TWI813543B - Method for producing polyimide precursor, polyimide and transparent polyimide film - Google Patents

Abstract

The invention provides a method for manufacturing a polyimide precursor, polyimide and a transparent polyimide film. The polyimide precursor has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride. The polyimide precursor has structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and derived from 1,2,3,4-cyclobutanetetracarboxylic The structural units of acid dianhydride, and among all the structural units derived from acid dianhydride, it contains more than 70 mol% of the structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride. When the imide precursor is imidized to form polyimide, the light transmittance is less than 5% at 308 nm, more than 70% at 400 nm, and the thermal expansion coefficient is less than 45 ppm/K.

Description

Method for manufacturing polyimide precursor, polyimide and transparent polyimide film

The present invention relates to a transparent film material or a transparent flexible substrate material, especially a transparent material having high transparency, low thermal expansion coefficient, high heat resistance and laser lift-off properties. Polyimide as a resin substrate material, its precursor, and a method for manufacturing a transparent polyimide film.

The performance of electronic equipment is rapidly advancing and there is a tendency to become lighter and thinner. Along with this, there is an increasing demand for high performance of components used in electronic equipment and substrates on which the components are mounted. . In displays and touch screen applications, glass substrates are used as the base material of display panels. However, in order to achieve further thinning, weight reduction, and flexibility, the processing cost of the roll-to-roll process is increased. Resin substrate materials were developed to reduce the However, resins are generally inferior to glass in terms of dimensional stability, transparency, heat resistance, etc., so various studies are being conducted.

Examples of display applications include large displays such as televisions, or small displays such as mobile phones, personal computers, and smartphones. For example, in organic electroluminescence (EL) devices, thin film transistors (TFTs) are mounted. ) and other components, glass substrates are used as support substrates. In addition, in touch screen applications, there are equally strong requirements for resin substrate materials that can replace glass substrates. In this case, it is also required to have a low coefficient of thermal expansion (CTE) to prevent warping and other problems. From a viewpoint, ideal is, for example, 45 ppm/K or less.

As such a resin substrate material, polyimide is one of the promising materials because it has excellent heat resistance and dimensional stability.

In recent years, in order to obtain a thin polyimide substrate, the following method has been proposed: using a glass substrate as a supporting base material, temporarily forming a polyimide film on the supporting base material, and then mounting electronic components on the polyimide film. The imide film is peeled off from the glass substrate as the supporting base material. For example, Patent Document 1 discloses a polyimide precursor resin composition for forming a flexible device substrate manufactured by peeling off a carrier substrate. The glass transition temperature is 300°C or higher and the thermal expansion coefficient is 20 ppm/ K or less. However, transparency etc. were not studied. Patent Document 2 discloses a laminate including a polyimide film and an inorganic substrate, which has high light transmittance and low out gas. The polyimide film is a polyimide precursor with a specific structure. The solution is cast on an inorganic substrate, dried and imidized. However, the coefficient of thermal expansion (CTE) of polyimide exceeds 45 ppm/K. Therefore, the difference with the thermal expansion coefficient of glass substrate is 10 ppm/K or less, resulting in poor shape stability.

In addition, Patent Document 3 discloses that in order to reduce the coloring of polyimide, the transmittance of diamine and tetracarboxylic dianhydride used as raw materials is strictly controlled. Patent Document 4 discloses a structure derived from a diamine and a structure derived from a tetracarboxylic dianhydride and derived from a specific alicyclic tetracarboxylic acid in order to produce a colorless, transparent, low CTE polyimide film. A polyimide precursor and a resin composition in which the amide imidization rate of the amide bond of carboxylic dianhydride is 10% to 100%. In addition, Patent Document 5 proposes to react a diamine compound and a compound containing three or more amino groups with tetracarboxylic dianhydride, and Patent Document 6 proposes the use of a polyimide-based precursor containing fine particles. The polymer solution is used to form the particle-containing layer.

However, the reality is that expectations for the development of a transparent polyimide film that can be used as a practical heat-resistant transparent resin substrate material that can replace a glass substrate and satisfy required characteristics such as dimensional stability and its manufacturing method are still ongoing. [Prior Art Documents] [Patent Documents]

[Patent Document 1] Japanese Patent Laid-Open No. 2010-202729 [Patent Document 2] Japanese Patent Laid-Open No. 2012-40836 [Patent Document 3] Japanese Patent Laid-Open No. 2013-23583 [Patent Document 4] International Publication 2015 /122032 [Patent Document 5] Japanese Patent Application Laid-Open No. 2014-210896 [Patent Document 6] Japanese Patent Application Laid-Open No. 2013-209498

[Problems to be Solved by the Invention] Against this background, an object of the present invention is to provide a thin polyimide film that is excellent in dimensional stability, transparency, and heat resistance and can be easily peeled off from a supporting base material. The polyimide precursor and the polyimide of the heat-resistant transparent resin substrate material, and the manufacturing method of the transparent polyimide film.

[Technical Means for Solving the Problem] The present invention is a polyimide precursor having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and is characterized in that: it has a structural unit derived from 2,2'-bis( The structural unit of trifluoromethyl)-4,4'-diaminobiphenyl (alias: 2,2'-bis(trifluoromethyl)benzidine), and derived from 1,2,3,4-cyclobutane Structural units of alkane tetracarboxylic dianhydride, and among all structural units derived from acid dianhydride, more than 70 mol% of structural units derived from 1,2,3,4-cyclobutane tetracarboxylic dianhydride are included , when the polyimide precursor is imidized to form the polyimide, the light transmittance is less than 5% at 308 nm, more than 70% at 400 nm, and the thermal expansion coefficient is 45 ppm/K or less.

The polyimide precursor preferably satisfies at least one of the following. 1) Contains 50 mol% or more of structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl among all structural units derived from diamines. 2) Containing less than 50 mol% of structural units derived from diamines other than 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl among all structural units derived from diamines , or contain less than 30 mol% of structural units derived from acid dianhydrides other than 1,2,3,4-cyclobutanetetracarboxylic dianhydride among all the structural units derived from acid dianhydride. 3) The structural unit derived from acid dianhydride also includes a structural unit derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride, a structural unit derived from pyromellitic acid dianhydride, or derived from Structural unit of 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. 4) The structural unit derived from diamine also contains a structural unit derived from 2,2'-dimethyl-4,4'-diaminobiphenyl.

