JP6846148B2 - Polyimide precursor solution and its production method, polyimide film production method and laminate production method - Google Patents

Description

The present invention relates to a polyimide precursor solution and a method for producing the same, a method for producing a polyimide film, and a method for producing a laminate in which a polyimide layer is laminated.

Polyimide is a material having excellent durability and heat resistance, and is widely used in electronic material applications, various display applications, automobile applications, and the like. Polyimide is obtained by applying a polyimide precursor (also referred to as polyamic acid or polyamic acid) solution, which is a precursor thereof, onto a substrate and drying and imidizing it by heat treatment.

Here, the polyimide precursor is generally obtained by reacting an acid component such as tetracarboxylic acid dianhydride, which is a raw material thereof, with a diamine or the like in a solvent, but as a reaction solvent used in the production thereof. In general, aprotic polar solvents such as N, N-dimethylacetamide (DMAc) and N-methyl-2-pyrrolidone (NMP) are generally used (see Patent Document 1, Patent Document 2 and Patent Document 3). ).

While the above solvent is highly versatile, foaming is likely to occur when a polyimide precursor solution is applied to form a polyimide film. Therefore, N, N, N', N'-tetramethylurea is used as a means for suppressing foaming. The tetracarboxylic dianhydride component and the diamine component are reacted in a mixed solvent with a solvent selected from the above-mentioned aprotonic polar solvent such as DMAc and NMP and glycol ethers such as diethylene glycol alkyl ether. A method for obtaining a polyamic acid is disclosed in Patent Document 4.

However, when the polyimide precursor is to be reacted with DMAc or NMP, the reaction takes a long time, so that the production efficiency is inferior. In addition, DMAc is suspected to be carcinogenic, and NMP is suspected to have reproductive toxicity, which may adversely affect the human body. Instead of these reaction solvents, production efficiency is high and there are few safety problems. Production of polyimide precursors and polyimides with other solvents is desired.

Some polyimides are provided with colorless and transparent properties in addition to high heat resistance and dimensional stability, and attempts are being made to apply these to display and touch panel applications by taking advantage of these characteristics. However, when the polyimide precursor solution is applied to a display or a touch panel application to form a polyimide film, the ease of forming the polyimide film and the formation of the polyimide film depend on the properties of the polyimide precursor solution to be used. It has been desired to provide a polyimide precursor solution suitable for such an application because it affects the characteristics, particularly the appearance and the light transmittance. Most of the widely known polyimides are yellowish when formed into a film, but unlike that, those having almost no coloring, for example, those having a YI of 20 or less are expressed as colorless and transparent in the present specification. To do.

Japanese Patent No. 5249203 Japanese Unexamined Patent Publication No. 60-147470 Japanese Unexamined Patent Publication No. 2007-332369 Japanese Unexamined Patent Publication No. 2015-155504

INDUSTRIAL APPLICABILITY According to the present invention, a polyimide precursor solution can be produced by easily dissolving the raw material of the polyimide precursor using a solvent safe for the human body, and it is possible to improve the working environment in the manufacturing process and simplify the manufacturing equipment. It is an object of the present invention to provide a method capable of producing a colorless and transparent polyimide precursor solution at room temperature in a short time without heating for a long time.

As a result of diligent studies to solve the above problems, in a polyimide precursor solution composed of a polyimide precursor and a solvent, the polyimide precursor is a fluorine-containing polyimide precursor, and the solvent is N. We have found that the above problems can be solved by using a solvent having no element and containing a solvent composed of molecules containing an alicyclic lactone structure or an alicyclic ketone structure, and completed the present invention.

That is, the present invention is a polyimide precursor solution composed of a polyimide precursor and a solvent, wherein the polyimide precursor is a fluorine-containing polyimide precursor containing a fluorine atom in its structure, and the solvent is N. It contains a solvent consisting of molecules containing an alicyclic lactone structure or an alicyclic ketone structure without elements, and the viscosity of the polyimide precursor solution at 25 ° C. is in the range of 500 to 350,000 cP and is solid. It is a polyimide precursor solution characterized in that the YI value of a polyimide precursor solution having a component concentration of 15 wt% measured in a quartz cell having a thickness of 10 mm is 20 or less.

