JP7694389B2 - Laminate - Google Patents

Description

The present invention relates to a laminate including a self-repairing layer and a polyimide film. More specifically, the present invention relates to a laminate including a polyimide film that exhibits excellent transparency, self-repairing properties, and flexibility, and has excellent adhesion to the self-repairing layer.

Conventionally, hard coat films in which a hard coat layer is provided on a transparent substrate film have been used for the front panels and around the electrodes of image display devices such as touch panels and displays in order to provide scratch resistance so that the visibility is not reduced due to scratches during handling (Patent Document 1). On the other hand, in recent years, touch panels and displays with foldable image display areas have been proposed in order to provide high portability and large screens (Patent Document 2), and hard coat films are now required to have greater flexibility than before.

The hard coat layer provided on the hard coat film has a high surface hardness to provide scratch resistance, but a coat layer with high surface hardness tends to be brittle, making it difficult to achieve both high surface hardness and excellent flexibility. As a result, as an alternative to the hard coat layer, a film has been proposed in which a flexible and strong coat layer is formed, and a self-healing coat layer is provided that has the function of spontaneously eliminating deformations and scratches caused by stress during handling or processing (Patent Document 3).

The substrate film used in such self-repairing films is generally a transparent thermoplastic resin film made of polyethylene terephthalate (PET), acrylic, polycarbonate (PC), triacetyl cellulose (TAC), polyolefin, etc. These thermoplastic resin films have excellent transparency and bending resistance, and are easy to bond and process, so they also have excellent adhesion to the self-repairing coating layer (Patent Document 4).

Meanwhile, technological developments have been made to form functional elements such as electrodes and display elements directly on substrate films, and attempts have been made to use polyimide films, which have heat and chemical resistance, instead of typical thermoplastic resin films as substrate films for hard coat films (Patent Documents 5 to 6).

JP 2013-37323 A JP 2019-211778 A Special Publication No. 2016-516846 JP 2016-147416 A JP 2019-51644 A JP 2019-105829 A

In order to directly form functional elements such as electrodes and display elements, the substrate film is required to have a high tensile modulus, a low CTE, and heat and chemical resistance. When attempting to use a polyimide film suitable for such substrate films as the substrate film for a self-repairing film with excellent flexibility and flex resistance as exemplified in Patent Document 4, the surface of the polyimide film is flat and has low activity, resulting in insufficient adhesion to the polyimide film, and the coating layer is prone to peeling or falling off during processing or when flexed.

On the other hand, the self-repairing layer has the function of absorbing external forces caused during handling or processing and repairing deformations and scratches, and since it is provided on the front surface of the image display device, it is necessary for it to have low tackiness, antifouling properties, and chemical resistance, and therefore a high degree of crosslinking and a compositionally low activity component are used. Therefore, the easy-adhesion layer exemplified in Patent Document 5 for hard coat layers has insufficient adhesion to the self-repairing layer, and the self-repairing layer is prone to peeling or falling off during the processing process or when bending.

Because both the polyimide film and the self-healing layer have low activity, the challenge was to achieve adhesion between the self-healing layer and the polyimide film while exhibiting excellent transparency, self-healing properties, and flexibility.

As a result of intensive research into solving the above problems, the inventors discovered that such problems could be solved and arrived at the present invention. That is, the present invention has the following configuration.

A laminate comprising a polyimide film having a tensile modulus of elasticity of 3 GPa or more in both the MD and TD directions, a CTE of -5 ppm/°C to +55 ppm/°C in both the MD and TD directions, and a solvent content of 0.5 to 5.0 mass%, and a self-repairing layer formed on at least one surface of the polyimide film.

The laminate preferably has a return rate of 80% or more after applying a minute load of 0.5 mN to the surface from a Vickers square pyramid diamond indenter and holding it for 5 seconds, then removing the load to 0.005 mN and holding it for 60 seconds. The laminate also preferably has an adhesion rate of 80% or more of the self-repairing layer cut into a lattice shape to the polyimide film according to the cross-cut method of JIS K 5600-5-6 (1999). The laminate also preferably has a yellow index of 10 or less, a light transmittance of 70% or more at a wavelength of 400 nm, and a total light transmittance of 85% or more. The self-repairing layer is preferably a polymer composition containing cross-linking points, and some or all of the cross-linking points are movable cross-linking points.

According to the present invention, even when a polyimide film having a low activity surface is used as a substrate film, it is possible to provide a laminate that exhibits excellent self-repairing properties while having excellent adhesion to a self-repairing layer. In addition, because it has excellent transparency and flexibility, it is possible to provide a transparent laminate that is suitable for the front panel and the periphery of electrodes of image display devices such as touch panels and displays whose image display portions are foldable.

Hereinafter, a laminate according to an embodiment of the present invention will be described. The laminate according to the present invention is a laminate including a polyimide film and a self-repairing layer formed on at least one surface of the polyimide film. The polyimide film constituting the laminate according to the present invention is a polymer film having an imide bond in the main chain, and is preferably a polyimide film or a polyamideimide film, and more preferably a polyimide film.

The polyimide film of the present invention is preferably obtained by any of the following manufacturing methods. First, in the first method, a polyamic acid (polyimide precursor) solution obtained by polymerizing diamines and tetracarboxylic acids in a solvent is applied to a support for preparing a polyimide film, dried to form a green film (also called a "precursor film," "polyamic acid film," or "polyamic acid film"). The green film is then subjected to high-temperature heat treatment on the support for preparing a polyimide film or in a state where it is peeled off from the support to cause a dehydration ring-closing polymerization reaction. In the second method, a polyimide solution obtained by a dehydration ring-closing polymerization reaction between diamines and tetracarboxylic acids in a solvent is applied to a support for preparing a polyimide film, dried to form a polyimide film containing 1 to 50% by mass of solvent, and the polyimide film containing 1 to 50% by mass of solvent is then subjected to high-temperature treatment and dried on the support for preparing a polyimide film or in a state where it is peeled off from the support to obtain the polyimide film.

In the third method, a polyamideimide solution obtained by polymerizing diisocyanates and tricarboxylic acids in a solvent is applied to a support for producing a polyamideimide film, and dried to form a polyamideimide film containing 1 to 50% by mass of solvent, and the polyamideimide film containing 1 to 50% by mass of solvent is then subjected to high-temperature treatment and dried on the support for producing polyamideimide or after being peeled off from the support. In the above three production methods, dicarboxylic acids can also be used as appropriate.

As the tetracarboxylic acids, tricarboxylic acids, and dicarboxylic acids, aromatic tetracarboxylic acids (including their acid anhydrides), aliphatic tetracarboxylic acids (including their acid anhydrides), alicyclic tetracarboxylic acids (including their acid anhydrides), aromatic tricarboxylic acids (including their acid anhydrides), aliphatic tricarboxylic acids (including their acid anhydrides), alicyclic tricarboxylic acids (including their acid anhydrides), aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and alicyclic dicarboxylic acids, which are commonly used in polyimide synthesis or polyamideimide synthesis, can be used. Among them, aromatic tetracarboxylic acid anhydrides or alicyclic tetracarboxylic acid anhydrides are preferred, aromatic tetracarboxylic acid anhydrides are more preferred from the viewpoint of heat resistance, and alicyclic tetracarboxylic acids are more preferred from the viewpoint of light transmittance (transparency). When the tetracarboxylic acids are acid anhydrides, the anhydride structure may be one or two in the molecule, but preferably has two anhydride structures (dianhydrides). Tetracarboxylic acids, tricarboxylic acids, and dicarboxylic acids may be used alone or in combination of two or more.

