Laminate

Abstract

Provided is a laminate in which peeling and dropping of a self-restoring layer, which is for imparting scratch resistance in such a manner that scratching does not occur during handling and visibility is not reduced, do not occur during a machining process or during bending in a polyimide film in which the self-restoring layer is laminated and which has high tensile elasticity, low CTE, high heat resistance, and high chemical resistance.　A laminate characterized by including: a polyimide film in which the tensile modulus of elasticity in both an MD direction and a TD direction is 3 GPa or higher, the CTE in both the MD direction and the TD direction ranges from −5 to +55 ppm / °C, and the solvent content is 0.5-5.0 mass%; and a self-restoring layer formed on at least one surface of the polyimide film.

Description

Technical Field

[0001] The present invention relates to a laminate including a self-healing layer and a polyimide film. More specifically, the present invention relates to a laminate composed of a polyimide film that exhibits excellent transparency, self-healing property, and flexibility, and has excellent adhesion to the self-healing layer.

Background Art

[0002] Conventionally, a hard coat film in which a hard coat layer is provided on a transparent base film has been used for the front panel of an image display device such as a touch panel or a display, and around the electrodes, for the purpose of imparting scratch resistance so that the visibility is not reduced when scratched during handling (Patent Document 1). On the other hand, in recent years, in order to provide both high portability and a large screen, touch panels and displays in which the image display portion can be folded have been proposed (Patent Document 2), and flexibility superior to that of conventional hard coat films has been required.

[0003] The hard coat layer provided on the hard coat film has a high surface hardness in order to impart scratch resistance. However, since a coat layer having a high surface hardness tends to be brittle, it has been difficult to achieve both excellent flexibility. Therefore, as a means to replace the hard coat layer, a film provided with a self-healing coat layer that forms a flexible and tough coat layer and has a function of spontaneously disappearing deformations and scratches caused by stress during handling or processing has been proposed (Patent Document 3).

[0004] As the base film used for such a self-healing film, a transparent thermoplastic resin film made of polyethylene terephthalate (PET), acrylic, polycarbonate (PC), triacetyl cellulose (TAC), polyolefin, etc. is generally used. These thermoplastic resin films are excellent in transparency and bending resistance, and are also excellent in adhesion to the self-healing coat layer because they are easily adhesively treated and processed (Patent Document 4).

[0005] On the other hand, technological development has been carried out to directly form functional elements such as electrodes and display elements on a substrate film, and attempts have been made to use a polyimide film having heat resistance and chemical resistance instead of a general thermoplastic resin film as the substrate film for a hard coat film (Patent Documents 5 to 6).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Patent Document 5

Patent Document 6

Summary of the Invention

Problems to be Solved by the Invention

[0007] 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, heat resistance, and chemical resistance. When attempting to use a polyimide film, which is suitable for such a substrate film, as the substrate film of a self-healing film having excellent flexibility and bend resistance as exemplified in Patent Document 4, due to the flat and low-active surface of the polyimide film, the adhesion to the polyimide film is insufficient, and peeling or dropping of the coating layer is likely to occur during the processing process or bending.

[0008] On the one hand, in addition to having the function of absorbing external forces during handling, processing, etc. and repairing deformations and scratches, since the self-healing layer is provided on the front surface of the image display device, it is necessary to have low tackiness, antifouling properties, and chemical resistance, and a high degree of crosslinking and components with low activity in terms of composition are used. Therefore, for the self-healing layer, the easy-adhesion layer exemplified in Patent Document 5 for the hard coat layer has insufficient adhesion, and peeling or dropping of the self-healing layer is likely to occur during the processing process or bending.

[0009] Since both the polyimide film and the self-healing layer are low in activity in this way, while exhibiting excellent transparency, self-healing properties, and flexibility, it has been an issue to obtain adhesion between the self-healing layer and the polyimide film.

Means for Solving the Problems

[0010] As a result of intensive studies to solve the above problems, the inventors have found that such problems can be solved and have reached the present invention. That is, the present invention has the following configuration.

[0011] A laminate comprising a polyimide film having a tensile elastic modulus of 3 GPa or more in both the MD direction and the TD direction, a CTE of -5 ppm / °C to +55 ppm / °C in both the MD direction and the TD direction, and a solvent content of 0.5 to 5.0% by mass, and a self-healing layer formed on at least one surface of the polyimide film.

[0012] The laminate preferably has a return rate of 80% or more after applying a minute load of 0.5 mN from a Vickers square pyramid diamond indenter to the surface with a micro hardness tester, holding for 5 seconds, unloading to 0.005 mN, and then holding for 60 seconds. Further, the laminate preferably has an adhesion rate of 80% or more of the self-healing layer cut in a lattice pattern by the cross cut method of JIS K 5600-5-6 (1999) to the polyimide film. Further, the laminate preferably 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 self-healing layer is a polymer composition containing cross-linking points, and preferably, some or all of the cross-linking points are cross-linking points having mobility.

Advantages of the Invention

[0013] According to the present invention, even when a polyimide film having a low-active surface is used as a base film, it is possible to provide a laminate that exhibits excellent self-healing properties and has excellent adhesion to the self-healing layer. Further, since it has excellent transparency and flexibility, it is possible to provide a transparent laminate suitable for a front panel of an image display device such as a foldable touch panel or a display where an image display portion can be folded, or around an electrode.

Embodiments for Carrying Out the Invention

[0014] Hereinafter, the laminate of the embodiment of the present invention will be described. The laminate of the present invention is a laminate including a polyimide film and a self-healing layer formed on at least one surface of the polyimide film. The polyimide film constituting the laminate of the present invention is a film of a polymer having an imide bond in the main chain, preferably a polyimide film or a polyamide-imide film, and more preferably a polyimide film.

