JP2024017733A - Polyimide resin varnish and optical film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a varnish that prevents the gelation of a polyimide resin contained within it, and an optical film formed from the varnish.

SOLUTION: A polyimide resin varnish contains a polyimide resin, at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, and a solvent.

SELECTED DRAWING: None

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present invention relates to a polyimide resin varnish and an optical film formed from the varnish.

Currently, image display devices such as liquid crystal display devices and organic EL display devices are widely used not only in televisions but also in various applications such as mobile phones and smart watches. With the expansion of these applications, conventional rigid image display devices are being replaced by image display devices with flexible characteristics (sometimes called flexible displays), and even image display devices that can be folded (also called foldable displays). (sometimes referred to as rollable displays) and image display devices that can be rolled up and stored (sometimes called rollable displays) are being considered. An image display device includes a display element such as a liquid crystal display element or an organic EL display element, as well as constituent members such as a polarizing plate, a retardation plate, and a front plate.

In conventional rigid image display devices, glass has been used as the front plate. However, since glass is usually hard and easily broken, polyimide resins with protective functions and flexibility, as well as optical films using polyimide resins, have been considered as front panels for use in foldable displays, etc. (For example, Patent Document 1). Optical films using polyimide resins are usually manufactured from varnishes containing polyimide resins, and the long-term storage stability of the varnishes has also been studied (for example, Patent Document 2).

In addition, thin glass sheets that are made thinner so that they can be bent are also being considered. Such thin glass sheets are also required to have impact resistance and the ability to prevent scattering when broken.

Japanese Patent Application Publication No. 2017-203984 Japanese Patent Application Publication No. 2020-186369

When using a varnish containing a polyimide resin and a solvent, the resin in the varnish may gel during the storage period or film forming process. Conventionally, various studies have been made on polyimide resin films, but in some cases gelation of the polyimide resin in varnish cannot be sufficiently suppressed.

Therefore, an object of the present invention is to provide a varnish in which gelation of a polyimide resin in the varnish is suppressed, and an optical film formed from the varnish.

As a result of intensive studies to solve the above problems, the present inventors added at least one compound selected from the group consisting of urea compounds and cyclic amide compounds to a varnish containing a polyimide resin and a solvent. The inventors have discovered that the above-mentioned problems can be solved by including the above, and have completed the present invention.

［式（ａ１）および式（ａ２）中、Ｒ^ａ１～Ｒ^ａ６は、それぞれ独立に、水素原子または炭素数１～４のアルキル基を表し、ｍは１～４の整数を表す。］
で表される化合物である、〔１〕に記載のポリイミド系樹脂ワニス。
〔３〕環状アミド化合物は式（ｂ）：

［式（ｂ）中、Ｒ^ｂ１は炭素数１～６の２価の炭化水素基を表し、Ｒ^ｂ２は水素原子または炭素数１～６の１価の炭化水素基を表す］
で表される化合物である、〔１〕に記載のポリイミド系樹脂ワニス。
〔４〕ウレア系化合物は式（ａ１）で表される化合物である、〔２〕に記載のポリイミド系樹脂ワニス。
〔５〕ウレア系化合物および環状アミド化合物からなる群より選択される少なくとも１種の化合物の量は、ポリイミド系樹脂ワニスの総量に基づいて、１５質量％以下である、〔１〕～〔４〕のいずれかに記載のポリイミド系樹脂ワニス。
〔６〕ポリイミド系樹脂は、フッ素原子を有するポリアミドイミド樹脂である、〔１〕～〔５〕のいずれかに記載のポリイミド系樹脂ワニス。
〔７〕ポリイミド系樹脂は、式（１）：

［式（１）中、Ｙは４価の有機基を表し、Ｘは２価の有機基を表し、＊は結合手を表す］
で表される構成単位を含み、式（１）中のＹとして、式（２６）：

［式（２６）中、Ｗ^１は、単結合、－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－、－Ａｒ－ＳＯ_２－Ａｒ－または－ＣＯ－Ｏ－Ａｒ－Ｏ－ＣＯ－を表し、Ａｒは、水素原子が炭素数１～３のアルキル基またはフッ素原子で置換されていてもよい炭素数６～２０のアリーレン基を表し、＊は結合手を表す］
で表される基、および、式（２６）で表される基中の水素原子がメチル基、フルオロ基、クロロ基またはトリフルオロメチル基で置換された基からなる群より選択される少なくとも１つの基を含む、〔１〕～〔６〕のいずれかに記載のポリイミド系樹脂ワニス。
〔８〕光学フィルム製造用のワニスである、〔１〕～〔７〕のいずれかに記載のポリイミド系樹脂ワニス。
〔９〕光路長１０ｍｍにおける４０５ｎｍの透過率が１０％以上である、〔１〕～〔８〕のいずれかに記載のポリイミド系樹脂ワニス。
〔１０〕ポリイミド系樹脂は透明ポリイミド系樹脂である、〔１〕～〔９〕のいずれかに記載のポリイミド系樹脂ワニス。
〔１１〕〔１〕～〔１０〕のいずれかに記載のポリイミド系樹脂ワニスから形成された、光学フィルム。 That is, the present invention includes the following preferred embodiments.
[1] A polyimide resin varnish containing a polyimide resin, at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, and a solvent.
[2] The urea compound has formula (a1) or formula (a2):

[In formula (a1) and formula (a2), R ^a1 to R ^a6 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 4. ]
The polyimide resin varnish according to [1], which is a compound represented by:
[3] The cyclic amide compound has the formula (b):

[In formula (b), R ^b1 represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R ^b2 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms]
The polyimide resin varnish according to [1], which is a compound represented by:
[4] The polyimide resin varnish according to [2], wherein the urea compound is a compound represented by formula (a1).
[5] The amount of at least one compound selected from the group consisting of urea compounds and cyclic amide compounds is 15% by mass or less based on the total amount of the polyimide resin varnish, [1] to [4] The polyimide resin varnish according to any one of the above.
[6] The polyimide resin varnish according to any one of [1] to [5], wherein the polyimide resin is a polyamideimide resin having a fluorine atom.
[7] The polyimide resin has the formula (1):

[In formula (1), Y represents a tetravalent organic group, X represents a divalent organic group, and * represents a bond]
Formula (26) includes a structural unit represented by, and as Y in formula (1):

[In formula (26), W ¹ is 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-, -Ar-SO ₂ -Ar- or -CO-O-Ar-O-CO-, where Ar is a hydrogen atom substituted with an alkyl group having 1 to 3 carbon atoms or a fluorine atom represents an arylene group having 6 to 20 carbon atoms, and * represents a bond]
and at least one group selected from the group consisting of a group represented by formula (26) in which a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group. The polyimide resin varnish according to any one of [1] to [6], which contains a group.
[8] The polyimide resin varnish according to any one of [1] to [7], which is a varnish for producing an optical film.
[9] The polyimide resin varnish according to any one of [1] to [8], which has a transmittance of 10% or more at 405 nm at an optical path length of 10 mm.
[10] The polyimide resin varnish according to any one of [1] to [9], wherein the polyimide resin is a transparent polyimide resin.
[11] An optical film formed from the polyimide resin varnish according to any one of [1] to [10].

According to the present invention, it is possible to provide a varnish in which gelation of a polyimide resin in the varnish is suppressed, and an optical film formed from the varnish.

Embodiments of the present invention will be described in detail below. Note that the scope of the present invention is not limited to the embodiments described here, and various changes can be made without departing from the spirit of the present invention. Further, when a plurality of upper and lower limit values are described for a specific parameter, any of these upper and lower limit values can be combined to form a suitable numerical range.

The varnish of the present invention is a polyimide resin varnish containing a polyimide resin, at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, and a solvent. The varnish containing a polyimide resin and a solvent further contains at least one compound selected from the group consisting of a urea compound and a cyclic amide compound, thereby suppressing gelation of the polyimide resin in the varnish. It turned out that it is possible. When a film is manufactured from a varnish containing gelled resin, the thickness and physical properties of the film may become non-uniform, the optical properties may deteriorate, and the quality of the film may be adversely affected. Additionally, when manufacturing films from polyimide resin varnish, a process is usually performed to filter the varnish, but if the varnish contains gelled resin, clogging may occur during the filtration process, reducing production efficiency. In some cases, a pressurizing device is required for filtration, and the resin content in the varnish and the composition of the varnish vary due to removal of gelled resin. Such gels tend to form, for example, when varnishes are stored for a certain period of time. It can also occur when external force is applied to the varnish during the process of filtering the varnish during film production. According to the varnish of the present invention, it is possible to suppress the formation of such a gel, and it is possible to produce an optical film with excellent uniformity.

The reason why gel formation can be suppressed in a varnish containing a polyimide resin by including at least one compound selected from the group consisting of a urea compound and a cyclic amide compound is not clear, but for example, the following mechanism may be considered. is possible. When gel is generated in the above varnish, interactions between molecular chains of the polyimide resin, such as interactions due to hydrogen bonds between amic acid structure parts or amide structure parts of adjacent molecular chains, occur, and the polyimide resin It is thought that a phenomenon in which some of the objects are stacked is occurring. Furthermore, in the step of filtering the varnish, it is thought that by applying an external force to the varnish during filtration, the interaction between the molecular chains of the polyimide resin may increase, and gel formation may be promoted. When at least one compound selected from the group consisting of urea compounds and cyclic amide compounds is contained in the varnish, they can interact with the amide structure portion of the polyimide resin. As a result, stacking between molecular chains, which causes gel formation as described above, is suppressed, and gelation is thought to be suppressed. The urea compound has two nitrogen atoms bonded via carbonyl carbon, and these are thought to form a hydrogen bond with the amic acid structure or amide structure of the polyimide resin. Such two nitrogen atoms are preferably tertiary nitrogen atoms. The cyclic amide compound has a nitrogen atom, preferably a tertiary nitrogen atom, incorporated into the cyclic structure, and is thought to similarly interact with the polyimide resin to suppress gelation. Note that the present invention is not limited in any way by the above mechanism.

<Urea compounds and cyclic amide compounds>
The varnish of the present invention contains at least one compound selected from the group consisting of urea compounds and cyclic amide compounds.

［式（ａ１）および式（ａ２）中、Ｒ^ａ１～Ｒ^ａ６は、それぞれ独立に、水素原子または炭素数１～４のアルキル基を表し、ｍは１～４の整数を表す。］
で表される化合物であり、より好ましくは式（ａ１）で表される化合物である。 From the viewpoint of easily preventing interaction between molecular chains of the polyimide resin and easily suppressing gelation, the urea-based compound preferably has the formula (a1) or (a2):

[In formula (a1) and formula (a2), R ^a1 to R ^a6 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 4. ]
It is a compound represented by formula (a1), and more preferably a compound represented by formula (a1).

In formulas (a1) and (a2), R ^a1 to R ^a6 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, preferably an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, and butyl group. m in formula (a2) represents an integer of 1 to 4, preferably 2 or 3, more preferably 2.

Specifically, the compound represented by formula (a1) includes tetramethylurea, tetraethylurea, tetrapropylurea, tetraisopropylurea, tetrabutylurea, N,N'-dimethylurea, N,N'-diethyl Examples include urea, N,N'-dipropylurea, N,N'-diisopropylurea, and N,N'-dibutylurea. The compound represented by formula (a1) is preferably tetramethylurea. Specific examples of the compound represented by formula (a2) include 2-imidazolidinone, trimethyleneurea, tetramethyleneurea, 1,3-dimethyl-2-imidazolidinone, and N,N'-dimethyltridinone. Examples include methylene urea, N,N'-dimethyltetramethylene urea, 2-imidazolone, 1-methyl-2-imidazolone, 1,3-dimethyl-2-imidazolone, and the like. The compound represented by formula (a2) is preferably 1,3-dimethyl-2-imidazolidinone.

［式（ｂ）中、Ｒ^ｂ１は炭素数１～６の２価の炭化水素基を表し、Ｒ^ｂ２は水素原子または炭素数１～６の１価の炭化水素基を表す］
で表される化合物である。 From the viewpoint of easily preventing interaction between molecular chains of polyimide resin and easily suppressing gelation, the cyclic amide compound has the formula (b):

[In formula (b), R ^b1 represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R ^b2 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms]
It is a compound represented by

In formula (b), R ^b1 represents a divalent hydrocarbon group having 1 to 6 carbon atoms. Examples of the divalent hydrocarbon group having 1 to 6 carbon atoms include alkylene groups having 1 to 6 carbon atoms. The alkylene group having 1 to 6 carbon atoms may be a linear or branched alkylene group, such as a methylene group, ethylene group, propylene group, methylpropylene group, n-butylene group, ethylpropylene group, pentylene group. , heptylene group. From the viewpoint of easily increasing the stability of the compound represented by formula (b), R ^b1 is an alkylene group having 1 to 6 carbon atoms, and the compound represented by formula (b) is a 5- to 6-membered ring. Preferably, it is a group that forms. From this point of view, it is more preferable to use, for example, a propylene group, methylpropylene group, ethylpropylene group, n-butylene group, methylbutylene group, or ethylbutylene group.

