Laminate

Abstract

Provided is a release layer forming composition that contains an organic solvent and a polyamic acid represented by formula (1) (in the formula, X represents an aromatic group represented by formula (X1), Y represents a divalent organic group not including a fluorine atom but including an aromatic group having an ether bond or an ester bond, and n represents a natural number).

Description

[Technical Field]

[0001] The present invention relates to a release layer-forming composition. [Background technology]

[0002] In recent years, electronic devices have been required to be not only thin and lightweight, but also flexible, which has led to a demand for lightweight, flexible plastic substrates instead of conventional heavy, fragile, and inflexible glass substrates.

[0003] In particular, new generation displays require the development of active matrix full-color TFT display panels using lightweight flexible plastic substrates (hereinafter also referred to as resin substrates). For touch panel displays, materials that support flexibility, such as transparent electrodes and resin substrates for touch panels used in combination with display panels, have been developed. For transparent electrodes, alternative transparent electrode materials have been proposed, such as flexible transparent conductive polymers such as PEDOT, metal nanowires, and mixtures thereof, in addition to the conventionally used ITO (patent documents 1 to 4).

[0004] Meanwhile, the substrate of touch panel films has also changed from glass to sheets made of plastics such as polyethylene terephthalate (PET), polyimide, cycloolefin polymer, and acrylic resin, and transparent flexible touch screen panels with flexibility have been developed (Patent Documents 5 to 7).

[0005] Generally, flexible touch screen panels are produced by forming a release (adhesive) layer on a support substrate such as a glass substrate, and then peeling it off after fabricating the device, in order to ensure stable productivity and peelability (Patent Document 8). This release layer must not peel off from the support substrate during the process, but requires low peeling force when peeling off.

[0006] Furthermore, transparent flexible touchscreen panels typically use transparent plastic substrates, but these transparent plastics often have low glass transition temperatures (Tg). Therefore, when using transparent plastic substrates, the device fabrication process may require firing at temperatures above the Tg of the plastic. In such cases, the release layer and the resin substrate may adhere to each other, making it difficult to peel the resin substrate from the support substrate after device fabrication. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2012 / 147235 [Patent Document 2] Japanese Patent Application Laid-Open No. 2009-283410 [Patent Document 3] Special Publication No. 2010-507199 [Patent Document 4] Japanese Patent Application Laid-Open No. 2009-205924 [Patent Document 5] International Publication No. 2017 / 002664 [Patent Document 6] International Publication No. 2016 / 160338 [Patent Document 7] Japanese Patent Application Laid-Open No. 2015-166145 [Patent Document 8] Japanese Patent Application Laid-Open No. 2014-102490 Summary of the Invention [Problem to be solved by the invention]

[0008] The present invention has been made in consideration of the above circumstances, and aims to provide a composition for forming a release layer that provides a release layer that can be peeled off without damaging the resin substrate of a flexible electronic device. [Means for solving the problem]

[0009] As a result of extensive research to solve the above problems, the present inventors have found that a composition containing a polyamic acid having a specific structure and an organic solvent not only has excellent adhesion to a substrate and adequate adhesion and releasability to a resin substrate used in a flexible electronic device, but also can form a release layer that maintains its adhesion and releasability even when the resin substrate is baked at a temperature above the Tg, thereby completing the present invention.

[0010] That is, the present invention provides the following composition for forming a release layer. 1. A composition for forming a release layer, comprising a polyamic acid represented by the following formula (1) and an organic solvent: [ka] (In the formula, X is an aromatic group represented by the following formula (X1), Y is a divalent organic group containing an aromatic group having an ether bond or an ester bond and not containing a fluorine atom, and n is a natural number.) [ka] 2. The composition for forming a release layer according to 1, wherein the above Y is any one of the aromatic groups represented by the following formulas (Y1) to (Y8). [ka] (In the formula, R 1 ~R 96 represent, independently of each other, a hydrogen atom, a chlorine atom, a bromine atom, or an iodine atom; an alkyl group having 1 to 10 carbon atoms which may be substituted with a chlorine atom, a bromine atom, or an iodine atom; or an aryl group having 6 to 20 carbon atoms which may be substituted with a chlorine atom, a bromine atom, or an iodine atom. 3. The composition for forming a release layer according to 2, wherein the above Y is any one of the aromatic groups represented by the following formulae (Y9) to (Y13). [ka] 4. The composition for forming a release layer according to any one of 1 to 3, wherein the organic solvent is at least one selected from those having a structure represented by the following formulas (S1) to (S7): [ka] (In the formula, R 1s ~R 8s are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, and R 9s and R 10s are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms, and b and m are natural numbers. 5. A release layer obtained from the composition for forming a release layer according to any one of 1 to 4. 6. A method for manufacturing a resin substrate using the release layer of 5. 7. The manufacturing method of 6, wherein the resin substrate is a polyimide substrate. [Effects of the Invention]

[0011] By using the release layer-forming composition of the present invention, it is possible to reproducibly obtain a film having excellent adhesion to the substrate and moderate adhesion and release properties to the resin substrate. In particular, this film does not change in adhesion or release properties even when the resin substrate is baked at a temperature above its Tg, making it suitable for use in fixing resin substrates for flexible touch screen panels. By using the composition of the present invention, it becomes possible to separate the resin substrate from the substrate together with the circuits formed thereon during the manufacturing process of a flexible electronic device without damaging the resin substrate formed on the substrate or any circuits formed thereon. Therefore, the release layer-forming composition of the present invention can contribute to simplifying the manufacturing process of flexible electronic devices equipped with resin substrates and improving their yield. DETAILED DESCRIPTION OF THE INVENTION

[0012] The present invention will be described in more detail below. The release layer-forming composition of the present invention contains a polyamic acid represented by the following formula (1) and an organic solvent. Here, the release layer in the present invention is a layer provided directly on a substrate such as a glass substrate for a specific purpose, and a typical example of such a layer is a layer provided between a substrate and a resin substrate of a flexible electronic device made of a resin such as polyimide in a specific process during the manufacturing process of a flexible electronic device, in order to fix the resin substrate during the specific process and to enable the resin substrate to be easily peeled from the substrate after an electronic circuit or the like is formed on the resin substrate.

