CN108473764B

CN108473764B - Composition for forming flexible device substrate

Info

Publication number: CN108473764B
Application number: CN201780005922.3A
Authority: CN
Inventors: 小山欣也; 北浩; 叶镇嘉; 何邦庆
Original assignee: Nissan Chemical Corp
Current assignee: Nissan Chemical Corp
Priority date: 2016-01-08
Filing date: 2017-01-05
Publication date: 2021-09-28
Anticipated expiration: 2037-01-05
Also published as: TWI775739B; JP6905213B2; CN108473764A; TW201739838A; JPWO2017119450A1; KR20180102081A; WO2017119450A1

Abstract

The purpose of the present invention is to provide a composition for forming a substrate for a flexible device, which can obtain a resin film having excellent heat resistance and low retardation, particularly a resin film suitable as a substrate for a flexible device, and which can obtain a resin film that absorbs light having a specific wavelength and can be applied to a laser lift-off method. The composition for forming a flexible device substrate comprises a polyimide, titanium dioxide particles having a particle diameter of 3 to 200nm, silica particles having an average particle diameter of 100nm or less calculated from a specific surface area value measured by a nitrogen adsorption method, and an organic solvent, and a resin film formed from the composition for forming a flexible device substrate.

Description

Composition for forming flexible device substrate

Technical Field

The present invention relates to a composition for forming a flexible device substrate, and more particularly, to a composition which can be suitably used for forming a flexible device substrate for a flexible display or the like, in which a laser lift-off method is used in a lift-off process for lifting off a substrate from a carrier base material.

Background

In recent years, with rapid progress in electronic devices such as liquid crystal displays and organic electroluminescence displays, thinning, weight reduction, and flexibility of devices have been required.

In these devices, various electronic components such as a thin film transistor and a transparent electrode are formed on a glass substrate, and the glass material is replaced with a flexible and lightweight resin material, whereby the device itself can be made thin, light, and flexible.

Under such circumstances, polyimide has attracted attention as an alternative material to glass. Therefore, not only flexibility but also transparency similar to that of glass is required for polyimide to be used for this purpose in many cases. In order to achieve these properties, semi-alicyclic polyimides and full-alicyclic polyimides obtained by using an alicyclic diamine component and an alicyclic anhydride component as raw materials have been reported (see, for example, patent documents 1 to 3).

On the other hand, regarding the manufacture of flexible displays, there are reports of: the polymer substrate can be favorably peeled from the glass carrier by using a laser lift-off method (LLO method) which has been used in the production of high-brightness LEDs, three-dimensional semiconductor packages, and the like (for example, non-patent document 1).

It is reported that: in the manufacture of a flexible display, it is necessary to provide a polymer substrate made of polyimide or the like on a glass carrier, form a circuit or the like including electrodes or the like on the substrate, and finally peel the substrate together with the circuit or the like from the glass carrier. If the LLO method is adopted in this peeling step, that is, light having a wavelength of 308nm is irradiated to the glass carrier from the surface opposite to the surface on which the circuit and the like are formed, the light having the wavelength is transmitted through the glass carrier, and only the polymer (polyimide) in the vicinity of the glass carrier absorbs the light and evaporates (sublimes). As a result, the substrate can be selectively peeled from the glass carrier without affecting the circuit and the like provided on the substrate, which determines the performance of the display.

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2013-147599

Patent document 2: japanese patent laid-open No. 2014-114429

Patent document 3: international publication No. 2015/152178

Non-patent document

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

Disclosure of Invention

Problems to be solved by the invention

The LLO method is highly advantageous in the above process, and therefore, the LLO method is more likely to be used as a substrate peeling method which is extremely advantageous in manufacturing a flexible display. Further, as the practical use of flexible displays and the realization of mass production increase, the demand for polymer substrates for flexible displays to which the LLO method can be applied is increasing.

In order to be able to use the LLO method in the manufacture of flexible displays, the polymer substrate is required to absorb light of a specific wavelength. However, semi-alicyclic polyimide and full-alicyclic polyimide, which have been proposed so far as promising as substrate materials for flexible displays, have excellent transparency by suppressing absorption of light in the visible light region because they contain alicyclic sites, and on the other hand, absorption of light in the ultraviolet light region is also suppressed in many cases, and light in the ultraviolet light region (for example, 308nm) to which the LLO method can be applied is not sufficiently absorbed.

Due to such a trade-off relationship, the LLO method is not often applied to existing materials including semi-alicyclic polyimide and full-alicyclic polyimide. Therefore, in the field of flexible displays, a substrate material having the following characteristics is required: absorption in the visible light region is suppressed to sufficiently improve transparency, and light having a specific wavelength (for example, 308nm) to which the LLO method can be applied is sufficiently absorbed.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a composition for forming a flexible device substrate, which can obtain a resin thin film having excellent performance as a base film (base film) of a flexible device substrate such as a flexible display substrate having characteristics of excellent heat resistance and flexibility and low retardation (retadation), and particularly to provide a composition for forming a flexible device substrate, which can form a thin film capable of securing transparency in the visible light region and sufficiently absorbing light of a specific wavelength (308nm) to which a laser lift-off method can be applied.

Means for solving the problems

As a result of intensive studies to achieve the above object, the present inventors have found that a resin film obtained by blending titanium dioxide particles and silica particles into a polyimide having an alicyclic skeleton in the main chain has the characteristics of excellent heat resistance, low retardation, and further excellent flexibility, that a resin film having excellent heat resistance, low retardation, excellent flexibility, and further excellent transparency can be obtained by adjusting the blending amount of the silica to a predetermined range, and that a resin film having the transparency and capable of sufficiently absorbing light having a specific wavelength to which the LLO method can be applied can be obtained by blending a specific amount of the titanium dioxide particles, and that the resin film can be suitably used for a substrate for a flexible device such as a flexible display.

That is, the present invention relates to, as a1 st aspect, a composition for forming a flexible device substrate, comprising:

a polyimide having an alicyclic skeleton in its main chain,

titanium dioxide particles with the particle size of 3 nm-200 nm,

silica particles having an average particle diameter of 100nm or less, the average particle diameter being calculated from a specific surface area value measured by a nitrogen adsorption method, and

an organic solvent.

A second aspect of the present invention is the composition for forming a flexible device substrate according to the first aspect of the present invention 1, wherein the titanium dioxide particles are in an amount of 0.1 mass% or more and 20 mass% or less based on the total mass of the polyimide, the titanium dioxide particles and the silicon dioxide particles.

A 3 rd aspect of the present invention relates to the composition for forming a flexible device substrate according to the 1 st aspect, further comprising a crosslinking agent composed of a compound having 2 or more groups selected from a hydroxyl group, an epoxy group and an alkoxy group having 1 to 5 carbon atoms and having a cyclic structure, the compound being composed of only a hydrogen atom, a carbon atom, a nitrogen atom and an oxygen atom.

A4 th aspect of the present invention relates to the composition for forming a flexible device substrate according to the 3 rd aspect, wherein the titanium dioxide particles are in an amount of 3 mass% or more and 16 mass% or less with respect to a total mass of the polyimide, the titanium dioxide particles and the silicon dioxide particles.

A 5 th aspect of the present invention relates to the composition for forming a flexible device substrate according to any one of the 1 st to 4 th aspects, wherein the polyimide 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.

An aspect 6 relates to the composition for forming a flexible device substrate according to aspect 5, wherein the alicyclic tetracarboxylic dianhydride comprises a tetracarboxylic dianhydride represented by formula (C1).

[ in the formula, B¹Represents a 4-valent group selected from the group consisting of the formulae (X-1) to (X-12).

(wherein R's each independently represents a hydrogen atom or a methyl group; and represents a bond.)

In view 7, the composition for forming a flexible device substrate according to view 5 or 6, wherein the fluorine-containing aromatic diamine comprises a diamine represented by the formula (a 1).

H₂N-B²-NH₂ (A1)

(in the formula, B²Represents a 2-valent group selected from the group consisting of formulas (Y-1) to (Y-34). )

(wherein, represents a bond.)

An 8 th aspect of the present invention is the composition for forming a flexible device substrate according to any one of the 1 st to 7 th aspects, wherein a mass ratio of the polyimide to the silica particles is 7: 3-3: 7.

a 9 th aspect of the present invention relates to the composition for forming a flexible device substrate according to any one of 1 st to 8 th aspects, wherein the silica particles have an average particle diameter of 60nm or less.

A 10 th aspect relates to the composition for forming a flexible device substrate according to any one of the 1 st to 9 th aspects, wherein the composition is a composition for forming a substrate of a flexible device to which a laser lift-off method is applied.

From viewpoint 11, the present invention relates to a flexible device substrate formed from the composition for forming a flexible device substrate according to any one of viewpoints 1 to 10.

As a 12 th aspect, the present invention relates to a method for manufacturing a flexible device substrate, including the steps of:

a step of forming a flexible device substrate by applying the composition for forming a flexible device substrate according to any one of aspects 1 to 10 to a base material, drying and heating the composition,

and a peeling step of peeling the flexible device substrate from the base material by a laser peeling method.

