Resin film

Abstract

The present invention provides a resin film in which yellowing caused by a manufacturing process is suppressed. Provided is a resin film comprising a resin composition, said resin film being characterized in that the resin composition contains: one or more resins that are selected from among polyamidimide resin, polyamide resin, polyimide resin, polyarylate resin, polyethersulfone resin, and polycarbonate resin; a phosphorus compound that has a molecular weight of not more than 350; and a filler.

Description

Resin film

[0001] The present invention relates to a resin film.

[0002] Rapid advances in display devices such as smartphones and tablets have led to demands for thinner, lighter, and more flexible devices. Such display devices are typically equipped with a cover window to protect the display surface, and organic polymer film, particularly resin film, is often used as the cover window.

[0003] In recent years, various organic polymer materials have been developed for use in films as the cover windows, with the aim of not only meeting the above-mentioned demands but also further improving various properties such as toughness, heat resistance, and solvent resistance.

[0004] For example, Patent Document 1 proposes a polyamide film having a specific structural unit. Patent Document 2 proposes a polyamideimide film having a specific structural unit. Patent Document 3 proposes a polyimide film having a specific structural unit.

[0005] JP 2019-001853 A International Publication No. 2022 / 071443 JP 2022-135876 A

[0006] Here, it is fundamentally important that the above-mentioned film is colorless and highly transparent so as not to impair the display. However, the film tends to be yellowish due to the manufacturing process (in other words, the colorlessness is easily impaired and yellowing occurs easily).

[0007] In addition, resin-based films are not limited to the films used as cover windows for display devices, but are also used in a wide range of fields and applications, such as packaging films, various optical films, etc. Even in such films, yellowing is more or less detrimental and is a problem that should be avoided as much as possible.

[0008] Therefore, an object of the present invention is to provide a resin film in which yellowing due to the manufacturing process is suppressed.

[0009] The present inventors have conducted extensive research to solve the above-mentioned problems and have found that when a film is produced using a specific resin in a system containing a filler, adding a specific phosphorus compound contributes to suppressing yellowing, which led to the present invention.

[0010] The gist and configuration of the present invention to solve the above problems is as follows.

[0011] [1] A resin film made of a resin composition, characterized in that the resin composition contains one or more resins selected from polyamideimide resins, polyamide resins, polyimide resins, polyarylate resins, polyethersulfone resins, and polycarbonate resins, a phosphorus compound having a molecular weight of 350 or less, and a filler.

[0012] [2] The resin film according to [1], wherein the filler is a fibrous filler.

[0013] [3] The resin film according to [1] or [2], wherein the content of the phosphorus compound is 0.1 mass % or more and 15 mass % or less relative to the total mass of the resin film.

[0014] [4] The resin film according to any one of [1] to [3], wherein the content of the filler is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the resin.

[0015] [5] The phosphorus compound is represented by the following general formula (1): [In general formula (1), R １ and R ２ are each independently hydrogen or an alkyl group or an aryl group which may have a substituent, and R ３ is an alkyl group or an aryl group which may have a substituent], and a phosphonic acid compound represented by the following general formula (2): [In general formula (2), R ４ ~R ６ are each independently hydrogen or an alkyl group or an aryl group which may have a substituent, provided that R ４ ~R ６wherein one or more of the orthophosphate esters are not hydrogen.

[0016] [6] In the general formula (2), R ４ ~R ６ are each independently an alkyl group.

[0017] [7] In the general formula (1), R １ and R ２ are each independently an alkyl group having 1 to 3 carbon atoms, and in the general formula (2), R ４ ~R ６ are each independently an alkyl group having 1 to 3 carbon atoms.

[0018] [8] The resin film according to any one of [2] to [7], wherein the fibrous filler is a pseudo-boehmite type fibrous alumina filler.

[0019] According to the present invention, it is possible to provide a resin film in which yellowing due to the manufacturing process is suppressed.

[0020] The present invention will be described in detail below by way of example based on embodiments thereof.

[0021] <Resin Film> A resin film according to one embodiment of the present invention (hereinafter sometimes referred to as "the resin film of the present embodiment") is a resin film made of a resin composition. The resin composition is characterized by containing one or more resins selected from polyamideimide resins, polyamide resins, polyimide resins, polyarylate resins, polyethersulfone resins, and polycarbonate resins, a phosphorus compound having a molecular weight of 350 or less, and a filler.

[0022] The reason why yellowing is suppressed in the resin film of this embodiment is presumed to be as follows.

[0023] Typically, when a resin film is produced by a solution casting method, the resin film can be formed through the following steps: (1) dispersing (dissolving) a resin and, optionally, various additives such as fillers and dispersants in a solvent to prepare a solution containing a resin composition; (2) applying the solution to a substrate to obtain a coating film; and (3) heating and drying the coating film to remove the solvent. In this process, a highly polar, high-boiling-point solvent is often used as the solvent, and even if heat drying is performed thoroughly, more or less solvent may remain in the final film. In other words, it is extremely difficult to completely remove the solvent from the film. The present inventors have concluded that this remaining solvent mainly discolors due to oxidation during heating, ultimately causing yellowing of the resin film itself. This conclusion is based on the fact that, during extensive research by the present inventors, a correlation was found between the amount of solvent remaining in a resin film and its YI (yellowness index).

[0024] After further investigation, the inventors discovered that yellowing of the resin film itself is significantly suppressed when a phosphorus compound having a molecular weight of 350 or less is used together with a solvent in a filler-containing system. Due to the unique action of the phosphorus compound, at least a portion of the solvent remaining until the end is replaced by the phosphorus compound. This replacement reduces the amount of remaining solvent relatively, and it is presumed that this significantly suppresses yellowing of the resin film itself.

[0025] Based on the above considerations and inferences, by using a specified resin and a phosphorus compound with a molecular weight of 350 or less in a system in which a filler is blended, yellowing caused by the manufacturing process can be significantly suppressed in the resin film of this embodiment.

[0026] Furthermore, the resin film of this embodiment can also have the effect of maintaining mechanical properties such as elastic modulus at the same level as a resin film produced under the same conditions except that the specified phosphorus compound is not used.

[0027] The thickness of the resin film of the present embodiment is not particularly limited and can be appropriately selected depending on the purpose, but can be, for example, 5 μm or more and 100 μm or less, and preferably 10 μm or more and 80 μm or less.

[0028] (Resin) The resin film of this embodiment (and the resin composition constituting the resin film, the same applies hereinafter) contains one or more resins selected from polyamideimide resins, polyamide resins, polyimide resins, polyarylate resins, polyethersulfone resins, and polycarbonate resins. When any of these resins is used, yellowing due to the manufacturing process can be suppressed. In particular, in the resin film of this embodiment, from the viewpoint of obtaining a resin film excellent in elastic modulus and flexibility, it is preferable that the resin is one or two selected from polyamideimide resins and polyamide resins.

