CN111300937A

CN111300937A - Laminated body

Info

Publication number: CN111300937A
Application number: CN202010149276.1A
Authority: CN
Inventors: 唐泽真义; 大松一喜; 福井仁之; 岸田明子
Original assignee: Sumitomo Chemical Co Ltd
Current assignee: Sumitomo Chemical Co Ltd
Priority date: 2018-02-14
Filing date: 2019-02-12
Publication date: 2020-06-19
Anticipated expiration: 2039-02-12
Also published as: KR20190098679A; JP2020006682A; KR102025316B1; JP2020006673A; CN110154471A; JP6450048B1; TW201936394A; CN110154471B; JP6538259B1; KR20190110970A; CN111300937B; JP2020007520A

Abstract

The invention provides a laminate comprising a transparent resin film based on a polyimide polymer, which is less likely to cause whitening on the film surface and has good appearance and visibility. The laminate comprises a transparent resin film and a protective film bonded to at least one surface of the transparent resin film, wherein the transparent resin film comprises at least 1 and 1 or more solvents selected from the group consisting of polyimide, polyamide and polyamideimide, and is produced by a casting method using the 1 or more solvents, wherein the solvent having the highest boiling point among the 1 or more solvents has a boiling point of 120 to 300 ℃, the residual solvent amount S (mass%) of the transparent resin film and the low molecular weight component W (%) of the protective film satisfy the relational expression (1), W is 0.33 or less, the residual solvent amount S is calculated as the mass reduction rate from 120 ℃ to 250 ℃ based on thermogravimetric-differential thermal measurement, and the low molecular weight component W is defined as the ratio of the Log M in a graph measured at a measurement temperature of 140 ℃ by gel permeation chromatography to the total area, wherein the Log M is 2.82 to 3.32. S multiplied by W is less than or equal to 4.7 (1).

Description

Laminated body

The present application is a divisional application of chinese patent application 201910111874.7 entitled "laminate" filed on 12.2.2019.

Technical Field

The present invention relates to a laminate.

Background

In recent years, transparent resin films made of polymers such as polyimide and polyamide have been widely used as materials for replacing glass that has been conventionally used, with the reduction in thickness, weight, and flexibility of displays of various image display devices. As one of the methods for producing such a transparent resin film, a casting method (solution casting method) is known. In the casting method, a varnish containing a polymer such as polyimide dissolved in a solvent is usually applied to a support substrate to form a film, and the formed film is peeled off from the support substrate and then dried to remove the solvent, whereby a resin film can be continuously formed. A peelable protective film is appropriately laminated on the surface of a transparent resin film obtained by film formation, thereby protecting the film surface (patent documents 1 to 3).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent application No. 2010-208312

Patent document 2: japanese patent laid-open publication No. 2015-214122

Patent document 3: japanese patent laid-open publication No. 2016-87799

Disclosure of Invention

Problems to be solved by the invention

When a solvent is present in the resin film, components such as additives contained in the protective film may be eluted into the solvent contained in the resin film, and the surface of the resin film to which the protective film is attached may be whitened due to the eluted components. In particular, in the case of a transparent resin film produced by a casting method or the like using a solvent, it is difficult to completely remove the solvent in the varnish in continuous production, and a certain amount of the solvent often remains, and whitening is likely to occur when the film is bonded to a protective film. Such whitening in the transparent resin film not only causes appearance defects in the transparent resin film which is required to have high transparency, but also causes deterioration in visibility when used in displays of various image display devices and the like.

Accordingly, an object of the present invention is to provide a laminate including a transparent resin film made of a polyimide-based polymer, which is less likely to cause whitening on the film surface and has good appearance and visibility.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems, and as a result, have completed the present invention. That is, the present invention provides the following preferred embodiments.