[0015] 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 producing a polyimide film, dried to form a green film (also referred to as a "precursor film", "polyamic acid film" or "polyamic acid film"), and further on the support for producing a polyimide film, or in a state peeled off from the support, the green film is heat-treated at a high temperature to cause a dehydration ring-closing polymerization reaction to obtain it. Also, as the second method, a polyimide solution obtained by a dehydration ring-closing polymerization reaction of diamines and tetracarboxylic acids in a solvent is applied to a support for producing a polyimide film, dried to form a polyimide film containing 1 to 50% by mass of a solvent, and further on the support for producing a polyimide film, or in a state peeled off from the support, the polyimide film containing 1 to 50% by mass of a solvent is heat-treated at a high temperature to be dried to obtain it.

[0016] Furthermore, in the third method, a polyamide-imide solution obtained by polymerizing diisocyanates and tricarboxylic acids in a solvent is applied to a support for producing a polyamide-imide film, dried to form a polyamide-imide film containing 1 to 50% by mass of a solvent, and further on the support for producing a polyamide-imide, or in a state peeled off from the support, the polyamide-imide film containing 1 to 50% by mass of a solvent is heat-treated at a high temperature to be dried to obtain it. In addition, in the above three manufacturing methods, dicarboxylic acids can also be appropriately used.

[0017] 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, etc., which are usually used in polyimide synthesis or polyamide-imide synthesis, can be used. Among them, aromatic tetracarboxylic anhydrides or alicyclic tetracarboxylic anhydrides are preferable, aromatic tetracarboxylic anhydrides are more preferable from the viewpoint of heat resistance, and alicyclic tetracarboxylic acids are more preferable from the viewpoint of light transmittance (transparency). When the tetracarboxylic acids are acid anhydrides, the number of anhydride structures in the molecule may be 1 or 2, but those having 2 anhydride structures (dianhydrides) are preferable. The tetracarboxylic acids, tricarboxylic acids, and dicarboxylic acids may be used alone or in combination of two or more.

[0018] As the aromatic tetracarboxylic acids for obtaining a highly heat-resistant polyimide in the present invention, 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-diyl-oxy)]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-diyl-oxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(1,4-xylene-2,5-diyl-oxy)]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-diyl-oxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3-oxo-1,3-dihydro-2-benzofuran-1,1-diyl)bis(naphthalene-1,4-diyl-oxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(benzene-1,4-diyl-oxy)]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-diyl-oxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[(3H-2,1-benzoxathiol-1,1-dioxide-3,3-diyl)bis(1,4-xylene-2,5-diyl-oxy)]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-diyl-oxy)]dibenzene-1,2-dicarboxylic acid, 4,4'-[4,4'-(3H-2,1-Benzoxathiol-1,1-dioxide-3,3-diyl)bis(naphthalene-1,4-diyl oxy)]dibenzen-1,2-dicarboxylic acid, 3,3',4,4'-benzophenone tetracarboxylic acid, 3,3',4,4'-benzophenone tetracarboxylic acid, 3,3',4,4'-diphenylsulfone tetracarboxylic acid, 3,3',4,4'-biphenyltetracarboxylic acid, 2,3,3',4'-biphenyltetracarboxylic acid, pyromellitic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-2,6-diylbis(oxycarbonyl)]dibenzen-1,2-dicarboxylic acid, 4,4'-[spiro(xanthene-9,9'-fluorene)-3,6-diylbis(oxycarbonyl)]dibenzen-1,2-dicarboxylic acid, and the like, and tetracarboxylic acids and their acid anhydrides thereof. Among these, dianhydrides having two acid anhydride structures are preferred, and particularly, 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 emphasized, for example, 50% by mass or more of all tetracarboxylic acids is preferred, more preferably 60% by mass or more, still more preferably 70% by mass or more, and even more preferably 80% by mass or more.,

[0019] As alicyclic tetracarboxylic acids for obtaining a polyimide with high colorless transparency, there are 1,2,3,4-cyclobutanetetracarboxylic acid, 1,2,3,4-cyclopentanetetracarboxylic acid, 3-(carboxymethyl)cyclopentane-1,2,4-tricarboxylic acid, 1,2,3,4-cyclohexanetetracarboxylic acid, 1,2,4,5-cyclohexanetetracarboxylic acid, 3,3’,4,4’-bicyclohexyltetracarboxylic acid, bicyclo[2,2,1]heptane-2,3,5,6-tetracarboxylic 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, tetradehydroanthracene-2,3,6,7-tetracarboxylic acid, tetradehydro-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, 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 (alias “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 (alias “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-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, norbornane-2-spiro-α-(methylcyclohexanone)-α’-spiro-2’’-norbornane-5,5’’,6,6’’-tetracarboxylic acid, and the like, and tetracarboxylic acids and their 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, 1,2,4,5-cyclohexanetetracarboxylic dianhydride are preferred, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,4,5-cyclohexanetetracarboxylic dianhydride are more preferred, 1,2,3,4-Cyclobutanetetracarboxylic dianhydride is more preferable. These may be used alone or in combination of two or more. In the case of emphasizing transparency, for alicyclic tetracarboxylic acids, for example, 50% by mass or more of all tetracarboxylic acids is preferable, more preferably 60% by mass or more, still more preferably 70% by mass or more, and even more preferably 80% by mass or more.

[0020] Examples of the tricarboxylic acids include aromatic tricarboxylic acids such as trimellitic acid, 1,2,5-naphthalenetricarboxylic acid, diphenyl ether-3,3',4'-tricarboxylic acid, diphenyl sulfone-3,3',4'-tricarboxylic acid, or 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, polyethylene glycol bistrimellitate, and monohydrides, esterified products thereof. Among these, monohydrides having one acid anhydride structure are preferable, and in particular, trimellitic anhydride and hexahydrotrimellitic anhydride are preferable. These may be used alone or in combination of a plurality.

[0021] Examples of the dicarboxylic acids include aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, orthophthalic acid, naphthalenedicarboxylic acid, biphenyl-4,4'-dicarboxylic acid, 4,4'-oxydibenzenedicarboxylic acid, or hydrogenated products of the above aromatic dicarboxylic acids such as 1,4-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid, oxalic acid, succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, 2-methylsuccinic acid, and acid chlorides or esterified products thereof. Among these, aromatic dicarboxylic acids and their hydrogenated products are preferred, and particularly, terephthalic acid, 1,4-cyclohexanedicarboxylic acid, and 4,4'-oxydibenzenedicarboxylic acid are preferred. The dicarboxylic acids may be used alone or in combination of two or more.