Examples of aromatic tetracarboxylic acids for obtaining the highly heat-resistant polyimide of the present invention include 4,4'-(2,2-hexafluoroisopropylidene)diphthalic acid, 4,4'-oxydiphthalic acid, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-carboxylic acid) 1,4-phenylene, bis(1,3-dioxo-1,3-dihydro-2-benzofuran-5-yl)benzene-1,4-dicarboxylate, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(benzene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 3,3',4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(toluene -2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(4-isopropyl-toluene- 2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4- dibenzene-1,2-dicarboxylic acid, 4,4'-benzophenonetetracarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis (1,4-xylene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(4-isopropyl-toluene-2,5-diyloxy)]dibenzene-1,2-dicarboxylic acid, tetracarboxylic acids such as 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]dibenzene-1,2-dicarboxylic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]dibenzene-1,2-dicarboxylic acid, and their acid anhydrides. Among these, dianhydrides having two acid anhydride structures are preferred, and in particular, 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride and 4,4'-oxydiphthalic dianhydride are preferred. The aromatic tetracarboxylic acids may be used alone or in combination of two or more. When heat resistance is important, the aromatic tetracarboxylic acids preferably account for 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

Alicyclic tetracarboxylic acids that can be used to obtain colorless and highly transparent polyimides include 1,2,3,4-cyclobutane tetracarboxylic acid, 1,2,3,4-cyclopentane tetracarboxylic acid, 3-(carboxymethyl)cyclopentane-1,2,4-tricarboxylic acid, 1,2,3,4-cyclohexane tetracarboxylic acid, 1,2,4,5-cyclohexane tetracarboxylic acid, 3,3',4,4'-bicyclohexyl tetracarboxylic acid, and bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic acid. Carboxylic acid, bicyclo[2,2,2]octane-2,3,5,6-tetracarboxylic acid, bicyclo[2,2,2]oct-7-ene-2,3,5,6-tetracarboxylic acid, tetradecahydroanthracene-2,3,6,7-tetracarboxylic acid, tetradecahydro-1,4:5,8:9,10-trimethanoanthracene-2,3,6,7-tetracarboxylic acid, decahydronaphthalene-2,3,6,7-tetracarboxylic acid, decahydro-1,4:5,8-dimethanonaphthalene-2,3,6,7-tetracarboxylic acid tetracarboxylic acid, decahydro-1,4-ethano-5,8-methanonaphthalene-2,3,6,7-tetracarboxylic acid, norbornane-2-spiro-α-cyclopentanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid (also known as norbornane-2-spiro-2'-cyclopentanone-5'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid), methylnorbornane-2-spiro-α-cyclopentanone-α'-spiro-2''- ''-(methylnorbornane)-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid (also known as "norbornane-2-spiro-2'-cyclohexanone-6'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid"), methylnorbornane-2-spiro-α-cyclohexanone-α'-spiro-2''-(methylnorbornane)-5, 5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclopropanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclobutanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cycloheptanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro -α-cyclooctanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclononanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cyclodecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-cycloundecanone-α'-spiro-2"-norbornane-5, 5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclododecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotridecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2-spiro-α-cyclotetradecanone-α'-spiro-2''-norbornane-5,5'',6,6''-tetracarboxylic acid, norbornane-2- Examples of tetracarboxylic acids include spiro-α-cyclopentadecanone-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, norbornane-2-spiro-α-(methylcyclopentanone)-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, and norbornane-2-spiro-α-(methylcyclohexanone)-α'-spiro-2"-norbornane-5,5",6,6"-tetracarboxylic acid, and acid anhydrides thereof. Among these, dianhydrides having two acid anhydride structures are preferred, and in particular, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 1,2,4,5-cyclohexanetetracarboxylic dianhydride are more preferred, and 1,2,3,4-cyclobutanetetracarboxylic dianhydride is even more preferred. These may be used alone or in combination of two or more. When transparency is important, the alicyclic tetracarboxylic acids preferably account for 50% by mass or more of the total tetracarboxylic acids, more preferably 60% by mass or more, even more preferably 70% by mass or more, and even more preferably 80% by mass or more.

Examples of tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalene tricarboxylic acid, diphenyl ether-3,3',4'-tricarboxylic acid, and diphenyl sulfone-3,3',4'-tricarboxylic acid, and hydrogenated products of the above aromatic tricarboxylic acids such as hexahydrotrimellitic acid, alkylene glycol bistrimellitates such as ethylene glycol bistrimellitate, propylene glycol bistrimellitate, 1,4-butanediol bistrimellitate, and polyethylene glycol bistrimellitate, as well as monoanhydrides and esterified products thereof. Among these, monoanhydrides having one acid anhydride structure are preferred, and in particular, trimellitic anhydride and hexahydrotrimellitic anhydride are preferred. These may be used alone or in combination.

Examples of dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, and 4,4'-oxydibenzenedicarboxylic acid, or hydrogenated products of the above aromatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, and 1,2-cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, heptanedioic acid, octanedioic acid, azelaic acid, sebacic acid, undecanediacid, dodecanedioic acid, and 2-methylsuccinic acid, as well as their acid chlorides and esters. Among these, aromatic dicarboxylic acids and their hydrogenated products are preferred, and terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenedicarboxylic acid are particularly preferred. The dicarboxylic acids may be used alone or in combination.

The diamines or isocyanates for obtaining the polyimide having high heat resistance and/or colorless transparency in the present invention are not particularly limited, and aromatic diamines, aliphatic diamines, alicyclic diamines, aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, etc., which are usually used in polyimide synthesis or polyamideimide synthesis, can be used. From the viewpoint of heat resistance, aromatic diamines or aromatic diisocyanates are preferred, and from the viewpoint of transparency, alicyclic diamines or alicyclic diisocyanates are preferred. In addition, aromatic diamines or diisocyanates having a benzoxazole structure are preferred because they can exhibit high heat resistance, high elastic modulus, low heat shrinkage, and low linear expansion coefficient. The diamines and isocyanates may be used alone or in combination of two or more.

