CN118251446A

CN118251446A - Polyimide resin, varnish and polyimide film

Info

Publication number: CN118251446A
Application number: CN202280074156.7A
Authority: CN
Inventors: 安孙子洋平; 石井健太郎; 村谷孝博
Original assignee: Mitsubishi Gas Chemical Co Inc
Current assignee: Mitsubishi Gas Chemical Co Inc
Priority date: 2021-11-11
Filing date: 2022-10-21
Publication date: 2024-06-25
Also published as: TW202328293A; KR20240095412A; WO2023085041A1; JPWO2023085041A1

Abstract

A polyimide resin having a structural unit a derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, the structural unit a comprising: a structural unit (A1) selected from at least 1 of the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11) and a structural unit (a 12) derived from a compound represented by the following formula (a 12); and a structural unit (A2) derived from a compound represented by the following general formula (A2), the structural unit B comprising a structural unit (B1) derived from a compound represented by the following general formula (B1).

Description

Polyimide resin, varnish and polyimide film

Technical Field

The present invention relates to a polyimide resin, a varnish and a polyimide film.

Background

Polyimide resins have excellent mechanical properties, and therefore various uses thereof in the fields of electric and electronic components and the like have been studied. For example, for the purpose of weight reduction and flexibility of a device, it is desired to replace a glass substrate used in an image display device such as a liquid crystal display and an OLED display with a plastic substrate, and research on polyimide resins suitable as the plastic material is also being conducted. For polyimide resins for such applications, transparency is also required, and further, high heat resistance is also required so that it can cope with high temperature processes in the manufacturing process of image display devices.

In recent years, in the field of microelectronics, a laser lift-off process called laser lift-off (LLO) has been attracting attention as a method for separating a resin film from a support among supports on which the resin film is laminated. In order to make the polyimide film compatible with laser lift-off processing, development of a polyimide film excellent in laser lift-off property is also underway.

For example, patent document 1 discloses a polyimide resin containing a structural unit derived from norbornane-2-spiro- α -cyclopentanone- α '-spiro-2 "-norbornane-5, 5",6 "-tetracarboxylic dianhydride, a structural unit derived from 2,2' -bis (trifluoromethyl) benzidine, and the like for the purpose of improving mechanical properties, heat resistance, transparency, dimensional stability, and laser peelability.

Prior art literature

Patent literature

Patent document 1: international publication No. 2019/065523

Disclosure of Invention

Problems to be solved by the invention

Polyimide films used in image display devices are required to have good optical properties such as colorless transparency, and as described above, are also required to have high heat resistance so as to be compatible with high-temperature processes in the manufacturing process of the image display devices. In particular, when the TFT is of the LTPS (low temperature polysilicon TFT) type, the polyimide which is a substrate is required to have heat resistance which can withstand a treatment at a high temperature of 400 ℃ or more several times at a process temperature exceeding 400 ℃.

Although the polyimide film has excellent heat resistance in a short period of time, when it is subjected to a high temperature treatment for a long period of time, it is required to have a low weight loss during the high temperature treatment in order to withstand the high temperature treatment several times as described above.

Further, in order to cope with the laser lift-off processing, laser lift-off property is also required. In particular, in order to cope with peeling processing by XeCl excimer laser light having a wavelength of 308nm, polyimide films are required to have excellent characteristics of absorbing light having a wavelength of 308nm (i.e., to have a small transmittance at a wavelength of 308 nm).

Accordingly, an object of the present invention is to provide a polyimide resin and a polyimide varnish which can form a film excellent in heat resistance, particularly, a film having a small weight loss at the time of high temperature treatment and further excellent in laser peelability, and a polyimide film having an excellent heat resistance, particularly, a small weight loss at the time of high temperature treatment and further excellent in laser peelability.

Solution for solving the problem

The present inventors have found that a polyimide resin comprising a combination of structural units derived from a specific 2 kinds of tetracarboxylic dianhydrides and structural units derived from a specific diamine can solve the above-mentioned problems, and have completed the present invention.

That is, the present invention relates to the following < 1> < 18 >.

<1> A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine,

The structural unit A comprises: a structural unit (A1) selected from at least 1 of the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11) and a structural unit (a 12) derived from a compound represented by the following formula (a 12); and a structural unit (A2) derived from a compound represented by the following general formula (A2),

The structural unit B includes a structural unit (B1) derived from a compound represented by the following general formula (B1).

(In the formula (b 1), R is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, a hydroxyl group.)

<2> The polyimide resin according to the above <1>, wherein the ratio of the structural unit (B1) in the structural unit B is 15 mol% or more.

<3> The polyimide resin according to the above <1> or <2>, wherein the structural unit B further comprises a structural unit (B2) derived from a compound represented by the following formula (B2).

<4> The polyimide resin according to the above <3>, wherein the molar ratio [ (B1)/(B2) ] of the structural unit (B1) to the structural unit (B2) in the structural unit B is 15/85 to 70/30.

<5> The polyimide resin according to any one of the above <1> to <4>, wherein the structural unit (A11) comprises a structural unit (A111) derived from a compound represented by the following formula (a 111).

<6> The polyimide resin according to any one of the above <1> to <5>, wherein the structural unit (A2) comprises a structural unit (A2 s) derived from a compound represented by the following formula (A2 s).

<7> The polyimide resin according to any one of the above <1> to <6>, wherein the structural unit (B1) comprises a structural unit (B11) derived from a compound represented by the following formula (B11).

<8> The polyimide resin according to any one of the above <1> to <7>, wherein the molar ratio [ (A1)/(A2) ] of the structural unit (A1) to the structural unit (A2) in the structural unit A is 30/70 to 85/15.

<9> A varnish prepared by dissolving the polyimide resin according to any one of the above <1> to <8> in an organic solvent.

<10> An imide-amic acid copolymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).

(Wherein A ¹ is at least 1 selected from the group consisting of a group represented by the following formula (3) and a group represented by the following formula (4), and A ² is a group represented by the following formula (5).

B ¹ and B ² are 2-valent groups, and any of B ¹ and B ² contains a group represented by the following formula (6).

X ¹ and X ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms. )

<11> A varnish comprising the imide-amic acid copolymer of <10> above dissolved in an organic solvent.

<12> The varnish according to <11> above, further comprising an imidazole compound represented by the following general formula (7).

(In the formula (7), L ¹ and L ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, a hydroxyl group, and n is an integer of 1 to 4.)

<13> A polyimide resin obtained by imidizing the amic acid moiety in the copolymer of <10 >.

<14> A polyimide film comprising the polyimide resin according to any one of the above <1> to <8> and <13 >.

<15> The polyimide film according to the above <14>, which has a weight loss ratio of less than 1.0% when kept at 430 ℃ for 1 hour, and a glass transition temperature of 410 ℃ or more.

<16> The polyimide film according to the above <14> or <15>, which is used as a transparent substrate constituting a display device.

<17> A method for producing a polyimide film, wherein the varnish of <9>, <11> or <12> is applied to a support and heated.

<18> An image display device comprising the polyimide film according to any one of <14> to <16> as a transparent substrate.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, there can be provided: polyimide resins capable of forming films having excellent heat resistance, particularly, having little weight loss during high-temperature treatment and excellent laser peelability; polyimide varnish; and a polyimide film which is excellent in heat resistance, particularly, has little weight loss during high-temperature treatment, and is excellent in laser peelability.

Detailed Description

[ Polyimide resin ]

The polyimide resin of the present invention has a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine, the structural unit A comprising: a structural unit (A1) selected from at least 1 of the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11) and a structural unit (a 12) derived from a compound represented by the following formula (a 12); and a structural unit (A2) derived from a compound represented by the following general formula (A2), the structural unit B comprising a structural unit (B1) derived from a compound represented by the following general formula (B1).

The reason why the polyimide resin of the present invention is excellent in heat resistance, particularly the reason why the weight loss at the time of high temperature treatment is small, is not yet determined, but is considered as follows.