[0022] There are no particular restrictions on the diamines or isocyanates for obtaining the polyimide having high heat resistance and / or high colorless transparency in the present invention, and aromatic diamines, aliphatic diamines, alicyclic diamines, aromatic diisocyanates, aliphatic diisocyanates, alicyclic diisocyanates, etc. usually used for 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. Further, the use of aromatic diamines or diisocyanates having a benzoxazole structure is preferable because it is possible to 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.

[0023] 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)phenyl]ketone, bis[4-(3-aminophenoxy)phenyl]sulfide, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]-1,1,1,3,3,3-hexafluoropropane, m-phenylenediamine, o-phenylenediamine, p-phenylenediamine, m-aminobenzylamine, p-aminobenzylamine, 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'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, bis[4-(4-aminophenoxy)phenyl]methane, 1,1-bis[4-(4-aminophenoxy)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-aminophenoxy)benzene, 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'-diaminodiphenylsulfide, 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-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, 3,3'-diamino-4,4'-dibiphenoxybenzophenone, 4,4'-diamino-5,5'-dibiphenoxybenzophenone, 3,4'-diamino-4,5'-dibiphenoxybenzophenone, 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, 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, 4,4’-[spiro(xanthene-9,9’-fluorene)-3,6-diylbis(oxycarbonyl)]bisaniline and the like can be mentioned. Further, some or all of the hydrogen atoms on the aromatic ring of the above aromatic diamine may be substituted with a halogen atom, an alkyl group or an 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. Incidentally, the aromatic diamines may be used alone or in combination of a plurality of them.,

[0024] In addition, the aromatic diamines having the benzoxazole structure are not particularly limited. For example, 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-aminobenzoxazolyl)-4-(6-aminobenzoxazolyl)benzene, 2,6-(4,4'-diaminodiphenyl)benz[1,2-d:5,4-d']bisoxazole, 2,6-(4,4'-diaminodiphenyl)benz[1,2-d:4,5-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benz[1,2-d:5,4-d']bisoxazole, 2,6-(3,4'-diaminodiphenyl)benz[1,2-d:4,5-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benz[1,2-d:5,4-d']bisoxazole, 2,6-(3,3'-diaminodiphenyl)benz[1,2-d:4,5-d']bisoxazole, etc. may be mentioned. Among these, particularly, 2,2'-ditrifuluoromethyl-4,4'-diaminobiphenyl, 4-amino-N-(4-aminophenyl)benzamide, 4,4'-diaminodiphenylsulfone, or 3,3'-diaminobenzophenone is preferable. Incidentally, the aromatic diamines having an oxazole structure may be used alone or in combination of a plurality of them.

[0025] Examples of the 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-diyl dimethanamine, bicyclo[2,2,1]heptane-2,5-diamine, and the like. 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 of two or more.

[0026] Examples of the diisocyanates include aromatic diisocyanates such as 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'-diethyldiphenylmethane-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, diphenyl ether-4,4'-diisocyanate, benzophenone-4,4'-diisocyanate, diphenyl sulfone-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'-diethylbiphenyl-4,4'-diisocyanate, 3,3'-dimethoxybiphenyl-4,4'-diisocyanate, 3,3'-diethoxybiphenyl-4,4'-diisocyanate, and diisocyanates obtained by hydrogenating any of these (for example, isophorone diisocyanate, 1,4-cyclohexane diisocyanate, 1,3-cyclohexane diisocyanate, 4,4'-dicyclohexylmethane diisocyanate, 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, or 1,4-cyclohexane diisocyanate is preferable from the viewpoints of low hygroscopicity, dimensional stability, price, and polymerizability. The diisocyanates may be used alone or in combination of two or more.

[0027] The solvent used in the polyamic acid solution, polyimide solution, and polyamideimide solution of the present invention is not particularly specified as long as it can dissolve a polyimide-based resin or its precursor. Examples thereof include N-methyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 1,3-dimethyl-2-imidazolidinone, tetramethylurea, sulfolane, dimethyl sulfoxide, γ-butyrolactone, cyclohexanone, cyclopentanone, and the like. These may be used alone or in combination of two or more. Particularly in consideration of productivity and the optical properties of the film, it is preferable to use N,N-dimethylacetamide as the main component of the organic solvent. In addition, a poor solvent such as toluene or xylene may be used in an amount such that the polyimide-based resin or its precursor does not precipitate, in combination with these organic solvents.

[0028] 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. The upper limit of the thickness of the polyimide film is not particularly limited, 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.

[0029] The tensile modulus of the polyimide film of the present invention needs to be 3 GPa or more in both the MD direction and the TD direction, 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 handleability is excellent. The tensile modulus in both the MD direction and the TD direction 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 width direction (TD direction) of the polyimide film. The measurement method of the tensile modulus of the polyimide film is according to the method described in the examples.

[0030] The average CTE of the polyimide film in the present invention between 30°C and 300°C needs to be -5 ppm / °C to +55 ppm / °C. Preferably it is -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 within the above range, the difference in the coefficient of linear expansion from the functional element can be kept small, and peeling between the polyimide film and the functional element can be avoided even when subjected to the process of applying heat, and the processability is excellent. Here, CTE is a factor representing 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 width direction (TD direction) of the polyimide film. The measurement method of the CTE of the polyimide film is according to the method described in the examples.