In addition, the present invention is a polyimide having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and is characterized in that: it has a structural unit derived from 2,2'-bis(trifluoromethyl)-4 , structural units of 4'-diaminobiphenyl, and structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and all structural units derived from acid dianhydride contain 70 moles Ear% or more of structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride; and the light transmittance is less than 5% at 308 nm and more than 70% at 400 nm, and the thermal expansion The coefficient is 45 ppm/K or less.

The polyimide should preferably have a yellowness of 6 or less. Furthermore, the polyimide can be used excellently as a transparent resin substrate material.

The invention is a method for manufacturing a transparent polyimide film, which includes the following steps: coating a polyimide precursor or a resin solution thereof on the surface of a support; and applying the polyimide precursor or a resin solution thereof to the surface of a support. The step of heating to imidize to form a polyimide layer on the surface of the support; and the step of peeling the polyimide layer from the support to obtain a polyimide film, The manufacturing method of the polyimide film is characterized in that the polyimide precursor is made to contain 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl ( Alias: 2,2'-bis(trifluoromethyl)benzidine) and 2,2'-dimethyl-4,4'-diaminobiphenyl (alias: 2,2'-dimethylbenzidine) It is obtained by reacting one or two diamines with an acid dianhydride containing 1,2,3,4-cyclobutanetetracarboxylic dianhydride; and the thermal expansion coefficient of the polyimide film is 45 ppm/ K or less, the transmittance is less than 5% under 308 nm light and more than 70% under 400 nm light.

The method for producing a transparent polyimide film of the present invention preferably satisfies at least one of the following. 1) Containing more than 50 mol% of all diamines selected from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 2,2'-dimethyl-4, It is a diamine of 4'-diaminobiphenyl, and contains more than 70 mol% of 1,2,3,4-cyclobutanetetracarboxylic dianhydride in all acid dianhydrides. 2) Contain 1 mol% to 50 mol% of all diamines except 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl or 2,2'-dimethyl -Diamines other than 4,4'-diaminobiphenyl, or 1,2,3,4-cyclobutanetetracarboxylic dianhydride containing 1 to 30 mol% of all acid dianhydrides. of acid dianhydride. 3) The yellowness of the obtained polyimide film is 6 or less. 4) The interface between the polyimide layer and the support is irradiated with laser light to peel the polyimide layer from the supporting base material.

Another embodiment of the present invention is a method for manufacturing a transparent polyimide film with a functional layer, which is characterized in that: in the method for manufacturing a transparent polyimide film, a method is provided for forming a transparent polyimide film on the polyimide layer. After the functional layer, the polyimide layer with the functional layer is peeled off from the support. In this case, the functional layer is preferably selected from a transparent conductive layer, a wiring layer, a conductive layer, a gas barrier layer, a thin film transistor, an electrode layer, a luminescent layer, an adhesive layer, an adhesive layer, a transparent resin layer, and a color filter. Any one or two or more layers from the group consisting of sheet resist and hard coat layer.

[Effects of the Invention] The polyimide precursor of the present invention can be formed into a polyimide excellent in dimensional stability, transparency, and heat resistance by imidizing it. In addition, after the polyimide precursor of the present invention is coated on a support base material to form a polyimide film, the film peelability (laser peeling properties) from the support base material is also excellent, so the support base can be used The ultra-thin polyimide film can be obtained easily and easily. The polyimide of the present invention effectively utilizes the above characteristics and can be preferably used as a practical flexible heat-resistant transparent resin substrate material that can replace the glass substrate in displays or touch screens and satisfies required characteristics such as dimensional stability.

According to the production method of the present invention, a thin transparent polyimide film that is excellent in dimensional stability, transparency, and heat resistance, and is also excellent in film peelability (laser peeling characteristics) from the supporting base material can be easily obtained. The transparent polyimide film obtained by the present invention effectively utilizes the above characteristics and can be preferably used as a practical flexible heat-resistant material that can replace the glass substrate in displays or touch screens and satisfies required characteristics such as dimensional stability. Transparent resin substrate material.

The polyimide precursor of the present invention (hereinafter also referred to as "the polyimide precursor") has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride, and as a structure derived from the diamine Units having units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl or 2,2'-dimethyl-4,4'-diaminobiphenyl One or two structural units (U1) having a structural unit (U2) derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride as a structural unit derived from an acid dianhydride, and including all Structural units (U2) that constitute more than 70 mol% of the structural units derived from acid dianhydride.

It is known that a polyimide precursor having a structural unit derived from a diamine and a structural unit derived from an acid dianhydride can be represented by the following general formula (1). [-OCX(COOH)2CO-HN-Y-NH-] (1) In addition, the polyimide obtained by imidizing the polyimide precursor can be represented by the following general formula (2). [-N(OC)2X(CO)2N-Y-] (2) In Formula (1) and Formula (2), X is a tetravalent residue generated by removing two acid anhydride groups from an acid dianhydride, and Y is A divalent residue resulting from the removal of two amino groups from a diamine.

The polyimide precursor of the present invention is selected from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (code: TFMB) represented by the following formula (3) or As the diamine, one or two diamines among 2,2'-dimethyl-4,4'-diaminobiphenyl (code: m-TB) represented by the following formula (3b) are used. By using 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (code: TFMB) represented by the following formula (3) as the structural unit (Y) derived from the diamine And it has a structural unit derived from TFMB represented by the following formula (3a). [Chemical 1]

In the polyimide precursor of the present invention, TFMB or m-TB is used as an essential component as the diamine. The structural units derived from TFMB or m-TB are preferably 50 mol% or more, more preferably 70 mol% or more, and still more preferably 80 mol% or more of all the structural units derived from diamines. If it is within the above range, the polyimide obtained by imidizing the present polyimide precursor has excellent light transmittance at 400 nm and improves the transparency of the flexible substrate, which is preferable. When TFMB or m-TB is used in the above range, the visible light transmittance of the polyimide becomes excellent and the transparency of the flexible substrate is improved, which is preferable.

The polyimide precursor of the present invention uses 1,2,3,4-cyclobutanetetracarboxylic dianhydride (code: CBDA) represented by the following formula (4) as the tetracarboxylic dianhydride. Therefore, As the structural unit (X) derived from tetracarboxylic dianhydride, there is a structural unit derived from CBDA represented by the following formula (4a). [Chemicalization 2]

The present polyimide precursor contains preferably 70 mol % or more, more preferably 80 mol % or more of CBDA-derived structural units among all structural units derived from tetracarboxylic dianhydride. If it is within the above range, the polyimide obtained by imidizing the polyimide precursor maintains transparency, but the CTE becomes further lower. The dimensions of the flexible substrate using the polyimide It is excellent in stability and can suppress warpage of flexible devices, so it is preferred.