[0013] [ka]

[0014] In the formula, X is an aromatic group represented by the following formula (X1), and Y is a divalent organic group containing an aromatic group having an ether bond or an ester bond and not containing a fluorine atom. n represents a natural number, but is preferably an integer of 2 or more.

[0015] [ka]

[0016] Examples of Y include aromatic groups having a structure in which a plurality of aromatic rings having 6 to 20 carbon atoms are linked by ester or ether bonds. Specific examples of the aromatic ring include a benzene ring, a biphenyl ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Of these, from the viewpoint of ensuring the solubility of the polyamic acid in organic solvents, it is preferable to have a structure in which two or three aromatic rings are linked by ester or ether bonds. Aromatic groups represented by the following formulae (Y1) to (Y8) are more preferred.

[0017] [ka]

[0018] In the formula, R 1 ~R 96 represent, independently of each other, a hydrogen atom, a chlorine atom, a bromine atom, or an iodine atom; an alkyl group having 1 to 10 carbon atoms which may be substituted with a chlorine atom, a bromine atom, or an iodine atom; or an aryl group having 6 to 20 carbon atoms which may be substituted with a chlorine atom, a bromine atom, or an iodine atom.

[0019] Examples of the alkyl group having 1 to 10 carbon atoms include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, an s-butyl group, a t-butyl group, an n-pentyl group, an n-hexyl group, an n-heptyl group, an n-octyl group, an n-nonyl group, and an n-decyl group.

[0020] Examples of the aryl group having 6 to 20 carbon atoms include a phenyl group, a tolyl group, a 1-naphthyl group, a 2-naphthyl group, a 1-anthryl group, a 2-anthryl group, a 9-anthryl group, a 1-phenanthryl group, a 2-phenanthryl group, a 3-phenanthryl group, a 4-phenanthryl group, and a 9-phenanthryl group.

[0021] Among these, R 1 ~R 96 is preferably a hydrogen atom, an alkyl group having 1 to 3 carbon atoms or a phenyl group, more preferably a hydrogen atom, a methyl group or an ethyl group, and even more preferably a hydrogen atom.

[0022] The above Y is more preferably an aromatic group represented by the following formulae (Y1-1) to (Y8-1).

[0023] [ka] (In the formula, R 1 ~R 96 is the same as above.)

[0024] More preferred specific examples of Y include aromatic groups represented by the following formulae (Y9) to (Y13), but are not limited thereto.

[0025] [ka]

[0026] The polyamic acid represented by the above formula (P1) can be obtained by reacting the following aromatic diamine component with the aromatic tetracarboxylic dianhydride component.

[0027] The aromatic diamine may be an aromatic diamine containing an ether bond or an ester bond but not containing a fluorine atom. Examples of such aromatic diamines include diamines having a structure in which multiple aromatic rings having 6 to 20 carbon atoms are linked by ester or ether bonds. Specific examples of the aromatic ring include a benzene ring, a naphthalene ring, an anthracene ring, and a phenanthrene ring. Among these, from the viewpoint of ensuring the solubility of the polyamic acid in organic solvents, diamines having a structure in which two or three aromatic rings are linked by ester or ether bonds are preferred, and aromatic diamines containing the structures represented by the above formulas (Y1) to (Y8) are more preferred.

[0028] In the present invention, preferred specific examples of the aromatic diamine include the following.

[0029] [ka]

[0030] [ka]

[0031] [ka]

[0032] [ka]

[0033] [ka]

[0034] [ka]

[0035] In the present invention, other diamines may be used in addition to the aromatic diamines described above.

[0036] Such diamines may be either aliphatic diamines or aromatic diamines, but from the viewpoint of ensuring the strength and heat resistance of the resulting thin film, aromatic diamines that contain neither an ether bond nor an ester bond nor a fluorine atom are preferred.

[0037] Specific examples thereof include diamines containing one benzene nucleus such as 1,4-diaminobenzene (p-phenylenediamine), 1,3-diaminobenzene (m-phenylenediamine), 1,2-diaminobenzene (o-phenylenediamine), 2,4-diaminotoluene, 2,5-diaminotoluene, 2,6-diaminotoluene, 4,6-dimethyl-m-phenylenediamine, 2,5-dimethyl-p-phenylenediamine, 2,6-dimethyl-p-phenylenediamine, 2,4,6-trimethyl-1,3-phenylenediamine, 2,3,5,6-tetramethyl-p-phenylenediamine, m-xylylenediamine, and p-xylylenediamine; 1,2-naphthalenediamine, 1,3-naphthalenediamine, 1,4-naphthalenediamine, 1,5-naphthalenediamine, 1,6-naphthalenediamine, 1,7-naphthalenediamine, and 1,8-naphthalenediamine. amine, 2,3-naphthalenediamine, 2,6-naphthalenediamine, 4,4'-biphenyldiamine, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3'-dicarboxy-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 4,4'-diaminobenzanilide, 3,3'-dichlorobenzidine, 3,3'-dimethylbenzidine, 2,2 diamines containing two benzene nuclei, such as '-dimethylbenzidine, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 2,2-bis(3-aminophenyl)propane, 2,2-bis(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfoxide, 3,4'-diaminodiphenyl sulfoxide, and 4,4'-diaminodiphenyl sulfoxide;1,5-Diaminoanthracene, 2,6-diaminoanthracene, 9,10-diaminoanthracene, 1,8-diaminophenanthrene, 2,7-diaminophenanthrene, 3,6-diaminophenanthrene, 9,10-diaminophenanthrene, 1,3-bis(3-aminophenyl)benzene, 1,3-bis(4-aminophenyl)benzene, 1,4-bis(3-aminophenyl)benzene, 1,4-bis(4-aminophenyl)benzene, 1,3-bis(3-aminophenylsulfide)benzene, 1,3-bis(4-aminophenylsulfide)benzene Examples of diamines include, but are not limited to, diamines containing three benzene rings, such as 1,4-bis(4-aminophenylsulfide)benzene, 1,4-bis(4-aminophenylsulfide)benzene, 1,3-bis(3-aminophenylsulfone)benzene, 1,3-bis(4-aminophenylsulfone)benzene, 1,4-bis(4-aminophenylsulfone)benzene, 1,3-bis[2-(4-aminophenyl)isopropyl]benzene, 1,4-bis[2-(3-aminophenyl)isopropyl]benzene, and 1,4-bis[2-(4-aminophenyl)isopropyl]benzene. These may be used alone or in combination of two or more.

