Resin films and flexible displays

Abstract

The present invention provides a resin film that uses monomers that do not fall under the category of PFAS and maintains good colorlessness even when the film thickness is increased. [Solution] A resin film having a thickness of 30 μm or more, wherein the resin composition comprises one or more resins selected from aromatic polyimide resins, aromatic polyamideimide resins, and aromatic polyamide resins, and the resin has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring, and the yellow index value is 10.0 or less.

Description

[Technical Field]

[0001] This invention relates to resin films and flexible displays. [Background technology]

[0002] Display device components such as liquid crystal displays and organic light-emitting diodes (OLEDs) are widely used in various applications such as mobile phones and tablets. Traditionally, glass, typified by UTG (Ultra-Thin Glass), has been used as the front panel material for such display devices. However, while glass is colorless, highly transparent, and can exhibit high hardness depending on the type, it is also very rigid and brittle. Therefore, it is difficult to use this type of glass as the front panel material for flexible displays that are bent or folded.

[0003] Therefore, resin films utilizing polymer materials are being considered as an alternative to glass. Films containing polymer materials readily exhibit flexible properties and are expected to be used in various applications such as flexible displays. For example, Patent Document 1 proposes a polyamide film having specific structural units. [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2019-001853 [Overview of the project] [Problems that the invention aims to solve]

[0005] When using film as the front panel material for flexible displays, it is necessary to provide protection against external forces. Therefore, adjusting the film thickness is sometimes required to control impact resistance and hardness. However, increasing the film thickness of resin films tends to result in a yellowish tint and loss of colorlessness. Therefore, there is a need for resin films that maintain good colorlessness even at high film thicknesses.

[0006] Incidentally, 2,2'-bis(trifluoromethyl)benzidine (TFMB), used as a diamine monomer in Patent Document 1, has a trifluoromethyl group in its molecule and is a compound that falls under the category of so-called PFAS (Per- and polyfluoroalkyl substances). Compounds that fall under the category of PFAS are restricted or may be restricted in use by laws and regulations both domestically and internationally due to concerns about their impact on the environment or human health.

[0007] Therefore, there is a need for a resin film that maintains good colorlessness even with a large film thickness, while avoiding the use of compounds that fall under the category of PFAS, including TFMB.

[0008] Therefore, the present invention aims to solve the above problems and provide a resin film that uses monomers that do not fall under the category of PFAS and has good colorlessness even when the film thickness is increased. Furthermore, a further objective of the present invention is to provide a flexible display using such a film. Here, a large film thickness refers to a film thickness of 30 μm or more. [Means for solving the problem]

[0009] The inventors of the present invention have discovered that resin films using monomers that do not fall under the category of PFAS, which have a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring, can maintain good colorlessness even when the film thickness is increased, and have completed the present invention. The gist of the present invention, which solves the above problems, is as follows.

[0010] [1] A resin film made of a resin composition and having a film thickness of 30 μm or more, wherein the resin composition contains one or more resins selected from an aromatic polyimide resin, an aromatic polyamideimide resin, and an aromatic polyamide resin, and the resin has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring, and has a yellow index value of 10.0 or less. Resin film.

[0011] [2] The resin film according to [1], wherein the resin does not have a perfluoroalkyl moiety and a polyfluoroalkyl moiety.

[0012] [3] The resin film according to [1] or [2], wherein a nitrogen atom derived from an amino group is bonded to the benzene ring to which the carbon atom having the hydrogen atom is directly bonded.

[0013] [4] The resin film according to [3], wherein the resin has a residue derived from an aromatic diamine compound represented by the following formula (1).

Chemical formula

[0014] [5] The resin film according to any one of [1] to [4], wherein the resin composition further comprises an antioxidant.

[0015] [6] The resin film according to any one of [1] to [5], wherein the resin composition further comprises one or more selected from phosphate ester compounds and phosphonic acid compounds.

[0016] [7] The resin film according to any one of [1] to [6], wherein the resin composition further comprises a filler.

[0017] [8] A flexible display comprising a resin film as described in any one of [1] to [7]. [Effects of the Invention]

[0018] According to the present invention, it is possible to provide a resin film with good colorlessness even when using monomers that do not fall under the category of PFAS and when the film thickness is increased. Furthermore, according to the present invention, a flexible display using such a film can be provided. [Modes for carrying out the invention]

[0019] The resin film and flexible display of the present invention will be described in detail below based on their embodiments.

[0020] <Resin film> The resin film of this embodiment is A resin film having a thickness of 30 μm or more, comprising a resin composition, The resin composition comprises one or more resins selected from aromatic polyimide resins, aromatic polyamideimide resins, and aromatic polyamide resins, wherein the resin has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring. It is characterized by having a yellow index value of 10.0 or less.

[0021] The resin film of this embodiment has a film thickness of 30 μm or more. Generally, the greater the film thickness, the more likely it is to yellow. However, the resin film of this embodiment contains one or more resins selected from aromatic polyamide-imide resins, aromatic polyamide resins, and aromatic polyimide resins, which have an alkyl group having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring (hereinafter also referred to as "specific resin"), which easily suppresses yellow discoloration and exhibits colorlessness suitable for flexible display films with a yellow index value (YI value) of 10.0 or less.

[0022] Here, in a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring, the carbon atom containing the hydrogen atom is referred to as the "specified carbon atom." A given carbon atom may have at least one hydrogen atom, but may also have multiple hydrogen atoms. In other words, a given carbon atom may be bonded to at least one hydrogen atom, but may also be bonded to multiple hydrogen atoms.

[0023] The specified carbon atoms may be present in the side chains of the resin or incorporated into the main chain.

[0024] Resins having a structure in which carbon atoms containing hydrogen atoms are directly bonded to a benzene ring are presumed to be prone to yellowing and have a high YI value because this structure is easily oxidized. However, the specific resin used in the film of the present invention, even with a structure in which carbon atoms containing hydrogen atoms are directly bonded to a benzene ring, can secure a good YI value and produce a colorless film suitable for flexible displays.

[0025] Specifically, the particular resin in the present invention, when combined with a predetermined antioxidant, can effectively suppress the oxidation of a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring, thereby preventing the resin film from turning yellow.

[0026] Furthermore, the specific resin in the present invention, when combined with a specific drying process in the production of a resin film (such as performing secondary drying under a nitrogen atmosphere or vacuum, or performing primary drying only), can effectively suppress the oxidation of structures in which carbon atoms having hydrogen atoms are directly bonded to a benzene ring, thereby preventing the resin film from turning yellow.

[0027] Furthermore, by introducing bulky substituents around the structure in which a hydrogen-containing carbon atom is directly bonded to a benzene ring in a particular resin, it is possible to effectively suppress the yellowing of the resin film. For example, it is presumed that yellowing can be suppressed by having a fluorene skeleton around the structure in which a hydrogen-containing carbon atom is directly bonded to a benzene ring, such as 9,9-bis(4-amino-3-methylphenyl)fluorene, which has bulky substituents that inhibit the formation of charge transfer complexes and by the large free volume which makes it difficult for solvent to remain.

[0028] Furthermore, certain resins maintain their film-forming ability even when combined with other units, as their structure involves a carbon atom containing a hydrogen atom directly bonded to a benzene ring. This makes it easy to suppress yellow discoloration.

[0029] The upper limit of the thickness of the resin film is not particularly limited, and can be, for example, 100 μm or less, preferably 85 μm or less.

[0030] (resin) The resin composition of this embodiment comprises one or more resins selected from aromatic polyamide-imide resins, aromatic polyamide resins, and aromatic polyimide resins, the resin having a structure in which a predetermined carbon atom is directly bonded to a benzene ring.

[0031] The predetermined carbon atom may be present in the side chain of the resin or incorporated into the main chain. An example of a case where the predetermined carbon atom is present in the side chain of the resin is a case where the resin has an alkyl group in its side chain which may have substituents, and the alkyl group is directly bonded to a benzene ring (provided that the carbon atom of the alkyl group directly bonded to the benzene ring has at least one hydrogen atom). Here, the alkyl group in the alkyl group which may have substituents may be linear or branched, and examples include alkyl groups having 1 to 5 carbon atoms, preferably alkyl groups having 1 to 3 carbon atoms, such as a methyl group, an ethyl group, an n-propyl group, and an isopropyl group. Furthermore, examples of substituents on alkyl groups include alkenyl groups (for example, alkenyl groups with 2 to 6 carbon atoms) and aryl groups (for example, aryl groups with 6 to 10 carbon atoms).

[0032] The predetermined carbon atoms (carbon atoms having hydrogen atoms) in the side chain of the resin are preferably carbon atoms having a hydrogen atom at the benzyl position in an alkyl group directly bonded to a benzene ring.

[0033] Examples of cases in which a resin has a structure in which a predetermined number of carbon atoms are incorporated into the main chain of the resin include cases in which the resin has an alkylene group in its main chain that may have substituents, and the alkylene group is directly bonded to a benzene ring (provided that the carbon atoms of the alkyl group directly bonded to the benzene ring have at least one hydrogen atom). Here, the alkylene group may be linear or branched, and examples include alkylene groups having 1 to 5 carbon atoms, preferably alkylene groups having 1 to 3 carbon atoms, such as methylene groups, ethylene groups, n-propylene groups, and isopropylene groups. Examples of substituents include alkenyl groups (e.g., alkenyl groups with 2 to 6 carbon atoms) and aryl groups (e.g., aryl groups with 6 to 10 carbon atoms).

[0034] When the main chain has a structure in which an alkylene group, which may have substituents, is directly bonded to a benzene ring (provided that the carbon atoms of the alkylene group directly bonded to the benzene ring have at least one hydrogen atom), it is preferable that the main chain has a structure in which an alkylene group having an aryl group with 6 to 10 carbon atoms is directly bonded to a benzene ring.

[0035] Aromatic polyamide-imide resins are resins obtained by reacting monomer components such as aromatic diamine compounds, aromatic tetracarboxylic acid compounds, and aromatic dicarboxylic acid compounds, for example. Aromatic polyamide resins are resins obtained by reacting monomer components such as aromatic diamine compounds and aromatic dicarboxylic acid compounds, for example. Aromatic polyimide resins are resins obtained by reacting monomer components such as aromatic diamine compounds and aromatic tetracarboxylic acid compounds, for example. In aromatic polyamide-imide resins, aromatic polyamide resins, and aromatic polyimide resins, the structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring may be present in units derived from aromatic diamine compounds, in units derived from aromatic carboxylic acids (aromatic tetracarboxylic acids or aromatic dicarboxylic acids), or in both units. Preferably, the structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring is present in units derived from aromatic diamine compounds.

[0036] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic diamine compound, it is preferable that the carbon atom containing the hydrogen atom (a predetermined carbon atom) in the structure in which the carbon atom containing the hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded. In other words, a nitrogen atom derived from an amino group is bonded to a benzene ring to which a carbon atom containing a hydrogen atom is directly bonded.