Thus, a polyimide precursor having a structural unit represented by the following formula (5) containing a structure derived from TFMB or m-TB and a structure derived from CBDA can be obtained, and then imidized. And a polyimide having a structural unit represented by the following formula (6) can be obtained. In addition, formulas (5) and (6) show that when TFMB is used as a raw material for a structure derived from a diamine, when m-TB is used as a raw material, trifluoromethyl (CF ₃ ) becomes When TFMB and m-TB are used together, the methyl group (CH ₃ ) has a structure in which both of them coexist depending on the amount used. [Chemical 3] [Chemical 4]

The polyimide precursor of the present invention may contain, preferably 50 mol% to 97 mol%, more preferably 70 mol% to 97 mol%, represented by formula (5) in the polyimide precursor. structural unit. Similarly, the polyimide obtained by imidizing the present polyimide precursor may also contain preferably 50 mol% to 97 mol%, and more preferably 70 mol% in the polyimide. ~97 mol% of the structural unit represented by formula (6).

The polyimide precursor of the present invention can be obtained by reacting a diamine containing one or two selected from TFMB or m-TB and a tetracarboxylic dianhydride containing CBDA. It is preferable that TFMB or m-TB accounts for 50 mol% or more of all diamines. In addition, preferably 70 mol% or more of CBDA can be contained in all acid dianhydrides. Among them, it is ideal to contain not only the two components TFMB or m-TB and CBDA, but also tetracarboxylic acids other than CBDA in the range of 1 mol% to 30 mol%, preferably 1 mol% to 20 mol%. The acid dianhydride component is used as the acid dianhydride component; and/or in the range of 1 mol% to 50 mol%, preferably 1 mol% to 40 mol%, and more preferably 1 mol% to 30 mol%. A diamine component other than TFMB or m-TB is included as the diamine component. If it is within this range, it is preferable because the light transmittance at 308 nm of the polyimide obtained by imidizing the polyimide precursor is reduced and the peelability (laser peeling characteristics) is improved. When a diamine component other than TFMB or m-TB is contained, a polyimide obtained by imidizing a polyimide precursor by simultaneously containing a tetracarboxylic dianhydride component other than CBDA is The light transmittance at 308 nm is low, the light transmittance at 400 nm is high, and the CTE becomes low, so they are more preferable.

Diamines other than TFMB or m-TB that can be used for copolymerization are compounds represented by H ₂ N-Ar ¹ -N ₂ H. As Ar ¹ , an aromatic diamine residue represented by the following formula (7) is preferably exemplified. base. It corresponds to Y in the formula (1) and formula (2). [Chemistry 5]

Among the diamines, 5-amino-2-(4-aminophenyl)benzimidazole (AAPBZI) or 5-amino-2-(4-aminophenyl)benzoxazole (AAPBZO) can be exemplified as preferred of diamine.

When the diamine component other than TFMB or m-TB is used in combination, the usage ratio is preferably 1 mol% to 50 mol%, and more preferably 1 mol% to 30 mol% based on all diamines. Ear%.

Tetracarboxylic dianhydrides other than CBDA that can be used for copolymerization are compounds represented by the following formula (8), [Chemical 6] As Ar ² , a tetracarboxylic dianhydride residue represented by the following formula (9) is preferably exemplified. This corresponds to X in the formulas (1) and (2). [Chemical 7]

Among the tetracarboxylic dianhydrides, those derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), pyromellitic dianhydride (PMDA), or 2,2'- The structural unit of bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride (6FDA) is used as a preferred structural unit.

When the tetracarboxylic dianhydride component other than CBDA is used in combination, the usage ratio is 1 mol% to 30 mol%, preferably 1 mol% to 28 mole, based on all the tetracarboxylic dianhydride. %, more preferably 1 mol% to 20 mol%, still more preferably 1 mol% to 10 mol%.

Furthermore, in the description of the structural unit, terms such as a structural unit derived from a diamine or a structural unit derived from an acid dianhydride are used, but this is for convenience. As long as it can provide formula (1), formula ( 2) The structural units shown in etc. are sufficient, and the raw materials or manufacturing conditions are not limited. Specifically, in Formula (1) and Formula (2), the structural unit derived from acid dianhydride is interpreted as X, and the structural unit derived from diamine is interpreted as Y, and should not be interpreted to mean raw materials or manufacturing Law. Moreover, the structural units and their proportions of the polyimide precursor depend on the type and usage ratio of the diamine and the acid dianhydride. Therefore, the description of the structural units can be explained by the diamine and the acid dianhydride. The usage ratio of the diamine and the acid dianhydride is set to the existence ratio of the structural units respectively derived from the diamine and the acid dianhydride. For example, the usage ratio (mol %) of CBDA in all acid dianhydrides becomes the content (mol %) of structural units derived from CBDA among all structural units derived from acid dianhydrides. The same is true for the content (mol%) of the structural units derived from TFMB among all the structural units derived from the diamine.

The polyimide precursor and polyimide of the present invention can use the following method known as a normal production method: a polyimide precursor (also known as Polyamic acid (polyamic acid or polyamide acid) is formed by dehydration and ring-closing reaction to form polyimide.

