WO2018135432A1

WO2018135432A1 - Film, resin composition, and production method for polyamide-imide resin

Info

Publication number: WO2018135432A1
Application number: PCT/JP2018/000805
Authority: WO
Inventors: 皓史宮本; 希望増井; 将金坂; 池内　淳一
Original assignee: 住友化学株式会社
Priority date: 2017-01-20
Filing date: 2018-01-15
Publication date: 2018-07-26
Also published as: TW201831565A; KR20180094840A; JP2019104939A; JP6675509B2; JP7118651B2; KR101952823B1; JP2018119141A; KR20180133564A; KR20200038329A; CN110191909B; CN110191909A

Abstract

The present invention addresses the problem of providing a film that is suitable for use as a front surface plate for a flexible display or the like, includes a polyamide-imide resin that is highly imidized, and has high surface hardness. The present invention provides a film that includes a polyamide-imide resin A that: has at least a structural unit derived from a diamine, a structural unit derived from a dicarboxylic acid, and a structural unit derived from a tetracarboxylic acid dianhydride; and, as measured by two-dimensional NMR, is at least 95% imidized.

Description

Film, resin composition and method for producing polyamideimide resin

The present invention relates to a film containing a polyamideimide resin, a resin composition containing a polyamideimide resin, and a method for producing a polyamideimide resin.

Currently, image display devices such as liquid crystal display devices and organic EL display devices are widely used not only for televisions but also for various applications such as mobile phones and smart watches. With the expansion of such applications, an image display device (flexible display) having flexible characteristics is required. The image display apparatus includes a display element such as a liquid crystal display element or an organic EL display element, and other constituent members such as a polarizing plate, a retardation plate, and a front plate. In order to achieve a flexible display, all these components need to be flexible.

Until now, glass has been used as the front plate. Glass is highly transparent and can exhibit high hardness depending on the type of glass, but it is very rigid and easily broken, making it difficult to use as a front plate material for flexible displays.

Therefore, the use of polymer materials as a substitute for glass is being studied. Since the front plate made of a polymer material is easy to exhibit flexible characteristics, it can be expected to be used for various applications. Various resins can be used as the flexible resin, and one of them is a polyamideimide resin. Polyamideimide resins are used in various applications from the viewpoints of transparency and heat resistance, and various methods for their production have been studied.

For example, Patent Document 1 discloses a unit structure derived from TFDB (2,2′-bistrifluoromethyl-4,4′-biphenyldiamine), 6FDA (4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride. And a copolymerized polyamideimide film comprising a resin in which a unit structure derived from TPC (tetrephthaloyl chloride; 1,4-benzenedicarbonyl chloride) is copolymerized.
Patent Document 2 describes a copolymerized polyamide film having excellent mechanical properties such as pencil hardness.

Special table 2015-521686 gazette Special table 2014-528490 gazette

Conventionally, in a film containing a polyamide-imide resin used as a front plate, it is required to express a high surface hardness of the film with high transparency, but the evaluation result of the surface hardness depending on the film production method and the measurement conditions of the film There were problems such as greatly different.

For example, the film described in Patent Document 1 has an average transmittance of 89% or more at a wavelength of 380 to 780 nm, but it is not clear whether the film has a sufficiently high surface hardness. Moreover, there is no suggestion about a form suitable for the expression of high surface hardness. Patent Document 2 describes that the film has a surface pencil hardness of 3H or more, but when the pencil hardness is evaluated, the result may vary depending on the illuminance conditions used.

Therefore, an object of the present invention is to provide a film having a high surface hardness, including a polyamideimide resin having a high imidization ratio, which is particularly suitably used as a front plate for a flexible display or the like.

In order to solve the above-mentioned problems, the present inventors diligently studied various characteristics of the polyamideimide resin by paying attention to the imidization ratio of the polyamideimide resin and the surface hardness of the obtained film. As a result, it was found that the surface hardness of the film can be increased by using a polyamideimide resin satisfying specific requirements, and the present invention has been completed.

That is, the present invention includes the following preferred embodiments.
[1] It has at least a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride, and an imidation ratio of 95% or more as measured by two-dimensional NMR A film comprising polyamideimide resin A having
[2] The diamine has the formula (3):

[In Formula (3), X is Formula (3e '):

[In the formula (3e ′), R ¹⁰ to R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and are included in R ¹⁰ to R ^17. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ] Is represented. ]
The film according to [1] above, comprising at least one compound represented by the formula:
[3] The dicarboxylic acid has the formula (2):

[In Formula (2), Z represents Formula (2a) or (2b):

Wherein (2a) and Formula (2b), ^{U 1} represents a single _{_{_{bond, -O -, - CH 2 -}}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) _{_{_{_{2 -, - C (CF 3}}}} ) 2 -, - Ar -, - SO 2 -, - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar-, —Ar—C (CH ₃ ) ₂ —Ar— or Ar—SO ₂ —Ar— is represented, and * represents a bond. And B ¹ and B ² each independently represent OH or a halogen atom. ]
The film according to the above [1] or [2], comprising at least one compound represented by:
[4] The tetracarboxylic dianhydride has the formula (4):

[In Formula (4), Y represents Formula (4g):

[In Formula (4g), W ¹ represents a single bond, —C (CH ₃ ) ₂ — or C (CF ₃ ) ₂ —, and * represents a bond. ] Is represented. ]
The film according to any one of [1] to [3], comprising at least one compound represented by the formula:
[5] The film according to any one of [1] to [4], wherein the polyamideimide resin A contains a fluorine atom.
[6] The film according to any one of [1] to [5], having a YI of 3 or less.
[7] The film according to any one of [1] to [6], which has a pencil hardness of 3B or more as measured in accordance with ASTM D 3363 under an illumination condition of 4000 lux.
[8] It has a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride, and has an imidization ratio of 60% or more as measured by two-dimensional NMR. A resin composition comprising at least a polyamideimide resin B and a solvent.
[9] The diamine has the formula (3):

[In Formula (3), X is Formula (3e '):

[In the formula (3e ′), R ¹⁰ to R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and are included in R ¹⁰ to R ^17. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ] Is represented. ]
The resin composition as described in [8] above, comprising at least one compound represented by the formula:
[10] The dicarboxylic acid has the formula (2):

[In the formula (2), Z represents the following formula (2a) or formula (2b):

Wherein (2a) and Formula (2b), ^{U 1} represents a single _{_{_{bond, -O -, - CH 2 -}}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) _{_{_{_{2 -, - C (CF 3}}}} ) 2 -, - Ar -, - SO 2 -, - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar-, —Ar—C (CH ₃ ) ₂ —Ar— or Ar—SO ₂ —Ar— is represented, and * represents a bond. And B ¹ and B ² each independently represent OH or a halogen atom. ]
The resin composition according to the above [8] or [9], comprising at least one compound represented by:
[11] The tetracarboxylic dianhydride has the formula (4):

[In formula (4), Y represents the following formula (4g):

[In Formula (4g), W ¹ represents a single bond, —C (CH ₃ ) ₂ — or C (CF ₃ ) ₂ —, and * represents a bond. ] Is represented. ]
The resin composition according to any one of [8] to [10], comprising at least one compound represented by the formula:
[12] The resin composition according to any one of [8] to [11], wherein the polyamideimide resin B contains a fluorine atom.
[13] A film obtained by drying a coating film of the resin composition according to any one of [8] to [12].
[14] (1) A step of copolymerizing diamine, dicarboxylic acid, and tetracarboxylic dianhydride in a solvent to obtain a polyamideimide resin precursor, and
(2) A method for producing a polyamideimide resin, comprising at least a step of adding a dehydrating agent and a tertiary amine to a solution containing at least a polyamideimide resin precursor and heating at a temperature of 70 to 120 ° C. When the amount of water in the solvent at the start of (1) is w (ppm) and the heating time in step (2) is t (minutes), w and t are the following formulas:

Satisfying the manufacturing method.
[15] The production according to [14], wherein the molar amount of the dehydrating agent added in the step (2) is at least twice the molar amount of the tetracarboxylic dianhydride added in the step (1). Method.

According to the present invention, it is possible to obtain a film having a high surface hardness, which includes a polyamideimide resin having a high imidization ratio and is preferably used as a front plate or the like in an image display device or the like.

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiment described here, and various modifications can be made without departing from the spirit of the present invention.

The film of the present invention contains a polyamideimide resin A having an imidization ratio of 95% or more as measured by two-dimensional NMR. When the imidization ratio of the polyamide-imide resin A is lower than 95%, the surface hardness of the film containing the polyamide-imide resin cannot be sufficiently increased because the polyamide-imide resin A tends to be an excessively flexible primary structure. From the viewpoint of the stability of the polyamideimide varnish, the imidization ratio of the polyamideimide resin A is preferably 97% or more, more preferably 98% or more, and even more preferably 99% or more. The higher the imidization rate, the better. The upper limit is not particularly limited, and it may be 100% or less. As a method for adjusting the imidation ratio of the polyamide-imide resin A to the above range, for example, after producing a film using a polyamide resin composition described later, the method for producing by imidization, the production method described later The method etc. which manufacture a film using the composition containing the prepared polyamide imide resin are mentioned.

The imidation ratio of the polyamideimide resin A is the ratio of the number of moles of imide bonds in the polyamideimide resin A to the value twice the number of moles of the structural unit derived from the tetracarboxylic dianhydride in the polyamideimide resin A. In this specification, it is measured by two-dimensional NMR. Conventionally, the measurement of the imidization ratio of a polyamide-imide resin has often been performed using an infrared spectrum. In this method, a resin containing an imide is heated as described in JP-A-2004-338160. However, it is necessary to measure a fully imidized resin. However, in order to sufficiently imidize, it is necessary to heat at a high temperature, and there may be an error because a decomposition reaction of the resin may occur simultaneously in the heating process, and the imidation rate can be accurately measured. There wasn't. The present inventors have studied to measure the imidization ratio of the polyamide-imide resin with high accuracy using two-dimensional NMR, and as a result, a polyamide having a predetermined imidization ratio measured using two-dimensional NMR. It has been found that a film containing imide resin A achieves a high surface hardness. The imidization ratio of the polyamideimide resin A can be measured using two-dimensional NMR using a predetermined solution obtained by dissolving the film in deuterated dimethyl sulfoxide (DMSO-d6). The details of the two-dimensional NMR measurement conditions are as shown in the examples.

The pencil hardness (surface hardness) of the film of the present invention is preferably 3B or more, more preferably 2B or more, still more preferably B or more, particularly preferably HB or more, as measured according to ASTM D 3363 under an illumination condition of 4000 lux. Very preferably H or higher, most preferably 2H or higher. When the film of the present invention has a pencil hardness equal to or higher than the above lower limit, when used as a front plate (window film) of an image display device, it is easy to suppress scratches on the surface of the image display device, and the film shrinks and expands. It is preferable because it is easy to prevent. The upper limit of the pencil hardness of the film of the present invention is not particularly limited. The pencil hardness is measured according to JIS K5600-5-4: 1999. Specifically, measurement is performed at a load of 100 g and a scanning speed of 60 mm / min, and evaluation is performed under an illuminance condition of a light amount of 4000 lux. In addition, when evaluating pencil hardness, a result may change with the illumination intensity conditions to be used. Specifically, compared with the pencil hardness measured and evaluated under the illuminance condition of 4000 lux, the pencil hardness measured and measured under the lower illuminance condition is As a result of making it difficult to see scratches on the film, there is a high possibility that a higher pencil hardness than actual will be obtained. Therefore, the pencil hardness in the present specification is a value obtained by evaluating under an illuminance condition of a light amount of 4000 lux.

The YI value of the film of the present invention is preferably 3.5 or less, more preferably 3.0 or less, and even more preferably 2.5 or less. When the YI value is not more than the above upper limit, the visibility of the film can be further increased. Note that the lower limit of the YI value is not particularly limited, and may be usually 0 or more. The YI value represents the yellowness of the film (Yellow Index: YI value). According to JIS K 7373: 2006, the spectrophotometer (UV-Vis near-infrared spectrophotometer V-670 manufactured by JASCO Corporation) was used. ). Specifically, the tristimulus values (X, Y, Z) obtained by measuring the transmittance with respect to light of 300 to 800 nm are calculated based on the following formula. For the measurement, for example, a film having a thickness of 50 to 55 μm can be used. The thickness of the film of the present invention is not particularly limited as long as the YI value is in the above range, but is preferably within the above range in the thickness range described below.

