Resin composition and film therewith

Abstract

To provide, as a film, a resin composition that, while maintaining transparency as a film, combines excellent elasticity (in particular, average elasticity in an MD direction and a TD direction being 6.0 GPa or more ).SOLUTION: A resin composition contains a resin component and a fibrous alumina filler, where the resin component includes at least a resin having an amide structure, and the fibrous alumina filler is characterized by being dispersed in the resin composition with an average diameter of 4 nm to 30 nm and an average fiber length of 200 nm to 4,000 nm.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 a film using the same.

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. As a member such as a cover window used for a flexible display constituting such a foldable device, it has been necessary to have flexibility in addition to transparency. Specifically, a member having extremely high flexibility capable of realizing a 180° bend with a small bending radius of about 2.5 mm has been demanded.

[0003] Conventionally, as a material to replace rigid glass, materials made of flexible organic polymers have been variously studied. For example, from the viewpoints of transparency and heat resistance, films containing polyimide resins have been studied and proposed as flexible organic polymers.

[0004] However, in a flexible display using a film containing such a flexible organic polymer, when operating by finger touch or a touch pen, or even when holding the display in a folded state for a long time, compression marks or bending marks may occur on the display surface. Therefore, as a film for such a flexible display, it has been required to have both high flexibility and a high elastic modulus.

[0005] Conventionally, as a film for a flexible display having heat resistance, transparency, mechanical strength, surface hardness, and bend resistance, a polyimide resin composition containing a polyimide resin having a specific molecular structure and silica fine particles has been proposed (see Patent Document 1).

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] International Publication No. 2016 / 060213 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] However, in the recent field of foldable devices, with the further improvement of functionality and productivity, and the diversification of designs and applications, as a member, a higher elastic modulus (particularly, the average elastic modulus in the MD direction and the TD direction is 6.0 GPa or more) is required, and the polyimide resin composition of Patent Document 1 is not sufficient. In addition, as a film for a display, excellent transparency is also required, but it has been difficult to improve the elastic modulus while maintaining transparency.

[0008] Therefore, the main object of the present invention is to provide a resin composition that, as a film, has a good elastic modulus (particularly, the average elastic modulus in the MD direction and the TD direction is 6.0 GPa or more) while maintaining transparency. Another object of the present invention is to provide a film made of the above resin composition. [Means for Solving the Problems]

[0009] The inventors of the present invention have intensively studied to achieve the above object. As a result, according to a resin composition containing at least a resin having an amide structure and in which fibrous alumina fillers are dispersed in a specific fiber dimension state in the composition of such resin, it has been found that a resin composition having a high elastic modulus while maintaining transparency, which could not be achieved in the prior art, can be provided, and the present invention has been completed.

[0010] That is, the resin composition of the present invention is a resin composition containing a resin component and fibrous alumina filler, the resin component includes at least a resin having an amide structure, and the fibrous alumina filler is dispersed in the resin composition in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm.

[0011] Here, in the present invention, the "alumina" of the fibrous alumina filler in the resin composition includes alumina and alumina hydrate, and examples of the alumina hydrate include boehmite form, pseudo-boehmite form, etc. In addition, the "average fiber diameter" and "average fiber length" of the fibrous alumina filler refer to observing the fibrous alumina filler in the resin composition in an electron microscope image, and taking the average measured length value of the diameters in the short side direction of 50 arbitrarily selected fibrous alumina fillers as the "average fiber diameter", and the average measured length value in the long side direction as the "average fiber length".

[0012] In the resin composition of the present invention, it is preferable that the fibrous alumina filler is a boehmite form or pseudo-boehmite form alumina filler. Also, it is preferable that the fibrous alumina filler is contained in an amount of 1 to 50 parts by mass based on 100 parts by mass of the resin.

[0013] In the resin composition of the present invention, it is preferable that the resin having at least an amide structure includes a polyamide-imide resin or a polyamide resin.

[0014] The film of the present invention is characterized by being made of the above resin composition. It is preferable that a protective layer is laminated on at least one surface side of the film of the present invention. The resin composition or film of the present invention is preferably used as a member for a display.

[0015] That is, the gist configuration of the present invention is as follows. [1] A resin composition containing a resin component and fibrous alumina filler, The resin component contains at least a resin having an amide structure. The fibrous alumina filler is characterized in that, in the resin composition, it is dispersed in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm. [2] The resin composition according to [1], wherein the fibrous alumina filler is a boehmite-type or pseudo-boehmite-type alumina filler. [3] The resin composition according to [1] or [2], wherein the fibrous alumina filler is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the resin having at least an amide structure. [4] The resin composition according to any one of [1] to [3], wherein the resin having at least an amide structure contains a polyamide-imide resin or a polyamide resin. [5] A film comprising the resin composition according to any one of [1] to [4]. [6] A film in which a protective layer is laminated on one surface side of the film according to [5]. [7] A display member using the resin composition according to any one of [1] to [4] or the film according to [5] or [6].

Advantages of the Invention

[0016] According to the present invention, as a film, it is possible to provide a resin composition that exhibits an effect that could never be achieved by the prior art, having good elastic modulus (particularly, the average elastic modulus in the MD direction and the TD direction is 6.0 GPa or more) while maintaining transparency. Further, according to the present invention, it is possible to provide a film having the above-described effects and comprising the above resin composition.

Embodiments for Carrying Out the Invention

[0017] The resin composition of the present invention will be described in detail below. The resin composition of the present invention is a resin composition containing a resin component and fibrous alumina filler, wherein the resin component includes at least a resin having an amide structure, and the fibrous alumina filler is dispersed in the resin composition in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm.