[0037] The resin is more preferably having residues derived from an aromatic diamine compound represented by the following formula (1). [ka] During the ceremony, n is either 0 or 1. R1 and R2 are independently -CH3 and -CH2R, respectively. a ,-CHR b R c ,-CR d R e Rf or halogen atoms, R a ~R e Each of these is independently an alkyl group, an alkenyl group, or an aryl group. X is a single bond, -CH2-, -CHR f -, -CR g R h -, -O-, -S-, -S(=O)2, -C(=O)O-, -C(=O)-NH-, or -C(=O)-, R f ~R h Each of these is independently an alkyl group, an alkenyl group, or an aryl group, or R g and R h These may also form a carbon ring together with the carbon atoms to which they are bonded. p represents an integer from 0 to 4. q represents an integer from 0 to 4. If n is 0, p is an integer greater than or equal to 1, and at least one R1 is -CH3, -CH2R a or -CHR b R c And, If n is 1, then at least one of the following conditions (i) to (iii) is satisfied. (i) X is -CH2- or -CHR f - is (ii) p is an integer greater than or equal to 1, and at least one R1 is -CH3, -CH2R a or -CHR b R c That is (iii) q is an integer greater than or equal to 1, and at least one R2 is -CH3, -CH2R a or -CHR b R c That is the case.

[0038] In formula (1), examples of halogen atoms include fluorine atoms, chlorine atoms, bromine atoms, iodine atoms, etc., and chlorine atoms are preferred.

[0039] In formula (1), the alkyl group may be linear or branched, and examples include alkyl groups having 1 to 6 carbon atoms, preferably alkyl groups having 1 to 4 carbon atoms, such as a methyl group or an ethyl group.

[0040] In formula (1), the alkenyl group may be an alkenyl group having 2 to 6 carbon atoms, preferably an alkenyl group having 2 to 4 carbon atoms, such as a vinyl group.

[0041] In formula (1), the aryl group may be an aryl group having 6 to 15 carbon atoms, preferably an aryl group having 6 to 12 carbon atoms, such as a phenyl group or a naphthyl group.

[0042] R g and R h These may form a carbocyclic ring together with the carbon atoms to which they are bonded. The carbocyclic ring is not particularly limited as long as the ring constituent atoms are carbon atoms, and may be an unsaturated or saturated fatty ring or an aromatic ring. The ring may be monocyclic or polycyclic, and in the case of polycyclic, it may be a fused polycyclic ring. The ring may have 30 or fewer carbon atoms, and examples include indan rings and fluorene rings, with the formation of a fluorene ring being preferable.

[0043] When n is 0, the aromatic diamine compound represented by formula (1) above is preferably represented by the following formula (1-1). [ka] During the ceremony, R3 is -CH3, -CH2R a or -CHR b R c This represents, R a ~R c This is equivalent to equation (1), p1 is an integer between 1 and 4.

[0044] When n is 1, the aromatic diamine compound represented by formula (1) above is preferably represented by the following formula (1-2A) or formula (1-2B). [ka] During the ceremony, R3 and R4 are -CH3 and -CH2R a or -CHR b R c This represents, R a ~R c This is equivalent to equation (1), X, p, and q are equivalent to those in equation (1), but p and q cannot be zero at the same time. [ka] In the formula, R1, R2, p, and q are equivalent to those in formula (1) above. Y is either -CH2- or -CHR f -and, R f This is equivalent to equation (1).

[0045] In the above formula (1-2A), p and q are preferably 1 or 2 independently, and it is more preferable that both p and q are 1.

[0046] In the above formula (1-2A), it is preferable that at least one R3 and R4 are bonded to the amino group at the meta position.

[0047] In the above formula (1-2A), R3 and R4 are preferably -CH3 or -C2H5, respectively.

[0048] In the above formula (1-2A), X is preferably a single bond, a -CH2-, or a fluorene ring residue.

[0049] In the above formula (1-2B), Y is preferably -CH2-.

[0050] In the above formula (1-2B), p and q are preferably 0 or 1 independently, and it is more preferable that both p and q are 0 or both are 1.

[0051] In the above formula (1-2B), R1 and R2 are preferably a methyl group, an ethyl group, or a halogen atom.

[0052] Examples of aromatic diamine compounds represented by formula (1) include 2,2'-dimethylbenzidine, 3,3',5,5'-tetramethylbenzidine, 9,9-bis(4-amino-3-methylphenyl)fluorene, O-tolidine, 4,4'-methylenebis(2-methylaniline), 4,4'-methylenebis(2,6-dimethylaniline), 4,4'-methylenebis(2-ethylaniline), 4,4'-methylenebis(2,6-diethylaniline), and 4,4'-methyl Examples include lenbis(2,6-diisopropylaniline), 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 3,5-diaminotoluene, 2,5-diamino-p-xylene, 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethyl-1,4-phenylenediamine, 4,4'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, and 3,3'-diaminodiphenylmethane. The compounds listed below are, in order from top to bottom, 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene. As the aromatic diamine compound represented by formula (1), 2,2'-dimethylbenzidine is preferred in terms of improving mechanical strength while maintaining the transparency of the resin film, and 9,9-bis(4-amino-3-methylphenyl)fluorene is preferred in terms of improving colorlessness while maintaining the transparency of the resin film. [ka]

[0053] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic dicarboxylic acid compound, it is even more preferable that it has a residue derived from an aromatic dicarboxylic acid compound represented by the following formula (2). In the reaction, the aromatic dicarboxylic acid compound may be a derivative such as an acid chloride. [ka] In the equation, R1, R2, X, p, q, and n are equivalent to those in equation (1).

[0054] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic tetracarboxylic acid compound, it is even more preferable that it has a residue derived from an aromatic tetracarboxylic acid compound represented by the following formula (3). In the reaction, the aromatic tetracarboxylic acid compound may be a derivative of an acid anhydride, acid chloride, etc. [ka] In the formula, R1, R2, p, q, and X are synonymous with formula (1), and the examples and preferred examples described with respect to formula (1) apply.

[0055] Examples of aromatic dicarboxylic acid compounds represented by formula (2) or aromatic tetracarboxylic acid compounds represented by formula (3) include 4,4'-methylenedibenzoic acid, 2-methylterephthalic acid, and 2,5-dimethylterephthalic acid. In the reaction, derivatives of these compounds, such as acid chlorides, may also be used.

[0056] In the resin composition of this embodiment, if the resin has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the resin in the resin film of this embodiment does not have perfluoroalkyl and polyfluoroalkyl portions. Here, perfluoroalkyl and polyfluoroalkyl portions refer to "portions containing a completely fluorinated methyl group or methylene group (a carbon atom to which fluorine is bonded that does not have H, Cl, Br, or I atoms bonded)." This is because if the resin in the resin film of this embodiment has perfluoroalkyl and polyfluoroalkyl portions, the resin may fall under the category of PFAS and be subject to legal regulations. Specifically, the perfluoroalkyl and polyfluoroalkyl moieties include, for example, trifluoromethyl (-CF3) and perfluoroalkylene (-CF2). n -) (provided that the carbon atom to which fluorine is bonded does not have H, Cl, Br, or I atoms bonded to it), and these may further be bonded to alkyl groups or alkylene groups, specifically, for example, -(CH2) n The group represented by CF3, -(CF2) n Examples include groups represented by CH3.

[0057] In the resin film of this embodiment, the proportion of units having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring is preferably 10 mol% or more, due to excellent transparency resulting from solvent solubility and amorphous properties. The proportion of units having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring may be 100 mol%, but in order to obtain the effect of introducing units other than those having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring, units that do not have a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring (hereinafter also referred to as "other units") may be introduced. By introducing other units, it is also possible to suppress yellowing caused by oxidation of the structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring. In the resin composition of this embodiment, the proportion of units having an alkyl group having a hydrogen atom at the benzyl position is preferably 90 mol% or less, more preferably 70 mol% or less, and particularly preferably 55 mol% or less, in the total units of the resin.

[0058] When a unit derived from an aromatic diamine compound has a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring, the proportion of units having this structure among all units derived from the aromatic diamine compound is preferably 20 mol% or more, and more preferably 50 mol% or more. The proportion of units having this structure among all units derived from the aromatic diamine compound may be 100 mol%, but units derived from aromatic diamine compounds that do not have a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring (hereinafter also referred to as "other aromatic diamine compounds") may be introduced. When introducing units derived from other aromatic diamine compounds, the proportion of such units is preferably 10 mol% or more, and more preferably 20 mol% or more, in order to enjoy the effects thereon. If a unit derived from an aromatic diamine compound has a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring, then units derived from aromatic dicarboxylic acid compounds and / or aromatic tetracarboxylic acid compounds may only be units derived from aromatic dicarboxylic acid compounds that do not have a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring (hereinafter also referred to as "other aromatic dicarboxylic acid compounds") and / or aromatic tetracarboxylic acid compounds that do not have a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring (hereinafter also referred to as "other aromatic dicarboxylic acid compounds").

[0059] When a unit derived from an aromatic dicarboxylic acid compound or aromatic tetracarboxylic acid compound has a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring, the proportion of units having this structure among all units derived from the aromatic dicarboxylic acid compound or aromatic tetracarboxylic acid compound is preferably 20 mol% or more, and more preferably 50 mol% or more. The proportion of units having this structure among all units derived from the aromatic dicarboxylic acid compound or aromatic tetracarboxylic acid compound may be 100 mol%, but units derived from other aromatic dicarboxylic acid compounds or other aromatic tetracarboxylic acid compounds may also be introduced. When units derived from other aromatic dicarboxylic acid compounds or other aromatic tetracarboxylic acid compounds are introduced, the proportion of such units is preferably 10 mol% or more, and more preferably 20 mol% or more, in order to enjoy the effects thereon. If a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic dicarboxylic acid compound or an aromatic tetracarboxylic acid compound, then the unit derived from the aromatic diamine compound may consist only of units derived from other aromatic diamine compounds.

[0060] Furthermore, when a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring exists in units derived from aromatic dicarboxylic acid compounds and aromatic tetracarboxylic acid compounds, the proportion of units having a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring among all units derived from aromatic dicarboxylic acid compounds and aromatic tetracarboxylic acid compounds is preferably 20 mol% or more, and more preferably 50 mol% or more. The proportion of units having a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring among all units derived from aromatic dicarboxylic acid compounds and aromatic tetracarboxylic acid compounds may be 100 mol%, but units derived from other aromatic dicarboxylic acid compounds and other aromatic tetracarboxylic acid compounds may also be introduced. When units derived from other aromatic dicarboxylic acid compounds and other aromatic tetracarboxylic acid compounds are introduced, the proportion of such units is preferably 10 mol% or more, and more preferably 20 mol% or more, in order to enjoy the effects thereon. If a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in units derived from aromatic dicarboxylic acid compounds and aromatic tetracarboxylic acid compounds, then units derived from aromatic diamine compounds may consist only of units derived from other aromatic diamine compounds.

[0061] In this embodiment, to ensure colorlessness, it is preferable to use units in which a fluorine atom is directly bonded to an aromatic ring as another unit. The units in which a fluorine atom is directly bonded to an aromatic ring may be present in units derived from aromatic diamine compounds, in units derived from aromatic carboxylic acids (aromatic tetracarboxylic acids or aromatic dicarboxylic acids), or in both units. Preferably, the units in which a fluorine atom is directly bonded to an aromatic ring are present in units derived from aromatic diamine compounds.