In the present invention, examples of the tetracarboxylic dianhydride that can be used in combination with CBDA include those described above, and further examples include: naphthalene-2,3,6,7-tetracarboxylic dianhydride, naphthalene -1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3',4,4'-biphenyl Tetracarboxylic dianhydride, 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 2,3, 3',4'-benzophenone tetracarboxylic dianhydride, naphthalene-1,2,4,5-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, 4, 8-Dimethyl-1,2,3,5,6,7-hexahydronaphthalene-1,2,5,6-tetracarboxylic dianhydride, 4,8-dimethyl-1,2,3, 5,6,7-Hexahydronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,6-dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,7- Dichloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 2,3,6,7-tetrachloronaphthalene-1,4,5,8-tetracarboxylic dianhydride, 1,4,5, 8-Tetrachloronaphthalene-2,3,6,7-tetracarboxylic dianhydride, 2,2',3,3'-biphenyl tetracarboxylic dianhydride, 2,3,3',4'-biphenyl Tetracarboxylic dianhydride, 3,3'',4,4''-p-terphenyltetracarboxylic dianhydride, 2,2'',3,3''-p-terphenyltetracarboxylic dianhydride, 2, 3,3'',4''-p-terphenyltetracarboxylic dianhydride, 2,2-bis(2,3-dicarboxyphenyl)-propane dianhydride, 2,2-bis(3,4-di Carboxyphenyl)-propane dianhydride, bis(2,3-dicarboxyphenyl)ether dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, bis(3,4-dicarboxyphenyl) Methane dianhydride, bis(2,3-dicarboxyphenyl)sebane dianhydride, bis(3,4-dicarboxyphenyl)sebane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane Alkane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, perylene-2,3,8,9-tetracarboxylic dianhydride, perylene-3,4,9,10- Tetracarboxylic dianhydride, perylene-4,5,10,11-tetracarboxylic dianhydride, perylene-5,6,11,12-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic Acid dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,9,10-tetracarboxylic dianhydride, cyclopentane-1,2,3,4-tetracarboxylic acid Acid dianhydride, pyrazine-2,3,5,6-tetracarboxylic dianhydride, pyrrolidine-2,3,4,5-tetracarboxylic dianhydride, thiophene-2,3,4,5-tetracarboxylic acid Acid dianhydride, 4,4'-oxydiphthalic dianhydride, (trifluoromethyl) pyromellitic dianhydride, bis(trifluoromethyl)pyromellitic dianhydride, bis(heptafluoromethyl) Propyl) pyromellitic dianhydride, pentafluoroethyl pyromellitic dianhydride, bis{3,5-di(trifluoromethyl)phenoxy}pyromellitic dianhydride, 2,2-bis (3,4-Dicarboxyphenyl)hexafluoropropane dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 2,2' ,5,5'-tetrakis(trifluoromethyl)-3,3',4,4'-tetracarboxybiphenyl dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4 ,4'-tetracarboxydiphenyl ether dianhydride, 5,5'-bis(trifluoromethyl)-3,3',4,4'-tetracarboxybenzophenone dianhydride, bis{(trifluoromethyl) Methyl)dicarboxyphenoxy}phthalic anhydride, bis{(trifluoromethyl)dicarboxyphenoxy}trifluoromethylphthalic anhydride, bis(dicarboxyphenoxy)trifluoromethylphthalic anhydride , bis(dicarboxyphenoxy)bis(trifluoromethyl)phthalic anhydride, bis(dicarboxyphenoxy)tetrakis(trifluoromethyl)phthalic anhydride, 2,2-bis{(4-(3 ,4-dicarboxyphenoxy)phenyl}hexafluoropropane dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy }Bis(trifluoromethyl)biphenyl dianhydride, bis{(trifluoromethyl)dicarboxyphenoxy}diphenyl ether dianhydride, bis(dicarboxyphenoxy)bis(trifluoromethyl) dianhydride Phthalic anhydride, etc.

In the present invention, examples of diamines that can be used in combination with TFMB or m-TB include those mentioned above. Further examples include: 3,3'-dimethyl-4,4'-diamino Biphenyl, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,6-dimethyl metaphenylenediamine, 2,5-dimethyl p-phenylenediamine , 2,4-diamino-1,3,5-trimethylbenzene, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-dimethylbenzene, 4, 4'-methylene-2,6-diethylaniline, 2,4-toluenediamine, m-phenylenediamine, p-phenylenediamine, 4,4'-diaminodiphenylpropane, 3,3' -Diaminodiphenylpropane, 4,4'-diaminodiphenylethane, 3,3'-diaminodiphenylethane, 4,4'-diaminodiphenylmethane, 3,3' -Diaminodiphenylmethane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide Phenyl sulfide, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenyl ether, 3,3-diaminodiphenyl sulfide Ether, 1,3-bis(3-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 4,4 '-Diaminobiphenyl, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4' -Diaminobiphenyl, 4,4'-diamino-terphenyl, 3,3'-diamino-terphenyl, bis(p-β-amino-tert-butylphenyl) ether, bis(p-β- Methyl-δ-aminopentyl)benzene, p-bis(2-methyl-4-aminopentyl)benzene, p-bis(1,1-dimethyl-5-aminopentyl)benzene, 1, 5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis(β-amino-tert-butyl)toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p- Xylene-2,5-diamine, m-xylenediamine, p-xylenediamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4 - Oxadiazole, pyrazine, etc.

The precursor of the polyimide of the present invention (polyamic acid) can be used in an organic polar solvent using diamine and acid dianhydride at a molar ratio of 0.9 to 1.1 (substantially equal molar). It is produced by a known method of polymerization. Specifically, it can be obtained by dissolving a diamine in an aprotic amide solvent such as N,N-dimethylacetamide or N-methyl-2-pyrrolidone under a nitrogen flow, and then adding acid dianhydride and allow them to react at room temperature for about 3 to 20 hours. At this time, the molecular terminals can be blocked by aromatic monoamine or aromatic monocarboxylic anhydride. Examples of the solvent include, in addition to the above, dimethylformamide, 2-butanone, diglyme, xylene, γ-butyrolactone, etc. One type or two or more types may be used in combination.

The polyimide of the present invention is obtained by imidizing the polyimide precursor of the invention. The imidization can be performed by a thermal imidization method or a chemical imidization method. Thermal imidization is carried out in the following manner: using an applicator to apply the polyimide precursor on any supporting substrate such as glass, metal, resin (polyimide film, etc.), and heating at 130°C Pre-drying is performed at the following temperature for 3 to 60 minutes, and then heat treatment is usually performed at a temperature of room temperature to about 360° C. for 30 minutes to 24 hours to remove the solvent and imidize. Chemical imidization is to add a dehydrating agent and catalyst to a polyimide precursor (also known as "polyamide acid") solution, and perform chemical dehydration at 30°C to 60°C. As a representative dehydrating agent, acetic anhydride can be exemplified, and as a catalyst, pyridine can be exemplified. In thermal imidization, if the combination of the type of acid dianhydride or diamine and the type of solvent is selected, the imidization will be completed in a relatively short time, and it can be carried out for 60 days including preheating. Heat treatment within minutes. In addition, thermal imidization and chemical imidization may be used in combination. When applying the polyimide precursor, a polyimide precursor solution in which the polyimide precursor is dissolved in a known solvent can be used for coating. In addition, regarding the thickness of the support base material, for example, about 0.02 mm to 1.0 mm can be used.

The preferred degree of polymerization of the polyimide precursor and the polyimide of the present invention can be 1,000 cP to 40,000 cP in terms of the viscosity of the polyimide precursor solution measured with an E-type viscometer, and is preferably in the range of 1,000 cP to 40,000 cP. The range is 3,000 cP to 5,000 cP. In addition, the molecular weight of the polyimide precursor can be determined by gel permeation chromatography (GPC). The preferred molecular weight range (in terms of polystyrene) of the polyimide precursor is ideally a number average molecular weight of 15,000 to 250,000, a weight average molecular weight of 30,000 to 800,000, and preferably a range of 50,000 to 300,000, but this is only a standard. Not all polyimide precursors outside the stated range cannot be used. Furthermore, the molecular weight of the polyimide is also within the same range as the molecular weight of its precursor.