（一般式（１）中、Ａはテトラカルボン酸残基を表し、Ｂはジアミン残基を表すが、Ａのテトラカルボン酸残基及びＢのジアミン残基のいずれか一方又は両方にフッ素原子を含有している。）
前記溶媒は、Ｎ元素を有さず、脂環式ラクトン構造又は脂環式ケトン構造を含む分子からなる溶媒を含有する、上記ポリイミド前駆体溶液である。 Further, the present invention is a polyimide precursor solution composed of a polyimide precursor and a solvent, and the polyimide precursor has a structure represented by the following general formula (1).

(In the general formula (1), A represents a tetracarboxylic acid residue and B represents a diamine residue, but a fluorine atom is added to either or both of the tetracarboxylic acid residue of A and the diamine residue of B. Contains.)
The solvent is the polyimide precursor solution which does not have an N element and contains a solvent composed of a molecule containing an alicyclic lactone structure or an alicyclic ketone structure.

The present invention is a method for producing a polyimide precursor solution obtained by reacting an acid component with a diamine and / or diisocyanate in a solvent.
A monomer having a fluorine atom as at least one component of the acid component and diamine and / or diisocyanate is used.
By using a solvent having no N element and consisting of a molecule containing an alicyclic lactone structure or an alicyclic ketone structure, the solvent can be used.
The feature is that the viscosity of the polyimide precursor solution at 25 ° C. is in the range of 500 to 350,000 cP, and the YI value of the polyimide precursor solution at a solid content concentration of 15 wt% measured in a 10 mm thick quartz cell is 20 or less. This is a method for producing a polyimide precursor solution.

Further, the present invention is a method for producing a polyimide film in which the polyimide precursor solution or the polyimide precursor solution obtained by the method for producing the polyimide precursor solution is applied onto a substrate and imidized.

The present invention is also a method for producing a laminate in which a polyimide layer in which the above-mentioned polyimide precursor resin solution is applied and imidized is laminated on a supporting base material having a surface roughness Ra of 0.3 to 30 nm.

In the present invention, after forming a laminate composed of a support base material and a polyimide layer by the above method for producing a laminate, a functional layer is further added on the polyimide layer and separated at the interface between the support base material and the polyimide layer. Also includes a method of producing a polyimide film with a functional layer.

According to the present invention, tetracarboxylic dianhydride and the like and diamine or diisocyanate can be easily produced in a work environment with less harmfulness without using DMAc or NMP, which is harmful to the human body and is suspected to be carcinogenic or reproductive toxicity. The polyimide precursor solution can be produced by dissolving in, and the polyimide precursor solution can be produced at room temperature in a short time without heating.
Further, as a result, according to the present invention, since the production of the polyimide precursor solution does not involve heating for a long time, the production process can be easily controlled, and the influence of coloring due to mixing of impurities and deformation due to temperature change. It is easy to improve the yield and the stability of the quality in the production of the colorless and transparent polyimide film and the polyimide laminate.

Hereinafter, the present invention will be described in detail.
The polyimide precursor solution of the present invention comprises a polyimide precursor and a solvent.
The polyimide precursor may be a polymer precursor having an imide bond, and may be a fluorine-containing polyimide precursor containing a fluorine atom in its structure.
The polyimide precursor has a tetracarboxylic acid residue and / or a tricarboxylic acid residue, a diamine residue and / or a diisocyanate residue, and fluorine in which a hydrogen atom is substituted in a structural unit constituting the precursor. Fluorine-containing polyimide precursors having atoms can be mentioned.
The solvent does not have an N element and contains a solvent composed of molecules containing an alicyclic lactone structure or an alicyclic ketone structure.
The polyimide precursor has a structure in which a tetracarboxylic acid and / or a tricarboxylic acid and a diamine are dehydrated and condensed, and any of the tetracarboxylic acid residue and / or the tricarboxylic acid residue and the diamine residue. Or all of them may contain a fluorine atom.
The polyimide precursor solution of the present invention is obtained, for example, by reacting a tetracarboxylic dianhydride with a diamine, and one or both of them contains a fluorine-containing compound.

