JP6905213B2 - Composition for forming flexible device substrates - Google Patents

Description

The present invention relates to a composition for forming a flexible device substrate, and more specifically, it can be suitably used for forming a flexible device substrate such as a flexible display, which uses a laser lift-off method in a process of peeling the substrate from a carrier substrate. Regarding the composition.

In recent years, with the rapid progress of electronics such as liquid crystal displays and organic electroluminescence displays, there has been a demand for thinner and lighter devices and more flexible devices.
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. It can be made more flexible.
Under these circumstances, polyimide is attracting attention as an alternative material to glass. In addition, the polyimide for this application is required to have not only flexibility but also transparency similar to that of glass in most cases. In order to realize these characteristics, semi-alicyclic polyimides and total alicyclic polyimides obtained by using an alicyclic diamine component or an alicyclic anhydride component as a raw material have been reported (for example, Patent Documents 1 to 1). 3).

On the other hand, in the manufacture of flexible displays, it has been reported that the polymer substrate can be suitably peeled from the glass carrier by using the laser lift-off method (LLO method) which has been used in the manufacture of high-brightness LEDs and three-dimensional semiconductor packages. (For example, Non-Patent Document 1).
In the manufacture of flexible displays, a polymer substrate made of polyimide or the like is provided on a glass carrier, then a circuit or the like including electrodes or the like is formed on the substrate, and finally the substrate is peeled off from the glass carrier together with this circuit or the like. There is a need. When the LLO method is adopted in this peeling step, that is, when a light beam having a wavelength of 308 nm is applied to the glass carrier from a surface opposite to the surface on which the circuit or the like is formed, the light ray having the wavelength is transmitted through the glass carrier and the glass carrier. Only the nearby polymer (polygon) absorbs this light beam and evaporates (sublimates). As a result, it has been reported that the substrate can be selectively peeled from the glass carrier without affecting the circuits provided on the substrate, which determines the performance of the display.

Japanese Unexamined Patent Publication No. 2013-147599 Japanese Unexamined Patent Publication No. 2014-114429 International Publication No. 2015/152178

Journal of Information Display, 2014, Vol 15, No.1, p.p.1-4

Due to the above-mentioned process advantages, the LLO method is more likely to be adopted as an extremely superior substrate peeling method in the manufacture of flexible displays. As the practicality of flexible displays and the reality of mass production increase, the demand for polymer substrates for flexible displays to which the LLO method can be applied also increases.
In order to enable the adoption of the LLO method in the manufacture of flexible displays, it is required that the polymer substrate absorbs light rays of a specific wavelength. However, the semi-alicyclic polyimides and full alicyclic polyimides, which are promising substrate materials for flexible displays, have been proposed so far and contain an alicyclic portion, so that the absorption of light in the visible light region is suppressed and the light becomes transparent. On the other hand, the absorption of light in the ultraviolet light region is also suppressed, and in many cases, the light rays in the ultraviolet light region (for example, 308 nm) that make the LLO method applicable are not sufficiently absorbed.
Due to such a trade-off relationship, the LLO method cannot often be applied to existing materials including semi-alicyclic polyimides and full alicyclic polyimides. Therefore, in the field of flexible displays, absorption in the visible light region is suppressed and the transparency is sufficiently excellent, and at the same time, light rays of a specific wavelength (for example, 308 nm) to which the LLO method can be applied are sufficiently absorbed. There is a demand for a substrate material with.

The present invention has been made in view of such circumstances, and is excellent as a base film for a flexible device substrate such as a flexible display substrate, which has not only excellent heat resistance and flexibility but also low retardation. To provide a composition for forming a flexible device substrate that provides a resin thin film having performance, particularly a thin film capable of sufficiently absorbing light of a specific wavelength (308 nm) to which a laser lift-off method can be applied while ensuring transparency in the visible light region. It is an object of the present invention to provide a composition for forming a flexible device substrate capable of forming a flexible device substrate.

As a result of diligent studies to achieve the above object, the present inventors have found that a resin thin film in which titanium dioxide particles and silicon dioxide particles are mixed with polyimide having an alicyclic skeleton in the main chain has excellent heat resistance. It also has the characteristics of low polyimide and excellent flexibility, and by setting the blending amount of the silicon dioxide within a predetermined range, it has excellent heat resistance, low polyimide, excellent flexibility, and transparency. In particular, by blending a specific amount of the titanium dioxide particles, it is possible to realize a resin thin film that can sufficiently absorb light rays of a specific wavelength to which the LLO method can be applied while ensuring the transparency. , And have found that it can be suitably used as a substrate for flexible devices such as flexible displays, and completed the present invention.

〔式中、Ｂ¹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７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５観点または請求項６に記載のフレキシブルデバイス基板形成用組成物に関する。

（式中、Ｂ²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８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７観点のうちいずれか一項に記載のフレキシブルデバイス基板形成用組成物に関する。
第９観点として、前記二酸化ケイ素粒子の平均粒子径が、６０ｎｍ以下である、第１観点乃至第８観点のうちいずれか一項に記載のフレキシブルデバイス基板形成用組成物に関する。
第１０観点として、レーザーリフトオフ法を適用するフレキシブルデバイスの基板形成用組成物である、第１観点乃至第９観点のうちいずれか一項に記載のフレキシブルデバイス基板形成用組成物に関する。
第１１観点として、第１観点乃至第１０観点のうちいずれか一項に記載のフレキシブルデバイス基板形成用組成物から形成されるフレキシブルデバイス基板に関する。
第１２観点として、第１観点乃至第１０観点のうちいずれか一項に記載のフレキシブルデバイス基板形成用組成物を基材に塗布し、乾燥・加熱してフレキシブルデバイス基板を形成する工程、
レーザーリフトオフ法により前記基材から前記フレキシブルデバイス基板を剥離させる剥離工程を含む、フレキシブルデバイス基板の製造方法に関する。That is, as the first aspect of the present invention, a polyimide having an alicyclic skeleton in the main chain,
Titanium dioxide particles with a particle size of 3 nm to 200 nm,
The present invention relates to a composition for forming a flexible device substrate, which comprises silicon dioxide particles 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 amount of the titanium dioxide particles is 0.1% by mass or more and 20% by mass or less with respect to the total mass of the polyimide, the titanium dioxide particles, and the silicon dioxide particles, as described in the first aspect. The present invention relates to a composition for forming a flexible device substrate.
As a third viewpoint, a compound composed of only hydrogen atoms, carbon atoms, nitrogen atoms and oxygen atoms, which is selected from the group consisting of hydroxy groups, epoxy groups and alkoxy groups having 1 to 5 carbon atoms. A cross-linking agent composed of a compound having two or more and having a cyclic structure.
The present invention relates to the composition for forming a flexible device substrate according to the first aspect.
As a fourth aspect, the flexible device according to the third aspect, wherein the titanium dioxide particles are in an amount of 3% by mass or more and 16% by mass or less with respect to the total mass of the polyimide, the titanium dioxide particles and the silicon dioxide particles. The present invention relates to a composition for forming a substrate.
As a fifth aspect, the polyimide imidizes 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 composition for forming a flexible device substrate according to any one of the first to fourth aspects, which is the obtained polyimide.
As a sixth aspect, the composition for forming a flexible device substrate according to the fifth aspect, wherein the alicyclic tetracarboxylic dianhydride contains 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, multiple Rs represent hydrogen atoms or methyl groups independently of each other, and * represents a bond.)]
As a seventh aspect, the composition for forming a flexible device substrate according to the fifth aspect or claim 6, wherein the fluorine-containing 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 an eighth aspect, the composition for forming a flexible device substrate according to any one of the first to seventh aspects, wherein the mass ratio of the polyimide and the silicon dioxide particles is 7: 3 to 3: 7. Regarding.
As a ninth aspect, the composition for forming a flexible device substrate according to any one of the first to eighth aspects, wherein the average particle size of the silicon dioxide particles is 60 nm or less.
A tenth aspect relates to the flexible device substrate forming composition according to any one of the first to ninth aspects, which is a substrate forming composition for a flexible device to which the laser lift-off method is applied.
As the eleventh viewpoint, the present invention relates to a flexible device substrate formed from the composition for forming a flexible device substrate according to any one of the first to tenth viewpoints.
As a twelfth viewpoint, a step of applying the composition for forming a flexible device substrate according to any one of the first to tenth viewpoints to a substrate, drying and heating to form a flexible device substrate.
The present invention relates to a method for manufacturing a flexible device substrate, which comprises a peeling step of peeling the flexible device substrate from the substrate by a laser lift-off method.