It is believed that even if some part of the carbon-carbon bonds in the multi-alicyclic structure of the polyimide resin of the present invention are homolytic by heat (homolytic cleavage), the generated radicals are fixed in the matrix through a plurality of carbon atoms. Therefore, it is considered that the rebuckling occurs, and as a result, the decomposition becomes less likely to occur. By such a mechanism, it is considered that excellent heat resistance is exhibited.

The reason why the polyimide resin of the present invention can form a polyimide film excellent in laser peelability is not yet known, but is considered as follows.

It is considered that a resin having high absorption of the laser wavelength of irradiation, that is, low light transmittance can be obtained by containing not only the structural unit (A1) but also the structural unit (A2) derived from the compound represented by the formula (A2) as the structural unit derived from the tetracarboxylic dianhydride. Therefore, ablation is uniformly generated at the interface with the glass substrate, and laser peelability is considered to be excellent.

< Structural Unit A >

The structural unit a is a structural unit derived from tetracarboxylic dianhydride, which is contained in the polyimide resin.

The structural unit A comprises: a structural unit (A1) selected from at least 1 of the group consisting of a structural unit (a 11) derived from a compound represented by the following formula (a 11) and a structural unit (a 12) derived from a compound represented by the following formula (a 12); and a structural unit (A2) derived from a compound represented by the following general formula (A2).

By including the structural unit (A1) and the structural unit (A2), the heat resistance of the film can be improved. Particularly, the weight loss during high temperature treatment can be suppressed, and the laser peelability of the film can be improved.

By including the structural unit (A1) in the structural unit a, heat resistance of the film can be improved. In particular, weight loss during high temperature treatment can be suppressed.

The compound represented by the formula (a 11) is decahydro-1, 4:5, 8-dimethylnaphthalene-2, 3,6, 7-tetracarboxylic dianhydride (DNDA).

By including the structural unit (a 11) in the structural unit a, transparency and heat resistance of the film can be improved. In particular, weight loss during high temperature treatment can be suppressed.

The compound shown in the formula (a 12) is bicyclooctane-2, 3,5, 6-tetracarboxylic anhydride (BODA).

By including the structural unit (a 12) in the structural unit a, transparency and heat resistance of the film can be improved. In particular, weight loss during high temperature treatment can be suppressed.

The structural unit (A1) preferably contains a structural unit (a 11), more preferably a structural unit (a 11).

The structural unit (a 11) preferably includes a structural unit (a 111) derived from a compound represented by the following formula (a 111), and more preferably a structural unit (a 111) derived from a compound represented by the following formula (a 111). By including the structural unit (a 111) in the structural unit (a 11), transparency and heat resistance of the film can be improved. In particular, weight loss during high temperature treatment can be suppressed. The compound represented by the formula (a 111) is 1 stereoisomer of the compound represented by the formula (a 11).

By including the structural unit (A2) in the structural unit a, laser peelability of the film can be improved.

The compound represented by the formula (a 2) is biphenyl tetracarboxylic dianhydride (BPDA). Specific examples thereof include 3,3',4' -biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a 2 s), 2, 3',4' -biphenyltetracarboxylic dianhydride (a-BPDA) represented by the following formula (a 2 a), and 2,2', 3' -biphenyltetracarboxylic dianhydride (i-BPDA) represented by the following formula (a 2 i). Among them, 3',4' -biphenyltetracarboxylic dianhydride (s-BPDA) represented by the following formula (a 2 s) is preferable.

That is, the structural unit (A2) preferably includes a structural unit (A2 s) derived from a compound represented by the following formula (A2 s), and more preferably a structural unit (A2 s) derived from a compound represented by the following formula (A2 s).

The molar ratio [ (A1)/(A2) ] of the structural unit (A1) to the structural unit (A2) in the structural unit A is preferably 30/70 to 85/15, more preferably 50/50 to 85/15, still more preferably 55/45 to 65/35. By setting the molar ratio, the transparency and heat resistance of the film can be improved. In particular, weight loss during high temperature treatment can be suppressed.

The ratio of the structural unit (A1) in the structural unit a is preferably 30 to 85 mol%, more preferably 50 to 85 mol%, still more preferably 55 to 85 mol%, and still more preferably 55 to 65 mol%.

The ratio of the structural unit (A2) in the structural unit a is preferably 15 to 70 mol%, more preferably 15 to 50 mol%, further preferably 15 to 45 mol%, and still more preferably 35 to 45 mol%.

The total ratio of the structural unit (A1) and the structural unit (A2) in the structural unit a is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 100 mol% or less. The structural unit a may be composed of only the structural unit (A1) and the structural unit (A2).

The structural unit a may include structural units other than the structural unit (A1) and the structural unit (A2). The tetracarboxylic dianhydride to which such a structural unit is added is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides excluding the compound represented by the formula (a 2), alicyclic tetracarboxylic dianhydrides excluding the compound represented by the formula (a 11) and excluding the compound represented by the formula (a 12), and aliphatic tetracarboxylic dianhydrides.

In the present specification, the aromatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride having 1 or more aromatic rings, the alicyclic tetracarboxylic dianhydride means a tetracarboxylic dianhydride having 1 or more alicyclic rings and containing no aromatic rings, and the aliphatic tetracarboxylic dianhydride means a tetracarboxylic dianhydride containing neither aromatic rings nor alicyclic rings.

The number of the structural units optionally contained in the structural unit A may be 1 or 2 or more.

< Structural Unit B >

The structural unit B is a structural unit derived from diamine and occupied in polyimide resin.

The structural unit B includes a structural unit (B1) derived from a compound represented by the following formula (B1).

By including the structural unit (B1) in the structural unit B, heat resistance of the film can be improved. In particular, the weight loss during high temperature treatment can be suppressed, and the laser peelability and optical isotropy of the film can be improved.

In the formula (b 1), R is at least 1 selected from the group consisting of a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group, and a hydroxyl group, and is preferably a hydrogen atom. Specific examples of the compound represented by the formula (b 1) include 9, 9-bis (4-aminophenyl) fluorene, 9-bis (3-fluoro-4-aminophenyl) fluorene, 9-bis (3-methyl-4-aminophenyl) fluorene, and the like, and 9, 9-bis (4-aminophenyl) fluorene (BAFL) represented by the following formula (b 11) is preferable. That is, the structural unit (B1) preferably includes a structural unit (B11) derived from a compound represented by the following formula (B11), and more preferably the structural unit (B1) is a structural unit (B11) derived from a compound represented by the following formula (B11).

The ratio of the structural unit (B1) in the structural unit B is preferably 15 mol% or more, more preferably 30 mol% or more, further preferably 50 mol% or more, further preferably 70 mol% or more, further preferably 80 mol% or more, further preferably 90 mol% or more, further preferably 95 mol% or more, and further preferably 100 mol% or less, from the viewpoints of laser peelability and heat resistance of the film. The structural unit B may be constituted only by the structural unit (B1).

The structural unit B may be constituted by only the structural unit (B1), or may include structural units other than the structural unit (B1), and preferably further includes, as structural units other than the structural unit (B1), a structural unit (B2) derived from a compound represented by the following formula (B2).

The compound represented by the formula (b 2) is 2,2' -bis (trifluoromethyl) benzidine (TFMB). By including the structural unit (B2) in the structural unit B, transparency can be improved while maintaining heat resistance.

When the structural unit B includes the structural unit (B2), the molar ratio [ (B1)/(B2) ] of the structural unit (B1) to the structural unit (B2) in the structural unit B is preferably 15/85 to 70/30, more preferably 15/85 to 50/50, still more preferably 30/70 to 45/55. By setting the molar ratio, the heat resistance and laser peelability of the film can be improved, and further, the transparency can be improved.

When the structural unit B includes the structural unit (B2), the ratio of the structural unit (B1) in the structural unit B is preferably 15 to 70 mol%, more preferably 15 to 50 mol%, still more preferably 30 to 50 mol%, and still more preferably 30 to 45 mol%.

The ratio of the structural unit (B2) in the structural unit B is preferably 30 to 85 mol%, more preferably 50 to 85 mol%, still more preferably 50 to 70 mol%, still more preferably 55 to 70 mol%.

The total ratio of the structural units (B1) and (B2) in the structural unit B is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 100 mol% or less. The structural unit B may be composed of only the structural unit (B1) and the structural unit (B2).

