Resin composition, film, and display device

Abstract

To provide a resin composition capable of yielding a film with low yellowness, while retaining excellent resilience.SOLUTION: A resin composition comprises one or more resins (A) selected from polyamide-imide resins and polyamide resins, a fibrous alumina filler (B), and a crosslinking agent (C) containing two or more functional groups of at least one kind selected from among methylol groups and alkoxymethyl groups.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a resin composition, a film, and a display device.

Background Art

[0002] Foldable devices have recently attracted attention in order to further enhance the portability of portable information terminals such as smartphones and tablets. Conventionally, glass has been used as a member such as a cover window used for a display constituting such a foldable device. However, since glass is a rigid material, a film using a polymer has been used from the viewpoint of flexibility.

[0003] Polymer films are required to have not only flexibility but also excellent mechanical properties and excellent optical properties. In order to meet such requirements, for example, in Patent Document 1, a resin composition containing a resin component and a fibrous alumina filler, wherein the resin component includes a resin having an imide structure and an amide structure, and the fibrous alumina filler is dispersed in the resin composition in a state where the average fiber diameter is 4 to 30 nm and the average fiber length is 200 to 4,000 nm. A polymer film made of the resin composition has been proposed.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] Polymer films are required to be less likely to have compression marks or bending marks (hereinafter, "folding marks") on the film surface even when repeatedly folded or held in a folded state for a long time as assumed in foldable devices. In this regard, Japanese Patent Application Laid-Open No. 2022-135876 discloses controlling the resilience of a film in order to improve the resilience of a polyimide film against physical deformation caused by external force. Although the polymer film of Patent Document 1 is excellent in mechanical properties, there is room for improvement in terms of resilience.

[0006] In addition, as a polymer material used for a display, colorless transparency, particularly low yellowness, is also required. Therefore, there is a demand for a polymer film that has high resilience to suppress the occurrence of folding marks and also has low yellowness.

Means for Solving the Problems

[0007] The present inventors intensively studied to solve the above problems, and found that by blending a heat-reactive crosslinking agent into a resin composition containing one or more resins selected from a polyamideimide resin and a polyamide resin, it is possible to improve the resilience of a film obtained using the resin composition. However, when the resin composition further contains a fibrous alumina filler, depending on the type of the heat-reactive crosslinking agent, the yellowness of the film obtained using the resin composition may increase significantly. The present inventors further intensively studied for reducing yellowness, and by blending a crosslinking agent containing two or more of one or more functional groups selected from a methylol group and an alkoxymethyl group as the heat-reactive crosslinking agent, found that the film obtained using the resin composition has low yellowness while maintaining good resilience, and completed the present invention.

[0008] The gist configuration of the present invention is as follows. [1] A resin composition containing one or more resins (A) selected from a polyamideimide resin and a polyamide resin, a fibrous alumina filler (B), and a crosslinking agent (C) containing two or more of one or more functional groups selected from a methylol group and an alkoxymethyl group. The resin composition. [2] The resin composition according to [1], wherein the component (A) is a polyamideimide resin. [3] The resin composition according to [1] or [2], wherein the component (B) is a boehmite-shaped or pseudo-boehmite-shaped alumina filler. [4] The resin composition according to any one of [1] to [3], wherein the component (C) is a crosslinking agent having a melamine skeleton or a crosslinking agent having a benzoguanamine skeleton. [5] The resin composition according to any one of [1] to [4], wherein the component (B) is 1 to 50 parts by mass and the component (C) is 0.1 to 50 parts by mass with respect to 100 parts by mass of the component (A). [6] A film comprising the resin composition according to any one of [1] to [5]. [7] The film according to [6], wherein R according to the following formula (1) is 0.93 to 2.00 MPa. R = α·ε / 2 (1) In the formula, α is the yield strength (unit: MPa) and ε is the yield strain. [8] The film according to [6] or [7], wherein the yellow index is 0 or more and 3.0 or less. [9] A display device including the film according to any one of [6] to [8]. [Advantages of the Invention]

[0009] According to the resin composition of the present invention, a film having a low yellowness while maintaining good resilience is provided. It is expected that this film is less likely to develop folding marks even when repeatedly folded or held in a folded state for a long time. [Brief Description of the Drawings]

[0010]

Figure 1

[0011] [Resin Composition] The resin composition of the present invention contains at least one resin (A) selected from a polyamide-imide resin and a polyamide resin, a fibrous alumina filler (B), and a crosslinking agent (C) containing two or more functional groups selected from a methylol group and an alkoxymethyl group.

[0012] [Component (A)] The component (A) of the present invention may be at least one selected from a polyamide resin and a polyamide-imide resin, and may be only a polyamide resin, only a polyamide-imide resin, or a combination of a polyamide resin and a polyamide-imide resin. The polyamide resin and the polyamide-imide resin can be used alone or in combination of two or more. Preferably, the resin component consists essentially of only the component (A).

[0013] (Polyamide-imide resin) A polyamide-imide resin can be used in the resin composition of the present invention. The polyamide-imide resin can be obtained by reacting a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound as monomer components. Specifically, a polymer having an imide precursor structure is synthesized by reacting a diamine compound and a tetracarboxylic acid compound, and then a copolymer having an imide precursor structure and an amide structure is synthesized by reacting the polymer and a dicarboxylic acid compound, and then the imide precursor structure in the copolymer is subjected to a ring-closing reaction (imidation). In addition, a polymer having an imide precursor structure may be synthesized by reacting a diamine compound and a tetracarboxylic acid compound, the imide precursor may be subjected to a ring-closing reaction, and then a copolymer having an imide structure and an amide structure may be synthesized by reacting with a dicarboxylic acid compound.