Effects of the invention

According to the composition for forming a flexible device substrate of the present invention, a substrate for a flexible device such as a flexible display having a low linear expansion coefficient, excellent heat resistance, high transparency, low retardation, and excellent flexibility, and capable of sufficiently absorbing light having a specific wavelength (308nm) to which a laser lift-off method is applicable, can be formed with good reproducibility.

The flexible device substrate according to the present invention exhibits various characteristics required for a substrate for a flexible device such as a flexible display, that is, a low linear expansion coefficient, high transparency in a visible light region (high light transmittance, low yellowness index), low retardation, and further excellent flexibility, and particularly, can sufficiently absorb light of a specific wavelength (308nm), and therefore, when the substrate is peeled from a carrier base, a laser peeling method can be suitably used.

The present invention can sufficiently cope with the progress in the field of substrates for flexible devices, which require characteristics such as high flexibility, low linear expansion coefficient, high transparency (high light transmittance, low yellowness index), and low retardation, and particularly substrates for flexible devices, which can be produced by a laser lift-off method.

Detailed Description

The present invention will be described in detail below.

The composition for forming a flexible device substrate of the present invention contains the following specific polyimide, titanium dioxide particles, silica particles, and an organic solvent, and if necessary, a crosslinking agent and other components.

[ polyimide ]

The polyimide used in the present invention is a polyimide having an alicyclic skeleton in the main chain, and is preferably 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. That is, the polyimide is preferably an imide compound of polyamic acid, and the polyamic acid is a reaction product of a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride and a diamine component containing a fluorine-containing aromatic diamine.

Among them, the alicyclic tetracarboxylic dianhydride preferably includes a tetracarboxylic dianhydride represented by the following formula (C1), and the fluorine-containing aromatic diamine preferably includes a diamine represented by the following formula (a 1).

H₂N-B²-NH₂ (A1)

(wherein, represents a bond.)

Among the tetracarboxylic dianhydrides represented by the formula (C1), B in the formula is preferred¹Is a compound represented by the formula (X-1), (X-4), (X-6) or (X-7).

Among the diamines represented by the above formula (A1), B in the formula is preferable²Is a compound represented by the formula (Y-12) or (Y-13).

As a preferable example, the polyimide obtained by imidizing the polyamic acid obtained by reacting the tetracarboxylic dianhydride represented by the formula (C1) with the diamine represented by the formula (a1) contains a monomer unit represented by the formula (2) described later.

In order to obtain a resin film which has characteristics of a low linear expansion coefficient, a low retardation, and a high transparency, is excellent in flexibility, and is suitable for a flexible device substrate, the alicyclic tetracarboxylic dianhydride, for example, the tetracarboxylic dianhydride represented by the above formula (C1) is preferably 90 mol% or more, more preferably 95 mol% or more, and particularly preferably the tetracarboxylic dianhydride represented by the above formula (C1) is contained in the whole (100 mol%) with respect to the total molar number of the tetracarboxylic dianhydride components.

Similarly, in order to obtain the resin film having the characteristics of low linear expansion coefficient, low retardation, and high transparency and excellent flexibility, the fluorine-containing aromatic diamine, for example, the diamine represented by the formula (a1), is preferably 90 mol% or more, and more preferably 95 mol% or more, based on the total molar number of the diamine component. The total (100 mol%) of the diamine component may be a diamine represented by the above formula (a 1).

As an example of a preferable embodiment, the polyimide used in the present invention contains a monomer unit represented by the following formula (2).

The monomer unit represented by the above formula (2) is preferably a monomer unit represented by the formula (2-1) or the formula (2-2), and more preferably a monomer unit represented by the formula (2-1).

The polyimide used in the present invention may contain other monomer units in addition to the monomer units 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 (a 1). The content ratio of the other monomer unit can be arbitrarily determined as long as the properties of the resin film suitable for use in the flexible device substrate formed from the composition of the present invention are not impaired. The proportion is preferably less than 20 mol%, more preferably less than 10 mol%, and still more preferably less than 5 mol% relative to the total number of moles of monomer units derived from an alicyclic tetracarboxylic dianhydride component comprising a tetracarboxylic dianhydride represented by the above formula (C1) and a diamine component comprising a diamine represented by the formula (a 1).

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

In the formula (3), A represents a 4-valent organic group, preferably a 4-valent group represented by any one of the following formulae (A-1) to (A-4). In the formula (3), B represents a 2-valent organic group, preferably a 2-valent group represented by any one of the formulae (B-1) to (B-11). Wherein, represents a bond. In the formula (3), when A represents a 4-valent group represented by any one of the following formulae (A-1) to (A-4), B may be a 2-valent group represented by any one of the formulae (Y-1) to (Y-34). Alternatively, in formula (3), when B represents a 2-valent group represented by any one of formulae (B-1) to (B-11), A may be a 4-valent group represented by any one of formulae (X-1) to (X-12).

In the polyimide of the present invention, when the monomer unit represented by formula (3) is contained, for example, a monomer unit in which a and B are composed of only one kind of group represented by the following formula may be contained, or a monomer unit in which at least one of a and B is formed of two or more kinds selected from two or more kinds of groups represented by the following formula may be contained.

In the polyimide used in the present invention, the monomer units are bonded in an arbitrary order.

Further, in the case where the polyimide used in the present invention contains other monomer units represented by the above formula (3) in addition to monomer units derived from an alicyclic tetracarboxylic dianhydride component containing a tetracarboxylic dianhydride represented by the above formula (C1) and a diamine component containing a diamine represented by the above formula (a1), the polyimide containing each monomer unit can be obtained as follows: the polyimide resin is obtained by polymerizing a tetracarboxylic dianhydride represented by the formula (C1) and a tetracarboxylic dianhydride represented by the formula (5) as tetracarboxylic dianhydride components, and a diamine represented by the formula (a1) and a diamine represented by the formula (6) as diamine components in an organic solvent, and imidizing the obtained polyamic acid.

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

Specifically, examples of the tetracarboxylic acid dianhydride represented by the formula (5) include pyromellitic acid dianhydride, 3 ', 4,4 ' -biphenyltetracarboxylic acid dianhydride, 3 ', 4,4 ' -benzophenonetetracarboxylic acid dianhydride, 3 ', 4,4 ' -diphenylethertetracarboxylic acid dianhydride, 3 ', 4,4 ' -diphenylsulfonetetracarboxylic acid dianhydride, 4,4 ' - (hexafluoroisopropylidene) diphenyldicarboxylic acid dianhydride, 11-bis (trifluoromethyl) -1H-difluoro [3, 4-b: 3 ', 4' -i]

Ton-1, 3,7,9- (11H-tetraone), 6 '-bis (trifluoromethyl) - [5, 5' -diisobenzofuran]-1,1 ', 3, 3' -tetrone, 4,6,10, 12-tetrafluorodifurano [3, 4-b: 3 ', 4' -i]Dibenzo [ b, e ]][1,4]II

-1,3,7, 9-tetrone, 4, 8-bis (trifluoromethoxy) benzo [1, 2-c: 4, 5-c']Difuran-1, 3,5, 7-tetraone, N ' - [2,2 ' -bis (trifluoromethyl) biphenyl-4, 4 ' -diyl]Aromatic tetracarboxylic acids such as bis (1, 3-dioxo-1, 3-dihydroisobenzofuran-5-carboxamide); alicyclic tetracarboxylic acid dianhydrides such as 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-cyclopentane tetracarboxylic acid dianhydride, 1,2,3, 4-cyclohexane tetracarboxylic acid dianhydride, and 3, 4-dicarboxyl-1, 2,3, 4-tetrahydro-1-naphthalene succinic acid dianhydride; aliphatic tetracarboxylic acid dianhydrides such as 1,2,3, 4-butanetetracarboxylic acid dianhydride, but is not limited thereto.

Among them, tetracarboxylic dianhydrides in which A in the formula (5) is a 4-valent group represented by any one of the formulae (A-1) to (A-4) are preferable, and examples thereof include 11, 11-bis (trifluoromethyl) -1H-difluoro [3, 4-b: 3 ', 4' -i]

-1,3,7, 9-tetrone, 4, 8-bis (trifluoromethoxy) benzo [1, 2-c: 4, 5-c']Difuran-1, 3,5, 7-tetraone is a preferred compound.

