Resin composition, and dry film and laminate using the same

Abstract

To provide a resin composition which enables production of a polyimide film having excellent solvent resistance while maintaining characteristics such as low warpage, flexibility and transparency required for applications of a foldable device and the like.SOLUTION: A resin composition contains (A) polyimide having a fluorine content of 25 mass% or less and a YI value of 10 or less when formed into a polyimide single film having thickness of 50 μm, (B) a naphthalene ring-containing epoxy compound, and (C) a compound represented by the following formula (6).SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a resin composition suitable for use in applications such as foldable devices, and to a dry film and a laminate using the same. [Background technology]

[0002] Foldable devices have recently attracted attention as they offer a way to further enhance the portability of mobile information terminals such as smartphones and tablets. Components such as cover windows used in flexible displays that make up such foldable devices must be flexible in addition to transparent. Specifically, there is a demand for components with extremely high flexibility that can be bent 180° with a small bending radius of approximately 2.5 mm.

[0003] In response to this, various materials made of flexible organic polymers have been studied as alternatives to rigid glass. For example, films containing polyimide resins have been studied and proposed as flexible organic polymers from the viewpoints of transparency and heat resistance.

[0004] However, flexible displays using films containing such flexible organic polymers have often suffered from pressure marks or flex marks on the display surface when touched with a finger or a touch pen, or when the display is kept folded for a long period of time. Therefore, films for such flexible displays are required to have not only high flexibility but also a high elastic modulus.

[0005] In response to this, a polyimide resin composition containing a polyimide resin having a specific molecular structure and silica microparticles has been proposed as a film for flexible displays that combines heat resistance, transparency, mechanical strength, surface hardness, and bending resistance (see Patent Document 1).

[0006] Incidentally, not only the above-mentioned portable information terminals but also image display devices such as liquid crystal display devices and organic EL display devices generally have a hard coat layer formed on the display device surface to impart scratch resistance so as to prevent scratches on the image display surface during handling. Such hard coat layers must satisfy various required properties, such as scratch resistance, hardness, and transparency, and various compositions for forming hard coat layers have been investigated. For example, a composition in which ultrafine silica particles are added to an ultraviolet-curable acrylate has been proposed (see Patent Document 2, etc.). Hard coat layers using these compositions are formed by applying them to the surface of the display device to form a cured film. Therefore, in consideration of application properties, etc., ether alcohols such as 1-methoxy-2-propanol or esters such as ethyl acetate are generally used as solvents for hard coat layer-forming compositions. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2016 / 060213 Brochure [Patent Document 2] Japanese Patent Application Laid-Open No. 2012-252275 Summary of the Invention [Problem to be solved by the invention]

[0008] Even when a polyimide film such as that described in Patent Document 1 is used for a cover window of a display element, it is preferable to provide a hard coat layer from the viewpoint of surface protection. However, when a composition for forming a hard coat layer is applied to the surface of a polyimide film, not only is the transparency of the polyimide film impaired and the surface hardness of the polyimide film reduced, but cracks are also generated in the polyimide film, which can reduce adhesion to a transparent substrate (e.g., ultra-thin glass) to which the polyimide film is attached.

[0009] Therefore, a primary object of the present invention is to provide a resin composition that can provide a polyimide film having excellent solvent resistance while maintaining properties such as low warpage, flexibility, and transparency required for applications such as foldable devices, etc. Another object of the present invention is to provide a dry film and a laminate using the resin composition. [Means for solving the problem]

[0010] The present inventors have intensively investigated the possibility that one of the causes of the deterioration of transparency, surface hardness, adhesion, etc. of polyimide films is the solvent contained in the composition for forming a hard coat layer, and have found that the above problem can be solved by adding a specific epoxy resin and a compound having a specific structure containing two or more methylol groups or methoxymethyl groups to a specific polyimide resin. The present invention has been completed based on this finding. The gist of the present invention is as follows.

[0011] [1] (A) A polyimide having a fluorine content of 25% by mass or less and a YI value of 10 or less when made into a polyimide film having a thickness of 50 μm; (B) a naphthalene ring-containing epoxy compound, and (C) Formula (6): [ka] (In the formula, R 1 ~R 6 each independently represents a methylol group, an alkoxymethyl group containing an alkoxy group having 1 to 4 carbon atoms, or a hydrogen atom, provided that at least two of them are methylol groups or alkoxy groups having 1 to 4 carbon atoms. A compound represented by A resin composition comprising: [2] The resin composition according to [1], wherein the (B) naphthalene ring-containing epoxy compound is contained in an amount of 10 to 50 mass % based on the total mass of the resin composition. [3] The resin composition according to [1] or [2], wherein the compound (C) represented by formula (6) is contained in an amount of 5 to 20 mass % based on the total mass of the resin composition. [4] A dry film comprising a substrate and a dry film peelably disposed on the substrate, wherein the dry film is a coating film of a resin composition described in any one of claims 1 to 3. [5] A laminate comprising a glass substrate, a resin layer provided on one of the main surfaces of the glass substrate so as to be in contact with the surface, and a hard coat layer provided on the resin layer, The resin layer is a laminate comprising a cured film of the resin composition according to any one of [1] to [3], or a dried film of the dry film according to [4]. [6] The laminate according to claim 5, which is used as a cover window for a flexible display element. [Effects of the Invention]

[0012] According to the present invention, by adding a specific epoxy resin and a compound having a specific structure containing two or more methylol groups or methoxymethyl groups to a polyimide having a fluorine content of 25% by mass or less and a YI value of 10 or less, it is possible to provide a resin composition that can produce a polyimide film having excellent solvent resistance while maintaining properties such as low warpage, flexibility, and transparency required for applications such as foldable devices.

[0013] [Resin composition] The resin composition according to the present invention contains, as essential components, (A) a polyimide having a fluorine content of 25% by mass or less and having a YI value of 10 or less when formed into a 50 μm-thick polyimide film, (B) a naphthalene ring-containing epoxy compound, and (C) a compound represented by the above formula (I). The components constituting the resin composition are described in detail below.

[0014] <(A) Polyimide> The polyimide contained in the resin composition of the present invention has a structure represented by the following formula (1) in which a polyamic acid, which is a reaction product of a carboxylic acid anhydride and a diamine, is imidized. The constitutional unit represented by the following formula (1) is a constitutional unit formed by the reaction of a tetracarboxylic acid compound with a diamine compound.

[0015] [ka]

[0016] In the formula (II), X's each independently represent a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably a divalent organic group having a cyclic structure having 4 to 40 carbon atoms. Examples of the cyclic structure include an alicyclic, aromatic ring, and heterocyclic structure. The organic group may have a hydrogen atom substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the hydrocarbon group or the fluorine-substituted hydrocarbon group preferably has 1 to 8 carbon atoms. However, even in the case of fluorine substitution, the fluorine content of the polyimide must be 25 mass% or less. If the fluorine content increases, the optical properties of the polyimide (light transmittance, YI value, haze) improve, but the adhesion to the glass substrate cannot be maintained.

[0017] Furthermore, the polyimide contained in the resin composition of the present invention must have a fluorine content of 25% by mass or less and, in addition, a YI value of 10 or less when formed into a 50 μm-thick polyimide film. As described above, even if the fluorine content is 25% by mass or less, a polyimide having a YI value of 10 or less is used. That is, in the present invention, various polyimides can be used without particular limitation as long as the fluorine content is 25% by mass or less and the YI value is 10 or less. For example, in an embodiment of the present invention, the polyimide may contain multiple types of X, and the multiple types of X may be the same or different from one another. Examples of X include groups represented by the following formulae, in which the hydrogen atoms in each group are substituted with methyl, fluoro, chloro or trifluoromethyl groups, and chain hydrocarbon groups having 6 or less carbon atoms.

[0018] [ka]

[0019] In the above formula, * represents a bond, and A 1 , A 2 , A 3 are each independently a single bond, -O-, -S-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -SO2-, -CO-, or N(Q)-, where Q is a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. As an example, A 1 and A 3 is a single bond, -O- or -S-, and A 2 is -CH2-, -C(CH3)2-, -C(CF3)2- or SO2-. A 1 and A 2 The bonding positions of each ring and A 2 and A 3 The bonding positions of the and to each ring are, independently of each other, preferably meta or para positions relative to each ring, more preferably para positions.

[0020] Among the above groups, groups represented by the following formula are more preferred from the viewpoint of the surface hardness and flex resistance of the laminate. [ka]

[0021] Also, A 1 , A 2 and A 3 are preferably each independently a single bond, —O— or —S—, more preferably a single bond or O—, from the viewpoint of easily increasing the surface hardness and flexibility of the laminate.