Examples of aromatic diamines include 2,2'-dimethyl-4,4'-diaminobiphenyl, 1,4-bis[2-(4-aminophenyl)-2-propyl]benzene, 1,4-bis(4-amino-2-trifluoromethylphenoxy)benzene, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, bis[4-(3-aminophenoxy)biphenyl, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, amine, 4-amino-N-(4-aminophenyl)benzamide, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, 4,4'-diaminodiphenyl sulfoxide, 3 , 3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminobenzophenone, 3,4'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,3'-diaminodiphenyl methane, 3,4'-diaminodiphenyl methane, 4,4'-diaminodiphenyl methane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)phenyl]methane (4-phenyl)ethane, 1,2-bis[4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[4-(4-aminophenoxy)phenyl]propane, 1,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,3-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 1,1-bis[4-(4-aminophenoxy)phenyl]butane, 1,3-bis[4-( 4-aminophenoxy)phenyl]butane, 1,4-bis[4-(4-aminophenoxy)phenyl]butane, 2,2-bis[4-(4-aminophenoxy)phenyl]butane, 2,3-bis[4-(4-aminophenoxy)phenyl]butane, 2-[4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3-methylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3-methylphenyl]propane, 2-[ 4-(4-aminophenoxy)phenyl]-2-[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,4-bis(4-aminof 4,4'-bis(4-aminophenoxy)biphenyl, bis[4-(4-aminophenoxy)phenyl]ketone, bis[4-(4-aminophenoxy)phenyl]sulfide, bis[4-(4-aminophenoxy)phenyl]sulfoxide, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]ether, bis[4-(4-aminophenoxy)phenyl]ether, 1,3-bis[ 4-(4-aminophenoxy)benzoyl]benzene, 1,3-bis[4-(3-aminophenoxy)benzoyl]benzene, 1,4-bis[4-(3-aminophenoxy)benzoyl]benzene, 4,4'-bis[(3-aminophenoxy)benzoyl]benzene, 1,1-bis[4-(3-aminophenoxy)phenyl]propane, 1,3-bis[4-(3-aminophenoxy)phenyl]propane, 3,4'-diaminodiphenyl sulfide, 2,2 -bis[3-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, bis[4-(3-aminophenoxy)phenyl]methane, 1,1-bis[4-(3-aminophenoxy)phenyl]ethane, 1,2-bis[4-(3-aminophenoxy)phenyl]ethane, bis[4-(3-aminophenoxy)phenyl]sulfoxide, 4,4'-bis[3-(4-aminophenoxy)benzoyl]diphenyl ether, 4,4'- Bis[3-(3-aminophenoxy)benzoyl]diphenyl ether, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzophenone, 4,4'-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]diphenyl sulfone, bis[4-{4-(4-aminophenoxy)phenoxy}phenyl]sulfone, 1,4-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1, 3-bis[4-(4-aminophenoxy)phenoxy-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-trifluoromethylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-fluorophenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene, 1,3-bis[4-(4-amino-6-methylphenoxy)-α,α-dimethylbenzyl]benzene, cyanophenoxy)-α,α-dimethylbenzyl]benzene, 3,3'-diamino-4,4'-diphenoxybenzophenone, 4,4'-diamino-5,5'-diphenoxybenzophenone, 3,4'-diamino-4,5'-diphenoxybenzophenone, 3,3'-diamino-4-phenoxybenzophenone, 4,4'-diamino-5-phenoxybenzophenone, 3,4'-diamino-4-phenoxybenzophenone, 3,4'-diamino-5'-phenoxybenzophenone benzophenone, 3,3'-diamino-4,4'-divinylphenoxybenzophenone, 4,4'-diamino-5,5'-divinylphenoxybenzophenone, 3,4'-diamino-4,5'-divinylphenoxybenzophenone, 3,3'-diamino-4-biphenoxybenzophenone, 4,4'-diamino-5-biphenoxybenzophenone, 3,4'-diamino-4-biphenoxybenzophenone, 3,4'-diamino-5'-biphenoxybenzophenone, 1,3-bis(3-amino-4-phenoxybenzoyl)benzene, 1,4-bis(3-amino-4-phenoxybenzoyl)benzene, 1,3-bis(4-amino-5-phenoxybenzoyl)benzene, 1,4-bis(4-amino-5-phenoxybenzoyl)benzene, 1,3-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,4-bis(3-amino-4-biphenoxybenzoyl)benzene, 1,3-bis(4-amino-5-biphenoxybenzoyl)benzene Examples of the aromatic diamine include 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 1,4-bis(4-amino-5-biphenoxybenzoyl)benzene, 2,6-bis[4-(4-amino-α,α-dimethylbenzyl)phenoxy]benzonitrile, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]bisaniline, and 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline. In addition, some or all of the hydrogen atoms on the aromatic ring of the aromatic diamine may be substituted with a halogen atom, an alkyl group or alkoxyl group having 1 to 3 carbon atoms, or a cyano group, and further some or all of the hydrogen atoms of the alkyl group or alkoxyl group having 1 to 3 carbon atoms may be substituted with a halogen atom. The aromatic diamines may be used alone or in combination.

In addition, the aromatic diamines having a benzoxazole structure are not particularly limited, and examples thereof include 5-amino-2-(p-aminophenyl)benzoxazole, 6-amino-2-(p-aminophenyl)benzoxazole, 5-amino-2-(m-aminophenyl)benzoxazole, 6-amino-2-(m-aminophenyl)benzoxazole, 2,2'-p-phenylenebis(5-aminobenzoxazole), 2,2'-p-phenylenebis(6-aminobenzoxazole), 1-(5-aminobenzoxazolo)-4-(6-aminobenzoxazolo)benzene, 2,6-(4,4'- diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (4,4'-diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole, 2,6- (3,4'-diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (3,4'-diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole, 2,6- (3,3'-diaminodiphenyl) benzo [1,2-d: 5,4-d'] bisoxazole, 2,6- (3,3'-diaminodiphenyl) benzo [1,2-d: 4,5-d'] bisoxazole, and the like. Among these, 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl, 4-amino-N-(4-aminophenyl)benzamide, 4,4'-diaminodiphenylsulfone, and 3,3'-diaminobenzophenone are particularly preferred. The aromatic diamines having an oxazole structure may be used alone or in combination.

Examples of alicyclic diamines include 1,4-diaminocyclohexane, 1,4-diamino-2-methylcyclohexane, 1,4-diamino-2-ethylcyclohexane, 1,4-diamino-2-n-propylcyclohexane, 1,4-diamino-2-isopropylcyclohexane, 1,4-diamino-2-n-butylcyclohexane, 1,4-diamino-2-isobutylcyclohexane, 1,4-diamino-2-sec-butylcyclohexane, 1,4-diamino-2-tert-butylcyclohexane, 4,4'-methylenebis(2,6-dimethylcyclohexylamine), cyclohexane-1,4-diyldimethanamine, bicyclo[2,2,1]heptane-2,5-diamine, etc. Among these, 1,4-diaminocyclohexane or 1,4-diamino-2-methylcyclohexane is particularly preferred, and 1,4-diaminocyclohexane is more preferred. The alicyclic diamines may be used alone or in combination.

Diisocyanates include, for example, diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethyldiphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-diethyl Diphenylmethane-2,4'-diisocyanate, 3,2'- or 3,3'- or 4,2'- or 4,3'- or 5,2'- or 5,3'- or 6,2'- or 6,3'-dimethoxydiphenylmethane-2,4'-diisocyanate, diphenylmethane-4,4'-diisocyanate, diphenylmethane-3,3'-diisocyanate, diphenylmethane-3,4'-diisocyanate, diphenylether-4,4' -diisocyanate, benzophenone-4,4'-diisocyanate, diphenylsulfone-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-(2,2-bis(4-phenoxyphenyl)propane)diisocyanate, 3,3'- or 2,2'-dimethylbiphenyl-4,4'-diisocyanate, 3,3'- or 2,2'-di Examples of the diisocyanates include aromatic diisocyanates such as ethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, and 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and diisocyanates obtained by hydrogenating any of these diisocyanates (for example, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and hexamethylene diisocyanate). Among these, diphenylmethane-4,4'-diisocyanate, tolylene-2,4-diisocyanate, tolylene-2,6-diisocyanate, 3,3'-dimethylbiphenyl-4,4'-diisocyanate, naphthalene-2,6-diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, and 1,4-cyclohexane diisocyanate are preferred from the viewpoints of low moisture absorption, dimensional stability, cost, and polymerizability. The diisocyanates may be used alone or in combination.