In formula (b), R ^b2 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms. Examples of monovalent hydrocarbon groups having 1 to 6 carbon atoms include alkyl groups having 1 to 6 carbon atoms, unsaturated chain hydrocarbon groups having 2 to 4 carbon atoms, and cyclic hydrocarbon groups having 4 to 6 carbon atoms. Examples include groups. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, propyl group, isopropyl group, butyl group, isobutyl group, pentyl group, and heptyl group. Examples of the unsaturated chain hydrocarbon group having 2 to 4 carbon atoms include a vinyl group and an allyl group. Examples of the cyclic hydrocarbon group having 3 to 6 carbon atoms include a cyclohexyl group and a phenyl group. R ^b2 is preferably an alkyl group having 1 to 6 carbon atoms. The number of carbon atoms in R ^b2 is preferably 1 to 4, more preferably 1 to 3, and still more preferably 1 to 2.

Specifically, the compound represented by formula (b) includes N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, N-isopropyl-2-pyrrolidone, N- -methyl-2-piperidone and the like. From the viewpoint of more easily suppressing gelation, the compound represented by formula (b) is preferably N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-propyl-2-pyrrolidone, and N-propyl-2-pyrrolidone. -isopropyl-2-pyrrolidone, more preferably N-ethyl-2-pyrrolidone and N-isopropyl-2-pyrrolidone.

When the polyimide resin varnish of the present invention contains at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, the content is determined by the yellowness of the polyimide resin film formed from the varnish. From the viewpoint of easily suppressing and increasing transparency, based on the total amount of the polyimide resin varnish, preferably 15% by mass or less, more preferably 12% by mass or less, still more preferably 10% by mass or less, and The content is more preferably 9% by mass or less, particularly preferably 8% by mass or less, particularly preferably 7% by mass or less. In addition, the content of at least one compound selected from the group consisting of urea compounds and cyclic amide compounds is determined based on the total amount of the polyimide resin varnish, from the viewpoint of easily suppressing gelation of the polyimide resin in the varnish. , preferably 0.5% by mass or more, more preferably 1.0% by mass or more, still more preferably 1.5% by mass or more, even more preferably 2.0% by mass or more.

The content of at least one compound selected from the group consisting of urea compounds and cyclic amide compounds contained in the varnish is determined from the viewpoint of easily suppressing gelation of the polyimide resin in the varnish and increasing the yellowness of the polyimide resin film. From the viewpoint of easy suppression, the amount of polyimide resin contained in the polyimide resin varnish is preferably 1 to 200 parts by mass, more preferably 3 to 150 parts by mass, and still more preferably 5 to 120 parts by mass. , and even more preferably 10 to 100 parts by mass.

The content of at least one compound selected from the group consisting of urea compounds and cyclic amide compounds contained in the varnish is determined from the viewpoint of easily suppressing gelation of the polyimide resin in the varnish and increasing the yellowness of the polyimide resin film. From the viewpoint of easy suppression, preferably 0.5 to 15 parts by mass, more preferably 1 to 12 parts by mass, and Preferably it is 1.5 to 10 parts by weight, even more preferably 2 to 8 parts by weight.

<Polyimide resin>
The varnish of the present invention contains a polyimide resin. The polyimide resin is a polyimide resin, a polyamideimide resin, or a polyamic acid resin which is a precursor of a polyimide resin and a polyamideimide resin. The varnish of the present invention may contain one type of polyimide resin, or may contain two or more types of polyimide resin. The polyimide resin is preferably a polyimide resin or a polyamide-imide resin, more preferably a polyamide-imide resin, from the viewpoint of easily suppressing gelation of the polyimide resin in the varnish and from the viewpoint of film-forming properties. Further, from the same viewpoint, the polyimide resin is preferably a polyimide resin having a fluorine atom, more preferably a polyimide resin or a polyamideimide resin having a fluorine atom, and still more preferably a polyamideimide resin having a fluorine atom. It is.

The polyimide resin contained in the varnish of the present invention preferably has a polystyrene equivalent weight average molecular weight of 100,000 or more, from the viewpoint of improving the dent resistance of the film, suppressing yellowing over time, and improving bending resistance. More preferably 130,000 or more, still more preferably 150,000 or more, even more preferably 200,000 or more. The polystyrene equivalent weight average molecular weight of the polyimide resin is preferable from the viewpoints of ease of manufacturing the varnish, suppression of gelation of the varnish, film formability when manufacturing a polymeric material, and reduction of yellowness of the resulting film. is 800,000 or less, more preferably 600,000 or less, even more preferably 500,000 or less, even more preferably 450,000 or less, particularly preferably 400,000 or less. The weight average molecular weight is measured by gel permeation chromatography (GPC). As the measurement conditions, the conditions described in Examples may be used.

［式（１）中、Ｘは２価の有機基を表し、Ｙは４価の有機基を表し、＊は結合手を表す］
で表される構成単位を含むポリイミド樹脂であるか、または、式（１）で表される構成単位および式（２）：

［式（２）中、ＸおよびＺは、互いに独立に、２価の有機基を表し、＊は結合手を表す］
で表される構成単位を含むポリアミドイミド樹脂であることが好ましい。ポリイミド系樹脂は、ワニスのゲル化抑制、フィルムの耐凹み性の向上、透明性や屈曲性の観点、および、フィルムの黄変抑制の観点から、式（１）で表される構成単位および式（２）で表される構成単位を有するポリアミドイミド樹脂であることがより好ましい。以下において式（１）および式（２）について説明するが、式（１）についての説明は、ポリイミド樹脂およびポリアミドイミド樹脂の両方に関し、式（２）についての説明は、ポリアミドイミド樹脂に関する。 In one embodiment of the present invention, the polyimide resin has the formula (1):

[In formula (1), X represents a divalent organic group, Y represents a tetravalent organic group, and * represents a bond]
A polyimide resin containing a structural unit represented by, or a structural unit represented by formula (1) and formula (2):

[In formula (2), X and Z independently represent a divalent organic group, and * represents a bond]
It is preferable that it is a polyamideimide resin containing a structural unit represented by the following. Polyimide resins contain the structural unit and formula represented by formula (1) from the viewpoint of suppressing gelation of varnish, improving dent resistance of film, transparency and flexibility, and suppressing yellowing of film. A polyamide-imide resin having a structural unit represented by (2) is more preferable. Formula (1) and Formula (2) will be explained below, and the explanation about Formula (1) relates to both polyimide resin and polyamideimide resin, and the explanation about Formula (2) relates to polyamideimide resin.

The structural unit represented by formula (1) is a structural unit formed by the reaction of a tetracarboxylic acid compound and a diamine compound, and the structural unit represented by formula (2) is a structural unit formed by a reaction between a dicarboxylic acid compound and a diamine compound. It is a structural unit formed by the reaction of

The polyimide resin is a polyimide resin having a constitutional unit represented by formula (1), or a polyamide-imide having a constitutional unit represented by formula (1) and a constitutional unit represented by formula (2). In one embodiment of the present invention that is a resin, Y in formula (1) independently represents a tetravalent organic group, preferably a tetravalent organic group having 4 to 40 carbon atoms. The organic group is 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 number of carbon atoms is preferably 1 to 8. The polyimide resin, which is an embodiment of the present invention, may contain one type of Y, or may contain multiple types of Y. In other words, the plurality of Y contained in the polyimide resin are: They may be the same or different. Y in formula (1) is formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), A group represented by formula (28) or formula (29); a hydrogen atom in the group represented by formula (20) to formula (29) is substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group; and a tetravalent chain hydrocarbon group having 6 or less carbon atoms.

[In formulas (20) to (29), * represents a bond,
W ¹ is 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- , -Ar-SO ₂ -Ar- or -CO-O-Ar-O-CO-. Ar represents an arylene group having 6 to 20 carbon atoms in which the hydrogen atom may be substituted with an alkyl group having 1 to 3 carbon atoms or a fluorine atom, and specific examples include a phenylene group or a biphenylene group. ]

In formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) and formula (29), Among the groups represented, groups represented by formula (26), formula (28) or formula (29), and their At least one group selected from the group consisting of groups in which a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group is preferred. In addition, from the viewpoint of reducing yellowness, improving dent resistance, and flexibility, groups represented by formulas (20) to (27) and hydrogen atoms in these groups are methyl groups, fluoro groups, At least one group selected from the group consisting of a group substituted with a chloro group or a trifluoromethyl group is preferable, and a group represented by formula (26) and hydrogen in the group represented by formula (26) are preferable. At least one group selected from the group consisting of a group in which an atom is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group is more preferable, and a group represented by formula (26) is even more preferable. In addition, from the viewpoints of suppressing gelation of the varnish containing the polyimide resin, reducing the yellowness of the film formed from the varnish, improving dent resistance, and improving surface hardness and flexibility, W ¹ is determined independently from the single bond. , -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ -, preferably a single A bond, -O-, -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - is more preferable, and a single bond, -O-, -C(CH ₃ ) ₂ - or -C(CF ₃ ) ₂ - is more preferred, and -O- or -C(CF ₃ ) ₂ - is even more preferred.

［式（５）中、Ｒ^１８～Ｒ^２５は、互いに独立に、水素原子、炭素数１～６のアルキル基または炭素数６～１２のアリール基を表し、Ｒ^１８～Ｒ^２５に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
＊は結合手を表す。］ In the above embodiment, it is more preferable that at least some of the plurality of Y's in formula (1) are groups represented by formula (5). When at least a part of the plurality of Y in formula (1) is a group represented by formula (5), the film formed from the varnish containing the polyimide resin exhibits high dent resistance and high transparency. It's easy to do. In addition, due to the highly flexible skeleton, the solubility of the polyimide resin in solvents can be improved, the viscosity of the varnish can be kept low, gelation can be easily prevented, and the film can be easily processed. In addition, it is easy to improve the optical properties of the resulting film.

[In formula (5), R ¹⁸ to R ²⁵ 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 hydrogen contained in R ¹⁸ to R ²⁵ The atoms may be substituted independently of each other with halogen atoms,
* represents a bond. ]

In formula (5), R ¹⁸ , R ¹⁹ , R ²⁰ , R ²¹ , R ²² , R ²³ , R ²⁴ , and R ²⁵ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a C 6 alkyl group. -12 aryl group, preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in formula (3). Examples of the group or aryl group having 6 to 12 carbon atoms include those mentioned below. Here, the hydrogen atoms contained in R ¹⁸ to R ²⁵ may be independently substituted with halogen atoms. R ¹⁸ to R ²⁵ independently represent a hydrogen atom, a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group, from the viewpoint of surface hardness and flexibility of the film containing the polyimide resin. A hydrogen atom or a trifluoromethyl group is particularly preferred.

［式（５’）中、＊は結合手を表す］ In a preferred embodiment of the present invention, the group represented by formula (5) is a group represented by formula (5'), that is, at least some of the plurality of Y's are represented by formula (5'). It is a group represented by In this case, it is easy to suppress gelation of the varnish containing the polyimide resin, and it is easy to increase the transparency of the film formed from the varnish.

[In formula (5'), * represents a bond]

In a preferred embodiment of the present invention, preferably 50 mol% or more, more preferably 60 mol% or more, even more preferably 70 mol% or more of Y in the polyimide resin is represented by formula (26), preferably formula (5), especially expressed by formula (5'). When Y within the above range in the polyimide resin is represented by formula (26), preferably formula (5), particularly formula (5'), the film containing the polyimide resin has high transparency. be able to. In addition, since the solubility of the polyimide resin is improved when the fluorine element is contained, the viscosity of the varnish containing the polyimide resin is suppressed to a low level, making it easier to manufacture a film. Preferably, 100 mol% or less of Y in the polyimide resin is represented by formula (26), preferably formula (5), particularly formula (5'). Y in the polyimide resin may be represented by formula (26), preferably formula (5), particularly formula (5'). The content of the structural unit represented by formula (26), formula (5), or formula (5') of Y in the polyimide resin can be measured using, for example, ¹ H-NMR, or It can also be calculated from the preparation ratio.

In one embodiment of the present invention, where the polyimide resin is a polyamide-imide resin having a structural unit represented by formula (1) and a structural unit represented by formula (2), Z in formula (2) is independent of each other. represents a divalent organic group. In one embodiment of the present invention, the polyamide-imide resin may contain one type of Z, or may contain multiple types of Z, that is, the plurality of Z contained in the polyamide-imide resin are the same as each other. may be different. The divalent organic group preferably represents a divalent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, in which case the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. Examples of the organic group of Z include formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), and formula (28). ) or a group in which two non-adjacent bonds of the group represented by formula (29) are replaced with hydrogen atoms, and a divalent chain hydrocarbon group having 6 or less carbon atoms are exemplified. From the viewpoint of improving the optical properties of the film, for example, easily reducing the YI value, formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26) ) or a group represented by a group in which two non-adjacent bonds of the group represented by formula (27) are replaced with hydrogen atoms. In one embodiment of the present invention, the polyamide-imide resin may contain one type of organic group as Z, or may contain two or more types of organic groups.