[0038] In the present invention, when an aromatic diamine containing an ether bond or an ester bond but not containing a fluorine atom is used together with another diamine, the amount of the aromatic diamine containing an ether bond or an ester bond but not containing a fluorine atom used is preferably 70 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, and even more preferably 95 mol % or more of the total diamines. By adopting such an amount, a film having excellent adhesion to the substrate and adequate adhesion and adequate peelability from the resin substrate can be obtained with good reproducibility.

[0039] In the present invention, preferred specific examples of the aromatic tetracarboxylic dianhydride component containing an aromatic group represented by the above formula (X1) include those shown below.

[0040] [ka]

[0041] In the present invention, other tetracarboxylic acid dianhydrides can be used together with the aromatic tetracarboxylic acid dianhydride containing an aromatic group represented by the above formula (X1).

[0042] Such a tetracarboxylic acid dianhydride may be either an aliphatic tetracarboxylic acid dianhydride or an aromatic tetracarboxylic acid dianhydride. From the viewpoint of ensuring the strength and heat resistance of the resulting thin film, however, an aromatic tetracarboxylic acid dianhydride containing neither an ester bond nor an ether bond is preferred.

[0043] Specific examples thereof include pyromellitic dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, naphthalene-1,2,3,4-tetracarboxylic dianhydride, naphthalene-1,2,5,6-tetracarboxylic dianhydride, naphthalene-1,2,6,7-tetracarboxylic dianhydride, naphthalene-1,2,7,8-tetracarboxylic dianhydride, naphthalene-2,3,5,6-tetracarboxylic dianhydride, and naphthalene-2,3,6 ,7-tetracarboxylic dianhydride, naphthalene-1,4,5,8-tetracarboxylic dianhydride, biphenyl-2,2',3,3'-tetracarboxylic dianhydride, biphenyl-2,3,3',4'-tetracarboxylic dianhydride, biphenyl-3,3',4,4'-tetracarboxylic dianhydride, anthracene-1,2,3,4-tetracarboxylic dianhydride, anthracene-1,2,5,6-tetracarboxylic dianhydride, anthracene-1 ,2,6,7-tetracarboxylic dianhydride, anthracene-1,2,7,8-tetracarboxylic dianhydride, anthracene-2,3,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,3,4-tetracarboxylic dianhydride, phenanthrene-1,2,5,6-tetracarboxylic dianhydride, phenanthrene-1,2,6,7-tetracarboxylic dianhydride, phenanthrene-1,2,7,8-tetracarboxylic dianhydride, phenanthrene Examples include, but are not limited to, anthren-1,2,9,10-tetracarboxylic dianhydride, phenanthrene-2,3,5,6-tetracarboxylic dianhydride, phenanthrene-2,3,6,7-tetracarboxylic dianhydride, phenanthrene-2,3,9,10-tetracarboxylic dianhydride, phenanthrene-3,4,5,6-tetracarboxylic dianhydride, and phenanthrene-3,4,9,10-tetracarboxylic dianhydride. These may be used alone or in combination of two or more.

[0044] In particular, from the viewpoint of ensuring heat resistance, the aromatic tetracarboxylic acid dianhydride containing neither an ester bond nor an ether bond is preferably at least one selected from the group consisting of formulae (C1) to (C12), and more preferably at least one selected from the group consisting of formulae (C1) and (C9).

[0045] [ka]

[0046] In the present invention, when an aromatic tetracarboxylic acid dianhydride having an aromatic group represented by formula (X1) and another tetracarboxylic acid dianhydride are used together, the amount of the aromatic tetracarboxylic acid dianhydride having an aromatic group represented by formula (X1) used is preferably 70 mol % or more, more preferably 80 mol % or more, even more preferably 90 mol % or more, and even more preferably 95 mol % or more of the total tetracarboxylic acid dianhydrides. By adopting such an amount, a film having sufficient adhesion to the substrate, adequate adhesion to the resin substrate, and adequate peelability can be reproducibly obtained.

[0047] The polyamic acid contained in the release layer-forming composition according to the present invention can be obtained by reacting the diamine and tetracarboxylic dianhydride described above.

[0048] The organic solvent used in such a reaction is not particularly limited as long as it does not adversely affect the reaction, and specific examples include m-cresol, 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone, N-vinyl-2-pyrrolidone, N,N-dimethylacetamide, N,N-dimethylformamide, 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, etc. The organic solvents may be used alone or in combination of two or more.