[0062] When a unit in which a fluorine atom is directly bonded to an aromatic ring exists in a unit derived from an aromatic diamine compound, it is preferable that the fluorine is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0063] For example, it is even more preferable to have a residue derived from 9,9-bis(4-amino-3-fluorophenyl)fluorene, represented by the following formula. [ka]

[0064] When a unit in which a fluorine atom is directly bonded to an aromatic ring is present in a unit derived from an aromatic dicarboxylic acid compound, it is preferable to have a residue derived from 2-fluoroterephthalic acid chloride, for example, represented by the following formula. [ka]

[0065] In the resin film of this embodiment, if the resin contains units derived from aromatic diamine compounds and units derived from aromatic dicarboxylic acids, it is preferable that the resin contains units derived from aromatic diamine compounds having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring, and units derived from other aromatic dicarboxylic acid compounds. More preferably, the units derived from aromatic diamine compounds present in the resin consist of units derived from aromatic diamine compounds having a structure in which a carbon atom with a hydrogen atom is directly bonded to a benzene ring, and the units derived from aromatic dicarboxylic acids present in the resin consist of units derived from other aromatic dicarboxylic acid compounds.

[0066] Specifically, in the resin film of this embodiment, if units derived from aromatic diamine compounds and units derived from aromatic dicarboxylic acids are present, it is preferable that the resin has units derived from at least one aromatic diamine compound selected from 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene, and units derived from at least one aromatic dicarboxylic acid compound selected from terephthalic acid, terephthalic acid derivatives, 4,4'-oxybisbenzoic acid, and 4,4'-oxybisbenzoic acid derivatives, and it is more preferable that the resin has units derived from at least one aromatic diamine compound selected from 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene, and units derived from at least one aromatic dicarboxylic acid compound selected from terephthalic acid chloride (TPC) and 4,4'-oxybis(benzoyl chloride) (DEDC).

[0067] In the resin film of this embodiment, if the resin contains units derived from aromatic diamine compounds and units derived from aromatic dicarboxylic acids, it is preferable that the units derived from aromatic diamine compounds further have residues derived from 9,9-bis(4-amino-3-fluorophenyl)fluorene, 9,9'-bis(4-aminophenyl)fluorene, or 2,2'-bis[4-(4-aminophenoxy)phenyl]propane, in order to ensure colorless transparency. Furthermore, the resin in the resin film of this embodiment preferably has units derived from at least one aromatic diamine compound selected from 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene, residues derived from 9,9-bis(4-amino-3-fluorophenyl)fluorene, and units derived from at least one aromatic dicarboxylic acid compound selected from terephthalic acid, terephthalic acid derivatives, 4,4'-oxybisbenzoic acid, and 4,4'-oxybisbenzoic acid derivatives. It is also preferable that the resin has units derived from at least one aromatic diamine compound selected from 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene, and units derived from at least one aromatic dicarboxylic acid compound selected from terephthalic acid chloride (TPC) and 4,4'-oxybis(benzoyl chloride) (DEDC).

[0068] The following describes aromatic polyamide-imide resins, aromatic polyamide resins, and aromatic polyamide resins, respectively.

[0069] [Aromatic polyamide-imide resin] Aromatic polyamide-imide resins are polyamide-imide resins in which nitrogen atoms derived from amino groups are directly bonded to aromatic rings (having aromatic rings in the main chain). Aromatic polyamide-imide resins are resins obtained, for example, by reacting monomer components such as aromatic diamine compounds, aromatic tetracarboxylic acid compounds, and aromatic dicarboxylic acid compounds. Specifically, aromatic polyamide-imide resins are obtained by reacting aromatic diamine compounds with aromatic tetracarboxylic acid compounds to synthesize a polymer having an imide precursor structure, then reacting the polymer with an aromatic dicarboxylic acid compound to synthesize a copolymer having an imide precursor structure and an amide structure, and then performing a ring-closing reaction (imidization) on the imide precursor structure in the copolymer. Alternatively, a polymer having an imide precursor structure may be synthesized by reacting aromatic diamine compounds with aromatic tetracarboxylic acid compounds, and after performing a ring-closing reaction on the imide precursor, it may be reacted with an aromatic dicarboxylic acid compound to synthesize a copolymer (aromatic polyamide-imide resin) having an imide structure and an amide structure.

[0070] Aromatic polyamide-imide resins have a structure in which residues obtained by reacting aromatic diamine compounds and aromatic tetracarboxylic acid compounds are bonded via imide structures to structural units, and residues obtained by reacting aromatic dicarboxylic acid compounds are bonded via amide structures to these units.

[0071] The aromatic polyamide-imide resin in the resin film of this embodiment has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring. In this case, it is preferable that the carbon atom having a hydrogen atom (a predetermined carbon atom) in the structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded is directly bonded.

[0072] When a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic diamine compound, it is preferable that the carbon atom having a hydrogen atom in the structure in which the carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0073] Furthermore, if a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic diamine compound, it is more preferable that the aromatic polyamide-imide resin in the resin composition of this embodiment has a residue derived from the aromatic diamine compound represented by formula (1) above. For an explanation of formula (1), refer to the explanation in the (Resin) section.

[0074] Furthermore, aromatic diamine compounds include, for example, 2,4-toluenediamine, 2,2'-dimethylbenzidine, 9,9-bis(4-amino-3-methylphenyl)fluorene, p-phenylenediamine, m-phenylenediamine, 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, and 3,3'-diamino Examples of aromatic diamine compounds include diphenylsulfone, 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, 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-chlorophenyl)fluorene, and 9,9-bis(4-amino-3-fluorophenyl)fluorene. Among these, at least one aromatic diamine acid compound selected from 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-methylphenyl)fluorene is preferred, which is an aromatic diamine compound represented by formula (1) above, having a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring. These aromatic diamine compounds may be used individually or in combination of two or more. Furthermore, from the viewpoint of being colorless, it is preferable to combine at least one aromatic diamine compound selected from 9,9-bis(4-amino-3-fluorophenyl)fluorene, 9,9-bis(4-aminophenyl)fluorene, and 2,2-bis[4-(4-aminophenoxy)phenyl]propane.

[0075] Furthermore, if the aromatic diamine compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic diamine compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0076] Aromatic dicarboxylic acid compounds used in the synthesis of aromatic polyamide-imide resins include aromatic dicarboxylic acids or aromatic dicarboxylic acid derivatives. Examples of aromatic dicarboxylic acid derivatives include acid chlorides and esters of the aromatic dicarboxylic acid. Aromatic dicarboxylic acid compounds may be used individually or in combination of two or more.

[0077] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic dicarboxylic acid compound, it is even more preferable that it has a residue derived from an aromatic dicarboxylic acid compound represented by formula (2) above. In the reaction, the aromatic dicarboxylic acid compound may be a derivative of an acid chloride or the like. For an explanation of formula (2), refer to the explanation in the (Resin) section.

[0078] Specific examples of aromatic dicarboxylic acid compounds include, for example, 2-methylterephthalic acid, 2-fluoroterephthalic acid, 4,4'-methylenedibenzoic acid, 2,5-dimethylterephthalic 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 aromatic dicarboxylic acids and their derivatives (e.g., acid chlorides, acid anhydrides) in which two benzoic acids are linked by a single bond, -C(CH3)2-, -SO2-, or phenylene group. Among these, 2-methylterephthalic acid, which is an aromatic dicarboxylic acid compound represented by formula (2) above, is preferred. These aromatic dicarboxylic acid compounds may be used individually or in combination of two or more.

[0079] Among aromatic dicarboxylic acid compounds, terephthalic acid, 4,4'-oxybisbenzoic acid, or their derivatives are preferred, particularly terephthalic acid chloride (sometimes denoted as TPC) or 4,4'-oxybis(benzoyl chloride) (sometimes denoted as DEDC), as these improve the elongation at the breaking point and elastic modulus of the film.

[0080] Furthermore, if the aromatic dicarboxylic acid compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic dicarboxylic acid compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0081] Aromatic tetracarboxylic acid compounds used in the synthesis of aromatic polyamide-imide resins include aromatic tetracarboxylic acids or aromatic tetracarboxylic acid derivatives. Aromatic tetracarboxylic acid derivatives include anhydrides of aromatic tetracarboxylic acids, preferably dianhydrides or acid chlorides. These aromatic tetracarboxylic acid compounds may be used individually or in combination of two or more.

[0082] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic tetracarbone compound, it is preferable that the structure in which the carbon atom containing a hydrogen atom is directly bonded to a benzene ring to which a residue derived from a carboxyl group is attached, and it is even more preferable that it has a residue derived from the aromatic tetracarboxylic acid compound represented by formula (3) above. In the reaction, the aromatic tetracarboxylic acid compound may be a derivative of an acid anhydride, acid chloride, etc. For the explanation of formula (3), refer to the explanation in the (resins) section.

[0083] Specific examples of aromatic tetracarboxylic acid compounds 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'-(5-methylbiphenyltetracarboxylic dianhydride), 4,4'-oxydiphthalic acid dianhydride (sODPA), 3,4-oxydiphthalic acid dianhydride (aODPA), 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic acid 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, and 9,9-bis(3,4-dicarboxyphenyl)fluorenic acid dianhydride. Examples include (BPAF), 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 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 acid dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic acid dianhydride. Furthermore, 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. Among these, 4,4'-(5-methylbiphenyltetracarboxylic dianhydride), which is the aromatic tetracarboxylic compound represented by the above formula (3A), is preferred.

[0084] Among aromatic tetracarboxylic acid compounds, it is preferable to use a combination of at least one selected from the group consisting of 4,4'-(4,4'-isopropylidene diphenoxy)diphthalic acid dianhydride (BPADA), 3,4-oxydiphthalic acid dianhydride (aODPA), 4,4'-oxydiphthalic acid dianhydride (sODPA), 2,2',3,3'-biphenyltetracarboxylic acid dianhydride (aBPDA), and 9,9-bis(3,4-dicarboxyphenyl)fluorenic acid dianhydride (BPAF), in order to improve transparency without impairing various properties such as heat resistance and mechanical strength as a film.

[0085] Furthermore, if the aromatic tetracarboxylic acid compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic tetracarboxylic acid compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0086] In the synthesis of aromatic polyamide-imide resins, the molar ratio of monomer components (aromatic diamine compound: aromatic tetracarboxylic acid compound: aromatic 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. According to the above-mentioned monomer component ratio, the molar ratio of imide structures to amide structures in the structure of the aromatic polyamide-imide resin is preferably 0.5 to 4:3 to 6.5, more preferably 1.5 to 3.5:3.5 to 5.5, and particularly preferably 2.5 to 3.5:3.5 to 4.5. By having the above-mentioned molar ratio of imide structures to amide structures, it is possible to achieve a good balance between excellent flexibility and high elasticity.

[0087] In the synthesis of aromatic polyamide-imide resins, the ring-closing reaction (imidization) of the imide precursor can be carried out by either thermal imidization, which involves adding an azeotropic solvent that forms an azeotrope with water (e.g., toluene, xylene, etc.) and heating, or chemical imidization, which uses a condensing agent and a reaction accelerator. However, chemical imidization is preferred because it is easier to maintain colorless transparency.

[0088] Examples of condensing agents used in chemical imidation include acid anhydrides such as acetic anhydride, propionic anhydride, and trifluoroacetic anhydride, as well as phosphite esters such as triethyl phosphite, tributyl phosphite, dimethyl phosphite, diethyl phosphite, and triphenyl phosphite. These condensing agents may be used individually or in combination of two or more.