[0018] [Resin component] The resin component constituting the resin composition of the present invention includes at least a resin having an amide structure. Examples of the resin having at least an amide structure include polyamide resins having a structure in which structural units containing an amide structure are polymerized. Further, the resin having at least an amide structure may be a resin having an amide structure and an imide structure, for example, a polyamideimide resin having a structure in which a structural unit containing an imide structure and a structural unit containing an amide structure are copolymerized. In the resin composition containing at least a resin component having an amide structure, since the fibrous alumina filler described later is dispersed in a specific fiber dimension state, a film made of such a resin composition can achieve two characteristics that are difficult to achieve simultaneously, namely excellent transparency and high elasticity, at a high level. Furthermore, it can also be advantageous for realizing excellent thermal dimensional stability (thermal properties).

[0019] [Polyamideimide resin] The 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, which are 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 with a dicarboxylic acid compound. Then, it can be obtained by subjecting the imide precursor structure in the copolymer to a ring-closing reaction (imidation). Further, 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.

[0020] That is, the polyamide-imide resin in the resin composition of the present invention 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 polyamide-imide resin preferably contains at least one structure selected from the group consisting of a structure in which residues obtained by reacting the diamine compound and the tetracarboxylic acid compound are linked by an alkylene group which may be substituted with a fluorine atom, an aliphatic ring, and aromatic rings with a sulfonyl group or a fluorine atom.

[0021] Examples of the diamine compound used for synthesizing the polyamide-imide resin in the resin composition of the present invention include aliphatic diamines, aromatic diamines, and mixtures thereof. Here, the "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 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, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferably used. The "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 in a part of its structure. The diamine compound can be used alone or in combination of two or more.

[0022] Specific examples of the aliphatic diamine 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.

[0023] 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.

[0024] 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 fluorine group, a trifluoromethyl group, or a trifluoromethoxy group, specifically, 2,2'-bis(trifluoromethyl)benzidine is more preferably used.

[0025] Examples of the tetracarboxylic acid compound used for synthesizing the polyamideimide resin in the resin composition of the present invention include tetracarboxylic acids or tetracarboxylic acid derivatives. Examples of the tetracarboxylic acid derivatives include anhydrides of tetracarboxylic acids, preferably dianhydrides, acid chlorides, and the like. Examples of the tetracarboxylic acid compounds 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.

[0026] 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 non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4'-oxydiphthalic dianhydride (sODPA), 3,4-oxydiphthalic dianhydride (aODPA), 4,4'-(4,4'-isopropylidenediphenoxy)diphthalic dianhydride (BPADA), 3,3',4,4'-benzophenone tetracarboxylic dianhydride, 2,2',3,3'-benzophenone tetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride (sBPDA), 2,2',3,3'-biphenyltetracarboxylic dianhydride (aBPDA), 3,3',4,4'-diphenylsulfone tetracarboxylic 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 monocyclic aromatic tetracarboxylic dianhydrides include 1,2,4,5-benzenetetracarboxylic dianhydride, and examples of condensed polycyclic aromatic tetracarboxylic dianhydrides include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

[0027] Examples of the aliphatic tetracarboxylic dianhydride 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 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, 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.

[0028] Among tetracarboxylic acid compounds, from the viewpoint of improving the flexural 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) are preferably used in combination, and the composition ratio (any one of 6FDA:sBPDA, BPAF, CBDA, HBPDA) 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.

[0029] 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.

[0030] As the dicarboxylic acid compound used in the synthesis of the polyamideimide resin in the resin composition of the present invention, there are dicarboxylic acids or dicarboxylic acid derivatives. Examples of the dicarboxylic acid derivatives include acid chlorides and ester forms of the dicarboxylic acids. The dicarboxylic acid compound can be used alone or in combination of two or more.

[0031] 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 alicyclic dicarboxylic acids or aromatic dicarboxylic acids such as compounds linked by a phenylene group and their derivatives (for example, acid chlorides, acid anhydrides); aliphatic dicarboxylic acids such as dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms and their derivatives (for example, acid chlorides, ester forms), etc. These dicarboxylic acid compounds can be used alone or in combination of two or more.

[0032] Among these, from the viewpoint of improving the elongation at break and elastic modulus as a film, terephthalic acid or 4,4'-oxybisbenzoic acid or its derivatives, 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.

[0033] 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%, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 40 mol% or more. 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.

[0034] For example, in the synthesis of the polyamide-imide resin of the resin composition of the present invention, 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 monomer components described above, 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 making the composition ratio of the imide structure and the amide structure the above-mentioned composition ratio, excellent flexibility and high elasticity can be achieved in a well-balanced manner.

[0035] 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. However, chemical imidization is preferred because colorless transparency is easily maintained.

[0036] 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.

[0037] Examples of the condensing agent used for chemical imidization include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride, and phosphorous acid esters such as trimethyl 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.

[0038] 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.

[0039] The ring-closing reaction conditions for the synthesis of the polyamideimide resin of the resin composition of the present invention can be 1 to 27 hours at 10 to 50°C, and from the viewpoint of maintaining colorless transparency, it is preferably synthesized under a nitrogen atmosphere.

[0040] The weight average molecular weight (Mw) of the polyamideimide resin in the resin composition of the present invention 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 elongation at break. 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.

[0041] In the resin composition of the present invention, the content of the polyamideimide resin in the non-volatile component is preferably in the range of 50 to 96% by mass, more preferably in the range of 59 to 90% by mass, and even more preferably in the range of 67 to 83% by mass, from the viewpoints of maintaining colorless transparency and improving the elongation rate.

[0042] [Polyamide resin] A polyamide resin can be used in the resin composition of the present invention. The polyamide resin in the resin composition of the present invention can be obtained by reacting a diamine compound and a dicarboxylic acid compound which are monomer components. The dicarboxylic acid compound is a dicarboxylic acid and its derivatives (such as acid chloride, ester, acid anhydride, etc.).

[0043] That is, the polyamide resin in the resin composition of the present invention 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 the structure connecting the monomer components constituting the polyamide resin, it is more preferably composed of an amide structure and does not substantially contain a structure other than the amide structure.

[0044] Here, regarding the diamine compound, the description (including examples and preferred examples) regarding the diamine compound described in the section of 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 of the above polyimideamide resin is applicable.