[0049] The reaction temperature during synthesis of polyamic acid may be set appropriately within the range from the melting point to the boiling point of the solvent used, and is usually about 0 to 100° C. However, in order to prevent imidization in the resulting polyamic acid solution and maintain a high content of polyamic acid units, the temperature is preferably about 0 to 70° C., more preferably about 0 to 60° C., and even more preferably about 0 to 50° C. The reaction time cannot be generally determined because it depends on the reaction temperature and the reactivity of the raw materials, but is usually about 1 to 100 hours.

[0050] The above-described method can produce a reaction solution containing the target polyamic acid. The polyamic acid may be end-capped for the purpose of adjusting the peel strength, etc. In this case, a method such as generating a polyamic acid using an excess of diamine and then reacting it with phthalic anhydride, or generating a polyamic acid using an excess of acid dianhydride and then reacting it with aniline may be used.

[0051] The weight-average molecular weight of the polyamic acid is preferably 5,000 to 1,000,000, more preferably 10,000 to 500,000, and from the viewpoint of handleability, even more preferably 15,000 to 200,000. In the present invention, the weight-average molecular weight is the average molecular weight obtained by gel permeation chromatography (GPC) analysis in terms of standard polystyrene.

[0052] In the present invention, the reaction solution is usually filtered, and the filtrate can be used as it is, or the solution obtained by diluting or concentrating it can be used as the release layer-forming composition of the present invention. By doing so, not only can the inclusion of impurities that may cause deterioration in the adhesion, release properties, etc. of the resulting release layer be reduced, but also the release layer-forming composition can be obtained efficiently. In addition, after isolating the polyamic acid from the reaction solution, it can be dissolved again in a solvent to form the release layer-forming composition. In this case, the solvent can be the organic solvent used in the reaction described above, etc.

[0053] The release layer-forming composition of the present invention contains an organic solvent. As this organic solvent, the same as the specific examples of the reaction solvent for the above reaction can be used, but an organic solvent selected from the group consisting of amides, alcohols, esters, ethers, and ketones is preferred because it dissolves the polyamic acid of the present invention well and makes it easy to prepare a highly uniform composition. In particular, it is preferred to contain at least one organic solvent having a structure represented by the following formulas (S1) to (S7).

[0054] [ka]

[0055] In the above formula, R 1s ~R 8s R are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5 carbon atoms. 9s and R 10s are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, preferably 1 to 5, or an acyl group having 1 to 10 carbon atoms, preferably 1 to 5. b represents a natural number, preferably a natural number of 1 to 5, and more preferably a natural number of 1 to 3. m represents a natural number, preferably a natural number of 1 to 5, and more preferably a natural number of 1 to 3.

[0056] Specific examples of the alkyl group having 1 to 10 carbon atoms may be linear, branched, or cyclic, and include methyl, ethyl, n-propyl, isopropyl, cyclopropyl, n-butyl, isobutyl, s-butyl, t-butyl, n-pentyl, 1-methyl-n-butyl, 2-methyl-n-butyl, 3-methyl-n-butyl, 1,1-dimethyl-n-propyl, 1,2-dimethyl-n-propyl, 2,2-dimethyl-n-propyl, 1-ethyl-n-propyl, cyclopentyl, n-hexyl, 1-methyl-n-pentyl, 2-methyl-n-pentyl, 3-methyl-n-pentyl, and the like. ethyl, 4-methyl-n-pentyl, 1,1-dimethyl-n-butyl, 1,2-dimethyl-n-butyl, 1,3-dimethyl-n-butyl, 2,2-dimethyl-n-butyl, 2,3-dimethyl-n-butyl, 3,3-dimethyl-n-butyl, 1-ethyl-n-butyl, 2-ethyl-n-butyl, 1,1,2-trimethyl-n-propyl, 1,2,2-trimethyl-n-propyl, 1-ethyl-1-methyl-n-propyl, 1-ethyl-2-methyl-n-propyl, cyclohexyl, n-heptyl, n-octyl, n-nonyl, and n-decyl groups.

[0057] Specific examples of the acyl group having 1 to 10 carbon atoms include a formyl group, an acetyl group, a propionyl group, a butyryl group, an isobutyryl group, a valeryl group, an isovaleryl group, a hexanoyl group, an isohexanoyl group, a heptanoyl group, an isoheptanoyl group, an octanoyl group, an isooctanoyl group, a nonanoyl group, an isononanoyl group, a decanoyl group, an isodecanoyl group, and a benzoyl group.

[0058] Specific examples of the organic solvents represented by the above formulas (S1) to (S7) include the following. Formula (S1): 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 Formula (S2): 2-pyrrolidone, N-methyl-2-pyrrolidone, N-ethyl-2-pyrrolidone Formula (S3): N,N-dimethylformamide, N,N-dimethylacetamide, N,N-dimethylpropylamide, N,N-dimethylbutanamide Formula (S4): γ-butyrolactone Formula (S5): Cyclopentanone, cyclohexanone, cycloheptanone Formula (S6): methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, isoamyl lactate, methyl 2-hydroxyisobutyrate, ethyl 2-hydroxyisobutyrate, propyl 2-hydroxyisobutyrate, butyl 2-hydroxyisobutyrate Formula (S7): ethyl cellosolve, butyl cellosolve, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, propylene glycol monomethyl ether, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate

[0059] In the present invention, among these, N-methyl-2-pyrrolidone, butyl cellosolve, propylene glycol monomethyl ether, and propylene glycol monomethyl ether acetate are preferred, propylene glycol monomethyl ether and propylene glycol monomethyl ether acetate are more preferred, and propylene glycol monomethyl ether is even more preferred. These organic solvents may be used alone or in combination of two or more.

