JP6631804B2 - Method for producing resin thin film and composition for forming resin thin film - Google Patents

Description

  The present invention relates to a method for producing a resin thin film and a composition for forming a resin thin film, a resin thin film obtained therefrom, and a method for reducing the retardation of the resin thin film, and more specifically, particularly for a display substrate such as a flexible display substrate. The present invention relates to a method for producing a resin thin film suitable for use and a composition for forming a resin thin film.

In recent years, with the rapid progress of electronics such as liquid crystal displays and organic electroluminescence displays, devices have been required to be thinner, lighter, and more flexible.
In these devices, various electronic elements, such as thin film transistors and transparent electrodes, are formed on a glass substrate. By replacing this glass material with a flexible and lightweight resin material, the device itself can be made thinner and lighter. And flexibility. As a candidate for such a resin material, polyimide has attracted attention, and various reports on a polyimide film have been made (for example, see Patent Documents 1 and 2).

JP-A-60-188427 JP-A-58-208322 International Publication No. 2011/149018 pamphlet

  When a polyimide resin material is used as a substrate for a display, it is desirable and required that the resin material not only has excellent transparency but also has low retardation as one of required performances. Even for a flexible display substrate, it is necessary to satisfy these required performances in addition to high flexibility (flexibility). Here, the retardation (phase difference) refers to the product of the birefringence (difference between two orthogonal refractive indexes) and the film thickness. This numerical value, particularly the retardation in the thickness direction, is an important factor affecting the viewing angle characteristics. It is a numerical value. It is known that a large retardation value can cause deterioration in display quality of a display (for example, see Patent Document 3).

The present invention has been made in view of such circumstances, and is not only excellent in heat resistance and flexibility, but also has a characteristic of low retardation, particularly a resin thin film suitable as a substrate of a flexible device. It is an object of the present invention to provide a method for producing the same, a resin thin film, and a composition for forming a resin thin film that provides such a resin thin film.
In particular, the present invention is not only excellent in heat resistance and flexibility, but also has a characteristic of low retardation, and is also excellent in transparency, suitable as a base film of a display substrate, particularly as a base film of a flexible display substrate. It is another object of the present invention to provide a method for producing a resin thin film having excellent performance, a resin thin film, and a composition for forming a resin thin film that provides such a resin thin film.
Another object of the present invention is to provide a method for reducing the retardation of a resin thin film that can be used as a substrate for a flexible device or the like.

  The present inventors have conducted intensive studies to achieve the above object, and as a result, a resin thin film obtained by mixing silicon dioxide with a polyimide having a monomer unit having a specific structure has excellent heat resistance, low retardation, and further flexibility. It also has the characteristic of being excellent, and by setting the blending amount of the silicon dioxide within a predetermined range, it is possible to realize a resin thin film having excellent heat resistance, low retardation, excellent flexibility, and excellent transparency. And completed the present invention.

〔式中、Ｂ^１は、式（Ｘ−１）〜（Ｘ−１２）からなる群から選ばれる４価の基を表す。

（式中、複数のＲは、互いに独立して、水素原子またはメチル基を表し、＊は結合手を表す。）〕
第３観点として、前記含フッ素芳香族ジアミンが、式（Ａ１）で表されるジアミンを含む、第１観点または第２観点に記載の方法に関する。

（式中、Ｂ^２は、式（Ｙ−１）〜（Ｙ−３４）からなる群から選ばれる２価の基を表す。）

（式中、＊は結合手を表す。）
第４観点として、前記ポリイミドが、式（２）で表されるモノマー単位を含む、第１観点に記載の方法に関する。

第５観点として、前記ポリイミドと前記二酸化ケイ素粒子の質量比が、７：３〜３：７である、第１観点乃至第４観点のうちいずれか一項に記載の方法に関する。
第６観点として、前記平均粒子径が、６０ｎｍ以下である、第１観点乃至第５観点のうちいずれか一項に記載の方法に関する。
第７観点として、第１観点乃至第６観点のうちいずれか一項に記載の方法により製造された樹脂薄膜に関する。
第８観点として、脂環式テトラカルボン酸二無水物を含むテトラカルボン酸二無水物成分と含フッ素芳香族ジアミンを含むジアミン成分とを反応させて得られるポリアミック酸をイミド化して得られるポリイミド、
窒素吸着法により測定された比表面積値から算出される平均粒子径が１００ｎｍ以下である二酸化ケイ素粒子、及び
有機溶媒
を含む樹脂薄膜形成用組成物に関する。
第９観点として、前記脂環式テトラカルボン酸二無水物が、式（Ｃ１）で表されるテトラカルボン酸二無水物を含む、第８観点に記載の樹脂薄膜形成用組成物に関する。

〔式中、Ｂ^１は、式（Ｘ−１）〜（Ｘ−１２）からなる群から選ばれる４価の基を表す。

（式中、複数のＲは、互いに独立して、水素原子またはメチル基を表し、＊は結合手を表す。）〕
第１０観点として、前記含フッ素芳香族ジアミンが、式（Ａ１）で表されるジアミンを含む、第８観点または第９観点に記載の樹脂薄膜形成用組成物に関する。

（式中、Ｂ^２は、式（Ｙ−１）〜（Ｙ−３４）からなる群から選ばれる２価の基を表す。）

（式中、＊は結合手を表す。）
第１１観点として、前記ポリイミドが、式（２）で表されるモノマー単位を含む、第８観点に記載の樹脂薄膜形成用組成物。

第１２観点として、前記ポリイミドと前記二酸化ケイ素粒子の質量比が、７：３〜３：７である、第８観点乃至第１１観点のうちいずれか一項に記載の樹脂薄膜形成用組成物に関する。
第１３観点として、前記平均粒子径が、６０ｎｍ以下である、第８観点乃至第１２観点のうちいずれか一項に記載の樹脂薄膜形成用組成物に関する。
第１４観点として、樹脂薄膜のリタデーションを低減する方法であって、
脂環式テトラカルボン酸二無水物を含むテトラカルボン酸二無水物成分と含フッ素芳香族ジアミンを含むジアミン成分とを反応させて得られるポリアミック酸をイミド化して得られるポリイミド、
窒素吸着法により測定された比表面積値から算出される平均粒子径が１００ｎｍ以下である二酸化ケイ素粒子、及び
有機溶媒
を含む樹脂薄膜形成用組成物を用いて樹脂薄膜を形成することを特徴とする方法に関する。That is, the present invention provides, as a first aspect, a method for producing a resin thin film,
A polyimide obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride with a diamine component containing a fluorinated aromatic diamine,
The present invention relates to a method characterized by using a composition for forming a resin thin film containing a silicon dioxide particle having an average particle diameter of 100 nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and an organic solvent.
As a second aspect, the present invention relates to the method according to the first aspect, wherein the alicyclic tetracarboxylic dianhydride includes a tetracarboxylic dianhydride represented by the formula (C1).

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-1) to (X-12).

(In the formula, a plurality of Rs independently represent a hydrogen atom or a methyl group, and * represents a bond.)
As a third aspect, the present invention relates to the method according to the first aspect or the second aspect, wherein the fluorinated aromatic diamine contains a diamine represented by the formula (A1).

(In the formula, B ² represents a divalent group selected from the group consisting of formulas (Y-1) to (Y-34).)

(In the formula, * represents a bond)
As a fourth aspect, the present invention relates to the method according to the first aspect, wherein the polyimide contains a monomer unit represented by Formula (2).

As a fifth aspect, the present invention relates to the method according to any one of the first to fourth aspects, wherein a mass ratio between the polyimide and the silicon dioxide particles is 7: 3 to 3: 7.
As a sixth aspect, the present invention relates to the method according to any one of the first aspect to the fifth aspect, wherein the average particle diameter is 60 nm or less.
As a seventh aspect, the present invention relates to a resin thin film manufactured by the method according to any one of the first to sixth aspects.
As an eighth aspect, a polyimide obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride with a diamine component containing a fluorine-containing aromatic diamine,
The present invention relates to a composition for forming a resin thin film containing silicon dioxide particles having an average particle size of 100 nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and an organic solvent.
As a ninth aspect, the present invention relates to the composition for forming a resin thin film according to the eighth aspect, wherein the alicyclic tetracarboxylic dianhydride includes a tetracarboxylic dianhydride represented by the formula (C1).

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-1) to (X-12).

(In the formula, a plurality of Rs independently represent a hydrogen atom or a methyl group, and * represents a bond).
As a tenth aspect, the present invention relates to the composition for forming a resin thin film according to the eighth or ninth aspect, wherein the fluorinated aromatic diamine contains a diamine represented by the formula (A1).

(In the formula, B ² represents a divalent group selected from the group consisting of formulas (Y-1) to (Y-34).)

(In the formula, * represents a bond)
As a eleventh aspect, the composition for forming a resin thin film according to the eighth aspect, wherein the polyimide contains a monomer unit represented by the formula (2).

As a twelfth aspect, the present invention relates to the composition for forming a resin thin film according to any one of the eighth to eleventh aspects, wherein the mass ratio of the polyimide and the silicon dioxide particles is 7: 3 to 3: 7. .
As a thirteenth aspect, the present invention relates to the composition for forming a resin thin film according to any one of the eighth to twelfth aspects, wherein the average particle diameter is 60 nm or less.
As a fourteenth aspect, there is provided a method for reducing the retardation of a resin thin film,
A polyimide obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride with a diamine component containing a fluorinated aromatic diamine,
Forming a resin thin film using a silicon dioxide particle having an average particle diameter of 100 nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and a resin thin film forming composition containing an organic solvent. About the method.