Various fillers or additives may be blended with the polyimide precursor or the polyimide as necessary within a range that does not impair the object of the present invention. For example, inorganic particles such as silicon oxide, aluminum oxide, boron nitride, and aluminum nitride can be added for the purpose of improving sliding properties and thermal conductivity.

In the polyimide laminate in which a polyimide layer is formed on the surface of a support (support base material), the polyimide layer is peeled off from the support to obtain a polyimide film. The appropriate method for peeling depends on the type of the support, so a method suitable for the peeling is used. If the support is copper foil or the like, there is a method of dissolving it with acid. When the support is a resin (polyimide) film, a polyimide with a thickness of 25 μm or more and a heat resistance of 400°C or more is suitable. When the support contains a transparent material such as a glass substrate, a laser lift-off (LLO) method is suitable. In the LLO method, laser light is irradiated from the glass substrate side. If the laser light has a wavelength in the ultraviolet region, preferably in the near-ultraviolet region around 308 nm, it can be efficiently absorbed by the polyimide film obtained in the present invention to generate heat, and at the same time, the glass substrate and the polyimide layer can be A gap is created between them to facilitate or enable peeling. In addition, the polyimide film obtained by the production method of the present invention may not only be a single layer, but may also contain multiple layers of polyimide.

The polyimide of the present invention can form a thin polyimide layer (film) on a support base material, thereby achieving excellent transparency, dimensional stability, heat resistance, and easy peelability of the self-supporting base material. Transparent polyimide membrane with excellent performance. That is, the light transmittance under 400 nm light is 70% or more, preferably 80% or more, and the thermal expansion coefficient (CTE) is 45 ppm/K or less, preferably 35 ppm/K or less, and more preferably 30 ppm/K or less. , which can be easily peeled off from the supporting base material using known methods. In particular, the polyimide of the present invention has a light transmittance of 5% or less, preferably 3% or less, in the wavelength range of laser light (for example, 308 nm), and unlike the glass substrate supporting the base material, it can absorb laser light. It does not transmit light, so it is easily peeled off at the interface with the supporting base material (glass substrate), and excellent peelability (laser peeling: LLO) of the self-supporting base material caused by irradiation of laser light is obtained. , a thin transparent polyimide film with a thickness of preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less is preferred.

Here, when the polyimide of the present invention is used as a polyimide film, preferably when it is used for a flexible device, and more preferably when it is used as a device provided on a polyimide film. In the case of a polyimide film with a functional layer having a functional layer, unless otherwise specified, the light transmittance is a value obtained by measuring the film. In a preferred embodiment, the light transmittance is a value measured in a film state with a thickness of 10 μm to 15 μm, as long as the transmittance can be provided in any of the thickness ranges. . In a more preferred embodiment, the light transmittance is a value measured in a film state with a thickness of 13 μm. In this case, the value obtained by converting the value measured in a film state with a thickness of about 13 μm into a film of 13 μm may be used.

Unless otherwise specified, the coefficient of thermal expansion (CTE) is the linear expansion coefficient when changing from 250°C to 100°C. The difference in thermal expansion coefficient (10 ppm/K or less) between the polyimide of the present invention and glass is not large. , so when glass is used as the supporting base material, the shape stability is excellent. For example, when manufacturing flexible devices such as functional layer laminates in TFT substrates for organic EL devices, touch screen substrates, color filters, etc., which have bottom-emitting structures or top-emitting structures, the warpage of the substrates can be suppressed. , the manufacturing yield of flexible devices is excellent. Moreover, it can absorb light in the invisible light region and increase the transmittance in the visible light region. Within the above range, it is possible to absorb 308 nm laser light (excimer laser) while maintaining transparency in the visible light region. As a result, it is possible to irradiate flexible substrates such as organic EL device substrates, touch screen substrates, color filter substrates, etc. with laser without causing damage to the display device on the transparent polyimide layer. The imine layer (film) is peeled off from the glass and can be preferably produced using a laser lift-off method. The yellowness (YI) may be 6 or less, preferably 4 or less. If it is within the above range, it can be preferably used for substrates that require transparency or are colorless, such as TFT substrates for organic EL devices, touch screen substrates, and color filter substrates. In addition, from the viewpoint of heat resistance, the glass transition temperature is 300°C or higher, preferably 350°C or higher, more preferably 380°C or higher, and the thermal decomposition temperature (Td1) is 350°C or higher, preferably 380°C or higher.

Furthermore, since the polyimide of the present invention is obtained by dehydrating and ring-closing the polyimide precursor to undergo imidization, the arrangement of the structural units is maintained the same. Furthermore, when the polyimide precursor of the present invention is formed into a polyimide, the characteristics such as light transmittance and thermal expansion coefficient satisfy the above and are the same.

The polyimide film obtained by using the polyimide (precursor) of the present invention can be preferably used as a replacement for the glass substrate that is an existing material in thin displays or touch screen applications, and satisfies dimensional stability. Practical flexible heat-resistant transparent resin substrate material with required properties. That is, a polyimide film can be used as a substrate material, and functional layers such as elements having various functions can be formed on the surface. For example, not only main display devices such as liquid crystal display devices, organic EL display devices, touch screens, and electronic paper can be formed, but also components related to them, such as thin film transistors (TFTs), color filters, etc. Optical sheets, conductive films, gas barrier films, flexible circuit substrates, adhesive films, etc.

In this case, the polyimide film may not only be a single layer, but may also contain multiple layers of polyimide.

In addition, the formation method of the functional layer can appropriately set the formation conditions according to the target device. Generally, a metal film, an inorganic film, an organic film, etc. can be formed on a polyimide film and then patterned into a predetermined shape if necessary, or Obtained by known methods such as heat treatment. That is, there is no particular limitation on the means used to form the display element. For example, sputtering, evaporation, chemical vapor deposition (CVD), printing, exposure, dipping, etc. can be appropriately selected. If necessary, The process can also be performed in a vacuum chamber or the like. Furthermore, after the functional layer is formed on the polyimide film, the separation of the supporting base material and the polyimide film with the functional layer may be performed immediately after the functional layer is formed through various processes, or may be performed within a certain period of time. The inner part is kept integrally with the supporting base material and is separated and removed immediately before use as a display device, for example.