Further, examples of the diamine represented by the formula (6) include 2- (trifluoromethyl) benzene-1, 4-diamine, 5- (trifluoromethyl) benzene-1, 3-diamine, 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-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 ' - (perfluoropropane-2, 2-diyl) diphenylamine, 4 ' -oxybis [3- (trifluoromethyl) aniline ], 1, 4-bis (4-aminophenoxy) benzene, 2, 5-dimethoxy-1, 4-phenylenediamine, 2, 5-difluorobenzene-1, 4-diamine, 2-dichloro-diamine, 4-difluorobenzene, 4 ' -oxybis (trifluoromethyl) aniline, 1, 4-bis (4-aminophenoxy) benzene, 2, 4-bis (2-tetrafluoro) aniline, 4-phenylene, 2, 4-bis (2, 4-tetrafluoro) aniline, 2, 4-tetrafluoro-phenylene, 4, 2, 4, 2, and a mixture thereof, 1,3 ' -bis (4-aminophenoxy) benzene, 1, 4-bis (3-aminophenoxy) benzene, benzidine, 2-methylbenzidine, 3-methylbenzidine, 2- (trifluoromethyl) benzidine, 3- (trifluoromethyl) benzidine, 2 ' -dimethylbenzidine (m-tolidine), 3 ' -dimethylbenzidine (o-tolidine), 2,3 ' -dimethylbenzidine, 2 ' -dimethoxybenzidine, 3 ' -dimethoxybenzidine, 2 ' -dihydroxybenzidine, 3 ' -dihydroxybenzidine, 2 ' -difluorobenzidine, 3 ' -difluorobenzidine, 2,3 ' -dihydroxybenzidine, 2 ' -difluorobenzidine, 3 ' -difluorobenzidine, 2,3 ' -difluorobenzidine, 2 ' -dichlorobenzidine, 3 ' -dichlorobenzidine, 2,3 ' -dichlorobenzidine, 4 ' -diaminobenzanilide, 4-aminophenyl-4 ' -aminobenzoate, octafluorobenzidine, 2 ', 5,5 ' -tetramethylbenzidine, 3 ', 5,5 ' -tetramethylbenzidine, 2 ', 5,5 ' -tetrakis (trifluoromethyl) benzidine, 3 ', 5,5 ' -tetrakis (trifluoromethyl) benzidine, 2 ', 5,5 ' -tetrachlorobenzidine, 4 ' -bis (4-aminophenoxy) biphenyl, 4 ' -bis (3-aminophenoxy) biphenyl, 4 ' - { [3,3 "-bis (trifluoromethyl) - (1, 1': aromatic diamines such as 3 ', 1 "-terphenyl) -4, 4" -diyl ] -bis (oxy) } diphenylamine, 4' - { [ (perfluoropropane-2, 2-diyl) bis (4, 1-phenylene) ] bis (oxy) } diphenylamine, and 1- (4-aminophenyl) -2, 3-dihydro-1, 3, 3-trimethyl-1H-indene-5 (or 6) amine; 4,4 '-methylenebis (cyclohexylamine), 4' -methylenebis (3-methylcyclohexylamine), isophoronediamine, trans-1, 4-cyclohexanediamine, cis-1, 4-cyclohexanediamine, 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-bis (4-aminocyclohexyl) propane, 2-bis (4-aminocyclohexyl) hexafluoropropane, 1, 3-propanediamine, 1, 4-butanediamine, 1, 5-pentanediamine, 1, 6-hexanediamine, Aliphatic diamines such as 1, 7-heptanediamine, 1, 8-octanediamine and 1, 9-nonanediamine, but are not limited thereto.

Among them, preferred is an aromatic diamine in which B in the formula (6) is a 2-valent group represented by any one of the formulae (B-1) to (B-11), that is, 2 ' -bis (trifluoromethoxy) - (1,1 ' -biphenyl) -4,4 ' -diamine [ otherwise known as: 2,2 ' -dimethoxybenzidine ], 4 ' - (perfluoropropane-2, 2-diyl) diphenylamine, 2, 5-bis (trifluoromethyl) benzene-1, 4-diamine, 2-fluorobenzene-1, 4-diamine, 4 ' -oxybis [3- (trifluoromethyl) aniline ], 2 ', 3,3 ', 5,5 ', 6,6 ' -octafluoro [1,1 ' -biphenyl ] -4,4 ' -diamine [ otherwise known as: octafluorobenzidine ], 2,3,5, 6-tetrafluorobenzene-1, 4-diamine, 4 ' - { [3,3 ' -bis (trifluoromethyl) - (1,1 ': 3 ', 1 ' -terphenyl) -4,4 ' -diyl ] -bis (oxy) } diphenylamine, 4 ' - { [ (perfluoropropane-2, 2-diyl) bis (4, 1-phenylene) ] bis (oxy) } diphenylamine, 1- (4-aminophenyl) -2, 3-dihydro-1, 3, 3-trimethyl-1H-indene-5 (or 6) amine are preferred diamines.

The content of the polyimide is usually 10 mass% or more, preferably 20 mass% or more, and more preferably 25 mass% or more based on the total mass of the solid components of the composition for forming a flexible device substrate, from the viewpoint of the mechanical strength of the formed film, and is from the viewpoint of the optical characteristics (retardation in the thickness direction (R) of the low-retardation film_th) And a coefficient of linear expansion (CTE) is not lowered), usually 80 mass% or less, preferably 75 mass% or less, and more preferably 70 mass% or less. The solid component is a component remaining after removing 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 obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component containing an alicyclic tetracarboxylic dianhydride represented by the formula (C1) with a diamine component containing a fluorine-containing aromatic diamine represented by the formula (a 1).

The reaction to obtain polyamic acid from the above two components can be carried out relatively easily in an organic solvent, and is advantageous in that no by-product is produced.

The addition 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 the subsequent imidization, but the tetracarboxylic dianhydride component may be generally about 0.8 to 1.2, for example about 0.9 to 1.1, and preferably about 0.95 to 1.02, relative to the diamine component 1. Similarly to the ordinary 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 of the tetracarboxylic dianhydride component and the diamine component is not particularly limited as long as it does not adversely affect the reaction and the polyamic acid produced can be dissolved. Specific examples thereof are given below.

Examples thereof include m-cresol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N-dimethylformamide, N-dimethylacetamide, 3-methoxy-N, N-dimethylpropionamide, 3-ethoxy-N, N-dimethylpropionamide, 3-propoxy-N, N-dimethylpropionamide, 3-isopropoxy-N, N-dimethylpropionamide, 3-butoxy-N, N-dimethylpropionamide, 3-sec-butoxy-N, N-dimethylpropionamide, 3-tert-butoxy-N, N-dimethylpropionamide, N-ethylpropionamide, N-propylpropionic amide, N-propylpropionic amide, and their salts, Gamma-butyrolactone, N-methylcaprolactam, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethylsulfoxide, isopropanol, 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 monoacetate, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol monoacetate, propylene glycol monomethyl ether, propylene glycol tert-butyl ether, dipropylene glycol monomethyl ether, diethylene glycol monoacetate, diethylene glycol dimethyl ether, dipropylene glycol monoacetate monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoacetate monoethyl ether, isopropyl alcohol, methyl alcohol, and ethyl alcohol, 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, butyl butyrate, butyl ether, diisobutyl ketone, methylcyclohexene, propyl ether, dihexyl ether

Alkane, 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 ether acetate, methyl pyruvate, ethyl pyruvate, methyl 3-methoxypropionate, methyl ethyl 3-ethoxypropionate, ethyl 3-methoxypropionate3-ethoxypropionic acid, 3-methoxypropionic acid propyl ester, 3-methoxypropionic acid butyl ester, diglyme, 4-hydroxy-4-methyl-2-pentanone, etc., but are not limited thereto. These may be used alone or in combination of 2 or more.

Further, even in the case of a solvent which does not dissolve the polyamic acid, the solvent may be mixed and used within a range where the produced polyamic acid does not precipitate. Further, since the water content in the organic solvent causes inhibition of the polymerization reaction and hydrolysis of the produced polyamic acid, it is preferable to use an organic solvent dehydrated and dried as much as possible.

Examples of the method of reacting the tetracarboxylic dianhydride component and the diamine component in the organic solvent include a method of stirring a dispersion or solution obtained by dispersing or dissolving the diamine component in the organic solvent, and adding the tetracarboxylic dianhydride component directly thereto or a dispersion or solution obtained by dispersing or dissolving the component in the organic solvent; on the contrary, a method of adding a diamine component to a dispersion or solution obtained by dispersing or dissolving a tetracarboxylic dianhydride component in an organic solvent; and a method of alternately adding the tetracarboxylic dianhydride component and the diamine compound component, and the method is not limited to these methods as long as the target polyamic acid can be obtained.

In the case where the tetracarboxylic dianhydride component and/or the diamine component is composed of a plurality of compounds, they may be reacted in a state of being mixed in advance, or they may be reacted in sequence separately, or low-molecular-weight materials obtained by the separate reactions may be mixed and reacted to obtain high-molecular-weight materials.

The temperature for the synthesis of the polyamic acid may be set as appropriate within the range from the melting point to the boiling point of the solvent used, and may be any temperature, for example, from-20 ℃ to 150 ℃, but is from-5 ℃ to 100 ℃, usually from about 0 ℃ to 100 ℃, and preferably from about 0 ℃ to 70 ℃.

The reaction time depends on the reaction temperature and the reactivity of the raw material, and therefore cannot be generally specified, but is usually about 1 to 100 hours.