[1] A laminate comprising a transparent resin film and a protective film bonded to at least one surface of the transparent resin film, wherein the transparent resin film comprises 1 or more kinds of solvents and at least 1 kind selected from the group consisting of polyimide, polyamide and polyamideimide, and is produced by a casting method using the 1 or more kinds of solvents,

the boiling point of the solvent with the highest boiling point in the 1 or more solvents is 120-300 ℃,

a residual solvent amount S (mass%) of the transparent resin film calculated as a mass reduction rate from 120 ℃ to 250 ℃ obtained by thermogravimetry-differential thermal (TD-DTA) measurement and a low molecular component amount W (%) of the protective film defined as a ratio of an area where Log M in a graph (chart) measured at a measurement temperature of 140 ℃ by gel permeation chromatography is 2.82 to 3.32 to a total area satisfy a relational expression (1),

S×W≤4.7 (1)，

w is 0.33 or less.

[2] The laminate according to [1], wherein S and W satisfy the relational expression (1'):

0.005≤S×W (1’)。

[3] the laminate according to the above [1] or [2], wherein the transparent resin film has a haze of 1.0% or less.

[4] The laminate according to any one of the above [1] to [3], wherein the transparent resin film has a total light transmittance of 85% or more.

[5] The laminate according to any one of the above [1] to [4], wherein the transparent resin film contains at least 1 kind of solvent selected from the group consisting of N, N-dimethylacetamide, γ -butyrolactone, N-methylpyrrolidone, cyclopentanone, butyl acetate, and amyl acetate.

[6] The laminate according to any one of the above [1] to [5], wherein the protective film is a polyolefin resin film.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, a laminate comprising a transparent resin film made of a polyimide-based polymer, which is less likely to cause whitening on the film surface and has good appearance and visibility, can be provided.

Drawings

FIG. 1 shows the results of TG-DTA measurement of the transparent polyimide-based film produced in example 1.

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail. The scope of the present invention is not limited to the embodiments described herein, and various modifications may be made without departing from the spirit of the present invention.

The laminate of the present invention comprises a transparent resin film and a protective film bonded to at least one surface of the transparent resin film, wherein the transparent resin film constituting the laminate of the present invention comprises at least 1 selected from the group consisting of polyimide, polyamide and polyamideimide, and is formed from a resin composition comprising at least 1 selected from the group consisting of polyimide, polyamide and polyamideimide.

In the present specification, polyimide represents a polymer containing a repeating structural unit containing an imide group, polyamideimide represents a polymer containing both a repeating structural unit containing an imide group and a repeating structural unit containing an amide group, and polyamide represents a polymer containing a repeating structural unit containing an amide group. The polyimide-based polymer is a polymer containing at least one selected from the group consisting of polyimide and polyamideimide.

The polyimide-based polymer according to the present embodiment has a repeating structural unit represented by formula (10). Here, G represents a 4-valent organic group, and a represents a 2-valent organic group. May contain 2 or more kinds of repeating structural units represented by the formula (10) wherein G and/or A are different. The polyimide-based polymer according to the present embodiment may contain any one or more of the repeating structural units represented by any one of the formulae (11), (12), and (13) within a range that does not impair various physical properties of the obtained transparent resin film.

When the main structural unit of the polyimide-based polymer is a repeating structural unit represented by formula (10), it is preferable from the viewpoint of strength and transparency of the transparent resin film. In the polyimide polymer according to the present embodiment, the repeating structural unit represented by formula (10) is preferably 40 mol% or more, more preferably 50 mol% or more, further preferably 70 mol% or more, particularly preferably 90 mol% or more, and particularly more preferably 98 mol% or more, based on the total repeating structural units of the polyimide polymer. The repeating structural unit represented by formula (10) may be 100 mol%.

[ chemical formula 1]

G and G¹Each independently represents a 4-valent organic group, preferably a 4-valent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. As G and G¹Examples thereof may include a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29), and a chain hydrocarbon group having 4-valent carbon atoms of 6 or less. Wherein X represents a bond, Z represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-Ar-、-SO₂-、-CO-、-O-Ar-O-、-Ar-O-Ar-、-Ar-CH₂-Ar-、-Ar-C(CH₃)₂-Ar-or-Ar-SO₂-Ar-. Ar represents an arylene group having 6 to 20 carbon atoms which may be substituted with a fluorine atom, and specific examples thereof include a phenylene group. G and G are the yellowness of the transparent resin film which is easily suppressed¹Preferred examples thereof include a group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26) or formula (27).