According to the composition for forming a flexible device substrate according to the present invention, it has a low coefficient of linear expansion, excellent heat resistance, high transparency and low retardation, and further excellent flexibility, particularly application of the laser lift-off method. It is possible to form a substrate for a flexible device such as a flexible display that can sufficiently absorb light rays having a specific wavelength (308 nm).
Further, the flexible device substrate according to the present invention has various characteristics required for a substrate for a flexible device such as a flexible display, that is, a low line expansion coefficient and high transparency in the visible light region (high light transmittance, low yellowness). The laser lift-off method can be preferably used when peeling the substrate from the carrier base material because it exhibits low retardation, is excellent in flexibility, and can sufficiently absorb light rays of a specific wavelength (308 nm).
Such a present invention is used in a substrate for a flexil device, which is required to have characteristics such as high flexibility, low coefficient of linear expansion, high transparency (high light transmittance, low yellowness), and low retardation, particularly in the manufacturing process thereof. It is possible to sufficiently cope with the progress in the field of substrates for flexible devices, which can adopt the laser lift-off method.

Hereinafter, the present invention will be described in detail.
The composition for forming a flexible device substrate of the present invention contains the following specific polyimides, titanium dioxide particles, silicon dioxide particles and an organic solvent, and optionally contains a cross-linking agent and other components.

[Polyimide]
The polyimide used in the present invention is a polyimide having an alicyclic skeleton in the main chain, and preferably contains a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a fluorine-containing aromatic diamine. It is a polyimide obtained by imidizing a polyamic acid obtained by reacting with a diamine component contained therein. That is, the polyimide is preferably an imide of a polyamic acid, and the polyamic acid is a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a diamine component containing a fluorine-containing aromatic diamine. It is a reaction product with.
Among them, the alicyclic tetracarboxylic dianhydride contains a tetracarboxylic dianhydride represented by the following formula (C1), and the fluorine-containing aromatic diamine is represented by the following formula (A1). It is preferable that the diamine is contained.

〔式中、Ｂ¹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, multiple Rs represent hydrogen atoms or methyl groups independently of each other, and * represents a bond.)]

（式中、Ｂ²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 above formula (C1), B ¹ in the formula is represented by the formulas (X-1), (X-4), (X-6) and (X-7). The compound to be used is preferable.
Further, among the diamines represented by the above formula (A1), compounds in which B ² in the formula is represented by the formulas (Y-12) and (Y-13) are preferable.
As a suitable 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. Contains the monomer unit represented by the formula (2).

In order to obtain a resin thin film suitable for a flexible device substrate, which has the characteristics of low linear expansion coefficient, low retardation and high transparency, which is the object of the present invention, and has excellent flexibility, a tetracarboxylic dianhydride component is used. The alicyclic tetracarboxylic dianhydride, for example, the tetracarboxylic dianhydride represented by the above formula (C1) is preferably 90 mol% or more, preferably 95 mol% or more, based on the total number of moles of the above. It is more preferable that there is, and in particular, it is optimal that all (100 mol%) are tetracarboxylic dianhydrides represented by the above formula (C1).
Similarly, in order to obtain the resin thin film having the characteristics of low linear expansion coefficient, low retardation and high transparency and excellent flexibility, a fluorine-containing aromatic diamine is obtained with respect to the total number of moles of the diamine component. For example, the diamine represented by the above formula (A1) is preferably 90 mol% or more, and more preferably 95 mol% or more. Further, all of the diamine components (100 mol%) may be diamines 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 (2).

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

The polyimide used in the present invention contains an alicyclic tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride represented by the above formula (C1) and a diamine containing a diamine represented by the formula (A1). In addition to the monomer unit derived from the component, other monomer units may be contained. The content ratio of the other monomer units is arbitrarily determined as long as the characteristics of the resin thin film suitable for the flexible device substrate formed from the 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 above formula (C1) and the diamine component containing the diamine represented by the formula (A1). It is preferably less than 20 mol%, more preferably less than 10 mol%, and even more preferably less than 5 mol%, based on the total number of moles of the monomer units to be produced.

Examples of such other monomer units include, but are not limited to, the monomer unit represented by the formula (3).

In the formula (3), A represents a tetravalent organic group, preferably a tetravalent group represented by any of the following formulas (A-1) to (A-4). Further, in the above formula (3), B represents a divalent organic group, preferably a divalent group represented by any of the formulas (B-1) to (B-11). In each equation, * represents a bond. In the formula (3), when A represents a tetravalent group represented by any of the following formulas (A-1) to (A-4), B is the above-mentioned formulas (Y-1) to (A-4). It may be a divalent group represented by any of 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 represents the above-mentioned formulas (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, for example, only a monomer unit composed of only one of the groups exemplified by the following formula. However, at least one of A and B may contain two or more monomer units selected from the two or more groups exemplified below.

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

Further, the polyimide used in the present invention contains an alicyclic tetracarboxylic acid dianhydride component containing the tetracarboxylic acid dianhydride represented by the above formula (C1) and a diamine represented by the formula (A1). When other monomer units represented by the above formula (3) are contained in addition to the monomer unit derived from the diamine component, the polyimide containing each monomer unit is the above formula (C1) as a tetracarboxylic acid dianhydride component. ), The tetracarboxylic acid dianhydride represented by the following formula (5), the diamine represented by the above formula (A1) as a diamine component, and the following formula (6). It is obtained by polymerizing the diamine to be obtained in an organic solvent and imidizing the obtained polyamic 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, the tetracarboxylic acid dianhydride represented by the formula (5) includes pyromellitic acid dianhydride, 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride, 3,3. ', 4,4'-benzophenone tetracarboxylic acid dianhydride, 3,3', 4,4'-diphenyl ether tetracarboxylic acid dianhydride, 3,3', 4,4'-diphenylsulfone tetracarboxylic acid dianhydride , 4,4'-(hexafluoroisopropylidene) diphthalic hydride, 11,11-bis (trifluoromethyl) -1H-difluoro [3,4-b: 3', 4'-i] xanthene- 1,3,7,9- (11H-tetraone), 6,6'-bis (trifluoromethyl)-[5,5'-biisobenzofuran] -1,1', 3,3'-tetraone, 4 , 6,10,12-Tetrafluorodiflo [3,4-b: 3', 4'-i] dibenzo [b, e] [1,4] dioxine-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 (tri) Aromatic tetracarboxylic acids such as fluoromethyl) biphenyl-4,4'-diyl] bis (1,3-dioxo-1,3-dihydroisobenzofuran-5-carbamide); 1,2-dimethyl-1,2, 3,4-Cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-tetramethyl-1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,2,3,4-cyclopentanetetra Fats such as carboxylic acid dianhydride, 1,2,3,4-cyclohexanetetracarboxylic acid dianhydride, 3,4-dicarboxy-1,2,3,4-tetrahydro-1-naphthalene succinic hydride Cyclic tetracarboxylic dianhydride; aliphatic tetracarboxylic dianhydrides such as 1,2,3,4-butanetetracarboxylic hydride, but are not limited thereto.
Among these, tetracarboxylic acid dianhydride in which A in the formula (5) is a tetravalent group represented by any of the above formulas (A-1) to (A-4) is preferable, that is, 11 , 11-bis (trifluoromethyl) -1H-difluoro [3,4-b: 3', 4'-i] xanthene-1,3,7,9- (11H-tetraone), 6,6'-bis (Trifluoromethyl)-[5,5'-biisobenzofuran] -1,1', 3,3'-tetraone, 4,6,10,12-tetrafluorodifluoro [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'] Difran-1,3,5,7-tetraone can be mentioned as preferred compounds.