The reaction may be carried out at any concentration of the raw materials, but if the concentration is too low, it is difficult to obtain polyamic acid having a high molecular weight, and if the concentration is too high, the viscosity of the reaction solution is too high to stir uniformly, and 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. If necessary, the reaction may be carried out at a high concentration at the initial stage of the reaction, and then an organic solvent may be added.

Imidization 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 imidization in which a catalyst is added to a solution of the polyamic acid.

The temperature for thermal imidization of polyamic acid in a solution is preferably 100 to 400 ℃, more preferably 120 to 250 ℃, and is preferably performed while removing water produced by the imidization reaction from the system.

The chemical (catalytic) imidization of the polyamic acid can be carried out by adding a basic catalyst and an acid anhydride to a solution of the polyamic acid and stirring the inside of the system at a temperature of-20 to 250 ℃ and preferably 0 to 180 ℃.

The amount of the basic catalyst is 0.5 to 30 mol times, preferably 1.5 to 20 mol times, and the amount of the acid anhydride is 1 to 50 mol times, preferably 2 to 30 mol times, of the amic acid group of the polyamic acid.

Examples of the basic catalyst include amines such as pyridine, triethylamine, trimethylamine, tributylamine, trioctylamine, and 1-ethylpiperidine, and pyridine is preferable because pyridine has an appropriate basic group for the reaction to proceed.

Examples of the acid anhydride include aliphatic carboxylic acid anhydrides such as acetic anhydride, and aromatic carboxylic acid anhydrides such as trimellitic anhydride and pyromellitic anhydride, and among these, acetic anhydride is preferable because purification after completion of the reaction is easy.

The imidization rate of the catalyst imidization can be controlled by adjusting the amount of the catalyst, the reaction temperature and the reaction time.

In the polyimide used in the present invention, the dehydration ring-closing ratio (imidization ratio) of the amic acid group does not need to be 100%, and can be arbitrarily adjusted and used according to the application and purpose. Particularly preferably 50% or more.

In the present invention, the reaction solution may be filtered and the filtrate may be used as it is, or diluted or concentrated to incorporate titanium dioxide, silicon dioxide, or the like described later therein to prepare a composition for forming a flexible device substrate. When the resin film is filtered in this way, the composition for forming a flexible device substrate can be obtained efficiently while reducing the mixing of impurities which may cause deterioration in heat resistance, flexibility, and linear expansion coefficient characteristics of the obtained resin film.

In addition, the polyimide used in the present invention preferably has a weight average molecular weight (Mw) of 5,000 to 200,000 in terms of polystyrene in Gel Permeation Chromatography (GPC) in consideration of strength of a resin film, handling properties when forming a resin film, uniformity of a resin film, and the like.

Polymer recovery

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 the polymer component. Examples of the poor solvent used for precipitation include methanol, acetone, hexane, butyl cellosolve, heptane, methyl ethyl ketone, methyl isobutyl ketone, ethanol, toluene, benzene, isopropanol, and water. The polymer precipitated by charging into the poor solvent may be recovered by filtration, and then dried at normal temperature or under reduced pressure or by heating.

Further, if the operation of re-dissolving the polymer recovered by precipitation in an organic solvent and recovering the polymer by re-precipitation is repeated 2 to 10 times, impurities in the polymer can be reduced. In this case, if 3 or more kinds of poor solvents such as alcohols, ketones, hydrocarbons and the like are used, the purification efficiency is further improved, which is preferable.

The organic solvent for dissolving the resin component in the reprecipitation recovery step is not particularly limited. Specific examples thereof include N, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, N-methylcaprolactam, 2-pyrrolidone, N-ethylpyrrolidone, N-vinylpyrrolidone, dimethyl sulfoxide, tetramethylurea, pyridine, dimethyl sulfone, hexamethylsulfoxide, γ -butyrolactone, 1, 3-dimethylimidazolidinone, dipentene, ethylpentyl ketone, methylnonyl ketone, methylethyl ketone, methylisoamyl ketone, methylisopropyl ketone, cyclohexanone, ethylene carbonate, propylene carbonate, diglyme, 4-hydroxy-4-methyl-2-pentanone and the like. These solvents may be used in combination of 2 or more.

[ titanium dioxide ]

The titanium dioxide (titania) used in the present invention is not particularly limited, and particles having a particle diameter of, for example, 3nm to 200nm, preferably 3nm to 50nm, and more preferably 3nm to 20nm can be suitably used as the titanium dioxide in the form of particles. By using titanium dioxide particles having a particle diameter in such a numerical range, substrate peeling by the laser peeling method can be performed with higher accuracy and higher reproducibility.

In the present invention, the particle diameter of the titania particles is represented by a primary particle diameter obtained by observing titania particles in a titania sol described later with an electron microscope.

The titanium dioxide may have any crystal structure of anatase type, rutile type, anatase-rutile mixed type, and brookite type, but among them, rutile type is preferably contained.

In particular, in the present invention, the titania-based colloidal particles (colloidal titania) having the above-described particle size value can be suitably used, and a titania sol can be used as the colloidal titania.

The titania-based colloidal particles used in the present invention may be colloidal particles alone, or may be colloidal particles of a composite oxide or a mixture of the titania-based colloidal particles and another high-refractive-index metal oxide, which will be described later.

The method for producing the titanium dioxide-based colloidal particles is not particularly limited, and the titanium dioxide-based colloidal particles can be produced by a conventional method, for example, 1) an ion exchange method, 2) a peptization 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-type anion exchange resin.

2) A gel releasing method: examples thereof include a method in which an acidic salt of titanium is neutralized with a salt, or a gel obtained by neutralizing a basic salt of titanium with an acid is washed and then peptized with an acid or an alkali (Japanese patent publication No. 4-27168), a method in which an alkoxide of titanium is hydrolyzed (Japanese patent application laid-open No. 2003-176120), and a method in which a basic salt of titanium is hydrolyzed under heating (Japanese patent application laid-open No. 10-245224).

Examples of the other metal oxides include Fe₂O₃、ZrO₂、SnO₂、Ta₂O₅、Nb₂O₅、Y₂O₃、MoO₃、WO₃、PbO、In₂O₃、Bi₂O₃And SrO, and the like, and they can be produced in the same manner as the titania-based colloidal particles. Further, TiO is exemplified as the composite oxide₂-SnO₂、TiO₂-ZrO₂、TiO₂-ZrO₂-SnO₂、TiO₂-ZrO₂-CeO₂For example, the methods disclosed in, for example, Japanese patent application laid-open Nos. 2014-38293, 2001-122621, and 2000-063119 can be employed as the method for forming a composite.

Examples of the organic solvent in the titania sol include lower alcohols such as methanol, ethanol, and isopropanol; linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide; cyclic amides such as N-methyl-2-pyrrolidone; ethers such as γ -butyrolactone; ethyl cellosolve, glycols such as ethylene glycol, acetonitrile, and the like.

The viscosity of the titania sol is about 0.6 mPas to 100 mPas at 20 ℃.

Examples of commercially available products of the titanium dioxide-based colloidal particles (titanium dioxide sol) include,

trade name of neutral titanium dioxide sol TTO-W-5 (aqueous sol of rutile-type ultrafine titanium oxide, silica surface treatment, manufactured by Shikoku industries Co., Ltd.), trade name of TKS-201 (anatase-type acid sol, manufactured by テイカ Co., Ltd.), trade name of KS-202 (anatase-type acid sol, manufactured by テイカ Co., Ltd.), trade name of TKS-203 (anatase-type neutral sol, manufactured by テイカ Co., Ltd.), trade name of CSB (anatase-type aqueous acid sol, manufactured by Sakai chemical industries, Ltd.), trade name of CSB-M (anatase-type aqueous neutral sol, manufactured by Sakai chemical industries, Ltd.), trade name of DC-Ti, DCN-Ti, DCB-Ti (amorphous aqueous sol, manufactured by Fuji- チタン industries, Ltd.), organic sol (anatase, solvent: ethylene glycol, toluene-IPA manufactured by Fuji チタン industries (Ltd.), trade name of QUEEN TITANIC series (aqueous colloid, manufactured by Nissan catalytic conversion Co., Ltd.), trade name of OPTALAKE series (non-aqueous colloid, manufactured by Nissan catalytic conversion Co., Ltd.), trade name of サンコロイド (registered trademark) HT-R350M7-20 (manufactured by Nissan chemical industries, Ltd.), and the like.

The titania sol can be produced by dispersing titania particles in an organic solvent according to a general method.

Examples of such an organic solvent include the same organic solvents as those mentioned above.

Examples of commercially available products of titanium dioxide particles include TiO (registered trademark) under the trade name AEROXIDE₂P25 (manufactured by Nippon アエロジル Co., Ltd.).