[ chemical formula 2]

G²The organic group has a valence of 3, and preferably has a valence of 3 having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. As G²Examples thereof include a group obtained by replacing 1 of the chemical bonds of the group represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) with a hydrogen atom, and a chain hydrocarbon group having 3-valent carbon atoms of 6 or less. Examples of Z in the formula are the same as those of Z described in the description of G.

G³The organic group has a valence of 2, and preferably has a valence of 2 having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. G3 includes a group in which non-adjacent 2 of the chemical bonds of the groups represented by formula (20), formula (21), formula (22), formula (23), formula (24), formula (25), formula (26), formula (27), formula (28) or formula (29) are replaced by hydrogen atoms, and a 2-valent chain hydrocarbon group having 6 or less carbon atoms. Examples of Z in the formula are the same as those of Z described in the description of G.

A、A¹、A²And A³Each represents a 2-valent organic group, preferably a 2-valent organic group having 4 to 40 carbon atoms. The organic group may be substituted with a hydrocarbon group or a fluorine-substituted hydrocarbon group having 1 to 8 carbon atoms, and in this case, the number of carbon atoms of the hydrocarbon group and the fluorine-substituted hydrocarbon group is preferably 1 to 8. As A, A¹、A²And A³Examples of the "heterocyclic group" may include a group represented by formula (30), formula (31), formula (32), formula (33), formula (34), formula (35), formula (36), formula (37) or formula (38); a group obtained by substituting 1 or more of methyl, fluoro, chloro or trifluoromethyl; and a chain hydrocarbon group having 6 or less carbon atoms.

Wherein X represents a bond, Z¹、Z²And Z³Each independently represents a single bond, -O-, -CH₂-、-CH₂-CH₂-、-CH(CH₃)-、-C(CH₃)₂-、-C(CF₃)₂-、-S-、-SO₂-, -CO-or-NR². Here, R²Represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Here, R²Represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom. Z¹And Z²And Z²And Z³Preferably in the meta or para position, respectively, with respect to the rings.

[ chemical formula 3]

In the present invention, the resin composition forming the transparent resin film may contain polyamide. The polyamide according to the present embodiment is a polymer mainly composed of a repeating structural unit represented by formula (13). G in polyamides³And A³Preferred examples and specific examples of (1) and G in the polyimide-based polymer³And A³The preferred examples and specific examples are the same. The aforementioned polyamide may contain G³And/or A³2 or more different repeating structural units represented by the formula (13).

The polyimide-based polymer can be obtained by, for example, polycondensation of a diamine and a tetracarboxylic acid compound (tetracarboxylic dianhydride or the like), and can be synthesized, for example, by the method described in jp 2006-a 199945 or jp 2008-a 163107. Examples of commercially available products of polyimide include Neopulim (registered trademark) manufactured by Mitsubishi gas chemical corporation, KPI-MX300F manufactured by the riverside industries, and the like.

Examples of tetracarboxylic acid compounds that can be used in the synthesis of polyimide-based polymers include aromatic tetracarboxylic acid and anhydrides thereof, preferably aromatic tetracarboxylic acid compounds such as dianhydrides thereof; and aliphatic tetracarboxylic acid and anhydride thereof, preferably an aliphatic tetracarboxylic acid compound such as dianhydride thereof. The tetracarboxylic acid compound may be a tetracarboxylic acid compound derivative such as a tetracarboxylic acid chloride compound, other than the anhydride, and these may be used alone or in combination of 2 or more.