The thickness of the film of the present invention is preferably 20 μm or more, more preferably 30 μm or more, and still more preferably 40 μm or more, from the viewpoint that the pencil hardness also affects the film thickness.
The thickness of the film of the present invention is preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 100 μm or less from the viewpoint of bending resistance. The thickness is measured using a contact-type digimatic indicator.

The total light transmittance (Tt) of the film of the present invention is preferably 70% or more, more preferably 80% or more, still more preferably 85% or more, particularly preferably 90, as measured in accordance with JIS K 7105: 1981. % Or more. When the total light transmittance is not less than the above lower limit, the visibility when the film of the present invention is incorporated in an image display device can be easily improved. In addition, the upper limit of the total light transmittance of the film of the present invention is usually 100% or less. The total light transmittance is measured using, for example, a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K 7105: 1981. For the measurement, for example, a film having a thickness of 50 to 55 μm can be used. In addition, if the film of this invention has a total light transmittance in the said range, the thickness of a film will not be specifically limited, However, It is preferable to exist in the said range in the said thickness range.

The elastic modulus of the film of the present invention is preferably 5.9 GPa or less, more preferably 5.5 GPa or less, still more preferably 5.2 GPa or less, particularly preferably 5.0 GPa or less, most preferably, from the viewpoint of film flexibility. Is 4.5 GPa or less. When the elastic modulus is not more than the above upper limit, when the flexible display is bent, it is easy to suppress damage to other members due to the film. In addition, although the minimum of the elasticity modulus of the film of this invention is not specifically limited, Usually, it is 2.0 GPa or more. For example, the elastic modulus was measured from the slope of an SS curve measured using an autograph AG-IS manufactured by Shimadzu Corporation with a 10 mm wide test piece at a distance between chucks of 500 mm and a tensile speed of 20 mm / min. Can be measured.

The number of reciprocal folding of the film of the present invention is preferably measured 10,000 times from the viewpoint of bending resistance of the film until the film breaks under the conditions of R = 1 mm, 135 °, load 0.75 kgf, and speed 175 cpm. More preferably, it is 20,000 times or more, more preferably 30,000 times or more, particularly preferably 40,000 times or more, and most preferably 50,000 times or more. When the number of reciprocal folding of the film of the present invention is equal to or more than the above lower limit, weaving that may occur when the film is bent is easily suppressed. The upper limit of the number of reciprocal folds of the film of the present invention is not particularly limited, but it is sufficiently practical as long as the film can be normally bent about 1,000,000 times or less. The number of reciprocal bendings can be obtained by using, for example, a test piece cut out from a film having a thickness of 50 μm and a width of 10 mm using a MIT folding fatigue tester (model 0530) manufactured by Toyo Seiki Seisakusho.

The polyamideimide resin A contained in the film of the present invention has at least a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride.

The polyamideimide resin A contained in the film of the present invention has a structural unit derived from diamine. Examples of the diamine include a compound represented by the formula (3). Polyamideimide resin A may have a structural unit derived from one kind of diamine, or may have a structural unit derived from two or more kinds of diamines.

[In formula (3), X represents a divalent organic group. ]

In a preferred embodiment in which the polyamideimide resin A contained in the film of the present invention has a constitutional unit derived from the diamine represented by the formula (3), the amount of the constitutional unit is the total constitution contained in the polyamideimide resin A. Based on the unit, it is preferably 47.5 mol% or more, more preferably 49.0 mol% or more, and further preferably 49.5 mol% or more. When the amount of the structural unit derived from the diamine represented by the formula (3) is not less than the above lower limit, it is easy to obtain a high molecular weight polyamideimide resin and easily develop high surface hardness. Further, the amount of the structural unit derived from the diamine represented by the formula (3) is preferably 50.5 mol% or less, more preferably 50.0 mol, based on all the structural units contained in the polyamideimide resin A. % Or less, more preferably 49.99 mol% or less. When the amount of the structural unit derived from the diamine represented by the formula (3) is not more than the above upper limit, high transparency and low yellowness are likely to be exhibited.

X in the formula (3) represents a divalent organic group, and preferably represents an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of the divalent organic group include groups represented by formulas (3a) to (3i); a hydrogen atom in the groups represented by formulas (3a) to (3i) is a methyl group, a fluoro group, or a chloro group. Or a group substituted with a trifluoromethyl group; and a divalent chain hydrocarbon group having 6 or less carbon atoms.

[In the formulas (3a) to (3i),
* Represents a bond,
V ¹ ~ ^{V 3} are each independently a single _{_{bond, -O -, - S -,}} - CH 2 -, - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) _2- , -C (CF ₃ ) _2- , -SO ₂ -or CO- is represented. ]
In one example, V ¹ and V ³ are a single bond, —O— or S—, and V ² is —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —. Or SO ₂ —. The bonding position of V ¹ and V ² with respect to each ring and the bonding position of V ² and V ³ with respect to each ring are preferably in the meta position or the para position with respect to each ring, respectively. More preferably.

Among the groups represented by the formulas (3a) to (3i), groups represented by the formulas (3d) to (3h) are preferable from the viewpoint of the surface hardness and flexibility of the film of the present invention. The groups represented by 3e) to formula (3g) are more preferable. V ¹ to V ³ are each independently preferably a single bond, —O— or S— from the viewpoint of the surface hardness and flexibility of the film of the present invention, and preferably a single bond or O—. It is more preferable.

Specific examples of the diamine represented by the formula (3) include aliphatic diamines, aromatic diamines, and mixtures thereof. In the present embodiment, the “aromatic diamine” represents a diamine in which an amino group is directly bonded to an aromatic ring, and an aliphatic group or other substituent may be included in a part of the structure. The aromatic ring may be a single ring or a condensed ring, and examples thereof include, but are not limited to, a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring. Among these, a benzene ring is preferable. The “aliphatic diamine” refers to a diamine in which an amino group is directly bonded to an aliphatic group, and an aromatic ring or other substituent may be included in a part of the structure.

Examples of the aliphatic diamine include acyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, norbornane diamine, and 4,4 ′. -Cyclic aliphatic diamines such as diaminodicyclohexylmethane. These can be used alone or in combination of two or more.

Examples of aromatic diamines include p-phenylenediamine, m-phenylenediamine, 2,4-toluenediamine, m-xylylenediamine, p-xylylenediamine, 1,5-diaminonaphthalene, and 2,6-diamino. An aromatic diamine having one aromatic ring, such as naphthalene; 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether (ODA), 3,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenyl sulfone, 1,4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, 4,4 ' Diaminodiphenylsulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine (MB), 2,2′-bis (trifluoromethyl) benzidine (TFMB), 4,4′- Bis (4-aminophenoxy) biphenyl, 9,9-bis (4-aminophenyl) fluorene, 9,9-bis (4-amino-3-methylphenyl) fluorene, 9,9-bis (4-amino-3) Fragrance having two or more aromatic rings, such as -chlorophenyl) fluorene and 9,9-bis (4-amino-3-fluorophenyl) fluorene Diamine and the like. These can be used alone or in combination of two or more.

As the aromatic diamine, preferably 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 3,3′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3,3′-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (Trifluoromethyl) benzidine, 4,4'-bis (4-aminophenoxy) biphenyl More preferably 4,4′-diaminodiphenylmethane, 4,4′-diaminodiphenylpropane, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenylsulfone, 1,4-bis (4-aminophenoxy) Benzene, bis [4- (4-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2′-dimethylbenzidine, 2,2′-bis (tri Fluoromethyl) benzidine, 4,4′-bis (4-aminophenoxy) biphenyl. These can be used alone or in combination of two or more.

Among the diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure may be used from the viewpoints of surface hardness, flexibility, bending resistance, transparency and yellowness of the film of the present invention. Preferably, selected from the group consisting of 2,2′-dimethylbenzidine, 2,2′-bis (trifluoromethyl) benzidine, 4,4′-bis (4-aminophenoxy) biphenyl, and 4,4′-diaminodiphenyl ether It is more preferable to use one or more, and it is even more preferable to use 2,2′-bis (trifluoromethyl) benzidine.

From the viewpoint of easily increasing the surface hardness and transparency of the film of the present invention, the polyamideimide resin A has at least a structural unit derived from a diamine in which X in the formula (3) is represented by the formula (3e ′). preferable.

[In the formula (3e ′), R ¹⁰ to R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and are included in R ¹⁰ to R ^17. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ]

In the formula (3e ′), R ¹⁰ to R ¹⁷ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, preferably a hydrogen atom or 1 to 6 represents an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein the hydrogen atoms contained in R ¹⁰ to R ¹⁷ are each independently substituted with a halogen atom. Also good. From the viewpoint of the surface hardness, flexibility and transparency of the film of the present invention, R ¹⁰ to R ¹⁷ are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group. Particularly preferred are a hydrogen atom or a trifluoromethyl group.

In this embodiment, the polyamideimide resin A is a diamine (2,2′-bis (trifluoromethyl) benzidine, also referred to as TFMB) in which X in the formula (3) is represented by the formula (3e ″). It is more preferable to have at least the derived structural unit. In this case, the film of the present invention has high transparency, and at the same time, the polyamideimide resin A has a skeleton containing a fluorine element, so that the solubility of the polyamideimide resin in the solvent is improved, and the film of the present invention is Since the viscosity of the polyamidoimide varnish used when producing can be suppressed low, it becomes easy to manufacture the film of this invention.

[In the formula (3e ″), * represents a bond. ]

When the polyamideimide resin A has a structural unit derived from two or more kinds of diamines, X in the formula (3) is derived from the diamine represented by the formula (3e ′), preferably the formula (3e ″). The amount of the unit is preferably 30 mol% or more based on the entire constitutional unit derived from the diamine contained in the polyamideimide resin A, from the viewpoint of improving the transparency of the film of the present invention and the ease of production. Preferably it is 50 mol% or more, More preferably, it is 70 mol% or more. The upper limit of the amount of the structural unit derived from the diamine in which X in the formula (3) is represented by the formula (3e ′), preferably the formula (3e ″) is not particularly limited, and the diamine contained in the polyamideimide resin A 100 mol% or less should just be based on the whole structural unit derived from. The ratio of the structural unit derived from the diamine in which X in the formula (3) is represented by the formula (3e ′) or (3e ″) can be measured using, for example, two-dimensional NMR, or charged with raw materials It can also be calculated from the ratio.

The polyamideimide resin A contained in the film of the present invention has a structural unit derived from dicarboxylic acid. When the polyamideimide resin A contained in the film of the present invention has a structural unit derived from a dicarboxylic acid, it is replaced with a structural unit derived from a trivalent or higher carboxylic acid such as 1,3,5-benzenetricarboxylic acid. The solubility in the solvent tends to be less likely to decrease. The structural unit derived from dicarboxylic acid is preferably a structural unit derived from dicarboxylic acid dichloride. Examples of the dicarboxylic acid include a compound represented by the formula (2). Polyamideimide resin A may have a structural unit derived from one type of dicarboxylic acid, or may have a structural unit derived from two or more types of dicarboxylic acid.

[In the formula (2), Z represents a divalent organic group, and B ¹ and B ² each independently represent OH or a halogen atom, preferably a chlorine atom. ]

In the polyamideimide resin A, the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is preferably 5 mol% or more, more preferably 15 based on the total structural units contained in the polyamideimide resin A. The mol% or more, more preferably 20 mol% or more. When the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is not less than the above lower limit, high surface hardness is likely to be exhibited. Further, the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is preferably 45 mol% or less, more preferably 40 mol% or less, based on all the structural units contained in the polyamideimide resin A. More preferably, it is 30 mol% or less. When the amount of the structural unit derived from the dicarboxylic acid represented by the formula (2) is less than or equal to the above upper limit, the film tends to exhibit high flexibility, and thus its bending resistance is easily improved.

Z in the formula (2) represents a divalent organic group, and preferably represents an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Examples of the divalent organic group include groups represented by formula (2a) and formula (2b); a hydrogen atom in the group represented by formula (2a) and formula (2b) is a methyl group, a fluoro group, or a chloro group. Or a group substituted with a trifluoromethyl group; and a divalent chain hydrocarbon group having 6 or less carbon atoms.

[In Formula (2a) and Formula (2b),
* Represents a bond,
U ¹ represents a single _{_{_{bond, -O -, - CH 2 -}}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, _{-Ar -, - SO 2 -,} - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar -, - Ar-C (CH 3) 2 -Ar- Or Ar—SO ₂ —Ar—, preferably a single bond, —O— or —Ar—O—Ar—. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. ]

Specific examples of the dicarboxylic acid represented by the formula (2) include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and related acid chloride compounds, acid anhydrides, and the like. May be. Specific examples include dicarboxylic acid compounds of terephthalic acid; isophthalic acid; naphthalene dicarboxylic acid; 4,4′-biphenyldicarboxylic acid; 3,3′-biphenyldicarboxylic acid; chain hydrocarbon having 8 or less carbon atoms; One benzoic acid is a single bond, —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, —O—, —S—, —NR ⁹ —, —C (= O)-or a compound linked by a phenylene group; and acid chloride compounds thereof. Here, R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom.