本発明における好ましいポリイミド前駆体は、一般式（１）中、Ａはテトラカルボン酸残基であり、Ｂはジアミン残基であり、そのいずれか一方又は両方は含フッ素原子を有するものである。
一般式（１）の構造を有する化合物は、ポリアミド酸（ポリアミック酸）という。 The polyimide precursor in the present invention gives a molecular structure having a polyimide structure after the reaction, and the molecular structure may have an amide bond as well as an imide bond.
In the present invention, the polyimide also includes polyamide-imide. The tricarboxylic acid in the present invention is preferably one such as trimellitic acid, which easily reacts with a diamine to form an imide bond and an amide bond.
More specifically, the polyimide precursor in the present invention is represented by the following general formula (1), for example.

In the general formula (1), the preferred polyimide precursor in the present invention is one in which A is a tetracarboxylic acid residue and B is a diamine residue, and one or both of them has a fluorine-containing atom.
The compound having the structure of the general formula (1) is called a polyamic acid.

Further, in the general formula (1), A may be a tetracarboxylic acid residue, and is a known aromatic tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3', 4,4'. Arophilic tetracarboxylic dianhydride residues obtained from −biphenyltetracarboxylic dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic dianhydride, etc. and cyclobutane-1,2,3,4 Examples thereof include tetracarboxylic acid residues composed of alicyclic tetracarboxylic dianhydride residues obtained from −tetracarboxylic dianhydride, trans-1,4-diaminocyclohexane, etc., but the diamine residue of B can be exemplified. When does not contain fluorine, a tetracarboxylic acid residue containing a fluorine atom represented by the following formulas (2) -i to (2) -v is suitable.

When a tetracarboxylic acid containing a fluorine atom is used, 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride is preferably used.

式中、ｎは、０又は１であり、Ｘ_１〜Ｘ_４は、それぞれ独立して、Ｈ、Ｆ、炭素数１〜５までのアルキル基若しくはアルコキシ基、又は炭素数１〜５までのフッ素置換炭化水素基、Ｙ_１〜Ｙ_４は、ｎ＝１の場合に、それぞれ独立してＨ、Ｆ、炭素数１〜５までのアルキル基若しくはアルコキシ基、又は炭素数１〜５までのフッ素置換炭化水素基であるが、Ｘ_１〜Ｘ_４、Ｙ_１〜Ｙ_４のいずれか１つはＦ又はフッ素置換炭化水素基である。 In the general formula (1), B may be a diamine residue, and may be p-phenylenediamine, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-dimethylbenzidine, 3,3. '-Diamine benzidine, 2,2'-bis (4-aminophenyl) propane, 1,3-bis (3-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,4-bis Examples thereof include diamine residues composed of known aromatic diamines such as (4-aminophenoxy) benzene and 2,2-bis [4- (4-aminophenoxy) phenyl] propane, and other known aliphatic diamines. However, when the tetracarboxylic acid residue of A does not contain fluorine, a diamine residue containing a fluorine atom represented by the following formula (3) is suitable.

In the formula, n is 0 or 1, and X _{1 to} X ₄ are H, F, an alkyl group or an alkoxy group having 1 to 5 carbon atoms, or fluorine having 1 to 5 carbon atoms, respectively. Substituted hydrocarbon groups, Y _{1 to Y 4} , are independently H, F, alkyl or alkoxy groups having 1 to 5 carbon atoms, or fluorine substitutions having 1 to 5 carbon atoms, respectively, when n = 1. Although it is a hydrocarbon group, _{any one of X 1 to} X _{4 and} Y _{1 to Y 4} is an F or fluorine-substituted hydrocarbon group.

When using a diamine containing a fluorine atom, 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 2,2'-bis [4- (4-aminophenoxy) phenyl] hexa Fluoropropane is preferably used.

As described above, in the present invention, a fluorine-containing compound is used for either or both of the tetracarboxylic dianhydride and the diamine, whereby a polyimide precursor solution and a polyimide film having excellent transparency can be obtained.

The solvent in the polyimide precursor solution of the present invention has a molecular structure containing an alicyclic lactone structure or an alicyclic ketone structure in the molecular structure and does not contain an N element. Specific examples thereof include γ-butyrolactone (boiling point: 204 ° C.), cyclohexanone (boiling point: 155.6 ° C.), cyclopentanone (boiling point: 130 ° C.), δ-valerolactone (boiling point: 230 ° C.), and the like. Can be used alone or in combination of two or more. Preferred are γ-butyrolactone and δ-valerolactone, which have a molecular structure containing an alicyclic lactone structure, and among these solvents, γ-butyrolactone is particularly preferable.