[0014] That is, the polyamide-imide resin can have a structure in which a residue obtained by reacting a diamine compound and a tetracarboxylic acid compound is bonded via an imide structure, and a residue obtained by reacting a dicarboxylic acid compound via an amide structure is bonded. Among them, the polyamideimide resin preferably contains at least one structure selected from the group consisting of a structure in which a fluorine atom, an aliphatic ring, and aromatic rings are linked by an alkylene group which may be substituted with a sulfonyl group or a fluorine atom as a residue obtained by reacting the above diamine compound and tetracarboxylic acid compound.

[0015] Examples of the diamine compound used for synthesizing the polyamideimide resin include aliphatic diamines, aromatic diamines, and mixtures thereof. Here, the "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents in a part of its structure. This aromatic ring may be a monocyclic ring or a condensed ring, and examples include, but are not limited to, benzene ring, naphthalene ring, anthracene ring, and fluorene ring. Among these, a benzene ring is preferable. The "aliphatic diamine" represents a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents in a part of its structure. The diamine compound can be used alone or in combination of two or more.

[0016] Specific examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylenediamine; cyclic aliphatic diamines such as 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, 4,4'-diaminodicyclohexylmethane, etc. These can be used alone or in combination of two or more.

[0017] Specific examples of the aromatic diamine include aromatic diamines having one aromatic ring, such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, 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, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, 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)benzidine (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, 9,9-bis(4-amino-3-fluorophenyl)fluorene, etc., which are aromatic diamines having two or more aromatic rings. These can be used alone or in combination of two or more kinds.

[0018] Among the above diamine compounds, from the viewpoint of improving the colorless transparency and elasticity as a film, one or more selected from the group consisting of aromatic diamines having a biphenyl structure, specifically, 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 are preferably used. Further, from the viewpoint of easily improving the colorless transparency, a diamine having a biphenyl structure and having a part or all of the hydrogen atoms on the aromatic ring substituted with a substituent selected from a fluoro group, a trifluoromethyl group, or a trifluoromethoxy group, specifically, 2,2'-bis(trifluoromethyl)benzidine is more preferably used.

[0019] Examples of the tetracarboxylic acid compound used for the synthesis of the polyamideimide resin include tetracarboxylic acids or tetracarboxylic acid derivatives. The tetracarboxylic acid derivatives include anhydrides of tetracarboxylic acids, preferably dianhydrides, acid chlorides, and the like. Examples of the tetracarboxylic acid compound include aromatic tetracarboxylic acids and their anhydrides, preferably aromatic tetracarboxylic acid compounds such as their dianhydrides; aliphatic tetracarboxylic acid compounds and their anhydrides, preferably aliphatic tetracarboxylic acid compounds such as their dianhydrides. These tetracarboxylic acid compounds can be used alone or in combination of two or more.

[0020] Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4'-oxydiphthalic dianhydride (sODPA), 3,4-oxydiphthalic anhydride (aODPA), 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic dianhydride (BPADA), 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2',3,3'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sBPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (aBPDA), 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(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, 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, 4,4'-(m-phenylenedioxy)diphthalic dianhydride, and 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF). Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

[0021] Examples of the aliphatic tetracarboxylic dianhydrides include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkane tetracarboxylic dianhydrides such as 1,2,4,5-cyclohexanetetracarboxylic dianhydride (HPMDA), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3’,4,4’-tetracarboxylic dianhydride (HBPDA), and their positional isomers. These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydrides include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride, and these can be used alone or in combination of two or more. Further, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

[0022] Among tetracarboxylic acid compounds, from the viewpoint of improving the flex resistance and optical properties as a film, an aromatic tetracarboxylic dianhydride having a substituent selected from a fluoro group, a trifluoromethyl group, or a trifluoromethoxy group, specifically, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and a tetracarboxylic dianhydride having a biphenyl structure, a fluorene structure, or an alicyclic hydrocarbon structure, specifically, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sBPDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), 1,2,3,4-cyclobutanetetracarboxylic dianhydride (CBDA), dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride (HBPDA), it is preferable to use a combination of one selected from the group consisting of them, and the composition ratio (6FDA:sBPDA, BPAF, CBDA, HBPDA, any one of them) of 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride and one selected from the group consisting of 1,2,3,4-cyclobutanetetracarboxylic dianhydride and dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride is more preferably 1:2 as a molar ratio.

[0023] Among tetracarboxylic acid compounds, from the viewpoint of improving transparency and adhesion without impairing various properties such as heat resistance and mechanical strength as a film, 3,4-oxydiphthalic dianhydride (aODPA), and at least one selected from the group consisting of 4,4'-oxydiphthalic dianhydride (sODPA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (aBPDA), 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA) are preferably used in combination.

[0024] Examples of the dicarboxylic acid compound used for the synthesis of the polyamideimide resin include a dicarboxylic acid or a dicarboxylic acid derivative, and examples of the dicarboxylic acid derivative include an acid chloride or an ester form of the dicarboxylic acid. The dicarboxylic acid compound can be used alone or in combination of two or more.