[0031] The polyimide film showing the tensile elastic modulus and CTE of the present invention can be realized by performing stretching in the film forming process of the polyimide film. Such stretching operation is to apply a polyimide solution onto a support for producing a polyimide film, dry it to form a polyimide film containing 1 to 50% by mass of a solvent, and then on the support for producing a polyimide film or in a state peeled off from the support, in the process of heat-treating and drying the polyimide film containing 1 to 50% by mass of a solvent, stretch it 1.5 to 4.0 times in the MD direction and 1.4 to 3.0 times in the TD direction. At this time, an unstretched thermoplastic polymer film is used as the support for producing the polyimide film, and after stretching the thermoplastic polymer film and the polyimide film simultaneously, the stretched polyimide film is peeled off from the thermoplastic polymer film, whereby it is possible to prevent scratches from entering the polyimide film especially during stretching in the MD direction, and a higher-quality colorless and highly transparent polyimide film can be obtained. The preferable stretching ratio in the MD direction is 1.7 to 3.5 times, more preferably 2.0 to 3.0 times. Also, the preferable stretching ratio in the TD direction is 1.7 to 3.5 times, more preferably 2.0 to 3.0 times. The ratio (MD / TD) of the stretching ratio in the MD direction to the stretching ratio in the TD direction is preferably more than 1, more preferably 1.01 or more, further preferably 1.05 or more, even more preferably 1.08 or more, and particularly preferably 1.1 or more. Also, it is preferably 2.0 or less, more preferably 1.8 or less, further preferably 1.5 or less, and particularly preferably 1.2 or less.

[0032] The solvent content of the polyimide film of the present invention needs to be 0.5 to 5.0% by mass. Preferably, it is 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 setting the solvent content to be equal to or higher than the above lower limit value, the surface of the polyimide film will not become overly inert due to excessive high-temperature treatment, the adhesion to the polymer composition for forming the self-healing layer described later will be maintained, and the deterioration of the yellow index can be suppressed. Also, by setting the solvent content to be equal to or lower than the above upper limit value, it becomes easier to keep the tensile modulus of elasticity and CTE within a preferable range, and it is possible to suppress the migration of the residual solvent to the self-healing layer and the occurrence of whitening and devitrification, thereby suppressing the deterioration of the light transmittance at a wavelength of 400 nm and the total light transmittance.

[0033] The solvent contained in the polyimide film may be the residue of the solvent (residual solvent) in the process of producing the polyimide film (for example, the process of drying the polyimide film by high-temperature treatment), or it may be a solvent added after the polyimide film is produced. Preferably, it is the residual solvent in the process of producing the polyimide film.

[0034] The drying conditions of the polyimide film and / or the green film are not particularly limited, and it may be dried in one step or in multiple steps. It is preferable to dry in multiple steps. The number of drying steps during multi-step drying is not particularly limited, and it is preferably two or more steps, more preferably three or more steps. Also, it is preferably ten steps or less, more preferably five steps or less. It is preferable that the drying temperature in multiple steps becomes higher in the later stage. For example, in the case of two-step drying, the first step is preferably 100°C or higher and 250°C or lower, more preferably 120°C or higher and 200°C or lower, and even more preferably 150°C or higher and 180°C or lower. The second step is preferably above 250°C and below 500°C, more preferably 280°C or higher and 450°C or lower, and even more preferably 300°C or higher and 400°C or lower.

[0035] Also, the drying time can be set according to the above drying temperature, film thickness, type of solvent, and drying equipment used. For example, in the case of using a tenter for the two-stage drying, the drying time in 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 in 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 setting within the above range, the solvent content of the polyimide film can be made within a predetermined range.

[0036] Also, 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. Also, the drying time can be set according to the drying temperature. For example, in the case of the three-stage drying, the drying time in 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 in 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 2 minutes or more and 9 minutes or less, and even more preferably 3 minutes or more and 8 minutes or less. By setting within the above range, the solvent content of the polyimide film can be made within a predetermined range.

[0037] The laminate of the present invention is one in which a self-healing layer is laminated on at least one surface of a polyimide film exhibiting the above tensile elastic modulus and CTE, thereby ensuring the self-healing property of the laminate.

[0038] - Definition of self-healing property - Here, the self-healing property refers to the property of restoring deformations and scratches formed by strain due to stress concentration when the stress is removed, and specifically, it is evaluated by the "recovery rate" obtained by the measurement method described in the examples.

[0039] As the self-healing property of the laminate of the present invention, it is preferable that the recovery rate calculated by the measurement of the recovery rate is 80% or more, more preferably 85% or more, further preferably 90% or more, still further preferably 95% or more, and particularly preferably 100%.

[0040] Since the self-healing layer constituting the laminate of the present invention is mainly provided on the front surface of the image display device, it has crosslinking points from the viewpoints of low tackiness, antifouling property, and chemical resistance, and further, from the viewpoint of achieving a recovery rate of 80% or more as the self-healing property, it is preferable that a part or all of the crosslinking points include a polymer composition having movable crosslinking points (hereinafter, also referred to as "self-healing polymer composition").

[0041] The crosslinking points having mobility in the present invention represent, as a first form, crosslinking points formed by chemical bonds other than covalent bonds. Examples of chemical bonds other than covalent bonds include ionic bonds and hydrogen bonds. When the strain generated by stress concentration propagates, these chemical bonds are broken and deformations and scratches occur, but after the stress is removed, the bonds are regenerated by molecular motion, so that the deformations and scratches disappear and the material has self-healing properties.

[0042] The crosslinking points having mobility in the present invention represent, as a second form, crosslinking points composed of constraints depending on a geometric shape not based on chemical bonds. Examples of constraints depending on a geometric shape include a constraint in which a linear molecule penetrates through an opening of a cyclic molecule, and a constraint in which cyclic molecules penetrate through an opening. When the strain generated by stress concentration propagates, instead of the molecular bonds being broken, the constrained portions move and deformations and scratches occur, but after the stress is removed, the constrained portions are reconfigured by molecular motion, so that the deformations and scratches disappear and the material has self-healing properties.

[0043] As a polymer composition having a crosslinking point formed by a chemical bond other than a covalent bond, which is the first form of the crosslinking point having mobility in the present invention, as a polymer composition using an ionic bond, a metal ion-containing ethylene acrylate copolymer, a metal ion-containing (meth)acrylate ethylene copolymer, a metal ion-containing sulfonic acid polyester polymer, and a metal ion-containing sulfonic acid polyester polyether copolymer can be mentioned. As a polymer composition using a hydrogen bond, a polyether urethane copolymer, an aliphatic polyester urethane copolymer, a polyether polyester urethane copolymer, a polyurethane acrylate copolymer, a polyether polyamide copolymer, and an aliphatic polyester polyamide copolymer can be mentioned.