The solvents used in the polyamic acid solution, polyimide solution, and polyamideimide solution of the present invention are not particularly limited as long as they dissolve the polyimide resin or its precursor, but examples include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, dimethylsulfoxide, γ-butyrolactone, cyclohexanone, and cyclopentanone. These may be used alone or in combination of two or more. In particular, considering the productivity and optical properties of the film, it is preferable to use N,N-dimethylacetamide as the main component of the organic solvent. In addition to these organic solvents, poor solvents such as toluene and xylene may be used to the extent that the polyimide resin or its precursor does not precipitate.

The thickness of the polyimide film in the present invention is preferably 3 μm or more, more preferably 11 μm or more, and even more preferably 24 μm or more. There is no particular upper limit to the thickness of the polyimide film, but for use as a flexible electronic device, it is preferably 250 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less.

The tensile modulus of the polyimide film of the present invention must be 3 GPa or more in both the MD and TD directions, preferably 4 GPa or more, and more preferably 5 GPa or more. When the tensile modulus is 3 GPa or more, peeling between the polyimide film and the functional element can be avoided, and the polyimide film has excellent handleability. The tensile modulus in both the MD and TD directions is preferably 20 GPa or less, more preferably 12 GPa or less, and even more preferably 10 GPa or less. When the tensile modulus is 20 GPa or less, the polyimide film can be used as a flexible film. The tensile modulus of the polyimide film refers to the average value of the tensile modulus in the flow direction (MD direction) and the tensile modulus in the width direction (TD direction) of the polyimide film. The tensile modulus of the polyimide film is measured by the method described in the examples.

The average CTE of the polyimide film in the present invention between 30°C and 300°C must be -5 ppm/°C to +55 ppm/°C. It is preferably -4 ppm/°C to +45 ppm/°C, more preferably -3 ppm/°C to +35 ppm/°C, even more preferably -2 ppm/°C to +20 ppm/°C, and even more preferably +1 ppm/°C to +10 ppm/°C. When the CTE is in the above range, the difference in linear expansion coefficient with the functional element can be kept small, and peeling between the polyimide film and the functional element can be avoided even when subjected to a process in which heat is applied, resulting in excellent processability. Here, CTE is a factor that represents reversible expansion and contraction with respect to temperature. The CTE of the polyimide film refers to the average value of the CTE in the flow direction (MD direction) and the CTE in the width direction (TD direction) of the polyimide film. The method for measuring the CTE of the polyimide film is the method described in the examples.

The polyimide film exhibiting the tensile modulus and CTE of the present invention can be realized by performing stretching during the film formation process of the polyimide film. Such stretching operation can be realized by applying a polyimide solution to a support for preparing the polyimide film, drying it to form a polyimide film containing 1 to 50% by mass of solvent, and then stretching the polyimide film containing 1 to 50% by mass of solvent at a high temperature on the support for preparing the polyimide film or in a state where it has been peeled off from the support, in the process of drying. In this case, an unstretched thermoplastic polymer film is used as the support for preparing the polyimide film, and the thermoplastic polymer film and the polyimide film are stretched simultaneously, and then the stretched polyimide film is peeled off from the thermoplastic polymer film, thereby preventing scratches on the polyimide film, especially during stretching in the MD direction, and a higher quality, colorless, and highly transparent polyimide film can be obtained. The preferred stretching ratio in the MD direction is 1.7 to 3.5 times, more preferably 2.0 to 3.0 times. The stretching ratio in the TD direction is preferably 1.7 to 3.5 times, more preferably 2.0 to 3.0 times. The ratio of the stretching ratio in the MD direction to the stretching ratio in the TD direction (MD/TD) is preferably more than 1, more preferably 1.01 or more, even more preferably 1.05 or more, still more preferably 1.08 or more, and particularly preferably 1.1 or more. The ratio is preferably 2.0 or less, more preferably 1.8 or less, even more preferably 1.5 or less, and particularly preferably 1.2 or less.

The solvent content of the polyimide film of the present invention must be 0.5 to 5.0% by mass. It is preferably in the range of 0.7 to 4.0% by mass, more preferably in the range of 1.0 to 3.0% by mass. By making the solvent content equal to or greater than the lower limit, the polyimide film surface is not excessively inactivated by excessive high-temperature treatment, and adhesion to the polymer composition forming the self-repairing layer described below is maintained, and deterioration of the yellow index can be suppressed. In addition, by making the solvent content equal to or less than the upper limit, it becomes easy to keep the tensile modulus and CTE within a preferred range, and it is possible to suppress the migration of residual solvent to the self-repairing layer, causing whitening and devitrification, and to suppress deterioration of the light transmittance and total light transmittance at a wavelength of 400 nm.

The solvent contained in the polyimide film may be a solvent residue (residual solvent) from the polyimide film production process (for example, the process of drying the polyimide film by treating it at high temperature), or a solvent added after the polyimide film is produced. Preferably, it is a residual solvent from the polyimide film production process.

The drying conditions for the polyimide film and/or green film are not particularly limited, and may be dried in one stage or in multiple stages. Drying in multiple stages is preferable. The number of drying stages in the multi-stage drying is not particularly limited, and is preferably two stages or more, more preferably three stages or more. Also, it is preferable that there are 10 stages or less, more preferably five stages or less. It is preferable that the drying temperature in the multi-stage drying is higher in the later stages. For example, in the case of two-stage drying, the first stage is preferably 100°C or more and 250°C or less, more preferably 120°C or more and 200°C or less, and even more preferably 150°C or more and 180°C or less. The second stage is preferably more than 250°C and 500°C or less, more preferably 280°C or more and 450°C or less, and even more preferably 300°C or more and 400°C or less.

The drying time can be set according to the drying temperature, film thickness, type of solvent, and drying equipment used. For example, in the case of the two-stage drying using a tenter, the drying time of the first stage is preferably 2 minutes or more and 15 minutes or less, more preferably 3 minutes or more and 12 minutes or less, and even more preferably 5 minutes or more and 8 minutes or less. The drying time of the second stage is preferably more than 1 minute and 10 minutes or less, more preferably 2 minutes or more and 8 minutes or less, and even more preferably 3 minutes or more and 5 minutes or less. By keeping it within the above range, the solvent content of the polyimide film can be kept within a predetermined range.

In the case of three-stage drying, the first stage is preferably 100°C or more and 200°C or less, more preferably 120°C or more and 190°C or less, and even more preferably 150°C or more and 180°C or less. The second stage is preferably more than 200°C and 300°C or less, more preferably 210°C or more and 280°C or less, and even more preferably 220°C or more and 250°C or less. The third stage is preferably more than 300°C and 500°C or less, more preferably 320°C or more and 450°C or less, and even more preferably 340°C or more and 400°C or less. The drying time can be set depending on the drying temperature. For example, in the case of the three-stage drying, the drying time of the first stage is preferably 30 seconds or more and 10 minutes or less, more preferably 1 minute or more and 8 minutes or less, and even more preferably 2 minutes or more and 5 minutes or less. The drying time of the second stage is preferably 30 seconds or more and 10 minutes or less, more preferably 1 minute or more and 8 minutes or less, and even more preferably 2 minutes or more and 5 minutes or less. The drying time in the third stage is preferably more than 1 minute and less than 10 minutes, more preferably from 2 minutes to 9 minutes, and further preferably from 3 minutes to 8 minutes. By setting the drying time within the above range, the solvent content of the polyimide film can be set within a predetermined range.