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-phenylenediamine, 2,5-dimethoxy-1,4- Phenylene diamine, 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'-(perfluoro) Propane-2,2-diyl) dianiline, 4,4'-oxybis [3- (trifluoromethyl) aniline], 1,4-bis (4-aminophenoxy) benzene, 1,3'-bis (4-amino) Phenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, benzidine, 2-methylbenzidine, 3-methylbenzidine, 2- (trifluoromethyl) benzidine, 3- (trifluoromethyl) benzidine, 2,2 '-Dimethylbenzidine (m-tridin), 3,3'-dimethylbenzidine (o-tridin), 2,3'-dimethylbenzidine, 2,2'-dimethoxybenzidine, 3,3'-dimethoxybenzidine, 2,3 '-Dimethoxybenzidine, 2,2'-dihydroxybenzidine, 3,3'-dihydroxybenzidine, 2,3'-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-aminophenyl) -2,3-dihydro-1,3,3-trimethyl-1H-inden-5 (or 6) amine and other aromatic diamines; 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-diaminoadamantan, 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1, Aliphatic diamines such as 4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1,8-octamethylenediamine, 1,9-nonamethylenediamine. However, it is not limited to these.
Among these, aromatic diamines in which B in the formula (6) is a divalent group represented by any of the above formulas (B-1) to (B-11) are preferable, that is, 2,2'. -Bis (trifluoroolomethoxy)-(1,1'-biphenyl) -4,4'-diamine [also known as 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 known as octafluorobenzidine], 2,3,5,6-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-inden-5 (or 6) amine are listed as preferred diamines. be able to.

From the viewpoint of the mechanical strength of the film to be formed, the content of the polyimide is usually 10% by mass or more, preferably 20% by mass or more, more preferably 20% by mass or more, based on the total solid content of the composition for forming a flexible device substrate. It is 25% by mass or more, and is usually 80% by mass or less, preferably 75% by mass or less, from the viewpoint of the optical characteristics of the low retardation film (thickness direction polyimide (R _{th) and linear expansion coefficient (CTE) do not decrease).} More preferably, it is 70% by mass or less. The solid content means the remaining components excluding the solvent from all the components constituting the composition for forming a flexible device substrate.

<Synthesis of polyamic acid>
As described above, the polyimide used in the present invention is represented by the tetracarboxylic dianhydride component containing the alicyclic tetracarboxylic dianhydride represented by the above formula (C1) and the above formula (A1). It is obtained by imidizing a polyamic acid obtained by reacting with a diamine component containing a fluorine-containing aromatic diamine.
The reaction for obtaining a polyamic acid from the above two components is advantageous in that it can proceed relatively easily in an organic solvent and no by-products are produced.

The charging ratio (molar ratio) of the tetracarboxylic dianhydride component and the diamine component in such a reaction is appropriately set in consideration of the molecular weight of the polyamic acid and the polyimide obtained by subsequent imidization. However, it can be usually about 0.8 to 1.2 of the tetracarboxylic dianhydride component with respect to the diamine component 1, for example, about 0.9 to 1.1, preferably 0.95. It is about 1.02. Similar to a normal polycondensation reaction, the closer the molar ratio is to 1.0, the larger the molecular weight of the polyamic acid produced.

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 the produced polyamic acid is dissolved. Specific examples are given 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 Methylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, isopropyl alcohol, methoxymethylpentanol, dipentene, ethylamyl ketone, methyl nonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, methyl cell solve, ethyl cell solve, 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 monopropyl ether, 3-methyl-3-methoxybutyl acetate, tripropylene glycol methyl ether, 3-methyl-3-methoxybutanol, diisopropyl ether, ethyl isobutyl ether, diisobutylene, amyl Acetate, butylbutyrate, butyl ether, diisobutylketone, methylcyclohexene, propyl ether, dihexy Luether, 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 3-ethoxypropionate, ethyl 3-methoxypropionate, 3-ethoxypropionic acid, 3-methoxypropionic acid, propyl 3-methoxypropionate , Butyl 3-methoxypropionate, diglime, 4-hydroxy-4-methyl-2-pentanone and the like, but are not limited thereto. These may be used alone or in combination of two or more.
Further, even if the solvent does not dissolve the polyamic acid, it may be mixed with the above solvent and used as long as the produced polyamic acid does not precipitate. Further, since the water content in the organic solvent inhibits the polymerization reaction and further causes the produced polyamic acid to be hydrolyzed, it is preferable to use a dehydrated and dried organic solvent as much as possible.

As a method of reacting the tetracarboxylic dianhydride component and the diamine component in an organic solvent, for example, a dispersion or solution in which the diamine component is dispersed or dissolved in an organic solvent is stirred, and the tetracarboxylic dianhydride component is here. A method in which the anhydride component is added as it is, or a method in which the component is dispersed or dissolved in an organic solvent is added, or conversely, in a dispersion or solution in which the tetracarboxylic dianhydride component is dispersed or dissolved in an organic solvent. Examples thereof include a method of adding a diamine component and a method of alternately adding a tetracarboxylic dianhydride component and a diamine compound component, and the method is not limited to these methods as long as the desired polyamic acid can be obtained.
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 reacted individually in sequence, or may be reacted individually. A low molecular weight compound may be mixed and reacted to obtain a high molecular weight compound.

The temperature at the time of synthesizing the polyamic acid may be appropriately set in the range from the melting point to the boiling point of the solvent used described above. For example, any temperature of -20 ° C to 150 ° C can be selected, but -5. ° C. to 100 ° C., usually about 0 to 100 ° C., preferably about 0 to 70 ° C.
The reaction time cannot be unconditionally defined because it depends on the reaction temperature and the reactivity of the raw material, but it is usually about 1 to 100 hours.
The reaction can be carried out at any raw material concentration, but if the concentration is too low, it becomes difficult to obtain a high-molecular-weight polyamic acid, and if the concentration is too high, the viscosity of the reaction solution becomes too high and uniform stirring is performed. Since it becomes difficult, 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. If necessary, the initial reaction can be carried out at a high concentration, and then an organic solvent can be added.

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

For chemical (catalytic) imidization of polyamic acid, a basic catalyst and an acid anhydride are added to a solution of polyamic acid, and the inside of the system is subjected to a temperature condition of -20 to 250 ° C, preferably 0 to 180 ° C. This can be done by stirring.
The amount of the basic catalyst is 0.5 to 30 mol times, preferably 1.5 to 20 mol times, the amid acid group of the polyamic acid, and the amount of the acid anhydride is 1 to 50 mol times the amid acid group of the polyamic acid. It is twice, preferably 2 to 30 mol times.

Examples of the basic catalyst include amines such as pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, and 1-ethylpiperidine. Among them, pyridine is preferable because it has appropriate basicity for advancing the reaction.
Examples of the acid anhydride include an aliphatic carboxylic acid anhydride such as acetic anhydride and an aromatic carboxylic acid anhydride such as trimellitic anhydride and pyromellitic anhydride. Among them, acetic anhydride is used after the reaction is completed. Is preferable because it facilitates purification.
The imidization rate by catalytic imidization can be controlled by adjusting the amount of catalyst, the reaction temperature, and the reaction time.

In the polyimide used in the present invention, the dehydration ring closure rate (imidization rate) of the amic acid group does not necessarily have to be 100%, and can be arbitrarily adjusted and used according to the application and purpose. Particularly preferably, it is 50% or more.

In the present invention, after filtering the reaction solution, the filtrate may be used as it is, or diluted or concentrated, and titanium dioxide, silicon dioxide, etc., which will be described later, may be blended therein to prepare a composition for forming a flexible device substrate. .. When filtered in this way, not only can the mixing of impurities that can cause deterioration of the heat resistance, flexibility, or coefficient of linear expansion characteristics of the obtained resin thin film be reduced, but also a composition for forming a flexible device substrate can be efficiently obtained. Can be done.

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

<Polymer recovery>
When the polymer component is recovered from the reaction solution of polyamic acid and 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 cellsolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, isopropanol, and water. The polymer which has been put into a poor solvent and precipitated can be recovered by filtration and then dried at normal temperature or by heating under normal pressure or reduced pressure.
Further, by repeating the operation of redissolving the precipitated and recovered polymer in an organic solvent and reprecipitating and recovering the polymer 2 to 10 times, impurities in the polymer can be reduced. At this time, it is preferable to use three or more kinds of poor solvents such as alcohols, ketones, and hydrocarbons as the poor solvent because the purification efficiency is further improved.