［式（２０’）～式（２９’）中、Ｗ^１および＊は、式（２０）～式（２９）において定義する通りである］
で表される２価の有機基がより好ましい。なお、式（２０）～式（２９）および式（２０’）～式（２９’）における環上の水素原子は、炭素数１～８の炭化水素基、フッ素置換された炭素数１～８の炭化水素基、炭素数１～６のアルコキシ基、フッ素置換された炭素数１～６のアルコキシ基で置換されていてもよい。 Examples of the organic group of Z include formula (20'), formula (21'), formula (22'), formula (23'), formula (24'), formula (25'), formula (26'), and formula (27'), formula (28') and formula (29'):

[In formulas (20') to (29'), W ¹ and * are as defined in formulas (20) to (29)]
A divalent organic group represented by is more preferred. In addition, the hydrogen atom on the ring in formulas (20) to (29) and formulas (20') to (29') is a hydrocarbon group having 1 to 8 carbon atoms, or a fluorine-substituted group having 1 to 8 carbon atoms. may be substituted with a hydrocarbon group, an alkoxy group having 1 to 6 carbon atoms, or a fluorine-substituted alkoxy group having 1 to 6 carbon atoms.

［式（ｄ１）中、Ｒ^２４は、互いに独立に、水素原子、ハロゲン原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基または炭素数６～１２のアリール基を表し、Ｒ^２５は、Ｒ^２４または－Ｃ（＝Ｏ）－＊を表し、＊は結合手を表す］
で表されるカルボン酸由来の構成単位をさらに有すると、ワニスの粘度を低くしやすくなる傾向がある。ワニスの粘度が低い場合、ポリイミド系樹脂のゲル化が抑制されやすいため、得られるフィルムの均一性を高めやすい。 When the polyamide-imide resin has a structural unit in which Z in formula (2) is represented by any of the above formulas (20') to (29'), the polyamide-imide resin has, in addition to the structural unit, , the following formula (d1):

[In formula (d1), R ²⁴ independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, R ²⁵ represents R ²⁴ or -C(=O)-*, * represents a bond]
When the varnish further contains a structural unit derived from a carboxylic acid represented by the above formula, the viscosity of the varnish tends to be lowered. When the viscosity of the varnish is low, gelation of the polyimide resin is likely to be suppressed, so the uniformity of the resulting film is likely to be improved.

In R ²⁴ , the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, and the aryl group having 6 to 12 carbon atoms are exemplified with respect to R ¹ to R ⁸ in formula (3) described below, respectively. Examples include: Specifically, the structural unit (d1) includes a structural unit in which R ²⁴ and R ²⁵ are both hydrogen atoms (a structural unit derived from a dicarboxylic acid compound), a structural unit in which R ²⁴ is both a hydrogen atom, and R ²⁵ Examples include a structural unit in which -C(=O)-* (a structural unit derived from a tricarboxylic acid compound).

［式（３ａ）中、Ｒ^ｇおよびＲ^ｈは、互いに独立に、ハロゲン原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、または炭素数６～１２のアリール基を表し、Ｒ^ｇおよびＲ^ｈに含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、Ａ、ｍおよび＊は式（３）中のＡ、ｍおよび＊と同じであり、ｔおよびｕは互いに独立に０～４の整数である］
で表されることが好ましく、式（３）：

［式（３）中、Ｒ^１～Ｒ^８は、互いに独立に、水素原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、または炭素数６～１２のアリール基を表し、Ｒ^１～Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、互いに独立に、単結合、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＳＯ_２－、－Ｓ－、－ＣＯ－または－Ｎ（Ｒ^９）－を表し、Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１～１２の１価の炭化水素基を表し、
ｍは０～４の整数であり、
＊は結合手を表す］
で表されることがより好ましい。 In one embodiment of the present invention, the polyamide-imide resin may contain one type of Z, or may contain multiple types of Z, that is, the plurality of Z contained in the polyamide-imide resin may be mutually They may be the same or different. In particular, from the viewpoint of easily preventing gelation of the varnish and from the viewpoint of easily improving the surface hardness and optical properties of the obtained film, at least a part of Z is represented by the formula (3a):

[In formula (3a), R ^g and R ^h independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms; , R ^g and R ^h may be independently substituted with a halogen atom, A, m and * are the same as A, m and * in formula (3), and t and u are mutually independent integers from 0 to 4]
It is preferably represented by the formula (3):

[In formula (3), R ¹ to R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. , the hydrogen atoms contained in R ¹ to R ⁸ may be independently substituted with halogen atoms,
A is, independently of each other, a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, where R ⁹ is a monovalent group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom. represents a hydrocarbon group,
m is an integer from 0 to 4,
*represents a bond]
It is more preferable to express it as follows.

In formula (3) and formula (3a), A independently represents a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) _2- , -C(CF ₃ ) ₂ -, -SO ₂ -, -S-, -CO- or -N(R ⁹ )-, preferably from the viewpoint of bending resistance of the obtained film It represents -O- or S-, more preferably -O-.
R ¹ , R ² , R ³ , R ⁴ , R ⁵ , R ⁶ , R ⁷ and R ⁸ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, Or represents an aryl group having 6 to 12 carbon atoms. R ^g and R ^h each independently represent a halogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, 2-methyl- Examples include butyl group, 3-methylbutyl group, n-hexyl group, and the like. Examples of the alkoxy group having 1 to 6 carbon atoms include methoxy group, ethoxy group, propyloxy group, isopropyloxy group, butoxy group, isobutoxy group, tert-butoxy group, pentyloxy group, hexyloxy group, cyclohexyloxy group, etc. Can be mentioned. Examples of the aryl group having 6 to 12 carbon atoms include phenyl group, tolyl group, xylyl group, naphthyl group, and biphenyl group. From the viewpoint of the surface hardness and flexibility of the film obtained from the varnish, R ¹ to R ⁸ each independently preferably represent a hydrogen atom or an alkyl group having 1 to 6 carbon atoms, and more preferably a hydrogen atom or an alkyl group having 1 to 6 carbon atoms. It represents 1 to 3 alkyl groups, and more preferably represents a hydrogen atom. Here, the hydrogen atoms contained in R ¹ to R ⁸ , R ^g and R ^h may be independently substituted with a halogen atom.
R ⁹ represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of monovalent hydrocarbon groups having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, tert-butyl group, n-pentyl group, Examples include 2-methyl-butyl group, 3-methylbutyl group, n-hexyl group, n-heptyl group, n-octyl group, tert-octyl group, n-nonyl group, n-decyl group, etc., which are halogen atoms. may be replaced with . Examples of the halogen atom include a fluorine atom and a chlorine atom. The polyimide-based resin may contain one type of A, or may contain multiple types of A. In other words, the plurality of A's contained in the polyamide-imide resin may be the same or different. You can.

t and u in formula (3a) are each independently an integer of 0 to 4, preferably an integer of 0 to 2, more preferably 0 or 1, and even more preferably 0.

In formula (3) and formula (3a), m is an integer in the range of 0 to 4, and when m is within this range, gelation of the polyimide resin in the varnish can be easily suppressed, and the The film obtained from the varnish tends to have good bending resistance and elastic modulus. Furthermore, in formula (3) and formula (3a), m is preferably an integer in the range of 0 to 3, more preferably an integer in the range of 0 to 2, still more preferably 0 or 1, and even more preferably 0. be. When m is within this range, the bending resistance and elastic modulus of the film can be easily improved. Further, Z may contain one or more types of structural units represented by formula (3) or formula (3a), which suppresses gelation of the polyimide resin in the varnish and improves the elasticity of the resulting film. In particular, from the viewpoint of improving the elasticity and bending resistance, reducing the YI value, and suppressing yellowing of the film, a configuration of two or more types of structural units with different m values, preferably two or three types of structural units with different m values. May include units. In that case, from the viewpoint of suppressing gelation of the polyimide resin in the varnish, and from the viewpoint of facilitating the development of high elastic modulus, bending resistance, and low YI value of the film obtained from the varnish, the resin may be It is preferable to contain a structural unit represented by formula (3) or formula (3a) where m is 0, and in addition to the structural unit, m is 1. It is more preferable to further contain a unit. Further, in addition to the structural unit represented by formula (2) having Z represented by formula (3) where m is 0, it is also preferable to further have a structural unit represented by formula (d1) above. .

In a preferred embodiment of the present invention, the resin has m=0 as a structural unit represented by formula (3), and R ⁵ to R ⁸ each independently represent a hydrogen atom, a carbon number of 1 to It has a structural unit that is an alkyl group having 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms.
In a more preferred embodiment of the present invention, in the resin, as a structural unit represented by formula (3), m is 0, and R ⁵ to R ⁸ each independently represent a hydrogen atom, a carbon number of 1 It has a structural unit that is an alkyl group having 1 to 6 carbon atoms or an alkoxy group having 1 to 6 carbon atoms. In this case, it is easier to improve the dent resistance of the film of the present invention.

で表される構成単位を有していてもよい。この場合、フィルムの表面硬度および耐屈曲性を向上させやすく、ＹＩ値を低減しやすい。 In another preferred embodiment of the present invention, the polyimide resin includes a structural unit represented by formula (3) in which m=0 and R ⁵ to R ⁸ are hydrogen atoms; , formula (3'):

It may have a structural unit represented by. In this case, it is easy to improve the surface hardness and bending resistance of the film, and it is easy to reduce the YI value.

In a preferred embodiment of the present invention, when the total of the structural units represented by the formula (1) and the structural units represented by the formula (2) of the polyamide-imide resin is 100 mol%, the formula (3) or The proportion of the structural unit represented by formula (3a) is preferably 20 mol% or more, more preferably 30 mol% or more, even more preferably 40 mol% or more, even more preferably 50 mol% or more, particularly preferably 60 mol% or more. It is mol% or more, preferably 90 mol% or less, more preferably 85 mol% or less, still more preferably 80 mol% or less, even more preferably 75 mol% or less. When the proportion of the structural unit represented by formula (3) or formula (3a) is at least the above lower limit, gelation of the polyimide resin in the varnish can be easily suppressed, and the surface hardness of the film obtained from the varnish can be reduced. It is easy to increase the bending resistance and elastic modulus. When the proportion of the structural units represented by formula (3) or formula (3a) is below the above upper limit, the polyimide system in the varnish due to hydrogen bonding between amide bonds derived from formula (3) or formula (3a) Easily suppresses resin gelation and improves film processability.

In addition, when the polyamide-imide resin has a structural unit of formula (3) or formula (3a) where m = 1 to 4, the polyamide-imide resin has a structural unit represented by formula (1) and a structural unit represented by formula (2). The proportion of the structural units of formula (3) or formula (3a) in which m is 1 to 4 is preferably 2 mol% or more, more preferably 4 mol%, when the total of the structural units is 100 mol%. % or more, more preferably 6 mol% or more, even more preferably 8 mol% or more, preferably 70 mol% or less, more preferably 50 mol% or less, still more preferably 30 mol% or less, even more preferably 15 mol% or more. The amount is not more than 12% by mole, particularly preferably not more than 12% by mole. When the proportion of the structural unit of formula (3) or formula (3a) in which m is 1 to 4 is equal to or higher than the above lower limit, gelation of the polyimide resin in the varnish can be easily suppressed, and the polyimide resin obtained from the varnish can be easily suppressed. It is easy to increase the surface hardness and bending resistance of the film. If the proportion of the structural units of formula (3) or formula (3a) in which m is 1 to 4 is below the above upper limit, hydrogen bonding between amide bonds derived from formula (3) or formula (3a) may occur in the varnish. It is easy to suppress the gelation of the polyimide resin in the process, and it is also easy to improve the processability of the film. Note that the content of the structural unit represented by formula (1), formula (2), formula (3), or formula (3a) can be measured using, for example, ¹ H-NMR, or by It can also be calculated from the ratio.

In a preferred embodiment of the present invention, Z in the polyamide-imide resin preferably contains 30 mol% or more, more preferably 40 mol% or more, still more preferably 45 mol% or more, even more preferably 50 mol% or more, Particularly preferably 70 mol% or more is a structural unit represented by formula (3) or formula (3a), where m is 0 to 4. When the above lower limit or more of Z is a structural unit represented by formula (3) or formula (3a) where m is 0 to 4, gelation of the polyimide resin in the varnish can be easily suppressed, and It is easy to increase the surface hardness of the film obtained from the varnish, and it is also easy to increase the bending resistance and elastic modulus. Further, it is sufficient if 100 mol% or less of Z in the polyamide-imide resin is a structural unit represented by formula (3) or formula (3a) where m is 0 to 4. Note that the proportion of the structural unit represented by formula (3) or formula (3a) in which m is 0 to 4 in the resin can be measured using, for example, ¹ H-NMR, or by It can also be calculated from the ratio.

In a preferred embodiment of the present invention, Z in the polyamideimide resin preferably accounts for 5 mol% or more, more preferably 8 mol% or more, still more preferably 10 mol% or more, and even more preferably 12 mol% or more. , m is represented by formula (3) or formula (3a), where m is 1 to 4. When the above lower limit of Z of the polyamide-imide resin or more is represented by formula (3) or formula (3a) where m is 1 to 4, gelation of the polyimide resin in the varnish can be easily suppressed, and It is easy to increase the surface hardness of the film obtained from the varnish, and it is also easy to increase the bending resistance and elastic modulus. Further, preferably 90 mol% or less, more preferably 70 mol% or less, still more preferably 50 mol% or less, and even more preferably 30 mol% or less of Z is a compound of formula (3) in which m is 1 to 4 or It is preferably represented by formula (3a). When below the above upper limit of Z is represented by formula (3) or formula (3a) where m is 1 to 4, an amide bond derived from formula (3) or formula (3a) where m is 1 to 4 It is easy to suppress the increase in viscosity of the resin-containing varnish due to hydrogen bonds between the two, and it is easy to suppress the gelation of the polyimide resin in the varnish, and it is easy to improve the processability of the film. Note that the proportion of the structural unit represented by formula (3) or formula (3a) in which m is 1 to 4 in the resin can be measured using, for example, ¹ H-NMR, or it can be determined from the charging ratio of raw materials. It can also be calculated.