The laminate of the present invention has a self-repairing layer laminated on at least one side of a polyimide film exhibiting the above-mentioned tensile modulus and CTE, thereby ensuring the self-repairing properties of the laminate.

- Definition of self-repairing -
Here, the self-repair property refers to the property of restoring deformation or damage caused by distortion due to stress concentration when the stress is removed, and is specifically evaluated by the "return rate" obtained by the measurement method described in the examples.

As for the self-repairing properties of the laminate of the present invention, it is preferable that the return rate calculated by measuring the return rate is 80% or more, more preferably 85% or more, even more preferably 90% or more, even more preferably 95% or more, and particularly preferably 100%.

The self-repairing layer constituting the laminate of the present invention is preferably a polymer composition (hereinafter also referred to as a "self-repairing polymer composition") that has crosslinking points from the viewpoint of requiring low tackiness, stain resistance, and chemical resistance since it is mainly provided on the front surface of an image display device, and further contains crosslinking points in which some or all of the crosslinking points are movable from the viewpoint of achieving a self-repairing return rate of 80% or more.

The first type of the movable crosslinking points in the present invention refers to crosslinking points formed by chemical bonds other than covalent bonds, and examples of chemical bonds other than covalent bonds include ionic bonds and hydrogen bonds. When strain caused by stress concentration propagates, these chemical bonds are broken, causing deformation and damage, but after the stress is removed, the bonds are regenerated by molecular motion, and the deformation and damage disappear, resulting in self-repairing properties.

The second form of the movable crosslinking point in the present invention refers to a crosslinking point that is not based on a chemical bond but is based on a geometric constraint. Geometric constraints include a constraint in which a linear molecule penetrates the opening of a cyclic molecule, and a constraint in which cyclic molecules penetrate each other through the opening. When strain caused by stress concentration propagates, these constraints move the constrained points instead of severing the molecular bonds, causing deformation or damage. However, after the stress is removed, the constrained points are reconstructed by molecular motion, and the deformation or damage disappears, resulting in self-repairing properties.

As polymer compositions having crosslinking points formed by chemical bonds other than covalent bonds, which is the first form of crosslinking points having mobility in the present invention, examples of polymer compositions using ionic bonds include metal ion-containing acrylic acid ethylene copolymers, metal ion-containing (meth)acrylic acid ethylene copolymers, metal ion-containing sulfonic acid polyester polymers, and metal ion-containing sulfonic acid polyester polyether copolymers, and examples of polymer compositions using hydrogen bonds include polyether urethane copolymers, aliphatic polyester urethane copolymers, polyether polyester urethane copolymers, polyurethane acrylate copolymers, polyether polyamide copolymers, and aliphatic polyester polyamide copolymers.

Examples of polymer compositions having crosslinking points that are constrained by a geometric shape, which is the second form of crosslinking points having mobility in the present invention, include cyclic polyether ring-penetrating polyether polymers, cyclic polyether ring-penetrating aliphatic polyester copolymers, cyclic polyether ring-penetrating polyacrylic polymers, cyclodextrin ring-penetrating polyether polymers, and cyclodextrin ring-penetrating aliphatic polyester copolymers.

The content of the self-repairing polymer composition in the self-repairing layer is preferably 90% by mass or more, more preferably 95% by mass or more, even more preferably 99% by mass or more, and particularly preferably 99.9% by mass or more, and may be 100% by mass.

The polymer composition containing crosslinking points, some or all of which are movable, may be used alone or in combination, and may further contain additives commonly used in the technical field to which the present invention belongs, such as solvents, softeners, plasticizers, antioxidants, antioxidants, UV absorbers, light stabilizers, surface lubricants, leveling agents, antifouling agents, release agents, heat stabilizers, lubricants, inorganic fine particles, and surfactants, as necessary. The content of the additives is not particularly limited, as it can be adjusted in various ways within a range that does not deteriorate the physical properties of the laminate of the present invention, but may be, for example, about 0.1 to about 10 parts by weight per 100 parts by weight of the self-repairing layer.

The thickness of the self-repairing layer constituting the laminate of the present invention is preferably 5 μm or more, more preferably 8 μm or more, and particularly preferably 10 μm or more, from the viewpoint of ensuring adhesion and fully expressing the self-repairing function. On the other hand, from the viewpoint of ensuring transparency, processability, and moldability, the upper limit of the thickness is preferably 100 μm or less, more preferably 80 μm or less, and particularly preferably 50 μm or less.

The self-repairing layer constituting the laminate of the present invention can be formed by applying a self-repairing polymer composition onto a polyimide film, drying it as necessary, and then curing it by irradiating it with heat or active energy rays. In other words, the self-repairing polymer composition for forming the self-repairing layer of the present invention is preferably a thermosetting polymer composition or an active energy ray curable polymer composition.

The coating method used to apply the self-repairing polymer composition is preferably a wet coating method. Examples of such wet coating methods include reverse coating, spray coating, bar coating, gravure coating, rod coating, die coating, roll coating, and lip coating.

The preferred thickness of the laminate is 8 μm or more, more preferably 15 μm or more, and even more preferably 20 μm or more. Also, the preferred thickness is 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less.

The laminate of the present invention is a laminate in which a polyimide film and a self-repairing layer are laminated in that order, and the self-repairing layer has adhesion to the polyimide film, and the adhesion is evaluated by the "adhesion rate" determined by the measurement method specifically described in the examples.

In the laminate of the present invention, the adhesion rate of the self-repairing layer is preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, even more preferably 95% or more, and particularly preferably 100%. As described above, the adhesion rate can be achieved by setting the solvent content in the polyimide film to the above-mentioned lower limit or higher. In addition, the polyimide film may be subjected to a corona treatment, plasma treatment, ozone treatment, chemical treatment, solvent treatment, or the like as a pretreatment on the surface, within a range that does not reduce the transparency or adhesion to the self-repairing layer.

Since the laminate of the present invention is mainly used for the front panel and the periphery of electrodes of image display devices such as touch panels and displays, the yellowness index is preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, and even more preferably 3 or less. There is no particular lower limit for the yellowness index of the polyimide film, but for use as a flexible electronic device, it is preferably 0.1 or more, more preferably 0.2 or more, and even more preferably 0.3 or more.

Since the laminate of the present invention is mainly used for the front panel and around the electrodes of image display devices such as touch panels and displays, the light transmittance at a wavelength of 400 nm is preferably 70% or more, more preferably 72% or more, even more preferably 75% or more, and even more preferably 80% or more. There is no particular upper limit to the light transmittance at a wavelength of 400 nm of the polyimide film, but for use as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less.

Since the laminate of the present invention is mainly used for the front panel and the periphery of electrodes of image display devices such as touch panels and displays, the total light transmittance is preferably 85% or more, more preferably 86% or more, even more preferably 87% or more, and even more preferably 88% or more. There is no particular upper limit for the total light transmittance of the polyimide film, but for use as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, and even more preferably 97% or less.