The organic solvent that dissolves the resin component 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, dimethyl sulfoxide, tetra. Methylurea, pyridine, dimethylsulfone, hexamethylsulfoxide, γ-butyrolactone, 1,3-dimethyl-imidazolidinone, dipentene, ethylamyl ketone, methylnonyl ketone, methyl ethyl ketone, methyl isoamyl ketone, methyl isopropyl ketone, cyclohexanone, ethylene carbonate , Propylene carbonate, diglime, 4-hydroxy-4-methyl-2-pentanone and the like. Two or more kinds of these solvents may be mixed and used.

[titanium dioxide]
The titanium dioxide (titania) used in the present invention is not particularly limited, but titanium dioxide in the form of particles, for example, particles having a particle size of 3 nm to 200 nm, preferably 3 nm to 50 nm, and more preferably 3 nm to 20 nm may be preferably used. can. By using titanium dioxide particles having a particle size in such a numerical range, it is possible to perform substrate peeling by the laser lift-off method with higher accuracy and higher reproducibility.
In the present invention, the particle size of the titanium dioxide particles is expressed as the primary particle size obtained by observing the titanium dioxide particles in the titanium dioxide sol described later with an electron microscope.
The titanium dioxide may have any of anatas-type, rutile-type, anatas-rutile-mixed-type, and brookite-type crystal structures, and among these, those containing rutile-type are desirable.

In particular, in the present invention, titania-based colloidal particles (colloidal titania) having the above particle size values can be preferably used, and titania sol can be used as the colloidal titania.
The titania-based colloidal particles used in the present invention may be single colloidal particles, a mixture with other high-refractive-index metal oxides described later, or composite oxide colloidal particles.
The method for producing the titania-based colloidal particles is not particularly limited, and can be produced by a conventional method, for example, 1) an ion exchange method, 2) a solution method, or the like.
1) Ion exchange method: Examples thereof include a method of treating an acidic salt of titanium with a hydrogen type ion exchange resin and a method of treating a basic salt of titanium with a hydroxyl group type anion exchange resin.
2) Solving method: A method in which the gel obtained by neutralizing the acid salt of titanium with a salt or neutralizing the basic salt of titanium with an acid is washed and then dissolved with an acid or a base (solving method). Japanese Patent Application Laid-Open No. 4-27168), a method of hydrolyzing an alkoxide of titanium (Japanese Patent Laid-Open No. 2003-176120), or a method of hydrolyzing the basic salt of titanium under heating (Japanese Patent Laid-Open No. 10-245224). ) Etc. can be mentioned.
Examples of the above other metal oxides include Fe ₂ O ₃ , ZrO ₂ , SnO ₂ , Ta ₂ O ₅ , Nb ₂ O ₅ , Y ₂ O ₃ , MoO ₃ , WO ₃ , PbO, In ₂ O ₃ , Examples thereof include Bi ₂ O ₃ and SrO, which can be produced in the same manner as the titania-based colloidal particles described above. Further examples of composite _{oxides, TiO 2 -SnO 2, TiO 2} -ZrO 2, TiO 2 -ZrO 2 -SnO 2, TiO 2 -ZrO 2 -CeO 2 , and the like, as a method for compounding is For example, the methods disclosed in JP-A-2014-38293, JP-A-2001-1226221, JP-A-2000-063119 and the like can be adopted.

Examples of the organic solvent in the above-mentioned titania 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-pyrrolidone. Cyclic amides such as; ethers such as γ-butyrolactone; glycols such as ethyl cellosolve and ethylene glycol, acetonitrile and the like.
The viscosity of the titania sol is about 0.6 mPa · s to 100 mPa · s at 20 ° C.

As an example of a commercially available product of the above-mentioned titania-based colloidal particles (titania sol), for example,
Product name Neutral titania sol TTO-W-5 (Aqueous sol of rutile type ultrafine titanium oxide, silica surface treatment, manufactured by Ishihara Sangyo Co., Ltd.),
Product name TKS-201 (Anatas type acidic sol, manufactured by TAYCA Corporation), Product name KS-202 (Anatas type acidic sol, manufactured by TAYCA Corporation), Product name TKS-203 (Anatas type neutral sol, manufactured by TAYCA Corporation) Made by Co., Ltd.),
Product name CSB (Anatas type water-based acidic sol, manufactured by Sakai Chemical Industry Co., Ltd.), Product name CSB-M (Anatas type water-based neutral sol, manufactured by Sakai Chemical Industry Co., Ltd.),
Product names DC-Ti, DCN-Ti, DCB-Ti (above amorphous water-based sol, manufactured by Fuji Titanium Industry Co., Ltd.), organic sol (Anatas type, solvent: ethylene glycol, toluene-IPA, Fuji Titanium Industry Co., Ltd.) Made),
Product name QUEEN TITANIC series (water-based colloid, manufactured by JGC Catalysts and Chemicals Co., Ltd.), Product name OPTALAKE series (non-aqueous colloids, manufactured by JGC Catalysts and Chemicals Co., Ltd.),
Product name Sun Colloid (registered trademark) HT-R350M7-20 (manufactured by Nissan Chemical Industries, Ltd.) and the like can be mentioned.
The titania sol may be produced by dispersing titania particles in an organic solvent according to a conventional method.
Examples of such an organic solvent include those similar to those described above.
Examples of commercially available titanium particles include the trade name AEROXIDE (registered trademark) TiO ₂ P25 (manufactured by Nippon Aerosil Co., Ltd.).

The content of titanium dioxide is usually 0.1 mass with respect to the total mass of polyimide, titanium dioxide particles and silicon dioxide particles in the composition for forming a flexible device substrate from the viewpoint of ensuring absorption of light having a wavelength of 308 nm. % Or more, preferably 1% by mass or more, more preferably 2% by mass or more, and usually 30% by mass or less, preferably 25% by mass or less, from the viewpoint of obtaining a thin film having excellent transparency in the visible light region with good reproducibility. More preferably, it is 20% by mass or less.
When the composition for forming a flexible device substrate of the present invention contains a cross-linking agent described later, the dioxide is calculated based on the total mass of the polyimide, titanium dioxide particles and silicon dioxide particles in the composition for forming a flexible device substrate. The titanium content is preferably 3% by mass or more and 16% by mass or less.

[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, a thin film having an average particle diameter of 100 nm or less, preferably 5 nm to 100 nm, more preferably 5 nm to 55 nm, and more transparent. From the viewpoint of obtaining good reproducibility, it is preferably 5 nm to 50 nm, more preferably 5 nm to 45 nm, even more preferably 5 nm to 35 nm, and further preferably 5 nm to 30 nm.
In the present invention, the average particle size of the silicon dioxide particles is an average particle size value calculated from the specific surface area value measured by the nitrogen adsorption method using the silicon dioxide particles.

In particular, in the present invention, colloidal silica having the above average particle size value can be preferably used, and silica sol can be used as the colloidal silica. As the silica sol, an aqueous silica sol produced by a known method using an aqueous sodium silicate 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 alcohol in the presence of a catalyst (for example, an alkali catalyst such as ammonia, an organic amine compound or sodium hydroxide). Or an organosilica sol obtained by substituting the silica sol with another organic solvent can also be used. This substitution can be carried out by a usual method such as a distillation method or an ultrafiltration method.
Among these, it is preferable to use an organosilica sol in which the dispersion medium is an organic solvent in the present invention.

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 and the like can be mentioned.
The viscosity of the above organosilica sol is about 0.6 mPa · s to 100 mPa · s at 20 ° C.