[0029] [Polyamide-imide resin] Polyamide-imide resin is a resin obtained by, for example, reacting a diamine compound, a tetracarboxylic acid compound, and a dicarboxylic acid compound, which are monomer components. Specifically, polyamide-imide resin is obtained by reacting a diamine compound with a tetracarboxylic acid compound to synthesize a polymer having an imide precursor structure, then reacting the polymer with a dicarboxylic acid compound to synthesize a copolymer having an imide precursor structure and an amide structure, and then subjecting the imide precursor structure in the copolymer to a ring-closing reaction (imidization). Alternatively, a diamine compound may be reacted with a tetracarboxylic acid compound to synthesize a polymer having an imide precursor structure, and the imide precursor may be subjected to a ring-closing reaction, followed by reaction with a dicarboxylic acid compound to synthesize a copolymer having an imide structure and an amide structure (polyamide-imide resin).

[0030] That is, the polyamide-imide resin has a structure in which a residue resulting from the reaction of a diamine compound with a tetracarboxylic acid compound is bonded via an imide structure to a structural unit in which a residue resulting from the reaction of a dicarboxylic acid compound is bonded via an amide structure.

[0031] The polyamide-imide resin is preferably a residue obtained by reacting the diamine compound with the tetracarboxylic acid compound, the residue containing at least one structure selected from the group consisting of a fluorine atom, an aliphatic ring, and a structure in which aromatic rings are linked together by an alkylene group which may be substituted with a sulfonyl group or a fluorine atom.

[0032] Examples of the diamine compound used in the synthesis of polyamide-imide resins include aliphatic diamines, aromatic diamines, and mixtures thereof. Here, "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituents as part of its structure. The aromatic ring may be a single ring or a condensed ring, and examples include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferred. Furthermore, "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituents as part of its structure. The diamine compound may be used alone or in combination of two or more.

[0033] 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. The aliphatic diamines may be used alone or in combination of two or more.

[0034] Examples of aromatic diamines include aromatic diamines having one aromatic ring, such as p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diaminonaphthalene; 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4-aminophenoxy)benzene, and bis(4-aminophenoxy)benzene. Examples of aromatic diamines include aromatic diamines having two or more aromatic rings, such as 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, and 9,9-bis(4-amino-3-fluorophenyl)fluorene. These aromatic diamines may be used alone or in combination of two or more.

[0035] Among the above diamine compounds, from the viewpoint of improving the colorless transparency and elasticity of the film, it is preferable to use one or more 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. Furthermore, among the above diamine compounds, from the viewpoint of further improving the colorless transparency, it is more preferable to use a diamine having a biphenyl structure in which some or all of the hydrogen atoms on the aromatic ring are substituted with substituents selected from fluoro groups, trifluoromethyl groups, or trifluoromethoxy groups, specifically 2,2'-bis(trifluoromethyl)benzidine.

[0036] The tetracarboxylic acid compound used in the synthesis of polyamide-imide resins includes tetracarboxylic acids or tetracarboxylic acid derivatives. Examples of tetracarboxylic acid derivatives include tetracarboxylic acid anhydrides, preferably dianhydrides, and acid chlorides. Examples of tetracarboxylic acid compounds include aromatic tetracarboxylic acids and their anhydrides, preferably dianhydrides; and aliphatic tetracarboxylic acid compounds, such as aliphatic tetracarboxylic acid compounds and their anhydrides, preferably dianhydrides. These tetracarboxylic acid compounds may be used alone or in combination of two or more.

[0037] Specific examples of the aromatic tetracarboxylic acid dianhydride include non-condensed polycyclic aromatic tetracarboxylic acid dianhydrides, monocyclic aromatic tetracarboxylic acid dianhydrides, and condensed polycyclic aromatic tetracarboxylic acid dianhydrides. Examples of 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'-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, 9,9-bis(3,4-dicarboxyphenyl)fluorene dianhydride (BPAF), and 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 and 4,4'-(m-phenylenedioxy)diphthalic dianhydride. Furthermore, examples of the monocyclic aromatic tetracarboxylic dianhydrides include 1,2,4,5-benzenetetracarboxylic dianhydride, and examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

[0038] Examples of aliphatic tetracarboxylic acid dianhydrides include cyclic and acyclic aliphatic tetracarboxylic acid dianhydrides. Cycloaliphatic tetracarboxylic acid dianhydrides are tetracarboxylic acid dianhydrides having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkane tetracarboxylic acid dianhydrides such as 1,2,4,5-cyclohexane tetracarboxylic acid dianhydride (HPMDA), 1,2,3,4-cyclobutane tetracarboxylic acid dianhydride (CBDA), and 1,2,3,4-cyclopentane tetracarboxylic acid dianhydride; bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride; dicyclohexyl-3,3',4,4'-tetracarboxylic acid dianhydride (HBPDA); and positional isomers thereof. These cyclic aliphatic tetracarboxylic acid dianhydrides may 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. These acyclic aliphatic tetracarboxylic dianhydrides may be used alone or in combination of two or more. Furthermore, a cyclic aliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used in combination.

[0039] Among the above tetracarboxylic acid compounds, from the viewpoint of improving the bending resistance and optical properties of the film, it is preferable to use a combination of an aromatic tetracarboxylic acid dianhydride in which some or all of the hydrogen atoms on the aromatic ring of the aromatic tetracarboxylic acid dianhydride have been substituted with substituents selected from fluoro groups, trifluoromethyl groups, or trifluoromethoxy groups, specifically 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), and a tetracarboxylic acid dianhydride having a biphenyl structure or an alicyclic hydrocarbon structure, specifically 3,3',4,4'-biphenyltetracarboxylic acid dianhydride (sBPDA), 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride (CBDA), and dicyclohexyl-3,3',4,4'-tetracarboxylic acid dianhydride (HBPDA), and the molar ratio of (6FDA:any one of sBPDA, CBDA, and HBPDA) is preferably 1:2.

[0040] Among the above 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, it is preferable to use a combination of 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).

[0041] The dicarboxylic acid compound used in the synthesis of the polyamide-imide resin includes a dicarboxylic acid or a dicarboxylic acid derivative. Examples of the dicarboxylic acid derivative include an acid chloride or an ester of the dicarboxylic acid. The dicarboxylic acid compound may be used alone or in combination of two or more.

