. After the reaction solution was cooled to 50 ° C., 142.6 g of 3,4′-oxydianiline (0.4 g) was added.
(71 mol) and stirred and dissolved for 2 hours to obtain a uniform polyimide precursor solution. Further, a surfactant BYK-302 containing a siloxane unit was added in an amount of 2.0 g, which was 0.5% by mass based on the solid content of the obtained polyimide precursor solution.
Was added and the mixture was stirred and dissolved at 25 ° C. until the system became uniform, thereby obtaining a polyimide precursor solution (black) (solid content concentration: 45% by mass). When the viscosity of this solution was measured, it was 1.5 poise at 20 ° C. Further, this solution was spin-coated on an aluminum substrate (diameter: 100 mm) having an SRa of 50 nm in the same manner as in Example 1,
Thermal imidization was performed to obtain a polyimide coating. No repelling occurred on the substrate of the liquid applied at the time of coating. The obtained polyimide film had a thickness of 2 μm, no pinholes were observed, SRa was 0.5 nm, and was very excellent in surface smoothness.

Comparative Example 1 A reaction was carried out under the same preparation and conditions as in Example 1 except that no surfactant composed of silicone oil was added, to obtain a polyimide precursor solution (black) (solid content: 50% by mass). ). When the viscosity of this solution was measured,
Poise. Further, using this solution, a polyimide film was formed on an aluminum substrate (diameter 100 mm) having an SRa of 50 nm in the same manner and under the same conditions as in Example 1.
Although the thickness of the obtained polyimide film was 2 μm, eight pinholes were observed in the polyimide film due to repelling of the liquid applied at the time of application to the substrate.
Further, SRa was 3 nm.

Comparative Example 2 The amount of the surfactant BYK-302 used in Example 1 was 7% (35%) based on the solid content of the polyimide precursor solution.
The reaction was carried out under the same preparation and conditions as in Example 1 except for changing to g) to obtain a polyimide precursor solution (black) (solid content concentration: 50% by mass). When the viscosity of this solution was measured, it was 20 ° C. and 1.5 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. 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 concentration 30% by mass)

[0042]

As described above, the polyimide precursor solution of the present invention has a low viscosity even if the solute polyimide precursor is contained in the solvent at a high solid content ratio, and has a surface active property containing siloxane units. Since the composition contains an agent, repelling of the liquid applied at the time of coating does not occur on the substrate, and the state of the surface of the substrate is not affected. Therefore, from this polyimide precursor solution, there is no pinhole at a film thickness of 10 μm or less,
A polyimide film having excellent surface smoothness can be manufactured with high productivity.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeki Imamura 23 Uji Kozakura, Uji City, Kyoto Prefecture Unitika Central Research Laboratory (72) Inventor Fumiko Okui 23 Uji Kozakura, Uji City, Kyoto Unitika Central Research Center In-house F-term (reference) 4F071 AA60 AA60B AA67 AB07B AB08B AB09B AB28B AB29B AC16 AE10 AF27 AH12 BA02 BB02 BC01 BC02 BC12 4J002 CM041 CP032 EX036 FD312 FD316 GH00 GQ01 HA05 4J038 DJ03 NA03 MA03 MA03

Claims (3)

[Claims] 1. A 3,4′-oxydianiline represented by the following formula (1) and 3,3 ′, 4,4′- represented by the following formula (2):
A salt comprising biphenyltetracarboxylic acid and / or a derivative thereof and 4,4′-oxydiphthalic acid and / or a derivative thereof represented by the following formula (3) is dissolved in an organic solvent as a solute; 3,3 ', 4 shown in
4′-biphenyltetracarboxylic acid and / or a derivative thereof and 4,4′-oxydiphthalic acid represented by the formula (3) and / or
Or a surfactant having a molar ratio of 0: 100 to 90:10 with a derivative thereof and containing a siloxane unit represented by the following formula (4) per 100 parts by mass of a solute as a solute.
A polyimide precursor solution, which is contained in an amount of from 0.01 to 5 parts by mass. Embedded image (Wherein R, R ₁ , R ₂ , and R ₃ are each independently selected from a hydrogen atom and an alkyl group having 1 to 5 carbon atoms; R ₄ , R ₅
Is independently selected from a hydrogen atom, an alkyl group having 1 to 5 carbon atoms, an alkoxy group and a phenyl group. ) 2. The polyimide precursor solution according to claim 1, wherein the concentration of the salt as a solute is 30 to 80% by mass 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 heat imidization.