Examples of commercially available products of the above organosilica sol include, for example, trade name MA-ST-S (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name MT-ST (methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.). ), Product name MA-ST-UP (Methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), Product name MA-ST-M (Methanol-dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), Product name MA-ST- L (Methanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST-S (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) (Manufactured by Co., Ltd.), trade name IPA-ST-UP (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA-ST-L (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name IPA -ST-ZL (isopropanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name NPC-ST-30 (n-propyl cellosolve dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.), trade name PGM-ST (1- Methoxy-2-propanol dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd., trade name DMAC-ST (dimethylacetamide dispersed silica sol, manufactured by Nissan Chemical Industry 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.), trade name PMA-ST (propylene glycol monomethyl ether acetate dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) (Made by Co., 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 (Methyl ethyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) and trade name MIBK-ST (Methyl isobutyl ketone dispersed silica sol, manufactured by Nissan Chemical Industry Co., Ltd.) and the like can be mentioned, but are not limited thereto.
In the present invention, silicon dioxide, for example, silicon dioxide as mentioned in the above products used as an organosilica sol, may be used as a mixture of two or more.

The content of silicon dioxide is adjusted with respect to the total mass of polyimide, titanium dioxide particles and silicon dioxide particles in the composition for forming a flexible device substrate from the viewpoint of obtaining a thin film having a low linear expansion coefficient with good reproducibility with low retardation. It is usually 20% by mass or more, preferably 30% by mass or more, more preferably 40% by mass or more, and from the viewpoint of the mechanical strength of the film, it is usually 80% by mass or less, preferably 75% by mass or less, more preferably 70% by mass. It is as follows.

[Crosslinking agent]
The composition for forming a flexible device substrate of the present invention may further contain a cross-linking agent, and the cross-linking agent used here is a compound composed of only hydrogen atoms, carbon atoms, nitrogen atoms and oxygen atoms. , A cross-linking agent composed of a compound having two or more groups selected from the group consisting of a hydroxy group, an epoxy group and an alkoxy group having 1 to 5 carbon atoms and having a ring structure. By using such a cross-linking agent, a composition for forming a flexible device substrate, which not only provides a resin thin film having excellent solvent resistance and suitable for a flexible device substrate with good reproducibility, but also has improved storage stability, is realized. can do.
Above all, the total number of hydroxy groups, epoxy groups and alkoxy groups having 1 to 5 carbon atoms per compound in the cross-linking agent is preferably 3 or more from the viewpoint of realizing the solvent resistance of the obtained resin thin film with good reproducibility. From the viewpoint of realizing the flexibility of the obtained resin thin film with good reproducibility, it is preferably 10 or less, more preferably 8 or less, and even more preferably 6 or less.

Specific examples of the ring structure of the cross-linking agent include aryl rings such as benzene, nitrogen-containing atomic heteroaryl rings such as pyridine, pyrazine, pyrimidine, pyridazine, 1,3,5-triazine, cyclopentane, cyclohexane, cycloheptane and the like. Cycloalkane ring, piperidine, piperazine, hexahydropyrimidine, hexahydropyridazine, hexahydro-1,3,5-triazine and other cyclic amines can be mentioned.

The number of ring structures per compound in the cross-linking agent is not particularly limited as long as it is 1 or more, but 1 or 2 is used from the viewpoint of ensuring the solubility of the cross-linking agent in the solvent and obtaining a highly flat resin thin film. preferable.
When two or more ring structures are present, the ring structures may be condensed with each other, and an alkane having 1 to 5 carbon atoms such as a methylene group, an ethylene group, a trimethylene group, and a propane-2,2-diyl group. The ring structures may be bonded to each other via a linking group such as a diyl group.

The molecular weight of the cross-linking agent is not particularly limited as long as it has a cross-linking ability and is soluble in the solvent used, but the solvent resistance of the obtained resin thin film, the solubility of the cross-linking agent itself in an organic solvent, and easy availability. Considering the property, price, etc., it is preferably about 100 to 500, and more preferably about 150 to 400.

The cross-linking agent may further have a group that can be derived from a hydrogen atom, a carbon atom, a nitrogen atom and an oxygen atom, such as a ketone group and an ester group (bond).

Preferred examples of the cross-linking agent include compounds represented by a formula selected from the group consisting of the following formulas (K1) to (K5), and one of the preferred embodiments of the formula (K4) is the formula (K4-). The compound represented by 1) is one of the preferred embodiments of the formula (K5), and examples thereof include the compound represented by the formula (5-1).

In the above formula, each of A ¹ and A ² independently represents an alkane-diyl group having 1 to 5 carbon atoms such as a methylene group, an ethylene group, a trimethylene group, and a propane-2,2-diyl group. Among them, A ¹ is preferably a methylene group or an ethylene group, more preferably a methylene group, and A ² is preferably a methylene group or a propane-2,2-diyl group.

Each X is independently of a hydroxy group, an epoxy group (oxa-cyclopropyl group), or a methoxy group, an ethoxy group, a 1-propyloxy group, an isopropyloxy group, a 1-butyloxy group, a t-butyloxy group, etc. Represents an alkoxy group having 1 to 5 carbon atoms.
Among them, considering the availability and price of the cross-linking agent, X is preferably an epoxy group in the formulas (K1) and (K5), and has 1 to 5 carbon atoms in the formulas (K2) and (K3). An alkoxy group is preferable, and a hydroxy group is preferable in the formula (K4).

In the formula (K4), each n ^{indicates the number of − (A 1} −X) groups bonded to the benzene ring, and is an integer of 1 to 5 independently of each other, preferably 2 to 3 and more preferably. It is 3.

In each compound, each A ¹ is preferably all the same group, and each X is preferably all the same group.

The compounds represented by the above formulas (K1) to (K5) include skeleton compounds such as aryl compounds, heteroaryl compounds and cyclic amines having the same ring structure as the ring structure in each of these compounds, and epoxy alkyl halide compounds. It can be obtained by reacting with an alkoxy halide compound or the like by a carbon-carbon coupling reaction or an N-alkylation reaction, or by hydrolyzing the alkoxy moiety of the product.

As the cross-linking agent, a commercially available product may be used, or one synthesized by a known synthetic method may be used.
Commercially available products include CYMEL® 300, 301, 303LF, 303ULF, 304, 350, 3745, XW3106, MM-100, 323, 325, 327, 328, etc. 385, 370, 373, 380, 1116, 1130, 1133, 1141, 1161, 1168, 3020, 202, 203, 1156, MB-94, MB- 96, MB-98, 247-10, 651, 658, 683, 688, 1158, MB-14, MI-12-I, MI-97-IX, U-65. , UM-15, U-80, U-21-511, U-21-510, U-216-8, U-227-8, U-1050-10, U-1052 -8, U-1054, U-610, U-640, UB-24-BX, UB-26-BX, UB-90-BX, UB-25-BE, UB-30 -B, U-662, U-663, U-1051, UI-19-I, UI-19-IE, UI-21-E, UI-27-EI, U-38 -I, UI-20-E 659, 1123, 1125, 5010, 1170, 1172, NF3041, NF2000, etc. (all made by allnex); TEPIC® V, S , HP, L, PAS, VL, UC (above, manufactured by Nissan Chemical Industry Co., Ltd.), TM-BIP-A (manufactured by Asahi Organic Materials Industry Co., Ltd.), 1, 3, 4, 6 -Tetrax (methoxymethyl) glycol uryl (hereinafter abbreviated as TMG) (manufactured by Tokyo Kasei Kogyo Co., Ltd.), 4,4'-methylenebis (N, N-diglycidylaniline) (manufactured by Aldrich), HP-4032D, HP-7200L, HP-7200, HP-7200H, HP-7200HH, HP-7200HHH, HP-4700, HP-4770, HP-5000, HP-6000, HP-4710, EXA-4850-150, EXA-4850- 1000, EXA-4816, HP-820 (DIC Co., Ltd.), TG-G (Shikoku Kasei Kogyo Co., Ltd.) and the like can be mentioned.

Hereinafter, preferred specific examples of the cross-linking agent will be given, but the present invention is not limited thereto.

The blending amount of the cross-linking agent cannot be unconditionally specified because it is appropriately determined according to the type of the cross-linking agent and the like, but usually, the resin thin film obtained with respect to the total mass of the polyimide, the titanium dioxide and the silicon dioxide. From the viewpoint of ensuring flexibility and suppressing weakening, it is 50% by mass or less, preferably 100% by mass or less, and from the viewpoint of ensuring the solvent resistance of the obtained resin thin film, 0.1% by mass or more, preferably 0.1% by mass or more. It is 1% by mass or more.