The dicarboxylic acid represented by the formula (2) preferably contains at least one selected from terephthalic acid, 4,4′-biphenyldicarboxylic acid, 4,4′-oxybisbenzoic acid, and acid chloride compounds thereof. Is more preferable, and includes at least one selected from the group consisting of terephthaloyl chloride (TPC), 4,4′-biphenyldicarbonyl chloride (BPDOC), and 4,4′-oxybis (benzoyl chloride) (OBBC). More preferably, it contains 4,4′-oxybis (benzoyl chloride) (OBBC).

The polyamideimide resin A preferably has at least a structural unit in which Z in the formula (2) is represented by the formula (1) from the viewpoint of easily increasing the surface hardness and transparency of the film of the present invention.

[In Formula (1), R ¹ to R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, and hydrogen contained in R ¹ to R ⁸ Each atom may be independently substituted with a halogen atom,
Each A independently represents —O—, —S—, —CO— or NR ⁹ —, wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom;
m is an integer from 1 to 4,
* Represents a bond. ]

The symbols in formula (1) will be described below.
A each independently represents —O—, —S—, —CO— or NR ⁹ —, wherein R ⁹ represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. To express. From the viewpoint of the flexibility of the film of the present invention, A preferably represents each independently -O- or S-, more preferably -O-.
R ¹ to R ⁸ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. From the viewpoint of flexibility and surface hardness of the film of the present invention, R ¹ to R ⁸ each independently preferably represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or carbon number. It represents 1 to 3 alkyl groups, and more preferably represents a hydrogen atom. Here, each hydrogen atom contained in R ¹ to R ⁸ may be independently substituted with a halogen atom.
m is an integer in the range of 1 to 4, and is preferably an integer in the range of 1 to 3, more preferably 1 or 2, and even more preferably 1 from the viewpoint of availability of raw materials. When m is within the above range, the availability of the raw materials is good, and the flexibility of the film of the present invention is easily increased.

In a preferred embodiment of the present invention, the formula (1) is a structural unit represented by the formula (1 ′). In this case, the film of the present invention exhibits high surface hardness, and at the same time has a low elastic modulus and tends to have high flexibility.

In a preferred embodiment in which the polyamideimide resin A included in the film of the present invention has a structural unit represented by the formula (1) or the formula (1 ′), the amount of the structural unit is included in the polyamideimide resin A. Based on the total structural units, it is preferably at least 3 mol%, more preferably at least 5 mol%, even more preferably at least 10 mol%, particularly preferably at least 20 mol%. When the amount of the structural unit represented by the formula (1) or the formula (1 ′) is equal to or more than the above lower limit, the resin film tends to exhibit high flexibility, and thus its flex resistance is easily improved. Further, the amount of the structural unit represented by the formula (1) or the formula (1 ′) is preferably 45 mol% or less, more preferably 40 mol% or less, based on all the structural units contained in the polyamideimide resin A. More preferably, it is 30 mol% or less. When the amount of the structural unit represented by the formula (1) or the formula (1 ′) is not more than the above upper limit, the glass transition temperature of the resin film is likely to be improved.

As the polyamide-imide resin A, from the viewpoint of easily increasing the surface hardness, elastic modulus and flexibility of the film of the present invention, Z in the formula (2) is a structural unit derived from a dicarboxylic acid represented by the formula (1). It is preferable to have at least. When the polyamideimide resin has a structural unit derived from two or more kinds of dicarboxylic acids, the amount of the structural unit derived from dicarboxylic acid in which Z in formula (2) is represented by formula (1) is the surface hardness of the film. From the viewpoint of the modulus of elasticity and flexibility, it is preferably 5 mol% or more, more preferably 7 mol% or more, and even more preferably 9 mol%, based on the entire structural unit derived from the dicarboxylic acid contained in the polyamideimide resin A. Above, especially preferably 11 mol% or more. The upper limit of the amount of the structural unit derived from dicarboxylic acid in which Z in formula (2) is represented by formula (1) is not particularly limited, and is based on the entire structural unit derived from dicarboxylic acid contained in polyamideimide resin A. And 100 mol% or less. The ratio of the structural units derived from the dicarboxylic acid in which Z in formula (2) is represented by formula (1) can be measured using, for example, two-dimensional NMR, or can be calculated from the raw material charge ratio. it can.

Polyamideimide resin A contained in the film of the present invention has a structural unit derived from tetracarboxylic dianhydride. Examples of the tetracarboxylic dianhydride include compounds represented by the formula (4). Polyamideimide resin A may have a structural unit derived from one type of tetracarboxylic dianhydride, or may have a structural unit derived from two or more types of tetracarboxylic dianhydride. Good.

[In formula (4), Y represents a tetravalent organic group. ]

In the polyamideimide resin A contained in the film of the present invention, the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is based on all the structural units contained in the polyamideimide resin A. Preferably it is 5 mol% or more, More preferably, it is 10 mol% or more, More preferably, it is 20 mol% or more. When the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is not less than the above lower limit, the proportion of the structural unit derived from the dicarboxylic acid can be suppressed, and Tg is 370 ° C. or lower. It is easy to obtain a polyamideimide resin. Further, the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is preferably 45 mol% or less, more preferably 40 based on the total structural units contained in the polyamideimide resin A. The mol% or less, more preferably 30 mol% or less. When the amount of the structural unit derived from the tetracarboxylic dianhydride represented by the formula (4) is not more than the above upper limit, the proportion of the structural unit derived from the dicarboxylic acid can be increased, and high surface hardness is expressed. Cheap.

Y in Formula (4) represents a tetravalent organic group, and preferably represents an organic group in which a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. The organic group is preferably an organic group which may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. The organic group is preferably a tetravalent organic group having 4 to 40 carbon atoms. The hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. Examples of the tetravalent organic group include groups represented by formulas (4a) to (4j); a hydrogen atom in the groups represented by formulas (4a) to (4j) is a methyl group, a fluoro group, or a chloro group. Or a group substituted with a trifluoromethyl group; and a tetravalent chain hydrocarbon group having 6 or less carbon atoms.

[In the formulas (4a) to (4j),
* Represents a bond,
W ¹ represents a single _{_{_{bond, -O -, - CH 2 -}}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3) 2 -, _{-Ar -, - SO 2 -,} - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar -, - Ar-C (CH 3) 2 -Ar- Or represents Ar—SO ₂ —Ar—. Ar represents an arylene group having 6 to 20 carbon atoms in which a hydrogen atom may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. ]

Among the groups represented by formula (4a) to formula (4j), groups represented by formula (4g), formula (4i) and formula (4j) from the viewpoint of the surface hardness and flexibility of the film of the present invention. Is preferable, and the group represented by the formula (4g) is more preferable. Further, ^{W 1,} from the viewpoint of surface hardness and flexibility of the film of the present invention, a single _{_{bond, -O -, - CH 2 -}} , - CH 2 -CH 2 -, - CH (CH 3) -, - C It is preferably (CH ₃ ) ₂ — or C (CF ₃ ) ₂ —, and is a single bond, —O—, —CH ₂ —, —CH (CH ₃ ) —, —C (CH ₃ ) ₂ — or C More preferably, it is (CF ₃ ) ₂ —, more preferably a single bond, —C (CH ₃ ) ₂ — or C (CF ₃ ) ₂ —, and a single bond, or C (CF ₃ ) ₂ —. It is particularly preferred that

Specific examples of the tetracarboxylic dianhydride represented by the formula (4) include aromatic tetracarboxylic dianhydrides and aliphatic tetracarboxylic dianhydrides. One type of tetracarboxylic dianhydride may be used, or two or more types may be used in combination.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydride, monocyclic aromatic tetracarboxylic dianhydride, and condensed polycyclic aromatic tetra Carboxylic dianhydrides are mentioned. Non-condensed polycyclic aromatic tetracarboxylic dianhydrides include 4,4′-oxydiphthalic dianhydride (OPDA), 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2 , 2 ′, 3,3′-benzophenonetetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA), 2,2 ′, 3,3′-biphenyltetra Carboxylic dianhydride, 3,3 ′, 4,4′-diphenylsulfone tetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis ( 2,3-dicarboxyphenyl) propane dianhydride, 2,2-bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 '-(hexafluoroisopropylidene) diphthalic dianhydride 1,2-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, 1,2-bis (3,4-di Carboxyphenyl) ethane dianhydride, 1,1-bis (3,4-dicarboxyphenyl) ethane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, bis (2,3-dicarboxy Phenyl) methane dianhydride, 4,4 ′-(p-phenylenedioxy) diphthalic dianhydride, 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride. Examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride. Examples of the condensed polycyclic aromatic tetracarboxylic dianhydride include 2,3,6,7-naphthalene tetracarboxylic dianhydride. These can be used alone or in combination of two or more.

Among these, preferably 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride Anhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 2,2', 3,3'-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-diphenyl Sulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, 2,2- Bis (3,4-dicarboxyphenoxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA), 1,2-bis (2,3-dicarboxy) Enyl) 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 ′-( and p-phenylenedioxy) diphthalic dianhydride and 4,4 ′-(m-phenylenedioxy) diphthalic dianhydride. More preferably 4,4′-oxydiphthalic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 4,4 ′-(Hexafluoroisopropylidene) diphthalic dianhydride (6FDA), bis (3,4-dicarboxyphenyl) methane dianhydride and 4,4 ′-(p-phenylenedioxy) diphthalic acid Anhydrides are mentioned. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydrides. The cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. 1, 2,3,4-cyclobutanetetracarboxylic dianhydride, cycloalkanetetracarboxylic dianhydride such as 1,2,3,4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl 3,3′-4,4′-tetracarboxylic dianhydride and their positional isomers . These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride, 1,2,3,4-pentanetetracarboxylic dianhydride, etc. These may be used alone or in combination of two or more. Moreover, you may use combining a cycloaliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride.

Among the above tetracarboxylic dianhydrides, 4,4′-oxydiphthalic dianhydride, 3, 3 from the viewpoint of easily increasing the surface hardness, flexibility, bending resistance, transparency of the film, and easily reducing the yellowness. ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-biphenyltetracarboxylic dianhydride, 2,2 ', 3,3'-biphenyltetracarboxylic dianhydride 3,3 ′, 4,4′-diphenylsulfonetetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 4,4 ′-(hexafluoroisopropylidene) Diphthalic dianhydride and mixtures thereof are preferred, and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) and 4,4 ′-(hexafluoroisopropylate) Den) diphthalic acid dianhydride (6FDA), and more preferably mixtures thereof, 4,4 '- (hexafluoro isopropylidene) diphthalic anhydride are more preferred.

The polyamideimide resin A preferably has at least a structural unit derived from tetracarboxylic dianhydride in which Y in the formula (4) is represented by the formula (4g ′). In this case, since the film of the present invention has high transparency and the polyamideimide resin A has a high flexibility skeleton, the solubility of the polyamideimide resin in the solvent is improved, and the film of the present invention is produced. Since the viscosity of the polyamideimide varnish used at the time can be suppressed low, the film of the present invention can be easily produced.

[In the formula (4g ′), R ¹⁸ to R ²⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and are included in R ¹⁸ to R ^25. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ]

In the formula (4g ′), R ¹⁸ to R ²⁵ each independently represents a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, preferably a hydrogen atom or 1 to 6 represents an alkyl group, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, wherein the hydrogen atoms contained in R ¹⁸ to R ²⁵ are each independently substituted with a halogen atom. Also good. From the viewpoint of the surface hardness and flexibility of the film of the present invention, R ¹⁸ to R ²⁵ are each independently more preferably a hydrogen atom, a methyl group, a fluoro group, a chloro group or a trifluoromethyl group, particularly preferably. Is a hydrogen atom or a trifluoromethyl group.

In one preferable embodiment described above, the polyamideimide resin A preferably has at least a structural unit derived from tetracarboxylic dianhydride in which Y in the formula (4) is represented by the formula (4g ″). In this case, the film of the present invention has high transparency, and at the same time, the polyamideimide resin A has a skeleton containing a fluorine element, so that the solubility of the polyamideimide resin in the solvent is improved, and the film of the present invention is Since the viscosity of the polyamidoimide varnish used when producing can be suppressed low, it becomes easy to manufacture the film of this invention.