[0025] Specific examples of the dicarboxylic acid compound include, for example, 1,3 - cyclobutanedicarboxylic acid, 1,3 - cyclopentanedicarboxylic acid, 1,4 - cyclohexanedicarboxylic acid, 4,4'-oxybisbenzoic acid, terephthalic acid, isophthalic acid, 2,6 - naphthalenedicarboxylic acid, 1,5 - naphthalenedicarboxylic acid, 1,4 - naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid, 3,3'-biphenyldicarboxylic acid, two cyclohexanecarboxylic acids or two benzoic acids linked by a single bond, -CH 2 -, -C(CH 3 ) 2 -, -C(CF 3 ) 2 -, -SO 2 - or an alicyclic dicarboxylic acid or aromatic dicarboxylic acid such as a compound linked by a phenylene group and their derivatives (for example, acid chloride, acid anhydride); aliphatic dicarboxylic acid compounds such as dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms and their derivatives (for example, acid chloride, ester form), etc. These dicarboxylic acid compounds can be used alone or in combination of two or more.

[0026] Among these, from the viewpoint of improving the elongation at break and elastic modulus as a film, it is preferable to use terephthalic acid or 4,4'-oxybisbenzoic acid or their derivatives, particularly terephthalic acid chloride (sometimes denoted as TPC) or 4,4'-oxybis(benzoyl chloride) (4,4'-diphenylether dicarboxylic acid chloride, sometimes denoted as DEDC).

[0027] In the synthesis of the polyamide-imide resin of the resin composition of the present invention, with respect to a total of 100 mol% of the tetracarboxylic acid compound and the dicarboxylic acid compound, the dicarboxylic acid compound may be more than 0 mol% and less than 100%, but from the viewpoint of obtaining the effect of improving the resilience of the film by blending an amide structure and a thermally reactive crosslinking agent, 10 mol% or more is preferable, 20 mol% or more is more preferable, and 40 mol% or more is even more preferable. And the composition ratio of this monomer component is such that in the repeating unit in the polyamide-imide resin, the amide structure is more than 0 mol%, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 40 mol% or more. From the viewpoint of sufficiently obtaining the effect of introducing the imide structure, the amide structure is preferably 90 mol% or less, more preferably 80 mol% or less.

[0028] For example, the composition ratio of the monomer components (diamine compound:tetracarboxylic acid compound:dicarboxylic acid compound) is preferably 7:0.5 to 4:3 to 6.5, more preferably 7:1.5 to 3.5:3.5 to 5.5, and particularly preferably 7:2.5 to 3.5:3.5 to 4.5 as a molar ratio. And according to the composition ratio of the above-mentioned monomer components, the composition ratio (molar ratio) of the imide structure and the amide structure in the structure of the polyamide-imide resin is preferably 0.5 to 4:3 to 6.5, more preferably 1.5 to 3.5:3.5 to 5.5, and particularly preferably 2.5 to 3.5:3.5 to 4.5. By having the composition ratio of the imide structure and the amide structure be the above-mentioned composition ratio, excellent flexibility and high elasticity can be achieved in good balance.

[0029] For the ring-closing reaction (imidation) of the imide precursor in the synthesis of the polyamide-imide resin, either thermal imidization by adding an azeotropic solvent (e.g., toluene, xylene, etc.) that azeotropes with water and heating, or chemical imidization using a condensing agent and a reaction accelerator can be used, but chemical imidization is preferred because it is easier to maintain colorless transparency.

[0030] Examples of the reaction accelerator used for chemical imidization include triethylamine, diisopropylethylamine, N-methylpiperidine, pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 3-ethylpyridine, 3,5-dimethylpyridine, 3,5-diethylpyridine, isoquinoline, imidazole, 1-methylimidazole, 2-methylimidazole, and 1,2-dimethylimidazole. These reaction accelerators may be used alone or in combination of two or more thereof.

[0031] Examples of the condensing agent used for chemical imidization include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride, phosphite esters, and phosphite esters such as triethyl phosphite, triethyl phosphite, tributyl phosphite, dimethyl phosphite, diethyl phosphite, and triphenyl phosphite. These condensing agents may be used alone or in combination of two or more thereof.

[0032] The organic solvent used for the synthesis of the polyamideimide resin is not particularly limited as long as it is an organic solvent inert to the reaction. For example, N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, m-cresol, γ-butyrolactone, cyclopentanone, cyclohexanone, tetrahydrofuran, etc. may be mentioned. These organic solvents may be used alone or in combination of two or more thereof.

[0033] The ring-closing reaction conditions for the synthesis of the polyamideimide resin can be 10 to 50°C for 1 to 27 hours, and from the viewpoint of maintaining colorless transparency, it is preferably synthesized under a nitrogen atmosphere.

[0034] The weight average molecular weight (Mw) of the polyamideimide resin is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 80,000 to 800,000, and even more preferably in the range of 110,000 to 600,000 from the viewpoint of improving the elastic modulus and the elongation at break. In this specification, the weight-average molecular weight (Mw) is a value measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene, and specifically, it is measured by the method described in the examples.

[0035] (Polyamide resin) A polyamide resin can be used in the resin composition of the present invention. The polyamide resin can be obtained by reacting a diamine compound and a dicarboxylic acid compound as monomer components. The dicarboxylic acid compound is a dicarboxylic acid and its derivatives (such as acid chlorides, esters, etc.).