Specific examples of the aromatic tetracarboxylic dianhydride include non-condensed polycyclic aromatic tetracarboxylic dianhydrides, monocyclic aromatic tetracarboxylic dianhydrides, and condensed polycyclic aromatic tetracarboxylic dianhydrides. Examples of the non-condensed polycyclic aromatic tetracarboxylic acid dianhydride include 4, 4 ' -oxydiphthalic anhydride (4, 4 ' -oxydiphthalic dianhydride), 3, 3 ', 4, 4 ' -benzophenone tetracarboxylic acid dianhydride, 2 ', 3, 3 ' -benzophenone tetracarboxylic acid dianhydride, 3, 3 ', 4, 4 ' -biphenyl tetracarboxylic acid dianhydride, 2 ', 3, 3 ' -biphenyl tetracarboxylic acid dianhydride, 3, 3 ', 4, 4 ' -diphenylsulfone tetracarboxylic acid dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4 ' - (hexafluoroisopropylidene) diphthalic dianhydride (4, 4 ' - (hexafluoroisopropylidene) dicarboxylic anhydride, which is sometimes referred to as 6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4 ' - (p-phenylenedioxy) diphthalic dianhydride, 4 ' - (m-phenylenedioxy)) diphthalic dianhydride. Further, as the monocyclic aromatic tetracarboxylic acid dianhydride, 1, 2, 4, 5-benzenetetracarboxylic acid dianhydride is exemplified, and as the condensed polycyclic aromatic tetracarboxylic acid dianhydride, 2, 3, 6, 7-naphthalenetetracarboxylic acid dianhydride is exemplified.

Of these, preferred examples include 4, 4 '-oxydiphthalic anhydride, 3, 3', 4, 4 '-benzophenonetetracarboxylic dianhydride, 2', 3, 3 '-benzophenonetetracarboxylic dianhydride, 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride, 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 3, 3', 4, 4 '-diphenylsulfonetetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, 2-bis (2, 3-dicarboxyphenyl) propane dianhydride, 2-bis (3, 4-dicarboxyphenoxyphenyl) propane dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (6FDA), 1, 2-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 1-bis (2, 3-dicarboxyphenyl) ethane dianhydride, 1, 2-bis (3, 4-dicarboxyphenyl) ethane dianhydride, 1-bis (3, 4-dicarboxyphenyl) ethane dianhydride, bis (3, 4-dicarboxyphenyl) methane dianhydride, bis (2, 3-dicarboxyphenyl) methane dianhydride, 4, 4 '- (terephthaloxy) diphthalic dianhydride and 4, 4' - (isophthaloxy) diphthalic dianhydride, more preferably 4, 4 '-oxybisphthalic anhydride, 3, 3', 4, 4 '-biphenyltetracarboxylic dianhydride, 2', 3, 3 '-biphenyltetracarboxylic dianhydride, 4, 4' - (hexafluoroisopropylidene) diphthalic dianhydride (6FDA), bis (3, 4-dicarboxyphenyl) methane dianhydride and 4, 4' - (p-phenylenedioxy) diphthalic dianhydride. These may be used alone or in combination of 2 or more.

Examples of the aliphatic tetracarboxylic dianhydride include cyclic and acyclic aliphatic tetracarboxylic dianhydrides. The cyclic aliphatic tetracarboxylic dianhydride is a tetracarboxylic dianhydride having an alicyclic hydrocarbon structure, and specific examples thereof include cycloalkanetetracarboxylic dianhydrides such as 1, 2, 4, 5-cyclohexanetetracarboxylic dianhydride, 1, 2, 3, 4-cyclobutanetetracarboxylic dianhydride and 1, 2, 3, 4-cyclopentanetetracarboxylic dianhydride, bicyclo [2.2.2] oct-7-ene-2, 3, 5, 6-tetracarboxylic dianhydride, dicyclohexyl-3, 3 ', 4, 4' -tetracarboxylic dianhydride and positional isomers thereof. These may be used alone or in combination of 2 or more. Specific examples of the acyclic aliphatic tetracarboxylic acid dianhydride include 1, 2, 3, 4-butanetetracarboxylic acid dianhydride, 1, 2, 3, 4-pentanetetracarboxylic acid dianhydride, and the like, and these can be used alone or in combination of 2 or more. In addition, cyclic aliphatic tetracarboxylic dianhydrides and acyclic aliphatic tetracarboxylic dianhydrides may be used in combination.