[In the formula (4g ″), * represents a bond. ]

When the polyamideimide resin A has a structural unit derived from two or more kinds of tetracarboxylic dianhydrides, Y in the formula (4) is represented by the formula (4g ′), preferably the formula (4g ″). The amount of the structural unit derived from the tetracarboxylic dianhydride is the entire structural unit derived from the tetracarboxylic dianhydride contained in the polyamideimide resin A from the viewpoint of improving the transparency of the film and the ease of production. Is preferably 50 mol% or more, more preferably 60 mol% or more, still more preferably 70 mol% or more. The upper limit of the amount of the structural unit derived from tetracarboxylic dianhydride in which Y in Formula (4) is represented by Formula (4g ′), preferably Formula (4g ″) is not particularly limited, and polyamideimide resin It may be 100 mol% or less based on the entire structural unit derived from tetracarboxylic dianhydride contained in the carboxylic acid. The ratio of the structural unit derived from the diamine in which X in Formula (4) is represented by Formula (4g ′) or Formula (4g ″) can be measured using, for example, two-dimensional NMR, It can also be calculated from the charging ratio.

The polyamide-imide resin A contained in the film of the present invention may further have a structural unit derived from tricarboxylic acid. Examples of the tricarboxylic acid include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and acid chloride compounds, acid anhydrides and the like that are analogs thereof. One type of tricarboxylic acid may be used, or two or more types may be used in combination. Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; phthalic acid anhydride and benzoic acid are a single bond, —O— , —CH ₂ —, —C (CH ₃ ) ₂ —, —C (CF ₃ ) ₂ —, —SO ₂ —, or a compound connected by a phenylene group.

In a preferred embodiment of the present invention, the polyamideimide resin A contained in the film of the present invention comprises dicarboxylic acid (dicarboxylic acid analog such as acid chloride), diamine and tetracarboxylic acid (acid chloride, tetracarboxylic dianhydride). And a tetracarboxylic acid analog such as tricarboxylic acid (an analog of a tricarboxylic acid compound such as an acid chloride compound or a tricarboxylic acid anhydride). In this embodiment, the polyamideimide resin A has a structural unit represented by the formula (5) and a structural unit represented by the following formula (6).

[In formula (5), X and Y are as defined above. ]

[In formula (6), X and Z are as defined above. ]
X, Y, and Z in Formula (5) and Formula (6) are synonymous with X in Formula (3), Y in Formula (4), and Z in Formula (2), respectively. 2) to the above-mentioned preferable descriptions regarding X, Y and Z in the formula (4) are similarly applied to X, Y and Z in the formula (5) and the formula (6). The structural unit represented by the formula (5) is usually a structural unit derived from diamine and tetracarboxylic acid, and the structural unit represented by the formula (6) is usually structural unit derived from diamine and dicarboxylic acid. It is.

In a preferred embodiment of the present invention, the polyamideimide resin A contained in the film of the present invention further comprises a structural unit represented by the formula (7) and / or a structural unit represented by the following formula (8). You may have.

[In Formula (7), X ¹ represents a divalent organic group, and Y ¹ represents a tetravalent organic group. ]

[In Formula (8), X ² represents a divalent organic group, and Y ² represents a trivalent organic group. ]

In Formula (7), Y ¹ is each independently a tetravalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. Examples of Y ¹ include groups represented by formulas (4a) to (4j), and tetravalent chain hydrocarbon groups having 6 or less carbon atoms. The polyamideimide resin A may have a structural unit represented by one type of formula (7), or may be represented by two or more types of formula (7) that are different from each other in Y ¹ and / or X ¹ . You may have a structural unit.

In Formula (8), Y ² is each independently a trivalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. Examples of Y ² include a group in which any one of the bonds of the groups represented by formulas (4a) to (4j) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms. Is done. The polyamide-imide resin A may have a structural unit represented by one type of formula (8), or may be represented by two or more types of formula (7) that are different from each other in Y ² and / or X ² . You may have a structural unit.

In the formulas (7) and (8), X ¹ and X ² are each independently a divalent organic group, preferably a hydrocarbon group or a fluorine-substituted hydrocarbon in which a hydrogen atom in the organic group is substituted An organic group which may be substituted with a group. X ¹ and X ² are groups represented by formulas (3a) to (3i); a hydrogen atom in the groups represented by formulas (3a) to (3i) is a methyl group, a fluoro group, or a chloro group Or a group substituted with a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In a preferred embodiment of the present invention, the polyamideimide resin A contained in the film of the present invention comprises the structural unit represented by the formula (5) and the formula (6), and optionally the formula (7) and / or the formula ( 8). In this embodiment, from the viewpoint of easily increasing the flexibility and surface hardness of the film, the amount of the structural unit represented by the formula (5) and the formula (6) contained in the polyamideimide resin A is expressed by the formula (5) and the formula ( 6), and in some cases, based on all the structural units represented by formula (7) and formula (8), it is preferably at least 80%, more preferably at least 90%, and even more preferably at least 95%. In addition, the upper limit of the amount of the structural unit represented by the formula (5) and the formula (6) included in the polyamideimide resin A is the formula (5) and the formula (6), and optionally the formula (7) and Based on all the structural units represented by Formula (8), it is usually 100% or less. In addition, the said ratio can be measured, for example using two-dimensional NMR, or can also be computed from the preparation ratio of a raw material.

The glass transition temperature Tg calculated by tan δ in dynamic viscoelasticity measurement (DMA measurement) of the polyamideimide resin A contained in the film of the present invention is preferably less than 380 ° C., more preferably 379 ° C. or less, and further preferably It is 378 degrees C or less, for example, 370 degrees C or less. When the glass transition temperature Tg of the polyamide-imide resin A is less than the above upper limit or below the above upper limit, the film of the present invention is likely to exhibit high surface hardness, and at the same time, the elastic modulus is easily lowered and the flexibility is easily increased. . Although the minimum of glass transition temperature Tg is not specifically limited, Usually, it is 300 degreeC or more. The method for calculating the glass transition temperature by tan δ in the dynamic viscoelasticity measurement (DMA measurement) can be specifically performed as in the examples.

The weight average molecular weight (Mw) of the polyamideimide resin A contained in the film of the present invention is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 50,000 or more, and particularly preferably 70,000 or more. It is preferably 800,000 or less, more preferably 600,000 or less, further preferably 500,000 or less, and particularly preferably 450,000 or less. When the weight average molecular weight (Mw) of the polyamideimide resin A is not less than the above lower limit, the bending resistance of the film of the present invention can be easily increased. When the weight average molecular weight (Mw) of the polyamide-imide resin A is not more than the above upper limit, the solubility of the polyamide-imide resin in the solvent is improved, and the viscosity of the polyamide-imide varnish used when producing the film of the present invention is increased. Since it can suppress low, it becomes easy to manufacture the film of this invention. Further, since the film can be easily stretched, the processability is good. The weight average molecular weight (Mw) can be determined by, for example, GPC measurement and standard polystyrene conversion, and can be specifically determined by the method described in the examples.

The polyamideimide resin A contained in the film of the present invention preferably contains a halogen atom, and more preferably contains a fluorine atom. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group. When the polyamideimide resin A contains a halogen atom, it is easy to reduce the yellowness (YI value) of the film of the present invention, and it is easy to achieve both high flexibility and bending resistance. From the viewpoints of reducing the yellowness (improving transparency), reducing the water absorption rate, and bending resistance of the film of the present invention, the halogen atom is preferably a fluorine atom. From the above viewpoint, the polyamideimide resin A preferably has at least a structural unit derived from a fluorine atom-containing diamine and / or a fluorine atom-containing tetracarboxylic dianhydride.

The content of the halogen atom in the polyamide-imide resin A is the mass of the polyamide-imide resin A contained in the film of the present invention from the viewpoints of reducing yellowness (improving transparency), reducing water absorption, and suppressing film deformation. Is preferably 1% by mass to 40% by mass, more preferably 3% by mass to 35% by mass, and still more preferably 5% by mass to 32% by mass.

The film of the present invention may contain an additive having a light absorption function in addition to the polyamideimide resin from the viewpoint of improving the visibility and quality of the film of the present invention. Examples of the additive having a light absorbing function include an ultraviolet absorber and a bluing agent. The additive having a light absorbing function is preferably selected from the group consisting of an ultraviolet absorber and a bluing agent because the visibility and quality of the film of the present invention are easily improved. The film of the present invention may contain one kind of additive having a light absorbing function, or may contain two or more kinds of additives having a light absorbing function. Here, when an additive having a light absorbing function such as an ultraviolet absorber and a bluing agent is added to a film containing a conventional polyamideimide resin, since these additives have low heat resistance, a polyamideimide resin is used. In the process of heating the containing film under high-temperature conditions, there was a problem that degradation or the like occurred and the quality of the film deteriorated. Therefore, for example, it has been necessary to take measures such as adding these additives to a layer different from the layer containing the polyamideimide resin and bonding the additive to the polyamideimide film. For example, when a film is produced using the resin composition of the present invention or the composition containing the polyamideimide resin obtained by the production method of the present invention, the imidation ratio of the polyamideimide resin contained in the resin composition is increased in advance. I can keep it. Therefore, even when a film is produced under relatively low-temperature heating conditions, the imidization rate can be increased and sufficiently high surface hardness can be achieved. Therefore, even when an additive having a light absorption function is added to the same layer as the layer containing the polyamideimide resin, decomposition and the like of these additives can be suppressed, and deterioration in film quality can be suppressed.

The ultraviolet absorber may be appropriately selected from those normally used as an ultraviolet absorber in the field of resin materials. The ultraviolet absorber may contain a compound that absorbs light having a wavelength of 400 nm or less. Examples of the ultraviolet absorber include at least one compound selected from the group consisting of benzophenone compounds, salicylate compounds, benzotriazole compounds, and triazine compounds. When the film of the present invention contains an ultraviolet absorber, the deterioration of the polyamideimide resin is suppressed, so that the visibility of the film can be enhanced. In the present specification, “system compound” refers to a derivative of a compound to which the “system compound” is attached. For example, a “benzophenone compound” refers to a compound having benzophenone as a host skeleton and a substituent bonded to benzophenone.

When the film of the present invention contains an ultraviolet absorber, the addition amount of the ultraviolet absorber may be appropriately selected depending on the type of the ultraviolet absorber to be used, but as a guideline, preferably 1 mass based on the total mass of the film. % Or more, more preferably 2% by mass or more, further preferably 3% by mass or more, preferably 10% by mass or less, more preferably 8% by mass or less, and further preferably 6% by mass or less. The preferred amount of addition varies depending on the ultraviolet absorber used, but adjusting the amount of addition so that the light transmittance at 400 nm is about 20 to 60% makes it easy to improve the light resistance of the film of the present invention, as well as transparency. It is preferable because it is easy to obtain a high film.

The bluing agent may be appropriately selected from those normally used as a bluing agent in the field of resin materials. The bluing agent is an additive (dye, pigment) that adjusts the hue by absorbing light in a wavelength region such as orange to yellow in the visible light region. For example, ultramarine, bitumen, cobalt blue, etc. And inorganic dyes and pigments such as organic dyes and pigments such as phthalocyanine blueing agents and condensed polycyclic blueing agents. The bluing agent is not particularly limited, but from the viewpoint of heat resistance, light resistance, and solubility, a condensed polycyclic bluing agent is preferable, and an anthraquinone bluing agent is more preferable. From the viewpoint of heat resistance, the bluing agent preferably has a thermal decomposition temperature of 200 ° C. or higher. Examples of the condensed polycyclic bluing agent include anthraquinone bluing agents, indigo bluing agents, and phthalocyanine bluing agents.

When the film of the present invention contains a bluing agent, the amount of bluing agent added may be appropriately selected depending on the type of bluing agent to be used, but as a guideline, it is preferably based on the total mass of the film. 01% by mass or more, more preferably 0.02% by mass or more, further preferably 0.03% by mass or more, preferably 1.0% by mass or less, more preferably 0.5% by mass or less, and further preferably 0%. .2% by mass or less.

The film of the present invention may further contain an inorganic material such as inorganic particles in addition to the polyamideimide resin. Examples of the inorganic material include inorganic particles such as titania particles, alumina particles, zirconia particles, and silica particles, and silicon compounds such as quaternary alkoxysilanes such as tetraethyl orthosilicate. From the viewpoint of the stability of the polyamideimide varnish, the inorganic material is preferably inorganic particles, particularly silica particles. The inorganic particles may be bonded by molecules having a siloxane bond.