[0036] That is, the polyamide resin can have an amide structure formed by the reaction of a diamine compound and a dicarboxylic acid compound. The repeating unit constituting the polyamide resin is different from the polyamideimide resin in that it does not substantially contain an imide structure. Further, as a structure connecting the monomer components constituting the polyamide resin, it is more preferable that it substantially does not contain a repeating structure other than the amide structure and consists of an amide structure.

[0037] Here, regarding the diamine compound, the description (including examples and preferred examples) regarding the diamine compound described in the section on the above polyimideamide resin is applicable. Regarding the dicarboxylic acid compound, the description (including examples and preferred examples) regarding the dicarboxylic acid compound described in the section on the above polyimideamide resin is applicable.

[0038] Among the above diamine compounds, from the viewpoint of improving the colorless transparency and elasticity as a film, one or more selected from the group consisting of aromatic diamines having a biphenyl structure, specifically, 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 are preferably used. Further, from the viewpoint of easily improving the colorless transparency, a diamine having a biphenyl structure and having a part or all of the hydrogen atoms on the aromatic ring substituted with a substituent selected from a fluoro group, a trifluoromethyl group, or a trifluoromethoxy group, specifically, 2,2'-bis(trifluoromethyl)benzidine is more preferably used.

[0039] Among the above dicarboxylic acid compounds, from the viewpoint of improving the elongation at break and elastic modulus as a film, terephthalic acid or 4,4'-oxybisbenzoic acid or a derivative thereof, particularly, terephthalic acid chloride (sometimes denoted as TPC) or 4,4'-oxybis(benzoyl chloride) (4,4'-diphenyl ether dicarboxylic acid chloride, sometimes denoted as DEDC) is preferably used. It is also preferable to use TPC and DEDC in combination. In that case, the molar ratio (number of moles of TPC:number of moles of DEDC) can be 1:4 to 4:1, preferably 2:3 to 4:1. With these molar ratios, substantially, the structural units derived from TPC and the structural units derived from DEDC are introduced into the polyamide resin.

[0040] The polyamide resin can be produced by a method known as a method for producing polyamide. For example, a solution polymerization method, an interfacial polymerization method, a melt polymerization method, a solid-phase polymerization method, etc. can be used. In particular, as a method for producing an aromatic polyamide, a solution polymerization method and an interfacial polymerization method can be preferably used.

[0041] Specifically, a polyamide resin can be synthesized from a dicarboxylic acid chloride and a diamine compound by a solution polymerization method. In this case, the reaction can be carried out in an aprotic organic polar solvent.

[0042] In this reaction, hydrogen chloride is by-produced. When neutralizing this, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate, and organic neutralizing agents such as 1,2-butylene oxide, ethylene oxide, propylene oxide, ammonia, and pyridine are used.

[0043] When polymerization is carried out using two or more kinds of diamine compounds, the diamine compounds are added one by one, 10 to 99 mol% of dicarboxylic acid dichloride is added to the diamine compound and reacted, and then another diamine compound is added, and further dicarboxylic acid dichloride is added and reacted in a stepwise reaction method. Also, a method of mixing and adding all the diamine compounds and then adding dicarboxylic acid dichloride and reacting can be used. Further, when using two or more kinds of dicarboxylic acid dichlorides, similarly, a stepwise method, a method of adding simultaneously, etc. can be used. The molar ratio of all the diamine compounds to all the dicarboxylic acid dichlorides (the number of moles of all the diamine compounds: the number of moles of all the dicarboxylic acid dichlorides) can be appropriately adjusted according to the molecular weight of the target polyamide. For example, by setting it to 49:51 to 51:49, a polyamide with a sufficiently large molecular weight and excellent mechanical properties can be obtained.

[0044] When a diamine compound and a dicarboxylic acid dichloride are used as raw materials, it becomes an amine terminal or a carboxylic acid terminal depending on the composition ratio of the raw materials. From the viewpoint of improving the colorless transparency of the film, it is preferable to perform end-capping with other amines, carboxylic acid chlorides, and carboxylic acid anhydrides.

[0045] Examples of the compound used for end-capping include acetyl chloride, benzoyl chloride, substituted benzoyl chloride, acetic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, 4-ethynylaniline, 4-phenylethynylphthalic anhydride, maleic anhydride, etc. End-capping may not be performed, and in this case, the end groups can also be used as cross-linking points, etc.

[0046] In the production of polyamide resins, examples of the aprotic polar solvents to be used include sulfoxide-based solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide-based solvents such as N,N-dimethylformamide and N,N-diethylformamide, acetamide-based solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, pyrrolidone-based solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone, or hexamethylphosphoramide, γ-butyrolactone, etc. It is desirable to use these alone or as a mixture, but furthermore, the use of aromatic hydrocarbons such as xylene and toluene is also possible. Furthermore, for the purpose of promoting the dissolution of the polymer, salts of alkali metals or alkaline earth metals at 50% by mass or less can be added to the solvent.

[0047] The reaction conditions for the synthesis of polyamide resins can be 10 to 50 °C for 10 minutes to 27 hours, and from the viewpoint of maintaining colorless transparency, it is preferable to synthesize under a nitrogen atmosphere.

[0048] From the viewpoint of improving mechanical properties, the polyamide resin of the present invention preferably has a number average molecular weight (Mn) of 5,000 or more and 200,000 or less, and more preferably 10,000 or more and 180,000 or less.

[0049] From the viewpoint of improving mechanical properties, the polyamide resin of the present invention preferably has a weight average molecular weight (Mw) of 10,000 or more and 1,000,000 or less, more preferably 50,000 or more and 500,000 or less, and even more preferably 100,000 or more and 300,000 or less.