[0089] Examples of reaction accelerators used in chemical imidation 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 individually or in combination of two or more.

[0090] Organic solvents can be used in the synthesis of aromatic polyamide-imide resins. Such organic solvents are not particularly limited as long as they are inert to the reaction, and examples 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 individually or in combination of two or more.

[0091] For the synthesis of aromatic polyamide-imide resins, the reaction conditions can be a temperature of 10 to 50°C and a time of 1 to 27 hours. Furthermore, to maintain colorlessness and transparency, it is preferable to synthesize the resins under a nitrogen atmosphere.

[0092] The weight-average molecular weight (Mw) of the aromatic polyamide-imide resin is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 80,000 to 600,000, and even more preferably in the range of 120,000 to 300,000, from the viewpoint of improving the elastic modulus and elongation at the breaking point. In this specification, the weight-average molecular weight (Mw) is measured by GPC (gel permeation chromatography).

[0093] [Aromatic polyamide resin] Aromatic polyamide resins are polyamide resins in which nitrogen atoms derived from amino groups are directly bonded to aromatic rings (having aromatic rings in the main chain). Aromatic polyamide resins are resins obtained, for example, by reacting aromatic diamine compounds and aromatic dicarboxylic acid compounds, which are monomer components. That is, aromatic polyamide resins are resins having an amide structure formed by the reaction of, for example, an aromatic diamine compound and an aromatic dicarboxylic acid compound. Furthermore, aromatic polyamide resins differ from the aforementioned polyamide-imide resins in that the structure that binds the constituent monomer components substantially does not have an imide structure. Moreover, it is preferable that the structure that binds the constituent monomer components of an aromatic polyamide resin substantially contains no structures other than amide structures and consists of amide structures. In this specification, the structure that binds the constituent monomer components does not include the structure in which the end-capturing agent described later binds to the polyamide resin.

[0094] The diamine compounds used in the synthesis of aromatic polyamide resins are the same as those used in the synthesis of polyamide-imide resins (including examples and preferred examples) as described above. The diamine compounds may be used individually or in combination of two or more.

[0095] The aromatic polyamide resin in the resin film of this embodiment has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring. In the structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring, it is preferable that the carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0096] When a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic diamine compound, it is preferable that the carbon atom having a hydrogen atom in the structure in which the carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0097] Furthermore, it is more preferable that the aromatic polyamide resin in the resin film of this embodiment has residues derived from the aromatic diamine compound represented by formula (1) above. For an explanation of formula (1), refer to the explanation in the (Resin) section.

[0098] Specific examples of aromatic diamine compounds are the same as the specific examples and preferred examples described in the section on polyamide-imide resins. Aromatic diamine compounds may be used individually or in combination of two or more.

[0099] Furthermore, if the aromatic diamine compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic diamine compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0100] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic dicarboxylic acid compound, it is even more preferable that it has a residue derived from an aromatic dicarboxylic acid compound represented by formula (2) above. In the reaction, the aromatic dicarboxylic acid compound may be a derivative of an acid chloride or the like. For an explanation of formula (2), refer to the explanation in the (Resin) section.

[0101] Specific examples of aromatic dicarboxylic acid compounds are the same as those described in the section on polyamide-imide resins. Aromatic dicarboxylic acid compounds may be used individually or in combination of two or more.

[0102] Among aromatic dicarboxylic acid compounds, terephthalic acid, 4,4'-oxybisbenzoic acid, or their derivatives, particularly terephthalic acid chloride (TPC) or 4,4'-oxybis(benzoyl chloride) (DEDC), are preferred because they improve the elongation at the breaking point and elastic modulus of the film. It is also preferable to use TPC and DEDC in combination as the aromatic dicarboxylic acid compound.

[0103] Aromatic polyamide resins can be produced by methods known for producing polyamides, such as solution polymerization, interfacial polymerization, melt polymerization, solid-phase polymerization, and precipitate polymerization. In particular, solution polymerization and interfacial polymerization are preferably used for producing aromatic polyamide resins.

[0104] Specifically, for example, aromatic polyamide resins can be synthesized by solution polymerization from aromatic diamine compounds and acid chlorides of aromatic dicarboxylic acids as aromatic dicarboxylic acid compounds. In this case, the reaction can be carried out in an aprotic organic polar solvent. Although hydrogen chloride is produced as a by-product in this reaction, inorganic neutralizing agents such as calcium hydroxide, calcium carbonate, and lithium carbonate, or organic neutralizing agents such as 1,2-butylene oxide, ethylene oxide, propylene oxide, ammonia, and pyridine can be used to neutralize it.

[0105] Examples of aprotic organic polar solvents 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 individually or in combination of two or more. Aromatic hydrocarbons such as xylene and toluene can also be used. Furthermore, to promote the dissolution of polymers, a salt of an alkali metal or alkaline earth metal in an amount of 50% by mass or less may be added to the solvent.

[0106] When using aromatic polyamide resins, it is preferable to encapsulate the ends of the aromatic polyamide resin to improve the colorless transparency of the film. Examples of compounds used for encapsulating the ends of aromatic polyamide resins include acetyl chloride, benzoyl chloride, substituted benzoyl chloride, acetic anhydride, 5-norbornene-2,3-dicarboxylic acid anhydride, 4-ethynylaniline, 4-phenylethynylphthalic anhydride, and maleic anhydride.

[0107] For the synthesis of aromatic polyamide resins, the reaction conditions can be a temperature of 10 to 50°C and a time of 10 minutes to 27 hours. Furthermore, to maintain colorlessness and transparency, it is preferable to synthesize the resins under a nitrogen atmosphere.

[0108] Aromatic polyamide resins are preferably characterized by a number-average molecular weight (Mn) of 5,000 to 200,000, and more preferably 10,000 to 180,000, as this improves their mechanical properties.

[0109] The aromatic polyamide resin preferably has a weight-average molecular weight (Mw) of 120,000 or more and 300,000 or less. When the weight-average molecular weight (Mw) of the polyamide resin is 120,000 or more, the appearance and / or mechanical properties of the film can be further improved, and when it is 300,000 or less, the handling during the synthesis of the polyamide resin and the manufacture of the polyamide film can be further improved. From a similar viewpoint, the weight-average molecular weight (Mw) of the aromatic polyamide resin in the resin film of this embodiment is more preferably 120,000 or more, even more preferably 150,000 or more, even more preferably 300,000 or less, and even more preferably 250,000 or less. These upper and lower limits can be appropriately rearranged.

[0110] The aromatic polyamide resin preferably has a dispersion degree (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.

[0111] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) were measured by GPC (Gel Permeation Chromatography) and calculated using polystyrene equivalents.

[0112] [Aromatic polyimide resin] Aromatic polyimide resins are polyimide resins in which nitrogen atoms derived from amino groups are directly bonded to aromatic rings (having aromatic rings in the main chain). Aromatic polyimide resins are resins obtained, for example, by reacting aromatic diamine compounds and aromatic tetracarboxylic acid compounds, which are monomer components. That is, aromatic polyimide resins are resins having imide structures formed by the reaction of, for example, aromatic diamine compounds and aromatic tetracarboxylic acid compounds. Furthermore, aromatic polyimide resins differ from the aforementioned polyamide-imide resins in that the structures that bond the constituent monomer components substantially do not have amide structures. Moreover, it is preferable that aromatic polyimide resins consist of imide structures, and that the structures that bond the constituent monomer components substantially do not contain structures other than imide structures.

[0113] The aromatic polyimide resin in the resin film of this embodiment has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring. In the structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring, it is preferable that the carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0114] When a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic diamine compound, it is preferable that the carbon atom having a hydrogen atom in the structure in which the carbon atom having a hydrogen atom is directly bonded to a benzene ring to which a nitrogen atom derived from an amino group is bonded.

[0115] Furthermore, it is more preferable that the aromatic polyimide resin in the resin film of this embodiment has residues derived from the aromatic diamine compound represented by formula (1) above. For an explanation of formula (1), refer to the explanation in the (Resin) section.

[0116] Specific examples of aromatic diamine compounds are the same as those described in the section on polyamide-imide resins. Aromatic diamine compounds may be used individually or in combination of two or more.

[0117] As the aromatic diamine compound represented by formula (1) above, 2,2'-dimethylbenzidine is preferred from the viewpoint of obtaining a polyimide resin with excellent transparency and mechanical strength, and 9,9-bis(4-amino-3-methylphenyl)fluorene is preferred from the viewpoint of obtaining a polyimide resin with excellent colorlessness. These may be used individually or in combination of two or more.

[0118] Furthermore, if the aromatic diamine compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic diamine compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0119] When a structure in which a carbon atom containing a hydrogen atom is directly bonded to a benzene ring exists in a unit derived from an aromatic tetracarbone compound, it is preferable that the structure in which the carbon atom containing a hydrogen atom is directly bonded to a benzene ring to which a residue derived from a carboxyl group is attached, and it is even more preferable that it has a residue derived from the aromatic tetracarboxylic acid compound represented by formula (3) above. In the reaction, the aromatic tetracarboxylic acid compound may be a derivative of an acid anhydride, acid chloride, etc. For the explanation of formula (3), refer to the explanation in the (resins) section.

[0120] Specific examples of aromatic tetracarboxylic acid compounds represented by formula (3A) above, and aromatic dicarboxylic acid compounds other than those represented by formula (3A) above, are the same as the specific examples described in the section on polyamide-imide resins. Aromatic dicarboxylic acid compounds may be used individually or in combination of two or more.

[0121] Furthermore, if the aromatic tetracarboxylic acid compound has a fluorinated alkyl group, it is preferable that at least one hydrogen atom, chlorine atom, bromine atom, or iodine atom is bonded to the carbon atom of the fluorinated alkyl group. In other words, it is preferable that the aromatic tetracarboxylic acid compound does not have a perfluoroalkyl moiety or a polyfluoroalkyl moiety.

[0122] Aromatic polyimide resins can be produced by known methods for producing aromatic polyimides. For example, they can be produced by reacting an aromatic tetracarboxylic acid compound with an aromatic diamine compound to synthesize an imide precursor (polyamic acid resin), followed by a ring-closing reaction (imidization) of the imide precursor. The conditions for the ring-closing reaction are the same as those described above (including examples and preferred examples) for the ring-closing reaction of the imide precursor in the synthesis of aromatic polyamide-imide resins.

[0123] The weight-average molecular weight (Mw) of the aromatic polyimide resin is preferably in the range of 50,000 to 1,000,000, more preferably in the range of 80,000 to 600,000, and even more preferably in the range of 120,000 to 300,000, from the viewpoint of improving the elastic modulus and elongation at the breaking point. The weight-average molecular weight (Mw) is measured by GPC (gel permeation chromatography).

[0124] The resin film of this embodiment may contain other components in addition to the specific resin, as long as they do not impair the effects of the present invention.

[0125] (Antioxidant) The resin film of this embodiment may contain an antioxidant. By incorporating an antioxidant, oxidation of the resin film can be prevented, and through this, yellowing of the resin film can be effectively prevented, resulting in a resin film with excellent colorlessness.