The solvent preferably has a boiling point in the range of 100 to 240 ° C. If the boiling point is less than 100 ° C, the solvent will volatilize during the reaction under a nitrogen stream, which may hinder a uniform reaction. If the boiling point exceeds 240 ° C, the solvent will be a film when heat-treated to form a polyimide film. Since it remains in the film, it may affect the physical properties of the film.

The viscosity of the polyimide precursor solution of the present invention at 25 ° C. needs to be in the range of 500 to 350,000 cP, preferably in the range of 1500 to 100,000, and more preferably in the range of 2000 to 50,000. If the viscosity of the polyimide precursor solution is less than 500 cP, it is difficult to form a film with a uniform film thickness, and if it exceeds 350,000 cP, it is difficult to spread the film with an applicator or the like. The processability of the polyimide precursor solution is impaired.

When a general polyimide is formed into a film, it exhibits a yellowish property, but a solution of a polyimide precursor containing a fluorine atom in its structure of the present invention gives a colorless and transparent polyimide film. Regarding the properties of the precursor solution, the YI value of the polyimide precursor solution having a solid content concentration of 15 wt% measured in a quartz cell having a thickness of 10 mm is 20 or less.

Next, the method for producing the polyimide precursor solution of the present invention will be described in detail.
The present invention is a method for producing a polyimide precursor solution obtained by reacting an acid component with a diamine and / or diisocyanate in a solvent.
A monomer having a fluorine atom as at least one component of the acid component and diamine and / or diisocyanate is used.
In the polyimide precursor solution of the present invention, first, diamine or diisocyanate is dissolved in a solvent, and then tetracarboxylic acid or tricarboxylic acid or an anhydride thereof is added to the solution to produce a polyimide precursor. In this case, the order of dissolution of the monomers in the solvent may be reversed. As the solvent, one or more organic solvents having both an alicyclic structure and a ketone group structure in the above-mentioned molecular structure can be used, and by using them, diamine or diisocyanate and tetracarboxylic dianide can be used. The anhydride monomer can be easily dissolved.
As the acid component used in the method for producing the polyimide precursor solution of the present invention, known ones can be used, but tetracarboxylic acid or tricarboxylic acid capable of reacting with an amine to form an imide bond, or an anhydride thereof is preferable.

In addition, the above-mentioned monomer such as diamine or diisocyanate and tetracarboxylic dianhydride can be easily combined with an organic solvent having both an alicyclic structure and a ketone group in the above-mentioned molecular structure as long as the effect of the present invention is not impaired. A general-purpose organic solvent that can be dissolved can also be used in combination. Specific examples thereof include dimethylacetamide, dimethylformamide, n-methylpyrrolidinone, 2-butanone, diglime, xylene, triethylene glycol dimethyl ether and the like. However, even when N elements such as dimethylacetamide, dimethylformamide, and n-methylpyrrolidinone are contained, the ratio thereof is preferably 30 wt% or less in the total solvent, and it is particularly preferable that they are not substantially contained.

The polyimide precursor solution is produced by using a tetracarboxylic acid dianhydride and a monomer having a fluorine atom in either diamine or diisocyanate as a raw material monomer, having no N element, and having an alicyclic lactone structure or an alicyclic structure. It is not limited to using a solvent containing a solvent composed of a molecule containing a ketone structure. If the solvent specified in the present invention is used, the reaction for dissolving in the raw material monomer and for making the polyimide precursor can be sufficiently proceeded at room temperature, and the reaction can be completed in a relatively short time in particular. Therefore, the production efficiency of the polyimide precursor solution is also excellent.
Furthermore, if the solvent specified in the present invention is used, the obtained polyimide precursor has a low yellowness, that is, a small amount of coloring. Furthermore, by imidizing the polyimide precursor solution, a polyimide film having low yellowness and less coloring can be obtained.