[0022] In a preferred embodiment of the present invention, at least some of the multiple Xs in the above formula (1) are constitutional units represented by formula (2). [ka]

[0023] In formula (2), * represents a bond, and R1 ~R 8 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R 1 ~R 8 The hydrogen atoms contained in may be substituted with halogen atoms independently of each other.

[0024] R 1 ~R 8 are each independently preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, and R 1 ~R 8 The hydrogen atoms contained in R may be substituted with halogen atoms, independently of one another. Examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, and iodine atoms. 1 ~R 8 are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, from the viewpoint of the surface hardness, transparency and flex resistance of the laminate, and particularly preferably R 1 , R 3 , R 4 , R 5 , R 6 , R 8 is a hydrogen atom, R 2 and R 7 is a hydrogen atom, a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group, and particularly preferably R 2 and R 7 is a methyl group or a trifluoromethyl group. However, the fluorine content of the entire polyimide must be 25 mass % or less.

[0025] In a preferred embodiment of the present invention, the structural unit represented by the formula (2) is a structural unit represented by the formula (3). That is, at least a portion of the multiple X's are structural units represented by the formula (3). In this case, the fluorine-containing skeleton increases the solubility of the polyimide in solvents, which facilitates improving the storage stability of a varnish containing the polyimide, as well as reducing the viscosity of the varnish and improving the coatability when forming a dry film. Furthermore, the fluorine-containing skeleton improves the optical properties of the polyimide (total light transmittance, YI value, haze, etc.). However, from the viewpoint of adhesion to a glass substrate, the fluorine content of the polyimide as a whole needs to be 25% by mass or less.

[0026] [ka]

[0027] In one embodiment of the present invention, X in the polyimide is preferably 30 mol % or more, more preferably 50 mol % or more, and even more preferably 70 mol % or more, represented by formula (2), particularly formula (3). When X in the polyimide is represented by formula (2), particularly formula (3), within the above range, the fluorine-containing skeleton tends to improve the solubility in solvents, which tends to improve the storage stability of a varnish containing the polyimide, and also tends to reduce the viscosity of the varnish, improving its coatability. Furthermore, the fluorine-containing skeleton also improves optical properties such as total light transmittance, YI value, and haze. The proportion of the structural unit represented by formula (2) or (3) in X in the polyimide can be, for example, 1 It can be measured using H-NMR, but it can also be calculated from the ratio of raw materials used.

[0028] In the above formula (1), Y represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms, and more preferably a tetravalent organic group having 4 to 40 carbon atoms and a cyclic structure. Examples of the cyclic structure include an alicyclic, aromatic ring, and heterocyclic structure. The organic group is an organic group in which a hydrogen atom may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8.

[0029] In one embodiment of the present invention, the polyimide may contain multiple types of Y, which may be the same or different from one another. Y is preferably a group represented by the following formula: Examples of these exemplified groups include groups in which a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group; and tetravalent chain hydrocarbon groups having 6 or less carbon atoms.

[0030] [ka]

[0031] In the above formula, * represents a bond, B 1 represents a single bond, -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2-, -C(CF3)2-, -Ar-, -SO2-, -CO-, -O-Ar-O-, -Ar-O-Ar-, -Ar-CH2-Ar-, -Ar-C(CH3)2-Ar-, or Ar-SO2-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and a specific example is a phenylene group.

[0032] Among the above groups, as a means for making the YI value of the polyimide 10 or less, and from the viewpoint of the surface hardness and flex resistance of the laminate, a single bond, -O-, -CH2-, -CH2-CH2-, -CH(CH3)-, -C(CH3)2- or C(CF3)2- are preferred, a single bond, -O-, -CH2-, -CH(CH3)-, -C(CH3)2- or C(CF3)2- are more preferred, and a single bond, -C(CH 3 )2- or C(CF3)2-.

[0033] [ka]

[0034] In one embodiment of the present invention, at least some of the multiple Ys in formula (1) are structural units represented by the following formula (4). When at least some of the multiple Ys in formula (1) are groups represented by the following formula (4), the solubility of the polyimide in a solvent is increased, the viscosity of a varnish containing the polyimide is easily reduced, and the coatability is improved. In addition, the optical properties of the laminate are improved.

[0035] [ka]

[0036] In formula (4), * represents a bond, and R 9 ~R 16 are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; R 9 ~R 16 The hydrogen atoms contained in may be independently substituted with halogen atoms, such as fluorine, chlorine, bromine, and iodine atoms.

[0037] As a means for making the YI value of polyimide 10 or less, and also from the viewpoint of easily improving the surface hardness, flex resistance, and transparency of the laminate, R 9 ~R 16are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, and particularly preferably R 9 , R 10 , R 11 , R 14 , R 15 and R 16 is a hydrogen atom, R 12 and R 13 is a hydrogen atom, a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group, and particularly preferably R 12 and R 13 is a methyl group or a trifluoromethyl group.

[0038] In one embodiment of the present invention, the structural unit represented by the above formula (4) is preferably a group represented by the following formula (5). The fluorine-containing skeleton increases the solubility of the polyimide in a solvent, which facilitates improving the storage stability of a varnish containing the polyimide, and also facilitates reducing the viscosity of the varnish, improving its coatability. Furthermore, the fluorine-containing skeleton improves the optical properties of the laminate.

[0039] [ka]

[0040] In one embodiment of the present invention, it is preferable that the polyimide is one in which Y in formula (1) is preferably 50 mol % or more, more preferably 60 mol % or more, and even more preferably 70 mol % or more, represented by the above formula (4), particularly the above formula (5). Polyimides in which Y within the above range is represented by the above formula (4), particularly the above formula (5), have a fluorine-containing skeleton that enhances the solubility of the polyimide in solvents, making it easy to reduce the viscosity of varnishes containing the resin and improving the processability of dry films and laminates. Furthermore, the fluorine-containing skeleton makes it easy to improve the optical properties of laminates. However, from the viewpoint of adhesion to glass substrates, it is necessary to adjust the fluorine content of the polyimide as a whole to 25 mass % or less. The proportion of the structural unit of Y represented by formula (4) in the polyimide can be, for example, 1It can be measured using H-NMR, but it can also be calculated from the ratio of raw materials used.

[0041] The above polyimide can contain a constitutional unit represented by formula (30) and / or a constitutional unit represented by formula (31) in addition to the constitutional unit represented by formula (1).

[0042] [ka]

[0043] In equation (30), Y 1 is a tetravalent organic group, preferably an organic group in which a hydrogen atom may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. 1 Examples of the Y groups include the above-mentioned preferred groups for Y. In one embodiment of the present invention, the polyimide contains a plurality of Y groups. 1 may contain multiple types of Y 1 may be the same or different from each other.

[0044] In equation (31), Y 2 is a trivalent organic group, preferably an organic group in which a hydrogen atom may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. 2 Examples of the Y include a group in which one of the bonds of the above-mentioned preferred groups for Y is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. 2 may contain multiple types of Y 2 may be the same or different from each other.

[0045] In formula (30) and formula (31), X 1 and X 2 are each independently a divalent organic group, preferably an organic group in which a hydrogen atom may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. 1 and X 2Examples of the group include the preferred groups for X described above.

[0046] In one embodiment of the present invention, the polyimide comprises a structural unit represented by formula (1), and optionally a structural unit represented by formula (30) and / or formula (31). From the viewpoint of the optical properties, surface hardness, and flex resistance of the laminate, the structural unit represented by formula (1) in the polyimide is preferably 80 mol % or more, more preferably 90 mol % or more, and even more preferably 95 mol % or more, based on all structural units represented by formula (1), and optionally formula (30) and formula (31). In the polyimide, the structural unit represented by formula (1) is usually 100% or less, based on all structural units represented by formula (1), and optionally formula (30) and / or formula (31). The above ratio can be expressed, for example, as follows: 1 It can be measured using H-NMR, or can be calculated from the ratio of raw materials used.

[0047] In one embodiment of the present invention, in view of the adhesion between the resin layer and the glass substrate and the texture of the laminate, the polyimide may contain a structural unit represented by the following formula (40) in addition to the structural unit represented by formula (1) and, in some cases, the structural unit represented by formula (30) and / or formula (31).

[0048] [ka]

[0049] In the above formula (40), * represents a bond, and R 17 and R 18 are each independently a single bond, an alkylene group having 1 to 5 carbon atoms, or a divalent aromatic group having 6 or more carbon atoms, and R 19 and R 20 are each independently an alkyl group having 1 to 5 carbon atoms, and R 21 and R 22 are each independently an aryl group having 4 to 10 carbon atoms, and R 23 and R 24At least one of these is an alkenyl group having 2 to 10 carbon atoms, and m1, m2 and m3 are each independently an integer of 1 or greater.