[0126] The antioxidant content in the resin film of this embodiment is preferably 0.01 parts by mass or more and 20 parts by mass or less per 100 parts by mass of resin. Having an antioxidant content within this range allows for greater suppression of yellowing of the film when it is formed using the resin film of this embodiment. The antioxidant content is more preferably 0.05 parts by mass or more, and even more preferably 0.10 parts by mass or more, per 100 parts by mass of resin. Furthermore, to obtain a film with excellent transparency, the antioxidant content is more preferably 10 parts by mass or less, and even more preferably 5 parts by mass or less, per 100 parts by mass of resin.

[0127] In the resin film of this embodiment, it is preferable that the antioxidant has a boiling point of 170°C or higher. Having a boiling point of 170°C or higher prevents the evaporation of specific antioxidants during heating or other processes when manufacturing the resin film.

[0128] Examples of antioxidants include lactone-based antioxidants, phenol-based antioxidants, phosphite-based antioxidants, sulfur-based antioxidants, and amine-based antioxidants. Among these, lactone-based antioxidants, phenol-based antioxidants, and phosphite-based antioxidants are preferred. Antioxidants may be used individually or in combination of two or more types.

[0129] [Lactone-based antioxidants] Lactone-based antioxidants have the function of capturing carbon radicals, and through the exercise of this function, they can prevent oxidation. For example, lactone-based antioxidants capture carbon radicals that are generated from the bonding of carbon and hydrogen due to heat or light.

[0130] Lactone-based antioxidants refer to antioxidants having a lactone skeleton. Here, a lactone skeleton means a monocyclic or polycyclic atomic group containing a ring having -OC(=O)-. Lactone-based antioxidants that can be used are those described in Japanese Patent Publication No. 7-233160 and Japanese Patent Publication No. 7-247278.

[0131] In the resin film of this embodiment, the lactone skeleton in the lactone-based antioxidant is preferably a 4-20 membered ring, and more preferably a 5-10 membered ring. The lactone skeleton may be a monocycle consisting only of a lactone ring, or it may have an aromatic or non-aromatic hydrocarbon ring or heterocycle fused to the lactone ring. In particular, the lactone skeleton is preferably one in which an aromatic hydrocarbon ring is fused to the lactone ring, and more preferably one in which a benzene ring is fused to the lactone ring.

[0132] Specific examples of lactone-based antioxidants include, for example, 3-(3,4-dimethylphenyl)-5,7-di-tert-butylbenzofuran-2(3H)-one. Furthermore, commercially available lactone-based antioxidants include Irganox HP-136 (registered trademark, manufactured by CIBA SPECIALTY CHEMICALS).

[0133] Lactone-based antioxidants may be used individually or in combination of two or more types.

[0134] [Phenol-based antioxidants] Examples of phenolic antioxidants include styrenephenol, 2,5-di-tert-butyl-hydroquinone, cyclohexylphenol, butylhydroxyanisole, 4,4'-iso-propylenebisphenol, 4,4'-butylidene-bis(3-methyl-6-tert-butylphenol), 1,1-bis-(4-hydrooxyphenyl)cyclohexane, 1,1,3-tris(2-methyl-4-hydrooxy-5-tert-butylphenyl)butane, 4,4'-thiobis(3-methyl-6-tert-butylphenol), 2,2'-thiobis(4-methyl-6-tert-butylphenol), 4,4'-thiobis(2-methyl-6-tert-butylphenol), and N,N'-hexamethylenebis(3,5-di-tert-butylphenol-4-hydroxycinnamamide).

[0135] Furthermore, examples of phenolic antioxidants include phenolic antioxidants having a t-butyl group at one ortho position of the oxygen atom bonded to the benzene ring and an optionally substituted alkyl group at the other ortho position (hereinafter also referred to as "specific phenolic antioxidants"), and specific phenolic antioxidants are preferred from the viewpoint of suppressing yellowing of resin films.

[0136] Certain phenolic antioxidants may have a substructure represented by the following formula (4A). [ka] During the ceremony, R 10 This represents an alkyl group that may be substituted, * represents a coupling.

[0137] R 10Regarding this, the alkyl group may be linear or branched, and examples include alkyl groups having 1 to 6 carbon atoms, such as methyl group, ethyl group, propyl group, isopropyl group, n-butyl group, isobutyl group, sec-butyl group, tert-butyl group, n-pentyl group, isopentyl group, tert-pentyl group, neopentyl group, and 1,2-dimethylpropyl group. Among these, alkyl groups having 1 to 4 carbon atoms are preferred, and methyl group or t-butyl group are more preferred. Furthermore, from the viewpoint of further suppressing yellowing, groups with greater steric hindrance are preferred, and t-butyl group is preferred.

[0138] R 10 The alkyl group in the compound may be substituted, and while not limited to specific substituents, examples of substituents that substitute for the alkyl group include halogen atoms and optionally substituted aryl groups.

[0139] Certain phenolic antioxidants having a substructure represented by formula (4A) capture peroxyl radicals generated by the reaction of carbon radicals with oxygen and donate hydrogen to these peroxyl radicals to convert them into hydroperoxides. This is advantageous because it prevents chain reactions caused by peroxyl radicals and suppresses oxidation.

[0140] Examples of specific phenolic antioxidants having a substructure represented by formula (4A) include 3,9-bis{2-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyl]-1,1-dimethylethyl}-2,4,8,10-tetraoxaspiro[5,5]undecane, 2,6-di-tert-butyl-p-cresol (BHT), 2,4,6-tri-tert-butylphenol, n-octadecyl-3-(4'-hydroxy-3',5'-di-tert-butylphenol)propionate, 4-hydroxymethyl-2,6-di-tert-butylphenol, 2,2'-methylene-bis-(4-methyl-6-tert-butylphenol), and 2,2'-methylene-bis-(4-ethyl Examples include tris(3,5-di-tert-butyl-4-hydroxyphenyl) isocyanurate, tris(3,5-di-tert-butyl-4-hydroxyphenyl)propionyl-oxyethyl) isocyanate, and others.

[0141] The specific phenolic antioxidant may be a commercially available product, such as AO-20, AO-50, AO-60, AO-80, IRGANOX1098, IRGANOX1222, IRGANOX1330, etc.

[0142] Phenolic antioxidants may be used individually or in combination of two or more types.

[0143] [Phosphite-based antioxidants] Phosphate antioxidants include 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, triphenyl phosphite, 2-ethylhexyl phosphate, dilauryl phosphite, tri-iso-octyl phosphite, tris(2,4-di-tert-butylphenyl) phosphite, trilauryl phosphite, trilauryl-di-thiophosphite, trilauryl-tri-thiophosphite, trisnonylphenyl phosphite, distearyl pentaerythritol diphosphite, tris(mononylphenyl) phosphite, tris(dinonylphenyl) phosphite, trioctadecyl phosphite, and 1,1,3-tris(2-methyl-di-tridecyl phosphite-5-tert Examples include butylphenyl)butane, 4,4'-butyllidene-bis(3-methyl-6-tert-butyl)tridecyl phosphite, 4,4'-butyllidene-bis(3-methyl-6-tert-butyl-di-tridecyl) phosphite, bis(2,4-di-tert-butylphenyl)pentaerythritol-di-phosphite, tetrakis(2,4-di-tert-butylphenyl)4,4'-bisphenylenediphosphite, distearylpentaerythritol diphosphite, tridecyl phosphite, tristearyl phosphite, sorbitol-tris-phosphite-distearyl-mono-C30-diol ester, and bis(2,4,6-tri-tert-butylphenyl)pentaerythritol diphosphite.

[0144] Furthermore, examples of phosphite-based antioxidants include phosphite-based antioxidants having a t-butyl group at one ortho position of an oxygen atom bonded to a benzene ring and an optionally substituted alkyl group at the other ortho position (hereinafter also referred to as "specific phosphite-based antioxidants"), and such phosphite-based antioxidants are preferred from the viewpoint of suppressing yellowing of resin films.

[0145] A phosphite-based antioxidant having a t-butyl group at one ortho position of an oxygen atom bonded to a benzene ring, and an optionally substituted alkyl group at the other ortho position, may have a substructure represented by the following general formula (4B). [ka] During the ceremony, R 10 This is synonymous with formula (4A), and the examples and preferred examples apply. * represents a coupling.

[0146] In the above equation (4B), R 10 The alkyl group may form a ring with the -O- bonded to the lilin atom in formula (4B) via substituents.

[0147] Examples of specific phosphite-based antioxidants include 3,9-bis(2,4-di-tert-butylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane 3,9-dioxide, bis(2,6-di-tert-butyl-4-methylphenyl)pentaerythritol-di-phosphite, and 2,2'-methylenebis(4,6-di-tert-butylphenyl)octylphosphite.

[0148] The specific phosphite antioxidant may be a commercially available product, such as HP-10 or PEP-36.

[0149] Phosphate antioxidants may be used individually or in combination of two or more types.

[0150] [Amine-based antioxidants] Examples of amine-based antioxidants include 4,4'-bis(α,α-dimethylbenzyl)diphenylamine, phenyl-α-naphthylamine, phenyl-β-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-di-β-naphthyl-p-phenylenediamine, N-cyclohexyl-N'-phenyl-p-phenylenediamine, N-phenyl-N'-isopropyl-p-phenylenediamine, aldol-α-naphthylamine, polymers of 2,2,4-trimethyl-1,2-dihydroquinone, and 6-ethoxy-2,2,4-trimethyl-1,2-dihydroquinoline.

[0151] [Sulfur-based antioxidants] Examples of sulfur-based antioxidants include thiobis(β-naphthol), thiobis(N-phenyl-β-naphthylamine), 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, dodecyl mercaptan, tetramethylthiuram monosulfide, tetramethylthiuram disulfide, nickel dibutyldithiocarbamate, nickel isopropyl xanthate, dilauryl thiodipropionate, and distearyl thiodipropionate.

[0152] In order to ensure colorlessness, the resin film of this embodiment preferably contains one or more antioxidants selected from the group consisting of lactone-based antioxidants, specific phenol-based antioxidants, and specific phosphite-based antioxidants.

[0153] (Phosphate ester compounds or phosphonic acid compounds) The resin film of this embodiment may contain one or more compounds selected from phosphate ester compounds and phosphonic acid compounds (hereinafter sometimes collectively referred to as "phosphorus compounds"). The inclusion of phosphorus compounds in the resin composition is expected to further suppress yellowing and improve the colorlessness of the film. From the viewpoint of suppressing yellowing, the molecular weight of the phosphorus compound is preferably 300 or less, more preferably 250 or less, and even more preferably 200 or less. Within this range, the volatility of the phosphorus compound increases, thus reducing the amount of phosphorus compound remaining in the film using the resin composition. Phosphorus compounds may be used individually or in combination of two or more.

[0154] In this invention, the phosphorus compound differs from phosphite-based antioxidants in that it has a phosphate ester skeleton or a phosphonic acid skeleton.

[0155] In this embodiment, the resin film preferably contains a phosphorus compound in an amount of 1 to 25 parts by mass per 100 parts by mass of resin. Within this range, the effects of including the phosphorus compound can be fully enjoyed. The phosphorus compound content is more preferably 3 parts by mass or more, even more preferably 5 parts by mass or more, even more preferably 40 parts by mass or less, and even more preferably 30 parts by mass or less. Furthermore, when producing a film using a resin composition, phosphorus compounds may volatilize during the drying process. For films using a resin composition, the phosphorus compound content relative to the total mass of the film can be measured using thermogravimetric analysis (TGA).