[0060] In addition, even if a solvent does not dissolve polyamic acid alone, it can be mixed into the release layer-forming composition of the present invention as long as the polyamic acid does not precipitate. In particular, solvents having low surface tension such as ethyl cellosolve, butyl cellosolve, ethyl carbitol, butyl carbitol, ethyl carbitol acetate, ethylene glycol, 1-methoxy-2-propanol, 1-ethoxy-2-propanol, 1-butoxy-2-propanol, 1-phenoxy-2-propanol, propylene glycol monoacetate, propylene glycol diacetate, propylene glycol-1-monomethyl ether-2-acetate, propylene glycol-1-monoethyl ether-2-acetate, dipropylene glycol, 2-(2-ethoxypropoxy)propanol, methyl lactate, ethyl lactate, n-propyl lactate, n-butyl lactate, and isoamyl lactate can be mixed in an appropriate amount. This is known to improve the uniformity of the coating film when applied to the substrate, and is also preferably used in the release layer-forming composition of the present invention.

[0061] The concentration of polyamic acid in the release layer-forming composition of the present invention is set appropriately taking into consideration the thickness of the release layer to be produced, the viscosity of the composition, etc., but is usually about 1 to 30% by mass, preferably about 1 to 20% by mass. By setting such a concentration, a release layer having a thickness of about 0.05 to 5 μm can be reproducibly obtained. The concentration of polyamic acid can be adjusted by adjusting the amounts of diamine and tetracarboxylic dianhydride used as raw materials for polyamic acid, by filtering the reaction solution and then diluting or concentrating the filtrate, or by adjusting the amount of the isolated polyamic acid when dissolving it in a solvent.

[0062] The viscosity of the release layer-forming composition is determined appropriately taking into account factors such as the thickness of the release layer to be produced. For example, when the goal is to reproducibly obtain a film having a thickness of approximately 0.05 to 5 μm, the viscosity is typically approximately 10 to 10,000 mPa·s at 25°C, and preferably approximately 20 to 5,000 mPa·s. Here, viscosity can be measured using a commercially available viscometer for measuring the viscosity of liquids, for example, according to the procedure described in JIS K7117-2, at a composition temperature of 25°C. Preferably, a cone-plate type rotational viscometer is used, preferably using a 1°34' x R24 standard cone rotor, at a composition temperature of 25°C. An example of such a rotational viscometer is the TVE-25L manufactured by Toki Sangyo Co., Ltd.

[0063] The release layer-forming composition according to the present invention may contain, in addition to the polyamic acid and the organic solvent, a component such as a crosslinking agent, for example, in order to improve the film strength.

[0064] The release layer-forming composition of the present invention described above is applied to a substrate, and the resulting coating film is heated to thermally imidize the polyamic acid, thereby obtaining a release layer consisting of a polyimide film that has excellent adhesion to the substrate, as well as moderate adhesion and moderate releasability to a resin substrate.

[0065] When the release layer of the present invention is formed on a substrate, the release layer may be formed on a portion of the surface of the substrate, or may be formed on the entire surface. Forms of forming a release layer on a portion of the surface of the substrate include a form in which the release layer is formed only in a predetermined area of ​​the substrate surface, and a form in which the release layer is formed in a pattern such as a dot pattern or a line and space pattern on the entire surface of the substrate. In the present invention, the substrate means a substrate on whose surface the release layer-forming composition of the present invention is applied and which is used in the manufacture of flexible electronic devices, etc.

[0066] Examples of the substrate (base material) include glass, plastics (polycarbonate, polymethacrylate, polystyrene, polyester, polyolefin, epoxy, melamine, triacetyl cellulose, ABS, AS, norbornene-based resins, etc.), metals (silicon wafers, etc.), wood, paper, slate, etc., but glass is particularly preferred because the release layer obtained from the release layer-forming composition of the present invention has sufficient adhesion to it. The substrate surface may be composed of a single material, or may be composed of two or more materials. Examples of embodiments in which the substrate surface is composed of two or more materials include an embodiment in which a certain area of ​​the substrate surface is composed of one material and the remaining surface is composed of another material, and an embodiment in which a material in a pattern such as a dot pattern or line and space pattern is present among the other materials over the entire substrate surface.

[0067] The coating method is not particularly limited, but examples thereof include cast coating, spin coating, blade coating, dip coating, roll coating, bar coating, die coating, inkjet printing, and printing methods (relief printing, intaglio printing, lithography, screen printing, etc.).

[0068] The heating temperature for imidization is usually determined appropriately within the range of 50 to 550°C, but is preferably 200°C or higher, and preferably 500°C or lower. By setting the heating temperature in this manner, it becomes possible to prevent the resulting film from becoming brittle while allowing the imidization reaction to proceed sufficiently. The heating time cannot be specified in general because it varies depending on the heating temperature, but is usually 5 minutes to 5 hours. The imidization rate may be in the range of 50 to 100%.

[0069] A preferred example of the heating mode in the present invention is a method in which heating is performed at 50 to 170°C for 1 minute to 2 hours, followed by gradually increasing the heating temperature to 180 to 450°C for 30 minutes to 4 hours. In particular, heating at 50 to 150°C for 1 minute to 2 hours, followed by heating at 220 to 300°C for 5 minutes to 2 hours is preferred.

[0070] Examples of heating equipment include a hot plate, an oven, etc. The heating atmosphere may be air or an inert gas, and may be atmospheric pressure or reduced pressure.

[0071] The thickness of the release layer is usually about 0.01 to 50 μm, preferably about 0.05 to 20 μm, more preferably about 0.05 to 5 μm, from the viewpoint of productivity, and the desired thickness is achieved by adjusting the thickness of the coating film before heating.