[0050] The repeating unit having the structure of the above formula (40) contains a repeating unit substituted with an alkyl group, a siloxane repeating unit substituted with an aryl group, and a siloxane repeating unit substituted with an alkenyl group, thereby improving the tensile modulus of the resin layer, as well as the adhesion between the resin layer and the glass substrate, and also improving the texture of the laminate when formed.

[0051] The order of the repeating units substituted with an alkyl group, the siloxane repeating units substituted with an aryl group, and the siloxane repeating units substituted with an alkenyl group can be changed as desired, and they may be positioned alternately.

[0052] In one embodiment of the present invention, in the structural unit represented by the above formula (40), R 17 and R 18 are each independently a single bond, an alkylene group having 1 to 5 carbon atoms, or a divalent aromatic group having 6 or more carbon atoms, and preferably an alkylene group having 3 or more carbon atoms. R3 and R4 are each independently an alkyl group having 1 to 5 carbon atoms, and preferably a methyl or ethyl group. Also, R 19 and R 20 are each independently an aryl group having 4 to 10 carbon atoms, and preferably a phenyl group. Also, R 21 and R 22 At least one of them is an alkenyl group having 2 to 10 carbon atoms, and is preferably an ethenyl or propenyl group. The other group that is not an alkenyl group is an alkyl group having 1 to 5 carbon atoms.

[0053] In one embodiment of the present invention, in the structural unit represented by the above formula (40), m1, m2, and m3 are each independently an integer of 1 to 10; specifically, m1 is an integer of 3 to 9, m2 is an integer of 2 to 9, and m3 is an integer of 1 to 5.

[0054] In one embodiment of the present invention, the structural unit represented by the above formula (40) accounts for 5 mol % or more or 50 mol % or less, preferably 5 to 40 mol %, of all units, from the viewpoint of the balance between heat resistance and adhesion.

[0055] The polyimide may contain halogen atoms such as fluorine atoms, which can be introduced, for example, by the above-mentioned fluorine-containing substituents, but the fluorine content of the polyimide must be 25% by mass or less. If the polyimide contains fluorine atoms, the optical properties (light transmittance, YI value, haze) of the resin layer are improved, but the adhesion to the glass substrate is reduced. The fluorine atom content in the polyimide is preferably 0 to 23% by mass, more preferably 0 to 20% by mass.

[0056] The imidization ratio of the polyimide is preferably 90% or more, more preferably 93% or more, and even more preferably 96% or more. From the viewpoint of easily improving the optical homogeneity of the laminate, it is preferable that the imidization ratio is equal to or greater than the above lower limit. Furthermore, the upper limit of the imidization ratio is 100% or less. The imidization ratio indicates the ratio of the molar amount of imide bonds in the polyimide to twice the molar amount of structural units derived from tetracarboxylic acid compounds in the polyimide. Note that, when the polyimide contains a tricarboxylic acid compound, it indicates the ratio of the molar amount of imide bonds in the polyimide to the sum of twice the molar amount of structural units derived from tetracarboxylic acid compounds in the polyimide and the molar amount of structural units derived from tricarboxylic acid compounds. Furthermore, the imidization ratio can be determined by IR method, NMR method, etc.

[0057] Polyimide can be produced using, for example, a tetracarboxylic acid compound and a diamine compound as main raw materials. Note that a diisocyanate compound may be used instead of the diamine compound.

[0058] Examples of diamine compounds used in the production of polyimides include aliphatic diamines, aromatic diamines, diaminosiloxanes, and mixtures thereof. In this embodiment, "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents as part of its structure. The aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Of these, a benzene ring is preferred. Furthermore, "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents as part of its structure. Furthermore, "diaminosiloxane" refers to a compound having an amino group at the end of a siloxane skeleton, and may have a hydrocarbon group substituted as part of its structure.

[0059] Examples of aliphatic diamines include acyclic aliphatic diamines such as hexamethylenediamine, and cyclic aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, and 4,4'-diaminodicyclohexylmethane. These can be used alone or in combination of two or more.

[0060] Examples of aromatic diamines include aromatic diamines having one aromatic ring, such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, and 3,3'-diaminodiphenyl sulfone (sometimes abbreviated as 3,3'DDS); 1,4-bis(4-aminophenoxy)benzene; 1,3-bis(4-aminophenoxy)benzene (sometimes abbreviated as TPE-R); and 1,3-bis(3-aminophenoxy)benzene. Examples of aromatic diamines having two or more aromatic rings include aromatic diamines having two or more aromatic rings, such as 2,2-bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (sometimes referred to as TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene, 9,9-bis(4-amino-3-chlorophenyl)fluorene, and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These may be used alone or in combination of two or more.

[0061] The aromatic diamine is preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone (3,3'DDS), 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), 1,3-bis(3-aminophenoxy)benzene These include 4,4'-benzene (APB-N), bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), and 4,4'-bis(4-aminophenoxy)biphenyl. These can be used alone or in combination of two or more.

[0062] Examples of diaminosiloxanes include 1,3-bis(3-aminopropyl)tetramethyldisiloxane, 1,3-bis(4-aminobutyl)tetramethyldisiloxane, α,ω-bis(2-aminoethyl)polydimethylsiloxane, α,ω-bis(3-aminopropyl)polydimethylsiloxane, α,ω-bis(4-aminobutyl)polydimethylsiloxane, α,ω-bis(5-aminopentyl)polydimethylsiloxane, α,ω-bis[3-(2-aminophenyl)propyl]polydimethylsiloxane, and α,ω-bis[3-(4-aminophenyl)propyl]polydimethylsiloxane. These can be used alone or in combination of two or more.

[0063] Among the above diamine compounds, from the viewpoint of the surface hardness, flexibility, and degree of coloring (YI value) of the laminate, it is preferable to use one or more selected from the group consisting of aromatic diamines having a biphenyl structure, and among these, it is more preferable to use one or more selected from the group consisting of 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)benzidine, 4,4'-bis(4-aminophenoxy)biphenyl, and 4,4'-diaminodiphenyl ether, and it is even more preferable to use 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB).

[0064] Furthermore, from the viewpoint of the flexibility of the laminate, it is preferable to use one or more selected from the group consisting of aromatic diamines having an ether bond, and among these, it is more preferable to use one or more selected from the group consisting of 4,4'-diaminodiphenyl ether, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene (TPE-R), and 1,3-bis(3-aminophenoxy)benzene (APB-N), and it is even more preferable to use 1,3-bis(4-aminophenoxy)benzene (TPE-R) and 1,3-bis(3-aminophenoxy)benzene (APB-N).

[0065] From the viewpoint of the transparency of the laminate, it is preferable to use one or more selected from the group consisting of aromatic diamines having a sulfone bond, and among these, it is more preferable to use one or more selected from the group consisting of 3,3'-diaminodiphenyl sulfone (3,3'DDS) and bis[4-(4-aminophenoxy)phenyl]sulfone, and it is even more preferable to use 3,3'-diaminodiphenyl sulfone (3,3'DDS).

[0066] Examples of tetracarboxylic acid compounds used in the production of polyimides include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic acid dianhydrides, and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic acid dianhydrides. The tetracarboxylic acid compounds may be used alone or in combination of two or more. The tetracarboxylic acid compounds may be dianhydrides or tetracarboxylic acid compound analogs such as acid chloride compounds.

[0067] Specific examples of the aromatic tetracarboxylic acid dianhydride include non-condensed polycyclic aromatic tetracarboxylic acid dianhydrides, monocyclic aromatic tetracarboxylic acid dianhydrides, and condensed polycyclic aromatic tetracarboxylic acid dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic dianhydride (s-ODPA), 3,4'-oxydiphthalic dianhydride (a-ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenyl)] [hexafluoroisopropylidene]diphthalic dianhydride (sometimes abbreviated as 6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic dianhydride. Furthermore, an example of a monocyclic aromatic tetracarboxylic dianhydride is 1,2,4,5-benzenetetracarboxylic dianhydride, and an example of a condensed polycyclic aromatic tetracarboxylic dianhydride is 2,3,6,7-naphthalenetetracarboxylic dianhydride.

[0068] Among the above, 4,4'-oxydiphthalic dianhydride (s-ODPA), 3,4'-oxydiphthalic dianhydride (a-ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, and 3,3',4,4'-diphenylsulfone are preferred. Tetracarboxylic acid dianhydrides, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxyphenyl)]propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride and 4,4'-(m-phenylenedioxy)diphthalic dianhydride are more preferred. Examples of suitable diphthalic dianhydrides include s-ODPA, 3,4'-oxydiphthalic dianhydride (a-ODPA), 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), bis(3,4-dicarboxyphenyl)methane dianhydride, and 4,4'-(p-phenylenedioxy)diphthalic dianhydride. These may be used alone or in combination of two or more.