In the method for producing a polyimide precursor solution of the present invention, the viscosity of the polyimide precursor solution at 25 ° C. is in the range of 500 to 350,000 cP, and the polyimide precursor solution having a solid content concentration of 15 wt% is prepared in a 10 mm thick quartz cell. It is necessary that the measured YI value is 20 or less, more preferably 10 or less, and these viscosities and optical properties in the precursor state can be controlled by appropriately controlling the above reaction conditions. The reaction temperature is preferably in the range of room temperature (25 ° C.) ± 20 ° C., more preferably in the range of 10 to 30 ° C. The reaction time is preferably in the range of 1 to 10 hours. The reaction time is preferably as short as 8 hours because it is desirable from the viewpoint of production efficiency, but it is more preferably in the range of 2 to 8 hours from the viewpoint of ease of controlling the molecular weight (viscosity). If the reaction temperature or time deviates from the above range, it may be difficult to control the characteristics of the polyimide precursor solution within the above desired range under good production efficiency.

The polyimide film of the present invention is not particularly limited, but for example, a polyimide precursor solution which is a raw material of the polyimide film is cast-coated on an arbitrary support base material using an applicator, and is applied onto the support base material. In general, a gel film having self-supporting property is obtained by heating and drying with a polyimide film, and then heat-treated at a higher temperature to imidize the film to obtain a polyimide film.

The material of the supporting base material is not particularly limited as long as it can withstand the heat treatment temperature at the time of imidization, and examples thereof include an inorganic material, a metal, and a heat-resistant organic film. Specifically, a metal foil such as glass, a resin film, or a copper foil can be used. When a glass or resin film is used as the support base material, a film-like polyimide film can be obtained by peeling off the polyimide film formed on the support base material after imidization, and a metal foil is used as the support base material. When is used, a method of removing the metal foil by etching or the like is exemplified. From the viewpoint of peelability from the supporting base material and the transparency of the polyimide film, it is preferable to use a base material having a surface roughness Ra in the range of 0.3 to 30 nm.

The casting method is not particularly limited, and a known method, for example, a spin coater, a spray coater, a bar coater, or a method of extruding from a slit-shaped nozzle can be applied as long as a predetermined thickness accuracy can be obtained. Further, the surface of the substrate or the substrate to be coated with the resin solution may be appropriately surface-treated and then coated.

After applying the polyimide precursor on the substrate, the drying conditions should be 150 ° C or lower for 2 to 30 minutes, and the heat treatment for imidization should be performed at a temperature of 130 to 360 ° C for about 0.5 to 60 minutes. Is appropriate. The heating time (hereinafter referred to as high temperature holding time) in the high temperature heating temperature range from a temperature 20 ° C. lower than the maximum heating temperature (maximum ultimate temperature) at the time of temperature rise in this heat treatment to the maximum ultimate temperature shall be within 60 minutes. Is preferable. If this high temperature holding time exceeds 60 minutes, the production efficiency of the process may deteriorate, and the transparency of the polyimide film may decrease due to coloring or the like. In order to maintain transparency, it is better that the high temperature holding time is short, but if the time is too short, the effect of the heat treatment may not be sufficiently obtained. The optimum high temperature holding time varies depending on the heating method, the heat capacity of the base material, the thickness of the polyimide film, and the like, but is preferably 0.5 to 60 minutes, and particularly preferably 2 to 50 minutes.

By imidization by the above heat treatment, a laminate in which a polyimide layer is formed on a supporting base material can be obtained.

Further, the polyimide film obtained by the above heat treatment has a 1% thermal decomposition temperature Td1 of 500 ° C. or higher in thermogravimetric analysis, a light transmittance of 80% or higher at 450 nm at a film thickness of 15 μm, and a coefficient of thermal expansion of 60 ppm. It is less than / K. If the 1% thermal decomposition temperature Td1 in the thermogravimetric analysis is less than 500 ° C., the use in applications requiring heat resistance is restricted and unfavorable, and if the light transmittance is less than 80%, it is organic as a display element. When an EL element is used, the light emitted from the light emitting layer of the organic EL (wavelength is mainly 380 nm to 780 nm) does not sufficiently transmit through the polyimide film. By satisfying the above characteristics, for example, it can be suitably used for an EL display device having a bottom emission structure.