In formula (1) and formula (2), X independently represents a divalent organic group, preferably a divalent organic group having 4 to 40 carbon atoms, more preferably a C4 organic group having a cyclic structure. Represents ~40 divalent organic groups. Examples of the cyclic structure include an alicyclic ring, an aromatic ring, and a heterocyclic structure. In the organic group, a hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in that case, the number of carbon atoms in the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably is 1 to 8. In one embodiment of the present invention, the polyimide resin or polyamideimide resin may contain one type of X, or may contain multiple types of X, that is, the plurality of X contained in the resin is , may be the same or different from each other. X is expressed by formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17), and formula (18). groups; groups in which the hydrogen atom in the groups represented by formulas (10) to (18) is substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group; and groups having 6 or less carbon atoms; A chain hydrocarbon group is exemplified.

In formulas (10) to (18), * represents a bond,
V ¹ , V ² and V ³ each independently represent a single bond, -O-, -S-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) represents _2- , -C(CF ₃ ) ₂ -, -SO ₂ -, -CO- or -N(Q)-. Here, Q represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Examples of the monovalent hydrocarbon group having 1 to 12 carbon atoms include the groups described above for R ⁹ .
One example is where 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 positions of V ¹ and V ² to each ring and the bonding positions of V ² and V ³ to each ring are independent of each other, preferably at the meta position or para position with respect to each ring, and more preferably at the meta position or para position with respect to each ring. is in para position.

Among the groups represented by formulas (10) to (18), formulas (13), (14), formula (15), Groups represented by formula (16) and formula (17) are preferred, and groups represented by formula (14), formula (15) and formula (16) are more preferred. In addition, from the viewpoint of easily increasing the surface hardness and flexibility of the film obtained from the varnish of the present invention, V ¹ , V ² and V ³ are preferably a single bond, -O- or -S-, or more independently of each other. Preferably it is a single bond.

［式（４）中、Ｒ^１０～Ｒ^１７は、互いに独立に、水素原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基または炭素数６～１２のアリール基を表し、Ｒ^１０～Ｒ^１７に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、＊は結合手を表す］
で表される構成単位である。式（１）および式（２）中の複数のＸの少なくとも一部が式（４）で表される基であると、ワニス中でのポリイミド系樹脂のゲル化を抑制しやすいと共に、ワニスから得られるフィルムの表面硬度および透明性を高めやすい。 In a preferred embodiment of the present invention, at least some of the plurality of Xs in formula (1) and formula (2) are represented by formula (4):

[In formula (4), R ¹⁰ to R ¹⁷ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms, The hydrogen atoms contained in R ¹⁰ to R ¹⁷ may be substituted with halogen atoms independently of each other, and * represents a bond]
It is a constituent unit expressed as . When at least some of the plurality of Xs in formula (1) and formula (2) are groups represented by formula (4), gelation of the polyimide resin in the varnish can be easily suppressed, and It is easy to increase the surface hardness and transparency of the resulting film.

In formula (4), R ¹⁰ , R ¹¹ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ , R ¹⁶ and R ¹⁷ each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or a carbon number 1 ~6 alkoxy group or an aryl group having 6 to 12 carbon atoms. Examples of the alkyl group having 1 to 6 carbon atoms, the alkoxy group having 1 to 6 carbon atoms, or the aryl group having 6 to 12 carbon atoms include the alkyl group having 1 to 6 carbon atoms and the alkoxy group having 1 to 6 carbon atoms in formula (3). The groups or aryl groups having 6 to 12 carbon atoms include those exemplified. R ¹⁰ to R ¹⁷ independently of each other preferably represent a hydrogen atom or an alkyl group having 1 to ⁶ carbon atoms, more preferably a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; The hydrogen atoms contained in R ¹⁷ may be independently substituted with halogen atoms. Examples of the halogen atom include a fluorine atom and a chlorine atom. R ¹⁰ to R ¹⁷ are more preferably hydrogen atoms or methyl groups, independently of each other, from the viewpoint of easily suppressing gelation of the polyimide resin in the varnish, and improving the surface hardness, transparency, and bending resistance of the film. , represents a fluoro group, a chloro group, or a trifluoromethyl group, and even more preferably R ¹⁰ , R ¹² , R ¹³ , R ¹⁴ , R ¹⁵ and R ¹⁶ are hydrogen atoms, and R ¹¹ and R ¹⁷ are hydrogen atoms and methyl groups. , represents a fluoro group, a chloro group or a trifluoromethyl group, particularly preferably R ¹¹ and R ¹⁷ represent a methyl group or a trifluoromethyl group.

で表される構成単位であり、すなわち、式（１）および式（２）で表される複数の構成単位中の複数のＸの少なくとも一部は、式（４’）で表される構成単位である。この場合、フッ素元素を含有する骨格によりポリイミド系樹脂の溶媒への溶解性を高めやすく、ワニス中でのポリイミド系樹脂のゲル化を抑制しやすい。また、ワニスの粘度を低減しやすく、フィルムの加工性を向上しやすい。また、フッ素元素を含有する骨格により、ワニスから得られるフィルムの光学特性を向上しやすい。 In a preferred embodiment of the present invention, the structural unit represented by formula (4) is represented by formula (4'):

In other words, at least some of the plurality of X in the plurality of structural units represented by formula (1) and formula (2) are the structural units represented by formula (4') It is. In this case, the solubility of the polyimide resin in the solvent can be easily increased by the skeleton containing the fluorine element, and gelation of the polyimide resin in the varnish can be easily suppressed. In addition, it is easy to reduce the viscosity of the varnish and improve the processability of the film. Furthermore, the skeleton containing the fluorine element tends to improve the optical properties of the film obtained from the varnish.

In a preferred embodiment of the present invention, preferably 30 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more of X in the polyimide resin is represented by formula (4), especially formula (4). '). When X within the above range in the polyimide resin is represented by formula (4), especially formula (4'), the solubility of the polyimide resin in a solvent can be easily improved due to the skeleton containing the fluorine element. Moreover, it is easy to reduce the viscosity of the varnish, and it is easy to improve the processability of the film obtained from the varnish. Furthermore, the optical properties of the film obtained from the varnish are likely to be improved due to the skeleton containing elemental fluorine. Preferably, 100 mol% or less of X in the polyimide resin is represented by formula (4), particularly formula (4'). X in the polyamideimide resin may be represented by formula (4), particularly formula (4'). The proportion of the structural unit represented by formula (4) of X in the resin can be measured using, for example, ¹ H-NMR, or can be calculated from the charging ratio of raw materials.

The polyimide resin can include a structural unit represented by formula (30) and/or a structural unit represented by formula (31), and the structural unit represented by formula (1) and formula (2) In addition, it may contain a structural unit represented by formula (30) and/or a structural unit represented by formula (31).

In formula (30), Y ¹ is independently a tetravalent organic group, preferably an organic group in which the hydrogen atom in the organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group. It is the basis. As Y ¹ , formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28), and A group represented by formula (29), a group in which the hydrogen atom in the groups represented by formula (20) to formula (29) is substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group, Also, a tetravalent chain hydrocarbon group having 6 or less carbon atoms is exemplified. In one embodiment of the present invention, the polyimide resin may contain one type of Y ¹ or multiple types of Y ¹ , that is, a plurality of Y ¹ contained in the polyimide resin. may be the same or different.

In formula (31), Y ² is a trivalent organic group, preferably 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. As ^Y2 , the above formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28 ) and a group in which one of the bonding hands of the group represented by formula (29) is replaced with a hydrogen atom, and a trivalent chain hydrocarbon group having 6 or less carbon atoms are exemplified. In one embodiment of the present invention, the polyimide resin may contain one type of Y ² or multiple types of Y ² , that is, a plurality of Y ² contained in the polyimide resin. may be the same or different.

In formula (30) and formula (31), X ¹ and X ² are each independently a divalent organic group, preferably a hydrocarbon group in which the hydrogen atom in the organic group is a hydrocarbon group or a fluorine-substituted hydrocarbon group. is an organic group that may be substituted with As X ¹ and X ² , the above formula (10), formula (11), formula (12), formula (13), formula (14), formula (15), formula (16), formula (17) and A group represented by formula (18); a group in which the hydrogen atom in the groups represented by formulas (10) to (18) is substituted with a methyl group, fluoro group, chloro group or trifluoromethyl group; and A chain hydrocarbon group having 6 or less carbon atoms is exemplified.

In one embodiment of the present invention, the polyimide resin includes a structural unit represented by formula (1) and/or formula (2), and optionally a structure represented by formula (30) and/or formula (31). Consists of units. In addition, from the viewpoint of suppressing gelation of varnish, reducing the yellowness of the film obtained from the varnish, and improving optical properties, surface hardness, and bending resistance, in the above polyimide resin, formulas expressed by formula (1) and formula (2) are used. The structural units represented by formula (1), formula (2), and optionally formula (30) and formula (31) are preferably 80 mol% or more, more preferably 90 mol% or more. It is mol% or more, more preferably 95 mol% or more. In addition, in the polyimide resin, the structural units represented by formula (1) and formula (2) are represented by formula (1) and formula (2), and in some cases, formula (30) and/or formula (31). Based on all constituent units used, it is usually less than 100%. Note that the above ratio can be measured using, for example, ¹ H-NMR, or can also be calculated from the charging ratio of raw materials. From the same viewpoint, when the polyimide resin is a polyimide resin, the structural unit represented by formula (1) is preferably 80 mol% or more, more preferably 90 mol%, based on all the structural units contained in the polyimide resin. % or more, more preferably 95 mol% or more. Further, when the polyimide resin is a polyamide-imide resin, the structural units represented by formulas (1) and (2) are preferably 80 mol% or more, more preferably 80 mol% or more, based on the total structural units contained in the polyimide resin. is 90 mol% or more, more preferably 95 mol% or more.

In the polyamide-imide resin, the content of the structural unit represented by formula (2) is preferably 0.1 mol or more, more preferably 0.5 mol or more, per 1 mol of the structural unit represented by formula (1). mol or more, more preferably 1.0 mol or more, even more preferably 1.5 mol or more, preferably 6.0 mol or less, more preferably 5.0 mol or less, even more preferably 4.5 mol or less. be. When the content of the structural unit represented by formula (2) is at least the above lower limit, it is easy to increase the surface hardness of the film obtained from the varnish. In addition, when the content of the structural unit represented by formula (2) is below the above upper limit, thickening due to hydrogen bonding between amide bonds in formula (2) can be easily suppressed, and gelation of the varnish can be prevented. It is easy to process and improve the processability of the film.

In a preferred embodiment of the present invention, the polyimide resin may contain a halogen atom such as a fluorine atom, which can be introduced, for example, by the above-mentioned fluorine-containing substituent. When the polyimide resin contains fluorine atoms, it is easy to improve the elastic modulus of the film containing the polyimide resin and reduce the YI value. When the elastic modulus of the film is high, it is easy to suppress the occurrence of scratches, wrinkles, etc. in the film when the film is used, for example, in a flexible display device. Moreover, when the YI value of the film is low, it becomes easier to improve the transparency and visibility of the film. The halogen atom is preferably a fluorine atom. Preferred fluorine-containing substituents for containing fluorine atoms in the polyimide resin include, for example, a fluoro group and a trifluoromethyl group.

The content of halogen atoms, preferably the content of fluorine atoms, in the polyimide resin is preferably 1 to 40% by mass, more preferably 5 to 40% by mass, even more preferably 5 to 40% by mass, based on the mass of the polyimide resin. It is 30% by mass. When the content of halogen atoms is at least the above lower limit, the elastic modulus of the film containing the polyimide resin is further improved, the water absorption rate is lowered, the YI value is further reduced, and the transparency and visibility are further improved. Cheap. When the content of halogen atoms is below the above upper limit, the resin can be easily synthesized.

The imidization rate of the polyimide resin is preferably 90% or more, more preferably 93% or more, and still more preferably 96% or more. From the viewpoint of easily improving the dent resistance of the film containing the polyimide resin and also easily improving the optical properties, it is preferable that the imidization rate is equal to or higher than the above lower limit. Further, the upper limit of the imidization rate is 100% or less. The imidization rate indicates the ratio of the molar amount of imide bonds in the polyimide resin to twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin. In addition, when the polyimide resin contains a tricarboxylic acid compound, the value is twice the molar amount of the structural unit derived from the tetracarboxylic acid compound in the polyimide resin, and the molar amount of the structural unit derived from the tricarboxylic acid compound. It shows the ratio of the molar amount of imide bonds in the polyimide resin and polyamide-imide resin to the total of Further, the imidization rate can be determined by an IR method, an NMR method, or the like. For example, in the NMR method, it can be measured by the method described in Examples.

A commercially available polyimide resin may be used. Commercially available polyimide resins include, for example, Neoprim (registered trademark) manufactured by Mitsubishi Gas Chemical Co., Ltd. and KPI-MX300F manufactured by Kawamura Sangyo Co., Ltd.