[0044] As a polymer composition having a crosslinking point composed of a restraint depending on a geometric shape, which is the second form of the crosslinking point having mobility in the present invention, a cyclic polyether ring-penetrating polyether polymer, a cyclic polyether ring-penetrating aliphatic polyester copolymer, a cyclic polyether ring-penetrating polyacrylic polymer, a cyclodextrin ring-penetrating polyether polymer, and a cyclodextrin ring-penetrating aliphatic polyester copolymer can be mentioned.

[0045] The content of the self-healing polymer composition contained in the self-healing layer is preferably 90% by mass or more, more preferably 95% by mass or more, still more preferably 99% by mass or more, particularly preferably 99.9% by mass or more, and may be 100% by mass.

[0046] The polymer composition containing crosslinking points, some or all of which have mobility, may be used alone or in combination of a plurality, and if necessary, solvents, softeners, plasticizers, anti-aging agents, antioxidants, ultraviolet absorbers, light stabilizers, surface lubricants, leveling agents, antifouling agents, release agents, heat stabilizers, lubricants, inorganic fine particles, surfactants, etc., additives commonly used in the technical field to which the present invention belongs can be additionally included. Further, since the content can be variously adjusted within a range that does not deteriorate the physical properties of the laminate of the present invention, there is no particular limitation. For example, it may be contained in an amount of about 0.1 to about 10 parts by mass with respect to 100 parts by mass of the self-healing layer.

[0047] From the viewpoint of ensuring adhesion and sufficiently expressing the self-healing function, the thickness of the self-healing 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. 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.

[0048] The self-healing layer constituting the laminate of the present invention can be formed by applying a self-healing polymer composition on a polyimide film, drying if necessary, and then irradiating with heat or active energy rays to cure it. That is, the self-healing polymer composition for forming the self-healing layer according to the present invention is preferably a thermosetting polymer composition or an active energy ray-curable polymer composition.

[0049] As the coating method used for coating the self-healing polymer composition, a wet coating method is preferable. Examples of such a wet coating method include a reverse coating method, a spray coating method, a bar coating method, a gravure coating method, a rod coating method, a die coating method, a roll coating method, a lip coating method, etc.

[0050] The preferred thickness of the laminate is 8 μm or more, more preferably 15 μm, and even more preferably 20 μm or more. Also, it is preferably 300 μm or less, more preferably 200 μm or less, and even more preferably 100 μm or less.

[0051] The laminate of the present invention is formed by laminating a polyimide film and a self-healing layer in this order. The self-healing layer has adhesiveness to the polyimide film, and the adhesiveness is evaluated by the "adhesion rate" determined by the measurement method described in the specific examples.

[0052] As the adhesiveness of the self-healing layer of the laminate of the present invention, it is preferable that the adhesion rate is 80% or more, more preferably 85% or more, even more preferably 90% or more, still more preferably 95% or more, and particularly preferably 100%. As described above, a preferable value can be achieved by setting the solvent content contained in the polyimide film to be equal to or higher than the above lower limit value. Further, the polyimide film may be subjected to corona treatment, plasma treatment, ozone treatment, chemical treatment, solvent treatment, etc. as a pretreatment on the surface within a range that does not reduce the transparency and the adhesiveness to the self-healing layer.

[0053] Since the laminate of the present invention is mainly used for the front panel of an image display device such as a touch panel or a display, and around the electrodes, the yellowness index is preferably 10 or less, more preferably 7 or less, even more preferably 5 or less, and still more preferably 3 or less. The lower limit of the yellowness of the polyimide film is not particularly limited, 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.

[0054] Since the laminate of the present invention is mainly used for the front panel of an image display device such as a touch panel or a display, and around the electrodes, the light transmittance at a wavelength of 400 nm is preferably 70% or more, more preferably 72% or more, still more preferably 75% or more, and even more preferably 80% or more. The upper limit of the light transmittance at a wavelength of 400 nm of the polyimide film is not particularly limited, but in order to be used as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, and still more preferably 97% or less.

[0055] Since the laminate of the present invention is mainly used for the front panel of an image display device such as a touch panel or a display, and around the electrodes, the total light transmittance is preferably 85% or more, more preferably 86% or more, still more preferably 87% or more, and even more preferably 88% or more. The upper limit of the total light transmittance of the polyimide film is not particularly limited, but in order to be used as a flexible electronic device, it is preferably 99% or less, more preferably 98% or less, and still more preferably 97% or less.

Examples

[0056] Hereinafter, the present invention will be described in detail using examples. However, the present invention is not limited to the following examples as long as the gist thereof is not exceeded.

[0057] Each measured value in the examples and comparative examples was measured by the following method unless otherwise specified.

[0058] <Reduced viscosity of polyamic acid and polyimide> A solution dissolved in N-methyl-2-pyrrolidone (or N,N-dimethylacetamide) so that the polymer concentration was 0.2 g / dl was measured at 30 °C using an Ubbelohde viscometer tube. (When the solvent used for preparing the polyamic acid solution was N,N-dimethylacetamide, the polymer was dissolved using N,N-dimethylacetamide and measured.)

[0059] <Thickness of polyimide film and laminate> Measurement was carried out using a micrometer (manufactured by Fine Reuleaux Co., Ltd., Millitron 1245D).

[0060] <Tensile modulus of polyimide film> Samples were cut into strips of 100 mm × 10 mm in the machine direction (MD direction) and the transverse direction (TD direction) of the polyimide film, respectively, and used as test pieces. The test pieces were cut from the central part in the transverse direction. Using a tensile testing machine (manufactured by Shimadzu Corporation, Autograph (R), model name AG-5000A), the tensile modulus was measured for 5 samples in each of the MD direction and the TD direction under the conditions of a temperature of 25°C, a tensile speed of 50 mm / min, and a chuck distance of 40 mm, and the average value of all the measured values was obtained.