[0050] The polyamide resin of the present invention preferably has a dispersity (Mw / Mn) of 1.0 or more and 20 or less, more preferably 1.0 or more and 15 or less, and even more preferably 1.0 or more and 4.0 or less.

[0051] The resin in the resin composition of the present invention preferably has substantially no hydroxyl group and carboxyl group. When the resin has a hydroxyl group or a carboxyl group, the crosslinking density may increase significantly due to the crosslinking of the thermoreactive crosslinking agent described later and the resin, and the flexibility of the resin may decrease significantly. By substantially having no hydroxyl group and carboxyl group in the resin, resilience can be increased while maintaining the flexibility of the resin.

[0052] [Component (B)] Component (B) of the present invention is a fibrous alumina filler, which is a fibrous filler and includes those composed of alumina and alumina hydrate. Here, "fibrous" refers to a shape with an aspect ratio (filler length / filler diameter) of 5 or more. Examples of the alumina hydrate include boehmite and pseudo-boehmite. Component (B) is preferably a boehmite-type or pseudo-boehmite-type alumina filler. Component (B) can be used alone or in combination of two or more.

[0053] The fibrous alumina filler (Component (B)) is preferably dispersed in the resin composition of the present invention containing the above-described resin component (Component (A)) in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm. According to such a fibrous alumina filler in a dispersed state, it is considered that each fiber is arranged in a lattice pattern with each other in the resin composition, so that it is possible to suppress coloring, turbidity, and a decrease in flexibility, and impart a remarkable effect of increasing high elasticity. In addition, compared with spherical or amorphous fillers, the fibrous alumina filler can impart an excellent anti-blocking effect without impairing light transmittance. Specifically, when films made of the resin composition of the present invention are stacked or wound into a roll for storage, the above-described fibrous alumina filler can suppress the adhesion (blocking) between the films, and improve storage stability and workability.

[0054] In the resin composition of the present invention, the fibrous alumina filler ((B) component) preferably has an average fiber diameter of 1 to 30 nm and an average fiber length of 100 to 4,000 nm, more preferably an average fiber diameter of 2 to 25 nm and an average fiber length of 200 to 3,000 nm, and even more preferably an average fiber diameter of 3 to 20 nm and an average fiber length of 500 to 2,000 nm, and is dispersed. The fact that the fibrous alumina filler is dispersed in the resin composition in a state of having an average fiber diameter and an average fiber length within the above-described ranges is advantageous for a film formed using this resin composition to achieve high elasticization while suppressing coloring and turbidity and maintaining flexibility. The "average fiber diameter" and "average fiber length" in the dispersed state of the fibrous alumina filler in the resin composition of the present invention are measured by diluting the resin composition 10,000 times with a solvent (for example, methyl isobutyl ketone (MIBK) or dimethylacetamide (DMAc)) used for adjusting the resin composition, dropping one drop onto a cover glass (cover glass trophy, manufactured by Matsunami Glass Industries, Ltd.), drying at 50°C, and then observing with an electron microscope image (for example, a 10,000-fold observation image using FE-SEM manufactured by Hitachi High-Tech). In addition, as long as the fibrous alumina filler to be measured can be visually recognized as a single fiber in the electron microscope image, it may be in any state of a single fiber or a fiber bundle in which a plurality of single fibers are aggregated. The average measured length value of the diameters in the short side direction of 50 fibrous alumina fillers arbitrarily selected in the electron microscope image is defined as the "average fiber diameter", and the average measured length value in the long side direction is defined as the "average fiber length".

[0055] The fibrous alumina filler ((B) component) is compounded and stirred with the (A) component, the (C) component, and optionally any other components in the form of a powder or the dispersion liquid (sol) described below, and kneaded as necessary, whereby the dispersion state in the resin composition, namely, the "average fiber diameter" and the "average fiber length" can be adjusted. For example, stirring or kneading can be performed using a stirrer such as a dissolver or a butterfly mixer, or a kneader such as a roll mill or a bead mill. At that time, it can be adjusted according to various conditions such as the rotation speed of the stirrer / kneader, the shape of the stirring blades / kneading device, the stirring / kneading time, the stirring / kneading temperature, the bead filling rate, and the roll gap.

[0056] The fibrous alumina filler ((B) component) can be surface-treated or used as a dispersion liquid (sol) dispersed in an organic solvent or the like. By performing surface treatment or compounding as a dispersion liquid, the dispersion state in the resin composition can be stabilized. Among these, if a dispersion liquid is used in which the dispersion state of the fibrous alumina filler in the dispersion liquid (sol) is adjusted to be the same as the dispersion state of the fibrous alumina filler in the resin composition of the present invention, namely, the "average fiber diameter" and the "average fiber length", the resin composition of the present invention can be produced with high productivity.

[0057] The method for surface treatment or making a dispersion liquid of the fibrous alumina filler ((B) component) is not particularly limited. For example, a surface treatment method using a coupling agent such as a silane-based, titanate-based, aluminate-based, or zirconaluminate-based coupling agent, or a method for producing a dispersion liquid treated with an organic sulfonic acid disclosed in JP-A-2008-31010 can be used.

[0058] Examples of the fibrous alumina filler ((B) component) include the aluminosol series manufactured by Kawaken Fine Chemicals.