[0069] Examples of aliphatic tetracarboxylic acid dianhydrides include cyclic and acyclic aliphatic tetracarboxylic acid dianhydrides. Cyclic aliphatic tetracarboxylic acid dianhydrides are tetracarboxylic acid dianhydrides having an alicyclic hydrocarbon structure, and specific examples include cycloalkane tetracarboxylic acid dianhydrides such as 1,2,4,5-cyclohexane tetracarboxylic acid dianhydride, 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride, and 1,2,3,4-cyclopentane tetracarboxylic acid dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride, 3,3',4,4'-dicyclohexyl tetracarboxylic acid dianhydride (HBPDA), and positional isomers thereof. These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride, which can be used alone or in combination of two or more. Also, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride can be used in combination.

[0070] Among the above-mentioned tetracarboxylic dianhydrides, 4,4'-oxydiphthalic dianhydride (s-ODPA), 3,4'-oxydiphthalic dianhydride (a-ODPA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, and 2,2',3,3'-biphenyltetracarboxylic dianhydride are preferred as a means for making the YI value of polyimide 10 or less, and also from the viewpoint of high surface hardness, high transparency, high flexibility, and high flex resistance of the laminate. Preferred are 3,3',4,4'-dicyclohexyltetracarboxylic dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 3,3',4,4'-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis[4-(3,4-dicarboxyphenoxyphenyl)]propane dianhydride, 3,3',4,4'-dicyclohexyltetracarboxylic dianhydride (HBPDA), and mixtures thereof.

[0071] The dicarboxylic acid compound used in the production of polyimide is preferably terephthalic acid, 4,4'-oxybisbenzoic acid, or an acid chloride compound thereof. In addition to terephthalic acid, 4,4'-oxybisbenzoic acid, or an acid chloride compound thereof, other dicarboxylic acid compounds may be used. Examples of other dicarboxylic acid compounds include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their related acid chloride compounds, acid anhydrides, etc., and two or more of these may be used in combination.

[0072] Specific examples include dicarboxylic acid compounds such as isophthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, and chain hydrocarbons having 8 or less carbon atoms, as well as compounds in which two benzoic acids are linked by a single bond, -CH2-, -C(CH3)2-, -SO2-, or a phenylene group, and acid chloride compounds thereof. Specific examples are preferably 4,4'-oxybis(benzoyl chloride) and terephthaloyl chloride, and more preferably a combination of 4,4'-oxybis(benzoyl chloride) and terephthaloyl chloride.

[0073] The polyimide may be obtained by further reacting the above-mentioned tetracarboxylic acid compound with tetracarboxylic acids, tricarboxylic acids, and their anhydrides and derivatives, as long as the various physical properties of the laminate are not impaired. Examples of tetracarboxylic acids include water adducts of the anhydrides of the above-mentioned tetracarboxylic acid compounds. Examples of tricarboxylic acid compounds include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and their related acid chloride compounds and acid anhydrides, and two or more of these may be used in combination. Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic-2,3-anhydride; and compounds in which phthalic anhydride and benzoic acid are linked via a single bond, -O-, -CH2-, -C(CH3)2-, -SO2-, or a phenylene group.

[0074] In producing the polyimide, the amounts of the diamine compound, tetracarboxylic acid compound and / or dicarboxylic acid compound used can be appropriately selected depending on the ratio of each of the desired structural units of the polyimide.

[0075] In producing a polyimide, the reaction temperature of the diamine compound, tetracarboxylic acid compound, and dicarboxylic acid compound is not particularly limited, but is, for example, 5 to 350°C, preferably 20 to 200°C, and more preferably 25 to 100°C. The reaction time is also not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out in an inert atmosphere or under reduced pressure. In a preferred embodiment, the reaction is carried out under normal pressure and / or an inert gas atmosphere with stirring. The reaction is also preferably carried out in a solvent inert to the reaction.

[0076] The solvent is not particularly limited as long as it does not affect the reaction, and examples thereof include alcohol solvents such as water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, 2-butoxyethanol, and propylene glycol monomethyl ether; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone, γ-valerolactone, propylene glycol methyl ether acetate, and ethyl lactate; acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, Examples of suitable solvents include ketone solvents such as methyl isobutyl ketone and N-methyl-2-pyrrolidone; aliphatic hydrocarbon solvents such as pentane, hexane, and heptane; alicyclic hydrocarbon solvents such as ethylcyclohexane; aromatic hydrocarbon solvents such as toluene and xylene; nitrile solvents such as acetonitrile; ether solvents such as tetrahydrofuran and dimethoxyethane; chlorine-containing solvents such as chloroform and chlorobenzene; amide solvents such as N,N-dimethylacetamide and N,N-dimethylformamide; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations (mixed solvents) thereof. Among these, amide solvents are preferred from the viewpoint of solubility.

[0077] The imidization step in the production of polyimides can be carried out in the presence of an imidization catalyst. Examples of imidization catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; alicyclic amines (monocyclic) such as N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydroazepine; and azabicyclo[2.2.1]heptane, azabicyclo[3.2.1]octane, azabicyclo[2.2.2]octane, and azabicyclo[3.2.1]octane. 2] Alicyclic amines (polycyclic) such as nonane; and aromatic amines such as pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and isoquinoline.

[0078] In addition, from the viewpoint of facilitating the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of the acid anhydride include conventional acid anhydrides used in imidization reactions, and specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic acid.

[0079] The polyimide may be isolated (separated and purified) by a conventional method, for example, a separation means such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination of these. In a preferred embodiment, the polyimide can be isolated by adding a large amount of alcohol such as methanol to a reaction solution containing a transparent polyamideimide resin to precipitate the resin, followed by concentration, filtration, drying, etc.

[0080] The weight-average molecular weight (Mw) of the polyimide obtained as described above is preferably 30,000 to 1,000,000, more preferably 70,000 to 700,000, and even more preferably 100,000 to 500,000, from the viewpoints of solubility in solvents when producing a dry film and the surface hardness and flex resistance of the resin layer when using the dry film for optical applications. The weight-average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and calculated in terms of standard polystyrene.

[0081] In the present invention, the polyimide described above has a YI value of 7.0 or less when formed into a 50 μm-thick single film. By using a polyimide with a small YI value, a laminate produced using the dry film can be suitably used as a cover window for a display for a flexible device. A YI value of 5.0 or less is more preferable, and a YI value of 2.0 or less is particularly preferable. In this specification, the YI value (yellowness index) refers to a value calculated based on the formula YI=100×(1.2769X−1.0592Z) / Y, obtained by measuring the transmittance of light from 300 to 800 nm using a UV-Vis-Near-Infrared Spectrophotometer in accordance with JIS K 7373:2006, and determining the tristimulus values ​​(X, Y, Z). Alternatively, a 50 μm-thick single film can be formed by adding dimethylacetamide as a solvent so that the final coating thickness is 50 μm, applying the diluted polyimide varnish onto a substrate, drying the coating at 80°C for 30 minutes to 4 hours to remove the solvent, and peeling it off from the substrate.

[0082] In the present invention, when the polyimide is formed into a single film having a thickness of 50 μm or less, the haze of the single film is preferably 5.0 or less. By using a polyimide with a low haze in addition to a low YI value, a laminate produced using the dry film can be more suitably used as a cover window for a display for a flexible device. A haze of 2.0 or less is more preferable. In this specification, haze refers to a value measured using a known turbidimeter in accordance with JIS K 7136:2000.

[0083] In the present invention, when the polyimide is formed into a single film having a thickness of 50 μm, the single film preferably has a total light transmittance of 88% or more. A total light transmittance of 88% or more allows the laminate to be suitably used as a cover window for a display for a flexible device. A total light transmittance of 90% or more is more preferable. In this specification, the total light transmittance refers to a value measured using a known turbidimeter in accordance with JIS K 7375:2008.