The polyimide resin contained in the varnish of the present invention is preferably a transparent polyimide resin. When a polyimide resin is a transparent polyimide resin, for example, when a film with a thickness of 50 mm is produced using a polyimide resin contained in a varnish, the total light transmittance of the film is 85% or more, preferably It represents 87% or more, more preferably 89% or more, even more preferably 90% or more. Further, even when the transmittance of the polyimide resin varnish at 405 nm is within the range described below, it can be said that the polyimide resin contained in the varnish is a transparent polyimide resin.

In one embodiment of the present invention, the content of the polyimide resin contained in the varnish of the present invention is preferably 10 parts by mass or more, more preferably 30 parts by mass or more, based on 100 parts by mass of solid content of the varnish. More preferably, it is 50 parts by mass or more, preferably 99.5 parts by mass or less, and more preferably 95 parts by mass or less. When the content of the polyimide resin is within the above range, gelation of the varnish can be easily prevented, the dent resistance of the film obtained from the varnish can be easily improved, and the optical properties and elastic modulus can be easily improved.

In a preferred embodiment of the present invention, the varnish of the present invention has a transmittance of 405 nm at an optical path length of 10 mm, preferably 10% or more, more preferably 20% or more, still more preferably 30% or more, and even more preferably 40% or more. % or more. The transmittance of the varnish can be measured using an ultraviolet-visible near-infrared spectrophotometer using the varnish as a measurement sample. As the measurement conditions, for example, the conditions described in Examples may be used.

［式（３”）中、Ｒ^１～Ｒ^８は、互いに独立に、水素原子、炭素数１～６のアルキル基、炭素数１～６のアルコキシ基、または炭素数６～１２のアリール基を表し、Ｒ^１～Ｒ^８に含まれる水素原子は、互いに独立に、ハロゲン原子で置換されていてもよく、
Ａは、単結合、－Ｏ－、－ＣＨ_２－、－ＣＨ_２－ＣＨ_２－、－ＣＨ（ＣＨ_３）－、－Ｃ（ＣＨ_３）_２－、－Ｃ（ＣＦ_３）_２－、－ＳＯ_２－、－Ｓ－、－ＣＯ－または－Ｎ（Ｒ^９）－を表し、
Ｒ^９は水素原子、ハロゲン原子で置換されていてもよい炭素数１～１２の１価の炭化水素基を表し、
ｍは０～４の整数であり、
Ｒ^３１およびＲ^３２は、互いに独立に、ヒドロキシル基、メトキシ基、エトキシ基、ｎ－プロポキシ基、イソプロポキシ基、ｎ－ブトキシ基、ｓｅｃ－ブトキシ基、ｔｅｒｔ－ブトキシ基または塩素原子を表す。］ <Production method of polyimide resin>
Polyimide resins can be produced, for example, using tetracarboxylic acid compounds and diamine compounds as main raw materials, and polyamide-imide resins can be produced, for example, using tetracarboxylic acid compounds, dicarboxylic acid compounds, and diamine compounds as main raw materials. Here, it is preferable that the dicarboxylic acid compound contains at least a compound represented by formula (3'').

[In formula (3''), R ¹ to R ⁸ independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, an alkoxy group having 1 to 6 carbon atoms, or an aryl group having 6 to 12 carbon atoms. and the hydrogen atoms contained in R ¹ to R ⁸ may be independently substituted with a halogen atom,
A is a single bond, -O-, -CH ₂ -, -CH ₂ -CH ₂ -, -CH(CH ₃ )-, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, - represents SO ₂ -, -S-, -CO- or -N(R ⁹ )-,
R ⁹ represents a monovalent hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a hydrogen atom or a halogen atom,
m is an integer from 0 to 4,
R ³¹ and R ³² independently represent a hydroxyl group, a methoxy group, an ethoxy group, an n-propoxy group, an isopropoxy group, an n-butoxy group, a sec-butoxy group, a tert-butoxy group, or a chlorine atom. ]

Note that when using a dicarboxylic acid compound in the production of a polyimide resin, it is desirable to sufficiently purify the polyimide resin so that unreacted dicarboxylic acid compounds are not included in the polyimide resin. By using a polyimide resin with high purity, it becomes easy to adjust the content of dicarboxylic acid in a varnish containing the polyimide resin to 10 ppm or less.

In a preferred embodiment of the present invention, the dicarboxylic acid compound is a compound represented by the formula (3'') where m is 0. The dicarboxylic acid compound is a compound represented by the formula (3'') where m is 0. In addition to the compound represented by the formula (3''), in which A is an oxygen atom, a compound represented by the formula (3'') may be used. In another preferred embodiment, the dicarboxylic acid compound is a compound represented by R ³¹ and R This is a compound represented by formula (3'') in which ³² is a chlorine atom. Further, a diisocyanate compound may be used instead of a diamine compound.

Diamine compounds used in the production of resins include, for example, aliphatic diamines, aromatic diamines, and mixtures thereof. In addition, in this embodiment, "aromatic diamine" represents a diamine in which an amino group is directly bonded to an aromatic ring, and may include an aliphatic group or other substituent as part of its structure. This 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 preferred. Moreover, "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may include an aromatic ring or other substituents as part of its structure.

Examples of aliphatic diamines include acyclic aliphatic diamines such as hexamethylene diamine, 1,3-bis(aminomethyl)cyclohexane, 1,4-bis(aminomethyl)cyclohexane, norbornanediamine, and 4,4' - Cycloaliphatic diamines such as diaminodicyclohexylmethane and the like. 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, 2,6-diaminonaphthalene, etc. Aromatic diamine having one aromatic ring, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylpropane, 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether, 4,4'-diaminodiphenylsulfone, 3,4'-diaminodiphenylsulfone, 3,3'-diaminodiphenylsulfone, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(4 -aminophenoxy)benzene, bis[4-(4-aminophenoxy)phenyl]sulfone, bis[4-(3-aminophenoxy)phenyl]sulfone, 2,2-bis[4-(4-aminophenoxy)phenyl] Propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2'-dimethylbenzidine, 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (with TFMB) ), 4,4'-bis(4-aminophenoxy)biphenyl, 9,9-bis(4-aminophenyl)fluorene, 9,9-bis(4-amino-3-methylphenyl)fluorene , 9,9-bis(4-amino-3-chlorophenyl)fluorene, and 9,9-bis(4-amino-3-fluorophenyl)fluorene, which have two or more aromatic rings. These can be used alone or in combination of two or more.

Aromatic diamines are 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)-4,4'-diaminodiphenyl (TFMB), 4,4'-bis(4-aminophenoxy)biphenyl, more preferably 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl Propane, 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(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB), 4,4'- It is bis(4-aminophenoxy)biphenyl. These can be used alone or in combination of two or more.

Among the above diamine compounds, one or more selected from the group consisting of aromatic diamines having a biphenyl structure are used from the viewpoint of high surface hardness, high transparency, high flexibility, high bending resistance, and low coloring property of the film. It is preferable. One species 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 the above, and even more preferable to use 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB).

Examples of the tetracarboxylic acid compounds used in the production of the resin include aromatic tetracarboxylic acid compounds such as aromatic tetracarboxylic dianhydride; and aliphatic tetracarboxylic acid compounds such as aliphatic tetracarboxylic dianhydride. It will be done. Tetracarboxylic acid compounds may be used alone or in combination of two or more. The tetracarboxylic acid compound may be a dianhydride or a tetracarboxylic acid compound analog such as an acid chloride compound.

Specific examples of aromatic tetracarboxylic dianhydrides include non-fused polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and fused polycyclic aromatic tetracarboxylic dianhydrides. Examples include carboxylic dianhydrides. Examples of the non-fused polycyclic aromatic tetracarboxylic dianhydride include 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 2,2 ',3,3'-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, 2,2-bis(2,3-dicarboxylic dianhydride) carboxyphenyl)propane dianhydride, 2,2-bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (described as 6FDA) ), 1,2-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3, 4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3 -dicarboxyphenyl)methane dianhydride, 4,4'-(p-phenylenedioxy)diphthalic dianhydride, and 4,4'-(m-phenylenedioxy)diphthalic dianhydride. Furthermore, examples of the monocyclic aromatic tetracarboxylic dianhydride include 1,2,4,5-benzenetetracarboxylic dianhydride, and fused polycyclic aromatic tetracarboxylic dianhydride. Examples include 2,3,6,7-naphthalenetetracarboxylic dianhydride.

Among these, 4,4'-oxydiphthalic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, and 2,2',3,3'-benzophenonetetracarboxylic dianhydride are preferable. Anhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,2',3,3'-biphenyltetracarboxylic dianhydride, 3,3',4,4'-diphenyl Sulfone tetracarboxylic dianhydride, 2,2-bis(3,4-dicarboxyphenyl)propane dianhydride, 2,2-bis(2,3-dicarboxyphenyl)propane dianhydride, 2,2- Bis(3,4-dicarboxyphenoxyphenyl)propane dianhydride, 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride (6FDA), 1,2-bis(2,3-dicarboxyphenyl) Ethane dianhydride, 1,1-bis(2,3-dicarboxyphenyl)ethane dianhydride, 1,2-bis(3,4-dicarboxyphenyl)ethane dianhydride, 1,1-bis(3 ,4-dicarboxyphenyl)ethane dianhydride, bis(3,4-dicarboxyphenyl)methane dianhydride, bis(2,3-dicarboxyphenyl)methane dianhydride, 4,4'-(p- Examples include 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 dianhydride. These can be used alone or in combination of two or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic or acyclic aliphatic tetracarboxylic dianhydride. Cycloaliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples include 1,2,4,5-cyclohexanetetracarboxylic dianhydride. dianhydride, cycloalkane tetracarboxylic dianhydride such as 1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentane tetracarboxylic dianhydride, bicyclo[2.2 .2] Oct-7-ene-2,3,5,6-tetracarboxylic dianhydride, dicyclohexyl-3,3',4,4'-tetracarboxylic dianhydride and positional isomers thereof. It will be done. These can be used alone or in combination of two or more. Specific examples of the acyclic aliphatic tetracarboxylic dianhydride include 1,2,3,4-butanetetracarboxylic dianhydride and 1,2,3,4-pentanetetracarboxylic dianhydride. These can be used alone or in combination of two or more. Furthermore, a combination of a cycloaliphatic tetracarboxylic dianhydride and an acyclic aliphatic tetracarboxylic dianhydride may be used.

Among the above tetracarboxylic dianhydrides, 4,4'-oxydiphthalic dianhydride, 3,3 ',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, including 3,3',4,4'-biphenyltetracarboxylic dianhydride and 4,4'-(hexafluoroisopropylidene)diphthalic dianhydride, and mixtures thereof. A mixture of these is more preferred, and 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) is even more preferred.

Examples of dicarboxylic acid compounds used in the production of the resin include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, etc., and two or more types may be used in combination. Specific examples include terephthalic acid; 2,5-bis(trifluoromethyl)terephthalic acid; isophthalic acid; 2,5-dimethylterephthalic acid; 2,5-dimethoxyterephthalic acid; naphthalene dicarboxylic acid; 4,4'-biphenyl Dicarboxylic acid; 3,3'-biphenyldicarboxylic acid; 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarboxylic acid; dicarboxylic acid compounds of chain hydrocarbons having 8 or less carbon atoms and two Compounds in which benzoic acid is linked with a single bond, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or phenylene group, and their acid chloride compounds are mentioned. It will be done. Among these dicarboxylic acid compounds, 4,4'-oxybisbenzoic acid, terephthalic acid, isophthalic acid, 2-methoxyterephthalic acid chloride, 2, 5-dimethylterephthalic acid, 2,5-dimethoxyterephthalic acid, 2,5-bis(trifluoromethyl)terephthalic acid, 2,2'-bis(trifluoromethyl)-4,4'-biphenyldicarboxylic acid and their Acid chlorides are preferred, such as 2-methoxyterephthalic acid chloride (hereinafter sometimes referred to as OMTPC), 4,4'-oxybis(benzoyl chloride) OBBC), 2,5-dimethylterephthalic acid chloride , 2,5-dimethoxyterephthalic acid chloride, 2,5-bis(trifluoromethyl)terephthalic acid chloride, terephthalic acid dichloride (hereinafter sometimes referred to as TPC), isophthalic acid dichloride (hereinafter referred to as IPC) Among them, OBBC, TPC, IPC, 2-methoxyterephthalic acid chloride, 2,5-dimethylterephthalic acid chloride, and 2,5-dimethoxyterephthalic acid chloride are more preferable.

The above polyimide resin may be one obtained by further reacting tetracarboxylic acid and tricarboxylic acid, as well as anhydrides and derivatives thereof, in addition to the above tetracarboxylic acid compound, as long as various physical properties of the film are not impaired. good.

Examples of the tetracarboxylic acid include water adducts of anhydrides of the above-mentioned tetracarboxylic acid compounds.

Examples of the tricarboxylic acid compound include aromatic tricarboxylic acids, aliphatic tricarboxylic acids, and their analogous acid chloride compounds, acid anhydrides, etc., and two or more types may be used in combination. Specific examples include 1,2,4-benzenetricarboxylic acid anhydride; 1,3,5-benzenetricarboxylic acid chloride compound; 2,3,6-naphthalenetricarboxylic acid-2,3-anhydride; A compound in which an acid anhydride and benzoic acid are connected by a single bond, -O-, -CH ₂ -, -C(CH ₃ ) ₂ -, -C(CF ₃ ) ₂ -, -SO ₂ - or phenylene group can be mentioned.