The structural unit B may include structural units other than the structural unit (B1) and the structural unit (B2). The diamine to which such a structural unit is added is not particularly limited, and examples thereof include aromatic diamines, alicyclic diamines, and aliphatic diamines excluding the compound represented by the formula (b 11) and excluding the compound represented by the formula (b 2).

In the present specification, an aromatic diamine means a diamine containing 1 or more aromatic rings, an alicyclic diamine means a diamine containing 1 or more alicyclic rings and containing no aromatic rings, and an aliphatic diamine means a diamine containing no aromatic rings and containing no alicyclic rings.

The structural units other than the structural unit (B1) and the structural unit (B2) optionally contained in the structural unit B may be 1 kind or 2 kinds or more.

< Property of polyimide resin >

The number average molecular weight of the polyimide resin is preferably 5,000 ～ 300,000 from the viewpoint of mechanical strength of the obtained polyimide film. The number average molecular weight of the polyimide resin can be obtained, for example, from a standard polymethyl methacrylate (PMMA) conversion value measured by gel permeation chromatography.

The polyimide resin may contain a structure other than a polyimide chain (a structure in which the structural unit a and the structural unit B are imide-bonded). Examples of the structure other than the polyimide chain that can be contained in the polyimide resin include a structure containing an amide bond.

The polyimide resin preferably contains a polyimide chain (a structure in which a structural unit a and a structural unit B are imide-bonded) as a main structure. Therefore, the ratio of the polyimide chain in the polyimide resin is preferably 50% by mass or more, more preferably 70% by mass or more, still more preferably 90% by mass or more, and still more preferably 99% by mass or more. Further, it is preferably 100 mass% or less. The polyimide resin may be composed of only polyimide chains.

[ Method for producing polyimide resin ]

The method for producing the polyimide resin of the present invention is not particularly limited, but any of the 2 methods described below is preferable.

The first production method of the present invention is a method of obtaining a polyimide resin by reacting the compound (tetracarboxylic acid component) imparting structural units a with the compound (diamine component) imparting structural units B. By this method, a polyimide resin can be directly obtained from the tetracarboxylic acid component and the diamine component.

The second production method of the present invention is a method for obtaining a polyimide resin by imidizing the amic acid site in an imide-amic acid copolymer having an imide repeating structural unit and an amic acid repeating structural unit.

The following describes each method.

< Method for producing first polyimide resin >

According to the present production method, a polyimide resin can be produced by reacting the tetracarboxylic acid component containing the structural unit (A1) -imparting compound and the structural unit (A2) -imparting compound with the diamine component containing the structural unit (B1) -imparting compound.

The compound to which the structural unit (A1) is added includes a compound represented by the formula (a 11) and a compound represented by the formula (a 12), but is not limited to these, and may be a derivative thereof within a range to which the same structural unit is added. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by the formula (a 11) and an alkyl ester of the tetracarboxylic acid. Among them, tetracarboxylic dianhydride represented by the formula (a 11) is preferable. Further, as the derivative, a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by the formula (a 12) and an alkyl ester of the tetracarboxylic acid are exemplified. Among them, tetracarboxylic dianhydride represented by the formula (a 12) is preferable.

Similarly, the compound to be added to the structural unit (A2) is a compound represented by the formula (A2), but the compound is not limited to these, and may be a derivative thereof within the range to be added to the same structural unit. Examples of the derivative include a tetracarboxylic acid corresponding to the tetracarboxylic dianhydride represented by the formula (a 2) and an alkyl ester of the tetracarboxylic acid. Among them, tetracarboxylic dianhydride represented by the formula (a 2) is preferable.

In the tetracarboxylic acid component, the molar ratio [ (A1)/(A2) ] of the compound imparting structural unit (A1) to the compound imparting structural unit (A2) is preferably 30/70 to 85/15, more preferably 50/50 to 85/15, still more preferably 55/45 to 65/35.

The ratio of the compound to be added to the structural unit (A1) in the tetracarboxylic acid component is preferably 30 to 85 mol%, more preferably 50 to 85 mol%, still more preferably 55 to 85 mol%, and still more preferably 55 to 65 mol%.

The ratio of the compound to be added to the structural unit (A2) in the tetracarboxylic acid component is preferably 15 to 70 mol%, more preferably 15 to 50 mol%, still more preferably 15 to 45 mol%, and still more preferably 35 to 45 mol%.

The total ratio of the compound imparting the structural unit (A1) and the compound imparting the structural unit (A2) in the tetracarboxylic acid component is preferably 50 mol% or more, more preferably 70 mol% or more, still more preferably 90 mol% or more, and further preferably 100 mol% or less. The tetracarboxylic acid component may be composed of only the compound imparting the structural unit (A1) and the compound imparting the structural unit (A2).

The tetracarboxylic acid component may contain a tetracarboxylic dianhydride other than the compound for imparting the structural unit (A1) and the compound for imparting the structural unit (A2). The tetracarboxylic dianhydride is not particularly limited, and examples thereof include aromatic tetracarboxylic dianhydrides excluding the compound represented by the formula (a 2), alicyclic tetracarboxylic dianhydrides excluding the compound represented by the formula (a 11) and excluding the compound represented by the formula (a 12), and aliphatic tetracarboxylic dianhydrides.

The number of tetracarboxylic dianhydrides optionally contained in the tetracarboxylic acid component may be 1 or 2 or more.

The compound to which the structural unit (B1) is added may be a compound represented by the formula (B1), but is not limited to these, and may be a derivative thereof within a range to which the same structural unit is added. The derivative may be a diisocyanate corresponding to the compound (diamine) represented by the formula (b 1). Among them, the compound represented by the formula (b 1) (i.e., diamine) is preferable.

The ratio of the compound to be added to the structural unit (B1) in the diamine component is preferably 15 mol% or more, more preferably 30 mol% or more, still more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 80 mol% or more, still more preferably 90 mol% or more, still more preferably 95 mol% or more, and still more preferably 100 mol% or less. The diamine component may be composed of only the compound imparting the structural unit (B1).

The diamine component may contain a structural unit other than the compound imparting the structural unit (B1), and preferably further contains a compound imparting the structural unit (B2) derived from the compound represented by the formula (B2).

When the diamine component contains a compound imparting a structural unit (B2), the molar ratio [ (B1)/(B2) ] of the compound imparting a structural unit (B1) to the compound imparting a structural unit (B2) in the diamine component is preferably 15/85 to 70/30, more preferably 15/85 to 50/50, still more preferably 30/70 to 45/55.

When the diamine component contains the compound imparting the structural unit (B2), the ratio of the compound imparting the structural unit (B1) in the diamine component is preferably 15 to 70 mol%, more preferably 15 to 50 mol%, still more preferably 30 to 45 mol%.

The ratio of the compound to be added to the structural unit (B2) in the diamine component is preferably 30 to 85 mol%, more preferably 50 to 85 mol%, still more preferably 50 to 70 mol%, and still more preferably 55 to 70 mol%.

The total ratio of the compound imparting structural unit (B1) and the compound imparting structural unit (B2) in the diamine component is preferably 50 mol% or more, more preferably 70 mol% or more, further preferably 90 mol% or more, and further preferably 100 mol% or less. The diamine component may be composed of only the compound imparting the structural unit (B1) and the compound imparting the structural unit (B2).

The diamine component may contain a diamine other than the compound for imparting the structural unit (B1) and the compound for imparting the structural unit (B2). The diamine to which such a structural unit is added is not particularly limited, and examples thereof include aromatic diamines, alicyclic diamines, and aliphatic diamines excluding the compound represented by the formula (b 11) and excluding the compound represented by the formula (b 2).

The diamine other than the structural unit (B1) and the structural unit (B2) optionally contained in the diamine component may be 1 kind or 2 kinds or more.

In the present invention, the addition amount ratio of the tetracarboxylic acid component to the diamine component used in the production of the polyimide resin is preferably 0.9 to 1.1 mol based on 1 mol of the tetracarboxylic acid component.