The content of the titanium dioxide is usually 0.1 mass% or more, preferably 1 mass% or more, and more preferably 2 mass% or more, with respect to the total mass of the polyimide, the titanium dioxide particles and the silica particles in the composition for forming a flexible device substrate, from the viewpoint of ensuring absorption of light having a wavelength of 308nm, and is usually 30 mass% or less, preferably 25 mass% or less, and more preferably 20 mass% or less, from the viewpoint of obtaining a film having excellent transparency in the visible light region with good reproducibility.

In the composition for forming a flexible device substrate of the present invention, when the crosslinking agent described later is contained, the content of the titanium dioxide is preferably 3 to 16% by mass based on the total mass of the polyimide, the titanium dioxide particles and the silica particles in the composition for forming a flexible device substrate.

[ silica ]

The silica (silica) used in the present invention is not particularly limited, and the silica in the form of particles has an average particle diameter of, for example, 100nm or less, preferably 5nm to 100nm, more preferably 5nm to 55nm, and is preferably 5nm to 50nm, more preferably 5nm to 45nm, even more preferably 5nm to 35nm, and even more preferably 5nm to 30nm, from the viewpoint of obtaining a further highly transparent thin film with good reproducibility.

In the present invention, the average particle diameter of the silica particles is an average particle diameter value calculated from a specific surface area value measured by a nitrogen adsorption method using the silica particles.

In particular, in the present invention, colloidal silica having the above-mentioned average particle size value can be suitably used, and as the colloidal silica, a 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 organic silica sol obtained by replacing water as a dispersion medium of the aqueous silica sol with an organic solvent can be used.

Further, a silica sol obtained by hydrolyzing and condensing an alkoxysilane such as methyl silicate or ethyl silicate 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 organic silica sol obtained by replacing the silica sol solvent with another organic solvent may be used. The substitution can be carried out by a usual method such as distillation or ultrafiltration.

Among them, the organic silica sol in which the dispersion medium is an organic solvent is preferably used in the present invention.

Examples of the organic solvent in the organic silica sol include lower alcohols such as methanol, ethanol, and isopropanol; linear amides such as N, N-dimethylformamide and N, N-dimethylacetamide; cyclic amides such as N-methyl-2-pyrrolidone; ethers such as γ -butyrolactone; ethyl cellosolve, glycols such as ethylene glycol, acetonitrile, and the like.

The viscosity of the organic silica sol is about 0.6 mPas-100 mPas at 20 ℃.

Examples of the commercially available product of the organic silica sol include, for example, a product name of MA-ST-S (methanol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of MT-ST (methanol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of MA-ST-UP (methanol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of MA-ST-M (methanol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of MA-ST-L (methanol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of IPA-ST-S (isopropyl alcohol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), a product name of IPA-ST (isopropyl alcohol-dispersed silica sol, manufactured by Nissan chemical industry Co., Ltd.), the trade name IPA-ST-UP (isopropyl alcohol-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), the trade name IPA-ST-L (isopropyl alcohol-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), the trade name IPA-ST-ZL (isopropyl alcohol-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), the trade name NPC-ST-30 (n-propyl cellosolve-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), the trade name PGM-ST (1-methoxy-2-propanol-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), the trade name DMAC-ST (dimethylacetamide-dispersed silica sol manufactured by Nissan chemical industry Co., Ltd.), and the trade name XBA-ST (xylene-n-butanol mixed solvent-dispersed silica sol), manufactured by Nissan chemical industries, Ltd.), the trade name EAC-ST (Ethyl acetate dispersed silica sol manufactured by Nissan chemical industries, Ltd.), the trade name PMA-ST (propylene glycol monomethyl ether acetate dispersed silica sol manufactured by Nissan chemical industries, Ltd.), the trade name MEK-ST (methyl ethyl ketone dispersed silica sol manufactured by Nissan chemical industries, Ltd.), the trade name MEK-ST-UP (methyl ethyl ketone dispersed silica sol manufactured by Nissan chemical industries, Ltd.), the trade name MEK-ST-L (methyl ethyl ketone dispersed silica sol manufactured by Nissan chemical industries, Ltd.), and the trade name MIBK-ST (methyl isobutyl ketone dispersed silica sol manufactured by Nissan chemical industries, Ltd.), and the like, but are not limited thereto.

In the present invention, two or more kinds of silica such as those exemplified above as silica used as the silica, for example, as the organic silica sol, may be used in combination.

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

[ crosslinking agent ]

The composition for forming a flexible device substrate of the present invention may further comprise a crosslinking agent, and the crosslinking agent used herein may comprise a compound having a ring structure and having 2 or more groups selected from a hydroxyl group, an epoxy group, and an alkoxy group having 1 to 5 carbon atoms, and being composed of only a hydrogen atom, a carbon atom, a nitrogen atom, and an oxygen atom. By using such a crosslinking agent, a composition for forming a flexible device substrate, which has excellent solvent resistance and is suitable for a flexible device substrate, can be obtained with good reproducibility, and which has further improved storage stability.

Among these, the total number of hydroxyl groups, epoxy groups, and alkoxy groups having 1 to 5 carbon atoms per compound in the crosslinking agent is preferably 3 or more from the viewpoint of achieving solvent resistance of the obtained resin film with good reproducibility, and is preferably 10 or less, more preferably 8 or less, and still more preferably 6 or less from the viewpoint of achieving flexibility of the obtained resin film with good reproducibility.

Specific examples of the ring structure of the crosslinking agent include aromatic rings such as benzene, heteroaromatic rings containing a nitrogen atom such as pyridine, pyrazine, pyrimidine, pyridazine and 1,3, 5-triazine, cycloalkane rings such as cyclopentane, cyclohexane and cycloheptane, and cyclic amines such as piperidine, piperazine, hexahydropyrimidine, hexahydropyridazine and hexahydro-1, 3, 5-triazine.

The number of ring structures per compound in the crosslinking agent is not particularly limited as long as it is 1 or more, but is preferably 1 or 2 from the viewpoint of ensuring solubility of the crosslinking agent in a solvent and obtaining a resin film having high flatness.

When the number of the ring structures is 2 or more, the ring structures may be condensed with each other, or may be bonded to each other via a linking group such as an alkane-diyl group having 1 to 5 carbon atoms such as a methylene group, an ethylene group, a1, 3-propylene group, a propane-2, 2-diyl group, or the like.

The molecular weight of the crosslinking agent is not particularly limited as long as it has crosslinking ability and dissolves in the solvent used, but is preferably about 100 to 500, more preferably about 150 to 400, in consideration of solvent resistance of the obtained resin film, solubility of the crosslinking agent itself in an organic solvent, availability, price, and the like.

The crosslinking agent may further have a group which a ketone group, an ester group (bond), or the like may be derived from a hydrogen atom, a carbon atom, a nitrogen atom, and an oxygen atom.

Preferable examples of the crosslinking agent include compounds represented by formulae selected from the following formulae (K1) to (K5), one preferable embodiment of formula (K4) includes a compound represented by formula (K4-1), and one preferable embodiment of formula (K5) includes a compound represented by formula (5-1).

In the above formula, each A¹And A²Independently represent an alkane-diyl group having 1 to 5 carbon atoms such as a methylene group, an ethylene group, a1, 3-propylene group, a propane-2, 2-diyl group and the like, wherein A represents¹Preferably methylene or ethylene, more preferably methylene, as A²Methylene and propane-2, 2-diyl are preferred.

Each X independently represents an alkoxy group having 1 to 5 carbon atoms such as a hydroxyl 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, or a tert-butyloxy group.

Among them, in view of availability, price, and the like of the crosslinking agent, X is preferably an epoxy group in the formulae (K1) and (K5), an alkoxy group having 1 to 5 carbon atoms in the formulae (K2) and (K3), and a hydroxyl group in the formula (K4).

In the formula (K4), each n represents- (A) bonded to a benzene ring¹The number of the groups-X) is an integer of 1 to 5 independently of each other, but is preferably 2 to 3, more preferably 3.

Among the compounds, each A is preferred¹All are the same group, and preferably each X is all the same group.

The compounds represented by the above formulae (K1) to (K5) can be obtained by: the compound having a structure similar to that of the aryl compound, heteroaryl compound, cyclic amine, etc. in each of these compounds is reacted with an epoxy alkyl halide compound, alkoxy halide compound, etc. by a carbon-carbon coupling reaction or an N-alkylation reaction, or the alkoxy moiety of the product is hydrolyzed.

The crosslinking agent may be a commercially available product or a synthesized product synthesized by a known synthesis method.