[0084] The above-mentioned YI value and total light transmittance of the polyimide are values ​​for a 50 μm-thick monolayer film, but the thickness of the coating film may be adjusted so that the final film thickness is 50 μm when preparing the polyimide monolayer film, or a polyimide monolayer film of any thickness may be prepared, the YI value and total light transmittance of the monolayer film measured, and each measured value normalized by the film thickness (50 μm thickness). Specifically, when the YI value of a polyimide monolayer film of any thickness (t μm) is YI(t) and the total light transmittance is T(t), the YI(50) and total light transmittance (T50) for a 50 μm monolayer film can be calculated using the following formulas. YI(50)=YI(t)×t / 50 T(50)=T(t)×t / 50

[0085] <(B) Epoxy Compound> The resin composition of the present invention contains a specific epoxy compound in addition to the polyimide having a fluorine content of a certain value or less and a YI value of 10 or less. A naphthalene ring-containing epoxy compound is used as the epoxy compound used in combination with the polyimide. By using such a specific epoxy compound in combination with a crosslinking agent described below, it is possible to improve solvent resistance and adhesion while maintaining the properties of the polyimide, such as low warpage, flexibility, and transparency. While the reason for this is unclear, it is thought that the hydroxyl groups present on the surface of the glass substrate react with the epoxy groups in the resin composition of the present invention to improve adhesion. In particular, the naphthalene ring-containing epoxy compound is thought to have excellent resistance to solvents contained in hard coat materials, significantly preventing cracking of the resin layer and a decrease in adhesion to the glass substrate.

[0086] As the naphthalene ring-containing epoxy compound, a glycidyl ether of an alkylene oxide adduct of a polyhydric phenol containing a naphthalene ring can be preferably used. Among these, in the present invention, it is preferable to use a naphthalene ring-containing epoxy compound having two or more glycidyl groups in one molecule.

[0087] Examples of naphthalene ring-containing epoxy compounds include those represented by the following formula: [ka] In the above formula, each R independently represents hydrogen or a hydrocarbon group having 1 to 5 carbon atoms.

[0088] The naphthalene ring-containing epoxy compound may be a commercially available product, such as HP4032, HP-4700 (both manufactured by DIC Corporation), ESN-355, ESN-375 (manufactured by Tohto Kasei Co., Ltd.), and NC-7300 (manufactured by Nippon Kayaku Co., Ltd.).

[0089] The amount of (B) epoxy compound is preferably 10 to 50 mass % and more preferably 10 to 30 mass % of the total resin composition, from the viewpoints of the chemical resistance of the resin composition, adhesion to a substrate, and surface hardness when the resin composition is formed into a film.

[0090] <(C) Compound represented by formula (6)> The resin composition according to the present invention can further improve solvent resistance by including a compound represented by the following formula (6) in addition to the above-described epoxy resin (B). The reason for this is not clear, but it is thought that the triazine ring structure as represented by the following formula (6) promotes the reaction of the epoxy compound, and that self-polymerization by the methylol group or methoxymethyl group improves the crosslink density of the cured film.

[0091] [ka]

[0092] In the formula, R 1 ~R 6 each independently represents a methylol group, an alkoxymethyl group including an alkoxy group having 1 to 4 carbon atoms, or a hydrogen atom, provided that at least two of them are methylol groups or alkoxy groups having 1 to 4 carbon atoms.

[0093] The above compounds can be obtained by known methods, for example, by modifying a melamine monomer by methylolating it with formalin, or by further modifying it by alkoxylating it with an alcohol.

[0094] Examples of the compound represented by the above formula include hexamethylol melamine, hexabutyrol melamine, hexakis(methoxymethyl)melamine, partially methylolated melamine, partially methoxymethylated melamine, and alkylated products thereof, tetramethylol benzoguanamine, partially methylolated benzoguanamine, partially methylolated benzoguanamine, and alkylated products thereof.

[0095] Commercially available melamine resins include "Nicalac" (manufactured by Sanwa Chemical Co., Ltd.) MW-30HM, MW-390, MW-100LM, MX-750LM, MW-30M, MW-30, MW-22, MS-21, MS-11, MW-24X, MS-001, MX-002, MX-730, MX750, MX-708, MX-706, MX-042, MX-45, MX-500, MX-520, MX-43, MX-417, and MX-410, and "Cymel" (manufactured by Allnex Corporation) 232, 235, 236, 238, 285, 300, 301, 303, 350, and 370.

[0096] The amount of the compound represented by the formula (6) is preferably 5 to 20% by mass, more preferably 5 to 10% by mass, relative to the epoxy compound (B) described above, from the viewpoints of the chemical resistance of the resin composition, adhesion to a substrate, and surface hardness when the resin composition is formed into a film.

[0097] <Solvent> In consideration of the formability of the resin layer, the resin composition preferably contains a solvent. Any solvent can be used without particular limitation as long as it can dissolve the polyimide and the epoxy compound, but from the viewpoints of the coatability of the varnish and the transparency of the resulting resin layer, a solvent containing at least one selected from the group consisting of an ester group, an ether group, a ketone group, a hydroxyl group, a sulfone group, and a sulfinyl group is preferred.

[0098] Examples of the solvent having an ester group include ester-based solvents such as methyl acetate, ethyl acetate, butyl acetate, and dimethyl carbonate. Examples of solvents having a cyclic ester group include lactone solvents such as γ-butyrolactone (GBL), δ-valerolactone, ε-caprolactone, γ-crotonolactone, γ-hexanolactone, α-methyl-γ-butyrolactone, γ-valerolactone, α-acetyl-γ-butyrolactone, and δ-hexanolactone. Examples of solvents having an ether group include tetrahydrofuran, dioxane, and dibutyl ether. Examples of the solvent having a ketone group include ketone-based solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone. Examples of solvents having a hydroxyl group include phenolic solvents such as m-cresol. Examples of solvents having a sulfone group include methyl sulfone, ethyl phenyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, bisphenol S, sorapsone, dapsone, bisphenol A polysulfone, and sulfolane. Examples of solvents having a sulfinyl group include sulfoxide solvents such as N,N-dimethyl sulfoxide (DMSO). In addition to the solvents listed above, amide solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), and N,N-dimethylacetamide (DMAc) can also be used.

[0099] <Other ingredients> The resin composition may contain any component other than those described above, such as a leveling agent for improving the coatability of the varnish when producing a dry film, a dispersant, a surfactant, a retardation adjuster, an antioxidant, an ultraviolet inhibitor, a light stabilizer, a plasticizer, waxes, a filler, a pigment, a dye, a foaming agent, an antifoaming agent, a dehydrating agent, an antistatic agent, an antibacterial agent, an antifungal agent, etc. Among the above-mentioned colorants, the resin composition of the present invention preferably contains a bluing agent for improving the yellowness inherent in the polyimide.

[0100] The bluing agent is an additive (dye, pigment) that absorbs light in the wavelength range of, for example, orange to yellow within the visible light range and adjusts the hue. Examples include inorganic dyes and pigments such as ultramarine, Prussian blue, and cobalt blue, and organic dyes and pigments such as phthalocyanine bluing agents and condensed polycyclic bluing agents. The bluing agent is not particularly limited, but from the viewpoints of heat resistance, light resistance, and solubility, condensed polycyclic bluing agents are preferred, and anthraquinone bluing agents are more preferred. One type of bluing agent may be used alone, or two or more types may be used in combination.

[0101] Examples of condensed polycyclic bluing agents include anthraquinone bluing agents, indigo bluing agents, and phthalocyanine bluing agents. Among these, it is preferable to contain an anthraquinone bluing agent from the viewpoints of heat resistance, light resistance, and solubility.

[0102] From the viewpoint of maintaining a high total light transmittance of a resin layer formed from the resin composition, it is preferable to relatively reduce the total amount (blending amount) of bluing agent used and also to use a small number of types of bluing agents. From the viewpoint of maintaining the total light transmittance while reducing the YI value, the content of the bluing agent is preferably 5 to 100 ppm, more preferably 10 to 70 ppm, based on the solid content of the resin composition.

[0103] [Dry film] The resin composition according to the present invention can be applied to a support to form a coating film, and then the coating film can be dried to remove a portion of the solvent, thereby forming a dry film. Conventional coating methods can be used, including dip coating, flow coating, roll coating, bar coating, blade coating, screen printing, curtain coating, and spray coating. As described above, the present invention can provide a film with reduced mechanical anisotropy regardless of the coating method.

[0104] The drying step for the coated film is not particularly limited as long as the temperature is such that the solvent volatilizes, but from the viewpoint of obtaining a highly transparent resin layer, it is preferably at 60 to 140° C. for about 30 seconds to 30 minutes.

[0105] The support for forming a dry film of the resin composition can be any support that can support the dry film and can be coated with the resin composition, and suitable supports include, for example, polyester films such as polyethylene terephthalate and polyethylene naphthalate, polyimide films, polyamideimide films, polypropylene films, polystyrene films, and other thermoplastic resin films. Among these, polyester films are preferred from the viewpoints of heat resistance, mechanical strength, ease of handling, etc.