Among the tetracarboxylic acid compounds, the alicyclic tetracarboxylic acid dianhydride or non-condensed polycyclic aromatic tetracarboxylic acid dianhydride is preferably used from the viewpoint of easily improving the elastic modulus, the bending resistance, and the optical properties of the transparent resin film. More preferred examples thereof include 3, 3 ', 4, 4 ' -biphenyltetracarboxylic dianhydride, 2 ', 3, 3 ' -biphenyltetracarboxylic dianhydride, 2-bis (3, 4-dicarboxyphenyl) propane dianhydride, and 4, 4 ' - (hexafluoroisopropylidene) diphthalic dianhydride (6 FDA). These may be used alone or in combination of 2 or more.

The polyimide-based polymer according to the present embodiment may be obtained by further reacting tetracarboxylic acid, tricarboxylic acid compounds, dicarboxylic acid compounds, anhydrides thereof, and derivatives thereof in addition to the anhydrides of tetracarboxylic acid that can be used in the above-described polyimide synthesis, within a range that does not impair various physical properties of the obtained transparent resin film.

Examples of the tricarboxylic acid compound include an aromatic tricarboxylic acid, an aliphatic tricarboxylic acid, and an acyl chloride compound and an acid anhydride similar thereto, and 2 or more kinds thereof may be used in combination. Specific examples thereof includeAnhydride of 1, 2, 4-benzenetricarboxylic acid; 2, 3, 6-naphthalene tricarboxylic acid-2, 3-anhydride; phthalic anhydride and benzoic acid via a single bond, -CH₂-、-C(CH₃)₂-、-C(CF₃)₂-、-SO₂-or phenylene groups.

Examples of the dicarboxylic acid compound include aromatic dicarboxylic acids, aliphatic dicarboxylic acids, and the like, and acid chloride compounds and acid anhydrides thereof, and 2 or more of these may be used in combination. Specific examples thereof include terephthalic acid; isophthalic acid; naphthalenedicarboxylic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; dicarboxylic acid compound of chain hydrocarbon having 8 or less carbon atoms and 2 benzoic acid skeletons via-CH₂-、-S-、-C(CH₃)₂-、-C(CF₃)₂-、-O-、-NR⁹-、-C(＝O)-、-SO₂-or phenylene groups. These may be used alone or in combination of 2 or more. Here, R⁹Represents a hydrocarbon group having 1 to 12 carbon atoms which may be substituted with a halogen atom.

As the dicarboxylic acid compound, terephthalic acid is preferable; isophthalic acid; 4, 4' -biphenyldicarboxylic acid; 3, 3' -biphenyldicarboxylic acid; and 2 benzoic acid skeletons via-CH₂-、-C(＝O)-、-O-、-NR⁹-、-SO₂-or phenylene, more preferably terephthalic acid; 4, 4' -biphenyldicarboxylic acid; and 2 benzoic acid skeletons through-O-, -NR⁹A compound formed by linking-C (═ O) -or-SO 2-. These may be used alone or in combination of 2 or more.

The proportion of the tetracarboxylic acid compound relative to the total amount of the tetracarboxylic acid compound, the tricarboxylic acid compound and the dicarboxylic acid compound is preferably 40 mol% or more, more preferably 50 mol% or more, still more preferably 70 mol% or more, still more preferably 90 mol% or more, and particularly preferably 98 mol% or more.

Examples of the diamine that can be used for the synthesis of the polyimide-based polymer include aliphatic diamines, aromatic diamines, and mixtures thereof. In this embodiment, the "aromatic diamine" refers to a diamine in which an amino group is directly bonded to an aromatic ring, and may contain an aliphatic group or other substituent in a part of the structure. The aromatic ring may be a monocyclic ring or a condensed ring, and examples thereof include a benzene ring, a naphthalene ring, an anthracene ring, and a fluorene ring, but are not limited thereto. Among these, benzene rings are preferred. The "aliphatic diamine" refers to a diamine in which an amino group is directly bonded to an aliphatic group, and may contain an aromatic ring or other substituent in a part of the structure.