After the polyimide layer (film) formed on the supporting base material using the polyimide (precursor) of the present invention is further formed with a functional layer thereon, the self-supporting base material combines the polyimide film with the function. The layers peel off together. For example, after the assembly and manufacturing steps of various electronic components in which a functional layer is formed on a polyimide film are completed, the polyimide film with the functional layer on the obtained support base material is irradiated with laser light, whereby the functional layer is The polyimide layer (film) is peeled off from the supporting substrate. As mentioned above, if an excimer laser (wavelength 308 nm) is used to irradiate the interface between the supporting substrate (glass) and the polyimide film, the polyimide film with the functional layer can be easily self-supported. Material peeling.

Furthermore, if the polyimide film stretches when the polyimide film is peeled off together with the functional layer from the supporting base material, retardation becomes larger. Therefore, it is preferable to peel the polyimide film so that the stress applied to the polyimide film during peeling is reduced. In order to prevent the polyimide film from extending, it is preferable to form an anti-extension layer of an adhesive or the like on a supporting base material, form a polyimide layer (film) thereon, and then form a function thereon. layer, and then peel off the polyimide film together with the anti-stretch layer and the functional layer, thereby distributing the stress required for peeling to the other layers.

The method for producing a transparent polyimide film of the present invention is to coat a polyimide precursor on a support (support base material) and perform imidization to form a polyimide layer, and then add the polyimide precursor to the support (support base material) to form a polyimide layer. It is preferable that the amine layer is peeled from the supporting base material to produce a polyimide film having a thickness of preferably 30 μm or less, more preferably 20 μm or less, and even more preferably 15 μm or less that can be used as a transparent resin substrate material.

[Examples] Hereinafter, the present invention will be specifically described based on Examples and Comparative Examples. Furthermore, the present invention is not limited to the above-described embodiments.

The codes of raw materials used in Examples etc. are shown below. ･TFMB: 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl･m-TB: 2,2'-dimethyl-4,4'-diaminobiphenyl･4 ,4'-DAPE: 4,4'-diaminodiphenyl ether･AAPBZI: 5-amino-2-(4-aminophenyl)benzimidazole･AAPBZO: 5-amino-2-(4-aminobenzene Benzoxazole･CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride･PMDA: Pyromellitic acid dianhydride･BPDA: 3,3',4,4'-biphenyltetracarboxylic acid Carboxylic dianhydride･6FDA: 2,2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride･NMP: N-methyl-2-pyrrolidone

The measurement method and evaluation method of each physical property in Examples etc. are shown below. [Light transmittance and yellowness (YI)] Use a SHIMADZU UV-3600 spectrophotometer to determine the 308 nm, 355 nm, and Light transmittance at 400 nm and 430 nm (T308, T355, T400, T430). In addition, YI (yellowness) was calculated based on the following calculation formula. YI=100×(1.2879X-1.0592Z)/Y X, Y, and Z are the tristimulus values of the test piece, which are specified in Japanese Industrial Standard (JIS) Z 8722.

[Coefficient of thermal expansion (CTE)] A thermomechanical analysis (TMA) device was used to apply a load of 5.0 g to a polyimide film of 3 mm × 15 mm size at a certain temperature rising rate (10°C/min). ) The temperature was raised from 30°C to 280°C, and then cooled from 250°C to 100°C, and the thermal expansion coefficient was measured based on the elongation (linear expansion) of the polyimide film during cooling.

[Glass transition temperature (Tg)] Use a dynamic thermomechanical analysis device to measure the dynamic viscoelasticity of a polyimide film (5 mm × 70 mm) when the temperature is raised from 23°C to 500°C at 5°C/min, and calculate the glass Transfer temperature (tan δ maximum value: ℃).

[Thermal decomposition temperature (Td1)] In a nitrogen atmosphere, a polyimide film weighing 10 mg to 20 mg was measured using a thermogravimetric (TG) device TG/DTA6200 manufactured by SEIKO. The weight change when the temperature is raised from 30°C to 550°C, the weight at 200°C is set to zero, and the temperature at which the weight reduction rate is 1% is set as the thermal decomposition temperature (Td1).

[Peelability: LED] This is the laser irradiation energy density (mJ/cm ² ) (code name: LED) until the polyimide layer and the supporting base material (glass substrate) can be peeled off. The irradiation conditions are the same as "Peelability: Laser Liftoff (LLO)" described in the following paragraph. The higher the energy density, the more difficult it is to peel off. In consideration of the life of the laser irradiation device, it is preferable that the irradiation energy density is small. The upper limit of measurement is 300 mJ/cm ² , and those that cannot be peeled off at 300 mJ/cm ² or less are marked as “×”.

[Peelability: Laser peeling (LLO)] Use an excimer laser processing machine (wavelength 308 nm) to support the base material (glass) side irradiation beam size 14 mm × 1.2 mm, moving speed 6 mm/s, overlap Use a laser with a rate of 80%, and set the state in which the support base material and the polyimide layer are completely separated (the peeling range is determined by the cutting knife, and the polyimide film naturally peels off from the glass after one round of incision) is set to "○ ”, the state in which the support base material and the polyimide layer cannot be separated entirely or partially, or the polyimide layer is discolored, is regarded as “×”.

Example 1 Under nitrogen flow, 9.17 g of TFMB was dissolved in 85 g of NMP in a 100 ml separable flask. Next, 5.00 g of CBDA was added to the solution. After stirring for 10 minutes, 0.83 g of BPDA was added. Furthermore, the molar ratio of the diamine component and the tetracarboxylic dianhydride component was set to 0.99 (substantially equal molar). Thereafter, the solution was continuously stirred at room temperature for 24 hours to proceed with the polymerization reaction, and polyamide A (a viscous, colorless solution) with a high degree of polymerization (Mw above 80,000, viscosity above 3,000 cP) was obtained.

Example 2 to Example 9, Comparative Example 1 to Comparative Example 7 Polymer was prepared in the same manner as in Example 1, except that the diamine and tetracarboxylic dianhydride as raw materials were changed to the compositions shown in Table 1 and Table 2. Amino acid solution to obtain polyamic acid B ~ polyamic acid P. In addition, in Table 1 and Table 2, the unit of the amount of diamine and tetracarboxylic dianhydride is g, and the numerical value in parentheses represents mol% in the diamine component or the tetracarboxylic dianhydride component.