[0106] From the viewpoint of improving mechanical strength, the thermoplastic resin film as described above is preferably a film stretched in a uniaxial or biaxial direction.

[0107] The surface of the substrate on which the dry film is formed may be subjected to a release treatment so that the dry film can be easily peeled off from the substrate when the dry film is used. For example, the release treatment can be performed by applying a coating liquid prepared by dissolving or dispersing a release agent such as wax, silicone wax, or silicone-based resin in an appropriate solvent to the surface of the substrate by a known means such as a coating method such as roll coating or spray coating, gravure printing, or screen printing, and drying the coating liquid.

[0108] The dry film of the present invention preferably has a thickness of 5 μm or more and 100 μm or less, more preferably 10 μm or more and 50 μm or less. By setting the thickness within the above range, the laminate described below can also achieve excellent flexibility and excellent transparency. The thickness can be adjusted by the amount of resin composition applied.

[0109] [Laminate] The laminate according to the present invention comprises a glass substrate and a resin layer provided in contact with one of the main surfaces of the glass substrate. The resin layer may be formed by applying a resin composition to the glass substrate to form a coating film, drying the coating film to remove a portion of the solvent, and then heat-curing the coating film, as described above. Alternatively, the resin layer may be formed by laminating a dried film of a dry film to the glass substrate and then heat-curing the dried film. According to one embodiment of the laminate of the present invention, the laminate may comprise a support on the other main surface of the glass substrate, and the glass substrate and the support may be laminated via an adhesive.

[0110] The glass substrate and the dry film are preferably bonded under pressure and heat using a vacuum laminator or the like. By using such a vacuum laminator, the dry film and the glass substrate can be tightly adhered to each other without introducing air bubbles between them. The pressure condition is preferably about 0.1 to 2.0 MPa, and the heating condition is preferably 40 to 120°C.

[0111] After laminating the dry film to the glass substrate, the substrate is peeled off from the dry film to form a dry film on the glass substrate. The dry film is then heat-cured at a temperature of 150°C or higher to form a resin layer, which improves adhesion between the resin layer and the glass substrate.

[0112] <Glass substrate> The glass substrate constituting the laminate of the present invention has a thickness of 25 to 100 μm. A glass substrate having a thickness of 25 to 100 μm can provide a laminate having bending resistance and impact resistance. The thickness of the glass substrate is preferably 30 to 70 μm from the viewpoint of achieving both low manufacturing costs and bending resistance and impact resistance.

[0113] The glass substrate can be any glass substrate having the above thickness. However, silicate glass or silica glass is preferred, and borosilicate glass, soda-lime glass, or aluminosilicate glass is more preferred. Chemically strengthened or alkali-free glass of these glasses is particularly preferred. Chemically strengthened glass is a glass material obtained by chemically strengthening the above glass material. Chemical strengthening can be performed by a conventionally known method. For example, by immersing a glass substrate in a melt of a metal salt (e.g., potassium nitrate) containing metal ions with a large ionic radius, metal ions with a small ionic radius (typically Na ions or Li ions) in the glass substrate are replaced with metal ions with a large ionic radius, resulting in the generation of residual compressive stress on the glass substrate surface. Chemically strengthened glass has superior compressive strength, bending strength, and impact resistance compared to non-chemically strengthened glass. Alkali-free glass refers to glass that is substantially free of alkali components (alkali metal oxides), specifically glass with an alkali component weight ratio of 3000 ppm or less. The weight ratio of the alkali component is preferably 1000 ppm or less, more preferably 500 ppm or less, and most preferably 300 ppm or less.

[0114] The flexural modulus of the glass substrate is preferably 50 to 150 GPa, more preferably 70 to 100 GPa. In this specification, the flexural modulus refers to a value measured at 25°C in accordance with JIS R 1602:1995.

[0115] The glass substrate may be commercially available, and examples thereof include Dragontrail (registered trademark) (manufactured by AGC Corporation: material = aluminosilicate, containing silicon, thickness = 70 μm), SCHOTT AS 87 eco (manufactured by SCHOTT: material = aluminosilicate, thickness = 25 μm, 50 μm, 70 μm), SCHOTT Xensation (registered trademark) Up (manufactured by SCHOTT: material = aluminosilicate, thickness = 30 μm, 50 μm, 70 μm), D263 (registered trademark) Teco (manufactured by SCHOTT: material = borosilicate, thickness = 30 μm, 70 μm), and G-Leaf (registered trademark) manufactured by Nippon Electric Glass Co., Ltd.: material = alkali-free glass, thickness = 50 μm, 100 μm).

[0116] <Hard coat layer> In the laminate of the present invention, a hard coat layer can be provided on the surface of the resin layer made of the resin composition or the dry film. According to the present invention, since the above-mentioned resin composition is used, even when a hard coat layer is provided, it is possible to suppress a decrease in surface hardness and improve adhesion to a glass substrate while maintaining the properties of the polyimide film, such as low warpage, flexibility, and transparency.

[0117] The hard coat layer can be formed using a known and commonly used coating solution (hard coat material) for hard coats, and either a photocurable or thermosetting hard coat material can be used. Commercially available products include X-48-500 manufactured by Shin-Etsu Chemical Co., Ltd., which has excellent flexibility, and Luxidia V-6841 manufactured by DIC Corporation.

[0118] The hard coat layer preferably has a YI value of 2 or less at a film thickness of 50 μm, more preferably 1 or less. If the YI value is 2 or less, a laminate with reduced yellowness (YI value) can be formed.

[0119] The hard coat layer preferably has a pencil hardness (surface hardness) of 2H or more, more preferably 4H or more, in the form of a single hard coat layer. A pencil hardness of 2H or more allows for the formation of a laminate with excellent scratch resistance. The pencil hardness can be measured in accordance with JIS K 5600-5-4.

[0120] From the viewpoint of achieving both a surface protection function and flexibility, the hard coat layer preferably has a thickness of 5 to 50 μm, more preferably 10 to 20 μm.

[0121] <Other layers> When the laminate of the present invention is used for optical purposes such as display devices, a functional layer may be further provided as needed. The function of the functional layer is not particularly limited and may be a common function employed in cover windows of flexible display devices, such as a hard coat function, antistatic function, antiglare function, low reflection function, antireflection function, antifouling function, gas barrier function, primer function, electromagnetic wave shielding function, undercoat function, UV absorption function, adhesive function, or hue adjustment function. The functional layer may be a layer having one type of function or a layer having two or more types of functions. From the viewpoint of ease of use as a cover window, it is preferable that at least one of the functional layers has at least one function selected from the group consisting of antistatic function, antiglare function, low reflection function, antireflection function, and antifouling function.

[0122] [Application] Examples of display components made using the film and laminate film of the present invention include thin, bendable foldable organic EL displays, and flexible panels used in mobile terminals such as smartphones and wristwatch-type terminals, display devices inside automobiles, and wristwatches. They can also be used as components for image display devices such as liquid crystal displays and organic EL displays, touch panel components, flexible printed circuit boards, solar cell panel components such as surface protection films and substrate materials, optical waveguide components, and other semiconductor-related components. In particular, they are suitable for use as components such as cover windows and TFT substrates that constitute foldable organic EL displays.

[0123] [Display cover window] The cover window of a display using the film of the present invention can be, for example, arranged so that the above-mentioned laminate film is positioned on the surface of various displays. The method of arrangement on the surface is not particularly limited, and examples thereof include a method using an adhesive layer. As the material for the adhesive layer, conventionally known adhesive materials that can be used for adhering display surface materials can be used. Note that the cover window of a display using the film or laminate film of the present invention may further have a fingerprint-proof layer on the surface on the side of the protective layer such as a hard coat layer.

[0124] [TFT substrate for organic EL displays] A TFT substrate for an organic EL display using the film of the present invention can be obtained, for example, by forming an amorphous silicon TFT (thin film transistor) on the film of the present invention. The TFT includes a gate metal layer, a silicon nitride gate dielectric layer, and an ITI pixel electrode. Furthermore, the structures required for the organic EL display can be formed on top of this by known methods, and the method for forming circuits, etc. is not particularly limited. [Example]

[0125] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. In the following, "parts" and "%" are all by mass unless otherwise specified.