[0042] Specific examples of the dicarboxylic acid compound include 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, and compounds in which two cyclohexanecarboxylic acids or two benzoic acids are bonded to a single bond, -CH ２ -, -C(CH ３ ) ２ -, -C(CF ３ ) ２ -, -SO ２ alicyclic dicarboxylic acids or aromatic dicarboxylic acids such as compounds linked by a phenylene group or a phenylene group, and derivatives thereof (e.g., acid chlorides, acid anhydrides); aliphatic dicarboxylic acids such as dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms, and derivatives thereof (e.g., acid chlorides, esters). These dicarboxylic acid compounds may be used alone or in combination of two or more.

[0043] Among the above dicarboxylic acid compounds, from the viewpoint of improving the elongation at break and modulus of elasticity of the film, it is preferable to use terephthalic acid, 4,4'-oxybisbenzoic acid or a derivative thereof, in particular terephthalic acid chloride (sometimes referred to as TPC) or 4,4'-oxybis(benzoyl chloride) (sometimes referred to as DEDC).

[0044] In the synthesis of polyamide-imide resins, the molar ratio of the monomer components (diamine compound:tetracarboxylic acid compound:dicarboxylic acid compound) is preferably 7:0.5-4:3-6.5, more preferably 7:1.5-3.5:3.5-5.5, and particularly preferably 7:2.5-3.5:3.5-4.5. Based on the above-described ratios of the monomer components, the molar ratio of imide structures to amide structures in the polyamide-imide resin structure is preferably 0.5-4:3-6.5, more preferably 1.5-3.5:3.5-5.5, and particularly preferably 2.5-3.5:3.5-4.5. By achieving the above-described ratio of imide structures to amide structures, excellent flexibility and high elasticity can be achieved in a well-balanced manner.

[0045] The ring-closing reaction (imidization) of an imide precursor in the synthesis of a polyamide-imide resin can be carried out by either thermal imidization, in which an azeotropic solvent (e.g., toluene, xylene, etc.) that forms an azeotrope with water is added and heated, or chemical imidization, in which a condensing agent and a reaction accelerator are used. However, chemical imidization is preferred because it is easier to maintain colorless transparency.

[0046] Condensing agents used in chemical imidization include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride, and phosphites 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.

[0047] Examples of reaction accelerators used in 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.

[0048] An organic solvent can be used in the synthesis of polyamide-imide resin. Such organic solvents are not particularly limited as long as they are inert to the reaction, and examples thereof include N,N-dimethylacetamide (DMAc), N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, dimethyl sulfoxide, m-cresol, γ-butyrolactone, cyclopentanone, cyclohexanone, and tetrahydrofuran. These organic solvents may be used alone or in combination of two or more.

[0049] The reaction conditions for synthesizing the polyamideimide resin may be a temperature of 10 to 50° C. and a time of 1 to 27 hours. From the viewpoint of maintaining colorless transparency, it is preferable to synthesize the resin in a nitrogen atmosphere.

[0050] From the viewpoint of improving the elastic modulus and elongation at break, the weight average molecular weight (Mw) of the polyamide-imide 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. 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 measured by the method described in the Examples.

[0051] [Polyamide Resin] Polyamide resin is a resin obtained by reacting, for example, a diamine compound and a dicarboxylic acid compound, which are monomer components. That is, polyamide resin is a resin having an amide structure formed by the reaction of, for example, a diamine compound and a dicarboxylic acid compound. Furthermore, polyamide resin differs from the polyamideimide resin in that the repeating units constituting the polyamide resin do not substantially have an imide structure. Furthermore, it is preferable that the structure connecting the constituting monomer components of the polyamide resin is composed of an amide structure, and does not substantially contain any repeating structures other than an amide structure.

[0052] The diamine compound used in the synthesis of the polyamide resin is the same as the diamine compound used in the synthesis of the polyamideimide resin (including examples and preferred examples). The diamine compound may be used alone or in combination of two or more.

[0053] Among the above diamine compounds, from the viewpoint of improving the colorless transparency and elasticity of the film, it is preferable to use one or more 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. Furthermore, among the above diamine compounds, from the viewpoint of further improving the colorless transparency, it is more preferable to use a diamine having a biphenyl structure in which some or all of the hydrogen atoms on the aromatic ring are substituted with substituents selected from fluoro groups, trifluoromethyl groups, or trifluoromethoxy groups, specifically 2,2'-bis(trifluoromethyl)benzidine.

[0054] The dicarboxylic acid compound used in the synthesis of the polyamide resin is the same as the dicarboxylic acid compound used in the synthesis of the polyamideimide resin (including examples and preferred examples). The dicarboxylic acid compound may be used alone or in combination of two or more.

[0055] Among the above dicarboxylic acid compounds, from the viewpoint of improving the elongation at break and modulus of elasticity of the film, it is preferable to use terephthalic acid, 4,4'-oxybisbenzoic acid, or a derivative thereof, in particular terephthalic acid chloride (TPC) or 4,4'-oxybis(benzoyl chloride) (DEDC). It is also preferable to use TPC and DEDC in combination as the dicarboxylic acid compound.

[0056] The polyamide resin can be produced by a known method for producing polyamides, such as a solution polymerization method, an interfacial polymerization method, a melt polymerization method, a solid-state polymerization method, etc. In particular, the solution polymerization method and the interfacial polymerization method are preferably used for producing aromatic polyamide resins.

[0057] Specifically, for example, polyamide resins can be synthesized by solution polymerization from a diamine compound and a dicarboxylic acid chloride as a dicarboxylic acid compound. In this case, the reaction can be carried out in an aprotic organic polar solvent. Hydrogen chloride is produced as a by-product in this reaction, and to neutralize this, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate, as well as organic neutralizing agents such as 1,2-butylene oxide, ethylene oxide, propylene oxide, ammonia, and pyridine can be used.

[0058] Examples of the aprotic organic polar solvent 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; hexamethylphosphoramide; and γ-butyrolactone. These aprotic organic polar solvents may be used alone or in combination of two or more. Aromatic hydrocarbons such as xylene and toluene may also be used. Furthermore, to promote dissolution of the polymer, 50% by mass or less of an alkali metal or alkaline earth metal salt may be added to the solvent.

[0059] When a polyamide resin is used, it is preferable to end-cap the polyamide resin from the viewpoint of improving the colorless transparency of the film. Examples of compounds used for end-capping the polyamide resin include acetyl chloride, benzoyl chloride, substituted benzoyl chloride, acetic anhydride, 5-norbornene-2,3-dicarboxylic anhydride, 4-ethynylaniline, 4-phenylethynylphthalic anhydride, and maleic anhydride.