Commercially available products include CYMEL (registered trademark) 300, CYMEL 301, CYMEL 303LF, CYMEL 303ULF, CYMEL 304, CYMEL 350, CYMEL 3745, CYMEL XW3106, CYMEL MM-100, CYMEL 323, CYMEL 325, CYMEL 327, CYMEL 328, CYMEL 385, CYMEL 370, CYMEL 373, CYMEL 380, CYMEL 1116, CYMEL 1130, CYMEL 1133, CYMEL 1141, CYMEL 1161, CYMEL 1168, CYMEL 3020, CYMEL 202, CYMEL 203, CYMEL 1156, CYMEL MB-94, CYMEL MB-96, CYMEL MB-98, CYMEL 247-10, CYMEL 651, CYMEL 658, CYMEL 683, CYMEL 688, CYMEL 8, CYMEL 11514, CYMEL MI-MI 65, CYMEL MI 80, CYMEL MI 80, CYMEL IX-5, CYMEL-5, CYMEL-5, CYMEL-5, CYMEL-6, CYMEL, CYME, CYMEL U-216-8, CYMEL U-227-8, CYMEL U-1050-10, CYMEL U-1052-8, CYMEL U-1054, CYMEL U-610, CYMEL U-640, CYMEL UB-24-BX, CYMEL UB-26-BX, CYMEL UB-90-BX, CYMEL UB-25-BE, CYMEL UB-30-B, CYMEL U-662, CYMEL U-663, CYMEL U-1051, CYMEL UI-19-I, CYMEL UI-19-IE, CYMEL UI-21-E, CYMEL UI-27-IE, CYMEL U-38-I, CYMEL UI-20-E, CYMEL 659-112659, CYMEL 5013, CYMEL1125, CYMEL 1170, CYMEL 1172, CYMEL 3041, CYMEL NF2000 and the like (more than or less than CYMEL) can BE used, manufactured by allnex corporation); TEPIC (registered trademark) V, TEPIC S, TEPIC HP, TEPIC L, TEPIC PAS, TEPIC VL, TEPIC UC (manufactured by Nissan chemical industry Co., Ltd.), TM-BIP-A (manufactured by Asahi organic materials Co., Ltd.), 1,3,4, 6-tetrakis (methoxymethyl) glycoluril (hereinafter abbreviated as TMG) (manufactured by Tokyo chemical industry Co., Ltd.), 4' -methylenebis (N, N-diglycidylaniline) (manufactured by Aldrich Co., Ltd.), 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 strain), TG-G (four kingdom Industrial Co., Ltd.), and the like.

Specific examples of preferred crosslinking agents are given below, but the crosslinking agents are not limited thereto.

The amount of the crosslinking agent to be blended is appropriately determined depending on the kind of the crosslinking agent, and therefore cannot be generally specified, and is usually 50 mass% or less, preferably 100 mass% or less, and 0.1 mass% or more, preferably 1 mass% or more, with respect to the total mass of the polyimide, the titanium dioxide and the silica, from the viewpoint of ensuring the flexibility and suppressing the brittleness of the obtained resin film, and from the viewpoint of ensuring the solvent resistance of the obtained resin film.

[ 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, silicon dioxide, and if necessary, a crosslinking agent. The organic solvent is not particularly limited, and examples thereof include the same ones as those of the reaction solvent used for preparing the polyamic acid and the polyimide. More specifically, N-dimethylformamide, N-dimethylacetamide, N-methyl-2-pyrrolidone, 1, 3-dimethyl-2-imidazolidinone, N-ethyl-2-pyrrolidone, γ -butyrolactone, and the like can be given. The organic solvent may be used alone in 1 kind, or may be used in combination in 2 or more kinds.

Among them, N-dimethylacetamide, N-methyl-2-pyrrolidone, and γ -butyrolactone are preferable if a resin film having high flatness is obtained with good reproducibility.

[ composition for Forming Flexible device substrate ]

The present invention is a composition for forming a flexible device substrate, which contains the above polyimide, titanium dioxide, silica, an organic solvent, and, if necessary, a crosslinking agent. Here, the composition for forming a flexible device substrate of the present invention is uniform, and no phase separation is observed.

In the composition for forming a flexible device substrate according to the present invention, the mixing ratio of the polyimide to the silica is preferably, in terms of mass ratio, a ratio of polyimide: silica 10: 1-1: 10, more preferably 8: 2-2: 8, e.g. 7: 3-3: 7.

the amount of solids in the composition for forming a flexible device substrate of the present invention is usually in the range of 0.5 to 30 mass%, but is preferably 5 mass% or more and 20 mass% or less from the viewpoint of film uniformity. The solid component is a component remaining after removing 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 film to be produced, and the like, and is usually 1 to 50,000mPa · s at 25 ℃.

In the composition for forming a flexible device substrate of the present invention, various organic or inorganic low-molecular or high-molecular compounds may be blended in order to impart processing characteristics and various functionalities. For example, catalysts, defoaming agents, leveling agents, surfactants, dyes, plasticizers, fine particles, coupling agents, sensitizers, and the like may be used. For example, the catalyst may be added for the purpose of reducing the retardation and linear expansion coefficient of the resin film.

The composition for forming a flexible device substrate of the present invention may be obtained by dissolving the polyimide obtained by the above method, titanium dioxide, silicon dioxide, and if necessary, a crosslinking agent in the organic solvent, or may be prepared by adding titanium dioxide, silicon dioxide, and if necessary, a crosslinking agent to a reaction solution after preparing a polyimide, and if necessary, further adding the organic solvent.

[ Flexible device substrate ]

The above-described composition for forming a flexible device substrate of the present invention is applied to a substrate, dried and heated to remove an organic solvent, and a resin film, that is, a flexible device substrate, having high heat resistance, high transparency, appropriate flexibility, an appropriate linear expansion coefficient, a small retardation, and capable of selectively absorbing light having a wavelength of 308nm can be obtained.

The present invention also provides a flexible device substrate comprising the polyimide, the titanium dioxide, the silicon dioxide, and, if necessary, a crosslinking agent, and a cured product of the composition for forming a flexible device substrate of the present invention.

Examples of the substrate used for manufacturing the flexible device substrate (resin film) include plastics (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy resin, melamine, triacetyl cellulose, ABS, AS, norbornene resin, etc.), metals, stainless steel (SUS), wood, paper, glass, silicon wafers, slates, and the like.

In particular, when applied as a flexible device substrate, the substrate to be applied is preferably glass or a silicon wafer from the viewpoint that existing equipment can be used, and further preferably glass from the viewpoint that the resulting flexible device substrate exhibits good peelability. The linear expansion coefficient of the substrate to be used is preferably 40 ppm/DEG C or less, and more preferably 30 ppm/DEG C or less, from the viewpoint of warpage of the substrate after coating.

The method for applying the composition for forming a flexible device substrate to a base material is not particularly limited, and examples thereof include a cast coating method, a spin coating method, a blade coating method, a dip coating method, a roll coating method, a bar coating method, a die coating method, an ink jet method, a printing method (relief printing, gravure printing, offset printing, screen printing, etc.), and the like, and these methods can be appropriately used according to the purpose.

The heating temperature is preferably 300 ℃ or lower. If the temperature exceeds 300 ℃, the resulting resin film may become brittle, and a resin film suitable for use as a display substrate cannot be obtained in particular.

In addition, considering the heat resistance and linear expansion coefficient characteristics of the resin film obtained, it is desirable that the coated composition for forming a flexible device substrate is heated at 40 to 100 ℃ for 5 minutes to 2 hours, then the heating temperature is directly raised stepwise, and finally the composition is heated at more than 175 ℃ and 280 ℃ or less for 30 minutes to 2 hours. In this way, by heating at a temperature of 2 or more stages, i.e., a stage of drying the solvent and a stage of promoting molecular orientation, the low thermal expansion characteristic can be expressed with good reproducibility.

It is particularly preferable that the coated composition for forming a flexible device substrate is heated at 40 to 100 ℃ for 5 minutes to 2 hours, then at more than 100 ℃ and 175 ℃ or less for 5 minutes to 2 hours, and then at more than 175 ℃ and 280 ℃ or less for 5 minutes to 2 hours.

Examples of the heating device include an electric hot plate and an oven. The heating atmosphere may be under air, an inert gas such as nitrogen, or under normal pressure or reduced pressure, or different pressures may be applied at each stage of heating.

The thickness of the resin film is appropriately determined in consideration of the type of flexible device within a range of about 1 to 200 μm, but when the resin film is used as a substrate for a flexible display in particular, the thickness is usually about 1 to 60 μm, preferably about 5 to 50 μm, and the thickness of the coating film before heating is adjusted to form a resin film having a desired thickness.

The method of peeling the resin film formed in this way from the substrate is not particularly limited, and examples thereof include a method of cooling the resin film together with the substrate to introduce cracks into the film and peeling the film, and a method of peeling the film by applying tension via a roller.

In particular, in the present invention, as a method for peeling the resin film from the substrate, a Laser Lift Off (LLO) method can be used. That is, by irradiating the substrate with light having a wavelength of 308nm from the surface of the substrate opposite to the surface on which the resin film is formed, the light having the wavelength is transmitted through the substrate (for example, a glass carrier), and only the polyimide in the vicinity of the substrate absorbs the light, and the polyimide in the portion is evaporated, whereby the resin film can be peeled from the substrate.

The laser used for peeling the resin film from the substrate by the laser peeling method is not particularly limited, but is preferably an excimer laser, and specifically, examples of the oscillation wavelength include ArF (193nm), KrF (248nm), XeCl (308nm), XeF (353nm), and the like, and XeCl (308nm) is particularly preferable.