According to the method for producing a resin thin film according to one embodiment of the present invention using the composition for forming a resin thin film according to one embodiment of the present invention, the resin thin film has a low coefficient of linear expansion, excellent heat resistance, and low retardation. And a resin thin film having excellent flexibility can be formed with good reproducibility.
In particular, according to the method for producing a resin thin film according to another embodiment of the present invention using the composition for forming a resin thin film according to another embodiment of the present invention, the resin thin film has a low coefficient of linear expansion and heat resistance It is possible to form a resin thin film having excellent transparency, high transparency and low retardation, and further excellent flexibility.
The resin thin film according to the present invention exhibits a low coefficient of linear expansion, high transparency (high light transmittance, low yellowness), low retardation, and excellent flexibility. It can be suitably used as a substrate.
Further, according to the method for reducing the retardation of a resin thin film according to the present invention, the retardation of the resin thin film can be effectively reduced.
Such a production method, a composition, a resin thin film, and a method for reducing retardation according to the present invention have characteristics such as high flexibility, low linear expansion coefficient, high transparency (high light transmittance, low yellowness), and low retardation. Can sufficiently cope with the progress in the field of flexible device substrates, in particular, flexible display substrates, in which the following is required.

Hereinafter, the present invention will be described in detail.
The resin thin film forming composition used in the method for producing a resin thin film of the present invention contains the following specific polyimide, silicon dioxide particles and an organic solvent, and the resin thin film forming composition is also an object of the present invention. .

[Polyimide]
The polyimide used in the present invention is obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride with a diamine component containing a fluorine-containing aromatic diamine. Polyimide.
Among them, the alicyclic tetracarboxylic dianhydride includes a tetracarboxylic dianhydride represented by the following formula (C1), and the fluorinated aromatic diamine is represented by the following formula (A1). It is preferable that the diamine contains a diamine.

〔式中、Ｂ^１は、式（Ｘ−１）〜（Ｘ−１２）からなる群から選ばれる４価の基を表す。

（式中、複数のＲは、互いに独立して、水素原子またはメチル基を表し、＊は結合手を表す。）〕

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-1) to (X-12).

(In the formula, a plurality of Rs independently represent a hydrogen atom or a methyl group, and * represents a bond.)

（式中、Ｂ^２は、式（Ｙ−１）〜（Ｙ−３４）からなる群から選ばれる２価の基を表す。）

（式中、＊は結合手を表す。）

(In the formula, B ² represents a divalent group selected from the group consisting of formulas (Y-1) to (Y-34).)

(In the formula, * represents a bond)

Among the tetracarboxylic dianhydrides represented by the formula (C1), B ¹ in the formula is represented by the formulas (X-1), (X-4), (X-6), and (X-7). Preferably, the compound is
Also among the diamine represented by the above (A1), ^{B 2} has the formula (Y-12) in the formula is preferably a compound represented by (Y-13).
As a preferred example, a polyimide obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride represented by the above formula (C1) with a diamine represented by the above formula (A1) will be described later. And a monomer unit represented by the following formula (2).

The object of the present invention has a low coefficient of linear expansion, low retardation and high transparency, in order to obtain a resin film excellent in flexibility, with respect to the total number of moles of the tetracarboxylic dianhydride component, The alicyclic tetracarboxylic dianhydride, for example, the tetracarboxylic dianhydride represented by the above formula (C1) is preferably at least 90 mol%, more preferably at least 95 mol%, particularly preferably all (100 mol%) is optimally a tetracarboxylic dianhydride represented by the above formula (C1).
Similarly, the above-mentioned low linear expansion coefficient, low retardation and high transparency properties, to obtain a resin film having excellent flexibility, with respect to the total number of moles of the diamine component, a fluorine-containing aromatic diamine, For example, the diamine represented by the formula (A1) is preferably at least 90 mol%, more preferably at least 95 mol%. Further, all (100 mol%) of the diamine component may be a diamine represented by the above formula (A1).

As an example of a preferred embodiment, the polyimide used in the present invention contains a monomer unit represented by the following formula (1).

As the monomer unit represented by the above formula (1), those represented by the formula (1-1) or (1-2) are preferable, and those represented by the formula (1-1) are more preferable.

According to a preferred embodiment of the present invention, the polyimide used in the present invention further contains a monomer unit represented by the formula (2) in addition to the monomer unit represented by the formula (1).

As the monomer unit represented by the above formula (2), those represented by the formula (2-1) or (2-2) are preferable, and those represented by the formula (2-1) are more preferable.

  When the polyimide used in the present invention contains the monomer unit represented by the formula (1) and the monomer unit represented by the formula (2), the polyimide unit is represented by the formula (1) in a molar ratio in the polyimide chain. Monomer unit: monomer unit represented by the formula (2) = 10: 1 to 1:10, more preferably 10: 1 to 3: 1.

  The polyimide of the present invention comprises an alicyclic tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride represented by the formula (C1) and a diamine component containing the diamine represented by the formula (A1). And other monomer units other than the monomer units represented by the above formulas (1) and (2). The content ratio of the other monomer units is arbitrarily determined as long as the properties of the resin thin film formed from the resin thin film forming composition of the present invention are not impaired. The ratio is derived from the alicyclic tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride represented by the formula (C1) and the diamine component containing the diamine represented by the formula (A1). The monomer unit represented by the formula (1), for example, based on the number of moles of the monomer unit represented by the formula (1), or when the monomer unit represented by the formula (2) is contained, It is preferably less than 20 mol%, more preferably less than 10 mol%, even more preferably less than 5 mol%, based on the total number of moles of the unit and the monomer unit represented by the formula (2).

Such other monomer units include, for example, monomer units having another polyimide structure represented by the formula (3), but are not limited thereto.

In the formula (3), A represents a tetravalent organic group, and preferably represents a tetravalent group represented by any of the following formulas (A-1) to (A-4). In the above formula (3), B represents a divalent organic group, preferably a divalent group represented by any one of formulas (B-1) to (B-11). In each formula, * represents a bond. In addition, in Formula (3), when A represents a tetravalent group represented by any of the following formulas (A-1) to (A-4), B is represented by the above formulas (Y-1) to (Y-1). Y-34). Alternatively, in the formula (3), when B represents a divalent group represented by any of the following formulas (B-1) to (B-11), A is the above-described formula (X-1) to (X It may be a tetravalent group represented by any of -12).
When the polyimide of the present invention contains a monomer unit represented by the formula (3), A and B may contain only a monomer unit composed of only one of the groups exemplified by the following formulas, for example. At least one of A and B may include two or more monomer units selected from two or more groups exemplified below.

  In the polyimide used in the present invention, each monomer unit is bonded in an arbitrary order.

As a preferred example, a polyimide having a monomer unit represented by the above formula (1) may be a bicyclo [3,3,0] octane-2,4,6,8-tetracarboxylic acid as a tetracarboxylic dianhydride component It is obtained by polymerizing a dianhydride and a diamine represented by the following formula (4) as a diamine component in an organic solvent, and imidizing the resulting polyamic acid.
When the polyimide used in the present invention has a monomer unit represented by the above formula (2) in addition to the monomer unit represented by the above formula (1), it is represented by the formulas (1) and (2). Polyimide containing each monomer unit is a tetracarboxylic dianhydride component, in addition to the above tetracarboxylic dianhydride, 1,2,3,4-cyclobutanetetracarboxylic dianhydride, and a diamine component represented by the following formula It is obtained by polymerizing a diamine represented by (4) in an organic solvent and imidizing the resulting polyamic acid.

Examples of the diamine represented by the above formula (4) include 2,2′-bis (trifluoromethyl) benzidine, 3,3′-bis (trifluoromethyl) benzidine, and 2,3′-bis (trifluoromethyl) Benzidine.
Among them, as the diamine component, from the viewpoint of lowering the linear expansion coefficient of the resin thin film of the present invention and increasing the transparency of the resin thin film, the diamine component is represented by the following formula (4-1): It is preferable to use 2'-bis (trifluoromethyl) benzidine or 3,3'-bis (trifluoromethyl) benzidine represented by the following formula (4-2), and in particular, 2,2'-bis (trifluoro It is preferred to use (methyl) benzidine.

Further, the polyimide used in the present invention contains an alicyclic tetracarboxylic dianhydride component containing the tetracarboxylic dianhydride represented by the above formula (C1) and a diamine represented by the formula (A1). In addition to a monomer unit derived from a diamine component, for example, a monomer unit represented by the above formula (1) and a monomer unit represented by the formula (2), another monomer unit represented by the above formula (3) When it has, the polyimide containing each monomer unit represented by Formula (1), Formula (2) and Formula (3) is a tetracarboxylic dianhydride component of the above-mentioned two kinds of tetracarboxylic dianhydrides. In addition, a tetracarboxylic dianhydride represented by the following formula (5) and a diamine represented by the following formula (6) in addition to the diamine represented by the above formula (4) as a diamine component in an organic solvent: Polymer obtained by Obtained by imidizing a click acid.

  A in the above formula (5) and B in the formula (6) have the same meanings as A and B in the above formula (3), respectively.