[0061] <Coefficient of thermal expansion (CTE) of polyimide film> At 5 points in each of the machine direction (MD direction) and the transverse direction (TD direction) of the polyimide film, the expansion and contraction rate was measured under the following conditions, and the expansion and contraction rate / temperature at intervals of 15°C such as 30°C to 45°C and 45°C to 60°C was measured. This measurement was carried out up to 300°C, and the average value of all the measured values was calculated as the CTE. Equipment name: TMA4000S manufactured by MAC Science Co., Ltd. Sample length: 20 mm Sample width: 2 mm Initial temperature for heating: 25°C Final temperature for heating: 400°C Heating rate: 5°C / min Atmosphere: Argon

[0062] <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 set in an aluminum micro cell and heated to 500°C at a rate of 5°C / min. The measurement was carried out under a nitrogen atmosphere, and the weight reduction between 100°C and 300°C was taken as the solvent content.

[0063] <Recovery rate of laminate> As a measuring device, a microhardness tester Fisherscope HM2000 (manufactured by Fisher) was used. The laminate was fixed to a slide glass with an instant adhesive Aron Alpha 221F (manufactured by Toagosei Co., Ltd.) and set in the above measuring device. A load was applied to the laminate fixed to the slide glass at a measuring temperature of 30 °C for 15 seconds from a Vickers square pyramid diamond indenter up to 0.5 mN and held at 0.5 mN for 5 seconds. The maximum displacement at that time was taken as (h1). Then, the load was unloaded to 0.005 mN over 15 seconds, and the displacement when held at 0.005 mN for 60 seconds was taken as (h2), and the recovery rate [{(h1 - h2) / h1} × 100 (%)] was calculated.

[0064] <Flexibility Evaluation of Laminate> Based on the bending test method conforming to JIS K 5600-5-1 (1999), a bending test was performed 1000 times using a bending tester type 1 (manufactured by Imoto Seisakusho, model IMC-AOF2, mandrel diameter φ20 mm). After that, the surface of the laminate sample was visually observed, and the flexibility was evaluated according to the following criteria.

[0065] 〇: No microcracks were observed on the surface of the laminate sample. ×: Microcracks were observed on the surface of the laminate sample.

[0066] <Adhesion Rate of Laminate> By the cross-cut method of JIS K 5600-5-6 (1999), under constant temperature and humidity conditions (23 °C, 50% RH), on the self-healing layer of the laminate sample, 11 linear cuts at 1 mm intervals were made in the vertical and horizontal directions using a checkerboard peeling test jig, and 100 cross-cuts of 1 square mm were produced. An adhesive tape No. 252 manufactured by Sekisui Chemical Co., Ltd. was pasted on this cross-cut grid, and after uniformly pressing it with a spatula, the adhesive tape was peeled off from the laminate in a 90-degree direction. The adhesion rate is determined as the number of remaining pieces on the polyimide film of the self-healing layer cross-cut. The evaluation was obtained as the number of remaining pieces out of 100 in "%".

[0067] <Yellowness Index (YI) of the laminate> Using a colorimeter (ZE6000, manufactured by Nippon Denshoku Industries Co., Ltd.) and a C2 light source, the tristimulus values XYZ of the polyimide film were measured according to ASTM D1925, and the yellowness index (YI) was calculated by the following formula. The same measurement was performed 3 times, and the arithmetic mean value was adopted. YI = 100×(1.28X - 1.06Z) / Y

[0068] <Light transmittance at 400 nm of the laminate> Using a spectrophotometer (U-2001, manufactured by Hitachi, Ltd.), the light transmittance at a wavelength of 400 nm was measured, and the obtained value was converted to a thickness of 20 μm according to the Lambert-Beer's law. The obtained value was taken as the light transmittance at 400 nm of the polyimide film. The same measurement was performed 3 times, and the arithmetic mean value was adopted.

[0069] <Total light transmittance (TT) of the 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 3 times, and the arithmetic mean value was adopted.

[0070] 〔Preparation of polyamic acid solution A〕 After purging the inside of a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer 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'-bis(trifluoromethyl)-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 into the reaction vessel and dissolved. Then, the mixture was stirred at room temperature for 24 hours to carry out a polymerization reaction. Thereafter, it 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.

[0071] [Preparation of Polyimide Solution B] After purging the inside of a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stirrer with nitrogen, 461 g of N,N-dimethylacetamide (DMAC) and 64.0 g (0.200 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB) were placed in 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 stirring was continued for 6 hours while adjusting the temperature to be in the range of 20 to 40 °C to carry out a polymerization reaction, obtaining a viscous polyamic acid solution. Next, 410 g of DMAC was added to the obtained polyamic acid solution for dilution, and then 25.83 g of isoquinoline was added as an imidization accelerator. While stirring the polyamic acid solution, the temperature was maintained in the range of 30 to 40 °C, and 122.5 g (1.20 mol) of acetic anhydride was slowly added dropwise over about 10 minutes as an imidizing agent. Thereafter, the liquid temperature was further maintained at 30 to 40 °C and stirring was continued for 12 hours to carry out a chemical imidization reaction, obtaining a polyimide solution. Next, 1000 g of the obtained polyimide solution containing an imidizing agent and an imidization accelerator was transferred to a reaction vessel equipped with a stirring device and a stirring blade, and while stirring at a speed of 120 rpm, the temperature was maintained at 15 to 25 °C, and 1500 g of methanol was added dropwise at a rate of 10 g / min. When about 800 g of methanol was added, turbidity of the polyimide solution was confirmed, and precipitation of powdery polyimide was confirmed. Subsequently, the entire amount of 1500 g of methanol was added to complete the precipitation of polyimide. Then, the contents of the reaction vessel were filtered off by a suction filtration device and further washed and filtered using 1000 g of methanol. Thereafter, 50 g of the filtered polyimide powder was dried at 50 °C for 24 hours and further dried at 260 °C for 2 hours to remove the remaining volatile components, obtaining a polyimide powder. 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 Polyimide Solution B.