In addition, the energy density of the laser light to be irradiated is usually less than 650mJ/cm²Examples of the range of (1) include, for example, 500mJ/cm²～530mJ/cm²In the range of 500mJ/cm²～515mJ/cm²And the like.

The resin film according to a preferred embodiment of the present invention obtained in this way 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 308nm becomes 5% or less, that is, sufficient light absorption at the wavelength can be achieved by peeling the resin film from the substrate by the laser peeling method.

Further, the resin film can have a linear expansion coefficient of 40 ppm/DEG C or less, particularly 10 ppm/DEG C to 35 ppm/DEG C, at 30 to 220 ℃, for example, and is excellent in dimensional stability when heated.

Further, the resin film has a characteristic of in-plane retardation R₀And a thickness direction retardation R_thAre all very small, the in-plane retardation R₀Expressed by the product of birefringence (difference in-plane orthogonal 2 refractive indices) and film thickness when the wavelength of incident light is 590 nm; retardation in the thickness direction R_thBy making 2 birefringence when viewed from a cross section in the thickness direction(differences between the respective in-plane 2 refractive indices and the refractive index in the thickness direction) are expressed as the average of the 2 phase differences obtained by multiplying the film thicknesses. The retardation R in the thickness direction of the resin thin film is about 15 to 40 μm in average thickness_thLess than 700nm, for example 450nm or less, for example 1 to 410nm, in-plane retardation R₀Less than 4.5, for example, 0.1 to 4.2, and a birefringence Δ n of less than 0.015, for example, 0.0028 to 0.0144, have very low values.

The resin thin film described above has the above-described characteristics, and therefore satisfies various conditions required as a base film for a flexible device substrate, and can be suitably used as a base film for a flexible device, particularly a substrate for a flexible display.

Examples

The present invention will be described in further detail below with reference to examples, but the present invention is not limited thereto. Further, the abbreviations of the reagents used and the devices and conditions used therefor are as follows.

< determination of number average molecular weight (Mn) and weight average molecular weight (Mw) >)

The device comprises the following steps: showdex GPC-101 manufactured by Showdex Denko K.K

Column: KD803 and KD805

Column temperature: 50 deg.C

Eluting solvent: DMF, flow rate: 1.5 ml/min

Standard 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: gamma-butyrolactone

[ example of Synthesis of polyimide (I) (preparation of polyimide solution (PI) ]

Into a three-necked reaction flask having a nitrogen gas inlet/outlet port and equipped with a dean-Stark apparatus and a mechanical stirrer were charged TFMB 11.208g (0.035mol) and gamma-butyrolactone (GBL)66.56g, and stirring was started and the temperature was raised to 90 ℃. After the diamine (TFMB) was completely dissolved in the solvent, 4.376g (0.0175mol) of BODAxx and 14.26g of GBL were added, and the mixture was heated at 140 ℃ for 10 minutes under a nitrogen atmosphere. Then, 3.432g (0.0175mol) of CBDA and 14.26g of GBL (. gamma. -butyrolactone) were added, and the reaction was carried out for 10 minutes under a nitrogen atmosphere. 0.152g of 1-ethylpiperidine was added to the reaction mixture, and the temperature was raised to 180 ℃ for 7 hours. GBL 86.02g was added to the reaction mixture, and the mixture was diluted so that the solid content concentration (concentration of the component after removal of the organic solvent) became 10.5 mass%, to obtain a target polyimide solution (PI) (molecular weight of polyimide (I): Mw 169,385, Mn 54,760).

[ preparation example of titanium dioxide Sol (TiO)₂-GBL)]

A1000 mL round-bottom flask was charged with a methanol-dispersed titanium dioxide sol prepared by Nissan chemical industries, Ltd: TiO 2₂91.13g of MeOH ("サンコロイド (registered trademark) HT-R305M 7-20", rutile type, titanium dioxide solid content: 30.6% by mass) and 82.02g of gamma-butyrolactone. Further, the flask was connected to a vacuum evaporator, the pressure in the flask was reduced, and the flask was immersed in a warm water bath at about 35 ℃ for 60 minutes to obtain a titanium dioxide sol (TiO) in which the solvent was replaced from methanol to γ -butyrolactone₂GBL) about 107.0g (titanium dioxide solid content concentration: 26.06 mass%).

In the titania sol, the primary particle diameter of the titania particles observed by an electron microscope is 10 to 12 nm.

[ preparation example of silica Sol (GBL-M) ]

A1000 mL round-bottomed flask was charged with 350g of a methanol-dispersed silica sol manufactured by Nissan chemical industries, Ltd: MA-ST-M (silica solid content concentration: 40.4% by mass) and 419g of gamma-butyrolactone. Further, the flask was connected to a vacuum evaporator, the pressure in the flask was reduced, and the flask was immersed in a warm water bath at about 35 ℃ for 20 to 50 minutes to obtain about 560.3g (silica solid content concentration: 25.25 mass%) of a silica sol (GBL-M) in which the solvent was replaced from methanol to γ -butyrolactone.

In the silica sol, the average particle diameter calculated from the specific surface area value measured by a nitrogen adsorption method was 22 nm. Specifically, the specific surface area of the dried powder of the silica sol was measured using a specific surface area measuring apparatus モノソーブ MS-16 manufactured by ユアサアイオニクス Co., Ltd, and the measured specific surface area S (m) was used²(g), the average primary particle diameter was calculated by the formula d (nm) 2720/S.

[ preparation of composition for Forming Flexible device substrate ]

[ example 1]

0.9703g of GBL-M silica sol (silica solid content concentration: 25.25 mass%) and 0.946g of GBL prepared in preparation example were added to 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5 mass%) prepared in preparation example at room temperature, and stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 2]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.8316g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.1343g of GBL titania sol (titania solid content concentration: 26.06 mass%) and 0.95g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 3]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.5718g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.0503g of GBL titania sol (titania solid content concentration: 26.06 mass%) and 0.5654g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 4]

Polyimide prepared in Synthesis example at room temperature0.5925g of GBL-M silica sol prepared in preparation example (silica solid content: 25.25% by mass) and TiO were added to 1g of the imide solution (PI, polyimide solid content: 10.5% by mass)₂0.0302g of GBL titania sol (titania solid content concentration: 26.06 mass%) and 0.5648g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 5]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.6133g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂GBL titania sol (titania solid content concentration: 26.06 mass%) 0.0100g and GBL 0.5642g were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 6]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.6186g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.0050g of GBL titania sol (titania solid concentration: 26.06 mass%) and 0.5640g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 7]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.37425g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.04029g of GBL titania sol (titania solid content concentration: 26.06 mass%) and 0.335g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 8]

GBL prepared in preparation example was added to 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5 mass%) prepared in preparation example at room temperature0.5718g of-M silica sol (silica solid content concentration: 25.25% by mass), TiO₂GBL titanium dioxide sol (titanium dioxide solid content concentration: 26.06 mass%) 0.05g and GBL 1.264g, and TEPIC-L (purity 99%) 0.029g were further added thereto and stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 9]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.5198g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.1g of GBL titania sol (titania solid concentration: 26.06 mass%) and 1.266g of GBL, and 0.029g of TEPIC-L (purity 99%) were further added thereto and stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 10]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.4678g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.1511g of GBL titania sol (titania solid concentration: 26.06 mass%), 1.268g of GBL, and 0.029g of TEPIC-L (purity 99%) were further added thereto and stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ example 11]

To 1g of the polyimide solution (PI, polyimide solid content concentration: 10.5% by mass) prepared in preparation example, 0.5458g of GBL-M silica sol (silica solid content concentration: 25.25% by mass) prepared in preparation example, and TiO were added at room temperature₂0.0755g of GBL titania sol (titania solid content concentration: 26.06 mass%) and 0.5654g of GBL were stirred for 30 minutes to obtain a composition for forming a flexible device substrate.

[ production of resin film ]

Each of the compositions for forming a flexible device substrate obtained in examples 1 to 10 was applied to a glass substrate, and the coating film was sequentially heated at 50 ℃ for 30 minutes, 140 ℃ for 30 minutes, 200 ℃ for 60 minutes, and-99 kpa vacuum for 60 minutes at 280 ℃ to obtain a resin film.

The obtained film was peeled off by mechanical cutting and subjected to subsequent evaluation.

[ evaluation of film ]

The heat resistance and optical properties of each resin film (evaluation sample) produced by the above procedure, namely, coefficient of linear expansion (CTE) at 30 ℃ to 220 ℃ and 5% weight loss temperature (Td)_5％) Light transmittance (T)_308nm，T_550nm) And CIE b^*Value (yellow evaluation), retardation (R)_th、R₀) And birefringence (Δ n) were evaluated according to the following procedure. The results are shown in table 1.