[0059] [(C) component] The (C) component of the present invention is a crosslinking agent containing two or more functional groups selected from methylol groups and alkoxymethyl groups. The (C) component can be used alone or in combination of two or more. In the present invention, the alkoxymethyl group is -CH2 A group represented by -O-R, where R is an alkyl group. R is preferably an alkyl group having 1 to 6 carbon atoms, more preferably 1 or 2 carbon atoms, and particularly preferably 1 carbon atom.

[0060] One or more functional groups selected from a methylol group and an alkoxymethyl group are preferably a methylol group or a methoxymethyl group.

[0061] The component (C) can be a crosslinking agent having a melamine skeleton, a crosslinking agent having a guanamine skeleton, a crosslinking agent having a glycoluril skeleton, etc. Compounds of these types containing two or more methylol groups or alkoxymethyl groups are preferred. Compounds of these types known as heat-reactive crosslinking agents can also be used.

[0062] The crosslinking agent having a melamine skeleton is a compound having a melamine structure and containing two or more of one or more functional groups selected from a methylol group and an alkoxymethyl group. As the component (C), the compound represented by the formula (1) can be used. These oligomers can also be used.

Chemical formula

[0063] The crosslinking agent having a benzoguanamine skeleton is a compound having a benzoguanamine structure and containing two or more of one or more functional groups selected from a methylol group and an alkoxymethyl group. As the component (C), the compound represented by the formula (2) can be used. These oligomers can also be used.

Chemical formula

[0064] The crosslinking agent having a glycoluril skeleton is a compound having a glycoluril structure containing two or more functional groups selected from methylol groups and alkoxymethyl groups, and examples of the component (C) include 1,3,4,6 - tetrakis(hydroxymethyl)glycoluril, 1,3,4,6 - tetrakis(methoxymethyl)glycoluril, 1,3,4,6 - tetrakis(butoxymethyl)glycoluril, etc.

[0065] As the component (C), hexamethylolmelamine, hexamethoxymethylmelamine, tetramethylolbenzoguanamine, tetramethoxymethylbenzoguanamine, and their oligomers are preferable.

[0066] [Resin Composition] In the resin composition of the present invention, with respect to 100 parts by mass of the component (A), the component (B) is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and the component (C) is preferably 0.1 to 50 parts by mass, more preferably 0.5 to 40 parts by mass, and even more preferably 1 to 30 parts by mass. Within this range, using the resin composition of the present invention, a film having low yellowness can be obtained while maintaining good resilience.

[0067] In the resin composition of the present invention, within a range not impairing the effects of the present invention, in addition to the components (A) to (C), optional additives may be included. Specifically, fillers different from the fibrous alumina filler (B), leveling agents, dispersants, surfactants, retardation regulators, antioxidants, ultraviolet light absorbers, light stabilizers, plasticizers, waxes, fillers, pigments, dyes, foaming agents, defoaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, bluing agents for reducing the yellowness of the film, phosphorus compounds, lubricants, pH adjusters, etc. can be mentioned.

[0068] The resin composition of the present invention can be obtained by dissolving at least one selected from polyamide resins and polyamideimide resins and a thermoreactive crosslinking agent in a solvent to form a resin composition (resin varnish). The solvent is not particularly limited as long as it can dissolve the above components. However, from the viewpoints of the coatability of the resin varnish and the transparency of the resulting film, etc., 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 preferable.

[0069] Examples of the solvent having an ester group include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, dimethyl carbonate, etc. Solvents having a cyclic ester group can also be used, and examples thereof 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, δ-hexanolactone, etc.

[0070] Examples of the solvent having an ether group include tetrahydrofuran, dioxane, dibutyl ether, etc. Examples of the solvent having a ketone group include ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, etc. Examples of the solvent having a hydroxyl group include phenolic solvents such as m-cresol, etc. Examples of the solvent having a sulfone group include methyl sulfone, ethyl phenyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, bisphenol S, sorapson, dapsone, bisphenol A polysulfone, sulfolane, etc. Examples of the solvent having a sulfinyl group include sulfoxide solvents such as N,N-dimethyl sulfoxide (DMSO), etc. In addition to the solvents listed above, amide solvents such as N-methyl-2-pyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DMAc), etc. can be used.

[0071] The resin composition of the present invention has a wide range of applications as materials for, for example, films, sheets, pipes, tubes, filaments, fibers, containers, etc. Among these, it is particularly suitable for use as a film material.

[0072] [Film] The film of the present invention is a film obtained by using the resin composition of the present invention. For example, it can be obtained by making the resin composition of the present invention into a resin varnish, applying it onto a support, drying it, and then peeling it off from the support. It is presumed that a crosslinked structure by a heat-reactive crosslinking agent is formed by the heat during film production, improving the resilience of the film.

[0073] Here, resilience means the energy per unit volume that a substance can absorb without permanent deformation. The resilience of a film is related to the relationship between the stress applied to the film and the strain of the film in the tensile test of the film, and corresponds to the area of the elastic deformation region shaded in the image diagram of FIG. 1. A high resilience means a high elastic recovery force, and it is expected that a film with high resilience can easily recover to its original state even when repeatedly folded or held in a folded state for a long time, and is less likely to generate fold marks.

[0074] Although resilience is obtained as the area in the elastic deformation region as described above, an approximate value can be evaluated by R in the following formula (1) by approximating the stress-strain diagram of the elastic deformation region as a triangular shape as shown in FIG. 1. The R of the film of the present invention is preferably 0.93 MPa or more, and may be 2.00 MPa or less. R = α·ε / 2 (1) In the formula, α is the yield strength (unit: MPa), and ε is the yield strain. The yield strength is the stress at the yield point in the stress-strain diagram, and the yield strain is the strain at the yield point.