Specific examples of the aliphatic diamine include acyclic aliphatic diamines such as 1, 6-hexamethylenediamine and cyclic aliphatic diamines such as 1, 3-bis (aminomethyl) cyclohexane, 1, 4-bis (aminomethyl) cyclohexane, norbornanediamine and 4, 4' -diaminodicyclohexylmethane, and these can be used alone or in combination of 2 or more.

Specific examples of the aromatic diamine include aromatic diamines having 1 aromatic ring such as p-phenylenediamine, m-phenylenediamine, 2, 4-tolylenediamine, m-xylylenediamine, p-xylylenediamine, 1, 5-diaminonaphthalene, and 2, 6-diaminonaphthalene, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 3' -diaminodiphenyl ether, 4 '-diaminodiphenyl sulfone, 3' -diaminodiphenyl sulfone, 1, 4-bis (4-aminophenoxy) benzene, 1, 3-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, Bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 ' -dimethylbenzidine, 2 ' -bis (trifluoromethyl) -4, 4 ' -diaminobiphenyl (sometimes referred to as TFMB), aromatic diamines having 2 or more aromatic rings, such as 4, 4' -bis (4-aminophenoxy) biphenyl, 9-bis (4-aminophenyl) fluorene, 9-bis (4-amino-3-methylphenyl) fluorene, 9-bis (4-amino-3-chlorophenyl) fluorene, and 9, 9-bis (4-amino-3-fluorophenyl) fluorene. These may be used alone or in combination of 2 or more.

The aromatic diamine is preferably 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenylether, 3' -diaminodiphenylether, 4 '-diaminodiphenylsulfone, 3' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, bis [4- (3-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2-bis [4- (3-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4, 4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl, more preferably 4, 4 '-diaminodiphenylmethane, 4' -diaminodiphenylpropane, 4 '-diaminodiphenyl ether, 4' -diaminodiphenylsulfone, 1, 4-bis (4-aminophenoxy) benzene, bis [4- (4-aminophenoxy) phenyl ] sulfone, 2-bis [4- (4-aminophenoxy) phenyl ] propane, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4, 4 '-diaminobiphenyl (TFMB), 4' -bis (4-aminophenoxy) biphenyl. These may be used alone or in combination of 2 or more.

The diamine may have a fluorine-based substituent. Examples of the fluorine-based substituent include a perfluoroalkyl group having 1 to 5 carbon atoms such as a trifluoromethyl group and a fluorine group.

Among the above diamines, from the viewpoint of high transparency and low coloring property, 1 or more selected from the group consisting of aromatic diamines having a biphenyl structure is preferably used, and as a specific example, 1 or more selected from the group consisting of 2, 2 '-dimethylbenzidine, 2' -bis (trifluoromethyl) -4, 4 '-diaminobiphenyl (TFMB), and 4, 4' -bis (4-aminophenoxy) biphenyl is preferably used. Diamines having a biphenyl structure and a fluorine-based substituent are more preferable, and 2, 2 '-bis (trifluoromethyl) -4, 4' -diaminobiphenyl (TFMB) is more preferable as a specific example.

The polyimide-based polymer is a condensation-type polymer that is formed by polycondensation of a diamine and a tetracarboxylic acid compound (including a tetracarboxylic acid compound derivative such as an acid chloride compound or a tetracarboxylic acid dianhydride), and contains a repeating structural unit represented by formula (10). In addition to these, tricarboxylic acid compounds (including derivatives of tricarboxylic acid compounds such as acid chloride compounds and tricarboxylic anhydride) and dicarboxylic acid compounds (including derivatives such as acid chloride compounds) may be used as the starting materials. The polyamide is a condensation-type polymer containing a repeating structural unit represented by formula (13), which can be formed by condensation polymerization of a diamine and a dicarboxylic acid compound (including derivatives such as an acid chloride compound).

The repeating structural units represented by the formulae (10) and (11) may be generally derived from diamines and tetracarboxylic acid compounds. The repeating structural unit represented by formula (12) may be generally derived from diamine and tricarboxylic acid compounds. The repeating structural unit represented by formula (13) may be generally derived from diamine and dicarboxylic acid compounds. Specific examples of the diamine, the tetracarboxylic acid compound, the tricarboxylic acid compound and the dicarboxylic acid compound are as described above.