1) Coefficient of linear expansion (CTE)

The film was cut into a size of 5mm in width and 16mm in length using TMA Q400 manufactured by TA インスツルメンツ, and the cut film was first heated at 10 ℃/min to 50 to 300 ℃ (first heating), then cooled to 50 ℃ at 10 ℃/min, then heated at 30 to 420 ℃ at 10 ℃/min to (second heating), and the linear expansion coefficient (CTE [ ppm/. degree.C ]) at 30 to 220 ℃ of the second heating was measured. In addition, a load of 0.05N was applied throughout the first heating, cooling, and second heating.

2) 5% weight loss temperature (Td)_5％)

5% weight loss temperature (Td)_5％[℃]) The following is obtained: the film is measured by heating to 50-800 ℃ at 10 ℃/min in nitrogen using TGA Q500 manufactured by TA インスツルメンツ, about 5-10 mg.

3) CIE b value (CIE b)^*)

CIE b value (CIE b)^*) The measurement was performed using a SA4000 spectrophotometer manufactured by japan electro-chromic industry, ltd, using air as a reference at room temperature.

4) Light transmittance (transparency) (T)_308nm、T_550nm)

Light transmittance (T) at wavelengths of 308nm and 550nm_308nm、T_550nm[％]) The measurement was performed using UV-3600 manufactured by Shimadzu corporation at room temperature with air as a reference.

5) Delay (R)_th、R₀)

The thickness direction retardation (R) was measured at room temperature using KOBURA 2100ADH manufactured by prince measuring machine (WAIKO CO., LTD.)_th) And in-plane retardation (R)₀)。

In addition, the thickness direction is retarded (R)_th) And in-plane retardation (R)₀) Calculated using the following equation.

R₀＝(Nx-Ny)×d＝ΔNxy×d

R_th＝[(Nx+Ny)/2-Nz]×d＝[(ΔNxz×d)+(ΔNyz×d)/2

Nx, Ny: in-plane orthogonal 2 indices of refraction (Nx > Ny, Nx also known as the slow axis, Ny also known as the fast axis)

Nz: refractive index in thickness (vertical) direction (vertical) with respect to plane

d: film thickness

Δ Nxy: in-plane 2 difference in refractive index (Nx-Ny) (birefringence)

Δ Nxz: difference between in-plane refractive index Nx and thickness-direction refractive index Nz (birefringence)

Δ Nyz: difference between in-plane refractive index Ny and thickness-direction refractive index Nz (birefringence)

6) Film thickness (d)

The thickness of the obtained thin film was measured by a thickness meter manufactured by Kabushiki Kaisha テクロック.

7) Birefringence (DELTA n)

Using the thickness direction retardation (R) obtained by the above-mentioned < 5) retardation >_th) The value of (d) is calculated by the following equation.

ΔN＝[R_thD (film thickness of film)]/1000

[ solvent resistance test ]

The compositions for forming flexible device substrates obtained in examples 1 and 3 to 10 were applied to a glass substrate at room temperature, the coating film was baked, 2 to 3 drops of TOK-106 (manufactured by tokyo chemical industries, ltd.) were dropped on the obtained resin film, and the resultant film was heated in an air oven at 60 ℃ for 3 minutes. Then, after wiping off the TOK-106, the appearance of the film was visually confirmed.

The film appearance before and after the test was visually observed and evaluated by the following criteria.

O: after solvent testing, the film did not shrink or swell

And (delta): after solvent testing, the film shrinks or expands slightly

X: after solvent testing, the film dissolves, or shrinks or expands

[ evaluation of flexibility ]

When the obtained film was held by both hands and bent at an acute angle (about 30 degrees), the film was evaluated as good when no crack was present and as good when a crack was generated.

The results of the optical properties of the resin films obtained from the compositions for forming flexible device substrates are shown in table 1, and the results of the heat resistance and solvent resistance tests are shown in table 2.

TABLE 1

TABLE 2

Film crazing (the film properties cannot be determined)

As shown in table 1, the following results were obtained for the resin films obtained from the compositions for forming flexible device substrates of examples 2 to 11: light transmittance at wavelength 550nm [% ]]On the other hand, the transmittance of light at a wavelength of 308nm becomes 5% or less, suggesting that the laser lift-off method can be applied. Further, the yellowness (CIE b) of the resin film^*) Also low, further retardation in the thickness direction R_thHas an in-plane retardation R of 404nm or less₀Is extremely low at 4.2nm or less, and the birefringence Δ n is also extremely low at a value of less than 0.015. In addition, as shown in the table2, the results of the above resin film are: coefficient of linear expansion [ ppm/. degree.C. ]](30 to 220 ℃) is low (less than 31 ppm/. degree. C.), the heat resistance is improved, and the flexibility is also provided. Further, in examples 8 to 10, the solvent resistance to the solvent was obtained.

On the other hand, the results of the resin film of example 1 were: although having the same heat resistance and optical characteristics as those of examples 2 to 11, the light transmittance at a wavelength of 308nm was as high as 66.5%, suggesting that it was difficult to apply the laser peeling method when peeling the resin film from the substrate.

[ peeling of resin film by LLO method ]

The compositions for forming flexible device substrates obtained in examples 1 and 11 were applied to a glass substrate, and the coating film was sequentially heated at 50 ℃ for 30 minutes, 140 ℃ for 30 minutes, 200 ℃ for 60 minutes, and-99 kpa vacuum for 60 minutes at 280 ℃ under the air atmosphere to obtain a resin film.

The resin film produced as described above was evaluated for whether or not it was peeled off by the LLO method.

In addition, as the LLO method, the following conditions were adopted.

Laser source: excimer laser XeCl (308nm)

Energy density: 420mJ/cm²、500mJ/cm²、515mJ/cm²、530mJ/cm²、560mJ/cm²、630mJ/cm²

Moving speed of the stage: 7.8 mm/sec

Laser beam size: 14 mm. times.1.3 mm (size at maximum energy: 7.8 mm. times.1.3 mm), and a repeated scanning range of the laser light of 80%

The results are shown in table 3.

In the table,. smallcircle.represents that the resin film was peeled off,. DELTA.represents that there was a partial defect, and. times.represents that there was no peeling.

TABLE 3

*1: film whitening

As shown in Table 3, it was confirmed that the resin film of the present invention shown in example 11 could be peeled by the LLO method. On the other hand, no TiO₂The resin film of example 1 was not peeled off under the same conditions.

As described above, the composition for forming a flexible device substrate of the present invention is a material capable of forming a resin thin film satisfying requirements required as a base film of a flexible device substrate, and has the characteristics of low linear expansion coefficient, high transparency (high light transmittance, low yellowness index), and low retardation, and can impart excellent solvent resistance. In particular, since the resin thin film can sufficiently absorb light having a specific wavelength (308nm) and apply a laser lift-off method, it is expected to be applied to mass production of flexible devices and is particularly suitable as a base film for a substrate of a flexible device.

Claims

1. A composition for forming a flexible device substrate, comprising:

the polyimide is a mixture of a polyimide and a polyimide,

titanium dioxide particles with the particle size of 3 nm-200 nm,

an organic solvent, and a solvent mixture comprising an organic solvent,

wherein the titanium dioxide particles are present in an amount of 3 to 16 mass% based on the total mass of the polyimide, the titanium dioxide particles and the silica particles, the mass ratio of the polyimide to the silica particles is 7: 3 to 3: 7,

the polyimide is obtained by imidizing a polyamic acid obtained by reacting a tetracarboxylic dianhydride component comprising an alicyclic tetracarboxylic dianhydride with a diamine component comprising a fluorine-containing aromatic diamine,

the alicyclic tetracarboxylic dianhydride comprises a tetracarboxylic dianhydride represented by the formula (C1),

in the formula, B¹Represents a 4-valent group selected from the group consisting of formulas (X-1) to (X-12);

wherein R's each independently represents a hydrogen atom or a methyl group, represents a bond,

the fluorine-containing aromatic diamine comprises a diamine represented by the formula (A1),

H₂N-B²-NH₂ (A1)

in the formula, B²Represents a 2-valent group selected from the group consisting of formulas (Y-1) to (Y-34);

in the formula, denotes a bond.

2. The composition for forming a flexible device substrate according to claim 1, further comprising a crosslinking agent composed of a compound which is composed of only hydrogen atoms, carbon atoms, nitrogen atoms and oxygen atoms, has 2 or more groups selected from hydroxyl groups, epoxy groups and alkoxy groups having 1 to 5 carbon atoms, and has a cyclic structure.

3. The composition for forming a flexible device substrate according to claim 1 or 2, wherein the average particle diameter of the silica particles is 60nm or less.

4. The composition for forming a flexible device substrate according to claim 1 or 2, which is a composition for forming a substrate of a flexible device to which a laser lift-off method is applied.

5. A flexible device substrate formed from the composition for forming a flexible device substrate according to any one of claims 1 to 4.

6. A method for manufacturing a flexible device substrate includes the steps of:

a step of forming a flexible device substrate by applying the composition for forming a flexible device substrate according to any one of claims 1 to 4 to a base material, drying and heating the composition,