The average primary particle diameter of the inorganic particles is preferably 10 to 100 nm, more preferably 20 to 80 nm, from the viewpoints of transparency of the film, mechanical properties, and suppression of aggregation of the inorganic particles. In the present invention, the average primary particle diameter can be determined by measuring 10 constant-direction diameters with a transmission electron microscope (TEM) and calculating an average value thereof.

When the film of the present invention contains an inorganic material, the content of the inorganic material in the film is preferably 0 to 90% by mass, more preferably 0 to 60% by mass, and still more preferably 0, based on the total mass of the film. ~ 40% by weight. If the content of the inorganic material is within the above range, the transparency and mechanical properties of the film tend to be compatible.

The film of the present invention may contain other additives. Examples of other additives include antioxidants, mold release agents, stabilizers, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, and leveling agents. When the film of the present invention contains other additives, the content of the other additives is preferably 0% by mass or more and 20% by mass or less, more preferably 0% by mass based on the mass of the film of the present invention. It is 10 mass% or less.

(Layer structure)
The layer structure of the film of the present invention is not particularly limited, and may be a single layer or a multilayer of two or more layers. When the film of the present invention further contains an additive such as an additive having a light absorption function, the additive and the polyamideimide resin are combined into one layer from the viewpoint of thinning the image display device and economy. It is preferable to contain. In this case, the film of the present invention is more preferably a single layer containing the additive and the polyamideimide resin, or a laminate having at least a layer containing the additive and the polyamideimide resin. From the viewpoint of impact resistance, the film of the present invention preferably has a multilayer structure of two or more layers including at least a layer containing a polyamideimide resin. When the film of the present invention further contains an additive such as an additive having a light absorption function, it is a laminate having at least a layer containing the additive and a polyamideimide resin, or a layer containing the additive, It may be a laminate having at least a layer containing a polyamideimide resin.

The film of the present invention may be a polyamideimide laminate in which one or more functional layers are further laminated on the above layer. Examples of the functional layer include layers having various functions such as a hard coat layer, an ultraviolet absorbing layer, an adhesive layer, a refractive index adjusting layer, and a primer layer. The film of the present invention may include one or more functional layers. One functional layer may have a plurality of functions. For example, the functional layer may be formed on a film containing a polyamideimide resin to obtain a multilayer film.

The present invention has a structural unit derived from a diamine, a structural unit derived from a dicarboxylic acid, and a structural unit derived from a tetracarboxylic dianhydride and has an imidization ratio of 60% or more as measured by two-dimensional NMR. There is also provided a resin composition containing at least a polyamideimide resin B having a solvent and a solvent. In addition, the film of this invention containing the said polyamideimide resin A is manufactured using the resin composition of this invention containing the polyamideimide resin B and a solvent at least, for example.

The resin composition of the present invention contains a polyamideimide resin B having an imidization ratio of 60% or more as measured by two-dimensional NMR. The resin composition of the present invention is a composition used for producing a film containing a polyamideimide resin, and since it contains a polyamideimide resin B having a high imidization ratio as described above, the film finally obtained It is possible to sufficiently increase the imidization ratio of the polyamideimide resin contained in the resin, and as a result, it is possible to obtain a polyamideimide film having a sufficiently high surface hardness. When the imidization ratio of the polyamide-imide resin contained in the resin composition is lower than 60%, there is a tendency to become a polyamideimide having an excessively flexible primary structure. Can not be increased. From the viewpoint of surface hardness, the imidation ratio of the polyamideimide resin B is preferably 80% or more, more preferably 90% or more, and even more preferably 95% or more. The higher the imidization rate, the better. The upper limit is not particularly limited, and it may be 100% or less.

The imidation ratio of the polyamide-imide resin B is the ratio of the number of moles of imide bonds in the polyamide-imide resin B to the value twice the number of moles of structural units derived from the tetracarboxylic dianhydride in the polyamide-imide resin B. In this specification, it is measured by two-dimensional NMR. The imidation ratio of the polyamideimide resin B was obtained by dissolving the polyamideimide resin B, which was precipitated and dried by a reprecipitation method by adding a poor solvent to the resin composition (varnish), in a dehydrated solvent which is a good solvent. Measurement can be performed using two-dimensional NMR using a predetermined solution as a measurement sample.
Examples of the poor solvent include alcohol solvents, water, saturated hydrocarbon solvents, and aromatic solvents, and preferably alcohol solvents and water. Alcohol solvents include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 1-isobutanol, 1-heptanol, 2-heptanol, 3-heptanol, 1-hexanol, 2-hexanol , 3-hexanol, ethylene glycol, glycerin and the like, preferably methanol, ethanol, 1-propanol and 2-propanol, more preferably methanol and ethanol. Moreover, two or more of these poor solvents may be mixed.
Examples of the deuterated solvent that is a good solvent include deuterated dimethyl sulfoxide (DMSO-d6).
The imidization rate is represented by the following formula (9).

Imidation rate (%) = [1- (number of moles of repeating unit having an amic acid) / (number of moles of repeating unit having an imide bond)] × 100 Formula (9)

A polyimide resin or a polyimide film obtains a molar ratio by appropriately integrating a signal derived from a repeating unit having an amic acid on a ¹ H-NMR spectrum and a signal derived from a repeating unit having an imide bond. The imidation ratio can be obtained by applying to the above formula (9). Here, the amic acid includes an amide bond and a carboxyl group, which are precursors of an imide bond.
Polyamideimide resin or polyamideimide film, for example, appropriately receives signals derived from repeating units having an amic acid and repeating units having an imide bond on a two-dimensional NMR spectrum measured with deuterated dimethyl sulfoxide (DMSO-d6). By converting the value obtained by integration, the imidization rate can be obtained. Examples of the conversion method include applying a correlation formula of the value to the imidization ratio obtained by the ¹ H-NMR spectrum.

In order to obtain an imidization rate with high accuracy, conventionally known or commonly used methods are applied. Examples of such a method include increasing the S / N ratio, which is the ratio of signal to noise, and integrating the obtained two-dimensional NMR spectrum with high accuracy. In order to obtain the imidization ratio with higher accuracy, the S / N ratio is preferably 6 or more. Examples of the method for increasing the S / N ratio include increasing the sample concentration, increasing the number of integrations, and using a highly sensitive NMR measuring apparatus. Examples of the highly sensitive NMR measuring apparatus include an NMR apparatus having a stronger magnetic field and an NMR apparatus using a cryoprobe. Examples of a method for accurately integrating a two-dimensional NMR spectrum include performing phase correction and performing baseline correction. Furthermore, when signals on a two-dimensional NMR spectrum derived from a structure different from the repeating unit having an amic acid and the repeating unit having an imide bond overlap, it is accurately integrated by not including the intensity of the signal. An imidation ratio can be obtained.

The glass transition temperature Tg calculated by tan δ in the dynamic viscoelasticity measurement (DMA measurement) of the polyamideimide resin B is preferably less than 380 ° C., more preferably 379 ° C. or less, further preferably 378 ° C. or less, for example 370 ° C. It is as follows. When the glass transition temperature Tg of the polyamide-imide resin B is less than the above upper limit or less than the above upper limit, the film obtained using the resin composition of the present invention is likely to exhibit high surface hardness and at the same time has an elastic modulus. It is easy to decrease and it is easy to increase flexibility. Although the minimum of glass transition temperature Tg is not specifically limited, Usually, it is 300 degreeC or more. The method for calculating the glass transition temperature by tan δ in the dynamic viscoelasticity measurement (DMA measurement) can be specifically performed as in the examples.

The weight average molecular weight (Mw) of the polyamideimide resin B contained in the film of the present invention is preferably 5,000 or more, more preferably 10,000 or more, still more preferably 50,000 or more, and particularly preferably 70,000 or more. It is preferably 800,000 or less, more preferably 600,000 or less, further preferably 500,000 or less, and particularly preferably 450,000 or less. When the weight average molecular weight (Mw) of the polyamideimide resin B is not less than the above lower limit, the bending resistance of a film obtained using the resin composition of the present invention can be easily increased. When the weight average molecular weight (Mw) of the polyamideimide resin B is not more than the above upper limit, the solubility of the polyamideimide resin in the solvent is improved, and the viscosity of the resin composition of the present invention can be suppressed low. It becomes easy to manufacture a film. Further, since the film can be easily stretched, the processability is good. The weight average molecular weight (Mw) can be determined by, for example, GPC measurement and standard polystyrene conversion, and can be specifically determined by the method described in the examples.

The polyamideimide resin B contained in the resin composition of the present invention has a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride. Regarding the specific examples and preferred embodiments of the diamine, dicarboxylic acid and tetracarboxylic dianhydride, the above description regarding the polyamideimide resin A similarly applies. Similarly to the polyamideimide resin A, the polyamideimide resin B contained in the resin composition of the present invention may further have a structural unit derived from tricarboxylic acid. As the tricarboxylic acid, the above description regarding the polyamide-imide resin A is similarly applied.

In a preferred embodiment of the present invention, the polyamideimide resin B contained in the resin composition of the present invention contains dicarboxylic acid (dicarboxylic acid analog such as acid chloride), diamine and tetracarboxylic acid (acid chloride, tetracarboxylic acid dicarboxylic acid). A polycondensation polymer that is a polycondensation product with a tricarboxylic acid (an acid chloride compound, a tricarboxylic acid compound analog such as a tricarboxylic acid anhydride) in some cases and a tetracarboxylic acid analog such as an anhydride). . In this embodiment, the polyamideimide resin B, like the polyamideimide resin A, has a structural unit represented by the formula (5) and a structural unit represented by the formula (6).

[In formula (5), X and Y are as defined above. ]

In a preferred embodiment of the present invention, the polyamideimide resin B contained in the resin composition of the present invention is a structural unit represented by the following formula (7) and / or a structure represented by the following formula (8). You may have a unit.

In Formula (7), Y ¹ is each independently a tetravalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. Examples of Y ¹ include groups represented by formulas (4a) to (4j), and tetravalent chain hydrocarbon groups having 6 or less carbon atoms. The polyamideimide resin B may have a structural unit represented by one type of formula (7), or may be represented by two or more types of formula (7) that are different from each other in Y ¹ and / or X ¹ . You may have a structural unit.

In Formula (8), Y ² is each independently a trivalent organic group, and preferably a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. Organic group. The organic group is preferably a trivalent organic group having 4 to 40 carbon atoms. The hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. The organic group preferably has 4 to 40 carbon atoms. Y ² represents a group in which any one of the bonds in the groups represented by the above formulas (4a) to (4j) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms Is exemplified. The polyamideimide resin B may have a structural unit represented by one type of formula (8), or may be represented by two or more types of formula (7) that are different from each other in Y ² and / or X ² . You may have a structural unit. The example of W ^{1 in} the formula is the same as the example of W ^{1 in} the description relating to Y ¹ .

In the formulas (7) and (8), X ¹ and X ² are each independently a divalent organic group, preferably a hydrocarbon group or a fluorine-substituted hydrocarbon in which a hydrogen atom in the organic group is substituted An organic group which may be substituted with a group. The organic group is preferably a divalent organic group having 4 to 40 carbon atoms. The hydrocarbon group and the fluorine-substituted hydrocarbon group preferably have 1 to 8 carbon atoms. The organic group preferably has 4 to 40 carbon atoms. X ¹ and X ² are groups represented by formulas (3a) to (3i); a hydrogen atom in the groups represented by formulas (3a) to (3i) is a methyl group, a fluoro group, or a chloro group Or a group substituted with a trifluoromethyl group; and a chain hydrocarbon group having 6 or less carbon atoms.

In a preferred embodiment of the present invention, the polyamideimide resin B contained in the resin composition of the present invention comprises the structural units represented by the formulas (5) and (6), and optionally the formula (7) and / or It consists of a structural unit represented by Formula (8). In this embodiment, from the viewpoint of easily increasing the flexibility and surface hardness of the film, the amount of the structural unit represented by the formula (5) and the formula (6) contained in the polyamideimide resin B is expressed by the formula (5) and the formula ( 6), and in some cases, based on all the structural units represented by formula (7) and formula (8), it is preferably at least 80%, more preferably at least 90%, and even more preferably at least 95%. In addition, the upper limit of the amount of the structural unit represented by the formula (5) and the formula (6) included in the polyamideimide resin B is the formula (5) and the formula (6), and in some cases, the formula (7) and Based on all the structural units represented by Formula (8), it is usually 100% or less. In addition, the said ratio can be measured, for example using two-dimensional NMR, or can also be computed from the preparation ratio of a raw material.