[Organic solvent]
The composition for forming a flexible device substrate of the present invention contains an organic solvent in addition to the polyimide, titanium dioxide and silicon dioxide, and optionally a cross-linking agent. The organic solvent is not particularly limited, and examples thereof include the same ones as the specific examples of the reaction solvent used in the preparation of 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 can be mentioned. As the organic solvent, one type may be used alone, or two or more types may be used in combination.
Among these, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ-butyrolactone are preferable in consideration of obtaining a resin thin film having high flatness with good reproducibility.

[Composition for Forming Flexible Device Substrate]
The present invention is a composition for forming a flexible device substrate, which contains the polyimide, titanium dioxide, silicon dioxide, an organic solvent, and optionally a cross-linking agent. Here, the composition for forming a flexible device substrate of the present invention is uniform and does not allow phase separation.
In the composition for forming a flexible device substrate of the present invention, the compounding ratio of the polyimide and the silicon dioxide is preferably polyimide: silicon dioxide = 10: 1 to 1:10, more preferably 8: 2 to 2: 8, for example 7: 3 to 3: 7.
The solid content in the composition for forming a flexible device substrate of the present invention is usually in the range of 0.5 to 30% by mass, but from the viewpoint of film uniformity, it is preferably 5% by mass or more and 20% by mass. It is as follows. The solid content means the remaining components excluding the solvent from all the components constituting the composition for forming a flexible device substrate.
The viscosity of the composition for forming a flexible device substrate is appropriately determined in consideration of the coating method used, the thickness of the resin thin film to be produced, and the like, but is usually 1 to 50,000 mPa · s at 25 ° C. ..

In addition, various organic or inorganic low molecular weight or high molecular weight compounds may be blended in the composition for forming a flexible device substrate of the present invention in order to impart processing characteristics and various functionalities. For example, catalysts, defoamers, leveling agents, surfactants, dyes, plasticizers, fine particles, coupling agents, sensitizers and the like can be used. For example, the catalyst can be added for the purpose of reducing the retardation of the resin thin film and the coefficient of linear expansion.
The composition for forming a flexible device substrate of the present invention can be obtained by dissolving the polyimide obtained by the above method, titanium dioxide and silicon dioxide, and optionally a cross-linking agent in the above-mentioned organic solvent, and the polyimide can be prepared. Titanium dioxide, silicon dioxide, and if desired, a cross-linking agent may be added to the subsequent reaction solution, and the organic solvent may be further added if desired.

[Flexible device board]
The composition for forming a flexible device substrate of the present invention described above is applied to a base material, dried and heated to remove an organic solvent, resulting in high heat resistance, high transparency, moderate flexibility, and moderate flexibility. It is possible to obtain a resin thin film having a linear expansion coefficient, a small retardation, and selectively absorbing light rays having a wavelength of 308 nm, that is, a flexible device substrate.
A flexible device substrate containing the above-mentioned flexible device substrate, that is, the above-mentioned polyimide, the above-mentioned titanium dioxide, silicon dioxide, and optionally a cross-linking agent, that is, a flexible device comprising a cured product of the composition for forming a flexible device substrate of the present invention. Substrates are also the subject of the present invention.

Examples of the base material used for manufacturing the flexible device substrate (resin thin film) include plastics (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetyl cellulose, ABS, AS, norbornene resin, etc.) and metals. , Stainless steel (SUS), wood, paper, glass, silicon wafers, slate and the like.
In particular, when applied as a flexible device substrate, it is preferable that the base material to be applied is glass or a silicon wafer from the viewpoint that existing equipment can be used, and the obtained flexible device substrate exhibits good peelability. Therefore, glass is more preferable. The coefficient of linear expansion of the applied base material is preferably 40 ppm / ° C. or less, more preferably 30 ppm / ° C. or less, from the viewpoint of warping of the base material after coating.

The method for applying the composition for forming a flexible device substrate to a substrate is not particularly limited, but for example, a cast coating method, a spin coating method, a blade coating method, a dip coating method, a roll coating method, and a bar coating method. , Die-coating method, inkjet method, printing method (letter plate, intaglio plate, lithographic plate, screen printing, etc.) and the like, and these can be appropriately used depending on the purpose.

The heating temperature is preferably 300 ° C. or lower. If 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 applications.
Further, considering the heat resistance and the coefficient of linear expansion characteristics of the obtained resin thin film, the applied composition for forming a flexible device substrate is heated at 40 ° C. to 100 ° C. for 5 minutes to 2 hours, and then the heating temperature is gradually increased as it is. It is desirable to raise and finally heat at> 175 ° C. to 280 ° C. for 30 minutes to 2 hours. As described above, by heating at a temperature of two or more steps, that is, a step of drying the solvent and a step of promoting molecular orientation, low thermal expansion characteristics can be exhibited with better reproducibility.
In particular, the applied composition for forming a flexible device substrate is heated at 40 ° C. to 100 ° C. for 5 minutes to 2 hours, then heated at over 100 ° C. to 175 ° C. for 5 minutes to 2 hours, and then at 175 ° C. to 280 ° C. It is preferable to heat for 5 minutes to 2 hours.
Examples of the appliance used for heating include a hot plate and an oven. The heating atmosphere may be under air or under an inert gas such as nitrogen, under normal pressure or under reduced pressure, and different pressures are applied at each stage of heating. You may.

The thickness of the resin thin film is appropriately determined in the range of about 1 to 200 μm in consideration of the type of flexible device, but is usually 1 to 60 μm, especially when it is assumed to be used as a substrate for a flexible display. The thickness is preferably about 5 to 50 μm, and the thickness of the coating film before heating is adjusted to form a resin thin film having a desired thickness.
The method of peeling the resin thin film thus formed from the base material is not particularly limited, and the resin thin film is cooled together with the base material, a cut is made in the thin film, and tension is applied via a roll. A method of peeling off the film can be mentioned.
In particular, in the present invention, a laser lift-off (LLO) method can be adopted as a method for peeling the resin thin film from the base material. That is, by irradiating the base material with light rays having a wavelength of 308 nm from the surface opposite to the surface on which the resin thin film of the base material is formed, the light rays having the wavelength pass through the base material (for example, glass carrier), and the base material The resin thin film can be peeled off from the base material by absorbing this light ray only by the polyimide in the vicinity and evaporating the polyimide in the portion.
The laser light used for peeling the resin thin film from the substrate by the laser lift-off method is not particularly limited, but an excimer laser is preferable, and specifically, the oscillation wavelengths are ArF (193 nm), KrF (248 nm), and XeCl (308 nm). ), XeF (353 nm) and the like, but XeCl (308 nm) is particularly preferable.
As the energy density of the irradiated laser beam, typically, include a range of less than 650 mJ / cm ^2, for example, a range of 500 mJ / cm ² to 530mJ / cm ^2, the range of 500 mJ / cm ² to 515mJ / cm ² And so on.

The resin thin film according to one preferred embodiment of the present invention thus obtained can realize high transparency with a light transmittance of 85% or more at a wavelength of 550 nm. On the other hand, the light transmittance at a wavelength of 308 nm is 5% or less, that is, sufficient light absorption at the wavelength that enables peeling of the resin thin film from the base material to which the laser lift-off method is applied can be achieved.
Further, the resin thin film can have a linear expansion coefficient of 40 ppm / ° C. or less, particularly 10 ppm / ° C. to 35 ppm / ° C. at 30 ° C. to 220 ° C., and is excellent in dimensional stability during heating. Is.
_{Further, the resin thin film has an in-plane retardation R 0} represented by the product of birefringence (difference between two in-plane orthogonal refractive indexes) and a film thickness when the wavelength of incident light is 590 nm, and the thickness. As the average value of the two phase differences obtained by multiplying the two birefringences (differences between the two in-plane refractive indexes and the refractive indexes in the thickness direction) when viewed from the cross section in the longitudinal direction by the film thickness. The feature is that the represented thickness-direction retardation _{Rth is very small.} When the average film thickness of the resin thin film is about 15 μm to 40 μm, the birefringence R _th in the thickness direction is less than 700 nm, for example 450 nm or less, for example 1 nm to 410 nm, and the in-plane birefringence R ₀ is less than 4.5. For example, it is 0.1 to 4.2, and the birefringence Δn has a very low value of less than 0.015, for example 0.0028 to 0.0144.