In the present invention, in addition to the tetracarboxylic acid component and the diamine component, a capping agent may be used in the production of the polyimide resin. The blocking agent is preferably a monoamine or dicarboxylic acid. The amount of the blocking agent to be introduced is preferably 0.0001 to 0.1 mol, more preferably 0.001 to 0.06 mol, based on 1 mol of the tetracarboxylic acid component. Examples of monoamine type blocking agents include methylamine, ethylamine, propylamine, butylamine, benzylamine, 4-methylbenzylamine, 4-ethylbenzylamine, 4-dodecylbenzylamine, 3-methylbenzylamine, 3-ethylbenzylamine, aniline, 3-methylaniline, 4-methylaniline, and the like, and benzylamine and aniline are preferable. The dicarboxylic acid-based blocking agent is preferably a dicarboxylic acid, and a part of the dicarboxylic acid may be blocked. Examples thereof include phthalic acid, phthalic anhydride, 4-chlorophthalic acid, tetrafluorophthalic acid, 2, 3-benzophenone dicarboxylic acid, 3, 4-benzophenone dicarboxylic acid, cyclohexane-1, 2-dicarboxylic acid, cyclopentane-1, 2-dicarboxylic acid, 4-cyclohexene-1, 2-dicarboxylic acid, and the like, and phthalic acid and phthalic anhydride are preferable.

The method for reacting the tetracarboxylic acid component with the diamine component is not particularly limited, and a known method can be used.

As a specific reaction method, there may be mentioned (1) a method comprising charging a tetracarboxylic acid component, a diamine component, and a reaction solvent into a reactor, stirring at 0 to 80℃for 0.5 to 30 hours, and then heating to conduct imidization; (2) Adding diamine component and reaction solvent into a reactor to dissolve the diamine component and the reaction solvent, adding tetracarboxylic acid component, stirring for 0.5-30 hours at the room temperature of 0-80 ℃ according to the requirement, and heating to perform imidization; (3) And a method in which the tetracarboxylic acid component, the diamine component, and the reaction solvent are charged into a reactor, and the imidization reaction is performed by immediately raising the temperature.

The reaction solvent used for the production of the polyimide resin may be one which does not interfere with the imidization reaction and which can dissolve the polyimide to be produced. Examples thereof include aprotic solvents, phenolic solvents, ether solvents, and carbonate solvents.

Specific examples of the aprotic solvent include amide solvents such as N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone (NMP), N-methylcaprolactam, 1, 3-dimethylimidazolidinone, and tetramethylurea; lactone solvents such as gamma-butyrolactone (GBL) and gamma-valerolactone; a phosphorus-containing amide solvent such as hexamethylphosphoramide and hexamethylphosphinotricin; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide, and sulfolane; ketone solvents such as acetone, cyclohexanone, and methylcyclohexanone; amine solvents such as picoline and pyridine; ester solvents such as 2-methoxy-1-methylethyl acetate, and the like.

Specific examples of the phenol-based solvent include phenol, o-cresol, m-cresol, p-cresol, 2, 3-dimethylphenol, 2, 4-dimethylphenol, 2, 5-dimethylphenol, 2, 6-dimethylphenol, 3, 4-dimethylphenol, 3, 5-dimethylphenol and the like.

Specific examples of the ether solvent include 1, 2-dimethoxyethane, bis (2-methoxyethyl) ether, 1, 2-bis (2-methoxyethoxy) ethane, bis [2- (2-methoxyethoxy) ethyl ] ether, tetrahydrofuran, and 1, 4-dioxane.

Specific examples of the carbonate-based solvent include diethyl carbonate, methylethyl carbonate, ethylene carbonate, propylene carbonate, and the like.

Among the above reaction solvents, aprotic solvents are preferable, and amide solvents and lactone solvents are more preferable. In addition, the above reaction solvents may be used alone or in combination of 2 or more.

The imidization reaction is preferably carried out by using a Dean-Stark trap or the like while removing water generated during the production. By doing so, the polymerization degree and the imidization rate can be further improved.

In the imidization reaction, a known imidization catalyst can be used. As the imidization catalyst, a base catalyst or an acid catalyst can be cited.

Examples of the base catalyst include organic base catalysts such as pyridine, quinoline, isoquinoline, α -picoline, β -picoline, 2, 4-lutidine, 2, 6-lutidine, trimethylamine, triethylamine (TEA), tripropylamine, tributylamine, triethylenediamine, imidazole, N-dimethylaniline, and N, N-diethylaniline; inorganic base catalysts such as potassium hydroxide, sodium hydroxide, potassium carbonate, sodium carbonate, potassium hydrogencarbonate, and sodium hydrogencarbonate.

Examples of the acid catalyst include crotonic acid, acrylic acid, trans-3-hexenoic acid, cinnamic acid, benzoic acid, methylbenzoic acid, hydroxybenzoic acid, terephthalic acid, benzenesulfonic acid, p-toluenesulfonic acid, naphthalenesulfonic acid, and the like. The imidization catalyst may be used alone or in combination of 2 or more.

Among the above, from the viewpoint of operability, a base catalyst is preferably used, an organic base catalyst is more preferably used, and at least 1 selected from the group consisting of triethylamine and triethylenediamine is more preferably used.

The temperature of the imidization reaction is preferably 120 to 250 ℃, more preferably 160 to 200 ℃, from the viewpoints of reaction rate, gelation inhibition, and the like. The reaction time is preferably 0.5 to 10 hours after the start of distillation of the produced water.

< Method for producing polyimide varnish and polyimide film >

The polyimide varnish of the present invention is prepared by dissolving the polyimide resin of the present invention in an organic solvent. That is, the polyimide varnish of the present invention contains the polyimide resin of the present invention and an organic solvent in which the polyimide resin is dissolved.

The organic solvent is not particularly limited as long as it dissolves the polyimide resin, and the above-mentioned compounds used as reaction solvents in the production of the polyimide resin are preferably used alone or in combination of 2 or more.

The polyimide varnish of the present invention may be a polyimide solution obtained by dissolving a polyimide resin obtained by a polymerization method in a reaction solvent, or may be obtained by diluting the polyimide solution with a solvent.

The polyimide resin of the present invention has solvent solubility, and thus can be prepared into a varnish of high concentration which is stable at room temperature. The polyimide varnish of the present invention preferably contains 5 to 40 mass% of the polyimide resin of the present invention, more preferably 10 to 30 mass%. The viscosity of the polyimide varnish is preferably 1 to 200pa·s, more preferably 1 to 100pa·s. The viscosity of the polyimide varnish was a value measured at 25℃using an E-type viscometer.

The polyimide varnish of the present invention may contain various additives such as an inorganic filler, an adhesion promoter, a release agent, a flame retardant, an ultraviolet stabilizer, a surfactant, a leveling agent, an antifoaming agent, a fluorescent whitening agent, a crosslinking agent, a polymerization initiator, and a photosensitizer, as far as the required properties of the polyimide film are not impaired.

The method for producing the polyimide varnish of the present invention is not particularly limited, and a known method can be used.

The method for producing the polyimide film of the present invention is not particularly limited, and a known method can be used. Examples of the method include a method of applying the varnish of the present invention to a support and heating the same. Specifically, a method of applying the varnish to a smooth support such as a glass plate, a metal plate, or a plastic, and then removing an organic solvent such as a reaction solvent or a dilution solvent contained in the varnish by heating is exemplified.

The coating method includes known coating methods such as spin coating, slit coating, and blade coating. Among them, slit coating is preferable from the viewpoint of improving chemical resistance and workability by controlling intermolecular orientation.

As a method for removing the organic solvent contained in the varnish by heating, it is preferable to evaporate the organic solvent at a temperature of 150 ℃ or lower to be non-tacky, and then dry the resultant mixture at a temperature of 200 to 500 ℃ or higher (not particularly limited) than the boiling point of the organic solvent to be used. Further, the drying is preferably performed under an air atmosphere or a nitrogen atmosphere. The pressure of the drying atmosphere may be any of reduced pressure, normal pressure, and increased pressure.

The method for peeling the polyimide film formed on the support from the support is not particularly limited, and examples thereof include a laser peeling method, a method using a sacrificial layer for peeling (a method of pre-coating a release agent on the surface of the support), and a method of adding a peeling agent.