The molar ratio of the diamine to the carboxylic acid compound such as the tetracarboxylic acid compound is preferably adjusted within a range of 0.9mol or more and 1.1mol or less of the tetracarboxylic acid with respect to 1.00mol of the diamine. In order to exhibit high folding resistance, the polyimide-based polymer to be obtained is preferably high in molecular weight, and therefore, the tetracarboxylic acid is more preferably 0.98mol or more and 1.02mol or less, and still more preferably 0.99 mol% or more and 1.01 mol% or less, based on 1.00mol of the diamine.

In addition, from the viewpoint of suppressing the yellowness of the obtained transparent resin film, the proportion of the amino group in the obtained polymer terminal is preferably low, and 1.00mol or more of the carboxylic acid compound such as a tetracarboxylic acid compound is preferably 1.00mol or more based on 1.00mol of the diamine.

The amount of fluorine in the molecule of the diamine and the carboxylic acid compound (for example, tetracarboxylic acid compound) can be adjusted so that the amount of fluorine in the resulting polyimide polymer is 1 mass% or more, 5 mass% or more, 10 mass% or more, and 20 mass% or more, based on the mass of the polyimide polymer. Since the higher the fluorine content, the higher the raw material cost tends to be, the upper limit of the fluorine content is preferably 40 mass% or less. The fluorine-based substituent may be present in either one of the diamine and the carboxylic acid compound, or may be present in both of them. The inclusion of a fluorine-based substituent may particularly reduce the YI value.

The polyimide-based polymer according to the present embodiment may be a copolymer containing a plurality of different types of the above-described repeating structural units. The weight average molecular weight of the polyimide polymer is usually 100,000 to 800,000 in terms of standard polystyrene. The weight average molecular weight of the polyimide-based polymer is preferably 200,000 or more, more preferably 300,000 or more, and even more preferably 350,000 or more, because the flexibility in film formation is improved. In addition, from the viewpoint of obtaining a varnish having an appropriate concentration and viscosity and tending to improve film formability, 750,000 or less is preferable, 600,000 or less is more preferable, and 500,000 or less is even more preferable.

By including a fluorine-containing substituent in the polyimide-based polymer and the polyamide, the following tendency is exhibited: not only the elastic modulus at the time of forming a film is increased but also the YI value can be lowered. When the elastic modulus of the film is high, the occurrence of damage, wrinkles, and the like tends to be suppressed. The polyimide-based polymer and the polyamide preferably have a fluorine-containing substituent from the viewpoint of transparency of the film. Specific examples of the fluorine-containing substituent include a fluoro group and a trifluoromethyl group.

The content of fluorine atoms in the polyimide-based polymer and the mixture of the polyimide-based polymer and the polyamide is preferably 1% by mass or more and 40% by mass or less, and more preferably 5% by mass or more and 40% by mass or less, based on the mass of the polyimide-based polymer or the total of the mass of the polyimide-based polymer and the mass of the polyamide, respectively. When the content of fluorine atoms is 1% by mass or more, the YI value at the time of forming a film tends to be further reduced, and the transparency tends to be further improved. When the content of fluorine atoms is 40% by mass or less, the polyimide tends to have a high molecular weight.

In the present invention, the content of the polyimide-based polymer and/or polyamide in the resin composition forming the transparent resin film is preferably 40% by mass or more, more preferably 50% by mass or more, further preferably 70% by mass or more, and may be 100% by mass, relative to the solid content of the resin composition. When the content of the polyimide-based polymer and/or polyamide is not less than the lower limit, the flexibility of the transparent resin film is good. The solid content means the total amount of components remaining after the solvent is removed from the resin composition.

In the present invention, the resin composition for forming a transparent resin film may further contain an inorganic material such as inorganic particles in addition to the polyimide-based polymer and/or the polyamide. The inorganic material includes inorganic particles such as silica particles, titanium particles, aluminum hydroxide, zirconia particles, barium titanate particles, etc., and a silicon compound such as a 4-stage alkoxysilane such as tetraethylorthosilicate, etc., and from the viewpoint of stability of the varnish and dispersibility of the inorganic material, silica particles, aluminum hydroxide, zirconia particles, etc., are preferable, and silica particles are more preferable.