[0060] The reaction conditions for synthesizing the polyamide resin may be a temperature of 10 to 50° C. and a time of 10 minutes to 27 hours. From the viewpoint of maintaining colorless transparency, it is preferable to synthesize the polyamide resin under a nitrogen atmosphere.

[0061] From the viewpoint of improving mechanical properties, the polyamide resin 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.

[0062] From the viewpoint of improving mechanical properties, the polyamide resin 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.

[0063] The polyamide resin preferably has a polydispersity (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.

[0064] [Polyimide Resin] A polyimide resin is a resin obtained by, for example, reacting a diamine compound and a tetracarboxylic acid compound, which are monomer components. That is, a polyimide resin is a resin having an imide structure formed by, for example, reacting a diamine compound with a tetracarboxylic acid compound. Furthermore, a polyimide resin differs from the polyamide-imide resin in that the repeating units constituting the polyimide resin are substantially free of amide structures. Furthermore, it is preferable that the structure connecting the constituting monomer components of a polyimide resin is substantially free of repeating structures other than imide structures and is composed of an imide structure.

[0065] The diamine compound used in the synthesis of the polyimide resin is the same as the diamine compound used in the synthesis of the polyamide-imide resin (including examples and preferred examples). The diamine compound may be used alone or in combination of two or more.

[0066] The tetracarboxylic acid compound used in the synthesis of the polyimide resin is the same as the tetracarboxylic acid compound used in the synthesis of the polyamide-imide resin (including examples and preferred examples). The tetracarboxylic acid compound may be used alone or in combination of two or more.

[0067] The polyimide resin can be produced by a known method for producing polyimides, for example, by reacting the above-mentioned tetracarboxylic acid compound with the above-mentioned diamine compound to synthesize an imide precursor (polyamic acid resin), and then performing a ring-closing reaction (imidization) of the imide precursor. The conditions for the ring-closing reaction are the same as those (including examples and preferred examples) described above as the conditions for the ring-closing reaction of the imide precursor in the synthesis of a polyamide-imide resin.

[0068] From the viewpoint of improving the modulus of elasticity and elongation at break, the weight average molecular weight (Mw) of the polyimide 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.

[0069] [Polyarylate Resin] Polyarylate resin is an amorphous aromatic polyester polymer having a structure containing an aromatic dicarboxylic acid residue and a dihydric phenol residue. Such polyarylate resin can be produced, for example, using an aromatic dicarboxylic acid or its derivative and a dihydric phenol or its derivative. In addition, polyarylate resin can be produced by a method such as solution polymerization, melt polymerization, or interfacial polymerization.

[0070] As a raw material for introducing an aromatic dicarboxylic acid residue into a polyarylate resin, aromatic dicarboxylic acids and derivatives thereof can be mentioned.

[0071] Examples of aromatic dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, chlorophthalic acid, nitrophthalic acid, 2,5-naphthalenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,5-naphthalenedicarboxylic acid, methyl terephthalic acid, 4,4'-biphenyldicarboxylic acid, 2,2'-biphenyldicarboxylic acid, 4,4'-diphenyletherdicarboxylic acid, 4,4'-diphenylmethanedicarboxylic acid, 4,4'-diphenylsulfonedicarboxylic acid, 4,4'-diphenylisopropylidenedicarboxylic acid, 1,2-bis(4-carboxyphenoxy)ethane, 5-sodium sulfoisophthalic acid, and diphenic acid. Examples of derivatives of aromatic dicarboxylic acids include esters and acid chlorides of the above-mentioned aromatic dicarboxylic acids with alkyl groups having 1 to 3 carbon atoms.

[0072] Among these, terephthalic acid, isophthalic acid, and derivatives thereof are preferred as raw materials for introducing aromatic dicarboxylic acid residues. Furthermore, from the viewpoint of the balance between heat resistance and fluidity, it is more preferred to use a mixture of both terephthalic acid or a derivative thereof and isophthalic acid or a derivative thereof as raw materials for introducing aromatic dicarboxylic acid residues. In this case, the mixed molar ratio (terephthalic acid / isophthalic acid) is any ratio within the range of 100 / 0 to 0 / 100, but is preferably 90 / 10 to 10 / 90. Within this range, the resulting polyarylate resin becomes more amorphous and has better heat resistance. From the same viewpoint, the mixed molar ratio (terephthalic acid / isophthalic acid) is more preferably within the range of 70 / 30 to 30 / 70, and even more preferably 55 / 45 to 45 / 55.

[0073] Examples of raw materials for introducing dihydric phenol residues into polyarylate resins include bisphenols, such as resorcinol, 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane, 2,2-bis(4-hydroxy-3-methylphenyl)propane, 2,2-bis(4-hydroxy-3,5-dibromophenyl)propane, 2,2-bis(4-hydroxy-3,5-dichlorophenyl)propane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl ketone, 4,4'-dihydroxydiphenylmethane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, and 1,1-bis(4-hydroxyphenyl)cyclohexane.

[0074] Among these, it is preferable to use 2,2-bis(4-hydroxyphenyl)propane as a raw material for introducing a dihydric phenol residue, and it is more preferable to use only this.

[0075] Examples of commercially available polyarylate resins that can be used include Vectran (registered trademark) manufactured by Kuraray Co., Ltd., U-Polymer (registered trademark) manufactured by Unitika Ltd., and Unifiner (registered trademark) manufactured by Unitika Ltd.

[0076] [Polyethersulfone Resin] Polyethersulfone resin is a resin having an aromatic group in the main chain and having an oxy group and a sulfonyl group as a linking group of the aromatic group. Polyethersulfone resin is usually produced by polycondensing a dihalodiphenyl compound and a dihydric phenol compound in the presence of an alkali metal compound in an organic solvent, or by polycondensing an alkali metal disalt of a dihydric phenol and a dihalodiphenyl compound. Polyethersulfone resin is typically a compound represented by the following formula (X1): [In the above formula (X1), Ar is a group represented by the following formula (X2): In the formula (X2), Y represents a divalent group having an aromatic ring selected from the group consisting of a single bond, a sulfonyl group (—SO２ -), 2,2-propylidene group (-C(CH ３ ) ２ In the structural unit of formula (X1), some of the hydrogen atoms bonded to the aromatic ring may be substituted with a halogen atom, a lower alkyl group having about 1 to 3 carbon atoms, a lower alkoxy group having about 1 to 3 carbon atoms, or a phenyl group.