[0045] 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 fluorine group, a trifluoromethyl group, or a trifluoromethoxy group, specifically, 2,2'-bis(trifluoromethyl)benzidine is more preferably used.

[0046] 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 abbreviated as TPC) or 4,4'-oxybis(benzoyl chloride) (4,4'-diphenyl ether dicarboxylic acid chloride, sometimes abbreviated 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 OBBC will be introduced into the polyamide resin.

[0047] The polyamide resin preferably contains the following structure (1) and / or (2) as a repeating unit, and more preferably 10 to 100 mol% of all the repeating units are the following structure (1) and / or (2). It is particularly preferable that all the repeating units substantially consist of the following structure (1) and / or (2).

Chemical formula

[0048] 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. As the method for producing the polyamide resin of the present invention, in particular, a solution polymerization method and an interfacial polymerization method can be preferably used.

[0049] 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.

[0050] 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 ethylene oxide, propylene oxide, 1,2-butylene oxide, ammonia, and pyridine are used.

[0051] 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. Stepwise reaction methods, and methods in which all diamine compounds are mixed and added, and then dicarboxylic acid dichloride is added and reacted, etc. can be used. Also, when using two or more kinds of dicarboxylic acid dichlorides, similarly, stepwise methods, simultaneous addition methods, etc. can be used. The molar ratio of all diamine compounds to all dicarboxylic acid dichlorides (number of moles of all diamine compounds: number of moles of all 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.

[0052] When a diamine compound and a dicarboxylic acid dichloride are used as raw materials, the terminal groups will be amine-terminated or carboxylic acid-terminated depending on the composition ratio of the raw materials. From the perspective of improving the colorless transparency of the film, it is preferable to perform end-capping with other amines, carboxylic acid chlorides, or carboxylic acid anhydrides.

[0053] 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 necessary, and in this case, the terminal groups can also be used as crosslinking points.

[0054] In the production of the polyamide resin, examples of the aprotic polar solvent to be used include sulfoxide solvents such as dimethyl sulfoxide and diethyl sulfoxide, formamide solvents such as N,N-dimethylformamide and N,N-diethylformamide, acetamide solvents such as N,N-dimethylacetamide and N,N-diethylacetamide, pyrrolidone 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.

[0055] The reaction conditions for the synthesis of the polyamide resin can be 10 to 50 °C for 10 minutes to 27 hours, and from the viewpoint of maintaining colorless transparency, the synthesis may be carried out under a nitrogen atmosphere.

[0056] From the viewpoint of improving the 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.

[0057] 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.

[0058] 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. The number average molecular weight (Mn) and the weight average molecular weight (Mw) refer to values measured by GPC (gel permeation chromatography) and calculated in terms of polystyrene conversion.

[0059] In the non-volatile component of the resin composition of the present invention, the content of the polyamide resin is preferably in the range of 50 to 96% by mass, more preferably in the range of 59 to 90% by mass, and even more preferably in the range of 67 to 83% by mass, from the viewpoints of maintaining colorless transparency and improving elongation.

[0060] In the resin composition of the present invention, a mixture of a polyimide resin composed of a structural unit containing an imide structure and a polyamide resin composed of a structural unit containing an amide structure can also be used. For example, when synthesizing the above-mentioned polyamideimide, in the polyamideimide resin solution, a polyimide resin composed only of a structural unit containing an imide structure and a polyamide resin composed only of a structural unit containing an amide structure may be by-produced without copolymerizing the structural unit containing an imide structure and the structural unit containing an amide structure. A mixture of any two or more of such polyamideimide resin, polyimide resin, and polyamide resin can also be preferably used in the present invention. Also, these resins may be synthesized individually and then mixed.

[0061] [Fibrous alumina filler] The fibrous alumina filler constituting the resin composition of the present invention is characterized in that it is dispersed in a resin composition containing the resin component described above 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, thereby suppressing a decrease in transparency and imparting a remarkable effect of increasing elasticity. In addition, the fibrous alumina filler in the present invention can also impart an excellent anti-blocking effect without impairing light transmittance as compared with spherical or amorphous fillers. Specifically, when films made of the resin composition of the present invention are stacked or wound in a roll for storage, the above-described fibrous alumina filler suppresses sticking (blocking) between the films, and can improve storage stability and workability.

[0062] The fibrous alumina filler in the resin composition of the present invention is dispersed in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm, preferably in a state where the average fiber diameter is 2 to 25 nm and the average fiber length is 200 to 3,000 nm, more preferably in a state where the average fiber diameter is 3 to 20 nm and the average fiber length is 500 to 2,000 nm. If the fibrous alumina filler is dispersed in the resin composition in a state where the average fiber diameter and the average fiber length are within the above-described ranges, the film made of this resin composition can achieve high elasticization while maintaining transparency. In addition, 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 obtained by diluting the resin composition ten thousand 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 Ind., 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, the fibrous alumina filler to be measured may be in any state of a single fiber or a fiber bundle formed by aggregation of a plurality of single fibers, as long as it can be visually recognized as a single fiber in an electron microscope image. 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".

[0063] The fibrous alumina filler constituting the resin composition of the present invention is blended and stirred in the above-described resin component in the form of a powder or a dispersion liquid (sol) described later, and kneaded as necessary, thereby adjusting the dispersion state in the resin composition, that is, the "average fiber diameter" and the "average fiber length". For example, stirring or kneading can be performed using a stirrer such as a dissolver or a butterfly mixer, a kneader such as a roll mill or a bead mill, etc. 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 blade / kneading device, the stirring / kneading time, the stirring / kneading temperature, the bead filling rate, and the roll gap.

[0064] The content of the fibrous alumina filler in the resin composition of the present invention is preferably 1 to 50 parts by mass, more preferably 5 to 40 parts by mass, and still more preferably 10 to 30 parts by mass with respect to 100 parts by mass of the resin having at least an amide structure. If the content of the fibrous alumina filler is within the above-described range, it is possible to increase the elasticity while maintaining transparency as a film.