[0072] The release layer described above has excellent adhesion to a substrate, particularly a glass substrate, and moderate adhesion and release properties to a resin substrate. Therefore, the release layer according to the present invention can be suitably used in the manufacturing process of a flexible electronic device to release the resin substrate together with circuits and the like formed on the resin substrate from the substrate without damaging the resin substrate.

[0073] An example of a method for producing a flexible electronic device using the release layer of the present invention will now be described. A release layer is formed on a glass substrate using the release layer-forming composition according to the present invention by the method described above. A resin solution for forming a resin substrate is applied onto the release layer, and the coating is heated to form a resin substrate fixed to the glass substrate via the release layer according to the present invention. In this process, the resin substrate is formed so as to completely cover the release layer and have an area larger than that of the release layer. Examples of the resin substrate include resin substrates made of polyimide resins, acrylic resins, and cycloolefin polymer resins, which are typical resin substrates for flexible electronic devices. Examples of resin solutions for forming such substrates include polyimide solutions, polyamic acid solutions, acrylic polymer solutions, and cycloolefin polymer solutions. The resin substrate may be formed according to conventional methods. Examples of highly transparent resin substrates include resin substrates made of polyimide resins, acrylic resins, or cycloolefin polymer resins, with those having a light transmittance of 80% or more at a wavelength of 450 nm being particularly preferred.

[0074] Next, a desired circuit is formed on the resin substrate fixed to the base via the release layer according to the present invention, and then the resin substrate is cut, for example, along the release layer, and the resin substrate together with the circuit is peeled off from the release layer to separate the resin substrate from the base. At this time, a part of the base may be cut together with the release layer.

[0075] In the present invention, the peel force when peeling the resin substrate from the base is preferably less than 0.5 N / 25 mm, more preferably less than 0.4 N / 25 mm, and even more preferably less than 0.3 N / 25 mm, from the viewpoint of finally peeling the resin substrate from the base easily. On the other hand, the lower limit of the peel force is not particularly limited, but is preferably 0.001 N / 25 mm or more, more preferably 0.01 N / 25 mm or more, and even more preferably 0.02 N / 25 mm or more, from the viewpoint of stably fixing the resin substrate on the base and stably fabricating an electronic device.

[0076] The release layer according to the present invention maintains a peel force within the above-mentioned range when peeling the resin substrate from the base, even when the resin substrate formed thereon is baked at a temperature equal to or higher than Tg. For example, even when a resin substrate having a Tg of 200°C or less is formed on the release layer formed using the release layer-forming composition according to the present invention and baked at a temperature equal to or higher than 230°C, it is preferable that the resin substrate can be peeled with a peel force within the above-mentioned range.

[0077] Meanwhile, in the manufacture of flexible displays, it has been reported that a polymer substrate can be effectively peeled from a glass carrier using the laser lift-off (LLO) method, which has previously been used in the manufacture of high-brightness LEDs and three-dimensional semiconductor packages (JP 2013-147599 A). In the manufacture of flexible displays, a polymer substrate made of polyimide or the like is provided on a glass carrier, and then circuits, including electrodes, are formed on the substrate. Finally, the substrate, along with the circuits, is peeled off from the glass carrier. By employing the LLO method in this peeling process, light with a wavelength of 308 nm is irradiated onto the glass carrier from the side opposite the side on which the circuits are formed. The light transmits through the glass carrier, and only the polymer (polyimide) near the glass carrier absorbs the light and evaporates (sublimes). As a result, it has been reported that selective peeling of the substrate from the glass carrier is possible without affecting the circuits, which determine the display's performance.

[0078] When a desired circuit is formed on the resin substrate fixed to a substrate via the release layer of the present invention and then the LLO method is employed, only the release layer absorbs the light and evaporates (sublimes). In other words, the release layer becomes a sacrifice (functions as a sacrificial layer), allowing selective peeling of the substrate from the glass carrier. The release layer-forming composition of the present invention is characterized by its ability to sufficiently absorb light of a specific wavelength (e.g., 308 nm) that makes the LLO method applicable, and therefore can be used as a sacrificial layer in the LLO method. [Example]

[0079] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples. The abbreviations of the compounds used in the examples, and the methods for measuring the number-average molecular weight and weight-average molecular weight are as follows:

[0080] <Compound abbreviation> p-PDA: p-phenylenediamine DA-4P: 1,3-bis(4-aminophenoxy)benzene DA-4: 1,4-bis(4-aminophenoxy)benzene DDE: 4,4'-oxydianiline 3,4'-DDE: 3,4'-diaminodiphenyl ether 3,3'-DDE: 3,3'-diaminodiphenyl ether DA-3F: 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane BTFDPE: 2,2'-trifluoromethyl-4,4'-diaminodiphenyl ether BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride PMDA: Pyromellitic dianhydride TAHQ: p-phenylenebis(trimellitic acid monoester acid anhydride) BPTME: p-biphenylenebis(trimellitic acid monoester acid anhydride) ODPA: 4,4'-oxydiphthalic anhydride NMP: N-methyl-2-pyrrolidone BCS: Butyl cellosolve

[0081] <Measurement of number average molecular weight and weight average molecular weight> The weight-average molecular weight (Mw) and molecular weight distribution (Mw / Mn) of the polymer were measured using a GPC system manufactured by JASCO Corporation (columns: KD801 and KD805 manufactured by Shodex; eluent: dimethylformamide / LiBr·HO (29.6 mM) / HPO (29.6 mM) / THF (0.1% by mass); flow rate: 1.0 mL / min; column temperature: 40°C; Mw: value converted into standard polystyrene) (the same applies to the following examples and comparative examples).