[0072] [Preparation of Polyimide Solution C] While introducing nitrogen gas into a reaction vessel equipped with a nitrogen inlet tube, a Dean-Stark tube, a reflux tube, a thermometer, and a stir bar, 120.5 g (0.485 mol) of 4,4'-diaminodiphenyl sulfone (4,4'-DDS), 51.6 g (0.208 mol) of 3,3'-diaminodiphenyl sulfone (3,3'-DDS), and 500 g of γ-butyrolactone (GBL) were added. Subsequently, 217.1 g (0.700 mol) of 4,4'-oxydiphthalic dianhydride (ODPA), 223 g of GBL, and 260 g of toluene were added at room temperature, and then the internal temperature was raised to 160 °C and heated under reflux at 160 °C for 1 hour to carry out imidization. After completion of imidization, the temperature was raised to 180 °C and the reaction was continued while extracting toluene. After a 12-hour polymerization reaction, the oil bath was removed and the temperature was returned to room temperature, and GBL was added so that the solid content was 20% by mass to obtain polyimide solution C having a reduced viscosity of 2.50 dl / g.

[0073] [Preparation of Polyamic Acid Solution G] After purging the inside of a reaction vessel equipped with a nitrogen inlet tube, a thermometer, and a stir bar 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'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), and 2000 g of N,N-dimethylacetamide were charged and dissolved in the reaction vessel under a nitrogen atmosphere, and then stirred at room temperature for 24 hours to carry out a polymerization reaction. Thereafter, it was diluted with 1000 g of N,N-dimethylacetamide to obtain polyamic acid solution G having a reduced viscosity of 3.50 dl / g.

[0074] [Production Example 1 of Polyimide Film] The polyamic acid solution A was applied using a die coater onto an endless continuous belt made of mirror-finished stainless steel, which is a film production support (coating width: 1240 mm), and dried at 90 to 115°C for 10 minutes. After drying, the self-supporting polyamic acid film (containing 9% by mass of residual solvent) 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 became 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 so that it was within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, the portions with poor flatness at both ends of the film were cut off with a slitter, wound up in a roll shape, and polyimide film 1A shown in Table 1 was obtained. Similarly, the polyamic acid solution A was changed to polyimide solution B or polyamic acid solution G, and the coating thickness on the support was changed to obtain polyimide film 1B or polyimide film 1G shown in Table 1.

[0075] [Production Example 2 of Polyimide Film] Polyamic acid solution A was applied to a polyester film that serves as a film production support, with a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak density (Spd) of 20 per square micrometer or less, and no coating layer on the surface, using a comma coater (coating width 1240 mm), and dried at 90 - 115°C for 10 minutes. After drying, the self-supporting polyamic acid film (containing 10% by mass of residual solvent) was peeled from the support, and both ends were cut to obtain a green film. The obtained green film was conveyed by a pin coater 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. Then, it was cooled to room temperature in 2 minutes, the portions with poor flatness at both ends of the film were cut off with a slitter, wound up in a roll shape, and polyimide film 2A shown in Table 1 was obtained. Similarly, polyamic acid solution A was changed to polyimide solution C or polyamic acid solution G, and the coating thickness on the support was changed to obtain polyimide film 2C or polyimide film 2G shown in Table 1.

[0076] 〔Production Example 3 of Polyimide Film〕 Polyimide solution B was applied using a comma coater to an unstretched polypropylene film which was a film production support and had a surface roughness (Sa) of 3 nm, a maximum protrusion height (Sp) of 12 nm, and a peak density (Spd) of 25 or less per square micrometer (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 stretched 2.8 times in the MD direction using the peripheral speed difference between the two layers simultaneously. Note that the rolls were arranged so that the rolls did not contact the surface of the polyimide film side of the two-layer film between the rolls with a peripheral speed difference. After stretching in the MD direction, both ends of the two-layer film were gripped with a clip tenter, and while being conveyed with a heat treatment at 150 °C for 6 minutes so that the final pinch sheet interval was 1140 mm, that is, a 2.5-fold stretch in the TD direction, and then the polyimide film was peeled from the support of the two-layer film, and further heat-treated at 350 °C for 3 minutes to remove the residual solvent so as to be within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, the portions with poor planarity at both ends of the film were cut off with a slitter, wound up in a roll shape, and polyimide film 3B shown in Table 1 was obtained. Similarly, polyimide solution B was changed to polyimide solution C, and the coating thickness on the support was changed to obtain polyimide film 3C shown in Table 1.

[0077] 〔Production Example 4 of Polyimide Film〕 Polyamic acid solution A was applied using a die coater onto a mirror-finished endless continuous belt made of stainless steel, which was a film production support (coating width: 1240 mm), and dried at 90 - 115°C for 10 minutes. After drying, the self-supporting polyamic acid film (containing 9% by mass of residual solvent) 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 became 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 10 minutes in the third stage to remove the residual solvent so that it was within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, and the portions with poor flatness at both ends of the film were cut off with a slitter and wound up in a roll to obtain the polyimide film 4A shown in Table 1.

[0078] 〔Production Example 5 of Polyimide Film〕 Polyamic acid solution A was applied using a comma coater onto a polyester film, which was a film production support, with 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 (coating width: 1240 mm), and dried at 90 - 115°C for 10 minutes. After drying, the self-supporting polyamic acid film (containing 10% by mass of residual solvent) 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 became 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 10 minutes in the third stage to remove the residual solvent so that it was within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, and the portions with poor flatness at both ends of the film were cut off with a slitter and wound up in a roll to obtain the polyimide film 5A shown in Table 1.

[0079] 〔Production Example 6 of Polyimide Film〕 Polyimide solution C was applied to a polyester film, which was a film production support, having a surface roughness (Sa) of 1 nm, a maximum protrusion height (Sp) of 7 nm, a peak point density (Spd) of 20 per square micrometer or less, and no coating layer on the surface, using a comma coater (coating width 1240 mm), and dried at 90 to 115°C for 10 minutes. After drying, the polyamic acid film that became self-supporting (containing 10% by mass of residual solvent) 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 became 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 1 minute in the third stage to remove the residual solvent so that it was within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, the portions with poor flatness at both ends of the film were cut off with a slitter, wound up in a roll shape, and polyimide film 6C shown in Table 1 was obtained.