[0126] <Preparation of Polyimide> The following polyimides 1 to 7 were prepared. Polyimide 1: A 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 2.0 g (0.007 mol) of 1,3-bis(3-aminophenoxy)benzene (APB-N), 3.3 g (0.01 mol) of 1,3-bis(4-aminophenoxy)benzene (TPE-R), 2.8 g (0.01 mol) of 1,3-bis(3-aminopropyl)tetramethyldisiloxane (PAM-E), 15.9 g (0.03 mol) of 2,2-bis[4-(3,4-dicarboxyphenoxyphenyl)]propane dianhydride (BisDA), 56 g of ethyl benzoate, 0.47 g (0.006 mol) of pyridine, and 10 g of toluene. The mixture was reacted under a nitrogen atmosphere at 180° C. for 4 hours while removing the toluene from the system during the reaction, thereby obtaining a 30 wt % polyimide solution. To the resulting polyimide solution, 59.5 mL of N,N-dimethylacetamide (DMAC) and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 1. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 300,000, the polydispersity index (Mw / Mn) was 4.2, and the fluorine content in the polyimide was 0%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 1 was measured, and the YI value was 7.0.

[0127] Polyimide 2: A 200 mL glass vial was charged with 60 g of DMAC and 3.8 g (0.012 mol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl (TFMB), a fluoro-substituted aromatic diamine compound, and stirred to dissolve the TFMB in the DMAC. Subsequently, 3.7 g (0.012 mol) of 3,3',4,4'-dicyclohexyltetracarboxylic dianhydride (HBPDA) was added over 5 minutes under a nitrogen stream while stirring the contents of the vial. The polymerization reaction was continued for 6 hours while maintaining the temperature within the 20-40°C range, yielding a viscous polyamic acid solution. The molar ratio of tetracarboxylic dianhydride to aromatic diamine compound used was 1.00, and the concentration of the polyamic acid solution was 13.0 wt%. Next, 5.9 g of pyridine was added to the polyamic acid solution as an imidization accelerator, and the mixture was kept at a temperature of 30 to 40°C while stirring. 7.1 g (0.07 mol) of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes, and the liquid temperature was then kept at 30 to 40°C while stirring was continued for 12 hours to carry out a chemical imidization reaction, yielding a polyimide solution. To the resulting polyimide solution containing the imidization agent and imidization accelerator, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 2. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 300,000, the polydispersity index (Mw / Mn) was 4.0, and the fluorine content in the polyimide was 21%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 2 was measured, and the YI value was 2.7.

[0128] Polyimide 3: A 200 mL glass vial was charged with 60 g of DMAC and 3.8 g (0.012 mol) of TFMB, and the mixture was stirred to dissolve the TFMB in the DMAC. Subsequently, 3.7 g (0.012 mol) of 4,4'-oxydiphthalic dianhydride (s-ODPA), a tetracarboxylic dianhydride, was added to the vial over a period of approximately 5 minutes under a nitrogen stream while stirring. The mixture was stirred for 6 hours while maintaining the temperature within the range of 20 to 40°C, resulting in a polymerization reaction and a viscous polyamic acid solution. The molar ratio of the tetracarboxylic dianhydride to the aromatic diamine compound used was 1.00, and the concentration of the polyamic acid solution was 10.0 wt%. Next, 5.9 g of pyridine was added to the polyamic acid solution as an imidization accelerator, and the mixture was kept at a temperature of 30 to 40°C while stirring. 7.1 g (0.07 mol) of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes, and the liquid temperature was then kept at 30 to 40°C while stirring was continued for 12 hours to carry out a chemical imidization reaction, yielding a polyimide solution. To the resulting polyimide solution containing the imidization agent and imidization accelerator, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 3. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 250,000, the polydispersity index (Mw / Mn) was 4.3, and the fluorine content in the polyimide was 20%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 3 was measured, and the YI value was 2.3.

[0129] Polyimide 4: A 200 mL glass vial was charged with 59.5 g of DMAC and 4.7 g (0.188 mol) of 3,3'-diaminodiphenyl sulfone (3,3'-DDS). The mixture was stirred to dissolve the 3,3'-DDS in the DMAC. Subsequently, 5.8 g (0.188 mol) of s-ODPA was added over 5 minutes under a nitrogen stream while stirring the contents of the vial. The polymerization reaction was continued for 6 hours while adjusting the temperature to 20-40°C, yielding a viscous polyamic acid solution. The molar ratio of tetracarboxylic dianhydride to aromatic diamine compound used was 1.00, and the concentration of the polyamic acid solution was 14.9 wt%. Next, 5.9 g of pyridine was added to the polyamic acid solution as an imidization accelerator, and the mixture was kept at a temperature of 30 to 40°C while stirring. 7.1 g (0.07 mol) of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes, and the liquid temperature was then kept at 30 to 40°C while stirring was continued for 12 hours to carry out a chemical imidization reaction, yielding a polyimide solution. To the resulting polyimide solution containing the imidization agent and imidization accelerator, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 4. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 210,000, the polydispersity index (Mw / Mn) was 4.5, and the fluorine content in the polyimide was 0%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 4 was measured, and the YI value was 8.0.

[0130] Polyimide 5: A 200 mL glass vial was charged with 60 g of DMAC and 3.8 g (0.012 mol) of TFMB, and the mixture was stirred to dissolve the TFMB in the DMAC. Next, 5.3 g (0.012 mol) of tetracarboxylic dianhydride 4,4'-(1,1,1,3,3,3-hexafluoropropane-2,2-diyl)diphthalic dianhydride (6FDA) was added over 5 minutes under a nitrogen stream while stirring the contents of the vial. The polymerization reaction was continued for 6 hours while maintaining the temperature within the 20-40°C range, yielding a viscous polyamic acid solution. The molar ratio of tetracarboxylic dianhydride to aromatic diamine compound used was 1.00, and the concentration of the polyamic acid solution was 10.0 wt%. Next, 5.9 g of pyridine was added to the polyamic acid solution as an imidization accelerator, and the mixture was kept at a temperature of 30 to 40°C while stirring. 7.1 g (0.07 mol) of acetic anhydride was slowly added dropwise as an imidization agent over a period of about 10 minutes, and the liquid temperature was then kept at 30 to 40°C while stirring was continued for 12 hours to carry out a chemical imidization reaction, yielding a polyimide solution. To the resulting polyimide solution containing the imidization agent and imidization accelerator, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 5. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 210,000, the polydispersity index (Mw / Mn) was 4.2, and the fluorine content in the polyimide was 33%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 5 was measured, and the YI value was 1.5.

[0131] Polyimide 6: A 200 mL glass vial was charged with 59.5 g of DMAC, 3.819 g (0.012 mol) of TFMB, and 1.105 g (0.0003 mol) of silicone-modified diamine X-22-1660B-3 (Shin-Etsu Silicones) and stirred to dissolve the TFMB in the DMAC. Next, 5.576 g (0.013 mol) of 6FDA was added to the vial under a nitrogen stream while stirring. The polymerization reaction was continued for 6 hours while adjusting the temperature to 20-40°C, yielding a viscous polyamic acid solution. The molar ratio of tetracarboxylic dianhydride to aromatic diamine compound used was 1.03, and the concentration of the polyamic acid solution was 15 wt%. Next, 3.9 g of pyridine was added to the polyamic acid solution as an imidization accelerator, and the mixture was stirred while maintaining the temperature at 30 to 40°C. 5.1 g (0.05 mol) of acetic anhydride was slowly added dropwise as an imidization agent, and the liquid temperature was further maintained at 30 to 40°C while stirring was continued for 12 hours to carry out a chemical imidization reaction, thereby obtaining a polyimide solution. To the resulting polyimide solution containing the imidization agent and imidization accelerator, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 6. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 300,000, the polydispersity index (Mw / Mn) was 4.2, and the fluorine content in the polyimide was 28%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 6 was measured, and the YI value was 15.0.

[0132] Polyimide 7: A 500 ml separable flask equipped with a nitrogen inlet tube and a stirrer was charged with 8.6 g (0.0225 mol) of norbornane-2-spiro-α-cyclopentanone-α'-spiro-2″-norbornane-5,5″,6,6″-tetracarboxylic acid dianhydride (CpODA), 2.3 g (0.0075 mol) of s-ODPA, 4.8 g (0.015 mol) of TFMB, 4.57 g (0.015 mol) of (2-phenyl-4-aminophenyl)-4-aminobenzoate (PHBAAB), 56 g of γ-butyrolactone, 0.47 g (0.006 mol) of pyridine, and 56 g of ethyl benzoate. The mixture was reacted under a nitrogen atmosphere at 180°C for 4 hours while removing toluene from the system, thereby obtaining a 30 wt % polyimide solution. To the resulting polyimide solution, 59.5 mL of DMAC and 59.5 mL of methanol were added and stirred until homogeneous. The resulting solution was added dropwise to 300 mL of ion-exchanged water for reprecipitation, yielding solid polyimide 1. The weight-average molecular weight (Mw) measured by gel permeation chromatography was 71,050, the polydispersity index (Mw / Mn) was 4.43, and the fluorine content in the polyimide was 8.9%. Furthermore, the YI value of a 50 μm-thick film of the resulting polyimide 7 was measured, and the YI value was 17.9.