[Table 1]

[Table 2]

Example 10 The solvent NMP was added to the polyimide precursor solution A obtained in Example 1 and diluted so that the viscosity became 4000 cP. Then, using a spin coater, the thickness of the polyimide after hardening was It is coated on a glass substrate (E-XG manufactured by Corning, size = 150 mm × 150 mm, thickness = 0.7 mm) with a thickness of about 15 μm. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen atmosphere, the temperature was raised from room temperature to 300°C (360°C in Comparative Example 10) at a certain heating rate (3°C/min), and maintained at 130°C for 10 minutes to form 150°C on the glass substrate. mm×150 mm polyimide layer (polyimide A), and polyimide laminate A was obtained.

Examples 11 to 18 and Comparative Examples 8 to 14 were the same as those in Example 10, except that the polyimide precursor was changed to any one of polyimide precursor B to polyimide precursor P. The operations are carried out in the same manner to obtain polyimide laminated bodies B to polyimide laminated bodies P. The polyimide precursor and the polyimide laminated body correspond to the symbols, which means that the polyimide laminated body B is obtained from the polyimide precursor B. The same applies to the symbol C and subsequent symbols.

Regarding the obtained polyimide laminates A to polyimide laminates P, laser lift-off (LLO) and LED were measured. The results are shown in Table 3 and Table 4.

Various physical properties other than those mentioned above were measured by peeling off the polyimide film from the laminated body. In this case, the laminated body used a 75 μm polyimide film as the substrate instead of the glass substrate. Made as described above. Detailed production conditions are shown below. The solvent NMP was added to the polyamic acid solutions A to the polyamic acid solutions P obtained in Examples 1 to 9 and Comparative Examples 1 to 7 and diluted so that the viscosity became 3000 cP, and then coated Apply to 75 μm polyimide membrane (Upilex-S) substrate. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen environment, the temperature was raised from room temperature to 300°C (360°C in Comparative Example 10) at a certain heating rate (3°C/min), and maintained at 130°C for 10 minutes to obtain a polyimide laminate. membrane. Then, the polyimide base material (Upilex-S) is peeled off to form a monomer form in which the polyimide solution A to the polyimide solution P are imidized. Polyimide film A ~ Polyimide film P. The peeling is performed in the following manner: using a cutting knife to cut only one circle of incisions in the formed polyimide layer to determine the range for peeling, and then peeling it off from the base material using tweezers. In addition, the thickness of these films is shown in the thickness item of Table 3 and Table 4.

Regarding the obtained polyimide films A to polyimide films P, various evaluations such as CTE, light transmittance, YI, Td1, and Tg were performed. The results are shown in Table 3 and Table 4.

[table 3]

[Table 4]

Synthesis Example 1 In order to synthesize a polyimide precursor, 8.57 g of TFMB was dissolved in 85 g of NMP in a 100 ml separable flask under nitrogen flow. Next, 0.67 g of AAPBZI was added to the solution. After stirring for 10 minutes, add 5.76 g of CBDA. Furthermore, the molar ratio of the diamine component and the tetracarboxylic dianhydride component was set to 0.99 (substantially equal molar). Thereafter, the solution was continuously stirred at room temperature for 24 hours to proceed with the polymerization reaction, and polyamide A (viscous, colorless solution) with a high degree of polymerization (Mw above 80,000, viscosity above 5,000 cP) was obtained.

Synthesis Example 2 to Synthesis Example 18 A polyamic acid solution was prepared in the same manner as in Synthesis Example 1, except that the diamine and tetracarboxylic dianhydride were changed to the compositions shown in Table 5 and Table 6, to obtain polyamic acid B to Polyamide R. In addition, in Tables 5 and 6, the unit of the amount of diamine and tetracarboxylic dianhydride is g, and the numerical value in the parentheses represents mol% in the diamine component or the tetracarboxylic dianhydride component.

[table 5]

[Table 6]

Example 19 The solvent NMP was added to the polyimide precursor solution A obtained in Synthesis Example 1 and diluted so that the viscosity became 4000 cP. Then, a spin coater was used to obtain a thickness of the polyimide after hardening. It is coated on a glass substrate (E-XG manufactured by Corning, size = 150 mm × 150 mm, thickness = 0.7 mm) with a thickness of about 15 μm. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen environment, the temperature was raised from room temperature to 300°C (360°C in Comparative Example 18) at a certain heating rate (3°C/min), and maintained at 130°C for 10 minutes to form 150°C on the glass substrate. mm×150 mm polyimide layer (polyimide A), and polyimide laminate A was obtained.

Examples 20 to 29 and Comparative Examples 15 to 21 are the same as those in Examples, except that polyimide precursor A is replaced by any one of polyimide precursor B to polyimide precursor R. 19 The same operation was performed to obtain polyimide laminates B to polyimide laminates R. The polyimide precursor and the polyimide laminated body correspond to the symbols, which means that the polyimide laminated body B is obtained from the polyimide precursor B. The same applies to the symbol C and subsequent symbols.

About the obtained polyimide laminated bodies A to polyimide laminated bodies R, laser lift-off (LLO) and LED were measured. The results are shown in Table 7 and Table 8.

Measurements other than the above were performed by peeling off the polyimide film from the laminate. In this case, the laminate used a 75 μm polyimide film as the substrate instead of the glass substrate. Otherwise, the above was followed. Made as described. Detailed production conditions are shown below. The solvent NMP was added to the polyamic acid solutions A to the polyamic acid solutions R obtained in Synthesis Examples 1 to 18, diluted so that the viscosity became 3000 cP, and then coated on a 75 μm polyamide layer. Amine film (Upilex-S) substrate. Next, heating was performed at 100° C. for 15 minutes. Then, in a nitrogen environment, the temperature was raised from room temperature to 300°C (360°C in Comparative Example 18) at a certain heating rate (3°C/min), and maintained at 130°C for 10 minutes to obtain a polyimide laminate. membrane. Then, the polyimide base material (Upilex-S) is peeled off to obtain a monomer form in which the polyimide solution A to the polyimide solution R are imidized. Polyimide film A ~ Polyimide film R. The peeling is performed in the following manner: using a cutting knife to cut only one circle of incisions in the formed polyimide layer to determine the range for peeling, and then peeling it off from the base material using tweezers. Furthermore, the thickness of these films is shown in the thickness column.

Regarding the obtained polyimide films A to polyimide films R, various evaluations such as CTE, light transmittance, YI, Td1 and Tg were performed respectively. The results are shown in Table 7 and Table 8.