The polyamideimide resin B contained in the resin composition of the present invention also preferably contains a halogen atom, more preferably a fluorine atom, like the polyamideimide resin A. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group. When the polyamideimide resin B contains a halogen atom, it is easy to reduce the yellowness (YI value) of the film obtained using the resin composition of the present invention, and it is easy to achieve both high flexibility and bending resistance. From the viewpoints of reducing the yellowness of the film (improving transparency), reducing the water absorption rate, and bending resistance, the halogen atom is preferably a fluorine atom. From the above viewpoint, the polyamideimide resin B preferably has at least a structural unit derived from a fluorine atom-containing diamine and / or a fluorine atom-containing tetracarboxylic dianhydride.

The content of halogen atoms in the polyamide-imide resin B is the polyamide-imide resin B contained in the resin composition of the present invention from the viewpoint of reducing yellowness (improving transparency), reducing water absorption, and suppressing film deformation. Is preferably 1 to 40% by mass, more preferably 3 to 35% by mass, and still more preferably 5 to 32% by mass.

The solvent contained in the resin composition of the present invention is not particularly limited as long as the polyamideimide resin B can be dissolved. Examples of such solvents include amide solvents such as N, N-dimethylacetamide (DMAc) and N, N-dimethylformamide; lactone solvents such as γ-butyrolactone and γ-valerolactone; dimethylsulfone, dimethylsulfoxide, sulfolane and the like. Sulfur-containing solvents of: carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof (mixed solvents). Among these solvents, an amide solvent or a lactone solvent is preferable, and a solvent containing dimethylacetamide is more preferable. The polyamideimide varnish may contain water, alcohol solvents, ketone solvents, acyclic ester solvents, ether solvents and the like. The resin composition of the present invention may further contain an additive that can be included in the film of the present invention described above.

Next, a method for producing the polyamideimide resin A contained in the film of the present invention and the polyamideimide resin contained in the resin composition of the present invention will be described below. Polyamideimide resins A and B are prepared by, for example, copolymerizing (polycondensing) the above-mentioned dicarboxylic acid, diamine and tetracarboxylic acid as main raw materials and optionally further together with the tricarboxylic acid described above. Can be manufactured.

The method for producing the polyamide-imide resin A contained in the film of the present invention and the polyamide-imide resin B contained in the resin composition of the present invention is not particularly limited as long as the polyamide-imide resin having the above characteristics is obtained.
(1) a step of copolymerizing diamine, dicarboxylic acid, and tetracarboxylic dianhydride in a solvent to obtain a polyamideimide resin precursor; and
(2) It can be produced by a method including at least a step of adding a dehydrating agent and a tertiary amine to a solution containing at least a polyamideimide resin precursor and heating at a temperature of 70 to 120 ° C.

The present invention also provides
(1) a step of copolymerizing diamine, dicarboxylic acid, and tetracarboxylic dianhydride in a solvent to obtain a polyamideimide resin precursor; and
(2) At least a step of adding a dehydrating agent and a tertiary amine to a solution containing at least a polyamideimide resin precursor and heating at a temperature of 70 to 120 ° C., in a solvent at the start of step (1) A method for producing a polyamide-imide resin is also provided in which w and t satisfy the following formula, where w is the water content of w (ppm) and t is the heating time in step (2).

The polyamide-imide resin obtained by the production method of the present invention may be, for example, polyamide-imide resin A or polyamide-imide resin B, and the description described above for polyamide-imide resin A and polyamide-imide resin B applies similarly. In addition, it is also possible to obtain the resin composition of the present invention by the production method of the present invention, and to produce the film of the present invention using the resin composition.
In this embodiment, the polyamideimide resin obtained by the production method of the present invention and the polyamideimide resin B contained in the resin composition of the present invention are the same resin. Further, the polyamideimide resin B contained in the resin composition of the present invention and the polyamideimide resin A contained in the film of the present invention may be the same resin in terms of imidization rate, resin structural unit, and the like. Further, resins different from each other in imidation ratio may be used.

In step (1), diamine, dicarboxylic acid and tetracarboxylic dianhydride are copolymerized in a solvent to obtain a polyamideimide resin precursor. The reaction temperature for carrying out the copolymerization is not particularly limited, but is, for example, 50 to 350 ° C. The reaction time is not particularly limited, but is, for example, about 30 minutes to 10 hours. If necessary, the reaction may be carried out under an inert atmosphere or under reduced pressure. As a solvent used at a process (1), the solvent contained in the resin composition of this invention described above is mentioned, for example.

In step (1), an imidization catalyst may be used. Examples of imidation catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydro Alicyclic amines (monocyclic) such as azepine; azabicyclo [2.2.1] heptane, azabicyclo [3.2.1] octane, azabicyclo [2.2.2] octane, and azabicyclo [3.2. 2] Cycloaliphatic amines (polycyclic) such as nonane; and pyridine, 2-methylpyridine, 3-methylpyridine, 4-methylpyridine, 2-ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2, 4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5, 7,8 tetrahydroisoquinoline, and aromatic amines isoquinoline.

Next, in step (2), a dehydrating agent and a tertiary amine are added to a solution containing at least the polyamideimide resin precursor, and heated at a temperature of 70 to 120 ° C. In this step, imidization of the polyamideimide resin precursor proceeds. The heating time in this step may be appropriately selected according to the reaction scale and the type and amount of the reagent used, but is usually 1 to 48 hours. From the viewpoint of finally obtaining a polyamideimide film having a reduced yellowness and a high surface hardness, the imidation ratio of the polyamideimide resin contained in the polyamideimide resin composition is preferably 60% or more in this step. More preferably, step (2) may be performed until 80% or more, and even more preferably 95% or more.

The dehydrating agent used in the step (2) is a substance that can promote copolymerization in a solvent with diamine, dicarboxylic acid, and tetracarboxylic dianhydride, which are polycondensation reactions involving dehydration. Examples of the dehydrating agent include acetic anhydride, propionic anhydride, isobutyric anhydride, pivalic anhydride, butyric anhydride, and isovaleric anhydride. The dehydrating agent is preferably selected from the group consisting of acetic anhydride and propionic anhydride, more preferably acetic anhydride.

The tertiary amine used in step (2) is a substance that acts as an imidization catalyst. Examples of the tertiary amine include the above-mentioned aromatic amine and aliphatic amine. The tertiary amine is preferably selected from the group consisting of triethylamine, tripropylamine, N-ethylpiperidine, N-propylpiperidine, pyridine, methylpyridine, ethylpyridine, dimethylpyridine and isoquinoline.

In the production method of the present invention, assuming that the amount of water in the solvent at the start of step (1) is w (ppm) and the heating time in step (2) is t (minutes), w and t are the following formulas: Meet.

1 / t (w + 167) is preferably 5.0 or less, more preferably 4.0 or less, and even more preferably 3.0 or less. Copolymerization of a diamine, dicarboxylic acid, and tetracarboxylic dianhydride for producing a polyamideimide resin in a solvent is a polycondensation reaction involving dehydration. Therefore, by reducing the amount of water present in the reaction system or adjusting the heating time, the polycondensation reaction (especially imidization reaction) can be efficiently advanced, and as a result, obtained. The imidation ratio in the polyamideimide resin can be increased. Therefore, according to the said manufacturing method of this invention, the polyamide imide resin which has a higher imidation ratio than before can be manufactured. In addition, it is difficult to raise the imidation ratio of a polyamideimide resin sufficiently by a conventionally known production method. Therefore, the process which produces a film using the polyamide-imide varnish containing the polyamidoimide resin which has a comparatively low imidation rate, heats this film on high temperature conditions, and advances imidation is performed. However, as described above, when heating is performed in a film state to increase the imidization rate, a sufficiently high imidization rate cannot be achieved, sufficient surface hardness cannot be obtained, and depending on the heating conditions Has a problem that the imidization rate of the polyamideimide resin varies and the imidization rate is not stable. According to the production method of the present invention, the imidation ratio of the polyamideimide resin can be easily increased sufficiently at the synthesis stage before being processed into a film, and the above problems are solved.

The production method of the present invention is not particularly limited as long as it includes at least step (1) and step (2). As a method for producing a resin composition containing a polyamideimide resin obtained by the production method of the present invention, for example, a mixed solution containing the polyamideimide resin obtained in the step (1) and the step (2), further a solvent and necessary The resin composition containing at least a polyamide-imide resin and a solvent (hereinafter, also referred to as “polyamide-imide varnish”) may be produced by adding an additive and stirring according to step (1) and A poor solvent is added to the mixed solution containing the polyamideimide resin obtained in the step (2), the polyamideimide resin is precipitated by a reprecipitation method, dried and taken out as a precipitate, and the taken polyamideimide resin precipitate is dissolved in the solvent. Thus, a resin composition containing at least a polyamideimide resin and a solvent may be obtained.

The film of the present invention is, for example, (1) a step of applying a polyamideimide resin composition obtained as described above to a support, and
(2-1) A step of peeling the coating film of the composition from the support after drying, or
(2-2) It can be produced by a production method including at least a step of peeling the coating film of the composition from the support after drying and a step of heating the peeled film. Thus, the film of the present invention is obtained by drying the coating film of the polyamideimide resin composition obtained as described above.

For example, a polyamide-imide varnish coating is formed by applying a polyamide-imide varnish on a support such as a resin substrate, a SUS belt, or a glass substrate by a known roll-to-roll or batch method. Can do. Examples of the support include a PET film, a PEN film, a polyimide film, and a polyamideimide film. Among these, from the viewpoint of excellent heat resistance, a PET film, a PEN film, a polyimide film, and other polyamideimide films are preferable. From the viewpoint of adhesion to the film of the present invention and cost, a PET film is more preferable.

Next, in step (2-1) or step (2-2), the polyamide-imide varnish coating is dried, and after drying, peeled off from the support. The coating film can be dried at a temperature of preferably 50 to 240 ° C, more preferably 200 to 240 ° C. If necessary, the coating film may be dried under an inert atmosphere or under reduced pressure. The film of the present invention can be obtained by peeling the coating film from the support after drying. As described in the step (2-2), for example, for the purpose of further increasing the surface hardness (pencil hardness) of the film of the present invention, a step of further heating the peeled film may be performed. The heating temperature is preferably 240 ° C. or lower.

A surface treatment step of performing a surface treatment on at least one surface of the film produced as described above may be performed. Examples of the surface treatment include UV ozone treatment, plasma treatment, and corona discharge treatment.

In a preferred embodiment of the present invention in which the film of the present invention contains an additive such as an additive having a light absorption function, the film of the present invention contains a polyamide-imide resin and the additive in the same layer. The layer can be produced in the same manner as described above by using a polyamideimide varnish obtained by further adding the additive to a composition (polyamideimide varnish) containing at least a polyamideimide resin and a solvent. In a preferred embodiment of the present invention in which an additive such as an additive having a light absorption function and a polyamideimide resin are contained in one layer, it is preferable to use an additive having a thermal decomposition temperature of at least 200 ° C. or more.

The film of the present invention may further include a functional layer. Examples of the functional layer include layers having various functions such as a hard coat layer, an ultraviolet absorbing layer, an adhesive layer, a refractive index adjusting layer, and a primer layer. The film of the present invention may include one or more functional layers. One functional layer may have a plurality of functions.

The hard coat layer is preferably disposed on the surface on the viewing side of the film. The hard coat layer may have a single layer structure or a multilayer structure. The hard coat layer comprises a hard coat layer resin, and examples of the hard coat layer resin include acrylic resins, epoxy resins, urethane resins, benzyl chloride resins, vinyl resins, silicone resins, or a mixture thereof. Examples thereof include ultraviolet curable resins such as resins, electron beam curable resins, and thermosetting resins. In particular, the hard coat layer preferably contains an acrylic resin from the viewpoint of mechanical properties such as surface hardness and from an industrial viewpoint. In one preferred embodiment of the present invention, since the film of the present invention has a high surface hardness, the film has a sufficient surface hardness for use in an image display device or the like without a hard coat layer. For this reason, when the film of the present invention further has a hard coat layer, the surface hardness of the film can be further increased.

The ultraviolet absorbing layer is a layer having an ultraviolet absorbing function. For example, a main material selected from an ultraviolet curable transparent resin, an electron beam curable transparent resin, and a thermosetting transparent resin, It is composed of dispersed UV absorbers. By providing the ultraviolet absorbing layer as the functional layer, a change in yellowness due to light irradiation can be easily suppressed.

The adhesive layer is a layer having an adhesive function, and has a function of bonding the film of the present invention to another member. As the material for forming the adhesive layer, a conventionally known material can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used.

The adhesive layer may be composed of a resin composition containing a component having a polymerizable functional group. In this case, strong adhesion can be realized by further polymerizing the resin composition constituting the adhesive layer after the film is brought into close contact with another member. The adhesive strength between the film of the present invention and the pressure-sensitive adhesive layer may be 0.1 N / cm or more, or 0.5 N / cm or more.