Since the resin thin film described above has the above-mentioned characteristics, it satisfies each condition required as a base film of a flexible device substrate, and is particularly preferably used as a base film of a flexible device substrate, particularly a flexible display substrate. can.

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited thereto. The abbreviations for the reagents used, the equipment used, and the conditions thereof are as follows.

<Measurement of number average molecular weight (Mn) and weight average molecular weight (Mw)>
Equipment: Showa Denko KK, Showdex GPC-101
Columns: KD803 and KD805
Column temperature: 50 ° C
Elution solvent: DMF, flow rate: 1.5 ml / calibration curve: standard polystyrene

<Acid dianhydride>
CBDA: 1,2,3,4-cyclobutanetetracarboxylic dianhydride BODAxx: Bicyclo [2,2,2] octane-2,3,5,6-tetracarboxylic dianhydride <diamine>
TFMB: 2,2'-bis (trifluoromethyl) benzidine <organic solvent>
NMP: N-methyl-2-pyrrolidone GBL: γ-butyrolactone

[Example of Synthesis of Polyimide (I) (Example of Preparation of Polyimide Solution (PI))]
11.208 g (0.035 mol) of TFMB and 66.56 g of γ-butyrolactone (GBL) were added to a three-necked reaction flask having a nitrogen inlet / outlet and equipped with a Dean-Stark apparatus and a mechanical stirrer, and stirring was started. Then, the temperature was raised to 90 ° C. After the diamine (TFMB) was completely dissolved in the solvent, 4.376 g (0.0175 mol) of BODAxx and 14.26 g of GBL were added, and the mixture was heated at 140 ° C. for 10 minutes under a nitrogen atmosphere. Then, 3.432 g (0.0175 mol) of CBDA and 14.26 g of GBL (γ-butyrolactone) were added, and the mixture was reacted in a nitrogen atmosphere for 10 minutes. 0.152 g of 1-ethylpiperidine was added to the reaction, the temperature was raised to 180 ° C., and the mixture was kept for 7 hours. 86.02 g of GBL was added to the reaction mixture and diluted so that the solid content concentration (concentration of the components excluding the organic solvent) was 10.5% by mass to obtain the desired polyimide solution (PI) (polyimide). Molecular weight of (I): Mw = 169,385, Mn = 54,760).

[Preparation example of titania sol (TiO _2- GBL)]
Methanol-dispersed titania sol manufactured by Nissan Chemical Industry Co. _{, Ltd .: TiO 2-} MeOH ("Sun Colloid (registered trademark) HT-R305M7-20", rutile type, titania solid content: 30.6% by mass) in a 1000 mL round bottom flask. ) 91.13 g and 82.02 g of γ-butyrolactone were added. Then, the flask was vacuum in the flask is connected to a vacuum evaporator, by soaking in warm water bath at about 35 ° C. 60 min, the solvent was replaced with γ- butyrolactone from methanol sol (TiO ₂ -GBL) about 107 0.0 g was obtained (Titania solid content concentration: 26.06% by mass).
In the above titania sol, the primary particle size of the titanium dioxide particles observed with an electron microscope was 10 to 12 nm.

[Example of preparation of silica sol (GBL-M)]
In a 1000 mL round bottom flask, 350 g of methanol-dispersed silica sol manufactured by Nissan Chemical Industry Co., Ltd .: MA-ST-M (silica solid content concentration: 40.4% by mass) and 419 g of γ-butyl lactone were placed. Then, the flask is connected to a vacuum evaporator, the inside of the flask is depressurized, and the flask is immersed in a warm water bath at about 35 ° C. for 20 to 50 minutes. 560.3 g was obtained (silica solid content concentration: 25.25% by mass).
In the above silica sol, the average particle size calculated from the specific surface area value measured by the nitrogen adsorption method was 22 nm. Specifically, the specific surface area of the dry powder of silica sol was measured using a specific surface area measuring device Monosorb MS-16 manufactured by Yuasa Ionics Co., Ltd., and the measured specific surface area S (m ² / g) was used for D. The average primary particle size was calculated by the formula (nm) = 2720 / S.

[Preparation of composition for forming flexible device substrate]
[Example 1]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 9703 g and 0.946 g of GBL were added and stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 2]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 8316 g, 0.1343 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.95 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 3]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 5718 g, 0.053 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.5654 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 4]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 5925 g, 0.0302 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.5648 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 5]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 6133 g, 0.0100 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.5642 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 6]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 6186 g, 0.0050 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.5640 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.
[Example 7]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 37425 g, 0.04029 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.335 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[Example 8]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 5718 g, _{0.05 g of TiO 2-} GBL titania sol (titania solid content concentration: 26.06% by mass) and 1.264 g of GBL are added, 0.029 g of TEPIC-L (purity 99%) is further added, and the mixture is stirred for 30 minutes. , A composition for forming a flexible device substrate was obtained.
[Example 9]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 5198 _{g, 0.1 g of TiO 2-} GBL titania sol (titania solid content concentration: 26.06% by mass) and 1.266 g of GBL are added, 0.029 g of TEPIC-L (purity 99%) is further added, and the mixture is stirred for 30 minutes. , A composition for forming a flexible device substrate was obtained.
[Example 10]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 4678 g, TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) 0.1511 g, GBL 1.268 g were added, and 0.029 g of TEPIC-L (purity 99%) was further added, and the mixture was stirred for 30 minutes. , A composition for forming a flexible device substrate was obtained.
[Example 11]
At room temperature, 1 g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in the synthetic example was added to the GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in the preparation example. 5458 g, 0.0755 g of TiO _2- GBL titania sol (titania solid content concentration: 26.06% by mass) and 0.5654 g of GBL were added, and the mixture was stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[Creation of resin thin film]
The flexible device substrate forming compositions obtained in Examples 1 to 10 are applied to a glass substrate, and the coating film is applied to the glass substrate at 50 ° C. for 30 minutes, 140 ° C. for 30 minutes, 200 ° C. for 60 minutes, and subsequently. A resin thin film was obtained by sequentially heating at 280 ° C. for 60 minutes under a vacuum of −99 kpa.
The obtained thin film was peeled off by mechanical cutting and used for subsequent evaluation.