[0077] The organic solvent used in producing the polyethersulfone resin is preferably a polar solvent. Examples of such organic solvents include sulfoxide solvents such as dimethyl sulfoxide; amide solvents such as N,N-dimethylformamide and N,N-dimethylacetamide; pyrrolidone solvents such as N-methyl-2-pyrrolidone and N-vinyl-2-pyrrolidone; piperidone solvents such as N-methyl-2-piperidone; imidazolidinone solvents such as 1,3-dimethyl-2-imidazolidinone; and hexamethylphosphoamide, γ-butyrolactone, sulfolane, diphenyl ether, dimethyl sulfoxide, and diphenyl sulfone. Such organic solvents may be used alone or in combination of two or more solvents.

[0078] Examples of the alkali metal compound used in producing the polyethersulfone resin include alkali metal carbonates, alkali metal hydroxides, alkali metal hydrides, alkali metal alkoxides, etc. Among these, anhydrous alkali metal carbonates such as potassium carbonate and sodium carbonate are preferred as the alkali metal compound.

[0079] Examples of the dihalodiphenyl compound include dihalodiphenyl compounds having a sulfonyl group. More specifically, examples include dihalodiphenyl sulfones such as 4,4'-dichlorodiphenyl sulfone and 4,4'-difluorodiphenyl sulfone; bis(halogenophenylsulfonyl)benzenes such as 1,4-bis(4-chlorophenylsulfonyl)benzene and 1,4-bis(4-fluorophenylsulfonyl)benzene; and bis(halogenophenylsulfonyl)biphenyls such as 4,4'-bis(4-chlorophenylsulfonyl)biphenyl and 4,4'-bis(4-fluorophenylsulfonyl)biphenyl. These dihalodiphenyl compounds may be used alone or in combination of two or more. Among these, from the viewpoint of easy availability, 4,4'-dichlorodiphenyl sulfone or 4,4'-difluorodiphenyl sulfone is more preferred as the dihalodiphenyl compound, with 4,4'-dichlorodiphenyl sulfone being particularly preferred.

[0080] Examples of the dihydric phenol compound include hydroquinone, catechol, resorcinol, and 4,4'-biphenol. Examples of the dihydric phenol compound include bis(4-hydroxyphenyl)alkanes such as 2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)methane, and 2,2-bis(4-hydroxyphenyl)ethane; dihydroxydiphenyl sulfones such as 4,4'-dihydroxydiphenyl sulfone; dihydroxydiphenyl ethers such as 4,4'-dihydroxydiphenyl ether; and compounds in which some of the hydrogen atoms bonded to the benzene ring of these compounds have been substituted with lower alkyl groups such as methyl, ethyl, and propyl groups, lower alkoxy groups such as methoxy, ethoxy, and propyloxy groups, or halogen atoms such as chlorine, bromine, and fluorine atoms. These dihydric phenol compounds may be used alone or in combination of two or more. Among these, the dihydric phenol compound is preferably hydroquinone, 4,4'-biphenol, 2,2-bis(4-hydroxyphenylpropane), 4,4'-dihydroxydiphenyl ether, or 4,4'-dihydroxydiphenyl sulfone from the viewpoints of price and availability, and is preferably a compound represented by the group of the following formula (X3): [In the above formula (X3), Y is the same as defined above.] Bisphenols selected from the above are more preferred, and 4,4'-dihydroxydiphenyl sulfone is particularly preferred.

[0081] Examples of commercially available polyethersulfone resins include the Sumikaexcel PES series manufactured by Sumitomo Chemical Co., Ltd., the PES series manufactured by Mitsui Chemicals, Inc., the Ultrason E series manufactured by BASF Japan Ltd., and the Radel A series manufactured by Solvay Advanced Polymers K.K.

[0082] [Polycarbonate Resin] A polycarbonate resin is a resin having a carbonate ester structure (—O—(C═O)—O—) in its molecular structure. Examples of such polycarbonate resins include reaction products of polyhydric phenol compounds with phosgene or carbonate ester compounds.

[0083] Examples of the polyhydric phenol compound include hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane, 1,1-bis(4-hydroxyphenyl)-1-phenylethane, bisphenol A, bisphenol C, bisphenol E, bisphenol F, bisphenol M, bisphenol P, bisphenol S, bisphenol Z, 2,2-bis(3-methyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxyphenyl)cyclohexane, 2,2-bis(3-phenyl-4 4,4'-dihydroxydiphenyl)propane, 2,2-bis(3-isopropyl-4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dibromo-4-hydroxyphenyl)propane, 4,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 3,3'-dimethyl-4,4'-dihydroxydiphenyl sulfide, 4,4'-dihydroxydiphenyl oxide, etc. Among these, hydroquinone, resorcinol, 4,4'-dihydroxydiphenyl, and bisphenol A are preferred as the polyhydric phenol compound.

[0084] Examples of the carbonate ester compound include diphenyl carbonate, bis(chlorophenyl) carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate, dimethyl carbonate, diethyl carbonate, dibutyl carbonate, etc. Among these, bis(diphenyl) carbonate, dimethyl carbonate, and diethyl carbonate are preferred as the carbonate ester compound.

[0085] Commercially available polycarbonate resins include Panlite L-1250WP and Panlite SP-1516 manufactured by Teijin Limited; Iupizeta EP-5000, Iupizeta EP-4000, Iupizeta PCZ-200, Iupizeta PCZ-400, Iupizeta PCZ-500, Iupizeta PCZ-800, Iupizeta FPC-2136, Iupizeta FPC-0330, and Iupizeta FPC-0220 ("Iupizeta" is a registered trademark) manufactured by Mitsubishi Gas Chemical Company, Inc.; Caliber 301-30 manufactured by Sumika Polycarbonate Co., Ltd.; and QPAC25, QPAC40, and QPAC100 manufactured by EMPOWER MATERIALS.

[0086] (Phosphorus Compound) The resin film of this embodiment contains a phosphorus compound having a molecular weight of 350 or less. In a system incorporating a filler, if the molecular weight of the phosphorus compound used exceeds 350, there is a risk that the effect of replacing part or all of the solvent and thus the effect of suppressing yellowing may not be obtained, and even more, the yellowness may become stronger. Furthermore, the molecular weight of the phosphorus compound used in the resin film of this embodiment is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less. In this case, the volatility of the phosphorus compound is increased, thereby suppressing the deterioration of various properties such as mechanical properties and thermal properties that may occur when a large amount of phosphorus compound remains in the resin film after heat drying. The phosphorus compounds may be used alone or in combination of two or more.