[0080] 〔Production Example 7 of Polyimide Film〕 Polyimide solution B was applied to an unstretched polypropylene film with a surface roughness (Sa) of 3 nm, a maximum protrusion height (Sp) of 12 nm, and a peak density (Spd) of 25 per square micrometer or less on the surface of the region, which was the film production support, 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 the support and the polyimide film (containing about 8% by mass of residual solvent). Next, this two-layer film was stretched 2.8 times in the MD direction by utilizing the peripheral speed difference between the two layers simultaneously with a roll. Note that the roll was arranged so that it did not contact the surface of the polyimide film side of the two-layer film between the rolls with a peripheral speed difference. After stretching in the MD direction, both ends of the two-layer film were gripped by a clip tenter, and while being transported at 150 °C with heat treatment so that the final pin sheet interval was 1140 mm, that is, a 2.5-fold stretch in the TD direction, and then the polyimide film was peeled from the support of the two-layer film, and further heat treatment was performed at 350 °C for 1 minute to remove the residual solvent so that it was within a predetermined value range. Then, it was cooled to room temperature in 2 minutes, the portions with poor planarity at both ends of the film were cut off with a slitter, wound up in a roll shape, and polyimide film 7B shown in Table 1 was obtained.

[0081] 〔Preparation of Composition D for Self-Healing Layer Formation〕 A composition for forming a polyurethane acrylate copolymer as a polymer composition having crosslinking points formed by chemical bonds other than covalent bonds was weighed as follows and mixed and prepared at room temperature. AUP-787 (urethane acrylate containing a photoinitiator, manufactured by Tokushiki Co., Ltd.): 100 parts by mass Methyl ethyl ketone: 50 parts by mass Propylene glycol monomethyl ether: 30 parts by mass BYK-381 (surfactant, manufactured by BYK-Chemie Japan): 1 part by mass

[0082] 〔Preparation of Composition E for Self-Healing Layer Formation〕 A composition for forming a cyclodextrin ring-penetrating polyether polymer was weighed as follows and mixed and prepared at room temperature as a polymer composition having crosslinking points composed of constraints depending on a geometric shape not based on chemical bonding. SM3405P (modified polyrotaxane, manufactured by Advanced Soft Materials): 50 parts by mass M-309 (trimethylolpropane triacrylate, manufactured by Toagosei Co., Ltd.): 35 parts by mass M284 (polyethylene glycol diacrylate, manufactured by Toyo Chemicals Co., Ltd.): 15 parts by mass Methyl ethyl ketone: 40 parts by mass Propylene glycol monomethyl ether: 10 parts by mass Omnirad184 (photoinitiator, manufactured by IGM Resins): 4 parts by mass

[0083] [Preparation of Composition F for Forming Hard Coat Layer] A composition for forming a (meth)acrylate copolymer as a polymer composition for forming a hard coat layer was weighed as follows and mixed and prepared at room temperature. OPSTAR Z7530 (mixture of organically modified silica fine particles and polyfunctional acrylate, manufactured by Arakawa Chemical Industries, Ltd.): 100 parts by mass Pentaerythritol triacrylate: 34 parts by mass 1-Hydroxycyclohexyl phenyl ketone: 1.8 parts by mass BYK-300 (leveling agent, manufactured by BYK-Chemie Japan): 0.1 parts by mass Propylene glycol monomethyl ether: 80 parts by mass

[0084] Example 1 <Production of Laminate> On the entire surface of the polyimide film 1A obtained in Production Example 1, the self-healing layer forming composition D was applied by a roll coater. Next, after drying at 80°C, while purging with nitrogen so that the atmosphere had an oxygen concentration of 1.0% by volume or less, the coating layer was cured using an ultraviolet lamp with an illuminance of 100 mW / cm² in the irradiation part and an irradiation dose of 0.3 J / cm², and a laminate having a self-healing layer with a laminate thickness of 22.0 μm and a dry layer thickness of 9.5 μm was prepared.

[0085] Examples 2 to 13 Similarly, laminates were prepared using the polyimide films shown in Table 1 and the self-healing layer forming compositions D and E, 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.

[0086] Comparative Examples 1 to 8 Similarly, laminates were prepared using the polyimide films shown in Table 1 and the self-healing layer forming compositions D, E, and F, and the properties of the laminates were evaluated. The results are shown in Table 3.

[0087]

Table 1

[0088]

Table 2

[0089]

Table 3

Industrial Applicability

[0090] As described above, the laminate of the present invention exhibits excellent transparency, self-healing property, and flexibility, and has excellent adhesion to the self-healing layer, so it is extremely useful for the front panel of an image display device such as a touch panel or a display whose image display part can be folded, and around the electrodes.

Claims

1. A polyimide film having a tensile elastic modulus of 3 GPa or more in both the MD direction and the TD direction, a CTE of -5 ppm / °C to +55 ppm / °C in both the MD direction and the TD direction, and a solvent content of 1.5 to 5.0% by mass, and a self-healing layer formed on at least one surface of the polyimide film, wherein the thickness of the self-healing layer is 5 μm or more, A laminate having a return rate of 80% or more after applying a minute load of 0.5 mN from a Vickers square pyramid indenter to the surface with a micro hardness tester, holding for 5 seconds, unloading to 0.005 mN, and holding for 60 seconds.

2. The laminate according to claim 1, wherein the adhesion rate of the self-healing layer, which is cut in a lattice pattern by the cross-cut method of JIS K5600-5-6 (1999), to the polyimide film is 80% or more.

3. The laminate according to claim 1 or 2, having a yellowness 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.

4. The laminate according to any one of claims 1 to 3, wherein the self-healing layer is a polymer composition containing cross-linking points, and some or all of the cross-linking points are cross-linking points having mobility.

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