[0156] Examples of phosphorus compounds include phosphonic acid compounds represented by the following formula (5A), orthophosphate ester compounds represented by the following formula (5B), and condensed phosphate ester compounds represented by the following formula (5C). [ka] During the ceremony, R 21 and R22 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group, and the alkyl group and aryl group may have substituents. R 23 is an alkyl group or an aryl group, and the alkyl group and aryl group may have substituents. [ka] During the ceremony, R 24 ~R 26 Each of these is independently a hydrogen atom, an alkyl group, or an aryl group, and the alkyl group and aryl group may have substituents, however, R 24 ~R 26 Not all of them are hydrogen atoms.

[0157] [ka] [In general formula (5C), R 27 and R 28 The expression is represented as follows: each is independently an alkyl or aryl group which may have substituents, Z is a divalent organic group containing at least one aromatic ring, and n is an integer of 1 or more. The condensed phosphate ester may be used alone or in combination of two or more types.

[0158] In the above general formula (5C), n is preferably 1. Also, in the above general formula (5C), R 27 and R 28 From the viewpoint of obtaining a higher desired effect, it is preferable that Z is an aryl group, and more preferably a phenyl group. Furthermore, in general formula (5C), from the viewpoint of obtaining a higher desired effect, it is preferable that Z contains one or two aromatic rings.

[0159] R in the above formula (5A) 21 and R 22Regarding this, the alkyl group may be either linear or branched, and examples thereof include alkyl groups having 1 to 6 carbon atoms, such as a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a tert-pentyl group, a neopentyl group, a 1,2-dimethylpropyl group, etc. Among them, from the viewpoint of obtaining a higher desired effect, it is preferably an alkyl group having 1 to 3 carbon atoms, and more preferably a methyl group.

[0160] Regarding R in the above formula (5A) 21 and R 22 Regarding this, the aryl group includes aryl groups having 6 to 20 carbon atoms, such as a phenyl group, a naphthyl group, etc. Among them, a phenyl group is preferred.

[0161] The above alkyl group and aryl group may have substituents, and the substituents are not particularly limited, and examples thereof include an alkenyl group, an aryl group, a halogen atom, etc.

[0162] From the viewpoint of obtaining a higher desired effect, R 21 and R 22 are each preferably independently an alkyl group, more preferably an alkyl group having 1 to 3 carbon atoms, and even more preferably both are methyl groups.

[0163] Regarding R in the above formula (5A) 23 Regarding the alkyl group, aryl group and substituent, the examples and preferred examples regarding the above R 21 and R 22 are applicable. R 23 is preferably an aryl group, and more preferably a phenyl group, from the viewpoint of obtaining a higher desired effect.

[0164] Examples of the phosphonic acid-based compound represented by the formula (5A) include dimethyl phenylphosphonate (PPADM), etc.

[0165] Regarding the above formula (5B), for the alkyl group, aryl group and substituent, the above R 21 and R 22 The examples and preferred examples regarding it are applicable. From the viewpoint of obtaining a desired effect higher than that, R 24 ~R 26 are each independently preferably an alkyl group, more preferably an alkyl group having 1 to 3 carbon atoms, and still more preferably a methyl group or an ethyl group. A phenyl group can also be preferably used.

[0166] Examples of the orthophosphoric ester acid compound represented by the formula (5B) include trimethyl phosphate, triethyl phosphate (TEP), triphenyl phosphate, and the like.

[0167] Examples of the condensed phosphate ester compound represented by the formula (5C) include resorcinol bis(diphenyl phosphate), bisphenol A bis(diphenyl phosphate), and the like. Commercially available products of the condensed phosphate ester compound represented by the formula (5C) include FP-900L, PFR, FP-600, etc. of the Adeka Stub series manufactured by Adeka Corporation.

[0168] From the viewpoint of ensuring colorlessness, the resin film of the present embodiment preferably contains one or more selected from the group consisting of the phosphonic acid-based compound represented by the above formula (5A) and the orthophosphoric ester compound represented by the above formula (5B). By combining these with one or more selected from a lactone-based antioxidant, a specific phenolic antioxidant, and a specific phosphite-based antioxidant, a further reduction in the YI value can be achieved.

[0169] (Filler) The resin film of the present embodiment can contain a filler.

[0170] In this embodiment, the resin film preferably contains a filler of 1 to 40 parts by mass per 100 parts by mass of resin. If the filler content is within this range, it is possible to achieve high elasticity while maintaining the various properties required of the film. Similarly, the filler content per 100 parts by mass of resin is more preferably 5 parts by mass or more, and even more preferably 30 parts by mass or less.

[0171] The shape of the filler is not particularly limited and can be fibrous, spherical, plate-shaped, cylindrical, prismatic, flaky, or irregularly shaped. Among these, the shape of the filler is preferably fibrous. That is, the filler is preferably fibrous. In this case, by arranging each fibrous filler in a lattice pattern in the resin composition, it is thought that the effect of increasing elasticity can be imparted while suppressing discoloration, cloudiness, and a decrease in flexibility. Furthermore, compared to spherical or irregularly shaped fillers, fibrous fillers can provide an excellent anti-blocking effect without impairing light transmittance. Specifically, when the resin films of the present invention are stacked or stored in a roll, the fibrous fillers described above can suppress adhesion (blocking) between the resin films, improving storage stability and workability. Furthermore, "fibrous" refers to a shape with an aspect ratio (filler length / filler diameter) of 5 or more.

[0172] 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 fibrous fillers are arranged in a lattice pattern within the resin film, which further enhances the effects of suppressing the reduction in color, turbidity, and flexibility, as well as increasing elasticity. Similarly, the average fiber diameter of the fibrous filler is more preferably 2 nm or more, even more preferably 3 nm or more, even more preferably 25 nm or less, and even more preferably 20 nm or less. Similarly, the average fiber length of the fibrous filler is more preferably 300 nm or more, even more preferably 500 nm or more, even more preferably 3,000 nm or less, and even more preferably 2,000 nm or less.

[0173] The "average fiber diameter" and "average fiber length" are measured by dissolving the resin film in a suitable solvent for the resin constituting the film (e.g., methyl isobutyl ketone (MIBK) or dimethylacetamide (DMAc)) and diluting it 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 it with a scanning probe microscope (e.g., a topographic observation image using Hitachi High-Tech AFM5000II). Furthermore, the fibrous filler to be measured may be a single fiber or a bundle of multiple single fibers, as long as it is visible as a single fiber in the scanning probe microscope image. The number-average length of the diameter in the short-side direction of 200 arbitrarily selected fibrous fillers in the scanning probe microscope image is defined as the "average fiber diameter," and the number-average length of the diameter in the long-side direction is defined as the "average fiber length."

[0174] Fibrous fillers can be mixed with a predetermined resin in powder or dispersion (sol) form, stirred, and kneaded as needed to adjust the dispersion state in the resin film, i.e., the "average fiber diameter" and "average fiber length." For example, stirring or kneading can be performed using stirrers such as dissolvers or butterfly mixers, or kneaders such as roll mills or bead mills. These can be adjusted by 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.

[0175] Fibrous fillers can be surface-treated or used as a dispersion (sol) in an organic solvent. In this case, the dispersion state in the resin composition can be stabilized. In particular, by adjusting the dispersion state of the fibrous filler in the dispersion (sol) 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, consequently, the resin film can be manufactured with high productivity.

[0176] The surface treatment method for the fibrous filler is not particularly limited, and examples include surface treatment using coupling agents such as silane-based, titanate-based, aluminate-based, and zircoaluminate-based agents. Furthermore, the method for preparing the dispersion of the fibrous filler is not particularly limited, and examples include the method for preparing a dispersion treated with an organic sulfonic acid as disclosed in Japanese Patent Application Publication No. 2008-31010.

[0177] The material of the fibrous filler is not particularly limited, but examples include silica, titanium oxide, alumina (including alumina hydrate), silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, etc. Examples of alumina hydrate include boehmite and pseudo-boehmite. These may be used individually or in combination of two or more. Among these, alumina (including alumina hydrate) is preferred as the material of the fibrous filler, boehmite or pseudo-boehmite is more preferred, and pseudo-boehmite is even more preferred. That is, the fibrous filler is preferably a fibrous alumina filler, more preferably a boehmite-type or pseudo-boehmite-type fibrous alumina filler, and even more preferably a pseudo-boehmite-type fibrous alumina filler. In this case, the mechanical and optical properties of the resin film can be further improved.

[0178] (Other ingredients) The resin film of this embodiment can be used with other materials as appropriate, depending on the desired properties. Examples include other resins besides the resin described above, solvents, leveling agents, dispersants, surfactants, retardation modifiers, UV inhibitors, light stabilizers, plasticizers, waxes, pigments, dyes, foaming agents, defoaming agents, dehydrating agents, antistatic agents, antibacterial agents, antifungal agents, bluing agents, pH adjusters, crosslinking agents, lubricants, and the like.

[0179] [Method for manufacturing resin film] The resin film of this embodiment is characterized by comprising a resin composition containing a specific resin.

[0180] The resin film of this embodiment can be produced, for example, by applying a varnish of a resin composition onto a support and drying it as needed.

[0181] Varnishes made from resin compositions can be prepared by dispersing and dissolving specific resins and optional components in a solvent.

[0182] The solvent is not particularly limited and known solvents can be used, for example: 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; solvents having an ether group such as tetrahydrofuran, dioxane, dibutyl ether, and diethylene glycol dimethyl ether (diglyme); acetone, methyl ether Examples include ketone solvents such as ethyl ketone, methyl isobutyl ketone, and cyclohexanone; phenolic solvents such as m-cresol; solvents having a sulfone group such as methanesulfonic acid, dimethyl sulfone, ethylphenyl 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). These solvents may be used individually 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, more preferably one or more selected from dimethylacetamide (DMAc), N-methyl-2-pyrrolidone (NMP), γ-butyrolactone (GBL), and diethylene glycol dimethyl ether (diglyme), and particularly preferably one or more selected from γ-butyrolactone and dimethylacetamide in order to improve the colorlessness of the film.

[0183] The support is not particularly limited and includes, for example, polyester films such as polyethylene terephthalate or polyethylene naphthalate, stainless steel belts, polyimide films, etc. The support can be peeled off from the film as appropriate. The support may be treated with a release agent to facilitate the peeling of the film.

[0184] The means for applying varnish to the support are not particularly limited, and conventionally known methods can be applied, such as the dip coat method, flow coat method, roll coat method, bar coater method, blade coater method, screen printing method, curtain coat method, spray coat method, etc.

[0185] After applying varnish to the support, it is dried as needed. The drying method is not particularly limited, and conventionally known methods can be applied. The drying temperature can be adjusted based on the boiling point of the solvent used in the varnish. To prevent the formation of bubbles in the film, drying can be performed in two stages. For example, primary drying can be performed at 90-150°C for 1-60 minutes, followed by secondary drying at 180-250°C for 1-60 minutes. Furthermore, tertiary heating can be performed to erase the thermal history, and in tertiary heating, the film can be heated to a temperature above its softening point after secondary drying. The atmosphere in which drying is performed is not particularly limited, and it may be done in an air atmosphere or a nitrogen atmosphere.