Specifically, examples of the tetracarboxylic dianhydride represented by the formula (5) include pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic dianhydride, 3,3', 4,4'-diphenylethertetracarboxylic dianhydride, 3,3 ', 4,4'-diphenylsulfonetetracarboxylic dianhydride Compound, 4,4 ′-(hexafluoroisopropylidene) diphthalic dianhydride, 11,11-bis (trifluoromethyl) -1H-difluoro [3,4-b: 3 ′, 4′-i] xanthen- 1,3,7,9- (11H-tetraone), 6,6′-bis (trifluoromethyl)-[5,5′-biisobenzofuran] -1,1 ′, 3,3′-tetraone, , 6,10,12-tetrafluorodifuro [3,4 b: 3 ', 4'-i] dibenzo [b, e] [1,4] dioxin-1,3,7,9-tetraone, 4,8-bis (trifluoromethoxy) benzo [1,2-c : 4,5-c '] difuran-1,3,5,7-tetraone, N, N'-[2,2'-bis (trifluoromethyl) biphenyl-4,4'-diyl] bis (1, Aromatic tetracarboxylic acids such as 3-dioxo-1,3-dihydroisobenzofuran-5-carbamide); 1,2-dimethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride; 3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic dianhydride, 1,2,3,4-cyclopentanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetra Carboxylic dianhydride, 3,4-dicarboxy-1, Alicyclic tetracarboxylic dianhydrides such as 1,3,4-tetrahydro-1-naphthalenesuccinic dianhydride; aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic dianhydride Anhydrides, but are not limited thereto.
Among these, tetracarboxylic dianhydride in which A in the formula (5) is a tetravalent group represented by any of the formulas (A-1) to (A-4) is preferable, that is, 11 , 11-Bis (trifluoromethyl) -1H-difluoro [3,4-b: 3 ′, 4′-i] xanthen-1,3,7,9- (11H-tetraone), 6,6′-bis (Trifluoromethyl)-[5,5'-biisobenzofuran] -1,1 ', 3,3'-tetraone, 4,6,10,12-tetrafluorodifuro [3,4-b: 3' , 4'-i] Dibenzo [b, e] [1,4] dioxin-1,3,7,9-tetraone, 4,8-bis (trifluoromethoxy) benzo [1,2-c: 4,5 -C '] difuran-1,3,5,7-tetraone can be mentioned as a preferred compound.

Examples of the diamine represented by the formula (6) include 2- (trifluoromethyl) benzene-1,4-diamine, 5- (trifluoromethyl) benzene-1,3-diamine, and 5- (trifluoromethyl). ) Benzene-1,2-diamine, 2,5-bis (trifluoromethyl) -benzene-1,4-diamine, 2,3-bis (trifluoromethyl) -benzene-1,4-diamine, 2,6 -Bis (trifluoromethyl) -benzene-1,4-diamine, 3,5-bis (trifluoromethyl) -benzene-1,2-diamine, tetrakis (trifluoromethyl) -1,4-phenylenediamine, 2 -(Trifluoromethyl) -1,3-phenylenediamine, 4- (trifluoromethyl) -1,3-phenylenediamine, 2-methoxy-1,4-phenylene Diamine, 2,5-dimethoxy-1,4-phenylenediamine, 2-hydroxy-1,4-phenylenediamine, 2,5-dihydroxy-1,4-phenylenediamine, 2-fluorobenzene-1,4-diamine, 2,5-difluorobenzene-1,4-diamine, 2-chlorobenzene-1,4-diamine, 2,5-dichlorobenzene-1,4-diamine, 2,3,5,6-tetrafluorobenzene-1, 4-diamine, 4,4 '-(perfluoropropane-2,2-diyl) dianiline, 4,4'-oxybis [3- (trifluoromethyl) aniline], 1,4-bis (4-aminophenoxy) Benzene, 1,3'-bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, benzidine, 2-methylben Gin, 3-methylbenzidine, 2- (trifluoromethyl) benzidine, 3- (trifluoromethyl) benzidine, 2,2′-dimethylbenzidine (m-tolidine), 3,3′-dimethylbenzidine (o-tolidine) 2,3′-dimethylbenzidine, 2,2′-dimethoxybenzidine, 3,3′-dimethoxybenzidine, 2,3′-dimethoxybenzidine, 2,2′-dihydroxybenzidine, 3,3′-dihydroxybenzidine, , 3'-Dihydroxybenzidine, 2,2'-difluorobenzidine, 3,3'-difluorobenzidine, 2,3'-difluorobenzidine, 2,2'-dichlorobenzidine, 3,3'-dichlorobenzidine, 2,3 '-Dichlorobenzidine, 4,4'-diaminobenzanilide, 4-aminophenyl-4'-aminobenzoate Octafluorobenzidine, 2,2 ′, 5,5′-tetramethylbenzidine, 3,3 ′, 5,5′-tetramethylbenzidine, 2,2 ′, 5,5′-tetrakis (trifluoromethyl) benzidine, 3,3 ′, 5,5′-tetrakis (trifluoromethyl) benzidine, 2,2 ′, 5,5′-tetrachlorobenzidine, 4,4′-bis (4-aminophenoxy) biphenyl, 4,4 ′ -Bis (3-aminophenoxy) biphenyl, 4,4 '-{[3,3 "-bis (trifluoromethyl)-(1,1': 3 ', 1" -terphenyl) -4,4 "- Diyl] -bis (oxy) dianiline, 4,4 ′-{[(perfluoropropane-2,2-diyl) bis (4,1-phenylene)] bis (oxy)} dianiline, 1- (4-amino Phenyl) -2,3-dihydro-1, Aromatic diamines such as 4,3-trimethyl-1H-indene-5 (or 6) amine; 4,4′-methylenebis (cyclohexylamine), 4,4′-methylenebis (3-methylcyclohexylamine), isophoronediamine, trans -1,4-cyclohexanediamine, cis-1,4-cyclohexanediamine, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6 -Bis (aminomethyl) bicyclo [2.2.1] heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 2,2-bis ( 4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propane Diamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine, etc. But is not limited thereto.
Among these, an aromatic diamine in which B in the formula (6) is a divalent group represented by any of the formulas (B-1) to (B-11) is preferable, that is, 2,2 ′. -Bis (trifluoromethoxy)-(1,1'-biphenyl) -4,4'-diamine [alias: 2,2'-dimethoxybenzidine], 4,4 '-(perfluoropropane-2,2- Diyl) dianiline, 2,5-bis (trifluoromethyl) benzene-1,4-diamine, 2- (trifluoromethyl) benzene-1,4-diamine, 2-fluorobenzene-1,4-diamine, 4, 4′-oxybis [3- (trifluoromethyl) aniline], 2,2 ′, 3,3 ′, 5,5 ′, 6,6′-octafluoro [1,1′-biphenyl] -4,4 ′ -Diamine [also called octafluorobenzidine], 2,3,5 -Tetrafluorobenzene-1,4-diamine, 4,4 '-{[3,3 "-bis (trifluoromethyl)-(1,1': 3 ', 1" -terphenyl) -4,4 " -Diyl] -bis (oxy)} dianiline, 4,4 ′-{[(perfluoropropane-2,2-diyl) bis (4,1-phenylene)] bis (oxy)} dianiline, 1- (4- Aminophenyl) -2,3-dihydro-1,3,3-trimethyl-1H-indene-5 (or 6) amine can be mentioned as a preferred diamine.

<Synthesis of polyamic acid>
The polyimide used in the present invention is, as described above, a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride represented by the above formula (C1), and a polyimide represented by the above formula (A1). Of a polyamic acid obtained by reacting a diamine component containing a fluorinated aromatic diamine.
Specifically, for example, as a preferred example, bicyclo [3,3,0] octane-2,4,6,8-tetracarboxylic dianhydride and optionally 1,2,3,4-cyclobutanetetracarboxylic acid An acid dianhydride, and further, if desired, a tetracarboxylic dianhydride component comprising a tetracarboxylic dihydrate represented by the above formula (5), a diamine represented by the above formula (4), and optionally a diamine represented by the above formula ( It is obtained by polymerizing a diamine component comprising the diamine component represented by 6) in an organic solvent, and imidizing the resulting polyamic acid.
The reaction from the two components to the polyamic acid is advantageous in that it can proceed relatively easily in an organic solvent and that no by-products are generated.

  The charge ratio (molar ratio) of the diamine component in the reaction between the tetracarboxylic dianhydride component and the diamine component is appropriately set in consideration of the molecular weight of the polyamic acid and further the polyimide obtained by imidization. However, the amount of the tetracarboxylic dianhydride component can be generally about 0.8 to 1.2, for example, about 0.9 to 1.1, and preferably about 0.1 to 1.1 with respect to the diamine component 1. It is about 95 to 1.02. As in the ordinary polycondensation reaction, the molecular weight of the generated polyamic acid increases as the molar ratio approaches 1.0.