[0133] <Preparation of epoxy compound> The following four epoxy compounds were used: Epoxy 1: HP4032D (difunctional naphthalene-type epoxy resin, manufactured by DIC Corporation) Epoxy 2: HP4700 (tetrafunctional naphthalene-type epoxy resin, manufactured by DIC Corporation) Epoxy 3: EX-214P (bifunctional aliphatic epoxy resin, manufactured by Nagase ChemteX Corporation) Epoxy 4: ZX1059 (difunctional bisphenol A epoxy resin, manufactured by Nippon Steel Chemical & Material Co., Ltd.)

[0134] <Preparation of the compound represented by formula (6), acrylate compound> The following three methoxymethyl compounds and acrylate compounds were used: Methoxymethyl compound 1: MW390 (a compound in which all R in the formula of claim 1 are methoxymethyl groups, manufactured by Sanwa Chemical Co., Ltd.) Acrylate compound 1: M-315 (isocyanuric acid EO-modified di- and triacrylate, manufactured by Toagosei Co., Ltd.) Acrylate compound 2: M-6250 (bifunctional polyester acrylate, manufactured by Toagosei Co., Ltd.)

[0135] <Preparation of Resin Composition> Each resin composition was prepared by mixing each component with a solvent (dimethylacetamide) according to the formulation shown in Table 1. The amount of solvent was adjusted so that the solvent was 333 parts by mass per 100 parts of polyimide. The blue dye in Table 1 is Plast Blue 8514 (manufactured by Arimoto Chemical Industry Co., Ltd.).

[0136] <Solvent resistance evaluation> Each resin composition obtained as described above was applied to a glass substrate (DragonTrail (registered trademark), manufactured by AGC Inc.) measuring 15 cm in length, 11 cm in width, and 70 μm in thickness so that the thickness after drying would be 15 μm. A dried film was formed by drying at 80°C for 30 minutes, and then heat curing was performed at 150°C for 30 minutes to prepare an evaluation substrate having a cured film made of each resin composition. Ethyl acetate and 1-methoxy-2-propanol (PGME) were dropped onto the surface of the cured film side of each evaluation substrate obtained using a dropper. After 10 minutes, the cured film surface was washed with water and dried. The area where the solvent was dropped was observed using an optical microscope (100x magnification) to check for the presence or absence of cracks on the cured film surface. Solvent resistance was evaluated according to the following evaluation criteria. ○: No cracks were observed ×: Cracks were observed The evaluation results are shown in Table 1 below.

[0137] <Adhesion evaluation> For each of the evaluation substrates described above, a 1 cm square observation area was randomly selected, and the presence or absence of air bubbles between the glass substrate and the cured film was observed from the glass substrate side using a digital microscope (VHX-5000, manufactured by Keyence Corporation). ◎: Bubble diameter 0mm ○: Bubble diameter 0mm to 2mm ×: Bubble diameter 2mm or more The evaluation results are shown in Table 1 below.

[0138] <Cross-cut peel test evaluation> Each of the evaluation substrates was subjected to a cross-cut peel test in accordance with ASTM D 3559-B, and the evaluation results are shown in Table 1 below.

[0139] <Impact resistance evaluation> Each evaluation substrate was placed on a flat desk with the glass substrate facing downwards, and an iron ball with a diameter of 30 mm and a weight of 110 g was dropped onto the laminate. The glass was visually inspected after the iron ball was dropped, and the height at which cracks were observed was evaluated. The evaluation criteria were as follows: ◎: 50cm or more ○: 40cm or more and less than 50cm △: 30cm or more and less than 40cm ×: Less than 30cm The impact resistance of the glass substrate itself was evaluated as poor.

[0140] <Surface hardness evaluation> The pencil hardness of the resin layer side of each of the evaluation substrates was measured in accordance with JIS-K5600-5-4:1999, and the highest pencil hardness that did not cause scratches on the coating film was recorded as the pencil hardness. The evaluation results are shown in Table 1. The pencil hardness of the glass substrate itself was 9H.

[0141] <Warp evaluation> Each evaluation substrate was placed on a flat table with the glass substrate facing downwards, and the warpage values ​​(distances from the table to the glass substrate) at the four corners of the evaluation substrate were measured with a ruler, and the average was taken as the warpage value. The evaluation criteria were as follows: ◎: Less than 8mm ○: 8mm or more and less than 10mm ×: 10mm or more ××: Rating not possible The evaluation results are shown in Table 1 below.

[0142] <Yellowness evaluation> The cured film was peeled from each of the evaluation substrates, and the YI value of each cured film was measured using a spectrophotometer (CM-5, manufactured by Konica Minolta, Inc.) in accordance with ASTM E313. Each measured value was normalized by film thickness (50 μm thickness). The measured YI value was evaluated according to the following criteria. 〇: YI value is 7 or less ×: YI value is more than 7 The evaluation results are shown in Table 1 below.

[0143] <Hayes' evaluation> The cured film was peeled off from each of the evaluation substrates, and the haze (%) of each cured film was measured using a haze meter (NDH 7000 II, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7136: 2000. The evaluation criteria were as follows: Good: Haze is 2.0% or less ×: Haze is more than 2.0% The evaluation results are shown in the following Table 1. The haze value of the glass substrate itself used for the evaluation substrate was 0.35%.

[0144] [Table 1]

[0145] As is clear from the evaluation results in Table 1, the evaluation samples (Examples 1 to 7) made using resin compositions in which naphthalene ring-containing epoxy compounds (epoxies 1 and 2) and a compound having a triazine ring structure (methylol compound 1) were added to polyimides (polyimides 1 to 4) having a fluorine content of 25% by mass or less and a YI value of 10 or less when made into a 50 μm-thick polyimide film, were found to have excellent solvent resistance and adhesion while maintaining properties such as low warpage, flexibility, and transparency required for applications such as foldable devices. In contrast, when polyimides having a fluorine content of more than 25% by mass (polyimides 5 and 6) are used, the solvent resistance, adhesion, etc. are not improved even when a naphthalene ring-containing epoxy compound and a compound having a triazine ring structure (methylol compound 1) are added (Comparative Examples 1 and 2). Furthermore, it was found that when a polyimide (Polyimide 7) having a fluorine content of 25 mass% or less but a YI value of more than 10 when made into a 50 μm-thick polyimide film was used, transparency could not be maintained (Comparative Example 3). Furthermore, it is clear that simply adding either a naphthalene ring-containing epoxy compound (epoxy 1) or a compound having a triazine ring structure (methylol compound 1) to a polyimide (polyimide 1) having a fluorine content of 25 mass% or less and a YI value of 10 or less when made into a polyimide-only film having a thickness of 50 μm does not result in a polyimide film having excellent solvent resistance while maintaining properties such as low warpage, flexibility, and transparency (Comparative Examples 4 to 9).

Claims

1. (A) A polyimide having a fluorine-containing skeleton, which contains 80 mol % or more of a structural unit represented by the following formula (1), has a fluorine content of 25 mass % or less, and has a YI value of 10 or less when made into a polyimide-only film having a thickness of 50 μm: 【change】 (In the formula, X's each independently represent a divalent organic group, and Y's each independently represent a tetravalent organic group.) (B) a naphthalene ring-containing epoxy compound, and (C) The following formula (6): 【Chemistry 1】 (In the formula, R １ ~R ６ each independently represents a methylol group, an alkoxymethyl group including an alkoxy group having 1 to 4 carbon atoms, or a hydrogen atom, provided that at least two of them are methylol groups or alkoxy groups having 1 to 4 carbon atoms. A compound represented by A resin composition comprising:

2. The resin composition according to claim 1, wherein the naphthalene ring-containing epoxy compound (B) is contained in an amount of 10 to 50 mass % based on the entire resin composition.

3. The resin composition according to claim 1 or 2, wherein the compound (C) represented by formula (6) is contained in an amount of 5 to 20 mass % based on the entire resin composition.

4. A dry film comprising a substrate and a dry film releasably provided on the substrate, wherein the dry film is a coating film of the resin composition according to any one of claims 1 to 3.

5. A laminate comprising a glass substrate, a resin layer provided on one of the main surfaces of the glass substrate so as to be in contact with the surface, and a hard coat layer provided on the resin layer, The resin layer is a cured film of the resin composition according to any one of claims 1 to 3, or a dried film of the dry film according to claim 4.

6. The laminate according to claim 5, which is used as a cover window for a flexible display device.

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