[0082] [1] Polymer synthesis Polyamic acid was synthesized by the following method. The polymer was not isolated from the resulting polymer-containing reaction liquid, but was diluted as described below to prepare a composition for forming a resin substrate or a composition for forming a release layer.

[0083] [Synthesis Example 1] Synthesis of polyamic acid L1 214.9 g (0.74 mmol) of DA-4P was dissolved in 4,400 g of NMP. 385.1 g (0.72 mmol) of BPTME was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid L1. The Mw of polyamic acid L1 was 50,700, and the Mw / Mn ratio was 2.51.

[0084] [Synthesis Example 2] Synthesis of polyamic acid L2 214.9 g (0.74 mol) of DA-4 was dissolved in 4,400 g of NMP. 385.1 g (0.72 mol) of BPTME was added to the resulting solution, and the mixture was reacted at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid L2. The Mw of polyamic acid L2 was 56,400, and the Mw / Mn ratio was 2.6.

[0085] [Synthesis Example 3] Synthesis of polyamic acid L3 165.9 g (0.83 mmol) of DDE was dissolved in 4,400 g of NMP. 434.1 g (0.81 mmol) of BPTME was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid L3. The Mw of polyamic acid L3 was 48,300, and the Mw / Mn ratio was 2.6.

[0086] [Synthesis Example 4] Synthesis of polyamic acid L4 165.9 g (0.83 mol) of 3.4'-DDE was dissolved in 4,400 g of NMP. 434.1 g (0.81 mmol) of BPTME was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid L4. The Mw of polyamic acid L4 was 31,000, and the Mw / Mn ratio was 2.4.

[0087] [Synthesis Example 5] Synthesis of polyamic acid L5 165.9 g (0.83 mol) of 3,3'-DDE was dissolved in 4,400 g of NMP. 434.1 g (0.81 mmol) of BPTME was added to the resulting solution, and the mixture was reacted at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid L5. The Mw of polyamic acid L5 was 25,300, and the Mw / Mn ratio was 2.3.

[0088] [Comparative Synthesis Example 1] Synthesis of polyamic acid HL1 3.218 g (30 mmol) of p-PDA was dissolved in 88.2 g of NMP. 8.581 g (29 mmol) of BPDA was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid HL1. The Mw of polyamic acid HL1 was 107,300, and the Mw / Mn ratio was 4.6.

[0089] [Comparative Synthesis Example 2] Synthesis of polyamic acid HL2 0.931 g (8.6 mmol) of p-PDA was dissolved in 35.2 g of NMP. 3.868 g (8.4 mmol) of TAHQ was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid HL2. The Mw of polyamic acid HL2 was 45,000, and the Mw / Mn ratio was 2.7.

[0090] [Comparative Synthesis Example 3] Synthesis of polyamic acid HL3 2.984 g (5.6 mmol) of DA-3F was dissolved in 35.2 g of NMP. 3.015 g (5.8 mmol) of BPTME was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid HL3. The Mw of polyamic acid HL3 was 45,000, and the Mw / Mn ratio was 2.7.

[0091] [Comparative Synthesis Example 4] Synthesis of polyamic acid HL4 5.55 g (51 mmol) of p-PDA was dissolved in 132 g of NMP. 12.45 g (57 mmol) of PMDA was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid HL3. The Mw of polyamic acid HL3 was 76,400, and the Mw / Mn ratio was 2.2.

[0092] [Comparative Synthesis Example 5] Synthesis of polyamic acid HL5 0.235 g (0.70 mmol) of BTFDPE was dissolved in 4 g of NMP. 0.365 g (0.68 mmol) of BPTME was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid HL5. The Mw of polyamic acid HL5 was 42,600, and the Mw / Mn ratio was 2.6.

[0093] [Synthesis Example F1] Synthesis of polyamic acid F1 392.1 g (1.3 mol) of DA-4P was dissolved in 3,200 g of NMP. 407.8 g (1.3 mol) of ODPA was added to the resulting solution, and the mixture was allowed to react at 23°C for 24 hours under a nitrogen atmosphere to obtain polyamic acid F1. The Mw of polyamic acid F1 was 60,400, and the Mw / Mn ratio was 2.9.

[0094] [2] Preparation of composition for forming resin substrate The reaction liquid obtained in Synthesis Example F1 was used as it was as a composition for forming a resin substrate.

[0095] [3] Preparation of release layer-forming composition [Example 1-1] BCS and NMP were added to the reaction liquid obtained in Synthesis Example 1, and the mixture was diluted to a polymer concentration of 5 mass % and a BCS concentration of 20 mass %, to obtain a composition for forming a release layer.

[0096] [Examples 1-2 to 1-5] Compositions for forming a release layer were obtained in the same manner as in Example 1-1, except that the reaction liquid obtained in Synthesis Example 1 was replaced with the reaction liquids obtained in Synthesis Examples 2 to 5, respectively.

[0097] [Comparative Examples 1-1 to 1-5] Compositions for forming a release layer were obtained in the same manner as in Example 1-1, except that the reaction liquid obtained in Synthesis Example 1 was replaced with the reaction liquids obtained in Comparative Synthesis Examples 1 to 5, respectively.

[0098] [4] Formation of peeling layer [Example 2-1] The release layer-forming composition obtained in Example 1-1 was applied onto a 100 mm x 100 mm glass substrate (hereinafter the same) as a glass substrate using a spin coater (conditions: rotation speed 3,000 rpm for approximately 30 seconds). The resulting coating film was heated at 80°C for 10 minutes using a hot plate, and then heated at 230°C for 30 minutes using an oven to form a release layer with a thickness of approximately 0.1 µm on the glass substrate, thereby obtaining a glass substrate with a release layer. Note that during the temperature increase, the glass substrate with the release layer was heated in the oven without being removed from the oven.