The organic solvent used in the reaction between the tetracarboxylic dianhydride component and the diamine component is not particularly limited as long as it does not adversely affect the reaction and dissolves the generated polyamic acid. Specific examples will be described below.
For example, m-cresol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, 3- Methoxy-N, N-dimethylpropylamide, 3-ethoxy-N, N-dimethylpropylamide, 3-propoxy-N, N-dimethylpropylamide, 3-isopropoxy-N, N-dimethylpropylamide, 3-butoxy -N, N-dimethylpropylamide, 3-sec-butoxy-N, N-dimethylpropylamide, 3-tert-butoxy-N, N-dimethylpropylamide, γ-butyrolactone, N-methylcaprolactam, dimethylsulfoxide, tetra Methyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxy Isopropyl alcohol, methoxymethylpentanol, dipentene, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, methyl cellosolve, ethyl cellosolve, methyl cellosolve acetate, ethyl cellosolve acetate, butyl carbitol, Ethyl carbitol, ethylene glycol, ethylene glycol monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol-tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol , Diethylene Glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, dipropylene glycol monopropyl ether, dipropylene glycol monoacetate mono Propyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl acetate, butyl butyrate, butyl ether, diisobutyl ketone, Methylcyclohexene, propyl ether, dihexy Ether, dioxane, n-hexane, n-pentane, n-octane, diethyl ether, cyclohexanone, ethylene carbonate, propylene carbonate, methyl lactate, ethyl lactate, methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol monoethyl acetate Ether, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate Butyl 3-methoxypropionate, diglyme, 4-hydroxy-4-methyl-2-pentanone, but are not limited thereto. These may be used alone or in combination of two or more.
Furthermore, even if the solvent does not dissolve the polyamic acid, it may be used by mixing with the above solvent as long as the generated polyamic acid does not precipitate. In addition, since water in the organic solvent inhibits the polymerization reaction and further causes hydrolysis of the generated polyamic acid, it is preferable to use a dehydrated organic solvent as much as possible.

As a method of reacting the tetracarboxylic dianhydride component and the diamine component in an organic solvent, a dispersion or solution in which the diamine component is dispersed or dissolved in the organic solvent is stirred, and the tetracarboxylic dianhydride is added thereto. A method in which the components are added as they are or a component in which the components are dispersed or dissolved in an organic solvent, and conversely, a diamine component is added to a dispersion or solution in which a tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent. And a method of alternately adding a tetracarboxylic dianhydride component and a diamine compound component, and any of these methods may be used.
When the tetracarboxylic dianhydride component and / or the diamine component are composed of a plurality of types of compounds, they may be reacted in a premixed state, may be individually reacted sequentially, and may be individually reacted. A low molecular weight substance may be mixed and reacted to obtain a high molecular weight substance.

The temperature at the time of synthesizing the polyamic acid may be appropriately set within the range from the melting point to the boiling point of the solvent to be used. For example, an arbitrary temperature of -20 ° C to 150 ° C can be selected. C. to 100.degree. C., usually about 0 to 100.degree. C., preferably about 0 to 70.degree.
The reaction time cannot be specified unconditionally because it depends on the reaction temperature and the reactivity of the raw materials, but is usually about 1 to 100 hours.
The reaction can be carried out at any concentration, but if the concentration is too low, it is difficult to obtain a high molecular weight polymer, and if the concentration is too high, the viscosity of the reaction solution becomes too high, and uniform stirring is difficult. Therefore, the total concentration of the tetracarboxylic dianhydride component and the diamine component in the reaction solution is preferably 1 to 50% by mass, more preferably 5 to 40% by mass. Initially, the reaction is performed at a high concentration, and then an organic solvent can be added.

<Imidation of polyamic acid>
Examples of the method for imidizing the polyamic acid include thermal imidization in which a solution of the polyamic acid is directly heated and catalytic imidization in which a catalyst is added to the solution of the polyamic acid.
The temperature at which the polyamic acid is thermally imidized in the solution is from 100 ° C. to 400 ° C., preferably from 120 ° C. to 250 ° C., and it is preferable to carry out the reaction while removing water generated by the imidization reaction out of the system.

Chemical (catalytic) imidization of a polyamic acid is performed by adding a basic catalyst and an acid anhydride to a solution of a polyamic acid, and adding -20 to 250 ° C., preferably 0 to 180 ° C. in the system. It can be performed by stirring.
The amount of the basic catalyst is 0.5 to 30 mol times, preferably 1.5 to 20 mol times, of the amic acid groups of the polyamic acid, and the amount of the acid anhydride is 1 to 50 mol of the amic acid groups of the polyamic acid. Times, preferably 2 to 30 times.

Examples of the basic catalyst include pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, 1-ethylpiperidine, and the like. Among them, pyridine is preferable because it has an appropriate basicity for causing the reaction to proceed.
Examples of the acid anhydride include acetic anhydride, trimellitic anhydride, and pyromellitic anhydride. Among them, acetic anhydride is preferred because purification after the reaction is facilitated.
The imidization rate by the catalytic imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature, and the reaction time.

  In the polyimide resin used in the present invention, the dehydration ring-closing rate (imidization rate) of the amide acid group is not necessarily required to be 100%, and can be arbitrarily adjusted and used depending on the use or purpose. It is particularly preferably at least 50%.

  In the present invention, after the reaction solution is filtered, the filtrate may be used as it is, or may be diluted or concentrated, and may be mixed with silicon dioxide or the like described later to obtain a composition for forming a resin thin film. When such filtration is performed, not only the heat resistance of the obtained resin thin film, the incorporation of impurities that may cause deterioration of flexibility or linear expansion coefficient characteristics can be reduced, but also a resin thin film forming composition can be efficiently obtained. it can.

  The polyimide used in the present invention has a weight average molecular weight (Mw) in terms of polystyrene by gel permeation chromatography (GPC) in consideration of the strength of the resin thin film, workability in forming the resin thin film, uniformity of the resin thin film, and the like. ) Is preferably 5,000 to 200,000.

<Polymer collection>
When the polymer component is recovered from the reaction solution of the polyamic acid and the polyimide and used, the reaction solution may be put into a poor solvent to precipitate. Examples of the poor solvent used for precipitation include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, and water. After the polymer that has been put into the poor solvent and precipitated is collected by filtration, it can be dried at normal temperature or under reduced pressure at normal temperature or under normal pressure.
In addition, by repeating the operation of re-dissolving the precipitated and recovered polymer in an organic solvent and performing re-precipitation recovery 2 to 10 times, impurities in the polymer can be reduced. It is preferable to use three or more kinds of poor solvents such as alcohols, ketones, and hydrocarbons as the poor solvent in this case, because the purification efficiency is further improved.

  The organic solvent in which the resin component is dissolved in the reprecipitation recovery step is not particularly limited. Specific examples include N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethylsulfoxide, tetramethyl Methyl urea, pyridine, dimethyl sulfone, hexamethyl sulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, dipentene, ethyl amyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate , Propylene carbonate, diglyme, 4-hydroxy-4-methyl-2-pentanone and the like. These solvents may be used as a mixture of two or more kinds.

[Silicon dioxide]
The silicon dioxide (silica) used in the present invention is not particularly limited, but silicon dioxide in the form of particles, for example, having an average particle diameter of 100 nm or less, for example, 5 nm to 100 nm, preferably 5 nm to 55 nm, and a highly transparent thin film can be reproduced. From the viewpoint of obtaining well, the thickness is preferably 5 nm to 50 nm, more preferably 5 nm to 45 nm, still more preferably 5 nm to 35 nm, and still more preferably 5 nm to 30 nm.
In the present invention, the average particle diameter of silicon dioxide particles is an average particle diameter value calculated from a specific surface area value measured by a nitrogen adsorption method using silicon dioxide particles.

In particular, in the present invention, colloidal silica having the above-mentioned average particle diameter can be suitably used, and as the colloidal silica, silica sol can be used. As the silica sol, an aqueous silica sol produced by a known method using a sodium silicate aqueous solution as a raw material and an organosilica sol obtained by substituting water as a dispersion medium of the aqueous silica sol with an organic solvent can be used.
Further, an alkoxysilane such as methyl silicate or ethyl silicate is hydrolyzed and condensed in an organic solvent such as an alcohol in the presence of a catalyst (eg, an ammonia, an organic amine compound, or an alkali catalyst such as sodium hydroxide). Silica sol to be used or an organosilica sol obtained by substituting the silica sol with another organic solvent can also be used.
Among these, the present invention preferably uses an organosilica sol in which the dispersion medium is an organic solvent.

Examples of the organic solvent in the above-mentioned organosilica sol include lower alcohols such as methyl alcohol, ethyl alcohol and isopropanol; linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide; N-methyl-2- Cyclic amides such as pyrrolidone; ethers such as γ-butyrolactone; glycols such as ethyl cellosolve and ethylene glycol; acetonitrile; This substitution can be performed by a usual method such as a distillation method and an ultrafiltration method.
The viscosity of the above organosilica sol at 20 ° C. is about 0.6 mPa · s to 100 mPa · s.

Examples of commercially available organosilica sols include, for example, MA-ST-S (methanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.) and MT-ST (methanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.) ), Trade name MA-ST-UP (methanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MA-ST-M (methanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MA-ST- L (methanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.), trade name IPA-ST-S (isopropanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.), trade name IPA-ST (isopropanol-dispersed silica sol, Nissan Chemical Industries, Ltd. Co., Ltd.), trade name IPA-ST-UP (isopropanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.), trade name IPA-ST- (Isopropanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.), trade name IPA-ST-ZL (isopropanol-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.), trade name NPC-ST-30 (n-propyl cellosolve dispersed silica sol, Nissan Chemical Industry Co., Ltd.), PGM-ST (1-methoxy-2-propanol-dispersed silica sol, Nissan Chemical Industry Co., Ltd.), DMAC-ST (dimethylacetamide-dispersed silica sol, Nissan Chemical Co., Ltd.) )), Trade name XBA-ST (xylene / n-butanol mixed solvent dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name EAC-ST (ethyl acetate dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), product PMA-ST (Propylene glycol monomethyl ether acetate dispersed silica sol, Nissan Chemical Industries, Ltd.) ), Trade name MEK-ST (methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MEK-ST-UP (methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MEK-ST-L ( Examples thereof include, but are not limited to, methyl ethyl ketone-dispersed silica sol (manufactured by Nissan Chemical Industries, Ltd.) and brand name MIBK-ST (methyl isobutyl ketone-dispersed silica sol, manufactured by Nissan Chemical Industries, Ltd.).
In the present invention, silicon dioxide, for example, the above-mentioned silicon dioxide used as an organosilica sol may be used as a mixture of two or more kinds.