The present invention will be described in detail below using examples, but the present invention is not limited to the following examples as long as it does not exceed the gist of the invention.

Unless otherwise specified, the measurements in the examples and comparative examples were measured using the following methods.

<Reduced Viscosity of Polyamic Acid and Polyimide>
The polymer was dissolved in N-methyl-2-pyrrolidone (or N,N-dimethylacetamide) so that the polymer concentration was 0.2 g/dl, and the solution was measured at 30° C. using an Ubbelohde type viscometer. (When the solvent used in preparing the polyamic acid solution was N,N-dimethylacetamide, the polymer was dissolved in N,N-dimethylacetamide and the measurement was performed.)

<Thickness of Polyimide Film and Laminate>
The measurement was carried out using a micrometer (Militron 1245D, manufactured by Fine Leaf Co., Ltd.).

<Tensile Modulus of Polyimide Film>
The polyimide film was cut into strips of 100 mm x 10 mm in the machine direction (MD) and width direction (TD) to prepare test pieces. The test pieces were cut from the center of the width direction. Using a tensile tester (Shimadzu Corporation, Autograph (R), model name AG-5000A), the tensile modulus was measured for five samples in each of the MD and TD directions under conditions of a temperature of 25°C, a tensile speed of 50 mm/min, and a chuck distance of 40 mm, and the average of all measured values was calculated.

<Coefficient of Linear Expansion (CTE) of Polyimide Film>
The expansion/contraction ratio was measured under the following conditions for five samples in each of the machine direction (MD) and width direction (TD) of the polyimide film. The expansion/contraction ratio/temperature was measured at intervals of 15°C, such as 30°C to 45°C and 45°C to 60°C. This measurement was continued up to 300°C, and the average value of all the measured values was calculated as CTE.
Device name: MAC Science TMA4000S
Sample length: 20 mm
Sample width: 2 mm
Heating start temperature: 25°C
End temperature: 400°C
Heating rate: 5°C/min
Atmosphere: Argon

<Solvent content in polyimide film>
The solvent content in the polyimide film was measured using a thermogravimetric analyzer (manufactured by TA Instruments, model name TGA2950). Approximately 10 mg of the sample was placed in an aluminum microcell and heated to 500°C at a rate of 5°C/min. The measurement was performed in a nitrogen atmosphere, and the weight loss between 100°C and 300°C was taken as the solvent content.

<Return rate of laminate>
A microhardness tester Fischerscope HM2000 (manufactured by Fischer) is used as a measuring device, and the laminate is fixed to a slide glass with instant adhesive Aron Alpha 221F (manufactured by Toa Gosei Co., Ltd.) and set in the measuring device. A load is applied to the laminate fixed to the slide glass from a Vickers pyramid diamond indenter at a measurement temperature of 30° C. for 15 seconds up to 0.5 mN, and the load is held at 0.5 mN for 5 seconds. The maximum displacement at that time is (h1). After that, the load is removed to 0.005 mN over 15 seconds, and the displacement when the load is held at 0.005 mN for 60 seconds is (h2), and the return rate [{(h1-h2)/h1}×100(%)] is calculated.

<Evaluation of Flexibility of Laminate>
Based on the bending test method in accordance with JIS K 5600-5-1 (1999), a bending test was performed 1000 times using a bending tester type 1 (manufactured by Imoto Manufacturing Co., Ltd., model IMC-AOF2, mandrel diameter φ20 mm), and then the surface of the laminate sample was visually observed and the flexibility was evaluated according to the following criteria.

◯: No microcracks were observed on the surface of the laminate sample. ×: Microcracks were observed on the surface of the laminate sample.

<Adhesion rate of laminate>
According to the cross-cut method of JIS K 5600-5-6 (1999), 11 linear cuts were made at 1 mm intervals in the vertical and horizontal directions on the self-repairing layer of the laminate sample under constant temperature and humidity conditions (23°C, 50% RH) using a checkerboard peel test tool to create 100 cross-cuts of 1 mm square. Adhesive tape No. 252 manufactured by Sekisui Chemical Co., Ltd. was attached onto the cross-cut grid, and after pressing evenly with a spatula, the adhesive tape was peeled off at 90 degrees to the laminate. The adhesion rate was determined as the number of cross-cuts of the self-repairing layer remaining on the polyimide film. The evaluation was determined as the number of remaining pieces out of 100 pieces in "%".

<Yellowness Index (YI) of Laminate>
Using a color meter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source, the tristimulus values XYZ of the polyimide film were measured in accordance with ASTM D1925, and the yellowness index (YI) was calculated by the following formula: The same measurement was performed three times, and the arithmetic average value was used.
YI=100×(1.28X-1.06Z)/Y

<400 nm Light Transmittance of Laminate>
The light transmittance at a wavelength of 400 nm was measured using a spectrophotometer (Hitachi, Ltd., "U-2001"), and the obtained value was converted to a thickness of 20 μm according to the Beer-Lambert law, and the obtained value was regarded as the 400 nm light transmittance of the polyimide film. The same measurement was performed three times, and the arithmetic average value was used.

<Total light transmittance (TT) of laminate>
The total light transmittance (TT) of the polyimide film was measured using a HAZEMETER (NDH5000, manufactured by Nippon Denshoku Industries Co., Ltd.). A D65 lamp was used as the light source. The same measurement was performed three times, and the arithmetic average value was used.

[Preparation of Polyamic Acid Solution A]
After replacing the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirring rod with nitrogen, 176.5 g (0.900 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 31.0 g (0.100 mol) of 4,4'-oxydiphthalic acid (ODPA), 160.1 g (0.500 mol) of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), 113.6 g (0.500 mol) of 4-amino-N-(4-aminophenyl)benzamide (DABAN), and 2000 g of N,N-dimethylacetamide were charged and dissolved in the reaction vessel under a nitrogen atmosphere, and the mixture was stirred at room temperature for 24 hours to carry out a polymerization reaction. Thereafter, the mixture was diluted with 1000 g of N,N-dimethylacetamide to obtain a polyamic acid solution A having a reduced viscosity of 4.50 dl/g.

[Preparation of Polyimide Solution B]
After replacing the inside of a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirring rod with nitrogen, 461 g of N,N-dimethylacetamide (DMAC) and 64.0 g (0.200 mol) of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB) were added to the reaction vessel under a nitrogen atmosphere and stirred to dissolve TFMB in DMAC. Next, while stirring the inside of the reaction vessel, 89.737 g (0.202 mol) of 4,4'-(2,2-hexafluoroisopropylidene)diphthalic dianhydride (6FDA) was added over about 10 minutes under a nitrogen stream, and the polymerization reaction was carried out by continuing stirring for 6 hours while adjusting the temperature to be in the range of 20 to 40 ° C., to obtain a viscous polyamic acid solution.
Next, 410 g of DMAC was added to the obtained polyamic acid solution to dilute it, and then 25.83 g of isoquinoline was added as an imidization accelerator. The polyamic acid solution was kept at a temperature range of 30 to 40°C while being stirred, and 122.5 g (1.20 mol) of acetic anhydride was slowly added dropwise thereto as an imidization agent over a period of about 10 minutes. Thereafter, the liquid temperature was further kept at 30 to 40°C and stirring was continued for 12 hours to carry out a chemical imidization reaction, thereby obtaining a polyimide solution.
Next, 1000 g of the obtained polyimide solution containing the imidization agent and the imidization accelerator was transferred to a reaction vessel equipped with a stirrer and agitator, and the temperature was kept at 15 to 25 ° C. while stirring at a speed of 120 rpm, and 1500 g of methanol was dropped therein at a rate of 10 g / min. When about 800 g of methanol was added, the polyimide solution became turbid and precipitation of powder-like polyimide was confirmed. Then, the entire amount of 1500 g of methanol was added, and the precipitation of polyimide was completed. Next, the contents of the reaction vessel were filtered using a suction filtration device, and further washed and filtered using 1000 g of methanol. Then, 50 g of the filtered polyimide powder was dried at 50 ° C. for 24 hours using a dryer equipped with a local exhaust device, and further dried at 260 ° C. for 2 hours to remove the remaining volatile components, and a polyimide powder was obtained. The reduced viscosity of the obtained polyimide powder was 5.40 dl / g. Next, 40 g of the obtained polyimide powder was dissolved in 300 g of DMAC to obtain a polyimide solution B.