[Evaluation of thin film]
The heat resistance and optical properties of each resin thin film (evaluation sample) produced by the above procedure, that is, the coefficient of linear expansion (CTE) at 30 ° C to 220 ° C, the 5% weight loss temperature (Td _5% ), and the light transmittance. (T _{308 nm} , T _{550 nm} ), CIE b ^* value (yellow evaluation), retardation (R _th , R ₀ ) and birefringence (Δn) were evaluated according to the following procedure. The results are shown in Table 1.
1) Coefficient of linear expansion (CTE)
Using TMA Q400 manufactured by TA Instruments, the thin film is cut into a size of 5 mm in width and 16 mm in length, first heated at 10 ° C./min and heated to 50 to 300 ° C. (first heating), and then 10 ° C. Linear expansion of the second heating at 30 ° C to 220 ° C when the temperature is lowered at / min and cooled to 50 ° C, then the temperature is raised at 10 ° C / min and heated to 30 ° C to 420 ° C (second heating). It was determined by measuring the value of the coefficient (CTE [ppm / ° C]). A load of 0.05 N was applied through the first heating, cooling and the second heating.
2) 5% weight loss temperature (Td _5% )
The 5% weight loss temperature (Td _5% [° C.]) is measured by raising the temperature of about 5 to 10 mg of a thin film in nitrogen to 50 to 800 ° C. at 10 ° C./min using TGA Q500 manufactured by TA Instruments. I asked for it.
3) CIE b value (CIE b ^* )
The CIE b value (CIE b ^* ) was measured using a SA4000 spectrometer manufactured by Nippon Denshoku Kogyo Co., Ltd. at room temperature using the reference as air.
4) Light transmittance (transparency) (T _308nm , T _550nm )
_{The light transmittances (T 308 nm} , T _{550 nm} [%]) at wavelengths of 308 nm and 550 nm were measured using UV-3600 manufactured by Shimadzu Corporation at room temperature and using air as a reference.
5) Reference (R _th , R ₀ )
Thickness direction retardation (R _th ) and in-plane retardation (R ₀ ) were measured at room temperature using KOBURA 2100ADH manufactured by Oji Measuring Instruments Co., Ltd.
The thickness direction retardation (R _th ) and the in-plane retardation (R ₀ ) are calculated by the following formulas.
R ₀ = (Nx−Ny) × d = ΔNxy × d
R _th = [(Nx + Ny) / 2-Nz] x d = [(ΔNxz × d) + (ΔNyz × d) / 2
Nx, Ny: Two orthogonal refractive indexes in the plane (Nx> Ny, Nx is also referred to as a slow axis, and Ny is also referred to as a phase advance axis).
Nz: Refractive index in the thickness (vertical) direction (vertical) with respect to the plane d: Film thickness ΔNxy: Difference between two refractive indexes in the plane (Nx-Ny) (birefringence)
ΔNxz: Difference between in-plane refractive index Nx and refractive index Nz in the thickness direction (birefringence)
ΔNyz: Difference between in-plane refractive index Ny and refractive index Nz in the thickness direction (birefringence)
6) Film thickness (d)
The film thickness of the obtained thin film was measured with a thickness gauge manufactured by Teclock Co., Ltd.
7) Birefringence (Δn)
_{Using the value of the thickness direction retardation (R th} ) obtained by the above-mentioned <5) retardation>, it was calculated by the following formula.
ΔN = [R _th / d (film thickness)] / 1000

[Solvent resistance test]
At room temperature, the flexible device substrate forming compositions obtained in Examples 1 and 3 to 10 were applied onto a glass substrate, and the coating film was fired onto a resin thin film obtained by TOK-106 (Tokyo). After dropping a few drops of Oka Kogyo Co., Ltd., the mixture was heated in an air oven at 60 ° C. for 3 minutes. Then, after wiping off TOK-106, the appearance of the thin film was visually confirmed.
The appearance of the thin film before and after this test was visually observed and evaluated according to the following criteria.
◯: The thin film does not shrink or expand after the solvent test Δ: The thin film shrinks or expands slightly after the solvent test ×: The thin film dissolves or shrinks or expands after the solvent test

[Flexibility evaluation]
When the obtained thin film was held with both hands and bent at an acute angle (about 30 degrees), the one that did not crack was evaluated as ◯, and the one that cracked was evaluated as x.

Table 1 shows the results of the optical properties of the resin thin film obtained from each flexible device substrate forming composition, and Table 2 shows the results of the heat resistance and solvent resistance tests.

As shown in Table 1, the resin thin films obtained from the flexible device substrate forming compositions of Examples 2 to 11 have a high light transmittance [%] at a wavelength of 550 nm, while the light transmittance at a wavelength of 308 nm is 5. The result was less than%, suggesting that the laser lift-off method can be applied. Further, the resin thin film has a ^{low yellowness (CIE b *} ), an extremely low thickness direction retardation R _th of 404 nm or less, an in-plane retardation R ₀ of 4.2 nm or less, and a birefringence Δn of less than 0.015. It was an extremely low value. Further, as shown in Table 2, the resin thin film has a low coefficient of linear expansion [ppm / ° C] (30 to 220 ° C) (less than 31 ppm / ° C), improved heat resistance, and has flexibility. .. Further, in Examples 8 to 10, it was obtained that the solvent was resistant to the solvent.
On the other hand, although the resin thin film of Example 1 had the same heat resistance and optical characteristics as those of Examples 2 to 11, the light transmittance at a wavelength of 308 nm was as high as 66.5%, and the resin thin film from the base material was used. The results suggest that it is difficult to apply the laser lift-off method for peeling.

[Peeling of resin thin film by LLO method]
The flexible device substrate forming composition obtained in Examples 1 and 11 was applied to a glass substrate, and the coating film was applied to the glass substrate at 50 ° C. for 30 minutes, 140 ° C. for 30 minutes, 200 ° C. for 60 minutes, and then-. A resin thin film was obtained by sequentially heating at 280 ° C. for 60 minutes under a vacuum of 99 kpa.
It was evaluated whether or not the resin thin film prepared above was peeled off by the LLO method.
The following conditions were adopted as the LLO method.
Laser light source: Maxima laser XeCl (308nm)
Energy ^{Density: 420mJ / cm 2, 500mJ /} cm 2, 515mJ / cm 2, 530mJ / cm 2, 560mJ / cm 2, 630mJ / cm 2
Stage movement speed: 7.8 mm / sec Laser beam size: 14 mm x 1.3 mm (size at maximum energy: 7.8 mm x 1.3 mm), laser light overlapping scanning range is 80%
The results are shown in Table 3.
In the table, ◯ indicates that the resin thin film was peeled off, Δ indicates that there was a partial defect, and × indicates that the resin thin film was not peeled off.

As shown in Table 3, it was confirmed that the resin thin film of the present invention shown in Example 11 can be peeled off by the LLO method. On the other hand, the resin thin film of Example 1 containing no _{TiO 2 was not peeled off under the same conditions.}

As described above, the composition for forming a flexible device substrate of the present invention has the characteristics of low coefficient of linear expansion, high transparency (high light transmittance, low yellowness), low retardation, and also imparts excellent solvent resistance. That is, it is a material capable of forming a resin thin film that meets the requirements required as a base film for a flexible device substrate. In particular, since the resin thin film sufficiently absorbs light rays of a specific wavelength (308 nm) and the laser lift-off method can be applied, it is particularly preferably used as a base film for a flexible device substrate for mass production of flexible devices. Can be expected to be possible.

Claims (7)

Polyimide with an alicyclic skeleton in the main chain,
Titanium dioxide particles with a particle size of 3 nm to 200 nm,
A composition containing silicon dioxide particles having an average particle diameter of 100 nm or less calculated from the specific surface area value measured by the nitrogen adsorption method, and an organic solvent.
The polyimide contains a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride containing a tetracarboxylic dianhydride represented by the formula (C1) and a diamine represented by the formula (A1). a polyimide obtained polyamic acid obtained by reacting a diamine component containing a fluorine-containing aromatic diamine imidized,
The titanium dioxide particles are in an amount of 0.1% by mass or more and 20% by mass or less with respect to the total mass of the polyimide, the titanium dioxide particles and the silicon dioxide particles.
The mass ratio of the polyimide to the silicon dioxide particles is 7: 3 to 3: 7.
A composition for forming a flexible device substrate.

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

(In the formula, multiple Rs represent hydrogen atoms or methyl groups independently of each other, and * represents a bond.)]

(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.) Further, it is a compound composed of only hydrogen atoms, carbon atoms, nitrogen atoms and oxygen atoms, and has two or more groups selected from the group consisting of hydroxy groups, epoxy groups and alkoxy groups having 1 to 5 carbon atoms. Moreover, it contains a cross-linking agent composed of a compound having a cyclic structure.
The composition for forming a flexible device substrate according to claim 1. The flexible device substrate according to claim 1 or 2 , wherein the titanium dioxide particles are in an amount of 3% by mass or more and 16% by mass or less with respect to the total mass of the polyimide, the titanium dioxide particles, and the silicon dioxide particles. Composition for formation. The composition for forming a flexible device substrate according to any one of claims 1 to 3 , wherein the silicon dioxide particles have an average particle size of 60 nm or less. The flexible device substrate forming composition according to any one of claims 1 to 4 , which is a composition for forming a substrate of a flexible device to which the laser lift-off method is applied. A flexible device substrate formed from the composition for forming a flexible device substrate according to any one of claims 1 to 5. A step of applying the composition for forming a flexible device substrate according to any one of claims 1 to 5 to a substrate, drying and heating to form a flexible device substrate.
A method for manufacturing a flexible device substrate, which comprises a peeling step of peeling the flexible device substrate from the substrate by a laser lift-off method.