[Organic solvent]
The composition for forming a resin thin film of the present invention contains an organic solvent in addition to the polyimide and silicon dioxide. The organic solvent is not particularly limited, and examples thereof include those similar to the specific examples of the reaction solvent used in preparing the polyamic acid and the polyimide. More specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1,3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, γ- Butyrolactone and the like. In addition, an organic solvent may be used individually by 1 type, and may be used in combination of 2 or more type.
Among these, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone are preferable in consideration of obtaining a resin film having high flatness with good reproducibility.

[Composition for forming resin thin film]
The present invention is a composition for forming a resin thin film, comprising the polyimide, silicon dioxide, and an organic solvent. Here, the composition for forming a resin thin film of the present invention is uniform and does not show phase separation.
In the composition for forming a resin thin film of the present invention, the mixing ratio of the polyimide and the silicon dioxide is preferably polyimide: silicon dioxide = 10: 1 to 1:10, more preferably 8: 2 by mass ratio. ２2: 8, for example, 7: 3 to 3: 7.
The amount of the solid content in the composition for forming a resin thin film of the present invention is usually about 0.5 to 30% by mass, and preferably about 5 to 25% by mass. When the solid concentration is less than 0.5% by mass, the film-forming efficiency in producing a resin thin film is low, and the viscosity of the composition for forming a resin thin film is low, so that a coating film having a uniform surface can be obtained. Hateful. When the solid content exceeds 30% by mass, the viscosity of the composition for forming a resin thin film becomes too high, which may also deteriorate the film formation efficiency and lack the uniformity of the surface of the coating film. Here, the solid content means the total mass of components other than the organic solvent, and even a liquid monomer or the like is included in the weight as a solid content.
The viscosity of the resin thin film forming composition is appropriately set in consideration of the thickness and the like of the resin thin film to be produced. In particular, when the purpose is to obtain a resin thin film having a thickness of about 5 to 50 μm with good reproducibility. Usually, it is about 500 to 50,000 mPa · s at 25 ° C., and preferably about 1,000 to 20,000 mPa · s.

In order to impart processing characteristics and various functionalities, various other organic or inorganic low molecular or high molecular compounds may be added to the resin thin film forming composition of the present invention. For example, a catalyst, an antifoaming agent, a leveling agent, a surfactant, a dye, a plasticizer, fine particles, a coupling agent, a sensitizer, and the like can be used. For example, a catalyst can be added for the purpose of reducing the retardation and the linear expansion coefficient of the resin thin film. In addition, a composition for forming a resin thin film containing a catalyst in addition to the polyimide, silicon dioxide, and the organic solvent can also be an object of the present invention.
The composition for forming a resin thin film of the present invention can be obtained by dissolving the polyimide and silicon dioxide obtained by the above-described method in the above-mentioned organic solvent, and adding silicon dioxide to the reaction solution after preparing the polyimide. If desired, the organic solvent may be further added.

[Resin thin film]
The organic solvent is removed by applying the composition for forming a resin thin film of the present invention described above to a substrate, followed by drying and heating to remove heat, high heat resistance, high transparency, appropriate flexibility, and appropriate wire. A resin thin film having an expansion coefficient and having a small retardation can be obtained.
The resin thin film, that is, the resin thin film containing the polyimide and the inorganic silica compound is also an object of the present invention. Further, in addition to the polyimide and silicon dioxide, a resin thin film containing a catalyst is also an object of the present invention.

Examples of the base material used for producing the resin thin film include plastics (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetylcellulose, ABS, AS, norbornene-based resin, etc.), metal, stainless steel (SUS ), Wood, paper, glass, silicon wafer, slate and the like.
In particular, when applied as a substrate material for an electronic device, from the viewpoint that existing equipment can be used, it is preferable that the substrate to be applied is glass or a silicon wafer, and that the obtained resin thin film has good peeling. Glass is more preferable because of its properties. In addition, the linear expansion coefficient of the applied substrate is preferably 30 ppm / ° C. or less, more preferably 20 ppm / ° C. or less, from the viewpoint of the warpage of the substrate after coating.

  The method of applying the composition for forming a resin thin film to a substrate is not particularly limited, and includes, for example, a cast coating method, a spin coating method, a blade coating method, a dip coating method, a roll coating method, a bar coating method, Examples include a die coating method, an ink jet method, and a printing method (e.g., letterpress, intaglio, lithographic, screen printing), which can be used as appropriate according to the purpose.

The heating temperature is preferably 300 ° C. or lower. When the temperature exceeds 300 ° C., the obtained resin thin film becomes brittle, and it may not be possible to obtain a resin thin film particularly suitable for display substrate use.
Further, considering the heat resistance and the coefficient of linear expansion coefficient of the obtained resin thin film, after heating the applied composition for forming a resin thin film at 40 ° C. to 100 ° C. for 5 minutes to 2 hours, the heating temperature is increased stepwise as it is. It is desirable to finally heat at more than 175 ° C to 280 ° C for 30 minutes to 2 hours. As described above, by heating at two or more stages of the stage of drying the solvent and the stage of promoting the molecular orientation, low thermal expansion characteristics can be exhibited.
In particular, the applied composition for forming a resin thin film is heated at 40 ° C to 100 ° C for 5 minutes to 2 hours, and then heated at more than 100 ° C to 175 ° C for 5 minutes to 2 hours, and then heated at 175 ° C to 280 ° C for 5 minutes. It is preferred to heat for minutes to 2 hours.
Instruments used for heating include, for example, a hot plate and an oven. The heating atmosphere may be under air or under an inert gas such as nitrogen, may be under normal pressure or under reduced pressure, and may apply a different pressure at each stage of heating. You may.

The thickness of the resin thin film is usually about 1 to 60 m, preferably about 5 to 50 μm, particularly when used as a substrate for a flexible display, and the thickness of the coating film before heating is adjusted to obtain a resin having a desired thickness. Form a thin film.
There is no particular limitation on the method of peeling the resin thin film formed in this manner from the substrate, and the resin thin film is cooled together with the substrate, and a method of peeling the thin film and applying tension through a roll is provided. And the like.

The thus obtained resin thin film according to one preferred embodiment of the present invention can realize high transparency such that the light transmittance at a wavelength of 400 nm is 75% or more.
Further, the resin thin film may have a coefficient of linear expansion at 50 ° C. to 200 ° C. of 60 ppm / ° C. or less, particularly as low as 10 ppm / ° C. to 35 ppm / ° C., and for example, a linear expansion coefficient at 200 ° C. to 250 ° C. The coefficient can have a low value of 80 ppm / ° C. or less, particularly 15 ppm / ° C. to 55 ppm / ° C., and is excellent in dimensional stability during heating.
In particular, the resin thin film has an in-plane retardation R ₀ represented by a product of a birefringence (difference between two orthogonal in-plane refractive indices) and a film thickness when the wavelength of incident light is 590 nm, and a thickness. The average value of the two phase differences obtained by multiplying the two birefringences (the difference between the two in-plane refractive indices and the refractive index in the thickness direction) when viewed from the cross section in the vertical direction by the film thickness, respectively. It is characterized in that the thickness direction retardation _Rth is extremely small. Resin thin film of the present invention, when the average film thickness of 15Myuemu～40myuemu, retardation _{R th} is less than 700nm in the thickness direction, for example 660nm or less, for example, 10Nm～660nm, plane retardation _{R 0} is less than 4, for example, 0.3 to 3.9, and the birefringence Δn has a very low value of less than 0.02, for example, 0.0003 to 0.019.
Thus, by forming a resin thin film using the composition for forming a resin thin film of the present invention, the retardation of the resin thin film can be reduced, and a method of reducing the retardation of such a resin thin film is also an object of the present invention. It is.

  The resin thin film of the present invention described above satisfies each condition necessary as a base film of a flexible display substrate because of having the above-mentioned characteristics, and can be particularly suitably used as a base film of a flexible display substrate.

  Hereinafter, the present invention will be described more specifically with reference to examples, but the present invention is not limited to the following examples.