< Method for producing second polyimide resin >

According to the present production method, the imide site in the imide-amic acid copolymer having the imide repeating structural unit and the amic acid repeating structural unit is imidized, whereby a polyimide resin can be obtained. The polyimide resin obtained is the polyimide resin described in the above [ polyimide resin ], and the preferable ranges are the same. The above imide-amic acid copolymer will be described below.

< Imide-amic acid copolymer >

The imide-amic acid copolymer of the present invention used in the present production method is a precursor of a polyimide resin, and preferably contains a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).

B ¹ and B ² are 2-valent groups, and any of B ¹ and B ² contains a group represented by the following formula (6). )

In the formula (1), a ¹ is at least 1 selected from the group consisting of a group represented by the formula (3) and a group represented by the formula (4), preferably contains a group represented by the formula (3), more preferably is a group represented by the formula (3).

In the formula (1) and the formula (2), B ¹ and B ² are a 2-valent group, preferably an optionally substituted 2-valent hydrocarbon group, more preferably an optionally substituted 2-valent aromatic hydrocarbon group. Either B ¹ or B ² contains a group represented by the following formula (6), preferably B ² contains a group represented by the following formula (6), and more preferably both B ¹ and B ² contain a group represented by the following formula (6). Further, it is more preferable that B ² is a group represented by the following formula (6).

In the formula (2), X ¹ and X ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, or an alkylsilyl group having 3 to 9 carbon atoms.

The molar ratio of the repeating unit represented by the formula (1) to the repeating unit represented by the formula (2) [ 1)/(2) ] is preferably 5/95 to 60/40.

(Process for producing imide-amic acid copolymer)

The imide-amic acid copolymer is preferably produced by a method having the following steps 1 and 2.

Step 1: reacting a tetracarboxylic acid component constituting the repeating unit represented by the formula (1) with a diamine component to obtain an oligomer having an imide repeating structural unit

Step 2: reacting the oligomer obtained in the step 1 with a tetracarboxylic acid component and a diamine component constituting the repeating unit represented by the formula (2) to obtain an imide-amic acid copolymer having an imide repeating structural unit and an amic acid repeating structural unit

By the production method having the steps 1 and 2, a copolymer which can form a polyimide film excellent in heat resistance, particularly, a polyimide film having a small weight loss at the time of high-temperature treatment and further excellent in laser peelability can be produced.

Hereinafter, a method for producing the imide-amic acid copolymer will be described.

(Tetracarboxylic acid component and diamine component)

The tetracarboxylic acid component constituting the repeating unit represented by the formula (1) contains at least 1 selected from the group consisting of the compound represented by the formula (a 11) and the compound represented by the formula (a 12). The tetracarboxylic acid component constituting the repeating unit represented by the formula (1) preferably contains a compound represented by the formula (a 11). The tetracarboxylic acid component constituting the repeating unit represented by the formula (1) is more preferably at least 1 selected from the group consisting of the compound represented by the formula (a 11) and the compound represented by the formula (a 12), and is more preferably the compound represented by the formula (a 11).

The compound represented by the formula (a 11) preferably contains a compound represented by the formula (a 111), more preferably a compound represented by the formula (a 111).

The diamine component constituting the repeating unit represented by the formula (1) is not limited, and preferably contains at least 1 selected from the group consisting of the compound represented by the formula (b 1) and the compound represented by the formula (b 2), more preferably contains the compound represented by the formula (b 1), and still more preferably is the compound represented by the formula (b 1).

The tetracarboxylic dianhydride and the diamine component constituting the repeating unit represented by the formula (1) may be contained in a range not to impair the effects of the present invention.

The tetracarboxylic acid component constituting the repeating unit represented by the formula (2) contains a compound represented by the formula (a 2). The tetracarboxylic acid component constituting the repeating unit represented by the formula (2) is preferably a compound represented by the formula (a 2).

The compound represented by the formula (a 2) preferably contains a compound represented by the formula (a 2 s), more preferably a compound represented by the formula (a 2 s).

The diamine component constituting the repeating unit represented by the formula (2) is not limited, and preferably contains at least 1 selected from the group consisting of the compound represented by the formula (b 1) and the compound represented by the formula (b 2), more preferably contains the compound represented by the formula (b 1), still more preferably contains the compound represented by the formula (b 1) and the compound represented by the formula (b 2).

The tetracarboxylic dianhydride and the diamine component constituting the repeating unit represented by the formula (2) may be contained in a range not to impair the effects of the present invention.

(Solvent)

The solvent used in the production of the copolymer may be used to dissolve the copolymer to be produced. Specific examples of the reaction solvent include those described in the above [ polyimide resin ]. Among the above reaction solvents, an amide-based solvent or a lactone-based solvent is preferable, an amide-based solvent is more preferable, and N-methyl-2-pyrrolidone is still more preferable. The above reaction solvents may be used alone or in combination of 2 or more.

(Process 1)

Step 1 is a step of reacting a tetracarboxylic acid component constituting the repeating unit represented by the formula (1) with a diamine component to obtain an oligomer having an imide repeating structural unit.

The tetracarboxylic acid component used in the step 1 contains a tetracarboxylic acid component constituting the repeating unit represented by the above formula (1).

The diamine component used in step 1 contains a diamine component constituting the repeating unit represented by formula (1).

The molar ratio of the diamine component to the tetracarboxylic acid component (diamine/tetracarboxylic acid) used in step 1 is preferably 0.9 to 2 moles, more preferably 1.01 to 2 moles, still more preferably 1.05 to 1.9 moles, and still more preferably 1.1 to 1.7 moles.

The method of reacting the tetracarboxylic acid component with the diamine component in step 1 to obtain the oligomer is not particularly limited, and a known method can be used. As a specific reaction method, the following description is given of < method for producing the first polyimide resin >.

In the imidization reaction, a known imidization catalyst can be used. As a specific example of the imidization catalyst, the preferable ranges are the same as those described in < method for producing a first polyimide resin >.

The oligomer obtained in step 1 has a repeating unit represented by formula (1).

The oligomer obtained in step 1 preferably has carboxyl groups at both ends of the main chain of the molecular chain. The carboxyl groups described herein also include derivatives.

By the above method, a solution containing an oligomer dissolved in a solvent can be obtained. The solution containing the oligomer obtained in step 1 may contain at least a part of the components used as the tetracarboxylic acid component and the diamine component in step 1 as unreacted monomers, as long as the effects of the present invention are not impaired.

(Process 2)

Step 2 is a step of reacting the oligomer obtained in step 1 with a tetracarboxylic acid component and a diamine component constituting the repeating unit represented by formula (2) to obtain an imide-amic acid copolymer having an imide repeating structural unit and an amic acid repeating structural unit.

The tetracarboxylic acid component used in step 2 contains a tetracarboxylic acid component constituting the repeating unit represented by the above formula (2).

The diamine component used in step 2 contains a diamine component constituting the repeating unit represented by formula (2).

The unreacted tetracarboxylic acid component remaining in the solution containing the oligomer obtained in step 1 may be used as the tetracarboxylic acid component in step 2, or the unreacted diamine component remaining in the solution containing the oligomer obtained in step 1 may be used as the diamine component in step 2.

In step 1, when the main chain of the molecular chain of the oligomer has amino groups at both ends, and the compound represented by the formula (b 1) is used as the diamine component used in step 1, only the tetracarboxylic acid component may be used in step 2.

In step 2, the method of reacting the oligomer obtained in step1 with the tetracarboxylic acid component and the diamine component constituting the repeating unit represented by formula (2) is not particularly limited, and a known method can be used.

Specific examples of the reaction method include (1) a method in which the oligomer, diamine component, tetracarboxylic acid component and solvent obtained in step 1 are charged into a reactor and stirred at a temperature of usually 0 to 120℃and preferably 5 to 80℃for 1 to 72 hours.

At 80℃or lower, the molecular weight of the copolymer obtained in step 2 does not change depending on the temperature history during polymerization, and the progress of thermal imidization can be suppressed, so that the copolymer can be stably produced.