[0065] The fibrous alumina filler in the resin composition of the present invention can be surface-treated or used as a dispersion liquid (sol) dispersed in an organic solvent or the like. By surface-treating or blending as a dispersion liquid, the dispersion state in the resin composition can be stabilized. Among them, 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, that is, the "average fiber diameter" and the "average fiber length", the resin composition of the present invention can be produced with high productivity.

[0066] The method for surface treatment or dispersion liquid of the fibrous alumina filler is not particularly limited. For example, a surface treatment method using a coupling agent such as a silane-based, titanate-based, aluminate-based, or zirconium aluminate-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.

[0067] The fibrous alumina filler in the resin composition of the present invention is preferably a boehmite-type or pseudo-boehmite-type alumina filler. When the resin component contains a polyamide resin, it is preferable to use a fibrous alumina filler which is a boehmite-type or pseudo-boehmite-type alumina filler. Examples of the fibrous alumina filler ((B) component) include the aluminosol series manufactured by Kawaken Fine Chemicals Co., Ltd.

[0068] [(Meth)acrylate compound having a molecular weight of 10,000 or less or a blocked isocyanate compound having an isocyanuric ring] From the viewpoint of relaxing external stresses such as dry shrinkage, bending, and compression in the film manufacturing process, the resin composition of the present invention can contain a (meth)acrylate compound having a molecular weight of 10,000 or less or a blocked isocyanate compound having an isocyanuric ring. The blending amount of the (meth)acrylate compound having a molecular weight of 10,000 or less or the blocked isocyanate compound having an isocyanuric ring is preferably 0.1 part by mass to 100 parts by mass, more preferably 1 part by mass to 50 parts by mass, and particularly preferably 2 parts by mass to 20 parts by mass with respect to 100 parts by mass of the resin having at least an amide structure.

[0069] [(Meth)acrylate compound having a molecular weight of 10,000 or less] As the (meth)acrylate compound, known and commonly used (meth)acrylate-based oligomers and (meth)acrylate-based monomers can be used. The (meth)acrylate compound may be used alone or in combination of two or more.

[0070] Examples of the (meth)acrylate oligomers include epoxy (meth)acrylates such as phenol novolak epoxy (meth)acrylate, cresol novolak epoxy (meth)acrylate, and bisphenol type epoxy (meth)acrylate, urethane (meth)acrylate, epoxy urethane (meth)acrylate, polyester (meth)acrylate, polyether (meth)acrylate, polybutadiene-modified (meth)acrylate, and the like.

[0071] Examples of (meth)acrylate monomers include (meth)acrylamides such as acrylamide, methacrylamide, N-hydroxymethylacrylamide, N-hydroxymethylmethacrylamide, N-methoxymethylacrylamide, N-ethoxymethylacrylamide, and N-butoxymethylacrylamide; allyl compounds such as triallyl isocyanurate, diallyl phthalate, and diallyl isophthalate; esters of (meth)acrylic acid such as 2-ethylhexyl (meth)acrylate, lauryl (meth)acrylate, tetrahydrofurfuryl (meth)acrylate, isobornyl (meth)acrylate, phenyl (meth)acrylate, and phenoxyethyl (meth)acrylate; hydroxyalkyl (meth)acrylates such as hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, and pentaerythritol tri(meth)acrylate; alkoxyalkylene glycol mono(meth)acrylates such as methoxyethyl (meth)acrylate and ethoxyethyl (meth)acrylate; alkylene polyol poly(meth)acrylates such as ethylene glycol di(meth)acrylate, tripropylene glycol di(meth)acrylate, butanediol di(meth)acrylate, neopentyl glycol di(meth)acrylate, 1,6-hexanediol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, and dipentaerythritol hexa(meth)acrylate; polyoxyalkylene glycol poly(meth)acrylates such as diethylene glycol di(meth)acrylate, triethylene glycol di(meth)acrylate, ethoxylated trimethylolpropane triacrylate, trimethylolprohantri(meth)acrylate, and propoxylated trimethylolpropane tri(meth)acrylate; poly(meth)acrylates such as neopentyl glycol hydroxypivalate ester di(meth)acrylate; and isocyanurate-type poly(meth)acrylates such as tris[(meth)acryloxyethyl] isocyanurate.

[0072] [Block isocyanate compound having an isocyanurate ring] The resin composition of the present invention can contain a block isocyanate compound having an isocyanurate ring. The blocked isocyanate group contained in this block isocyanate compound having an isocyanurate ring is a group in which the isocyanate group is protected by reaction with a blocking agent and temporarily inactivated. When heated to a predetermined temperature, the blocking agent cleaves to generate an isocyanate group. Therefore, even after coating, the reaction via the isocyanate group of the block isocyanate compound having an isocyanurate ring does not proceed until the drying step.

[0073] As the block isocyanate compound having an isocyanurate ring, an addition reaction product of an isocyanate compound and an isocyanate blocking agent is used. Examples of the isocyanate compound having an isocyanurate ring that can react with the blocking agent include 1,3,5-tris[(5-isocyanato-1,3,3-trimethylcyclohexyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, 2,4,6-trioxohexahydro-1,3,5-triazine-1,3,5-triyltris(6,1-hexanediyl)trisisocyanate, 1,3,5-tris[3-(isocyanatomethyl)phenyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, and the like.