The meanings of the abbreviations used in the following examples are as follows.
<Acid dianhydride>
BODA: bicyclo [3,3,0] octane-2,4,6,8-tetracarboxylic dianhydride CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride TCA: 2,3,5 -Tricarboxycyclopentylacetic acid-1,4: 2,3-dianhydride BODAxx: bicyclo [2,2,2] octane-2,3,5,6-tetracarboxylic dianhydride <diamine>
TFMB: 2,2′-bis (trifluoromethyl) benzidine TMDA: 1- (4-aminophenyl) -2,3-dihydro-1,3,3-trimethyl-1H-indene-5 (or 6) amine < Organic solvent>
DMAc: N, N-dimethylacetamide NMP: N-methyl-2-pyrrolidone DMF: N, N-dimethylformamide IPA: isopropanol GBL: γ-butyrolactone

<Silica sol>
IPA-ST: isopropanol-dispersed silica sol (silica average particle diameter: 10 to 15 nm, silica solid content: 30% by mass) Nissan Chemical Industries, Ltd. DMAC-ST: N, N-dimethylacetamide-dispersed silica sol (silica average particle diameter) : 10 to 15 nm, silica solids concentration: 20% by mass), Nissan Chemical Industries, Ltd. GBL-ZL: γ-butyrolactone dispersed silica sol (silica solids concentration: 25% by mass)
GBL-L: γ-butyrolactone dispersed silica sol (silica solid content concentration: 25% by mass)
GBL-M: γ-butyrolactone dispersed silica sol (silica solid concentration: 30% by mass)
GBL-ST: γ-butyrolactone-dispersed silica sol (silica solid concentration: 30% by mass)
GBL-S: γ-butyrolactone dispersed silica sol (silica solid concentration: 25% by mass)
GBL-UP: γ-butyrolactone dispersed silica sol (chain type, silica solid content concentration: 20% by mass)
The above-mentioned γ-butyrolactone-dispersed silica sol (GBL-ZL, GBL-L, GBL-M, GBL-ST, GBL-S and GBL-UP) is obtained by the method described below by isopropanol-dispersed silica sol manufactured by Nissan Chemical Industries, Ltd. (IPA-ST-ZL, IPA-ST-L, IPA-ST) and methanol-dispersed silica sol (MA-ST-M, MA-ST-S, MA-ST-UP) manufactured by Nissan Chemical Industries, Ltd. Is obtained by solvent replacement of isopropanol or methanol with γ-butyrolactone.
The average particle diameter of silica in the above IPA-ST and DMAC-ST is a catalog value, and the average particle diameter calculated from the specific surface area measured by the nitrogen adsorption method in the silica sol used this time is as follows. Specifically, the specific surface area of the dried silica sol powder was measured using a specific surface area measuring device Monosorb MS-16 manufactured by Yuasa Ionics, and D (D) was determined using the measured specific surface area S (m ² / g). nm) = 2720 / S, and the average primary particle diameter was calculated.
IPA-ST average particle size: 12 nm
DMAC-ST: 12 nm
GBL-ZL: 80 nm
GBL-L: 45 nm
GBL-M: 22 nm
GBL-ST: 12 nm
GBL-S: 9 nm
GBL-UP: 12 nm

In the examples, the apparatus and conditions used for sample preparation and physical property analysis and evaluation are as follows.
1) Measurement of number average molecular weight and weight average molecular weight The number average molecular weight (hereinafter abbreviated as Mn) and the weight average molecular weight (hereinafter abbreviated as Mw) of the polymer were measured using an apparatus: Showdex GPC-101, manufactured by Showa Denko KK. Column: KD803 and KD805, column temperature: 50 ° C., elution solvent: DMF, flow rate: 1.5 ml / min, calibration curve: standard polystyrene.
2) Film thickness The film thickness of the obtained resin thin film was measured with a thickness gauge manufactured by TECLOCK Co., Ltd.
3) Coefficient of linear expansion (CTE)
Using a TMA Q400 manufactured by TA Instruments, the resin thin film is cut into a size of 5 mm in width and 16 mm in length, first heated at 10 ° C./min, heated to 50 to 350 ° C. (first heating), and then heated at 10 ° C./min. After the temperature is lowered at 50 ° C./min and cooled to 50 ° C., the linear expansion of the second heating at 50 ° C. to 200 ° C. when the temperature is raised at 10 ° C./min and heated to 50 to 420 ° C. (second heating) The coefficient (CTE [ppm / ° C.]) and the coefficient of linear expansion (CTE [ppm / ° C.]) from 200 ° C. to 250 ° C. were determined. Note that a load of 0.05 N was applied through the first heating, the cooling, and the second heating.
4) 5% weight loss temperature (Td _5% )
The 5% weight loss temperature (Td _5% [° C.]) is measured by using a TGA Q500 manufactured by TA Instruments Inc. by heating a resin thin film of about 5 to 10 mg to 50 to 800 ° C. at 10 ° C./min in nitrogen. I asked by that.
5) Light transmittance (transparency) (T _{400 nm} , T _{550 nm} ) and CIE b value (CIE b ^* )
The light transmittances at wavelengths of 400 nm and 550 nm (T _{400 nm} , T _{550 nm} [%]) and the CIE b value (CIE b ^* ) were determined at room temperature using a SA4000 spectrometer manufactured by Nippon Denshoku Industries Co., Ltd. The measurement was performed as air.
6) Retardation ( _Rth , _R0 )
Thickness direction retardation (R _th ) and in-plane retardation (R ₀ ) were measured at room temperature using KOBURA 2100ADH manufactured by Oji Scientific Instruments.
The thickness direction retardation ( _Rth ) and the in-plane retardation ( _R0 ) are calculated by the following equations.
R ₀ = (Nx−Ny) × d = ΔNxy × d
R _th = [(Nx + Ny) / 2−Nz] × d = [(ΔNxx × d) + (ΔNyz × d) / 2
Nx, Ny: two in-plane orthogonal refractive indices (Nx> Ny, Nx is also called a slow axis, and Ny is also called a fast axis)
Nz: refractive index in the thickness (perpendicular) direction to the plane d: film thickness ΔNxy: difference between two in-plane refractive indexes (Nx-Ny) (birefringence)
ΔNxz: difference between in-plane refractive index Nx and thickness direction refractive index Nz (birefringence)
ΔNyz: difference between in-plane refractive index Ny and thickness direction refractive index Nz (birefringence)
7) Birefringence (Δn)
Using the value of the thickness direction retardation (R _th ) obtained in the above <6) Retardation>, the value was calculated by the following equation.
ΔN = [R _th / d (film thickness)] / 1000

[1] Preparation Example of Silica Sol (Preparation Example 1: Preparation of GBL-M)
A 1000 mL round bottom flask was charged with 350 g of methanol-dispersed silica sol (manufactured by Nissan Chemical Industries, Ltd.): MA-ST-M (silica solids concentration: 40.4% by mass) and 329.93 g of γ-butyl lactone. Then, the flask was connected to a vacuum evaporator to depressurize the inside of the flask, and immersed in a warm water bath at about 35 ° C. for 20 to 50 minutes, whereby the silica sol (GBL-M) in which the solvent was replaced with γ-butyl lactone from methanol was used. 471 g was obtained (silica solid content concentration: 30% by mass).
(Preparation Example 2: Preparation of GBL-ZL)
In a 1000 mL round-bottom flask, 350 g of isopropanol-dispersed silica sol manufactured by Nissan Chemical Industries, Ltd .: IPA-ST-ZL (silica solid content concentration: 30% by mass) and 315 g of γ-butyl lactone were put. Then, the flask is connected to a vacuum evaporator equipped with a chemical-resistant vacuum pump to reduce the pressure inside the flask, and immersed in a warm water bath at about 35 ° C. for 30 to 60 minutes, whereby the solvent isopropanol is replaced with γ-butyl lactone. About 420 g of silica sol (GBL-ZL) was obtained (solid concentration of silica: 25% by mass).
(Preparation Example 3: Preparation of GBL-L)
In a 1000 mL round-bottom flask, 350 g of isopropanol-dispersed silica sol manufactured by Nissan Chemical Industries, Ltd .: IPA-ST-L (silica solid content concentration: 30% by mass) and 315 g of γ-butyl lactone were put. Then, the flask is connected to a vacuum evaporator equipped with a chemical resistant vacuum pump to reduce the pressure inside the flask, and immersed in a warm water bath at about 35 ° C. for 30 to 60 minutes, whereby the solvent isopropanol is replaced with γ-butyl lactone. About 420 g of silica sol (GBL-L) was obtained (silica solid content concentration: 25% by mass).
(Preparation Example 4: Preparation of GBL-ST)
A 1000 mL round-bottom flask was charged with 350 g of isopropanol-dispersed silica sol manufactured by Nissan Chemical Industries, Ltd .: IPA-ST (silica solid content concentration: 30% by mass) and 245 g of γ-butyl lactone. Then, the flask is connected to a vacuum evaporator equipped with a chemical-resistant vacuum pump to reduce the pressure inside the flask, and immersed in a warm water bath at about 35 ° C. for 30 to 60 minutes, whereby the solvent isopropanol is replaced with γ-butyl lactone. About 350 g of silica sol (GBL-ST) was obtained (silica solid concentration: 30% by mass).
(Preparation Example 5: Preparation of GBL-S)
A 1000 mL round bottom flask was charged with 350 g of methanol-dispersed silica sol (manufactured by Nissan Chemical Industries, Ltd.): MA-ST-S (silica solid concentration: 25% by mass) and 262.5 g of γ-butyl lactone. Then, the flask was connected to a vacuum evaporator equipped with a chemical-resistant vacuum pump to reduce the pressure inside the flask, and immersed in a warm water bath at about 35 ° C for 20 to 50 minutes, whereby the solvent was replaced with γ-butyl lactone from methanol. About 350 g of the obtained silica sol (GBL-S) was obtained (silica solid content concentration: 25% by mass).
(Preparation Example 6: Preparation of GBL-UP)
A 1000 mL round bottom flask was charged with 350 g of methanol-dispersed silica sol (manufactured by Nissan Chemical Industries, Ltd.): MA-ST-UP (silica solid content concentration: 20% by mass) and 280 g of γ-butyl lactone. Then, the flask was connected to a vacuum evaporator equipped with a chemical-resistant vacuum pump to reduce the pressure inside the flask, and immersed in a warm water bath at about 35 ° C for 20 to 50 minutes, whereby the solvent was replaced with γ-butyl lactone from methanol. About 350 g of the obtained silica sol (GBL-UP) was obtained (silica solid content concentration: 20% by mass).