[0075] The yield strength and yield strain of the film can be measured by the method of the examples.

[0076] The film of the present invention preferably has a yield strength of 70 to 200 MPa, more preferably 100 to 180 MPa.

[0077] The film of the present invention preferably has a yield strain of 0.1 to 20%, more preferably 0.5 to 10%.

[0078] The film of the present invention has a low yellowness, and preferably has a YI value (Yellow Index) of 0 or more and 3.0 or less, more preferably 0 or more and 2.5 or less, and even more preferably 0 or more and 2.0 or less. Also, the closer the YI value is to 0, the better the achromaticity.

[0079] The YI value can be measured by the method of the examples, but the YI value referred to here means the measured value not normalized by the film thickness of the film.

[0080] The film of the present invention preferably has a film thickness of 5 to 100 μm, more preferably 10 to 70 μm. Within this range, excellent flexibility can be easily obtained, and the film can be preferably used as a cover window for a foldable display or a flexible display.

[0081] The film of the present invention can be obtained by drying the coating film of the resin composition of the present invention. For example, the film of the present invention can be obtained by turning the resin composition of the present invention into a resin varnish, applying it on a support, drying it, and then peeling it off from the support.

[0082] The coating method is not particularly limited, and known means can be applied. For example, dip coating method, flow coating method, roll coating method, bar coater method, blade coater method, screen printing method, curtain coating method, spray coating method, etc. can be mentioned. The coating thickness can be adjusted according to the film thickness of the film.

[0083] The drying conditions are not particularly limited as long as the temperature allows the solvent to volatilize, but from the viewpoint of obtaining a film with excellent transparency, it is preferably about 60 to 250 °C for 10 to 60 minutes.

[0084] [Display device] The film of the present invention can be used as a member of a display device, and the present invention relates to a display device including the film of the present invention.

[0085] The film of the present invention can be suitably used as a cover window of a display device. For example, the film can be disposed and used so as to be located on the surface of various display devices. The method of disposing on the surface is not particularly limited, and examples include a method via an adhesive layer. As the material of the adhesive layer, known adhesive materials can be used. The cover window using the film of the present invention may be provided with a protective layer such as a hard coat layer on the film surface, and further an anti-fingerprint adhesion layer.

[0086] The display device of the present invention may be a flexible type or a non-flexible type. The flexible type includes a foldable type that can be folded, a type that can be rolled into a cylindrical shape, a rollable type, etc. Since the film of the present invention has high resilience, it is suitable for a flexible type display device, and particularly suitable for a foldable type display device.

[0087] The type of the display is not particularly limited, and examples include a liquid crystal display device (LCD), an organic EL display, an inorganic EL display, a field emission display (FED), an electrophoretic display, etc.

[0088] The device including the display device of the present invention is not particularly limited, and examples include mobile phones, smartphones, wristwatch-type terminals and other mobile terminals, personal computers, televisions, large screens, digital signage (electronic billboards, electronic bulletin boards), etc.

[0089] The film of the present invention can also be applied to TFT substrates for organic EL displays, members for touch panels, flexible printed circuits, members for solar cell panels such as surface protective films and substrate materials, members for optical waveguides, and other semiconductor-related members.

Examples

[0090] The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to the following examples. In the following, "parts" and "%" are based on mass unless otherwise specified.

[0091] <Measurement method> The physical properties of the polyamide resin and polyamide film prepared in the examples were measured as follows.

[0092] (1) Film thickness of the film The film thickness of the prepared film was measured using a micrometer (manufactured by Mitutoyo).

[0093] (2) YI value (Yellow Index) The prepared film was cut into a size of 30 mm × 30 mm, and in accordance with ASTM D1925, the YI value (measured value) of each film was determined using a spectrophotometer (manufactured by Konica Minolta, product number: CM-5). Each measured YI value was normalized by the film thickness (50 μm thickness) according to the following formula to obtain the YI value (converted to 50 μm). YI value (converted to 50 μm) = YI value (measured value) × film thickness / 50 μm

[0094] (3) Yield strength and yield strain The fabricated film was cut into a predetermined size, and the yield strength and yield strain (ε) were measured using a small bench-top testing machine (manufactured by Shimadzu Corporation, product number: EZ-SX). The strain was determined by the following equation (2), and the elastic modulus was determined from the slope of the obtained stress-strain diagram when the stress was between 5 MPa and 10 MPa. The strain and stress at the 0.2% proof stress point on the stress-strain curve were defined as the yield strain and yield strength, respectively. The measurement was performed with n = 3, and the average value of the obtained measurement results is shown in Table 1. Strain = (L 1 - L 0 ) / L 0 (2) L 0 is the initial length of the film used for the measurement, and L 1 is the length of the film under a certain stress. [Test Conditions] Sample size: 100 mm × 10 mm Distance between grips: 50 mm Speed: 5 mm / min Number of measurements: 3 times

[0095] (4) Evaluation of resilience Resilience was evaluated by R in the following equation (1), R = α·ε / 2 (1) α and ε are the yield strength (unit: MPa) and yield strain obtained from the above measurement.