The adhesive layer may contain a thermosetting resin composition or a photocurable resin composition as a material. In this case, the resin composition can be polymerized and cured by supplying energy afterwards.

The pressure-sensitive adhesive layer may be a layer composed of an adhesive called pressure-sensitive adhesive (Pressure Sensitive Adhesive, PSA) that is attached to an object by pressing. The pressure-sensitive adhesive may be a pressure-sensitive adhesive that is “a substance that is sticky at normal temperature and adheres to an adherend with light pressure” (JIS K6800). And an adhesive that can maintain stability until the coating is broken by appropriate means (pressure, heat, etc.) (JIS K6800).

The hue adjusting layer is a layer having a hue adjusting function, and is a layer capable of adjusting the film of the present invention to a target hue. A hue adjustment layer is a layer containing resin and a coloring agent, for example. Examples of the colorant include inorganic pigments such as titanium oxide, zinc oxide, dial, titanium oxide-based fired pigment, ultramarine, cobalt aluminate, and carbon black; azo-based compounds, quinacridone-based compounds, anthraquinone-based compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, selenium compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Examples include acid dyes and mordant dyes.

The refractive index adjusting layer is a layer having a function of adjusting the refractive index, has a refractive index different from the layer containing the polyamideimide resin A in the film of the present invention, and gives a predetermined refractive index to the film of the present invention. It is a layer that can. The refractive index adjustment layer may be, for example, an appropriately selected resin, and optionally a resin layer further containing a pigment, or may be a metal thin film.

Examples of the pigment for adjusting the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide and tantalum oxide. The average primary particle diameter of the pigment may be 0.1 μm or less. By setting the average primary particle diameter of the pigment to 0.1 μm or less, irregular reflection of light transmitted through the refractive index adjusting layer can be prevented, and a decrease in transparency can be prevented.

Examples of the metal used for the refractive index adjustment layer include metals such as titanium oxide, tantalum oxide, zirconium oxide, zinc oxide, tin oxide, silicon oxide, indium oxide, titanium oxynitride, titanium nitride, silicon oxynitride, and silicon nitride. Oxides or metal nitrides may be mentioned.

The film of the present invention is an optical film useful as, for example, a front plate of an image display device, particularly a front plate (window film) of a flexible display. The film of this invention can be arrange | positioned as a front plate on the visual recognition side surface of an image display apparatus, especially a flexible display. The front plate has a function of protecting the image display element in the flexible display.

Examples of the image display device include wearable devices such as a television, a smartphone, a mobile phone, a car navigation system, a tablet PC, a portable game machine, electronic paper, an indicator, a bulletin board, a clock, and a smart watch. Examples of the flexible display include the above-described image display device having flexible characteristics.

Hereinafter, the present invention will be described in more detail with reference to examples. Unless otherwise specified, “%” and “part” in the examples mean mass% and part by mass. First, the evaluation method will be described.

<Measurement of weight average molecular weight (Mw)>
The weight average molecular weight (Mw) of the polyamideimide resin was determined by standard polystyrene conversion by gel permeation chromatography (GPC) measurement. Specific measurement conditions were as follows.
(1) Pretreatment method A DMF eluent (10 mM lithium bromide solution) is added to the obtained polyamideimide resin so as to have a concentration of 2 mg / mL, and the mixture is heated at 80 ° C. with stirring for 30 minutes. A solution obtained by filtration using an open 0.45 μm membrane filter was used as a measurement solution.
(2) Measurement conditions Column: TSKgel SuperAWM-H × 2 + SuperAW2500 × 1 (6.0mm ID × 150mm × 3)
(Both manufactured by Tosoh Corporation)
Eluent: DMF (10 mM lithium bromide added)
Flow rate: 1.0 mL / min.
Detector: RI detector Column temperature: 40 ° C
Injection volume: 100 μL
Molecular weight standard: Standard polystyrene

<Measurement of glass transition temperature (Tg)>
Using a TA Instrument DMA Q800, measurement was performed under the following samples and conditions to obtain a tan δ curve, which is the ratio of the loss elastic modulus to the storage elastic modulus. The Tg of the polyamideimide resin was calculated from the peak of the tan δ curve.
Sample (film): length 5-15mm, width 5mm
Experiment mode: DMA Multi-Frequency-Strain
Detailed experimental mode conditions:
(1) Clamp: Tension: Film
(2) Amplitude: 5 μm
(3) Frequency: 10 Hz (no fluctuation in all temperature sections)
(4) Preload Force: 0.01N
(5) Force Track: 125N
Temperature conditions: (1) Temperature rise range: normal temperature to 400 ° C, (2) Temperature rise rate: 5 ° C / min Main data collected: (1) Storage modulus (E '), (2) Loss modulus (Loss modulus, E "), (3) tan δ (E" / E ')

<Measurement of imidization ratio>
The imidization ratios of the polyimide resin and polyamideimide resin used in Examples and Comparative Examples were measured by NMR and calculated using signals derived from the partial structure shown in Formula (10). The method for calculating the imidization rate from the measurement conditions and the obtained results is as follows.

(Measurement sample preparation method)
Polyamideimide resin B:
A resin composition obtained by adding a large excess amount of methanol to a resin composition (varnish) containing at least a solvent and precipitating and drying by reprecipitation is dissolved in deuterated dimethyl sulfoxide (DMSO-d6) to obtain 2% by mass. A solution was used as a measurement sample.
Polyamideimide resin A:
A film containing the resin was dissolved in deuterated dimethyl sulfoxide (DMSO-d6) to give a 2% by mass solution, which was used as a measurement sample.
(NMR measurement conditions)
Measuring apparatus: 600 MHz NMR apparatus AVANCE600 manufactured by Bruker
Sample temperature: 303K
Measuring method: 1H-NMR, HSQC
(Calculation method of imidization ratio of polyimide resin)
In the ¹ H-NMR spectrum obtained using the solution containing the polyimide resin as the measurement sample, the integral value of the signal derived from the proton (A) in the formula (10) is represented by Int _A and the integral of the signal derived from the proton (B). The value was Int _B. From these values, the imidization ratio (%) was determined by the following formula (NMR-1).

(Calculation method of imidization ratio of polyamide-imide resin)
In the HSQC spectrum obtained using a solution containing a polyimide resin as a measurement sample, the integral value of the signal derived from the proton (C) in the formula (10XXX) is the signal derived from Int _C , proton (D), and proton (E). The average value of the integrated values of was defined as Int _DE . From these values, the β value was determined by the following formula (NMR-2).

Next, for a plurality of polyimide resins, the β value according to the formula (NMR-2) and the imidization ratio (%) according to the formula (NMR-1) were obtained, and the following correlation formula (NMR-3) was obtained from the results. .

Then, in the HSQC spectrum obtained using the solution containing the polyamideimide resin as a measurement sample, the β value was determined by the formula (NMR-2) in the same manner as described above. By substituting this β value into the above correlation equation (NMR-3), the imidization ratio (%) of the polyamideimide resin was obtained.

<Measurement of total light transmittance (Tt)>
The total light transmittance Tt of the obtained polyamideimide film was measured by a fully automatic direct reading haze computer HGM-2DP manufactured by Suga Test Instruments Co., Ltd. according to JIS K7105: 1981.

<Measurement of yellowness (YI value)>
The yellowness (Yellow Index: YI value) of the obtained polyamideimide film is measured using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO Corporation in accordance with JIS K 7373: 2006. did. After performing background measurement in the absence of a sample, the sample was set in a sample holder, and the transmittance for light of 300 to 800 nm was measured to obtain tristimulus values (X, Y, Z). The YI value was calculated based on the following formula.

<Measurement of surface hardness>
As the surface hardness of the obtained polyamideimide film, the pencil hardness of the sample surface was measured according to JIS K5600-5-4: 1999. Measurement was performed under the conditions of a load of 100 g and a scanning speed of 60 mm / min, and under the illuminance condition of a light amount of 4000 lux, the presence or absence of scratches was evaluated, and the pencil hardness was determined.

<Measurement of elastic modulus>
The elastic modulus of the obtained polyamideimide film was measured using an autograph AG-IS manufactured by Shimadzu Corporation. Using a film cut into a width of 10 mm as a test piece, an SS curve was measured under the conditions of a distance between chucks of 500 mm and a tensile speed of 20 mm / min, and the elastic modulus was calculated from the slope.

<Measurement of bending resistance>
As the bending resistance of the obtained polyamideimide film, the number of reciprocal bendings was measured using an MIT folding fatigue tester (model 0530) manufactured by Toyo Seiki Seisakusho. A film cut out to a thickness of 50 μm and a width of 10 mm was used as a test piece, and the number of reciprocal bendings until the film was broken was measured under the conditions of R = 1 mm, 135 °, load 0.75 kgf, and speed 175 cpm.

[Example 1]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, N, N-dimethylacetamide with 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and a water content adjusted to 500 ppm (DMAc) 693.8 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added to the flask. (BPDA) 9.57g (32.52mmol) was added, and it stirred at room temperature for 3 hours. Thereafter, 13.21 g (63.10 mmol) of terephthaloyl chloride (TPC) was added to the flask and stirred at room temperature for 1 hour. Next, 4.99 g (63.10 mmol) of pyridine and 21.91 g (214.66 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, and then heated to 70 ° C. using an oil bath. Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Example 2]
Except for changing the moisture content of DMAc of Example 1 to 100 ppm and changing the heating time after heating at 70 ° C. to 1 hour to obtain a polyamideimide resin, in the same manner as in Example 1, A polyamideimide film was obtained.

[Example 3]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 657.63 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 21.67 g (48.79 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added to the flask. (BPDA) 4.78 g (16.26 mmol) was added, and the mixture was stirred at room temperature for 3 hours. Thereafter, 19.81 g (97.57 mmol) of terephthaloyl chloride (TPC) was added to the flask and stirred at room temperature for 1 hour. Next, 7.49 g (94.65 mmol) of pyridine and 14.61 g (143.11 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Example 4]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 673.93 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 19.81 g (97.57 mmol) of terephthaloyl chloride (TPC) was added to the flask and stirred at room temperature for 1 hour. Next, 7.49 g (94.65 mmol) of pyridine and 14.61 g (143.11 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame and further dried at 230 ° C. for 30 minutes in the air to obtain a polyamideimide film having a thickness of 50 μm.

[Example 5]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 734.10 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 28.80 g (97.57 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) was added to the flask and stirred at room temperature for 1 hour. Next, 7.49 g (94.65 mmol) of pyridine and 14.61 g (143.11 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Example 6]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 734.10 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 28.80 g (97.57 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) was added to the flask and stirred at room temperature for 1 hour. Next, 7.49 g (94.65 mmol) of pyridine and 26.56 g (260.2 mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, and then heated to 70 ° C. using an oil bath. Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Example 7]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 667.75 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 21.67 g (48.79 mmol) of terephthaloyl chloride (TPC) 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Thereafter, 9.60 g (32.52 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) and 16.51 g (81.31 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. . Next, 8.73 g (110.42 mmol) of pyridine and 10.96 g (107.33 mmol) of acetic anhydride were added to the flask. After stirring for 30 minutes at room temperature, the temperature was raised to 70 ° C. using an oil bath. Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Comparative Example 1]
A polyamideimide film was obtained in the same manner as in Example 1 except that the polyamideimide resin was obtained by changing the stirring time after heating at 70 ° C. to 1 hour in Example 1.

[Comparative Example 2]
A polyamideimide film was obtained in the same manner as in Example 3 except that the polyamideimide resin was obtained by changing the stirring time after heating at 70 ° C. to 1 hour in Example 3.

[Comparative Example 3]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 831.46 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 72.24 g (162.62 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask and stirred at room temperature for 3 hours. Next, 6.43 g (81.31 mmol) of pyridine and 36.52 g (357.77 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyimide resin.
DMAc was added to the obtained polyimide resin so that a density | concentration might be 15 mass%, and the polyimide varnish was produced. The obtained polyimide varnish was applied on a smooth surface of a polyester base material (trade name “A4100” manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the free-standing film was 55 μm, and 50 ° C. for 30 minutes. Then, it was dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyimide film having a thickness of 50 μm.