[0087] The phosphorus compound is represented by the following general formula (1): [In general formula (1), R １ and R ２ are each independently hydrogen or an alkyl group or an aryl group which may have a substituent, and R ３ is an alkyl group or an aryl group which may have a substituent], and a phosphonic acid compound represented by the following general formula (2): [In general formula (2), R ４ ~R ６ are each independently hydrogen or an alkyl group or an aryl group which may have a substituent, provided that R４ ~R ６ wherein one or more of the groups are not hydrogen. In this case, a higher desired effect can be obtained.

[0088] In the above general formula (1), R １ and R ２ From the viewpoint of obtaining a higher desired effect, it is more preferable that each of R is independently an alkyl group having 1 to 3 carbon atoms, and it is even more preferable that each of R is a methyl group. ３ From the viewpoint of obtaining a higher desired effect, is preferably an aryl group, and more preferably a phenyl group.

[0089] In the above general formula (2), R ４ ~R ６ Preferably, none of R ４ ~R ６ From the viewpoint of obtaining a more desirable effect, R are each independently preferably an alkyl group, more preferably an alkyl group having 1 to 4 carbon atoms, even more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably an alkyl group having 1 or 2 carbon atoms. ４ ~R ６ are also preferably all the same.

[0090] In the resin film of this embodiment, the content of the phosphorus compound (the total content when two or more types are used) is preferably 0.1% by mass or more and 15% by mass or less relative to the total mass of the resin film. When the phosphorus compound is in the above range relative to the total mass of the resin film, the effect of replacing at least a portion of the solvent and thus the effect of suppressing yellowing can be significantly obtained, and the various properties required of the film can be maintained. From the same viewpoint, the content of the phosphorus compound relative to the total mass of the resin film is more preferably 0.3% by mass or more, even more preferably 0.5% by mass or more, even more preferably 0.6% by mass or more, even more preferably 0.8% by mass or more, more preferably 12% by mass or less, even more preferably 10% by mass or less, and even more preferably 8% by mass or less. Note that the phosphorus compound may also volatilize during the production of the resin film, particularly during drying. Therefore, when specifying the amount of the phosphorus compound in this embodiment, it is important to focus on the content of the phosphorus compound in the produced resin film rather than the compounding ratio during production. The content of the phosphorus compound relative to the total mass of the resin film can be measured by thermogravimetric analysis (TGA), specifically, by the procedure described in the Examples.

[0091] (Filler) The resin film of this embodiment contains a filler. The shape of the filler is not particularly limited, and examples include fibrous, spherical, plate-like, cylindrical, prismatic, scale-like, and irregular shapes. Among these, the shape of the filler is preferably fibrous. That is, the filler is preferably a fibrous filler. In this case, it is believed that the fibrous fillers are mutually arranged in a lattice pattern in the resin composition, thereby suppressing coloration, turbidity, and a decrease in flexibility while providing a high elasticity effect. Furthermore, compared to spherical or irregular fillers, fibrous fillers can provide excellent anti-blocking effects without impairing light transmittance. Specifically, when resin films of this embodiment are stacked or rolled up for storage, the fibrous filler can suppress adhesion (blocking) between the resin films, improving storage stability and workability. Note that "fibrous" refers to a shape having an aspect ratio (filler length / filler diameter) of 5 or more.

[0092] Furthermore, the fibrous filler preferably has an average fiber diameter of 1 to 30 nm and an average fiber length of 100 to 4,000 nm. When such fibrous fillers are dispersed, the respective fibrous fillers are mutually arranged in a lattice pattern in the resin composition, thereby further enhancing the effects of suppressing coloration, turbidity, and reduction in flexibility, as well as the effect of increasing elasticity. From the same viewpoint, the average fiber diameter of the fibrous filler is more preferably 2 nm or more, even more preferably 3 nm or more, and more preferably 25 nm or less, even more preferably 20 nm or less. From the same viewpoint, the average fiber length of the fibrous filler is more preferably 300 nm or more, even more preferably 500 nm or more, and more preferably 3,000 nm or less, even more preferably 2,000 nm or less.

[0093] The "average fiber diameter" and "average fiber length" are measured by dissolving a resin film in a good solvent for the resin constituting the resin film (e.g., methyl isobutyl ketone (MIBK) or dimethylacetamide (DMAc)), diluting the solution 10,000 times, dropping one drop onto a cover glass (Cover Glass Trophy, manufactured by Matsunami Glass Co., Ltd.), drying at 50°C, and then observing the resultant solution under an electron microscope (e.g., a 10,000x magnification image obtained using an FE-SEM manufactured by Hitachi High-Technologies). The fibrous filler to be measured may be in the form of either a single fiber or a fiber bundle formed by aggregating multiple single fibers, as long as it can be visually recognized as a single fiber in the electron microscope image. The "average fiber diameter" is the average measured value of the diameters in the short side direction of 50 arbitrarily selected fibrous fillers in the electron microscope image, and the "average fiber length" is the average measured value of the length in the long side direction.

[0094] The fibrous filler is blended in the predetermined resin in the form of a powder or a dispersion (sol), stirred, and kneaded as necessary, to adjust the dispersion state in the resin composition, i.e., the "average fiber diameter" and "average fiber length." 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, and adjustments can be made by varying 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 spacing.

[0095] The fibrous filler can be surface-treated or used as a dispersion (sol) dispersed in an organic solvent or the like. In this case, the dispersion state in the resin composition can be stabilized. In particular, if the dispersion state of the fibrous filler in the dispersion (sol) is adjusted to be the same as the dispersion state of the fibrous filler in the resin composition, i.e., the "average fiber diameter" and "average fiber length," the solution (dispersion), and ultimately the resin film, can be produced with good productivity.

[0096] The method for surface treatment of the fibrous filler is not particularly limited, and examples thereof include surface treatment methods using coupling agents such as silane-based, titanate-based, aluminate-based, and zircoaluminate-based coupling agents. Furthermore, the method for preparing a dispersion of the fibrous filler is not particularly limited, and examples thereof include the method for preparing a dispersion treated with an organic sulfonic acid disclosed in JP 2008-31010 A.

[0097] The material of the fibrous filler is not particularly limited, but examples thereof include silica, titanium oxide, alumina (including alumina hydrate), silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc. Examples of the alumina hydrate include boehmite and pseudo-boehmite. These may be used alone or in combination of two or more. Among these, the material of the fibrous filler is preferably alumina (including alumina hydrate), more preferably boehmite or pseudo-boehmite, and even more preferably pseudo-boehmite. That is, the fibrous filler is preferably a fibrous alumina filler, more preferably a boehmite or pseudo-boehmite fibrous alumina filler, and even more preferably a pseudo-boehmite fibrous alumina filler. In this case, the mechanical properties and optical properties of the resin film can be further improved.