[2] Synthesis example [Synthesis example 1]
In a 2,000 mL flask equipped with a mechanical stirrer, 58 g (0.1811 mol) of TFMB and 188.23 g of DMAc were sequentially charged, and stirring was started. After adding 36.25 g (0.1448 mol) of BODA and replacing with nitrogen, the mixture was stirred at 70 ° C. for 3 hours, then the reaction mixture was cooled to 50 ° C., and 7.103 g (0.0362 mol) of CBDA was added thereto. And further stirred for 2 hours. Thereafter, the reaction mixture was cooled to room temperature and further stirred overnight. Then, DMAc was added to the reaction mixture, and the reaction mixture was diluted so that the concentration of the solid content (the concentration of components other than the organic solvent) was 5% by mass.
To the diluted reaction mixture, 73.96 g (0.7244 mol) of acetic anhydride and 42.97 g (0.5433 mol) of pyridine were added, and the mixture was stirred at 90 to 100 ° C for 3 hours.
After completion of the stirring, the reaction mixture was cooled to room temperature, the cooled mixture was added to 7.094 kg of methanol, and the resulting slurry was stirred for 30 minutes. Then, the residue was collected by filtration. Thereafter, for purification, the obtained residue was added again to 7.094 kg of methanol to obtain a slurry, which was then stirred and filtered in the same manner. Further, for purification, the filtrate was added to methanol, and the mixture was stirred and filtered again.
Finally, the obtained residue was dried under reduced pressure at 100 ° C. for 8 hours to obtain 76 g of the desired polyimide A1 (yield: 76%, Mw: 59,302, Mn: 25,923).

[Synthesis Example 2]
115 g (0.3591 mol) of TFMB was charged into a 2,000 mL three-necked flask having a nitrogen inlet / outlet and a mechanical stirrer. Immediately thereafter, 468.9 g of γ-butyrolactone (GBL) was added, and stirring was started. After the diamine (TFMB) was completely dissolved in the solvent, 71.88 g (0.2872 mol) of BODA was added, and the mixture was stirred at 70 ° C. for 3 hours under a nitrogen atmosphere. Next, the reaction mixture was cooled to 50 ° C., and 14.08 g (0.071 mol) of CBDA was added thereto, followed by further stirring for 2 hours. Thereafter, the reaction mixture was cooled to room temperature to maintain the temperature, and further stirred overnight under a nitrogen atmosphere. Then, GBL was added to the reaction mixture, and the reaction mixture was diluted so that the concentration of the solid content (the concentration of components other than the organic solvent) was 5% by mass.
To the diluted reaction mixture, 146.65 g (1.436 mol) of acetic anhydride and 85.21 g (1.077 mol) of pyridine were added, and the mixture was stirred at 90 to 100 ° C for 3 hours.
After completion of the stirring, the reaction mixture was cooled to room temperature, the cooled mixture was added to 2.5 kg of methanol, and the resulting slurry was stirred for 30 minutes. Then, the residue was collected by filtration. Thereafter, for purification, the obtained residue was added again to 2.5 kg of methanol to obtain a slurry, which was then stirred and filtered in the same manner. Further, for purification, addition of the filtrate to 2.5 kg of methanol, stirring and filtration were performed again.
Finally, the obtained residue was dried in a vacuum oven at 120 ° C. for 8 hours to obtain 153 g of the target polyimide A2 (yield: 76.5%, Mn: 44,460, Mw: 96,641). ).
The polyimide A2 was dissolved in GBL, and the obtained solution was slowly filtered under pressure using a 5 μm filter to prepare a solution having a solid content of 12% by mass (polyimide A2 solution).

[Synthesis Example 3]
16.9 g (0.052 mol) of TFMB and 1.598 g (0.006 mol) of TMDA were charged into a 250 mL three-necked flask having a nitrogen inlet / outlet and a mechanical stirrer. Immediately thereafter, 124.46 g of γ-butyrolactone (GBL) was added, and stirring was started. After the diamine (TFMB and TMDA) was completely dissolved in the solvent, 6.725 g (0.03 mol) of TCA was added, and the mixture was stirred at 100 ° C. for 5 hours under a nitrogen atmosphere. Next, the reaction mixture was cooled to 50 ° C., and 5.883 g (0.03 mol) of CBDA was added thereto, followed by further stirring for 3 hours. Thereafter, the reaction mixture was cooled to room temperature to maintain the temperature, and further stirred overnight under a nitrogen atmosphere. Then, GBL was added to the reaction mixture, and the reaction mixture was diluted so that the concentration of the solid content (the concentration of components other than the organic solvent) was 4% by mass.
24.5 g (0.24 mol) of acetic anhydride and 14.23 g (0.18 mol) of pyridine were added to the diluted reaction mixture, and the mixture was stirred at 60 to 70 ° C. for 6 hours.
After completion of the stirring, the reaction mixture was cooled to room temperature, the cooled mixture was added to 0.7 kg of methanol, and the resulting slurry was stirred for 30 minutes. Then, the residue was collected by filtration. Then, for purification, the obtained filtrate was added again to 0.7 kg of methanol to obtain a slurry, and the mixture was stirred and filtered in the same manner. Further, for purification, addition of the filtrate to 0.7 kg of methanol, stirring and filtration were performed again.
Finally, the obtained residue was dried in a vacuum oven at 120 ° C. for 8 hours to obtain 24.26 g of the target polyimide B (yield: 78%, Mn: 65,425, Mw: 138,024). ).
The polyimide B was dissolved in GBL, and the obtained solution was slowly subjected to pressure filtration using a 5 μm filter to prepare a solution having a solid content of 11.17% by mass (polyimide B solution).

[Synthesis Example 4]
25.61 g (0.08 mol) of TFMB was charged into a 100 mL three-necked flask having a nitrogen inlet / outlet and a mechanical stirrer and a condenser. Immediately thereafter, 173.86 g of γ-butyrolactone (GBL) was added, and stirring was started. After the diamine (TFMB) was completely dissolved in the solvent, 10 g (0.04 mol) of BODAxx and 7.84 g (0.04 mol) of CBDA were added, and the mixture was heated to 140 ° C. under a nitrogen atmosphere. Thereafter, 1.739 g of 1-ethylpiperidine was added to the reaction solution, and the mixture was heated and stirred at 210 ° C. for 4.5 hours under a nitrogen atmosphere.
The reaction mixture was added to 0.9 kg of methanol, and the resulting slurry was stirred for 30 minutes. Then, the residue was collected by filtration. Thereafter, for purification, the obtained residue was added again to 0.9 kg of methanol to obtain a slurry, which was then stirred and filtered in the same manner. Further, for purification, addition of the filtrate to 0.9 kg of methanol, stirring and filtration were performed again.
Finally, the obtained residue was dried in a vacuum oven at 120 ° C. for 8 hours to obtain 31.16 g of the target polyimide C (yield: 74%, Mn: 40,465, Mw: 281,382). ).
The polyimide C was dissolved in GBL, and the obtained solution was slowly filtered under pressure using a 5 μm filter to prepare a solution having a solid content of 13.5% by mass (polyimide C solution).

[3] Preparation of thin film composition for substrate (1)
[Example 1]
At room temperature, 3 g of polyimide A1 was dissolved in 22 g of DMAc to prepare a polyimide solution, and the obtained solution was slowly pressure-filtered using a 5 μm filter. Then, 6.67 g of the IPA-ST silica sol was added to the filtrate, and the mixture was stirred for 30 minutes. Then, the stirred mixture was allowed to stand overnight to obtain a resin composition.

[Examples 2 to 3]
The same as Example 1 except that 6.67 g of GBL-ST silica sol (Example 2) and 10.00 g of DMAC-ST silica sol (Example 3) were used instead of 6.67 g of IPA-ST silica sol, respectively. A resin composition was obtained by the method.

[Example 4]
A resin composition was obtained in the same manner as in Example 1, except that 22 g of NMP was used instead of 22 g of DMAc.

[Examples 5 to 6]
A resin composition was obtained in the same manner as in Example 2 except that 22 g of NMP (Example 5) and 22 g of GBL (Example 6) were used instead of 22 g of DMAc, respectively.

[Example 7]
A resin composition was obtained in the same manner as in Example 2, except that the amount of the GBL-ST silica sol used was changed to 2.5 g.

[Examples 8 to 9]
A resin composition was obtained in the same manner as in Example 7, except that 22 g of NMP (Example 8) and 22 g of GBL (Example 9) were used instead of 22 g of DMAc, respectively.

Example 10
At room temperature, 3 g of polyimide A1 was dissolved in 22 g of GBL to prepare a polyimide solution, and the obtained solution was slowly filtered under pressure using a 5 μm filter. Then, after adding 6.67 g of GBL-ST silica sol to the filtrate and stirring for 30 minutes, oxybis ((3-aminopropyl) dimethylsilane) was added thereto as a catalyst in an amount of 0.5% by mass based on the total mass of the composition. And stirred for 3 minutes to obtain a resin composition.