In the production of the resin, the amount of the diamine compound, tetracarboxylic acid compound and/or dicarboxylic acid compound to be used can be appropriately selected depending on the ratio of each constituent unit of the desired polyimide resin.

In the production of resin, the reaction temperature of the diamine compound, tetracarboxylic acid compound and dicarboxylic acid compound is not particularly limited, but is, for example, 5 to 350°C, preferably 20 to 200°C, more preferably 25 to 100°C. The reaction time is also not particularly limited, and 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. In a preferred embodiment, the reaction is carried out with stirring under normal pressure and/or an inert gas atmosphere. Further, the reaction is preferably carried out in a solvent inert to the reaction. The solvent is not particularly limited as long as it does not affect the reaction, but examples include water, methanol, ethanol, ethylene glycol, isopropyl alcohol, propylene glycol, ethylene glycol methyl ether, ethylene glycol butyl ether, 1-methoxy-2-propanol, Alcohol solvents such as 2-butoxyethanol and propylene glycol monomethyl ether; esters such as ethyl acetate, butyl acetate, ethylene glycol methyl ether acetate, γ-butyrolactone [GBL], γ-valerolactone, propylene glycol methyl ether acetate, and ethyl lactate. Ketone solvents such as acetone, methyl ethyl ketone, cyclopentanone, cyclohexanone, 2-heptanone, methyl isobutyl ketone; Aliphatic hydrocarbon solvents such as pentane, hexane, heptane; Alicyclic hydrocarbon solvents such as ethylcyclohexane; Aromatic hydrocarbon solvents such as toluene and xylene; Nitrile solvents such as acetonitrile; Ether solvents such as tetrahydrofuran and dimethoxyethane; Chlorine-containing solvents such as chloroform and chlorobenzene; N,N-dimethylacetamide [DMAc], N,N - Amide solvents such as dimethylformamide [DMF]; sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane; carbonate solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide solvents can be preferably used from the viewpoint of solubility.

In the imidization step in the production of polyimide resin, imidization can be carried out in the presence of an imidization catalyst. Examples of imidization catalysts include aliphatic amines such as tripropylamine, dibutylpropylamine, and ethyldibutylamine; N-ethylpiperidine, N-propylpiperidine, N-butylpyrrolidine, N-butylpiperidine, and N-propylhexahydr 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] Alicyclic amines (polycyclic) such as nonane; and pyridine, 2-methylpyridine (2-picoline), 3-methylpyridine (3-picoline), 4-methylpyridine (4-picoline), 2- Ethylpyridine, 3-ethylpyridine, 4-ethylpyridine, 2,4-dimethylpyridine, 2,4,6-trimethylpyridine, 3,4-cyclopentenopyridine, 5,6,7,8-tetrahydroisoquinoline, and Examples include aromatic amines such as isoquinoline. Further, from the viewpoint of easily promoting the imidization reaction, it is preferable to use an acid anhydride together with the imidization catalyst. Examples of acid anhydrides include commonly used acid anhydrides used in imidization reactions. Specific examples thereof include aliphatic acid anhydrides such as acetic anhydride, propionic anhydride, and butyric anhydride, and aromatic acid anhydrides such as phthalic acid. Examples include acid anhydrides.

The polyimide resin may be isolated (separated and purified) by conventional methods such as filtration, concentration, extraction, crystallization, recrystallization, column chromatography, or a combination of these. In a preferred embodiment, a large amount of alcohol such as methanol is added to a reaction solution containing a transparent imide resin to precipitate the resin, which can be isolated by concentration, filtration, drying, etc.

<Solvent>
The varnish of the invention also contains a solvent. The solvent is not particularly limited as long as it can dissolve the polyimide resin; for example, amide solvents such as N,N-dimethylacetamide (DMAc) and N,N-dimethylformamide (DMF); γ-butyrolactone (GBL) , lactone-based solvents such as γ-valerolactone; sulfur-containing solvents such as dimethylsulfone, dimethylsulfoxide, and sulfolane; carbonate-based solvents such as ethylene carbonate and propylene carbonate; and combinations thereof. Among these, amide solvents or lactone solvents are preferred. These solvents can be used alone or in combination. Further, the varnish may contain water, an alcohol solvent, a ketone solvent, an acyclic ester solvent, an ether solvent, and the like. The concentration of the solvent based on the total amount of varnish is preferably 75 to 99% by weight, more preferably 80 to 95% by weight, even more preferably 85 to 95% by weight. The solid content concentration of the varnish is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, and still more preferably 5 to 15% by weight.

<Other ingredients>
(filler)
The varnish of the present invention may contain at least one filler in addition to the polyimide resin and the solvent. Examples of the filler include organic particles and inorganic particles, preferably inorganic particles. Inorganic particles include metal oxide particles such as silica, zirconia, alumina, titania, zinc oxide, germanium oxide, indium oxide, tin oxide, indium tin oxide (sometimes written as ITO), antimony oxide, and cerium oxide. , metal fluoride particles such as magnesium fluoride and sodium fluoride, and among these, silica particles, zirconia particles, and alumina particles are preferred, and silica particles are more preferred. These fillers can be used alone or in combination of two or more.

The average primary particle diameter of the filler, preferably silica particles, is usually 1 nm or more, preferably 5 nm or more, more preferably 10 nm or more, even more preferably 15 nm or more, particularly preferably 20 nm or more, and preferably 100 nm or less, more preferably It is 90 nm or less, more preferably 80 nm or less, even more preferably 70 nm or less, especially preferably 60 nm or less, especially more preferably 50 nm or less, even more preferably 40 nm or less. When the average primary particle diameter of the filler, preferably silica particles, is within the above range, aggregation of the filler, preferably silica particles, is suppressed and the optical properties of the resulting optical laminate are likely to be improved. The average primary particle diameter of the filler can be measured by the BET method. Note that the average primary particle diameter may be measured by image analysis using a transmission electron microscope or a scanning electron microscope.

When the varnish of the present invention contains a filler, preferably silica particles, the content of the filler, preferably silica particles, is usually 0.1% by mass or more, preferably 1% by mass, based on the total solid content of the varnish. The content is more preferably 5% by mass or more, still more preferably 10% by mass or more, even more preferably 20% by mass or more, particularly preferably 30% by mass or more, and preferably 60% by mass or less. When the content of the filler is at least the above lower limit, the elastic modulus of the resulting film is likely to be improved. Moreover, when the filler content is below the above upper limit, the storage stability of the varnish is improved, and the optical properties of the resulting film are likely to be improved.

(Ultraviolet absorber)
The varnish of the present invention may contain one or more types of ultraviolet absorbers. The ultraviolet absorber can be appropriately selected from those commonly used as ultraviolet absorbers in the field of resin materials. The ultraviolet absorber may include a compound that absorbs light with 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 varnish of the present invention contains an ultraviolet absorber, deterioration of the polyimide resin in a film produced from the varnish is suppressed, so that the visibility of the film can be improved.
In addition, in this specification, a "system compound" refers to the derivative of the compound to which the said "system compound" is attached. For example, a "benzophenone compound" refers to a compound having benzophenone as a parent skeleton and a substituent bonded to benzophenone.

When the varnish of the present invention contains an ultraviolet absorber, the content of the ultraviolet absorber is preferably 1% by mass or more, more preferably 2% by mass or more, still more preferably 3% by mass, based on the solid content of the varnish. or more, preferably 10% by mass or less, more preferably 8% by mass or less, still more preferably 6% by mass or less. The preferred content varies depending on the UV absorber used, but if the content of the UV absorber is adjusted so that the light transmittance at 400 nm is about 20 to 60%, the light resistance of the film will be increased and the transparency will be improved. You can get high quality film.

(Other additives)
The varnish of the present invention may further contain additives other than fillers and ultraviolet absorbers. Examples of other additives include antioxidants, mold release agents, stabilizers, bluing agents, flame retardants, pH adjusters, silica dispersants, lubricants, thickeners, silane coupling agents, and leveling agents. can be mentioned. When containing other additives, the content thereof is preferably 0.001 to 20 parts by mass, more preferably 0.01 to 15 parts by mass, and even more preferably 0. .1 to 10 parts by weight.

<Method for producing varnish of the present invention>
The varnish of the present invention is not particularly limited, but can be prepared by dissolving a polyimide resin in a solvent, adding additives such as the filler and ultraviolet absorber as necessary, and stirring and mixing.
In addition, when using silica particles as a filler, a silica sol dispersion containing silica particles may be substituted with a solvent in which the resin can be dissolved, for example, the above-mentioned solvent, and a silica sol may be added to the resin.
The solid content concentration of the varnish is preferably 1 to 25% by weight, more preferably 5 to 20% by weight, and even more preferably 5 to 15% by weight.

<Film>
Films, preferably optical films, can be produced using the varnish of the invention. The present invention also provides an optical film formed from the varnish of the present invention, particularly an optical film obtained by casting the varnish of the present invention. The varnish of the present invention is suitable as a varnish for producing optical films.

The thickness of the optical film obtained from the varnish of the present invention is adjusted appropriately depending on the application, but is usually 10 to 1,000 μm, preferably 15 to 500 μm, more preferably 20 to 400 μm, and still more preferably 25 to 300 μm. It is. In the present invention, the thickness can be measured using a contact-type digimatic indicator.

The total light transmittance Tt of the optical film obtained from the varnish of the present invention is preferably 70% or more, more preferably 80% or more, still more preferably 85% or more, even more preferably 89% or more, particularly preferably 90%. That's all. If the total light transmittance Tt of the optical film is at least the above lower limit, sufficient visibility can be easily ensured when the optical film is incorporated into an image display device. Note that the upper limit of the total light transmittance Tt of the optical film is usually 100% or less. The haze of the optical film is preferably 3.0% or less, more preferably 2.0% or less, even more preferably 1.0% or less, even more preferably 0.8% or less, particularly preferably 0.5% or less. , particularly preferably 0.3% or less. When the haze of the optical film is below the above upper limit, sufficient visibility can be easily ensured when the optical film is incorporated into a flexible electronic device such as an image display device. Note that the lower limit of the haze is not particularly limited, and may be 0% or more. Note that the total light transmittance and haze can be measured using a haze computer in accordance with JIS K 7105:1981.

The YI value of the optical film obtained from the varnish of the present invention is preferably 8 or less, more preferably 5 or less, still more preferably 3 or less, and even more preferably 2.8 or less. When the YI value of the optical film is less than or equal to the above upper limit, the optical film has good transparency, and can contribute to high visibility when used, for example, as a front plate of an image display device. Further, the YI value is usually -5 or more, preferably -2 or more. The YI value is determined by measuring the transmittance of light in the range of 300 to 800 nm using an ultraviolet-visible near-infrared spectrophotometer to determine tristimulus values (X, Y, Z), and calculating YI = 100 x (1.2769X- It can be calculated based on the formula: 1.0592Z)/Y. For example, it may be measured by the method described in Examples. The optical film obtained from the varnish of the present invention preferably has a YI value within the above range even after 24 hours of UV irradiation, for example, after 24 hours of irradiation with 313 nm UV light at 40 W.

Generally, optical films may be exposed to ultraviolet light for a long period of time when used in image display devices. In the film of the present invention, even in such a case, the YI value does not increase significantly, so there is little change in color and the visibility is high. The film of the present invention preferably has a small ΔYI determined by the following procedure. For example, the ΔYI is preferably 1.50 or less, more preferably 1.2 or less, and even more preferably 1.1 or less.
ΔYI=(YIa-YIb)
(In the formula, YIa represents the YI value before ultraviolet irradiation described below, YIb is UV-B (wavelength 313 nm), ultraviolet rays with an output of 40 W, and the distance between the sample and the light source is set to 5 cm. (Represents the YI value of the film after 24 hours of ultraviolet irradiation.)

<Method for manufacturing the film of the present invention>
The method for producing the film of the present invention is not particularly limited, but examples include the following production method:
A manufacturing method comprising at least (a) a coating step of applying the varnish of the present invention to a substrate to form a coating film, and (b) a film forming step of drying the coating film to form the film of the present invention. It's good.

In the coating step (a), a varnish is coated on the substrate to form a coating film using a known coating method. Known coating methods include, for example, wire bar coating, reverse coating, roll coating such as gravure coating, die coating, comma coating, lip coating, spin coating, screen coating, fountain coating, and dipping. method, spray method, drool molding method, etc.

Examples of the base material include SUS plate if it is metal-based, PET film, PEN film, polyamide resin film, other polyimide resin films, other polyamide-imide resin films, cycloolefin polymer film, etc. if it is resin-based. Examples include acrylic film and glass. Among them, glass, PET film, SUS plate, etc. are preferable from the viewpoint of excellent smoothness and heat resistance, and from the viewpoint of adhesion with the film of the present invention and cost, and from the viewpoint of easy production of a film with excellent dent resistance. Glass and PET films are more preferred.