[0098] In the resin film of this embodiment, the content of the filler is preferably 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the resin. If the content of the filler is within the above range, the film can be made highly elastic while maintaining the various properties required for the film. From the same viewpoint, the content of the filler is more preferably 5 parts by mass or more and more preferably 30 parts by mass or less per 100 parts by mass of the resin.

[0099] (Other Components) In addition to the above-described resins, phosphorus compounds, and fillers, the resin film of this embodiment may contain other components within the scope of the present invention. Examples of such other components include resins other than the above-described resins, solvents that may remain in the resin film due to the production process, leveling agents for improving coatability when producing the film, dispersants, surfactants, retardation adjusters, antioxidants, ultraviolet inhibitors, light stabilizers, plasticizers, waxes, pigments, dyes, foaming agents, antifoaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, bluing agents for reducing the yellowness of the film, pH adjusters, crosslinking agents, and lubricants.

[0100] [Other Resins] Examples of other resins other than the above-described resins include polyester resins such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyphenylene sulfide resin, polyether ether ketone resin, polyetherimide resin, epoxy resin, phenolic resin, glass-epoxy resin, polyphenylene ether resin, acrylic resin, polyolefin resins such as polyethylene and polypropylene, and polycycloolefins such as polynorbornene.

[0101] [Solvent] The solvent that may remain in the resin film due to the production process is not particularly limited, and examples thereof include known solvents, particularly organic solvents. Specific examples thereof include ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and dimethyl carbonate; lactone solvents such as γ-butyrolactone (GBL), δ-valerolactone, ε-caprolactone, γ-crotonolactone, γ-hexanolactone, α-methyl-γ-butyrolactone, γ-valerolactone, α-acetyl-γ-butyrolactone, and δ-hexanolactone; and tetrahydrofuran, dioxane, dibutyl ether, and diethylene glycol dimethyl ether (diglyme). Examples of the solvent include solvents having an ether group, ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone, phenol solvents such as m-cresol, solvents having a sulfone group such as methanesulfonic acid, dimethyl sulfone, ethyl phenyl sulfone, diethyl sulfone, diphenyl sulfone, sulfolane, bisphenol S, sorapsone, dapsone, bisphenol A polysulfone, and sulfolane, sulfoxide solvents such as dimethyl sulfoxide (DMSO), and amide solvents such as N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), and dimethylacetamide (DMAc). The above solvents may be used alone or in combination of two or more. Among these, the solvent is preferably one or more selected from ester solvents, solvents having an ether group, and amide solvents, and more preferably one or more selected from dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), and diethylene glycol dimethyl ether (diglyme). However, the solvent does not necessarily have to remain in the resin film of the present embodiment.

[0102] [Dispersant] When producing the resin film of this embodiment, a dispersant may be further used from the viewpoint of modifying the filler and stabilizing the solution viscosity of the resin composition. That is, the resin film of this embodiment may further contain a dispersant. Examples of the dispersant include organic carboxylic acid compounds such as acetic acid, benzoic acid, terephthalic acid, citric acid, succinic acid, and lactic acid; organic phosphoric acid compounds and organic phosphonic acid compounds (other than the specific phosphorus compounds used in this embodiment); organic sulfonic acid compounds such as benzenesulfonic acid, p-toluenesulfonic acid, and dodecylbenzenesulfonic acid; and organic bases such as pyridine, tetraethylamine, diisopropylethylamine, 2,6-dimethylpyridine, isoquinoline, and triethylenediamine.

[0103] When the resin film further contains a dispersant, the content of the dispersant relative to 100 parts by mass of the filler can be, for example, 1 part by mass or more and 50 parts by mass or less.

[0104] (Production of Resin Film) The method for producing the resin film of this embodiment is not particularly limited. For example, the resin film of this embodiment can be produced by the following steps: (1) dispersing the above-mentioned predetermined resin, the phosphorus compound having a molecular weight of 350 or less, a filler, and any other components (described above) in a solvent at predetermined ratios to prepare a solution (dispersion), (2) applying the solution (dispersion) to a substrate to obtain a coating film, (3) drying the coating film, and (4) peeling the dried coating film from the substrate to obtain a film.

[0105] When a solvent is used in the synthesis of the resin, the solvent may be used as it is.

[0106] When preparing the solution (dispersion), it is preferable to adjust the amount of the phosphorus compound relative to the resin so that the content of the phosphorus compound relative to the total mass of the resin film falls within the above-mentioned preferred range. Specifically, taking into consideration that not only the solvent but also the phosphorus compound may volatilize, a suitable resin film can be obtained by setting the amount of the phosphorus compound to 2 to 25 parts by mass relative to 100 parts by mass of the resin. The amount of the phosphorus compound relative to 100 parts by mass of the resin is more preferably 5 parts by mass or more, even more preferably 10 parts by mass or more, and more preferably 20 parts by mass or less.

[0107] As a means for applying the solution (dispersion) onto the substrate, a conventionally known means can be applied, such as a dip coating method, a flow coating method, a roll coating method, a bar coater method, a blade coater method, a screen printing method, a curtain coating method, and a spray coating method.

[0108] The conditions for drying the coating film are not particularly limited and can be adjusted based on the boiling point of the solvent used, but for example, it is preferable to perform primary drying at 90 to 150°C for 1 to 60 minutes and secondary drying at 180 to 250°C for 1 to 60 minutes. Tertiary drying may be performed after the secondary drying. Note that since the volatilization behavior differs depending on the selected phosphorus compound and solvent, it is preferable to appropriately adjust the drying conditions in order to obtain a suitable resin film.

[0109] The resin film of the present embodiment can be used in a wide range of applications, such as packaging films and various optical films, but because of its excellent colorlessness, it can be particularly preferably used as a display member, for example, an organic EL display, a flexible substrate, a flexible panel, a liquid crystal display device, a touch panel, a cover window, a surface protection film, etc.

[0110] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples and can be modified as appropriate within the scope of the present invention.