The imide-amic acid copolymer is a copolymer having an amic acid repeating structural unit and an imide repeating structural unit, and is a product of addition polymerization reaction of the oligomer obtained in step 1 with the tetracarboxylic acid component and the diamine component in step 2.

By the above method, a copolymer solution containing the imide-amic acid copolymer dissolved in a solvent can be obtained.

The concentration of the copolymer in the obtained copolymer solution is usually in the range of 1 to 50 mass%, preferably 3 to 35 mass%, more preferably 10 to 30 mass%.

The number average molecular weight of the imide-amic acid copolymer is preferably 5,000 ～ 500,000 from the viewpoint of the mechanical strength of the polyimide film obtained. The number average molecular weight of the copolymer can be obtained, for example, from a standard polymethyl methacrylate (PMMA) conversion measured by gel permeation chromatography.

(Copolymer varnish, method for producing polyimide resin, and method for producing polyimide film)

In the second method for producing a polyimide resin, the polyimide resin is obtained by imidizing the amic acid site in the copolymer, which is a precursor of the polyimide resin, and usually, the polyimide resin is obtained in a film shape by subjecting a copolymer solution (varnish) to imidization and molding the resultant product into a film shape. Therefore, in this item, a method for producing a polyimide film, which is a copolymer solution (varnish) and a polyimide resin having a film shape, will be described.

The copolymer varnish is a precursor of a polyimide resin, and is obtained by dissolving a copolymer having an imide repeating structural unit and an amic acid repeating structural unit in an organic solvent. That is, the copolymer varnish contains a copolymer and an organic solvent, and the copolymer is dissolved in the organic solvent.

The organic solvent is not particularly limited as long as it dissolves the copolymer, and it is preferable to use the compound used as a solvent in the production of the copolymer alone or in combination of 2 or more kinds.

The copolymer varnish may be the copolymer solution itself or may be obtained by further adding a solvent for dilution to the copolymer solution.

From the viewpoint of more efficiently imidizing the amic acid sites in the copolymer, the copolymer varnish can further comprise an imidization catalyst and a dehydration catalyst. The imidization catalyst is preferably an imidization catalyst having a boiling point of 40 ℃ or more and 180 ℃ or less, and more preferably an amine compound having a boiling point of 180 ℃ or less. When the imidization catalyst has a boiling point of 180 ℃ or less, there is no concern that the film will be colored and the appearance will be impaired when the film is dried at a high temperature after the film is formed. In addition, if the imidization catalyst has a boiling point of 40 ℃ or higher, the possibility of volatilization before imidization is sufficiently performed can be avoided.

As the amine compound suitable as an imidization catalyst, pyridine or picoline may be mentioned. The imidization catalyst may be used singly or in combination of 2 or more.

Examples of the dehydration catalyst include anhydrides such as acetic anhydride, propionic anhydride, n-butyric anhydride, benzoic anhydride and trifluoroacetic anhydride; and carbodiimide compounds such as dicyclohexylcarbodiimide. These may be used alone or in combination of 2 or more.

The copolymer contained in the copolymer varnish has solvent solubility, and thus a varnish of high concentration can be produced. The copolymer varnish preferably contains 5 to 40 mass% of the copolymer, more preferably 10 to 30 mass%. The viscosity of the copolymer varnish is preferably 0.1 to 100pa·s, more preferably 0.1 to 20pa·s. The viscosity of the copolymer varnish was a value measured at 25℃using an E-type viscometer.

The copolymer varnish may contain various additives other than the above resin additives, such as an inorganic filler, an adhesion promoter, a flame retardant, an ultraviolet stabilizer, a leveling agent, an antifoaming agent, a fluorescent whitening agent, a crosslinking agent, a polymerization initiator, a photosensitive agent, and an adhesion imparting agent, as far as the required properties of the polyimide film are not impaired.

The method for producing the varnish is not particularly limited, and a known method can be used.

The copolymer varnish preferably further contains an imidazole compound represented by the following general formula (7).

By containing the imidazole compound represented by the above general formula (7), a polyimide film composed of a polyimide resin having a structural unit a derived from tetracarboxylic dianhydride, which includes a structural unit (A1) and a structural unit (A2), and a structural unit B derived from diamine, which includes a structural unit (B1), can be efficiently obtained. The obtained polyimide film is excellent in heat resistance and strength.

In the formula (7), L ¹ and L ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, or a hydroxyl group, but are preferably at least 1 selected from the group consisting of a hydrogen atom and an alkyl group having 1 to 6 carbon atoms, more preferably at least 1 selected from the group consisting of a hydrogen atom and a methyl group, and still more preferably a hydrogen atom. More preferably, L ¹ is methyl and L ² is a hydrogen atom.

In the formula (7), n is an integer of 1 to 4, preferably an integer of 1 or 2, and more preferably 1.

Among the imidazole compounds represented by the above general formula (7), at least 1 selected from the group consisting of imidazole compounds represented by the following formula (7-1) and imidazole compounds represented by the following formula (7-2) is preferable, and imidazole compounds represented by the following formula (7-1) are more preferable.

The imidazole compound represented by the following formula (7-1) is 1-benzyl-2-methylimidazole, and the imidazole compound represented by the following formula (7-2) is 1-benzyl imidazole. That is, the imidazole compound represented by the general formula (7) is preferably at least 1 selected from the group consisting of 1-benzyl imidazole and 1-benzyl-2-methylimidazole, and more preferably 1-benzyl-2-methylimidazole.

The content of the imidazole compound represented by the formula (7) is preferably 0.1 to 100 parts by mass, more preferably 1.0 to 50 parts by mass, still more preferably 4.0 to 40 parts by mass, and still more preferably 10 to 30 parts by mass, per 100 parts by mass of the imide-amic acid copolymer in the copolymer varnish.

The method for producing the polyimide film of the present invention is not particularly limited, and a known method can be used. Examples of the method include a method of applying the varnish to a support and heating the same. Specifically, a method of applying the varnish to a smooth support such as a glass plate, a metal plate, or a plastic, and then removing an organic solvent such as a reaction solvent or a dilution solvent contained in the varnish by heating is exemplified. When the copolymer varnish is used, the organic solvent is removed and then further heated to effect imidization.

The heating temperature for drying the copolymer varnish to obtain a copolymer film is preferably 50 to 150 ℃. The heating temperature at the time of imidization by heating the copolymer may be selected from the range of preferably 200 to 500 ℃, more preferably 250 to 450 ℃, and still more preferably 300 to 400 ℃. The heating time is usually 1 minute to 6 hours, preferably 5 minutes to 2 hours, and more preferably 15 minutes to 1 hour.

The heating atmosphere includes air, nitrogen, oxygen, hydrogen, and a nitrogen/hydrogen mixed gas, and in order to suppress coloring of the obtained polyimide resin, nitrogen having an oxygen concentration of 100ppm or less and a nitrogen/hydrogen mixed gas having a hydrogen concentration of 0.5% or less are preferable.

The method of imidization is not limited to thermal imidization, and chemical imidization may be used.

The method of peeling the polyimide film formed on the support from the support is not particularly limited, and examples thereof include a laser peeling method, a method using a sacrificial layer for peeling (a method of coating a release agent on the surface of the support in advance), and a method of adding a release agent.

[ Polyimide film ]

The polyimide film of the present invention contains the above polyimide resin. Therefore, the polyimide film of the present invention is excellent in heat resistance, particularly, is small in weight loss during high-temperature treatment, and is excellent in laser peelability.

The thickness of the polyimide film of the present invention may be appropriately selected depending on the application, etc., and is preferably 1 to 250. Mu.m, more preferably 5 to 100. Mu.m, still more preferably 8 to 80. Mu.m, still more preferably 10 to 80. Mu.m. The thickness of 1 to 250 μm can be practically used as a self-supporting film.

The thickness of the polyimide film can be easily controlled by adjusting the solid concentration and viscosity of the varnish.

The polyimide film of the present invention has excellent heat resistance and particularly has small weight loss during high-temperature treatment. The polyimide film of the present invention has suitable physical properties as described below.

The weight loss ratio when maintained at 430℃for 1 hour is preferably less than 1.0%, more preferably less than 0.5%, still more preferably less than 0.3%.