[Preparation of Polyimide Solution C]
Into a reaction vessel equipped with a nitrogen inlet tube, a Dean-Stark tube, a reflux tube, a thermometer, and a stirrer, 120.5 g (0.485 mol) of 4,4'-diaminodiphenylsulfone (4,4'-DDS), 51.6 g (0.208 mol) of 3,3'-diaminodiphenylsulfone (3,3'-DDS), and 500 g of γ-butyrolactone (GBL) were added while introducing nitrogen gas. Then, 217.1 g (0.700 mol) of 4,4'-oxydiphthalic acid non-dihydrate (ODPA), 223 g of GBL, and 260 g of toluene were added at room temperature, and the internal temperature was raised to 160°C and heated to reflux at 160°C for 1 hour to perform imidization. After completion of imidization, the temperature was raised to 180°C, and the reaction was continued while drawing out toluene. After 12 hours of polymerization reaction, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content became 20% by mass, to obtain a polyimide solution C having a reduced viscosity of 2.50 dl/g.

[Preparation of Polyamic Acid Solution G]
After replacing the atmosphere in a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirring rod with nitrogen, 94.1 g (0.480 mol) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 108.9 g (0.370 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA), 46.5 g (0.150 mol) of 4,4'-oxydiphthalic acid (ODPA), 320.2 g (1.000 mol) of 2,2'-ditrifluoromethyl-4,4'-diaminobiphenyl (TFMB), and 2000 g of N,N-dimethylacetamide were charged and dissolved in the reaction vessel under a nitrogen atmosphere, and the mixture was stirred at room temperature for 24 hours to carry out a polymerization reaction. Thereafter, the mixture was diluted with 1000 g of N,N-dimethylacetamide to obtain a polyamic acid solution G having a reduced viscosity of 3.50 dl/g.

[Polyimide Film Preparation Example 1]
The polyamic acid solution A was applied to a mirror-finished stainless steel endless continuous belt (coating width 1240 mm) as a film preparation support using a die coater, and dried at 90 to 115 ° C for 10 minutes. The polyamic acid film (containing 9% by mass of residual solvent) that became self-supporting after drying was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin tenter so that the final pin sheet interval was 1140 mm, and heat treatment was performed at 170 ° C for 2 minutes in the first stage, 230 ° C for 2 minutes in the second stage, and 350 ° C for 6 minutes in the third stage to remove the residual solvent within a predetermined value range. Thereafter, it was cooled to room temperature in 2 minutes, and the parts with poor flatness at both ends of the film were cut off with a slitter and wound up into a roll to obtain a polyimide film 1A shown in Table 1. Similarly, the polyamic acid solution A was replaced with polyimide solution B or polyamic acid solution G, and the coating thickness on the support was changed to obtain a polyimide film 1B or polyimide film 1G shown in Table 1.

[Polyimide Film Preparation Example 2]
The polyamic acid solution A was applied to a polyester film having a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak density (Spd) of 20/μm2 or less, and no coating layer on the surface, which was a support for film production, using a comma coater (coating width 1240 mm), and dried at 90 to 115 ° C for 10 minutes. After drying, the polyamic acid film (containing 10% by mass of residual solvent) that became self-supporting was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin tenter so that the final pin sheet interval was 1140 mm, and heat treatment was performed at 170 ° C for 2 minutes at the first stage, 230 ° C for 2 minutes at the second stage, and 350 ° C for 6 minutes at the third stage, to remove the residual solvent so as to be within a predetermined value range. Thereafter, the film was cooled to room temperature in 2 minutes, and the parts of the film with poor flatness at both ends were cut off with a slitter and rolled up into a roll to obtain a polyimide film 2A shown in Table 1. Similarly, polyimide film 2C or polyimide film 2G shown in Table 1 was obtained by changing polyamic acid solution A to polyimide solution C or polyamic acid solution G and by changing the coating thickness on the support.

[Polyimide Film Preparation Example 3]
Polyimide solution B was applied to an unstretched polypropylene film having a regional surface roughness (Sa) of 3 nm, a maximum peak height (Sp) of 12 nm, and a peak density (Spd) of 25/μm2 or less, which was a support for film production, using a comma coater (coating width 450 mm), and dried at 85 to 105°C for 30 minutes to obtain a two-layer film of a support and a polyimide film (containing about 8% by mass of residual solvent). Next, this two-layer film was simultaneously stretched 2.8 times in the MD direction by utilizing the difference in peripheral speed between the rolls. Note that the rolls were arranged so that the rolls would not come into contact with the polyimide film side of the two-layer film between the rolls with the difference in peripheral speed. After stretching in the MD direction, both ends of the bilayer film were held by a clip tenter, and the film was conveyed while being heat-treated at 150°C for 6 minutes so that the final pin sheet interval was 1140 mm, i.e., the film was stretched 2.5 times in the TD direction. The polyimide film was then peeled off from the support of the bilayer film, and further heat-treated at 350°C for 3 minutes to remove the residual solvent within a predetermined range. The film was then cooled to room temperature for 2 minutes, and the parts of the film with poor flatness at both ends were cut off with a slitter and rolled up to obtain polyimide film 3B shown in Table 1. Similarly, polyimide solution B was replaced with polyimide solution C, and the coating thickness on the support was changed to obtain polyimide film 3C shown in Table 1.

[Polyimide Film Preparation Example 4]
The polyamic acid solution A was applied to a mirror-finished stainless steel endless continuous belt (coating width 1240 mm) as a film preparation support using a die coater, and dried at 90 to 115 ° C for 10 minutes. The polyamic acid film (containing 9% by mass of residual solvent) that became self-supporting after drying was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin tenter so that the final pin sheet interval was 1140 mm, and heat-treated at 170 ° C for 2 minutes in the first stage, 230 ° C for 2 minutes in the second stage, and 350 ° C for 10 minutes in the third stage, to remove the residual solvent within a predetermined value range. Thereafter, it was cooled to room temperature in 2 minutes, and the parts of the film with poor flatness at both ends were cut off with a slitter and wound up into a roll to obtain polyimide film 4A shown in Table 1.