[0074] Examples of the isocyanate blocking agent include phenolic blocking agents such as phenol, cresol, xylenol, chlorophenol, and ethylphenol; lactam-based blocking agents such as ε-caprolactam, δ-valerolactam, γ-butyrolactam, and β-propiolactam; active methylene-based blocking agents such as ethyl acetoacetate and acetylacetone; alcohol-based blocking agents such as methanol, ethanol, propanol, butanol, amyl alcohol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, diethylene glycol monomethyl ether, propylene glycol monomethyl ether, benzyl ether, methyl glycolate, butyl glycolate, diacetone alcohol, methyl lactate, and ethyl lactate; oxime-based blocking agents such as formaldehyde oxime, acetaldehyde oxime, acetoxime, methyl ethyl ketoxime, diacetyl monoxime, and cyclohexanone oxime; mercaptan-based blocking agents such as butyl mercaptan, hexyl mercaptan, t-butyl mercaptan, thiophenol, methyl thiophenol, and ethyl thiophenol; acid amide-based blocking agents such as acetamide and benzamide; imide-based blocking agents such as succinimide and maleimide; amine-based blocking agents such as xylylidene, aniline, butylamine, and dibutylamine; imidazole-based blocking agents such as imidazole and 2-ethylimidazole; imine-based blocking agents such as methyleneimine and propyleneimine; pyrazole-based blocking agents such as dimethylpyrazole; maleic acid ester-based blocking agents such as diethyl maleate, and the like.

[0075] The cleavage temperature of the blocked isocyanate compound having an isocyanuric ring is preferably 100°C or higher. If it is 100°C or higher, the increase in viscosity is suppressed until the drying step of film formation, and the coatability is maintained.

[0076] Commercially available blocked isocyanate compounds having an isocyanurate ring of the present invention can be used. For example, BI7951 and BI7982 manufactured by TRIXENE can be mentioned. Further, such blocked isocyanate compounds having an isocyanurate ring can be used alone or in combination of two or more.

[0077] [Compound containing two or more kinds of functional groups selected from methylol group and alkoxymethyl group] The resin composition of the present invention can contain a compound containing two or more kinds of functional groups selected from methylol group and alkoxymethyl group. By containing a compound containing two or more kinds of functional groups selected from methylol group and alkoxymethyl group, the resilience of the film made of the resin composition of the present invention can be improved. Therefore, even if the film is repeatedly folded or held in a folded state for a long time, it is expected that folding marks are less likely to occur.

[0078] Compounds containing two or more kinds of functional groups selected from methylol group and alkoxymethyl group can be used alone or in combination of two or more. In the present invention, the alkoxymethyl group is a group represented by -CH 2 -O-R, and 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.

[0079] As the one or more kinds of functional groups selected from methylol group and alkoxymethyl group, a methylol group or a methoxymethyl group is preferable.

[0080] Compounds containing two or more kinds of functional groups selected from methylol group and alkoxymethyl group can be crosslinking agents having a melamine skeleton, crosslinking agents having a guanamine skeleton, crosslinking agents having a glycoluril skeleton, etc. These types of compounds containing two or more methylol groups or alkoxymethyl groups are preferable. These types of compounds known as heat-reactive crosslinking agents can also be used.

[0081] The crosslinking agent having a melamine skeleton is a compound having a melamine structure and containing two or more functional groups selected from methylol groups and alkoxymethyl groups, and the compound represented by the formula (3) can be used. These oligomers can also be used. [Chemical formula] In the formula, R 1 is a hydrogen atom or an alkyl group (preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group, and particularly preferably a methyl group).

[0082] The crosslinking agent having a benzoguanamine skeleton is a compound having a benzoguanamine structure and containing two or more functional groups selected from methylol groups and alkoxymethyl groups, and the compound represented by the formula (4) can be used. These oligomers can also be used. [Chemical formula] In the formula, R 2 is a hydrogen atom or an alkyl group (preferably an alkyl group having 1 to 6 carbon atoms, more preferably a methyl group or an ethyl group).

[0083] The crosslinking agent having a glycoluril skeleton is a compound having a glycoluril structure and containing two or more functional groups selected from methylol groups and alkoxymethyl groups, and examples thereof include 1,3,4,6-tetrakis(hydroxymethyl)glycoluril, 1,3,4,6-tetrakis(methoxymethyl)glycoluril, and 1,3,4,6-tetrakis(butoxymethyl)glycoluril.

[0084] As the compound containing two or more functional groups selected from methylol groups and alkoxymethyl groups, hexamethylol melamine, hexamethoxymethyl melamine, tetramethylol benzoguanamine, tetramethoxymethyl benzoguanamine, and their oligomers are preferred.

[0085] [Other components] The resin composition of the present invention may further contain additives or resin components other than resins having at least an amide structure, as long as the effects of the present invention are not impaired.

[0086] Examples of the additives include organic carboxylic acid compounds such as acetic acid, benzoic acid, terephthalic acid, citric acid, succinic acid, and lactic acid, organic phosphoric acid compounds such as mono(di)methyl phosphate, mono(di)butyl phosphate, and phenylphosphonic acid, and organic sulfonic acid compounds such as benzenesulfonic acid, p-toluenesulfonic acid, and dodecylbenzenesulfonic acid, from the viewpoint of modifying the fibrous alumina filler and stabilizing the solution viscosity of the resin composition, and surfactants for improving film-forming properties and defoaming properties.

[0087] Examples of the resin components other than resins having at least an amide structure include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyimide resins, polyphenylene sulfide resins, polyether ether ketone resins, polyether sulfone resins, polycarbonate resins, polyetherimide resins, epoxy resins, phenol resins, glass-epoxy resins, polyphenylene ether resins, acrylic resins, polyolefin resins such as polyethylene and polypropylene, and polycycloolefins such as polynorbornene.

[0088] [Film] The film of the present invention is composed of the aforementioned resin composition. According to the present invention, as a film, it has high elastic characteristics (the average elastic modulus in the MD direction and the TD direction is 6.0 GPa or more) while maintaining transparency. In addition, as described later, the film of the present invention can also exhibit anisotropy in mechanical properties in the MD direction and the TD direction. For example, the elastic modulus in the MD direction can be 7.0 GPa or more. Furthermore, while the film of the present invention has high elasticity, it is also possible to further improve transparency. For example, the haze value of the film can be set to 1.0% or less, and the YI value can be set to 0 or more and 5.0 or less. Here, the elastic modulus, YI value, and haze of the film can be measured by the method of the examples. Furthermore, the film of the present invention can also be advantageous in terms of excellent thermal dimensional stability (thermal properties), excellent antiblocking properties, excellent storage stability of the film, and workability.