[0111] The phosphorus compounds used in each example are as follows: Phosphorus compound 1: "ADK STAB FP-900L" manufactured by ADEKA Corporation, molecular weight of main component: 650.55 Phosphorus compound 2: "ADK STAB PFR" manufactured by ADEKA Corporation, molecular weight of main component: 574.5 Phosphorus compound 3: "ADK STAB FP-600" manufactured by ADEKA Corporation, molecular weight of main component: 692.64 Phosphorus compound 4: triphenyl phosphate (TPhP) (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight: 326 Phosphorus compound 5: dimethyl phenylphosphonate (PPADM) (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight: 186 Phosphorus compound 6: trimethyl phosphate (TMP) (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight: 140 Phosphorus compound 7: triethyl phosphate (TEP) (manufactured by Tokyo Chemical Industry Co., Ltd.), molecular weight: 182

[0112] <Synthesis of Polyamide-imide Resin (PAI)> A 100 mL reactor was charged with 60.0 g of N,N-dimethylacetamide (DMAc), and 4.849 g (15.14 mmol) of 2,2'-bis(trifluoromethyl)benzidine (TFMB) was added. 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 the mixture was stirred at 30°C for 2 hours to react, yielding 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 the solution, and the mixture was stirred for 1.5 hours while maintaining the liquid temperature at 30°C to react, yielding a solution containing a copolymer having an imide precursor structure and an amide structure. Subsequently, 2.09 g of pyridine, 2.45 g of acetic anhydride, and 8.53 g of DMAc were added and stirred at 20-30°C for 8 hours to obtain a polyamideimide solution. Further, 99 g of DMAc was added and stirred until homogeneous. The solution was then gradually poured into a container containing 4 L of methanol to cause precipitation. The precipitated solid was then filtered and pulverized, and then dried in a vacuum at 80°C for 18 hours to obtain 8.0 g of polyamideimide copolymer (PAI) as a solid powder. The resulting PAI had a weight average molecular weight of 221,000 in terms of polystyrene measured by GPC.

[0113] <Synthesis of Polyamide Resin (PA)> A 100 mL reactor was charged 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'-oxybis(benzoyl chloride) (DEDC) and 2.67 g (13.17 mmol) of terephthalic acid chloride (TPC) were added to the TFMB solution, and the mixture was stirred at 30°C for 2 hours to react. Thereafter, 0.026 g (0.33 mmol) of acetyl chloride was added to the solution, and the mixture was stirred at 30°C for 30 minutes to react, yielding a solution containing a polymer (PA) having an amide structure. The resulting PA had a weight average molecular weight of 184,000 as calculated on a polystyrene basis by GPC.

[0114] <Film Production> Resin (polyamideimide resin or polyamide resin) powder, a phosphorus compound, and a dispersant (p-toluenesulfonic acid monohydrate) were dissolved in a solvent (dimethylacetamide, DMAc) according to the formulation shown in Table 1. A filler (pseudoboehmite-type fibrous alumina filler, manufactured by Kawaken Fine Chemicals, average fiber diameter: 5 nm, average fiber length: 800 nm) was then added. The solids concentration was adjusted to 13% by mass, and the resulting solution was dispersed and homogenized to prepare a film production solution. This solution was then applied to a glass substrate using a table coater ("AFA-standard" manufactured by Coatec Co., Ltd.) to a thickness of approximately 50 μm after drying. The solution was then dried in an oven ("Fine Oven DH612" manufactured by Yamato Scientific Co., Ltd.) to form a film made of the resin composition. The drying conditions were a two-stage drying process: 120°C for 40 minutes, followed by 220°C for 30 minutes.

[0115] The following measurements were carried out on the obtained film, and the results are shown in Table 1.

[0116] (1) Measurement of the content of phosphorus compound relative to the total mass of the film (thermogravimetric analysis) 3 to 5 mg of each film was weighed into an aluminum cup and subjected to thermogravimetric analysis using a TA Instruments "TA 5500" at a measurement temperature of 30°C to 400°C and a heating rate of 10°C / min to obtain a TG curve. Next, a peak separation operation was performed on the differential curve of the obtained TG curve, and the peaks of each component (phosphorus compound) were integrated to determine the weight loss of each component (content in the film). In the peak separation operation, fitting was performed using a Gaussian function.

[0117] (2) Measurement of tensile modulus Tests were carried out on each film using an EZ-SX made by Shimadzu Corporation under the following conditions. The tensile modulus was determined from the slope of the obtained stress-strain curve when the stress was between 5 MPa and 10 MPa. [Test conditions] Sample size: 80 mm x 10 mm Distance between grippers: 50 mm Speed: 5 mm / min Number of measurements: 3

[0118] (3) Evaluation of YI Value (Yellow Index) Each film was cut into a size of 30 mm x 30 mm, and the YI value of each film was measured using a spectrophotometer (CM-5, manufactured by Konica Minolta, Inc.) in accordance with ASTM E313-73. Furthermore, the amount of change in the YI value of each example relative to the YI value of a reference example (a comparative example using the same resin but no phosphorus compound) was calculated. A negative value for the amount of change in the YI value indicates that yellowing was suppressed.

[0119]

[0120] Table 1 shows that in a system incorporating a filler, when a film is produced by dispersing a resin in a solvent, yellowing of the film can be significantly suppressed by incorporating a phosphorus compound having a molecular weight of 350 or less. On the other hand, Comparative Example 2-4 in Table 1 shows that even if a phosphorus compound is incorporated, if the molecular weight of the phosphorus compound exceeds 350, the yellowness of the film is actually intensified.

[0121] According to the present invention, it is possible to provide a resin film in which yellowing due to the manufacturing process is suppressed.

Claims

1. A resin film made of a resin composition, characterized in that the resin composition contains one or more resins selected from polyamideimide resins, polyamide resins, polyimide resins, polyarylate resins, polyethersulfone resins, and polycarbonate resins, a phosphorus compound having a molecular weight of 350 or less, and a filler.

2. The resin film according to claim 1, wherein the filler is a fibrous filler.

3. A resin film according to claim 1 or 2, wherein the content of the phosphorus compound is 0.1 mass % or more and 15 mass % or less relative to the total mass of the resin film.

4. A resin film according to claim 1 or 2, wherein the content of the filler is 1 part by mass or more and 40 parts by mass or less per 100 parts by mass of the resin.

5. The phosphorus compound is represented by the following general formula (1): [In general formula (1), R １ and R ２ are each independently a hydrogen atom, an alkyl group which may have a substituent, or an aryl group, and R ３ is an alkyl group or an aryl group which may have a substituent], and a phosphonic acid compound represented by the following general formula (2): [In general formula (2), R ４ ~R ６ are each independently a hydrogen atom, an alkyl group which may have a substituent, or an aryl group, provided that R ４ ~R ６ wherein one or more of the orthophosphate esters are not hydrogen.

6. In the general formula (2), R ４ ~R ６ The resin film according to claim 5 , wherein each of the groups independently represents an alkyl group.

7. In the general formula (1), R １ and R ２ are each independently an alkyl group having 1 to 3 carbon atoms; ４ ~R ６ The resin film according to claim 6, wherein each of the groups independently represents an alkyl group having 1 to 3 carbon atoms.

8. The resin film according to claim 2, wherein the fibrous filler is a pseudoboehmite type fibrous alumina filler.

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