[Polyimide Film Preparation Example 5]
The polyamic acid solution A was applied to a polyester film having a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak density (Spd) of 20/μm2 or less, and no coating layer on the surface, which was a support for film production, using a comma coater (coating width 1240 mm), and dried at 90 to 115 ° C for 10 minutes. The polyamic acid film (containing 10% by mass of residual solvent) that became self-supporting after drying was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin tenter so that the final pin sheet interval was 1140 mm, and heat treatment was performed at 170 ° C for 2 minutes at the first stage, 230 ° C for 2 minutes at the second stage, and 350 ° C for 10 minutes at the third stage, to remove the residual solvent so as to be within a predetermined value range. Thereafter, it was cooled to room temperature in 2 minutes, and the parts of the film with poor flatness at both ends were cut off with a slitter and wound up into a roll to obtain polyimide film 5A shown in Table 1.

[Polyimide Film Preparation Example 6]
The polyimide solution C was applied to a polyester film having a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak density (Spd) of 20/μm2 or less, and no coating layer on the surface, which was a support for film production, using a comma coater (coating width 1240 mm), and dried at 90 to 115 ° C for 10 minutes. After drying, the polyamic acid film (containing 10% by mass of residual solvent) that became self-supporting was peeled off from the support and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin tenter so that the final pin sheet interval was 1140 mm, and heat treatment was performed at 170 ° C for 2 minutes at the first stage, 230 ° C for 2 minutes at the second stage, and 350 ° C for 1 minute at the third stage, to remove the residual solvent so as to be within a predetermined value range. Thereafter, the film was cooled to room temperature in 2 minutes, and the parts with poor flatness at both ends of the film were cut off with a slitter and rolled up into a roll to obtain polyimide film 6C shown in Table 1.

[Polyimide Film Preparation Example 7]
Polyimide solution B was applied to an unstretched polypropylene film having a regional surface roughness (Sa) of 3 nm, a maximum peak height (Sp) of 12 nm, and a peak density (Spd) of 25/μm2 or less, which was a support for film production, using a comma coater (coating width 450 mm), and dried at 85 to 105°C for 30 minutes to obtain a two-layer film of a support and a polyimide film (containing about 8% by mass of residual solvent). Next, this two-layer film was simultaneously stretched 2.8 times in the MD direction by utilizing the difference in peripheral speed between the rolls. Note that the rolls were arranged so that the rolls would not come into contact with the polyimide film side of the two-layer film between the rolls with the difference in peripheral speed. After stretching in the MD direction, both ends of the bilayer film were held by a clip tenter, and the film was conveyed while being heat-treated at 150° C. so that the final pin sheet interval was 1140 mm, i.e., the film was stretched 2.5 times in the TD direction, and then the polyimide film was peeled off from the support of the bilayer film, and further heat-treated at 350° C. for 1 minute to remove the residual solvent within a predetermined range. The film was then cooled to room temperature for 2 minutes, and the portions of both ends of the film with poor flatness were cut off with a slitter and wound up into a roll to obtain polyimide film 7B shown in Table 1.

[Preparation of self-repairing layer forming composition D]
The compositions for forming a polyurethane acrylate copolymer as a polymer composition having crosslinking points formed by chemical bonds other than covalent bonds were weighed out as shown below and mixed at room temperature to prepare the composition.
AUP-787 (urethane acrylate containing photopolymerization initiator, manufactured by Tokushiki Co., Ltd.): 100 parts by weight Methyl ethyl ketone: 50 parts by weight Propylene glycol monomethyl ether: 30 parts by weight BYK-381 (surfactant, manufactured by BYK Japan Co., Ltd.): 1 part by weight

[Preparation of self-repairing layer forming composition E]
A composition for forming a cyclodextrin ring-penetrating polyether polymer as a polymer composition having crosslinking points formed by constraints due to geometric shapes and not by chemical bonds was measured out as follows and mixed at room temperature to prepare the composition.
SM3405P (modified polyrotaxane, manufactured by Advanced Soft Materials): 50 parts by weight M-309 (trimethylolpropane triacrylate, manufactured by Toagosei): 35 parts by weight M284 (polyethylene glycol diacrylate, manufactured by Toyo Chemicals): 15 parts by weight Methyl ethyl ketone: 40 parts by weight Propylene glycol monomethyl ether: 10 parts by weight Omnirad 184 (photopolymerization initiator, manufactured by IGM Resins): 4 parts by weight

[Preparation of hard coat layer forming composition F]
The composition for forming a (meth)acrylate copolymer as the polymer composition for forming the hard coat layer was measured as shown below and mixed at room temperature to prepare the composition.
OPSTAR Z7530 (mixture of organically modified silica fine particles and polyfunctional acrylate, manufactured by Arakawa Chemical Industries, Ltd.): 100 parts by weight Pentaerythritol triacrylate: 34 parts by weight 1-hydroxycyclohexyl phenyl ketone: 1.8 parts by weight BYK-300 (leveling agent, manufactured by BYK Japan): 0.1 parts by weight Propylene glycol monomethyl ether: 80 parts by weight

Example 1
<Preparation of Laminate>
The self-repairing layer-forming composition D was applied by a roll coater to the entire surface of the polyimide film 1A obtained in Preparation Example 1. Next, after drying at 80°C, the coating layer was cured by using an ultraviolet lamp with an illuminance of the irradiated part of 100mW/cm2 and an irradiation amount of 0.3J/cm2 while purging with nitrogen so that the atmosphere had an oxygen concentration of 1.0% by volume or less, to produce a laminate having a self-repairing layer with a laminate thickness of 22.0 μm and a dry layer thickness of 9.5 μm.

Examples 2 to 13
Similarly, laminates were prepared using the polyimide films and self-repairing layer-forming compositions D and E shown in Table 1, and the properties of the laminates were evaluated. The results are shown in Table 2. However, in the following, Example 3 and Example 6 are to be read as Reference Example 1 and Reference Example 2, respectively.

Comparative Examples 1 to 8
Similarly, laminates were prepared using the polyimide films and self-repairing layer-forming compositions D, E and F shown in Table 1, and the properties of the laminates were evaluated. The results are shown in Table 3.

As described above, the laminate of the present invention exhibits excellent transparency, self-repairability, and flexibility, and has excellent adhesion to the self-repairing layer, and is therefore extremely useful for the front panel and electrode periphery of image display devices such as touch panels and displays having foldable image display portions.

Claims (4)

A polyimide film having a tensile modulus of elasticity in both the MD and TD directions of 3 GPa or more, a CTE in both the MD and TD directions of -5 ppm/°C to +55 ppm/°C, and a solvent content of 1.5 to 5.0 mass %, and a self-repairing layer formed on at least one surface of the polyimide film , the self-repairing layer having a thickness of 5 μm or more,
A laminate in which a minute load of 0.5 mN is applied to the surface from a Vickers square pyramid diamond indenter using a microhardness tester, held for 5 seconds, and then the load is removed to 0.005 mN and held for 60 seconds, after which the return rate is 80% or more . The laminate according to claim 1 , characterized in that the adhesion rate of the self-repairing layer cut into a lattice shape to the polyimide film is 80% or more according to the cross-cut method of JIS K5600-5-6 (1999). 3. The laminate according to claim 1, which has a yellow index of 10 or less, a light transmittance at a wavelength of 400 nm of 70% or more, and a total light transmittance of 85% or more. The laminate according to any one of claims 1 to 3 , characterized in that the self-repairing layer is a polymer composition containing crosslinking points, and some or all of the crosslinking points are movable crosslinking points.