[0089] The film of the present invention preferably has a film thickness of 5 μm or more and 100 μm or less, and more preferably 10 μm or more and 70 μm or less. By setting the film thickness within the above-described range, excellent flexibility and excellent transparency can be realized even in the laminate described later.

[0090] [Method for producing film] As a method for producing the film of the present invention, a coating solution for film production in which the resin composition of the present invention is dissolved in a solvent is applied onto a support by a known coating means, dried as necessary, and then peeled off from the support. The coating means is not particularly limited as long as it can apply the desired film thickness. It should be noted that the coating amount of the above coating solution is preferably adjusted as appropriate so that the film thickness after drying of the coating film is within a predetermined range.

[0091] In the film formation using the resin composition of the present invention, depending on the coating means, the film may have anisotropy in mechanical strength. The reason is not clear, but since the fibrous alumina filler described above is contained in a dispersed state in the resin composition, when a coating means in which shear stress acts is applied, the fibrous alumina filler is oriented in the direction in which the shear stress acts, and as a result, it is considered that anisotropy in mechanical strength occurs in the obtained film. Note that the anisotropy in mechanical strength means that, for example, when producing a long film, the mechanical properties such as the tensile elastic modulus of the obtained film are different between the direction in which the coating film is formed (MD direction) and the direction orthogonal thereto (TD direction).

[0092] In the present invention, by making the organic solvent having a boiling point of 150°C or higher account for 90% by mass or more of all the solvents of the coating solution for film production, it is possible to suppress the anisotropy of the mechanical strength of the obtained film. When the organic solvent having a high boiling point is contained at a predetermined ratio, when drying the coating film coated with the resin varnish, the time for the fibrous alumina filler oriented in the coating film to relax is ensured. As a result, it is considered that the fibrous alumina filler can be dispersed in the dried coating film (i.e., the film) in a state close to non-orientation. When suppressing anisotropy, it is preferable that the organic solvent having a boiling point of 150°C or higher is contained at 92% by mass or more based on all the solvents.

[0093] As the organic solvent having a boiling point of 150°C or higher that can be used as the solvent of the coating solution for film production, from the viewpoint of the transparency of the film, etc., solvents having an ester group, an ether group, a ketone group, a hydroxyl group, a sulfone group, and a sulfinyl group, and amide solvents are preferable.

[0094] Examples of the solvent having an ester group include γ-butyrolactone (boiling point 204°C), ε-caprolactone (boiling point 230°C), γ-hexanolactone (boiling point 219°C), γ-valerolactone (boiling point 207°C), benzyl benzoate (boiling point 323°C), ethyl benzoate (boiling point 212°C), ethylene glycol monobutyl ether acetate (boiling point 191.5°C), ethylene glycol monoethyl ether acetate (boiling point 156.3°C), butyl lactate (boiling point 188°C), ethyl lactate (boiling point 154°C), ethyl 3-ethoxypropionate (boiling point 169°C), and the like.

[0095] Examples of the solvent having an ether group include 2-(2-butoxyethoxy)ethyl acetate (boiling point 245°C), 2-(2-ethoxyethoxy)ethyl acetate (boiling point 217°C), propyl cellosolve (boiling point 150°C), triethylene glycol dimethyl ether (boiling point 216°C), and the like.

[0096] Examples of solvents having a ketone group include cyclohexanone (boiling point 156 °C), 1-phenylethanone (boiling point 202 °C), benzaldehyde (boiling point 179 °C), etc.

[0097] Examples of solvents having a hydroxyl group include 2-methylphenol (boiling point 190 °C), 3-methylphenol (boiling point 202 °C), octyl alcohol (boiling point 195 °C), etc.

[0098] Examples of solvents having a sulfone group include methanesulfonic acid (boiling point 167 °C), dimethyl sulfone (boiling point 238 °C), diethyl sulfone (boiling point 238 °C), sulfolane (boiling point 285 °C), dapsone (boiling point 177 °C), etc.

[0099] Examples of solvents having a sulfinyl group include dimethyl sulfoxide (boiling point 189 °C), etc.

[0100] As amide solvents, N-methyl-2-pyrrolidone (boiling point 202 °C), N,N-dimethylformamide (boiling point 153 °C), N,N-dimethylacetamide (boiling point 165 °C), 3-butoxy-N,N-dimethylpropanamide (boiling point 252 °C), etc. can be used.

[0101] Among these solvents, from the viewpoint of reducing the YI value of the film, amide solvents are more preferable, and N,N-dimethylacetamide is particularly preferable.

[0102] As the solvent for the coating solution for film production, other solvents may be included in addition to the organic solvents with a boiling point exceeding 150°C as described above. For example, from the perspective of drying properties, solvents with a boiling point below 150°C may be included. Examples of such solvents include ester solvents such as methyl acetate, ethyl acetate, isopropyl acetate, propyl acetate, butyl acetate, dimethyl carbonate, propylene glycol monomethyl ether acetate, and methyl lactate; ether solvents such as tetrahydrofuran, dioxane, and dibutyl ether; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclopentanone; amide solvents such as 3-methoxy-N,N-dimethylpropanamide; and aromatic solvents such as toluene.

[0103] From the perspective of coatability, the resin composition according to the present invention preferably has a viscosity at 25°C of 10 to 50,000 cP, more preferably 100 to 40,000 cP, and even more preferably 100 to 30,000 cP. Note that by lowering the viscosity of the resin composition, the anisotropy of the mechanical strength when forming a film can also be reduced. The viscosity of the resin composition can be measured by a conventional method using a cone-plate viscometer.