In the film forming step (b), the film of the present invention can be manufactured by drying the coating film. The coating film is dried at a temperature of 250°C or less, preferably 50 to 250°C, from the viewpoint of easily lowering the YI value and from the viewpoint of easily suppressing the deterioration of the properties of the base material layer, preferably the bending resistance. It is preferable to do so. If necessary, the coating film may be dried in an inert atmosphere or under reduced pressure conditions. Note that the resulting coating film contains components other than the solvent contained in the varnish, so the content of each component contained in the coating layer is determined by the solid content concentration of each component contained in the varnish. equal to the content based on Further, a small amount of the solvent may remain in the coating layer. The amount of solvent contained in the coating layer is preferably 1.5% or less, more preferably 1.2% or less, even more preferably 1.1% or less, and even more preferably It is 1.0% or less. The lower limit of the amount of solvent is preferably 0% or more, more preferably 0.02% or more, even more preferably 0.1% or more, and even more preferably 0.3% or more.

The step of drying the coating film in the film forming step may be carried out by performing preliminary drying and then main drying. From the viewpoint of maintaining the quality of the film surface, the pre-drying temperature is preferably 50°C or higher, more preferably 80°C or higher, even more preferably 100°C or higher, and preferably 200°C or lower, more preferably 150°C or lower. . The pre-drying time may be appropriately selected depending on the type of solvent contained in the varnish, the pre-drying temperature, etc., and is preferably 5 to 150 minutes, more preferably 10 to 120 minutes, and even more preferably 20 to 60 minutes. . Pre-drying may be carried out under an inert atmosphere or under reduced pressure conditions, if necessary.

The main drying temperature is preferably 150°C or higher, more preferably 180°C or higher, and still more preferably 200°C or higher, from the viewpoint of removing the solvent in the coating film and improving the adhesion between the coating film and the base material layer. , from the viewpoint of easily lowering the YI value and from the viewpoint of easily maintaining the characteristics of the base material layer, preferably 250°C or less, more preferably 240°C or less, still more preferably 230°C or less, and even more preferably 220°C. It is as follows. The main drying temperature is higher than the preliminary drying temperature, preferably 30°C or more higher than the preliminary drying temperature, more preferably 40°C or more higher, still more preferably 50°C or higher. The main drying time may be appropriately selected depending on the solid content concentration of the resin coating film after pre-drying, and is preferably 1 to 120 minutes, more preferably 5 to 80 minutes, and still more preferably 10 to 40 minutes. . The main drying may be performed under an inert atmosphere or under reduced pressure conditions, if necessary.

[Film with functional layer]
The use of the film of the present invention is not particularly limited, and it may be used for various purposes. Further, the film of the present invention may be used as a laminated film in which at least one functional layer is laminated on one or both sides.

The film of the invention may have at least one functional layer on at least one side. Examples of the functional layer include a hard coat layer, a primer layer, a gas barrier layer, an ultraviolet absorption layer, an adhesive layer, a hue adjustment layer, and a refractive index adjustment layer. The functional layers can be used alone or in combination.

The thickness of the hard coat layer is not particularly limited, and may be, for example, 2 to 100 μm. When the thickness of the hard coat layer is within the above range, impact resistance can be improved, flexibility resistance is less likely to decrease, and the problem of curling due to curing shrinkage tends to be less likely to occur. The hard coat layer can be formed by curing a hard coat composition containing a reactive material capable of forming a crosslinked structure by irradiation with active energy rays or application of thermal energy, preferably by irradiation with active energy rays. Active energy rays are defined as energy rays that can generate active species by decomposing compounds that generate active species, and include visible light, ultraviolet rays, infrared rays, X-rays, α-rays, β-rays, γ-rays, and electron beams. Preferably, ultraviolet light is used. The hard coat composition contains at least one polymer of a radically polymerizable compound and a cationically polymerizable compound.

The radically polymerizable compound is a compound having a radically polymerizable group. The radically polymerizable group possessed by the radically polymerizable compound may be any functional group that can cause a radical polymerization reaction, such as a group containing a carbon-carbon unsaturated double bond, and specifically, a vinyl group, etc. , (meth)acryloyl group, etc. Note that when the radically polymerizable compound has two or more radically polymerizable groups, these radically polymerizable groups may be the same or different. The number of radically polymerizable groups that the radically polymerizable compound has in one molecule is preferably 2 or more in order to improve the hardness of the hard coat layer. From the viewpoint of high reactivity, the radically polymerizable compound is preferably a compound having a (meth)acryloyl group, specifically a compound having 2 to 6 (meth)acryloyl groups in one molecule. Compounds called polyfunctional acrylate monomers, epoxy (meth)acrylates, urethane (meth)acrylates, and polyester (meth)acrylates have several (meth)acryloyl groups in the molecule and have a molecular weight of several hundred to Thousands of oligomers may be mentioned, preferably one or more selected from epoxy (meth)acrylates, urethane (meth)acrylates and polyester (meth)acrylates.

The cationic polymerizable compound is a compound having a cationic polymerizable group such as an epoxy group, an oxetanyl group, or a vinyl ether group. The number of cationically polymerizable groups that the cationically polymerizable compound has in one molecule is preferably 2 or more, more preferably 3 or more, from the viewpoint of improving the hardness of the hard coat layer.
Further, as the cationically polymerizable compound, a compound having at least one of an epoxy group and an oxetanyl group as a cationically polymerizable group is particularly preferable. Cyclic ether groups such as epoxy groups and oxetanyl groups are preferred from the viewpoint of low shrinkage due to polymerization reactions. In addition, among the cyclic ether groups, compounds having an epoxy group are easily available in a variety of structures, do not adversely affect the durability of the obtained hard coat layer, and are easy to control compatibility with radically polymerizable compounds. There is an advantage. In addition, among cyclic ether groups, oxetanyl groups tend to have a higher degree of polymerization than epoxy groups, accelerate the rate of network formation from cationically polymerizable compounds in the resulting hard coat layer, and are mixed with radically polymerizable compounds. Even in the region where monomers are used, there are advantages such as forming an independent network without leaving unreacted monomers in the film.
Examples of the cationically polymerizable compound having an epoxy group include polyglycidyl ether of a polyhydric alcohol having an alicyclic ring, or a compound containing a cyclohexene ring or a cyclopentene ring, using an appropriate oxidizing agent such as hydrogen peroxide or peracid. Alicyclic epoxy resin obtained by epoxidation; polyglycidyl ether of aliphatic polyhydric alcohol or its alkylene oxide adduct, polyglycidyl ester of aliphatic long-chain polybasic acid, homopolymer of glycidyl (meth)acrylate, Aliphatic epoxy resins such as copolymers; glycidyl ethers produced by reacting bisphenols such as bisphenol A, bisphenol F and hydrogenated bisphenol A, or derivatives thereof such as alkylene oxide adducts and caprolactone adducts with epichlorohydrin; and glycidyl ether type epoxy resins derived from bisphenols, such as novolak epoxy resins.

The hard coat composition may further include a polymerization initiator. Examples of the polymerization initiator include radical polymerization initiators, cationic polymerization initiators, and radical and cationic polymerization initiators, which are appropriately selected and used. These polymerization initiators are decomposed by at least one of active energy ray irradiation and heating to generate radicals or cations to advance radical polymerization and cationic polymerization.
Any radical polymerization initiator may be used as long as it is capable of releasing a substance that initiates radical polymerization by at least one of active energy ray irradiation and heating. For example, examples of the thermal radical polymerization initiator include hydrogen peroxide, organic peroxides such as perbenzoic acid, and azo compounds such as azoisobisbutyronitrile.
Active energy ray radical polymerization initiators include Type 1 radical polymerization initiators that generate radicals by decomposition of molecules, and Type 2 radical polymerization initiators that coexist with tertiary amines and generate radicals through hydrogen abstraction type reactions. and they may be used alone or in combination.
Any cationic polymerization initiator may be used as long as it is capable of releasing a substance that initiates cationic polymerization by at least one of active energy ray irradiation and heating. As the cationic polymerization initiator, aromatic iodonium salts, aromatic sulfonium salts, cyclopentadienyl iron (II) complexes, etc. can be used. Depending on their structure, cationic polymerization can be initiated by irradiation with active energy rays and/or heating.

The polymerization initiator may preferably be contained in an amount of 0.1 to 10% by weight based on 100% by weight of the entire hard coat composition. When the content of the polymerization initiator is within the above range, curing can proceed sufficiently, and the mechanical properties and adhesion of the final coating film can be in a good range, and Poor adhesion, cracking, and curling due to curing shrinkage tend to occur less easily.

The hard coat composition may further include one or more selected from the group consisting of a solvent and an additive.
The solvent can dissolve or disperse the polymerizable compound and the polymerization initiator, and does not inhibit the effects of the present invention, as long as it is a solvent known as a solvent for hard coat compositions in the technical field. Can be used within a range.
The additives may further include inorganic particles, leveling agents, stabilizers, surfactants, antistatic agents, lubricants, antifouling agents, and the like.

The ultraviolet absorbing layer is a layer that has the function of absorbing ultraviolet rays, and includes, for example, a main material selected from ultraviolet curable transparent resin, electron beam curable transparent resin, and thermosetting transparent resin, and this main material. It consists of a dispersed ultraviolet absorber.

The adhesive layer is a layer having an adhesive function, and has the function of adhering the film to other members. As the material for forming the adhesive layer, commonly known materials can be used. For example, a thermosetting resin composition or a photocurable resin composition can be used. In this case, the thermosetting resin composition or photocurable resin composition can be polymerized and cured by supplying energy afterwards.

The adhesive layer may be a layer called pressure sensitive adhesive (PSA) that is attached to the object by pressure. Pressure-sensitive adhesives may be adhesives that are "substances that are sticky at room temperature and adhere to adherends with light pressure" (JIS K 6800), or "substances that contain specific components in a protective coating (microcapsules)" (JIS K 6800). ) and can maintain stability until the film is destroyed by appropriate means (pressure, heat, etc.) (JIS K 6800).

The hue adjustment layer is a layer that has a function of hue adjustment, and is a layer that can adjust the hue of the film to a desired hue. The hue adjustment layer is, for example, a layer containing a resin and a colorant. Examples of the coloring agent include inorganic pigments such as titanium oxide, zinc oxide, Bengara, titanium oxide fired pigments, ultramarine, cobalt aluminate, and carbon black; azo compounds, quinacridone compounds, anthraquinone compounds, Organic pigments such as perylene compounds, isoindolinone compounds, phthalocyanine compounds, quinophthalone compounds, threne compounds, and diketopyrrolopyrrole compounds; extender pigments such as barium sulfate and calcium carbonate; and basic dyes, Dyes such as acid dyes and mordant dyes can be mentioned.

The refractive index adjusting layer is a layer having a refractive index adjusting function, and has a refractive index different from that of the single-layer film of the present invention, for example, and can impart a predetermined refractive index to a laminate containing the film. This is the layer where you can do it. The refractive index adjusting layer may be, for example, a resin layer containing an appropriately selected resin and optionally a pigment, or may be a thin metal film. Examples of pigments that adjust the refractive index include silicon oxide, aluminum oxide, antimony oxide, tin oxide, titanium oxide, zirconium oxide, and tantalum oxide. The average primary particle size 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, it is possible to prevent diffuse reflection of light passing through the refractive index adjusting layer and prevent a decrease in transparency. Examples of metals used in 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. Mention may be made of oxides or metal nitrides.

In one embodiment of the present invention, the film of the present invention and/or the laminate containing the film may have a protective film on at least one surface (one or both surfaces). For example, when the film of the present invention has a functional layer on one side, the protective film may be laminated on the surface of the film of the present invention or the surface of the functional layer, or the protective film may be laminated on both the film of the present invention and the functional layer. may be stacked on top of each other. When the film of the present invention has functional layers on both sides, the protective film may be laminated on the surface of one of the functional layers, or may be laminated on the surfaces of both functional layers. The protective film is a film for temporarily protecting the surface of the film or functional layer of the present invention, and is not particularly limited as long as it is a peelable film that can protect the surface of the film or functional layer. Examples of the protective film include polyester resin films such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; polyolefin resin films such as polyethylene and polypropylene films; acrylic resin films; Preferably, the film is selected from the group consisting of terephthalate resin films and acrylic resin films. When the film and/or laminate of the present invention has two protective films, each protective film may be the same or different.

The thickness of the protective film is not particularly limited, but is usually 10 to 120 μm, preferably 15 to 110 μm, and more preferably 20 to 100 μm. When the film of the present invention and/or the laminate of the present invention has two protective films, the thickness of each protective film may be the same or different.

In one embodiment of the invention, the film of the invention and/or the laminate containing the film may have a thin glass layer on at least one surface. With such a configuration, impact resistance and shatter prevention functions can be imparted to the thin glass.
Both sides of the thin glass may have layers formed from the film of the present invention. The upper limit of the film thickness of the thin glass is preferably 200 μm or less, more preferably 150 μm or less, and even more preferably 100 μm or less. The lower limit of the film thickness of the thin glass is preferably 5 μm or more, more preferably 10 μm or more. The thin glass may be chemically strengthened. A laminate containing the film of the present invention and thin glass may be produced by coating a thin glass with the varnish of the present invention, or may be produced by laminating the film of the present invention. A primer layer may be provided between the polyimide layer and the thin glass layer to improve adhesion to the thin glass.