In addition to the above characteristics, the polyimide film of the present invention can have a glass transition temperature of 330 ° C. or higher. If the glass transition temperature is lower than the above temperature, the polyimide film may be deformed due to the heat generated when the display element is mounted.

The film thickness of the polyimide film is not limited, but is preferably in the range of 5 to 30 μm, more preferably in the range of 10 to 20 μm.

In the present invention, in the laminate in which the polyimide layer is formed on the support base material, the support base material and the polyimide film can be easily separated (peeled).

Such a laminate can be obtained by using the polyimide precursor solution exemplified above and applying it by salivation on an appropriate supporting base material. The ease of separation (peeling) is such that it can be easily peeled off by human hands, and when expressed in terms of peeling strength, the adhesive strength at the interface between the polyimide layer and the supporting base material is 0.1. The range is ~ 20 N / m. The range of peel strength is not limited, but in order to prevent peeling at the interface between the polyimide layer and the supporting base material when the laminate is conveyed by the roll-to-roll method, 0.1 N / m. It is better to do the above. On the other hand, in order to facilitate peeling, it is preferably 20 N / m or less.

In the laminate of the present invention, a functional layer can be further provided on the polyimide layer. If the functional layer is provided on the laminate in which the support base material and the polyimide layer are laminated, it becomes easy to form the functional layer even if it is a thin polyimide layer, and after the functional layer is provided, the support base material is provided. A polyimide film with a functional layer can be manufactured by separating the film at the interface between the polyimide layer and the polyimide layer. This method is particularly advantageous when producing a thin polyimide film with a functional layer having a thickness of 20 μm or less.

Here, the functional layer constitutes a liquid crystal display device, an organic EL display device, a display device such as an electronic paper or a touch panel, a lighting device, a detection device, a layer constituting the component thereof, or various functional material layers. Specifically, it means one or a combination of one or more of an electrode layer, a light emitting layer, a gas barrier layer, an adhesive layer, an adhesive layer, a thin film transistor, a wiring layer, a transparent conductive layer, and the like.
The polyimide film provided with the functional layer is used in an organic EL lighting device, a conductive film on which ITO and the like are laminated, a gas barrier film that prevents the penetration of moisture and oxygen, flexible circuit board components, a touch panel, and a vapor deposition mask. , It is used as a functional material having various functions such as a substrate for a fan-out wafer level package (FOWLP). Preferably, it is used as a flexible device.

A polyimide film provided with a functional layer is called a flexible device, which is an element for an electronic device or a member for an electronic device having flexibility to the extent that it can be bent by hand. The form in which the flexible device is mounted on an electronic device may be a bending application in which the curvature changes during use, a fixed curved surface in which the curvature does not change, or a flat surface.

Hereinafter, the present invention will be described in more detail based on Examples, but the present invention is not limited to the contents of these Examples.

First, abbreviations for monomers and solvents for synthesizing polyimide (precursor), methods for measuring various physical properties in the examples, and the like are shown below.

TFMB: 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl DAPE: 4,4'-diaminodiphenyl ether m-TB: 2,2'-dimethylbenzidine HF-BAPP: 2,2'- Bis [4- (4-aminophenoxy) phenyl] Hexafluoropropane TPE-R: 1,3-bis (4-aminophenoxy) benzene 6FDA: 2,2'-bis (3,4-dicarboxyphenyl) hexafluoro Propane dianhydride PMDA: pyromellitic dianhydride BPDA: 3,3', 4,4'-biphenyltetracarboxylic dianhydride CBDA: cyclobutane-1,2,3,4-tetracarboxylic dianhydride GBL : Γ-Bylolactone DMAc: N, N-dimethylacetamide NMP: N-methyl-2-pyrrolidone

<Viscosity, molecular weight>
The viscosity was measured at 25 ° C. with a cone plate type viscometer (manufactured by Tokimec Co., Ltd.) equipped with a constant temperature water tank. The weight average molecular weight (Mw) measured by GPC is shown in the table.

<Light transmittance, yellowness: YI>
As for the light transmittance, the transmittance of each wavelength of 300 to 800 nm was measured with a spectrophotometer (UV-3600 Plus manufactured by Shimadzu Corporation).
Further, the YI value was calculated from the formula of YI = 100 (1.28X-1.06Z) / Y from the X, Y, Z values measured by the same apparatus.
The yellowness of the solution was calculated by putting the solution in a glass cell of 10 mm square and measuring and calculating the YI value in the same manner.