[0104] As described above, after the coating solution for film production is applied, the solvent is removed by drying the coating film as necessary. Examples of the drying method include vacuum drying, heat drying, or a combination of these. When drying at normal pressure, it is preferably dried at 30 to 350°C, and from the perspective of obtaining a resin layer with high transparency, it is preferably dried at 60 to 250°C for about 30 seconds to 180 minutes. In such a drying method, stepwise drying such as gradually increasing the temperature from a low temperature can be performed within the above temperature and time ranges. Also, it is preferably dried under a nitrogen atmosphere.

[0105] [Laminated Film] The film of the present invention can be made into a laminated film by forming a functional layer such as a hard coat layer that functions as a protective layer for preventing the occurrence of scratches and other damages on at least one surface side of the film, if necessary. According to the film of the present invention, since the above-described film has a high elastic modulus without impairing transparency, it is possible to suppress the occurrence of warpage when forming a protective layer such as a hard coat layer, and it is excellent in flatness and can obtain a high surface hardness, and the occurrence of bending marks and compression marks can also be reduced.

[0106] The laminated film using the film of the present invention preferably has a thickness of the entire laminated film of 10 to 150 μm, and more preferably 25 to 100 μm. If the thickness of the entire laminated film is within the above range, a flexible and optically excellent display panel can be manufactured.

[0107] [Hard coat layer] As the hard coat layer, a publicly known and commonly used coating solution for hard coat (hard coat material) can be used, and any of photocurable and thermosetting hard coat materials can be used. Examples of commercially available products include X-48-500 manufactured by Shin-Etsu Chemical Co., Ltd. and Lucidia V-6841 manufactured by DIC Corporation, which are excellent in flexibility.

[0108] The hard coat layer preferably has a YI value of 4 or less, more preferably 1 or less, at a film thickness of 50 μm. If the YI value is 4 or less, a laminated film with suppressed yellowness (YI value) can be formed.

[0109] Also, the hard coat layer preferably has a pencil hardness (surface hardness) of 2H or more, more preferably 4H or more. If the pencil hardness is 2H or more, a laminated film excellent in scratch resistance can be formed. The pencil hardness can be measured in accordance with JIS K 5600-5-4.

[0110] Furthermore, the hard coat layer preferably has a film thickness of 1 μm or more and 50 μm or less, more preferably 5 μm or more and 20 μm or less. If the film thickness is 50 μm or less, a laminated film excellent in flexibility can be formed.

[0111] [Method for manufacturing a laminated film] As a method for manufacturing a laminated film using the film of the present invention, for example, a manufacturing method including a step of forming a film by the above-described film manufacturing method and a step of forming a protective layer such as a hard coat layer thereon can be mentioned.

[0112] The method for manufacturing the film is as described above, and the description thereof is omitted here. As a step of forming a hard coat layer as a protective layer on the film, a resin solution (hard coat material) for the hard coat layer is applied to one surface of the film manufactured by the above-described film manufacturing method by a known coating means, and dried and cured as necessary. The coating means is not particularly limited as long as it can be coated with the target film thickness. In addition, the coating amount of the resin solution for the hard coat layer varies depending on the performance required for the resulting laminated film, but it is preferably adjusted appropriately so that the film thickness after drying is within a predetermined range.

[0113] As described above, the solvent is removed from the coating film made of the resin solution for the hard coat layer by drying as necessary. Examples of the drying method include reduced pressure drying, heat drying, or a combination of these. When drying at normal pressure, it is preferably dried at 30 to 150 °C.

[0114] Furthermore, as a method for curing the hard coat layer, it is preferable to cure the coating film by at least one of light irradiation and heating according to the components of the resin solution (hard coat material).

[0115] [Member for display] As members for displays using the film and laminated film of the present invention, for example, there are members for use in foldable organic EL displays that are thin and bendable, portable terminals such as smartphones and wristwatch-type terminals, display devices inside automobiles, flexible panels used in wristwatches, etc. Further, it can also be applied to members for image display devices such as liquid crystal display devices and organic EL display devices, members for touch panels, flexible printed boards, members for solar cell panels such as surface protection films and substrate materials, members for optical waveguides, and other semiconductor-related members. Among them, it is preferably used for member applications such as cover windows and TFT substrates constituting foldable organic EL displays.

[0116] [Cover window of display] As a cover window of a display using the film of the present invention, for example, the above-described laminated film is arranged and used so as to be located on the surface of various displays. The method of arranging on the surface is not particularly limited, and examples include a method via an adhesive layer. As the material of the adhesive layer, conventionally known adhesive materials that can be used for adhering surface materials for displays can be used. Note that a fingerprint adhesion prevention layer may be further provided on the surface on the protective layer side such as a hard coat layer for the cover window of a display using the film or laminated film of the present invention.

[0117] [TFT substrate for organic EL display] As a TFT substrate for an organic EL display using the film of the present invention, for example, it can be obtained 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. Further, a structure necessary for an organic EL display can also be formed thereon by a known method, and the method of forming a circuit or the like is not particularly limited.

Examples

[0118] Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples. In the following, "parts" and "%" are all based on mass unless otherwise specified.

[0119] (Synthesis Example of Polyamide PA1) A 100 mL reactor was filled with 60.0 g of N,N-dimethylacetamide (DMAc), and 5.33 g (16.63 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) and 2.64 g (36.59 mmol) of 1,2-butylene oxide were added. Next, 0.97 g (3.29 mmol) of 4,4'-diphenylether dicarboxylic acid chloride (DEDC) and 2.67 g (13.17 mmol) of terephthalic acid chloride (TPC) were added to this solution of TFMB, and the mixture was stirred at 30 °C for 2 hours to react. Then, 0.026 g (0.33 mmol) of acetyl chloride was added to this solution, and the mixture was stirred at 30 °C for 30 minutes to react, obtaining a solution containing a polymer (PA1) having an amide structure. The weight average molecular weight in terms of polystyrene by GPC was 184,000.