The film of the present invention can be suitably used as a front plate (sometimes referred to as a window film) of a display device, especially a flexible display device, particularly a front plate of a rollable display or a foldable display. That is, the film of the present invention is preferably an optical film, more preferably a film for the front panel of a display device, and even more preferably a film for the front panel of a flexible display device. The front plate has a function of protecting the display element of the flexible display device. Note that the flexible display device is a display device that is used with operations such as repeatedly bending or repeatedly winding the image display device. The front plate of a flexible display device used with such repeated bending operations is required to have high bending resistance, especially high folding resistance. The front panel also requires high visibility. Compared to the film for the substrate of the image display device used inside the image display device, the front panel of the image display device, especially the film or laminate for the front panel of the flexible display device, requires high visibility. At the same time, high bending resistance is required. For example, the film of the present invention preferably has the total light transmittance, haze, and/or YI value as described above, from the viewpoint of easily improving visibility when used for a front panel of a flexible display device. Further, from the viewpoint of easily improving bending resistance, especially bending resistance when used as a front plate of a flexible display device, it is preferable that the bending resistance satisfies the number of bending resistances described above. Examples of display devices include televisions, smartphones, mobile phones, car navigation systems, tablet PCs, portable game consoles, electronic paper, indicators, bulletin boards, watches, and wearable devices such as smart watches. Examples of flexible displays include display devices having flexible characteristics, such as televisions, smartphones, mobile phones, and smart watches. Examples of flexible display devices include all image display devices having flexible characteristics, such as rollable displays and foldable displays as described above. A rollable display is an image display device in which the image display part including the front plate is wound up into a roll, and the image display part is pulled out and used in a flat or curved state. This is an image display device that requires operations such as picking it up each time it is used. Furthermore, a foldable display is an image display device in which the image display part including the front panel is folded and is used with the image display part opened to make a flat or curved surface. This is an image display device that is used every time. An image display device in which such operations such as winding and folding are repeatedly performed is called a flexible image display device.

[Flexible display device]
The film of the present invention is preferably used as a front plate in a flexible display device, and the front plate is sometimes referred to as a window film. The flexible display device is composed of a flexible display device laminate and an organic EL display panel, and the flexible display device laminate is arranged on the viewing side with respect to the organic EL display panel, and is configured to be foldable. The laminate for a flexible display device may further contain a polarizing plate and a touch sensor, and the order in which they are stacked is arbitrary. , a polarizing plate are preferably laminated in this order. It is preferable that the polarizing plate is present on the viewing side of the touch sensor because the pattern of the touch sensor becomes less visible and the visibility of the displayed image improves. Each member can be laminated using an adhesive, a pressure-sensitive adhesive, or the like. Further, a light shielding pattern may be provided on at least one surface of any one of the window film, polarizing plate, and touch sensor layer.
The polarizing plate, the touch sensor, and the light shielding pattern are not particularly limited, and known ones can be used.

EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples. Note that "%" and "parts" in Examples and Comparative Examples are "% by mass" and "parts by mass", respectively, unless otherwise specified.

The weight average molecular weights of the polyimide resins used in Examples and Comparative Examples were measured using the following procedure.
<Weight average molecular weight (Mw)>
Gel permeation chromatography (GPC) measurement/pretreatment method DMF eluent (10mM lithium bromide solution) was added to the polyamide-imide resin at a concentration of 2mg/mL, heated at 80°C for 30 minutes with stirring, and cooled. Thereafter, the solution was filtered through a 0.45 μm membrane filter and used as a measurement solution.
・Measurement conditions Column: TSKgel SuperAWM-H x 2 + SuperAW2500 x 1 (6.0mm I.D. x 150mm x 3)
Eluent: DMF (containing 10mM lithium bromide)
Flow rate: 1.0mL/min.
Detector: RI detector Column temperature: 40°C
Injection volume: 100μL
Molecular weight standard: standard polystyrene

<Production Example 1: Synthesis of polyamideimide resin (1)>
<Synthesis of polyamide-imide resin (1)>
Under a nitrogen gas atmosphere, 45 g (140.52 mmol) of 2,2'-bis(trifluoromethyl)-4,4'-diaminodiphenyl (TFMB) and N,N-dimethyl were placed in a 1 L separable flask equipped with a stirring blade. 770.40 g of acetamide (DMAc) was added, and TFMB was dissolved in DMAc with stirring at room temperature. Next, 19.01 g (42.80 mmol) of 4,4'-(hexafluoroisopropylidene) diphthalic dianhydride (6FDA) was added to the flask, and the mixture was stirred at room temperature for 3 hours. Then, 4.21 g (14.27 mmol) of 4,4'-oxybis(benzoyl chloride) (OBBC) and then 17.38 g (85.60 mmol) of terephthaloyl chloride (TPC) were added to the flask and stirred at room temperature for 1 hour. did. Next, 4.65 g (49.93 mmol) of 4-methylpyridine and 13.11 g (128.39 mmol) of acetic anhydride were added to the flask, and after stirring at room temperature for 30 minutes, the temperature was raised to 70 ° C. using an oil bath. After stirring for an additional 3 hours, the reaction solution was cooled to room temperature. Next, methanol was added to the reaction solution while stirring, and the deposited precipitate was taken out. The precipitate was immersed in methanol for 8 hours, washed with methanol, and then dried under reduced pressure at 100° C. to obtain a polyamide-imide resin. The weight average molecular weight Mw of the polyamide-imide resin (1) was 210,000.

<Example 1: Preparation of varnish (1)>
Gamma-butyrolactone solution (0.01% by mass) of 822.05 g of gamma-butyrolactone, 4.60 g of ultraviolet absorber [Sumisorb 340 (manufactured by Sumika Chemtex)], and bluing agent [Sumiplast Violet B (manufactured by Sumika Chemtex)] 15 .0g, 9.78g of gamma-butyrolactone solution (1.0% by mass) of fluorosurfactant [FC4430 (manufactured by 3M)], 26.19g of tetramethylurea, and 100.00g of polyamideimide resin (1) were dissolved. A polyamide-imide varnish was produced.
The resulting polyamide-imide varnish was filled into a container with a ratio of container inner diameter/liquid level height of 0.7 and sealed. After standing still for 7 days, the polyamide-imide varnish was put into a pressure-resistant container equipped with a disc filter (LPD-03-PB (manufactured by Loki Techno, filtration accuracy 3 μm)), filtered under pressure of 0.3 MPa, and the filtrate The weight was measured every 5 minutes, and the filtration rate and rate of change A of the filtration rate were determined by the following method.

<Change rate A of filtration rate>
The filtrate weight at each time measured under the above conditions was converted into filtration weight per unit time to calculate the filtration rate. Furthermore, log ₁₀ (filtration rate (g/hour)) was calculated and plotted against the filtrate weight (g), and a value corresponding to the following formula A was calculated as the slope. Since the filtration rate tended to fluctuate immediately after the start of filtration, the value after the filtration rate stabilized was used as the evaluation value.
Note that the smaller the value of the rate of change A, the more stable the filtration rate is with respect to the filtration weight. If gel is present in the varnish, the gel will accumulate on the filter during filtration and the filtration rate will decrease.The fact that the rate of change A is small is due to the gelation of the polyimide resin in the varnish and the gelation during filtration. This means that the formation of gel is suppressed.
A = Δlog ₁₀ (filtration rate (g/hour)) x 1000/Δfiltrate weight (g)

<Varnish transmittance>
Regarding the polyamide-imide varnish before the filtration test, the transmittance at 405 nm was measured using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO Corporation. The measurement was performed by performing background measurement in a state in which pure water was placed in a quartz cell with an optical path length of 10 mm, and then by filling the quartz cell with an optical path length of 10 mm with varnish.

<Example 2: Preparation of varnish (2)>
A polyamide-imide varnish was produced in the same manner as in Example 1 except that the amount of gamma-butyrolactone was 804.59 g and the amount of tetramethylurea was 43.65 g, and the polyamide-imide varnish was evaluated.

<Example 3: Preparation of varnish (3)>
A polyamide-imide varnish was prepared in the same manner as in Example 1 except that the amount of gamma-butyrolactone was 787.14 g and the amount of tetramethylurea was 61.10 g, and the polyamide-imide varnish was evaluated.

<Example 4: Preparation of varnish (4)>
A polyamide-imide varnish was prepared in the same manner as in Example 1 except that the amount of gamma-butyrolactone was 760.95 g and the amount of tetramethylurea was 87.29 g, and the polyamide-imide varnish was evaluated.

<Comparative Example 1: Preparation of varnish (5)>
A polyamide-imide varnish was prepared in the same manner as in Example 1 except that the amount of gamma-butyrolactone was 848.24 g and tetramethylurea was not added, and the polyamide-imide varnish was evaluated.

<Production of film>
The varnish after the filtration rate test was applied onto glass using an applicator so that the average thickness of the free-standing film was 52 μm, and dried at 50°C for 30 minutes and then at 140°C for 15 minutes to obtain a free-standing film. Ta. The self-supporting film was fixed to an A4 size metal frame, heated to 200° C. over 40 minutes, and dried by maintaining the temperature at 200° C. for 20 minutes to obtain a polyimide resin film with a thickness of 50 μm.

The following measurements and evaluations were performed on the films obtained in each Example and Comparative Example.
<Measurement of film thickness>
The thickness of the film was measured using an ABS digimatic indicator (manufactured by Mitutoyo Co., Ltd., "ID-C112BS").

<Evaluation of optical properties of film>
(1) Total light transmittance The polyimide resin film obtained in the example was cut into a size of 30 mm x 30 mm, and the The total light transmittance (%) of the film was measured.

(2) Yellowness (YI value)
The yellow index (YI value) of each of the polyimide resin films obtained in the examples was measured using an ultraviolet-visible near-infrared spectrophotometer V-670 manufactured by JASCO Corporation. After background measurement was performed without a sample, the polyimide resin film was set on a sample holder, transmittance measurement was performed for light in the range of 300 to 800 nm, and tristimulus values (X, Y, Z) were determined. . The YI value was calculated based on the following formula.
YI=100×(1.2769X-1.0592Z)/Y

(3) ΔYI value light irradiation test A polyimide resin film was subjected to a light irradiation test using UVCON manufactured by Atlas. The light source was UV-B 313 nm, the output was 40 W, and the distance between the sample and the light source was set to 5 cm. The polyimide resin film was irradiated with ultraviolet rays for 24 hours.
The yellowness (YI value) of the film before and after UV irradiation was measured as described above, and the difference was calculated.

(4) Haze
The polyimide resin film obtained in the example was cut into a size of 30 mm x 30 mm, and the haze (%) was measured using a haze computer (manufactured by Suga Test Instruments Co., Ltd., "HGM-2DP").

The results of each evaluation are shown in the table below.

In the polyimide resin varnishes of Examples 1 to 4, which contain a polyimide resin, at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, and a solvent, the rate of change A in filtration rate is It was confirmed that gelation of the polyimide resin in the varnish and/or gel formation during filtration was suppressed. On the other hand, in the case of the varnish of Comparative Example 1 which does not contain at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, the rate of change A in the filtration rate is large, which is due to the polyimide in the varnish. This is thought to be due to gelation of the system resin and/or gel formation during filtration. When manufacturing a film industrially using a varnish like Comparative Example 1, the filter needs to be replaced more frequently, and the rate of change A in the filtration rate is large, making the amount of varnish discharged unstable. There is a possibility that the quality of manufactured films may vary.

Claims (11)

A polyimide resin varnish comprising a polyimide resin, at least one compound selected from the group consisting of urea compounds and cyclic amide compounds, and a solvent. The urea compound has formula (a1) or formula (a2):

[In formula (a1) and formula (a2), R ^a1 to R ^a6 each independently represent a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, and m represents an integer of 1 to 4. ]
The polyimide resin varnish according to claim 1, which is a compound represented by: The cyclic amide compound has the formula (b):

[In formula (b), R ^b1 represents a divalent hydrocarbon group having 1 to 6 carbon atoms, and R ^b2 represents a hydrogen atom or a monovalent hydrocarbon group having 1 to 6 carbon atoms]
The polyimide resin varnish according to claim 1, which is a compound represented by: The polyimide resin varnish according to claim 2, wherein the urea compound is a compound represented by formula (a1). The polyimide resin varnish according to claim 1, wherein the amount of at least one compound selected from the group consisting of urea compounds and cyclic amide compounds is 15% by mass or less based on the total amount of the polyimide resin varnish. . The polyimide resin varnish according to claim 1, wherein the polyimide resin is a polyamideimide resin having a fluorine atom. The polyimide resin has the formula (1):

[In formula (1), Y represents a tetravalent organic group, X represents a divalent organic group, and * represents a bond]
Formula (26) includes a structural unit represented by, and as Y in formula (1):

[In formula (26), W ¹ is 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-, -Ar-SO ₂ -Ar- or -CO-O-Ar-O-CO-, where Ar is a hydrogen atom substituted with an alkyl group having 1 to 3 carbon atoms or a fluorine atom represents an arylene group having 6 to 20 carbon atoms, and * represents a bond]
and at least one group selected from the group consisting of a group represented by formula (26) in which a hydrogen atom is substituted with a methyl group, a fluoro group, a chloro group, or a trifluoromethyl group. The polyimide resin varnish according to claim 1, comprising a group. The polyimide resin varnish according to claim 1, which is a varnish for producing an optical film. The polyimide resin varnish according to claim 1, having a transmittance of 10% or more at 405 nm at an optical path length of 10 mm. The polyimide resin varnish according to claim 1, wherein the polyimide resin is a transparent polyimide resin. An optical film formed from the polyimide resin varnish according to any one of claims 1 to 10.