[0099] [Examples 2-2 to 2-5] A release layer was formed in the same manner as in Example 2-1, except that the release layer-forming compositions obtained in Examples 1-2 to 1-5 were used instead of the release layer-forming composition obtained in Example 1-1, and a glass substrate with a release layer was obtained.

[0100] [Comparative Examples 2-1 to 2-5] A release layer was formed in the same manner as in Example 2-1, except that the release layer-forming compositions obtained in Comparative Examples 1-1 to 1-5 were used instead of the release layer-forming composition obtained in Example 1-1, and a glass substrate with a release layer was obtained.

[0101] [5] Evaluation of resin substrate formation and peelability [Example 3-1] Using a bar coater (gap: 250 μm), the resin substrate-forming composition was applied onto the release layer (resin thin film) on the glass substrate with the release layer obtained in Example 2-1. The resulting coating film was heated on a hot plate at 100°C for 30 minutes, and then heated in an oven at 230°C for 60 minutes, forming a polyimide substrate with a thickness of approximately 20 μm on the release layer.

[0102] [Examples 3-2 to 3-5, Comparative Examples 3-1 to 3-5] A polyimide substrate was formed on a release layer in the same manner as in Example 3-1, except that the glass substrates with release layers obtained in Examples 2-2 to 2-5 and Comparative Examples 2-1 to 2-5 were used instead of the glass substrate with release layer obtained in Example 2-1.

[0103] [Examples 3-6] Using a bar coater (gap: 250 μm), the resin substrate-forming composition was applied onto the release layer (resin thin film) on the glass substrate with the release layer obtained in Example 2-2. The resulting coating film was heated on a hot plate at 100°C for 30 minutes, and then heated in an oven at 300°C for 60 minutes, forming a polyimide substrate with a thickness of approximately 20 μm on the release layer.

[0104] [Examples 3-7 and 3-8] A polyimide substrate was formed on a release layer in the same manner as in Example 3-6, except that the glass substrates with release layers obtained in Examples 2-4 to 2-5 were used instead of the glass substrate with release layer obtained in Example 2-2.

[0105] <Evaluation of peel strength of resin substrate> (1) Peel strength of resin substrate before heat treatment The resin substrates formed in Examples 3-1 to 3-8 and Comparative Examples 3-1 to 3-5 were cut into 25 mm wide strips using a cutter. Cellotape (registered trademark) was then attached to the tip of each cut resin substrate to prepare a test piece. A peel test was performed on this test piece using a push-pull tester manufactured by Atonic Co., Ltd., with a peel angle of 90°, and the peel strength was evaluated based on the following criteria. The peeled surface was observed using an optical microscope, and if the release layer peeled off from the glass substrate, it was deemed defective. The results are shown in Table 1. The Tg of the peeled resin substrate was measured using a TMA-4000SA (manufactured by Bruker AXS Co., Ltd.) and found to be approximately 190°C. In addition, the light transmittance was measured using a UV-visible spectrophotometer (Shimadzu Corporation UV-2600). The resin substrate showed a transmittance of 80% or more at 450 nm.

[0106] Poor: Separation of the release layer and the glass substrate was observed. 4b: No peeling 3b: Peeling force of 1.00N / 25mm or more 2b: Peel force of 0.80N / 25mm or more and less than 1.00N / 25mm 1b: Peeling force of 0.60N / 25mm or more and less than 0.80N / 25mm b: Peeling force of 0.50N / 25mm or more and less than 0.60N / 25mm a: Peeling force of 0.40N / 25mm or more and less than 0.50N / 25mm aa: Peeling force of 0.30N / 25mm or more and less than 0.40N / 25mm aaa: Peel force less than 0.30N / 25mm

[0107] (2) Peel strength of resin substrate after heat treatment The resin substrates formed in Examples 3-1 to 3-8 were fixed on glass substrates and heated in an oven for 2 hours at the temperatures shown in Table 1. The peel strength of the heat-treated resin substrates was evaluated in the same manner as in (1) above. The results are shown in Table 1. The resin substrates of Comparative Examples 3-1 to 3-5 were not evaluated for peel strength after heat treatment because they had adhered to the release layer before the heat treatment and could not be peeled from the release layer.

[0108] [Table 1]

[0109] From the results in Table 1, it was confirmed that the release layer of the example not only has excellent adhesion to the base, and moderate adhesion and moderate releasability to the resin substrate, but also does not adhere to the resin substrate even when the resin substrate is baked at a temperature above Tg, and maintains moderate releasability.

Claims

1. A laminate comprising a glass substrate, a release layer formed on the glass substrate, and a resin substrate formed on the release layer, The laminate, wherein the release layer is obtained from a composition for forming a release layer, which comprises a polyamic acid represented by the following formula (1) and an organic solvent: 【Chemical 1】 (In the formula, X is an aromatic group represented by the following formula (X1), Y is any one of the aromatic groups represented by the following formulas (Y9) to (Y13), and n is a natural number.) 【Chemistry 2】 【Chemistry 3】

2. 2. The laminate according to claim 1, wherein the organic solvent is at least one selected from those having structures represented by the following formulas (S1) to (S7): 【Chemistry 4】 (In the formula, R 1s ~R 8s are each independently a hydrogen atom or an alkyl group having 1 to 10 carbon atoms; R 9s and R 10s are each independently a hydrogen atom, an alkyl group having 1 to 10 carbon atoms, or an acyl group having 1 to 10 carbon atoms, and b and m are natural numbers.

3. A method for producing a resin substrate using the laminate according to claim 1 or 2.

4. 4. The manufacturing method according to claim 3, wherein the resin substrate is a polyimide substrate.

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