[Table 7]

[Table 8]

without

without

Claims (11)

A polyimide precursor, which has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride. The polyimide precursor is characterized in that: it has a structural unit derived from 2,2'-bis(trifluoro Structural units of methyl)-4,4'-diaminobiphenyl and structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and in all structural units derived from acid dianhydride Containing more than 70 mol% of structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride, the polyimide precursor is imidized to form a polyimide The light transmittance of amine is less than 5% at 308nm and more than 70% at 400nm, and the thermal expansion coefficient is less than 45ppm/K, derived from 2,2'-bis(trifluoromethyl)-4,4' - The structural unit of diaminobiphenyl and the structural unit derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride constitute the structural unit represented by formula (5):

Among all the structural units derived from diamines, more than 50 mol% of the structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl are included. The structural units of the diamine contain 1 mol% to 50 mol% of structural units derived from diamines other than 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, or Contains 1 mol% to 15 mol% of structural units derived from acid dianhydrides other than 1,2,3,4-cyclobutanetetracarboxylic dianhydride among all structural units derived from acid dianhydride, source The structural unit of diamines other than 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl is derived from 2,2'-dimethyl-4,4'-diaminobiphenyl. Benzene or a compound represented by H ₂ N-Ar ¹ -N ₂ H, where Ar ¹ is an aromatic diamine residue represented by formula (7):

The structural unit derived from acid dianhydride is further a structural unit derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride, a structural unit derived from pyromellitic dianhydride or derived from 2, Structural unit of 2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. The polyimide precursor as described in item 1 of the patent application, wherein the structural units derived from diamine also include structural units derived from 2,2'-dimethyl-4,4'-diaminobiphenyl . A polyimide, characterized in that: the polyimide precursor described in item 1 or 2 of the patent application is obtained by imidization. A polyimide has a structural unit derived from a diamine and a structural unit derived from an acid dianhydride. The polyimide is characterized in that: it has a structural unit derived from 2,2'-bis(trifluoromethyl)- Structural units of 4,4'-diaminobiphenyl and structural units derived from 1,2,3,4-cyclobutane tetracarboxylic dianhydride, and all structural units derived from acid dianhydride contain 70 mol Ear% or more of structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride; and the light transmittance is less than 5% at 308nm, more than 70% at 400nm, and the thermal expansion coefficient is 45ppm/K or less, structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 1,2,3,4-cyclobutanetetracarboxylic acid di The structural unit of anhydride constitutes the structural unit represented by formula (5):

Among all the structural units derived from diamines, more than 50 mol% of the structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl are included. The structural units of the diamine contain 1 mol% to 50 mol% of structural units derived from diamines other than 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, or Among all structural units derived from acid dianhydride, 1 mol % to 15 mol % of structural units derived from acid dianhydride other than 1,2,3,4-cyclobutane tetracarboxylic dianhydride, source The structural unit of diamines other than 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl is derived from 2,2'-dimethyl-4,4'-diaminobiphenyl. Benzene or a compound represented by H ₂ N-Ar ¹ -N ₂ H, where Ar ¹ is an aromatic diamine residue represented by formula (7):

The structural unit derived from acid dianhydride is further a structural unit derived from 3,3',4,4'-biphenyltetracarboxylic dianhydride, a structural unit derived from pyromellitic dianhydride or derived from 2, Structural unit of 2'-bis(3,4-dicarboxyphenyl)hexafluoropropane dianhydride. For example, the polyimide described in item 4 of the patent application has a yellowness of 6 or less. The polyimide described in item 4 of the patent application, wherein the polyimide is used as a transparent resin substrate material. A method for manufacturing a transparent polyimide film, comprising: coating a polyimide precursor or a resin solution thereof on the surface of a support; and heating the polyimide precursor or a resin solution thereof. The step of performing imidization to form a polyimide layer on the surface of a support; and the step of peeling off the polyimide layer from the support to obtain a polyimide film, the polyimide film The method for manufacturing a acyl imine membrane is characterized in that the polyimide precursor is selected from the group consisting of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 2,2 It is obtained by reacting one or two diamines in '-dimethyl-4,4'-diaminobiphenyl with an acid dianhydride containing 1,2,3,4-cyclobutanetetracarboxylic dianhydride, Composed of structural units derived from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and structural units derived from 1,2,3,4-cyclobutanetetracarboxylic dianhydride The structural unit represented by formula (5):

; And the thermal expansion coefficient of the polyimide film is less than 45 ppm/K, the light transmittance is less than 5% under 308nm light, and is more than 70% under 400nm light, wherein all diamines contain 50 moles More than 1% of diamines selected from 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl and 2,2'-dimethyl-4,4'-diaminobiphenyl , and contains more than 70 mol% of 1,2,3,4-cyclobutanetetracarboxylic dianhydride in all acid dianhydrides, and contains 1 to 50 mol% of all diamines except 2 , diamines other than 2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl or 2,2'-dimethyl-4,4'-diaminobiphenyl, or in all acid diamines The anhydride contains 1 mol% to 15 mol% of acid dianhydrides other than 1,2,3,4-cyclobutanetetracarboxylic dianhydride, derived from 2,2'-bis(trifluoromethyl)- The structural unit of diamines other than 4,4'-diaminobiphenyl is derived from 2,2'-dimethyl-4,4'-diaminobiphenyl or represented by H ₂ N-Ar ¹ -N ₂ H A compound, wherein Ar ¹ is an aromatic diamine residue represented by formula (7):

All acid dianhydrides further include 3,3',4,4'-biphenyltetracarboxylic dianhydride, pyromellitic dianhydride or 2,2'-bis(3,4-dicarboxyphenyl)hexa Fluoropropane dianhydride. The method for manufacturing a transparent polyimide film as described in Item 7 of the patent application, wherein the yellowness is 6 or less. The method for manufacturing a transparent polyimide film as described in claim 7, wherein the interface between the polyimide layer and the support is irradiated with laser light to peel the polyimide layer from the support. A method for manufacturing a transparent polyimide film with a functional layer, characterized in that: the transparent polyimide film as described in any one of items 7 to 9 of the patent application scope The method for producing an imine film includes the step of forming a functional layer on the polyimide layer and then peeling the polyimide layer with the functional layer from the support. The method for manufacturing a transparent polyimide film with a functional layer as described in item 10 of the patent application, wherein the functional layer is selected from the group consisting of a transparent conductive layer, a wiring layer, a conductive layer, a gas barrier layer, and a thin film. Any one or two or more layers from the group consisting of a transistor, an electrode layer, a light-emitting layer, an adhesive layer, an adhesive layer, a transparent resin layer, a color filter resist, and a hard coat layer.