[0120] Here, the conditions for GPC measurement are as follows. Apparatus: GL7700 manufactured by GL Science 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 (using an 85% aqueous solution as a raw material) and an NMP solution containing 10 mmol / L of LiBr Eluent flow rate: 0.7 mL / min Calibration standard reagent: Polystyrene Detector wavelength: 260 nm and 300 nm Detector temperature: Room temperature Baseline range during analysis: 15 minutes to 40 minutes Molecular weight calculation range during analysis: 20 to 35 minutes

[0121] (Synthesis Examples of Polyamides PA2 - 5) A solution containing polymers (PA2 - 5) having an amide structure was obtained in the same manner as PA1, except that the addition amounts (molar ratios) of TFMB, DEDC, and TPC were set to the values described in Table 1.

[0122] (Synthesis Example of Polyamide Imide PAI) A 100 mL reactor was filled with 60.0 g of DMAc, and 4.849 g (15.14 mmol) of TFMB was added. Subsequently, 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 this TFMB solution, and the mixture was stirred at 30 °C for 2 hours to react, obtaining a solution containing a polymer having an imide precursor structure. Thereafter, 1.37 g (19.03 mmol) of 1,2 - butylene oxide and 1.757 g (8.653 mmol) of TPC were added to this solution, and the mixture was stirred and reacted for 1.5 hours while maintaining the liquid temperature at 30 °C, obtaining a solution containing a copolymer having an imide precursor structure and an amide structure. Thereafter, 2.09 g of pyridine, 2.45 g of acetic anhydride, and 8.53 g of DMAc were added, and the mixture was stirred at 20 - 30 °C for 8 hours to obtain a polyamide imide solution. Further, 99 g of DMAc was added and stirred until it became uniform. Then, this solution was gradually poured into a container containing 4 L of methanol for precipitation. After the precipitated solid content was filtered and pulverized, it was dried in vacuo at 80 °C for 18 hours to obtain 8.0 g of a solid powder of the polyamide imide copolymer. The weight - average molecular weight in terms of polystyrene by GPC was 221,000.

[0123] The composition ratios of the monomer components used in the synthesis of polyamides PA1 - 5 are shown in Table 1.

[0124]

Table 1

[0125] (Preparation of Evaluation Samples (Films)) Using the compounding amounts shown in Table 2, powders of PA1-5 or PAI, a dispersant, and a fibrous alumina filler dispersion were compounded, and after adjusting with a solvent (DMAc) to a solid content concentration of 12.5% by weight, they were dispersed and homogenized to prepare a resin composition for film production. Next, this resin composition was coated on a glass plate using an applicator so that the film thickness of the finally obtained film would be 50 μm using a table coater (AFA-standard manufactured by Coattech Co., Ltd.), and dried in a precision thermostat (Fine Oven DH612 manufactured by Yamato Scientific Co., Ltd.) at 120 °C for 40 minutes and then at 220 °C for 30 minutes, and a film was formed by peeling it from the glass plate.

[0126] Regarding the evaluation samples of Examples 1-6 and Comparative Example 1 obtained in this way, the following evaluations were performed. These results are also shown in Table 2.

[0127] ·Film thickness The film thickness of each evaluation sample was measured using a micrometer (manufactured by Mitutoyo Corporation).

[0128] ·Elastic modulus and elongation at break evaluation Both the elastic modulus and elongation at break were measured using EZ-SX manufactured by Shimadzu Corporation under the following conditions. The elastic modulus was determined from the slope of the stress-strain diagram obtained when the strain was from 0.2% to 0.5%. For each evaluation sample, measurements were performed in the direction parallel (MD) and perpendicular (TD) to the coating direction of the film. In the evaluation samples of Examples 1-6, since anisotropy in the MD and TD directions was observed for the elastic modulus and elongation at break, the respective values are described in Table 2, and the difference between the elastic modulus in the MD direction and the elastic modulus in the TD direction was shown as the elastic modulus anisotropy, and the average value of the elastic modulus in the MD direction and the elastic modulus in the TD direction was shown as the average elastic modulus. [Test conditions] Sample size: 80 mm × 10 mm Distance between grips: 50 mm Speed: 5 mm / min Number of measurements: 3 times

[0129] ·Haze evaluation Each evaluation sample was cut into a size of 30 mm × 30 mm, and both the total light transmittance and haze of each evaluation sample were measured using a haze meter (manufactured by Nippon Denshoku Industries Co., Ltd., NDH 7000 II) in accordance with ASTM D1003. Note that the lower the haze value, the better the transparency.

[0130] ·YI value (Yellow Index) evaluation Each evaluation sample was cut into a size of 30 mm × 30 mm, and measured using a spectrophotometer (manufactured by Konica Minolta, CM-5) in accordance with ASTM E313-73. Note that the closer the YI value is to 0, the better the achromaticity.

[0131]

Table 2

[0132] From the results shown in Table 2 above, according to the present invention, it can be seen that as a film, a resin composition is provided that has good elastic modulus (particularly, the average elastic modulus in the MD direction and the TD direction is 6.0 GPa or more) while maintaining transparency.

Claims

1. A resin composition comprising a resin component and fibrous alumina filler, wherein the resin component includes at least a resin having an amide structure, and the fibrous alumina filler is dispersed in the resin composition in a state where the average fiber diameter is 1 to 30 nm and the average fiber length is 100 to 4,000 nm. The resin composition is characterized by this.

2. The resin composition according to Claim 1, wherein the fibrous alumina filler is a boehmite-type or pseudo-boehmite-type alumina filler.

3. The resin composition according to Claim 1, wherein the fibrous alumina filler is contained in an amount of 1 to 50 parts by mass with respect to 100 parts by mass of the resin having at least the amide structure.

4. The resin composition according to Claim 1, wherein the resin having at least the amide structure includes a polyamide-imide resin or a polyamide resin.

5. A film comprising the resin composition according to any one of Claims 1 to 4.

6. A film having a protective layer laminated on one surface side of the film according to Claim 5.

7. A member for a display using the film according to Claim 5.

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