<Coefficient of thermal expansion: CTE>
A polyimide film having a size of 3 mm × 15 mm is heated in a temperature range of 30 ° C. to 280 ° C. at a constant temperature rising rate (10 ° C./min) while applying a load of 5.0 g using a thermomechanical analysis (TMA) device. -The temperature was lowered and a tensile test was performed, and the coefficient of thermal expansion (ppm / K) was measured from the change in the amount of elongation of the polyimide film with respect to the temperature change from 250 ° C. to 100 ° C.

<ITO film formation>
ITO (indium tin oxide) was sputtered onto the produced polyimide film to a thickness of 100 nm.
◯: The adhesion of the ITO electrode is good, and the conductive film is uniformly formed.

<Peelability>
The possibility of peeling from the polyimide film alone or the polyimide film provided with the functional layer with a thickness of 0.7 mm is shown.
◯: The polyimide film alone or the polyimide film provided with the functional layer can be peeled off from the supporting base material without tearing.

[Example 1]
(Polyimide precursor solution A)
Under a nitrogen stream, 8.4914 g of TFMB was dissolved in 70 g of solvent γ-butyrolactone in a 300 ml separable flask. Next, 1.4680 g of 6FDA was added to this solution and stirred, then 5.0406 g of PMDA was added, 15 g of γ-butyrolactone was added so that the solid content became 15 wt%, and the mixture was stirred at room temperature for 5 hours to carry out a polymerization reaction. It was. After the reaction, a viscous transparent polyimide precursor solution was obtained.
The characteristics of the obtained polyimide precursor solution are shown in Table 1.

The polyimide precursor solution A obtained above was applied onto a glass substrate having a thickness of 0.7 mm and a surface roughness Ra = 1.4 nm using an applicator so that the film thickness after heat treatment was 10 to 15 μm. The temperature was raised from 90 ° C. to 360 ° C. over a minute to obtain a polyimide film A.
Table 3 shows the results of various evaluations of the obtained polyimide film A.

[Examples 2 to 7, Comparative Examples 1 to 7]
The polymerization reaction was carried out in the same manner as in Example 1 except that the raw materials of the polyimide raw material diamine and the tetracarboxylic dianhydride and the polymerization conditions (solvent, polymerization time) were changed to those shown in Table 1 to obtain a polyimide precursor solution. It was.
The characteristics of the obtained polyimide precursor solution are shown in Tables 1 and 2.

When the appearance of the polyimide precursor solution obtained in each example was visually judged, the appearance of the polyimide precursor solution obtained in Examples 1 to 7, Comparative Example 1, and Comparative Examples 5 and 6 was colorless to pale. Although it was transparent to yellow, the appearance of the polyimide precursor solution obtained in Comparative Example 2 was colored yellow although it showed transparency.
Further, in Comparative Example 3 and Comparative Example 4 in which the acid component containing no fluorine and the diamine were used, the monomer could not be completely dissolved in the solvent used, and the polymerization did not proceed sufficiently. Further, in Comparative Example 7, the solvent used did not increase the viscosity and molecular weight, and the polymerization did not proceed sufficiently.

(Evaluation of polyimide film)
A polyimide film was formed in the same manner as in Example 1 using each polyimide precursor solution, and the results of various evaluations of the obtained polyimide film are shown in Tables 3 and 4 (compared with Examples F1 to F7). Examples F1 to F2 and F5 to F6). A polyimide film could not be formed from the polyimide precursors J, K and L corresponding to Comparative Examples 3, 4 and 7.
Further, when the 1% thermogravimetric reduction temperature (Td1%) of the polyimide film of Example F1 was confirmed, it was 519 ° C.
The 1% thermogravimetric reduction temperature (Td1%) is a constant temperature rise rate (10 ° C.) of a polyimide film weighing 5 to 10 mg in a nitrogen atmosphere with a thermogravimetric analysis (TG) device TG / DTA6200 manufactured by SEIKO. Measure the weight change when the temperature is raised from 30 ° C to 550 ° C at (/ min), and set the temperature when the weight loss rate is 1% based on the weight of 200 ° C (0%) to the 1% thermogravimetric weight loss temperature. (Td1%).
Although the polyimide film of Comparative Example F1 could be formed into a film, the resin viscosity of the polyimide precursor solution D was extremely higher than that of the precursor solution of Example, and the processability was poor.