[0096] (5) Weight-average molecular weight (Mw) The weight-average molecular weight (Mw) is the polystyrene-equivalent amount determined by gel permeation chromatography (GPC) measurement. The conditions for GPC measurement are as follows. Apparatus: GL7700 manufactured by GL Sciences Column: TSKgel αM (manufactured by Tosoh Corporation) Column internal temperature: 40 °C Eluent composition: 100 mmol / L of H 3 PO 4 (H 3 PO 4 85% aqueous solution was used as a raw material) and an NMP solution containing 10 mmol / L of LiBr Eluent flow rate: 0.7mL / min Calibration standard: Polystyrene Detector wavelength: 260nm and 300nm Detector temperature: Room temperature Baseline range at analysis: 15 to 40 minutes Molecular weight calculation range during analysis: 20 to 35 minutes

[0097] <Production of polyamideimide> A 100 mL reactor was filled with 60.0 g of N,N-dimethylacetamide (DMAc) and 4.849 g (15.14 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB). Next, 1.007 g (3.245 mmol) of 3,4-oxydiphthalic dianhydride (aODPA) and 1.007 g (3.245 mmol) of 4,4'-oxydiphthalic dianhydride (sODPA) were added to the TFMB solution and reacted at 30°C for 2 hours with stirring to obtain a solution containing a polymer having an imide precursor structure. Thereafter, 1.757 g (8.653 mmol) of terephthalic acid chloride (TPC) was added to this solution, and the solution was stirred and reacted for 1.5 hours while maintaining the liquid temperature at 30° C., to obtain a solution containing a copolymer having an imide precursor structure and an amide structure. Then, 2.09g of pyridine, 2.45g of acetic anhydride, and 8.53g of DMAc were added and stirred at 20-30°C for 8 hours to obtain a polyamideimide solution. 99g of DMAc was further added and stirred until homogenous, after which the solution was gradually poured into a container containing 4L of methanol to cause precipitation, and the precipitated solid was filtered and pulverized, and then dried at 80°C in vacuum for 18 hours to obtain 8.0g of polyamideimide copolymer (PAI) as a solid powder. The weight average molecular weight in terms of polystyrene measured by GPC was 221,000.

[0098] <Film Preparation> A polyamide-imide resin (PAI) powder and a thermally reactive crosslinking agent were dissolved in a solvent (DMAc) in the amounts shown in Table 1 (shown in parts by mass of solid content) to adjust the solid content concentration to 13% by mass, and then a fibrous alumina filler dispersion was added, dispersed, and homogenized to prepare a resin composition for film production. Next, this resin composition was applied onto a glass plate using a table coater (AFA-standard manufactured by Coatec Co., Ltd.) with an applicator so that the final film thickness was about 50 μm, and then dried in a precision thermostat (Fine Oven DH612 manufactured by Yamato Scientific Co., Ltd.) at 120° C. for 20 minutes, then at 220° C. for 30 minutes, and peeled off from the glass plate to form a film. The evaluation of each of the obtained films is shown in Table 1.

[0099] [Table 1]

[0100] The components used in Table 1 are as follows: · Pseudoboehmite filler Alumina filler manufactured by Kawaken Fine Chemicals (average fiber diameter: 5 nm, average fiber length 800 nm, added as a slurry dispersed in DMAc at a concentration of 10%, values ​​in the table exclude solvent) Sanwa Chemical's Nikalac MW-390 TIFF2025087504000005.tif36162·Miki Riken Resin MM-630 Hexamethylolmelamine compound · Sanwa Chemical Co., Ltd. TTMOBGN Alkoxymethylol benzoguanamine compounds Mitsubishi Chemical JER828 Bisphenol A type epoxy resin Epoxy equivalent: 184-194g / eq Mitsubishi Chemical TAIC Triallyl isocyanurate ·K·I Chemical Co., Ltd. BMI-80 TIFF2025087504000006.tif29162

[0101] As shown in Table 1, the films of the examples had low yellowness while maintaining good resilience. On the other hand, the films of Comparative Examples 2 to 4, which used a crosslinking agent other than component (C), were inferior in at least either resilience or yellowness. [Industrial Applicability]

[0102] According to the resin composition for films of the present invention, a film having low yellowness while maintaining good resilience is provided. This film is expected to be unlikely to develop folding marks even if it is repeatedly folded or kept in a folded state for a long period of time, and is therefore highly useful in industry.

Claims

1. One or more resins (A) selected from polyamideimide resin and polyamide resin, fibrous alumina filler (B), and a crosslinking agent (C) containing two or more functional groups selected from methylol group and alkoxymethyl group, a resin composition.

2. The resin composition according to Claim 1, wherein the component (A) is a polyamideimide resin.

3. The resin composition according to Claim 1, wherein the component (B) is a boehmite-type or pseudo-boehmite-type alumina filler.

4. The resin composition according to Claim 1, wherein the component (C) is a crosslinking agent having a melamine skeleton or a crosslinking agent having a benzoguanamine skeleton.

5. The resin composition according to Claim 1, wherein the component (B) is 1 to 50 parts by mass and the component (C) is 0.1 to 50 parts by mass with respect to 100 parts by mass of the component (A).

6. A film made using the resin composition according to any one of Claims 1 to 5.

7. The film according to Claim 6, wherein R according to the following formula (1) is 0.93 to 2.00 MPa. R = α・ε / 2 (1) In the formula, α is the yield strength (unit: MPa) and ε is the yield strain.

8. The film according to Claim 6, wherein the yellow index is 0 or more and 3.0 or less.

9. A display device provided with the film according to Claim 6.

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