[Examples 11 to 12]
A method similar to that of Example 6 was used except that 10 g of GBL-UP silica sol (Example 11) and 6.67 g of GBL-M silica sol (Example 12) were used instead of 6.67 g of GBL-ST silica sol, respectively. A resin composition was obtained.

Example 13
At room temperature, 3 g of polyimide A1 was dissolved in 22 g of GBL to prepare a polyimide solution, and the obtained solution was slowly filtered under pressure using a 5 μm filter. Then, 3.33 g of GBL-ST silica sol and 5 g of GBL-UP silica sol were added to the filtrate, stirred for 30 minutes, and the stirred mixture was allowed to stand overnight to obtain a resin composition.

[Examples 14 and 15]
A resin composition was prepared in the same manner as in Example 13 except that 3.33 g of GBL-M silica sol (Example 14) and 4 g of GBL-S silica sol (Example 15) were used instead of 5 g of GBL-UP silica sol. Got.

[4] Preparation of resin thin film (1)
[Example 16]
The resin composition obtained in Example 1 was applied to a glass substrate, and the coating film was sequentially heated at 50 ° C. for 30 minutes, 140 ° C. for 30 minutes, and 200 ° C. for 60 minutes to obtain a resin thin film. In addition, three ovens set to a desired temperature in advance were used for heating.
The obtained resin thin film was peeled off by mechanical cutting and used for subsequent evaluation.

[Examples 17 to 30]
A resin thin film was obtained in the same manner as in Example 16, except that the resin compositions obtained in Examples 2 to 15 were used instead of the resin composition obtained in Example 1.

[5] Evaluation of resin thin film (1)
The heat resistance and optical properties of each resin thin film prepared by the above-mentioned procedure, that is, the linear expansion coefficient (50 to 200 ° C.), the 5% weight loss temperature, the light transmittance and the CIE b value (yellow evaluation), and the retardation Each was evaluated according to the above procedure. Table 1 shows the results.

As shown in Table 1, the resin thin film of the present invention has a low coefficient of linear expansion [ppm / ° C.] (50 to 200 ° C.), a high light transmittance [%] at 400 nm and 550 nm after curing, and It was confirmed that the yellowness represented by the CIE b * value was small and the retardation was suppressed to a low value. In addition, the larger the content of silica sol, the lower the coefficient of linear expansion and the higher the light transmittance.
In addition, the resin thin films of the present invention obtained in Examples 16 to 30 do not crack even when they are held with both hands and bent at an acute angle (about 30 degrees), and are required for a flexible display substrate. It had high flexibility.

[6] Preparation of thin film composition for substrate (2)
[Example 31]
At room temperature, 4.457 g (solid content of polyimide A2: 0.534 g) of the polyimide A2 solution prepared in Synthesis Example 2 was slowly subjected to pressure filtration using a 5 μm filter. Then, 1.426 g of GBL-ZL silica sol and 0.059 g of γ-butyrolactone (GBL) were added to the filtrate, and the mixture was stirred for 30 minutes. Then, the stirred mixture was allowed to stand overnight to obtain a resin composition. .
[Examples 32 to 38]
Except that the addition amount of the polyimide A2 solution prepared in Synthesis Example 2 (the values in the table are the amounts used as a solution), the type and amount of silica sol, and the addition amount of γ-butyrolactone are shown in Table 2 below. A resin composition was obtained in the same manner as in No. 31.

[Example 39]
At room temperature, 2.146 g (polyimide B solid content: 0.239 g) of the polyimide B solution prepared in Synthesis Example 3 was slowly subjected to pressure filtration using a 5 μm filter. Then, 0.639 g of GBL-ZL silica sol and 0.544 g of γ-butyrolactone (GBL) were added to the filtrate, and the mixture was stirred for 30 minutes. Then, the stirred mixture was allowed to stand overnight to obtain a resin composition. .
[Examples 40 to 48]
Except that the addition amount of the polyimide B solution prepared in Synthesis Example 3 (the values in the table are the amounts used as solutions), the type and amount of silica sol, and the addition amount of γ-butyrolactone are as shown in Table 3 below. A resin composition was obtained in the same manner as in No. 39.

[Example 49]
At room temperature, 2.5147 g (solid content of polyimide C: 0.339 g) of the polyimide C solution prepared in Synthesis Example 4 was slowly subjected to pressure filtration using a 5 μm filter. Then, 0.905 g of GBL-ZL silica sol and 0.165 g of GBL were added to the filtrate, and the mixture was stirred for 30 minutes. Then, the stirred mixture was allowed to stand overnight to obtain a resin composition.
[Examples 50 to 64]
Except that the amount of the polyimide C solution prepared in Synthesis Example 4 (the values in the table are the amounts used as solutions), the type and amount of the silica sol, and the amount of γ-butyrolactone were as shown in Table 4 below, In the same manner as in 49, a resin composition was obtained.

[7] Preparation of resin thin film (2)
The resin composition obtained in Example 31 was applied to a glass substrate, and the coating was heated at 50 ° C. for 30 minutes, 140 ° C. for 30 minutes, 220 ° C. for 60 minutes, 280 ° C. for 60 minutes, and sequentially heated to a resin thin film. Got. In addition, four ovens set to a desired temperature in advance were used for heating.
The obtained resin thin film was peeled off by mechanical cutting and used for subsequent evaluation.
Each resin thin film was obtained in the same manner as described above, except that the resin compositions obtained in Examples 32 to 64 were used instead of the resin composition obtained in Example 31.

[8] Evaluation of resin thin film (2)
The heat resistance and optical properties of each resin thin film prepared by the above procedure, that is, the coefficient of linear expansion, 5% weight loss temperature, light transmittance and CIE b value (yellow evaluation), and retardation were evaluated according to the above procedure. did. The results are shown in Tables 2 to 4.

As shown in Tables 2 to 4, the resin thin film of the present invention has a low coefficient of linear expansion [ppm / ° C.] (particularly, 50 to 200 ° C.), and a light transmittance [%] at 400 nm and 550 nm after curing. , The yellowness represented by the CIE b * value was small, the retardation was suppressed to a low value, and the birefringence value Δn was also extremely low. Moreover, the tendency that the linear expansion coefficient was lower as the content of silica sol was larger was shown.
In addition, the resin thin films of the present invention obtained as described above do not crack even when they are held with both hands and bent at an acute angle (about 30 degrees), and exhibit high flexibility required for a flexible display substrate. Had.

Claims (8)

A method for producing a resin thin film,
A polyimide obtained by imidizing the polyamic acid obtained by reacting a diamine component containing an alicyclic tetracarboxylic acid dianhydride MonoNaru component and a fluorine-containing aromatic diamine,
The alicyclic tetracarboxylic dianhydride component contains an alicyclic tetracarboxylic dianhydride represented by the following (C1),
The fluorinated aromatic diamine contains a diamine represented by the following (A1),
The polyimide contains a monomer unit represented by the formula (2) ,

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-4), (X-6) and (X-7).

(In the formula, * represents a bond.)]

(In the formula, B ² represents a divalent group represented by the formula (Y-12).)

(In the formula, * represents a bond)

A method comprising using a composition for forming a resin thin film containing silicon dioxide particles having an average particle size of 100 nm or less, calculated from a specific surface area value measured by a nitrogen adsorption method, and an organic solvent. The method according to claim 1 , wherein the mass ratio of the polyimide and the silicon dioxide particles is 7: 3 to 3: 7. The method according to claim 1, wherein the average particle size is 60 nm or less. Resin thin film manufactured by the method according to any one of claims 1 to 3. A polyimide obtained by imidizing the polyamic acid obtained by reacting a diamine component containing an alicyclic tetracarboxylic acid dianhydride MonoNaru component and a fluorine-containing aromatic diamine,
The alicyclic tetracarboxylic dianhydride component includes an alicyclic tetracarboxylic dianhydride represented by the following (C1),
The fluorinated aromatic diamine contains a diamine represented by the following (A1), and
The polyimide comprises a monomer unit represented by the formula (2) ,

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-4), (X-6) and (X-7).

(In the formula, * represents a bond.)]

(In the formula, B ² represents a divalent group represented by the formula (Y-12).)

(In the formula, * represents a bond)

A composition for forming a resin thin film, comprising silicon dioxide particles having an average particle size of 100 nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and an organic solvent. The resin thin film forming composition according to claim 5 , wherein the mass ratio of the polyimide and the silicon dioxide particles is 7: 3 to 3: 7. The composition for forming a resin thin film according to claim 5 or 6 , wherein the average particle diameter is 60 nm or less. A method for reducing retardation of a resin thin film,
A polyimide obtained by imidizing the polyamic acid obtained by reacting a diamine component containing an alicyclic tetracarboxylic acid dianhydride MonoNaru component and a fluorine-containing aromatic diamine,
The alicyclic tetracarboxylic dianhydride component includes an alicyclic tetracarboxylic dianhydride represented by the following (C1),
The fluorinated aromatic diamine contains a diamine represented by the following (A1), and
The polyimide comprises a monomer unit represented by the formula (2) ,

[In the formula, B ¹ represents a tetravalent group selected from the group consisting of formulas (X-4), (X-6) and (X-7).

(In the formula, * represents a bond.)]

(In the formula, B ² represents a divalent group represented by the formula (Y-12).)

(In the formula, * represents a bond)

Forming a resin thin film using a silicon dioxide particle having an average particle diameter of 100 nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and a resin thin film forming composition containing an organic solvent. Method.