Claims (9)

A polyimide precursor solution composed of a polyimide precursor and a solvent, wherein the polyimide precursor is a fluorine-containing polyimide precursor containing a fluorine atom in its structure, and the polyimide precursor is at a temperature of 10 to 30 ° C. a polyimide precursor was carried out 2-8 hours, the solvent has no N element contains a solvent selected from γ-butyrolactone or δ-valerolactone comprise molecules containing an alicyclic lactone structure, The viscosity of the polyimide precursor solution at 25 ° C. is in the range of 500 to 350,000 cP, and the YI value of the polyimide precursor solution having a solid content concentration of 15 wt% measured in a 10 mm thick quartz cell is 20 or less. A method for producing a featured polyimide precursor solution. The method for producing a polyimide precursor solution according to claim 1, wherein the polyimide precursor has a structural unit represented by the following general formula (1).

(In the general formula (1), A represents a tetracarboxylic acid residue and B represents a diamine residue, but a fluorine atom is added to either or both of the tetracarboxylic acid residue of A and the diamine residue of B. Contains.) In the general formula (1), A is 2,2'-bis (3,4-dicarboxyphenyl) hexafluoropropane dianhydride, pyromellitic dianhydride, 3,3', 4,4'-biphenyltetra. At least one tetracarboxylic dian residue selected from carboxylic acid dianhydride, cyclobutane-1,2,3,4-tetracarboxylic dianhydride, and cyclohexane-1,2,4,5-tetracarboxylic dianhydride. It is a group, and B is 2,2'-bis (trifluoromethyl) -4,4'-diaminobiphenyl, 4,4'-diaminodiphenyl ether, 2,2'-dimethylbenzidine, 2,2'-bis [4. -(4-Aminophenoxy) phenyl] Hexafluoropropane, trans-1,4-diaminocyclohexane is at least one diamine residue, and either or both of the tetracarboxylic dian residue and the diamine residue. The method for producing a polyimide precursor solution according to claim 2, which contains a fluorine amino acid. The polyimide according to any one of claims 1 to 3, which provides a heat-resistant polyimide having a light transmittance of 80% or more at 450 nm and a coefficient of thermal expansion of less than 60 ppm / K at a thickness of 15 μm of a polyimide obtained from a polyimide precursor. A method for producing a precursor solution. A method for producing a polyimide precursor solution obtained by reacting an acid component with a diamine and / or diisocyanate in a solvent at a temperature of 10 to 30 ° C. for 2 to 8 hours.
A monomer having a fluorine atom as at least one component of the acid component and diamine and / or diisocyanate is used.
In the solvent, without a N element, by using a solvent selected from alicyclic lactone structure comprise molecules containing γ-butyrolactone or δ-valerolactone,
The feature is that the viscosity of the polyimide precursor solution at 25 ° C. is in the range of 500 to 350,000 cP, and the YI value of the polyimide precursor solution at a solid content concentration of 15 wt% measured in a 10 mm thick quartz cell is 20 or less. A method for producing a polyimide precursor solution. The polyimide precursor solution obtained by the process according to claim 1 to 5 or 1 Kouki mounting of the polyimide precursor solution was coated on a substrate to obtain a polyimide film was imidized, producing a polyimide film. The method for producing a polyimide film according to claim 6 , wherein the light transmittance at 450 nm at a thickness of 15 μm is 80% or more and the coefficient of thermal expansion is less than 60 ppm / K. Surface roughness Ra on a supporting substrate of 0.3～30Nm, coating a polyimide precursor solution obtained by the production method of the polyimide precursor solution of claim 1-5 or 1 Kouki mounting imidization A method for producing a laminated body in which a polyimide layer is laminated, which includes a step of laminating. A function of forming a laminate composed of a support base material and a polyimide layer by the method for producing a laminate according to claim 8 , further adding a functional layer on the polyimide layer, and separating the laminate at the interface between the support base material and the polyimide layer. A method for producing a layered polyimide film.