The glass transition temperature is preferably 410℃or higher, more preferably 420℃or higher, and still more preferably 430℃or higher.

The physical property values in the present invention can be measured by the methods described in examples.

The polyimide film of the present invention is suitable for use as a film for various members such as a color filter, a flexible display, a semiconductor device, and an optical member. The polyimide film of the present invention is suitable for use as a substrate for display devices such as liquid crystal displays and OLED displays, and is more suitable for use as a transparent substrate constituting a display device.

[ Image display device ]

The image display device of the present invention comprises the polyimide film of the present invention as a transparent substrate.

The image display device of the present invention includes, for example, a transparent substrate made of the polyimide film of the present invention, and a display portion provided on the transparent substrate.

The display portion is not particularly limited, and examples thereof include a display element using a TFT element, an organic EL element, a color filter, an LED, a transistor, an electron emitting element, electronic ink, an electrophoretic element, a GLV (grating light valve ), a MEMS (micro electro MECHANICAL SYSTEM), a display element using a DMD (digital micromirror device ), a DMS (digital micro shutter, digital micro shutter), an IMOD (interferometric modulator ) element, an electrowetting (electrowetting) element, a piezoelectric ceramic display, and a carbon nanotube.

Examples of the image display device of the present invention include a liquid crystal display, an OLED display, and a touch panel.

The image display device of the present invention can be manufactured based on known information, in addition to using the polyimide film of the present invention as a transparent substrate.

The image display device of the present invention uses the polyimide film of the present invention having excellent heat resistance as a transparent substrate, and therefore is less likely to cause cracking of an inorganic film, coloring of the transparent substrate, and the like, and has excellent reliability.

Examples

The present invention will be specifically described below with reference to examples. The present invention is not limited by these examples.

[ Film Properties and evaluation ]

The physical properties of the polyimide films obtained in examples and comparative examples were measured by the methods shown below. Further, the polyimide film was evaluated by the following method. The polyimide film used for measurement and evaluation of the physical properties was a film peeled off by the following "(8) minimum energy density peelable method". The film which could not be peeled off by this method was immersed in water at 40℃for 5 minutes and peeled off, and then the surface was dehydrated with a dust-free paper (CLEAN PAPER), and then the film was heated in a hot air dryer at 80℃for 10 minutes to remove the moisture, and then used for measurement and evaluation of various physical properties.

(1) Film thickness

The film thickness of the polyimide films of examples and comparative examples was measured using a contact displacement sensor "SA-S110" manufactured by ltd.

< Optical Property >

(2) Total light transmittance and Yellowness Index (YI)

The total light transmittance and YI of the polyimide films of examples and comparative examples were measured on the polyimide film peeled from the glass plate, and the total light transmittance was measured according to JIS K7361-1 and YI was measured according to ASTM E313-05 (D light source, 65 °) using NIPPON DENSHOKU INDUSTRIES Co., ltd. Color/haze simultaneous measuring instrument "COH 7700".

(3) Thickness retardation (Rth) (evaluation of optical isotropy)

The thickness retardation (Rth) of the polyimide films of examples and comparative examples was measured by using an ellipsometer "M-220" manufactured by japan spectroscopic corporation, for the polyimide film peeled from the glass plate. The thickness phase difference was measured at a measurement wavelength of 590 nm. Rth is expressed by the following formula, where nx is the maximum refractive index in the plane of the polyimide film, ny is the minimum refractive index, nz is the refractive index in the thickness direction, and d is the film thickness.

Rth＝[{(nx+ny)/2}-nz]×d

< Thermal Property (Heat resistance) >)

(4) Glass transition temperature (Tg)

The glass transition temperatures (Tg) of the polyimide films of examples and comparative examples were determined by the following methods using the polyimide films peeled from the glass plate as test pieces. Using a thermo-mechanical analysis device "TMA7100C", manufactured by HITACHI HIGH-Tech corporation, under the conditions of a test piece size of 4 mm. Times.20 mm, a load of 0.1N, a heating rate of 10℃per minute, the temperature was raised to a temperature sufficient to remove residual stress in a tensile mode, and then cooled to room temperature. Thereafter, the elongation of the test piece was measured under the same conditions as in the above-described treatment for removing residual stress, and the glass transition temperature was obtained by extrapolation of the turning point of the elongation.

(5) 1% Weight loss temperature (Td 1%)

The polyimide films of examples and comparative examples were subjected to the following method using a polyimide film peeled from a glass plate as a sample at a 1% weight loss temperature (Td 1%). The apparatus "NEXTASTA RV" was also measured by using a differential thermogravimetry measurement apparatus manufactured by HITACHI HIGH-Tech corporation. The sample was heated from 40℃to 150℃at a heating rate of 10℃per minute, kept at 150℃for 30 minutes to remove water, and then heated to 550℃at 10℃per minute. The temperature at 1% loss in weight was taken as 1% loss in weight temperature (Td 1%) compared to the weight after 30 minutes at 150 ℃. The larger the weight loss temperature value, the more excellent the heat resistance.

(6) Weight loss rate at 430 DEG C

The weight loss ratio at 430℃of the polyimide films of examples and comparative examples was determined by the method described below using the polyimide film peeled from the glass plate as a sample. The apparatus "NEXTASTA RV" was also measured by using a differential thermogravimetry measurement apparatus manufactured by HITACHI HIGH-Tech corporation. The sample was heated from 40℃to 150℃at a heating rate of 10℃per minute, kept at 150℃for 30 minutes to remove water, and then heated to a predetermined temperature (430 ℃) at 10℃per minute, and kept at that temperature for 1 hour. The weight loss ratio at 430℃was defined as the ratio of the weight reduced during the period of 1 hour at 430℃to the weight before 1 hour. The smaller the value of the weight loss ratio at 430℃is, the more excellent the heat resistance is.

< Laser Peel off (LLO) Peel off Property >

(7) Transmittance at wavelength 308nm

The transmittance at a wavelength of 308nm of the polyimide films of examples and comparative examples was determined by the method described below for the polyimide film peeled from the glass plate. The measurement was performed using an ultraviolet visible near infrared spectrophotometer "UV-3100PC" manufactured by Shimadzu corporation. The smaller the light transmittance value at a wavelength of 308nm, the more excellent the LLO peelability.

In addition, "< 0.1" in table 1 means "less than 0.1%".

(8) Minimum energy density of strippable

LLO peelability was evaluated by irradiating excimer laser light (oscillation gas: xeCl, wavelength 308 nm) from the glass plate side of the laminate (glass plate/polyimide film) obtained in examples and comparative examples. LLO conditions were set to be an overlap of 50%, a frequency of 60Hz, and a beam size of 14 mm. Times.1 mm, and laser irradiation was performed so as to stepwise increase the energy density per 10mJ/cm ², whereby the minimum energy density of the releasable polyimide was measured. The results are shown in tables 1 and 2. In the examples and comparative examples of the present test, AN-wizusFC (0.5 mmt) was used for the glass plate.

The irradiation was terminated when the energy density became 400mJ/cm ², and the evaluation result by the non-peelable person was "non-peelable".

The smaller the minimum energy density of the strippable polyimide, the more excellent the LLO strippability. Namely, the efficiency is good and the productivity is excellent.

< Abbreviation of component and the like >

The tetracarboxylic acid component and the diamine component used in examples and comparative examples, and their abbreviations are as follows.

(Tetracarboxylic acid component)

DNDA: ( 4arH,8 ach) -decahydro-1 t,4t:5c,8 c-dimethylnaphthalene-2 t,3t,6c,7 c-tetracarboxylic dianhydride (DAXIN company; a compound represented by the formula (a 111) )

BODA: bicyclooctane-2, 3,5, 6-tetracarboxylic acid anhydride (DAXIN, compound represented by the formula (a 12))

S-BPDA:3,3', 4' -Biphenyltetracarboxylic dianhydride (a compound represented by formula (a 2 s) manufactured by Mitsubishi chemical Co., ltd.)