[0186] In the production of the resin film of this embodiment, from the viewpoint of improving colorlessness, it is preferable to perform drying in two stages, with secondary drying carried out in a nitrogen atmosphere, or to perform primary drying only. When performing primary drying only, it is preferable to perform primary drying under reduced pressure in order to sufficiently remove the solvent, or to perform a wet film formation method as described in Japanese Patent No. 3676218 on the resin film after primary drying.

[0187] The resin film of this embodiment has a film thickness of 30 μm or more, but the film thickness can be adjusted by the amount of varnish applied.

[0188] (YI value) The film of this embodiment has a yellow index value (YI value), which is an indicator of the degree of yellowing, of 10.0 or less, preferably 5.0 or less, and particularly preferably 3.0 or less. The lower limit of the YI value is not particularly limited and can be, for example, -1.0 or more. The YI value is calculated in accordance with ASTM D1925 by measuring the transmittance for light from 300 to 800 nm using a UV-Vis-Near-Infrared spectrophotometer with a C light source and a 2-degree field of view, determining the tristimulus values ​​(X, Y, Z), and using the formula YI = 100 × (1.28X - 1.06Z) / Y. Alternatively, it can be measured using a spectrophotometer in accordance with ASTM D1925.

[0189] (Uses of film) The film of this 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 is particularly preferable to use it as a display component. Examples of display components include organic EL displays, flexible substrates, flexible panels, liquid crystal display devices, touch panels, cover windows, and surface protective films.

[0190] <Flexible Display> The flexible display of this embodiment is characterized by including the above-described film. Because such a flexible display uses the above-described film, it exhibits good colorlessness.

[0191] For example, the resin film of this embodiment can be used as part of the layers of a flexible display, such as a cover window, and bonded to other layers (shatterproof layer, anti-scatter layer, etc.) to create a flexible display. Such a flexible display can be used in flexible devices such as foldable mobile phones or tablets, and deformable solar panels. [Examples]

[0192] The present invention will be described in more detail below with reference to examples, but the present invention is not limited in any way to the following examples.

[0193] <Measurement method> Various measurements of the polyamide resin and polyamide film prepared in the examples were performed according to the following procedure.

[0194] (1) Number average molecular weight (Mn), weight average molecular weight (Mw) The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the polyamide resin were measured using the GL7700 from GL Sciences. Column: TSKgelαM (manufactured by Tosoh Corporation) Column temperature: 40℃ Eluent: NMP solution containing 100 mmol / L H3PO4 (using an 85% aqueous solution of H3PO4 as the raw material) and 10 mmol / L LiBr. Calibration curve: Standard polystyrene Column flow rate: 0.7 mL / min The number-average molecular weight (Mn) and weight-average molecular weight (Mw) are expressed in terms of polystyrene equivalents.

[0195] (2) Film thickness The film thickness was measured using a micrometer (manufactured by Mitutoyo Corporation).

[0196] (3) Total light transmittance and haze The total light transmittance and haze of the films were measured by preparing evaluation samples by cutting each example's film to a size of 30 mm x 30 mm, and measuring each evaluation sample using a haze meter (NDH 7000 II, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with ASTM D1003. Note that a higher total light transmittance value indicates better transparency. Similarly, a lower haze value indicates better transparency.

[0197] (4) YI value (yellowness) Each film was cut into a size of 30 mm × 30 mm, and in accordance with ASTM D1925, the YI value of each film was measured using a spectrophotometer (CM-5, manufactured by Konica Minolta Co., Ltd.). The closer the YI value is to 0, the better the colorlessness is indicated.

[0198] (5) Tensile modulus, elongation at break, maximum point stress The tensile modulus (unit: GPa), elongation at break, and maximum point stress (unit: MPa) of the prepared film were measured using "EZ-SX" manufactured by Shimadzu Corporation under the following conditions. [Test conditions] Sample size: 80 mm × 10 mm Distance between grips: 50 mm Speed: 5 mm / min Number of measurements: 3 times For the filler-added samples, the tensile modulus, elongation at break, and maximum point stress were measured for each of the directions parallel (MD) and perpendicular (TD) to the coating direction when the film was prepared. The larger the value of the tensile modulus (for the filler-added samples, the value of the tensile modulus in the MD direction), the better the mechanical strength is indicated.

[0199] <Monomer raw material: diamine compound> The diamine compounds used as monomer raw materials in each example are as follows. m-Tolidine: 2,2'-dimethylbenzidine FFDA: 9,9-bis(4-amino-3-fluorophenyl)fluorene

[0200] <Monomer raw material: dicarboxylic acid compound> The dicarboxylic acid compounds used as monomer raw materials in each example are as follows. DEDC: 4,4'-oxybisbenzoyl chloride (also referred to as 4,4'-oxybis(benzoic acid chloride))

[0201] <Examples 1 to 4: polyamide film> (Synthesis of polyamide resin) In Example 1, 102.3 g of N,N-dimethylacetamide (DMAc) and 4.8 g of 1,2-butylene oxide were added to a vial containing a stirring bar, and 5.7 g of m-Tolidine and 1.2 g of FFDA were dissolved to obtain a solution. Next, 8.6 g of the dicarboxylic acid compounds shown in Table 1 were added while stirring, and the mixture was reacted at room temperature (approximately 25°C) for 30 minutes to 1 hour. Subsequently, 0.2 g of an end-capturing agent (acetyl chloride) was added to this solution and stirred for 1 hour to obtain a solution containing the polyamide resin synthesized by the above reaction, with a solid content of 11-13% by mass.

[0202] The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained polyamide resins are shown in Table 1.

[0203] (Preparation of polyamide film) Next, the solution containing the obtained polyamide resin (coating liquid) was coated onto a glass substrate using a bar coater to a target thickness of 55 μm after drying. Then, primary drying was performed in a hot air circulation dryer (DH612, manufactured by Yamato Scientific Co., Ltd.) under atmospheric conditions at 120°C for 20 minutes, followed by secondary drying at 220°C for 20 minutes. After drying, the film was allowed to cool at room temperature (approximately 25°C) and peeled off the glass substrate to obtain a polyamide film. Polyamide films for Examples 2-4 and Comparative Example 1 were synthesized in the same manner as in Example 1, except that the molar ratios of each reacted diamine compound and dicarboxylic acid compound were as shown in Table 1.

[0204] The measurement results for the obtained polyamide film are shown in Table 1. [Table 1]

[0205] As shown in Table 1, it can be seen that by combining 2,2'-dimethylbenzidine and 9,9-bis(4-amino-3-fluorophenyl)fluorene as aromatic diamine compounds in the production of polyamide films, a resin film with a YI value of 10.0 or less can be obtained even with a film thickness of 30 μm or more.

[0206] <Examples 5-15, Comparative Examples 2-6: Resin films containing antioxidants> The resins and antioxidants used in Examples 5-15 and Comparative Examples 2-6 are as follows.

[0207] (resin) Polyamide resin 1 (PA1): A polyamide resin synthesized using 2,2'-dimethylbenzidine as the aromatic diamine compound and 4,4'-oxybis(benzoyl chloride) (DEDC) as the aromatic dicarboxylic acid compound, synthesized by the method described below.

[0208] (Antioxidant) • Lactone-based antioxidant: Manufactured by BASF Japan Ltd., product name "Irganox HP-136", referred to as "HP-136" in the table. [ka] • Phenolic antioxidant: 2,6-di-tert-butyl-p-cresol (BHT) (manufactured by Tokyo Chemical Industry Co., Ltd.), represented as "BHT" in the table. • Phenolic antioxidant: Manufactured by ADEKA Corporation, product name "ADEKA Stab AO-30", represented as "AO-30" in the table, not applicable to any specific phenolic antioxidant. [ka] • Phenolic antioxidant: Manufactured by ADEKA Corporation, product name "ADEKA Stab AO-40", referred to as "AO-40" in the table, not applicable to any specific phenolic antioxidant. [ka] · Phenolic antioxidant: Manufactured by ADEKA Corporation, product name "ADEKA STAB AO-50", represented as "AO-50" in the table

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[0209] <Synthesis of Polyamide Resin 1> A 100 mL reactor was packed with 66.7 g of N,N-dimethylacetamide (DMAc), and 4.31 g (20.3 mmol) of 2,2'-dimethylbenzidine and 3.22 g (44.6 mmol) of 1,2-butylene oxide were added. Next, 5.96 g (20.1 mmol) of 4,4'-oxybis(benzoyl chloride) (DEDC) was added to this 2,2'-dimethylbenzidine solution, and the mixture was stirred at 30°C for 2 hours to allow it to react. Subsequently, 0.16 g (2.0 mmol) of acetyl chloride was added to this solution, and the mixture was stirred at 30°C for 30 minutes to obtain a solution containing a polymer having an amide structure (polyamide resin 1). The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained polyamide resin 1 were 42,092 and 163,454, respectively.

[0210] <Film Production> For Example 5, the film was prepared using the following method. To 40 g of a solution of resin (polyamide resin 1) (solid content concentration 11% by mass), 0.022 g of antioxidant and 0.17 g of dispersant (phenylphosphonic acid) were dissolved. Then, 6.6 g of alumina slurry (alumina filler (pseudo-boehmite filler, manufactured by Kawaken Fine Chemicals) with a fiber diameter of 5 nm and a fiber length of 800 nm dispersed in N,N-dimethylacetamide (DMAc), solid content concentration 10% by mass) was added, and the slurry was then dispersed and homogenized to prepare a solution for film manufacturing. Next, this solution was applied to a glass substrate using a table coater (AFA-standard, manufactured by Cortec Co., Ltd.) to a thickness of approximately 50 μm after drying. Then, it was dried using 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 under an atmospheric environment, with drying at 120°C for 20 minutes followed by drying at 220°C for 20 minutes. Except for changing the type and amount of antioxidants as shown in Table 2, polyamide films for Examples 6-15 and Comparative Examples 2-6 were prepared in the same manner as in Example 5.

[0211] The film was measured using the measurement method described above. The results are shown in Table 2.

[0212] [Table 2]

[0213] As shown in Table 2, it can be seen that by using antioxidants selected from lactone-based antioxidants, specific phenol-based antioxidants, and specific phosphite-based antioxidants in the production of polyamide films, it is possible to obtain resin films with a YI value of 10.0 or less, even with a film thickness of 30 μm or more.

[0214] <Examples 16-22: Films using phosphorus compounds> The resins and antioxidants used in Examples 16-22 were the same as described above, and the phosphorus compounds were as follows.