[Comparative Example 4]
In a 1 L separable flask equipped with a stirring blade under a nitrogen atmosphere, 52 g (162.38 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethylacetamide having a water content adjusted to 500 ppm (DMAc) 733.51 g was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 28.90 g (65.05 mmol) of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride were added to the flask. (BPDA) 28.71g (97.57mmol) was added, and it stirred at room temperature for 3 hours. Next, 6.43 g (81.31 mmol) of pyridine and 36.52 g (357.77 mmol) of acetic anhydride were added to the flask, stirred for 30 minutes at room temperature, then heated to 70 ° C. using an oil bath, Stir for hours to obtain a reaction solution.
The obtained reaction solution was cooled to room temperature, poured into a large amount of methanol in the form of a thread, the deposited precipitate was taken out, immersed in methanol for 6 hours, and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyimide resin.
DMAc was added to the obtained polyimide resin so that a density | concentration might be 15 mass%, and the polyimide varnish was produced. The obtained polyimide varnish was applied on a smooth surface of a polyester base material (trade name “A4100” manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the free-standing film was 55 μm, and 50 ° C. for 30 minutes. Then, it was dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyimide film having a thickness of 50 μm.

[Comparative Example 5]
A polyamideimide film was obtained in the same manner as in Example 1 except that in Example 1, the moisture content of DMAc was changed to 1000 ppm to obtain a polyamideimide resin.

[Comparative Example 6]
A polyamideimide film was obtained in the same manner as in Example 1 except that the moisture content of DMAc was changed to 1700 ppm and the stirring time after heating at 70 ° C. was changed to 5 hours to obtain a polyamideimide resin. .

[Comparative Example 7]
In Example 5, a polyamideimide film was obtained in the same manner as in Example 5 except that the stirring time after heating at 70 ° C. was changed to 30 minutes to obtain a polyamideimide resin.

[Comparative Example 8]
In Example 7, the stirring time after heating at 70 ° C. was changed to 30 minutes, and a polyamideimide film was obtained in the same manner as in Example 7 except that a polyamideimide resin was obtained.

[Example 8]
In a 1 L separable flask equipped with a stirring blade under a nitrogen gas atmosphere, 45 g (140.5 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and N, N-dimethyl prepared with a water content of 200 ppm were prepared. 600.9 g of acetamide (DMAc) was added, and TFMB was dissolved in DMAc while stirring at room temperature. Next, 4.14 g (14.1 mmol) of 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride (BPDA) was added to the flask, and the mixture was stirred at room temperature for 2.5 hours. -(Hexafluoroisopropylidene) diphthalic dianhydride (6FDA) (25.01 g, 56.3 mmol) was added, and the mixture was stirred at room temperature for 15 hours. Further, 4.15 g (14.1 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) and 11.43 g (56.3 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. . Next, 21.55 g (211.1 mmol) of acetic anhydride and 3.28 g (35.2 mmol) of 4-picoline were added to the flask, stirred at room temperature for 30 minutes, then heated to 70 ° C. using an oil bath, The mixture was stirred for 3 hours to obtain a reaction solution.
After cooling the obtained reaction liquid to room temperature, 647 g of methanol and 180 g of ion-exchanged water were added to obtain a polyamideimide precipitate. It was immersed in methanol for 12 hours, recovered by filtration and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin. The molar ratio of each component is as shown in Table 1.
DMAc was added to the obtained polyamideimide resin so that the concentration was 15% by mass to prepare a polyamideimide varnish. The obtained polyamideimide varnish was coated on a smooth surface of a polyester base material (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using an applicator so that the film thickness of the self-supporting film became 55 μm, and the temperature was 50 ° C. And then dried at 140 ° C. for 15 minutes to obtain a self-supporting film. The self-supporting film was fixed to a metal frame, and further dried at 300 ° C. for 30 minutes in the air to obtain a polyamideimide film having a film thickness of 50 μm.

[Example 9]
In a 1 L separable flask equipped with a stirring blade under a nitrogen gas atmosphere, 14.67 g (45.8 mmol) of 2,2′-bis (trifluoromethyl) benzidine (TFMB) and a water content adjusted to 200 ppm were obtained. -233.3 g of dimethylacetamide (DMAc) was added and TFMB was dissolved in DMAc while stirring at room temperature. Next, 4.283 g (13.8 mmol) of 4,4′-oxydiphthalic dianhydride (OPDA) was added to the flask, and the mixture was stirred at room temperature for 16.5 hours. Thereafter, 1.359 g (4.61 mmol) of 4,4′-oxybis (benzoyl chloride) (OBBC) and 5.609 g (27.6 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. . Next, 4.937 g (48.35 mmol) of acetic anhydride and 1.501 g (16.12 mmol) of 4-picoline were added to the flask, stirred at room temperature for 30 minutes, heated to 70 ° C. using an oil bath, The mixture was stirred for 3 hours to obtain a reaction solution.
After cooling the obtained reaction liquid to room temperature, 360 g of methanol and 170 g of ion-exchanged water were added to obtain a polyamideimide precipitate. It was immersed in methanol for 12 hours, recovered by filtration and washed with methanol. Next, the precipitate was dried under reduced pressure at 100 ° C. to obtain a polyamideimide resin. The molar ratio of each component is as shown in Table 1.
In the same manner as in Example 8, a polyamideimide film having a thickness of 50 μm was obtained from the polyamideimide resin obtained in Example 9.

[Example 10]
Instead of 4.283 g of 4,4′-oxydiphthalic dianhydride (OPDA), 6.140 g of 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was converted into 2,2′-bis ( Trifluoromethyl) benzidine (TFMB) was changed to 14.67 g (45.8 mmol), but TFMB 8.809 g (27.5 mmol) and 2,2′-dimethylbenzidine (MB) 3.889 g (18.3 mmol) were used. Obtained a polyamideimide resin in the same manner as in Example 9. The molar ratio of each component is as shown in Table 1.
In the same manner as in Example 8, a polyamideimide film having a thickness of 50 μm was obtained from the polyamideimide resin obtained in Example 10.

[Example 11]
Polyamideimide was prepared in the same manner as in Example 9 except that 3.670 g (18.3 mmol) of 4,4′-diaminodiphenyl ether (ODA) was used instead of 3.889 g of 2,2′-dimethylbenzidine (MB). A resin was obtained. The molar ratio of each component is as shown in Table 1.
In the same manner as in Example 8, a polyamideimide film having a thickness of 50 μm was obtained from the polyamideimide resin obtained in Example 11.

The ratio of each structural unit and the synthesis conditions in the polyamideimide resin (B) contained in the polyamideimide varnish obtained in the above examples and the resin (B) contained in the varnish obtained in the comparative example are shown in Table 1 below. Table 1 also shows the results obtained by measuring the imidization ratio of the polyamideimide resin (B) and the resin (B) according to the measurement method. In Table 1, the imidization rate of the polyamideimide resin (B) and the resin (B) is “imidation rate B”, and the water content in the solvent at the start of the step (1) is “w [ppm]”. The heating time in the step (2) is “t [min]”, and the ratio of the molar amount of the dehydrating agent added in the step (2) to the molar amount of the tetracarboxylic dianhydride added in the step (1) is “ "Dehydrating agent addition amount". Here, in the measurement of the imidization ratio B of the polyimide resin B obtained in Comparative Examples 3 and 4, a polyimide resin B was prepared in the same manner as the polyamideimide resin B except that the resin was changed.

The results obtained by measuring the imidization rate of the polyamideimide resin (A) contained in the polyamideimide film obtained in the above examples and the resin (A) contained in the film obtained in the above comparative example according to the above measurement method 2 shows as “imidization ratio A”. Here, in the measurement of the imidization ratio of the polyimide resin A contained in the polyimide films obtained in Comparative Examples 3 and 4, a polyimide resin A was prepared in the same manner as the polyamideimide resin A except that the resin was changed. Furthermore, about the film obtained by the Example and the comparative example, according to the said measuring method, pencil hardness, yellowness (YI), total light transmittance (Tt), elastic modulus, and bending resistance (number of times of reciprocal bending) were measured. The obtained results are shown in Table 1. In addition, the ratio of the ratio of each structural unit in the polyamideimide resin (A) contained in the polyamideimide film and the resin (A) contained in the film obtained in the above comparative example corresponds to the polyamideimide shown in Table 1, respectively. It is the same as the ratio of the structural unit in resin (B) and resin (B). Moreover, in Example 10 and 11, it confirmed that the signal derived from the structure different from the repeating unit which has an amic acid, and the repeating unit which has an imide bond overlaps. For this reason, in the signal, the intensity of the non-overlapping part was integrated to obtain the original signal intensity from the area ratio of the part, and the imidization ratios A and B were calculated.

Claims

A polyamide having at least a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride and having an imidization ratio of 95% or more as measured by two-dimensional NMR A film containing imide resin A.
The diamine has the formula (3):

[In Formula (3), X is Formula (3e '):

[In the formula (3e ′), R 10 to R 17 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and are included in R 10 to R 17. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ] Is represented. ]
The film of Claim 1 containing the at least 1 sort (s) of compound represented by these.
The dicarboxylic acid has the formula (2):

[In Formula (2), Z represents Formula (2a) or Formula (2b)

Wherein (2a) and Formula (2b), U 1 represents a single bond, -O -, - CH 2 - , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3 ) 2 -, - Ar -, - SO 2 -, - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar-, —Ar—C (CH 3 ) 2 —Ar— or Ar—SO 2 —Ar— is represented, and * represents a bond. And B 1 and B 2 each independently represent OH or a halogen atom. ]
The film of Claim 1 or 2 containing the at least 1 sort (s) of compound represented by these.
Tetracarboxylic dianhydride has the formula (4):

[Wherein Y represents the formula (4g):

[In Formula (4g), W 1 represents a single bond, —C (CH 3 ) 2 — or C (CF 3 ) 2 —, and * represents a bond. ] Is represented. ]
The film according to any one of claims 1 to 3, comprising at least one compound represented by the formula:
The film according to claim 1, wherein the polyamideimide resin A contains a fluorine atom.
6. The film according to claim 1, which has a YI of 3 or less.
The film according to any one of claims 1 to 6, which has a pencil hardness of 3B or more as measured according to ASTM D 3363 under an illumination condition of 4000 lux.
Polyamideimide having a structural unit derived from diamine, a structural unit derived from dicarboxylic acid, and a structural unit derived from tetracarboxylic dianhydride and having an imidization ratio of 60% or more as measured by two-dimensional NMR A resin composition comprising at least a resin B and a solvent.
The diamine has the formula (3):

[In Formula (3), X is Formula (3e '):

[In the formula (3e ′), R 10 to R 17 each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an aryl group having 6 to 12 carbon atoms, and are included in R 10 to R 17. Each hydrogen atom may be independently substituted with a halogen atom, and * represents a bond. ] Is represented. ]
The resin composition of Claim 8 containing the at least 1 sort (s) of compound represented by these.
The dicarboxylic acid has the formula (2):

[In Formula (2), Z represents Formula (2a) or Formula (2b):

Wherein (2a) and Formula (2b), U 1 represents a single bond, -O -, - CH 2 - , - CH 2 -CH 2 -, - CH (CH 3) -, - C (CH 3) 2 -, - C (CF 3 ) 2 -, - Ar -, - SO 2 -, - CO -, - O-Ar-O -, - Ar-O-Ar -, - Ar-CH 2 -Ar-, —Ar—C (CH 3 ) 2 —Ar— or Ar—SO 2 —Ar— is represented, and * represents a bond. And B 1 and B 2 each independently represent OH or a halogen atom. ]
The resin composition of Claim 8 or 9 containing the at least 1 sort (s) of compound represented by these.
Tetracarboxylic dianhydride has the formula (4):

[In Formula (4), Y represents Formula (4g):

[In Formula (4g), W 1 represents a single bond, —C (CH 3 ) 2 — or C (CF 3 ) 2 —, and * represents a bond. ] Is represented. ]
The resin composition according to any one of claims 8 to 10, comprising at least one compound represented by the formula:
The resin composition according to claim 8, wherein the polyamideimide resin B contains a fluorine atom.
A film obtained by drying a coating film of the resin composition according to any one of claims 8 to 12.
(1) a step of copolymerizing diamine, dicarboxylic acid, and tetracarboxylic dianhydride in a solvent to obtain a polyamideimide resin precursor; and
(2) A method for producing a polyamideimide resin, comprising at least a step of adding a dehydrating agent and a tertiary amine to a solution containing at least a polyamideimide resin precursor and heating at a temperature of 70 to 120 ° C. When the amount of water in the solvent at the start of (1) is w (ppm) and the heating time in step (2) is t (minutes), w and t are the following formulas:

Satisfying the manufacturing method.
The manufacturing method according to claim 14, wherein the molar amount of the dehydrating agent added in the step (2) is at least twice the molar amount of the tetracarboxylic dianhydride added in the step (1).