CpODA: norbornane-2-spiro-alpha-cyclopentanone-alpha' -spiro-2 "-norbornane-5, 5",6 "-tetracarboxylic dianhydride (manufactured by ENEOS Co., ltd.)

(Diamine component)

BAFL:9, 9-bis (4-aminophenyl) fluorene (manufactured by JFE Chemical Corporation, compound represented by formula (b 11))

TFMB:2,2' -bis (trifluoromethyl) benzidine (SEIKA CORPORATION. A compound represented by formula (b 2))

The abbreviations for the solvents and catalysts used in the examples and comparative examples are as follows.

GBL: gamma-butyrolactone (Mitsubishi chemical Co., ltd.)

NMP: n-methyl-2-pyrrolidone (manufactured by Tokyo pure medicine industry Co., ltd.)

TEA: triethylamine (manufactured by kanto chemical Co., ltd.)

TEDA: triethylenediamine (Tokyo chemical industry Co., ltd.)

< Production of polyimide resin, varnish and polyimide film >

Example 1

To a 1L 5-neck round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen gas introduction pipe, a dean-Stark trap equipped with a cooling pipe, a thermometer, and a glass end cap were charged 13.938g (0.040 mol) of BAFL, 19.214g (0.060 mol) of TFMB, and 93.686g of GBL, and the mixture was stirred at a rotational speed of 200rpm under a nitrogen atmosphere at a temperature of 70℃in the system to obtain a solution.

To this solution, 18.137g (0.060 mol) of DNDA, 11.769g (0.040 mol) of s-BPDA, and 19.908g of GBL were added all at once, and then 5.060g of TEA, 0.056g of TEDA, and 3.513g of GBL were added as imidization catalysts, and the mixture was heated by a sheathed resistance heater (MANTLE HEATER) to raise the temperature in the reaction system to 190℃over about 20 minutes. The distilled components were collected, and the rotational speed was adjusted in accordance with the increase in viscosity, while the temperature in the reaction system was kept at 190℃for 5 hours to reflux.

Thereafter, 417.978g of GBL was added, the reaction system was cooled to 120℃and stirred for about 3 hours to homogenize the mixture, thereby obtaining a polyimide varnish having a solid content of 10% by mass. Then, the obtained polyimide varnish was applied to a glass plate, and the resultant was kept at 80℃for 20 minutes using a heating plate, and then, the solvent was evaporated by heating at 400℃for 30 minutes in a hot air dryer under a nitrogen atmosphere, to obtain a polyimide film. The physical properties and evaluation results of the film are shown in Table 1.

Examples 2 to 7 and comparative examples 1 to 5

A polyimide film was obtained in the same manner as in example 1, except that the tetracarboxylic acid component and the diamine component in example 1 were changed to those described in table 1. The physical properties and evaluation results of the film are shown in Table 1.

TABLE 1

As shown in table 1, the polyimide film of examples was excellent in heat resistance, particularly, the weight loss at the time of high temperature treatment was small, and further, the laser peelability was also excellent.

Example 8

To a 500mL 5-port round-bottom flask equipped with a stainless steel half-moon shaped stirring blade, a nitrogen gas inlet pipe, a dean-Stark trap equipped with a cooling pipe, a thermometer, and a glass end cap were charged 9.607g (0.030 mol) of TFMB, 10.454g (0.030 mol) of BAFL and 84.394g of NMP, and the mixture was stirred at a rotation speed of 200rpm under a nitrogen gas atmosphere at a temperature of 70℃in the system to obtain a solution.

To this solution, 15.114g (0.050 mol) of DNDA and 17.934g of NMP were added at a time, and then, 0.253g of TEA and 3.165g of NMP as imidization catalysts were added and heated by a sheath resistance heater, thereby raising the temperature in the reaction system to 190℃over about 20 minutes. The distilled components were collected while maintaining the temperature in the reaction system at 190℃for 1 hour under reflux. Thereafter, 98.368g of NMP was added, and the temperature in the reaction system was cooled to 50℃to obtain a solution containing an oligomer having an imide repeating structural unit.

To the obtained solution were added 14.711g (0.050 mol) of s-BPDA, 12.810g (0.040 mol) of TFMB and 39.713g of NMP at once, and stirred at 50℃for 5 hours. Thereafter, NMP was added so that the solid content concentration became about 10 mass% and homogenized, and further 1-benzyl-2-imidazole was added so that the mass of NMP became 15 parts by mass with respect to 100 parts by mass of the imide-amic acid copolymer and homogenized, whereby a varnish comprising a copolymer having an imide repeating structural unit and an amic acid repeating structural unit (imide-amic acid copolymer) was obtained.

Then, the obtained varnish was coated on a glass plate by spin coating, maintained at 80 ℃ for 20 minutes by a heating plate, and then the solvent was evaporated by heating at 400 ℃ for 60 minutes in a hot air dryer under a nitrogen atmosphere, to obtain a polyimide film. The physical properties and evaluation results of the film are shown in Table 2.

TABLE 2

As shown in table 2, the polyimide film of examples was excellent in heat resistance, particularly, the weight loss at the time of high temperature treatment was small, and further, the laser peelability was also excellent.

Claims

1. A polyimide resin having a structural unit A derived from tetracarboxylic dianhydride and a structural unit B derived from diamine,

The structural unit B comprises a structural unit (B1) derived from a compound represented by the following general formula (B1),

In the formula (b 1), R is independently a hydrogen atom, a fluorine atom, an alkyl group having 1 to 5 carbon atoms, a trifluoromethyl group or a hydroxyl group.

2. The polyimide resin according to claim 1, wherein the ratio of the structural unit (B1) in the structural unit B is 15 mol% or more.

3. The polyimide resin according to claim 1 or 2, wherein the structural unit B further comprises a structural unit (B2) derived from a compound represented by the following formula (B2),

4. The polyimide resin according to claim 3, wherein the molar ratio [ (B1)/(B2) ] of the structural unit (B1) to the structural unit (B2) in the structural unit B is 15/85 to 70/30.

5. The polyimide resin according to any one of claims 1 to 4, wherein the structural unit (A11) comprises a structural unit (A111) derived from a compound represented by the following formula (a 111),

6. The polyimide resin according to any one of claims 1 to 5, wherein the structural unit (A2) comprises a structural unit (A2 s) derived from a compound represented by the following formula (A2 s),

7. The polyimide resin according to any one of claims 1 to 6, wherein the structural unit (B1) comprises a structural unit (B11) derived from a compound represented by the following formula (B11),

8. The polyimide resin according to any one of claims 1 to 7, wherein the molar ratio [ (A1)/(A2) ] of the structural unit (A1) to the structural unit (A2) in the structural unit A is from 30/70 to 85/15.

9. A varnish prepared by dissolving the polyimide resin according to any one of claims 1 to 8 in an organic solvent.

10. An imide-amic acid copolymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2),

Wherein A ¹ is at least 1 selected from the group consisting of a group represented by the following formula (3) and a group represented by the following formula (4), A ² is a group represented by the following formula (5),

B ¹ and B ² are a 2-valent group, and any of B ¹ and B ² contains a group represented by the following formula (6),

X ¹ and X ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms or an alkylsilyl group having 3 to 9 carbon atoms,

11. A varnish prepared by dissolving the imide-amic acid copolymer described in claim 10 in an organic solvent.

12. The varnish according to claim 11, further comprising an imidazole compound represented by the following general formula (7),

In the formula (7), L ¹ and L ² are each independently a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a carboxyl group, a hydroxyl group, and n is an integer of 1 to 4.

13. A polyimide resin obtained by imidizing the amic acid moiety in the copolymer according to claim 10.

14. A polyimide film comprising the polyimide resin according to any one of claims 1 to 8 and 13.

15. The polyimide film according to claim 14, which has a weight loss ratio of less than 1.0% when kept at 430 ℃ for 1 hour, and a glass transition temperature of 410 ℃ or higher.

16. The polyimide film according to claim 14 or 15, which is used as a transparent substrate constituting a display device.

17. A method for producing a polyimide film, wherein the varnish according to claim 9, 11 or 12 is applied to a support and heated.

18. An image display device comprising the polyimide film according to any one of claims 14 to 16 as a transparent substrate.