[0215] (Phosphorus compounds) Triethyl phosphate (TEP): Manufactured by Tokyo Chemical Industry Co., Ltd., Molecular weight: 182 Dimethyl phenylphosphonate (PPADM): Manufactured by Tokyo Chemical Industry Co., Ltd., Molecular weight: 186

[0216] <Film Production> For Example 16, the film was prepared using the following method. To 40 g of a solution of resin (polyamide resin 1), 0.022 g of antioxidant, 0.17 g of dispersant (phenylphosphonic acid), and 0.88 g of phosphorus compound (TEP) were dissolved. Then, 6.6 g of alumina slurry (alumina filler (pseudo-boehmite filler, manufactured by Kawaken Fine Chemicals) with a fiber diameter of 5 nm and a fiber length of 800 nm dispersed in N,N-dimethylacetamide (DMAc), solid content concentration 10% by mass) was added, and the mixture was then dispersed and homogenized to prepare a solution for film manufacturing. Next, this solution was applied to a glass substrate using a table coater (AFA-standard, manufactured by Cortec Co., Ltd.) to a thickness of approximately 50 μm after drying. Then, it was dried using 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 under an atmospheric environment, with 120°C for 20 minutes followed by 220°C for 20 minutes. Polyamide films of Examples 17-21 were prepared in the same manner as in Example 16, except that the composition was changed as shown in Table 3. Furthermore, the polyamide film of Example 22 was prepared in the same manner as in Example 16, except that the composition was changed to that shown in Table 3 and the film was coated to a thickness of approximately 85 μm after drying.

[0217] The film was measured using the measurement method described above. The results are shown in Table 3.

[0218] [Table 3]

[0219] As shown in Table 3, it can be seen that in the production of polyamide films, the YI value of resin films with a film thickness of 30 μm or more can be further improved by using phosphorus compounds in combination with antioxidants selected from lactone-based antioxidants, specific phenol-based antioxidants, and specific phosphite-based antioxidants.

[0220] <Examples 23-26: Polyamide film> The resins used in Examples 23-26 are as follows:

[0221] <Synthesis of Polyamide Resin 2> 40.4 g of N,N-dimethylacetamide (DMAc) was packed into a 100 mL reactor, and 4.02 g (10.7 mmol) of 9,9-bis(4-amino-3-methylphenyl)fluorene and 1.69 g (23.5 mmol) of 1,2-butylene oxide were added. Next, 3.15 g (10.7 mmol) of 4,4'-oxybis(benzoyl chloride) (DEDC) was added to this 9,9-bis(4-amino-3-methylphenyl)fluorene solution, and the mixture was stirred at 30°C for 2 hours to allow the reaction to proceed. Subsequently, 0.096 g (1.1 mmol) of acetyl chloride was added to this solution, and the mixture was stirred at 30°C for 30 minutes to obtain a solution containing a polymer having an amide structure (polyamide resin 2). The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained polyamide resin 2 were 53,055 and 198,744, respectively.

[0222] (Preparation of polyamide film in Example 23) Next, the solution containing the obtained polyamide resin 2 (coating liquid) was coated onto a glass substrate using a bar coater to a target thickness of 55 μm after drying. Then, primary drying was performed in a hot air circulation dryer (DH612, manufactured by Yamato Scientific Co., Ltd.) under atmospheric conditions at 120°C for 20 minutes, followed by secondary drying at 220°C for 20 minutes. After drying, the film was allowed to cool at room temperature (approximately 25°C) and peeled off the glass substrate to obtain the polyamide film of Example 23.

[0223] (Preparation of polyamide film in Example 24) 40 g of the solution containing the obtained polyamide resin 2 (coating solution, solid content concentration 13% by mass) was mixed with 0.026 g of BHT and 1.0 g of TEP, and the homogenized solution was coated onto a glass substrate using a bar coater to a target thickness of 55 μm after drying. Then, primary drying was performed in a hot air circulation dryer (DH612, Yamato Scientific Co., Ltd.) under atmospheric conditions at 120°C for 20 minutes, followed by secondary drying at 220°C for 20 minutes. After drying, the film was allowed to cool at room temperature (approximately 25°C) and peeled off the glass substrate to obtain the polyamide film of Example 24.

[0224] (Preparation of polyamide film in Example 25) To 40 g of the solution (coating solution) containing the obtained polyamide resin 2, 0.20 g of dispersant (phenylphosphonic acid) was dissolved, and then 7.8 g of alumina slurry (alumina filler (pseudo-boehmite filler, manufactured by Kawaken Fine Chemicals) with a fiber diameter of 5 nm and a fiber length of 800 nm dispersed in N,N-dimethylacetamide (DMAc), solid content concentration 10% by mass) was added. The slurry was then dispersed and homogenized to prepare a solution for film manufacturing. Next, this solution was applied to a glass substrate using a table coater (AFA-standard, manufactured by Cortec) to a thickness of approximately 50 μm after drying. Then, it was dried using an oven (Fine Oven DH612, manufactured by Yamato Scientific Co., Ltd.) to form the polyamide film of Example 25. The drying conditions were a two-stage drying process under an atmospheric environment, with drying at 120°C for 20 minutes followed by drying at 220°C for 20 minutes.

[0225] (Preparation of polyamide film in Example 26) To 40 g of the solution (coating solution) containing the obtained polyamide resin 2, 0.026 g of BHT, 1.0 g of TEP, and 0.20 g of a dispersant (phenylphosphonic acid) were dissolved. Then, 7.8 g of alumina slurry (alumina filler (pseudo-boehmite filler, manufactured by Kawaken Fine Chemicals) with a fiber diameter of 5 nm and a fiber length of 800 nm dispersed in N,N-dimethylacetamide (DMAc), solid content concentration 10% by mass) was added, and the mixture was then dispersed and homogenized to prepare a solution for film manufacturing. Next, this solution was applied to a glass substrate using a table coater (AFA-standard, manufactured by Cortec) to a thickness of approximately 50 μm after drying. Then, it was dried using an oven (Fine Oven DH612, manufactured by Yamato Scientific Co., Ltd.) to form the polyamide film of Example 26. The drying conditions were a two-stage drying process under an atmospheric environment, with drying at 120°C for 20 minutes followed by drying at 220°C for 20 minutes.

[0226] The film was measured using the measurement method described above. The results are shown in Table 4. [Table 4]

[0227] As shown in Table 4, it can be seen that by using 9,9-bis(4-amino-3-methylphenyl)fluorene as an aromatic diamine compound in the production of polyamide films, it is possible to obtain resin films with a YI value of 10.0 or less, even with a film thickness of 30 μm or more. Furthermore, it can be seen that the YI value of resin films with a film thickness of 30 μm or more can be further improved by using specific phenolic antioxidants or phosphorus compounds in combination.

[0228] <Examples 27-30: Polyamide-imide film> The resins used in Examples 27-30 are as follows:

[0229] <Synthesis of polyamide-imide resin> 62.4 g of N,N-dimethylacetamide (DMAc) was packed into a 100 mL reactor, and 2.74 g (12.9 mmol) of 2,2'-dimethylbenzidine was added. Next, 2.88 g (5.5 mmol) of 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) was added to this 2,2'-dimethylbenzidine solution, and the mixture was stirred at 30°C for 2 hours to obtain a solution containing a polymer having an imide precursor structure. Subsequently, 1.17 g (16.2 mmol) of 1,2-butylene oxide was added to this solution. Next, 2.14 g (7.3 mmol) of 4,4'-oxybis(benzoyl chloride) (DEDC) was added, and the mixture was stirred at 30°C for 1.5 hours to obtain a solution containing a copolymer having both an imide precursor structure and an amide structure. Subsequently, 4.90 g of pyridine and 6.34 g of acetic anhydride 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 the mixture was stirred until homogeneous. This solution was then gradually added to a container with 4 L of methanol to allow precipitation. Next, the precipitated solid was filtered and pulverized, and then dried under vacuum at 80°C for 18 hours to obtain 8.0 g of solid powder polyamide-imide copolymer (polyamide-imide resin). The number-average molecular weight (Mn) and weight-average molecular weight (Mw) of the obtained polyamide-imide resin were 47,578 and 181,099, respectively.

[0230] (Preparation of polyamide-imide films in Examples 27-30) The polyamide-imide films of Examples 27 to 30 were formed using the same composition and method as in Examples 23 to 26, except that a solution or powder of polyamide-imide resin was used instead of polyamide resin 2.

[0231] The film was measured using the measurement method described above. The results are shown in Table 5. [Table 5]

[0232] As shown in Table 5, by using a polyamide-imide resin corresponding to a specific resin, it is possible to obtain a resin film with a YI value of 10.0 or less, even with a film thickness of 30 μm or more.

[0233] <Example 31: Polyamide film> The polyamide film of Example 31 was prepared in the same manner as in Comparative Example 1, except that secondary drying was performed at 220°C for 20 minutes under a nitrogen atmosphere. The film was measured using the measurement method described above. The results are shown in Table 6.

[0234] [Table 6]

[0235] As shown in Table 6, in the production of polyamide films using a specific resin, it can be obtained with a YI value of 10.0 or less even when the film thickness is 30 μm or more, by performing secondary drying under a nitrogen atmosphere. [Industrial applicability]

[0236] According to the present invention, it is possible to provide a resin film that has good colorlessness even when the film thickness is increased, using monomers that do not fall under the category of PFAS. Furthermore, according to the present invention, a flexible display using such a resin film can be provided.

Claims

1. A resin film made of a resin composition, having a film thickness of 30 μm or more, The resin composition comprises one or more resins selected from aromatic polyimide resins, aromatic polyamideimide resins, and aromatic polyamide resins, wherein the resin has a structure in which a carbon atom having a hydrogen atom is directly bonded to a benzene ring. The yellow index value is 10.0 or less. Resin film.

2. The resin film according to claim 1, wherein the resin does not have a perfluoroalkyl portion and a polyfluoroalkyl portion.

3. The resin film according to claim 1, wherein a nitrogen atom derived from an amino group is bonded to a benzene ring to which the carbon atom having the hydrogen atom is directly bonded.

4. The resin film according to claim 3, wherein the resin has a residue derived from an aromatic diamine compound represented by the following formula (1). 【Chemistry 1】 During the ceremony, n is either 0 or 1, R １ and R ２ are each independently, -CH ３ , -CH ２ R ａ , -CHR ｂ R ｃ , -CR ｄ R ｅ R ｆ or a halogen atom, R ａ ~R ｅ These are, independently, an alkyl group, an alkenyl group, and an aryl group. X is a single bond, -CH ２ -----CHR ｆ -, -CR ｇ R ｈ -, -O-, -S-, -S (=O) ２ , -C(=O)O-, -C(=O)-NH-, or -C(=O)-, R ｆ ~R ｈ Each of these is independently an alkyl group, an alkenyl group, or an aryl group, or R ｇ and R ｈ These may also form a carbon ring together with the carbon atoms to which they are bonded. p represents an integer from 0 to 4. q represents an integer from 0 to 4. If n is 0, p is an integer greater than or equal to 1, and there is at least one R １ ga-CH ３ ien-CH ２ R ａ or -CHR ｂ R ｃ And, If n is 1, then at least one of the following conditions (i) to (iii) is met. (i) X is -CH ２ - or - CHR ｆ - is (ii) p is an integer greater than or equal to 1 and at least one R １ ga-CH ３ ien-CH ２ R ａ or -CHR ｂ R ｃ That is (iii) q is an integer greater than or equal to 1 and at least one R ２ ga-CH ３ ien-CH ２ R ａ or -CHR ｂ R ｃ That is the case.

5. The resin film according to claim 1, wherein the resin composition further comprises an antioxidant.

6. The resin film according to claim 1, wherein the resin composition further comprises one or more selected from phosphate ester compounds and phosphonic acid compounds.

7. The resin film according to claim 1, wherein the resin composition further comprises a filler.

8. A flexible display comprising a resin film according to any one of claims 1 to 7.

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