The inorganic material preferably has an average primary particle diameter of 1 to 200nm, more preferably 3 to 100nm, further preferably 5 to 50nm, and further more preferably 5 to 30 nm. When the average primary particle diameter is 100nm or less, the transparency tends to be improved. When the average primary particle diameter is 10nm or more, the inorganic material tends to be easily handled because of weak cohesive force.

In the present invention, the silica particles may be a silica sol in which silica particles are dispersed in an organic solvent or the like, or a silica fine particle powder produced by a vapor phase method may be used, and a silica sol produced by a liquid phase method is preferable from the viewpoint of easy handling.

The average primary particle diameter of the silica particles in the transparent resin film can be determined by observation with a Transmission Electron Microscope (TEM). The particle size distribution of the silica particles before forming the transparent resin film can be determined by a commercially available laser diffraction particle size distribution meter.

In the present invention, the content of the inorganic material in the resin composition is preferably 0 mass% or more and 90 mass% or less with respect to the solid content of the resin composition. More preferably 10% by mass or more and 60% by mass or less, and still more preferably 20% by mass or more and 50% by mass or less. When the content of the inorganic material in the resin composition is within the above range, the transparency and the mechanical strength of the transparent resin film tend to be easily achieved at the same time. The solid content means the total amount of components remaining after the solvent is removed from the resin composition.

The resin composition for forming a transparent resin film may further contain other components in addition to the components described above. Examples of the other components include an antioxidant, a release agent, a light stabilizer, a bluing agent, a flame retardant, a lubricant, and a leveling agent.

In the present invention, when the resin composition contains other components than the resin component such as a polyimide-based polymer and the inorganic material, the content of the other components is preferably 0% by mass or more and 20% by mass or less, and more preferably 0% by mass or more and 10% by mass or less, based on the total mass of the transparent resin film.

In the present invention, the transparent resin film can be produced, for example, from the following resin varnish, which can be prepared by: a solvent is added to a resin composition containing a reaction solution of a polyimide polymer and/or a polyamide obtained by selecting and reacting the tetracarboxylic acid compound, the diamine, and the other raw materials, an inorganic material used as needed, and other components, and the mixture is mixed and stirred. In the resin composition or the resin varnish, a solution of a commercially available polyimide polymer or the like or a solution of a commercially available solid polyimide polymer or the like may be used instead of the reaction solution of a polyimide polymer or the like.

As a solvent that can be used for preparing the resin varnish, a solvent that can dissolve or disperse a resin component such as a polyimide-based polymer can be appropriately selected. The solvent may be used alone in 1 kind, or in combination of 2 or more kinds. When 2 or more solvents are used, the kind of the solvent is preferably selected so that the boiling point of the solvent having the highest boiling point among the solvents used falls within the above range. From the viewpoint of solubility, coatability, drying properties and the like of the resin component, an organic solvent having a boiling point of 120 to 300 ℃ is preferable, and an organic solvent having a boiling point of 120 to 270 ℃ is more preferable, 120 to 250 ℃ is even more preferable, and 120 to 230 ℃ is particularly preferable. Specific examples of such organic solvents include amide solvents such as N, N-dimethylformamide, N-dimethylacetamide, and N-methylpyrrolidone; lactone solvents such as γ -butyrolactone and γ -valerolactone; ketone solvents such as cyclohexanone, cyclopentanone, and methyl ethyl ketone; acetate solvents such as butyl acetate and amyl acetate; sulfur-containing solvents such as dimethyl sulfone, dimethyl sulfoxide and sulfolane, and carbonate solvents such as ethylene carbonate and 1, 2-propylene carbonate. Among them, from the viewpoint of excellent solubility in the polyimide-based polymer and polyamide, a solvent selected from the group consisting of N, N-dimethylacetamide (boiling point: 165 ℃ C.), γ -butyrolactone (boiling point: 204 ℃ C.), N-methylpyrrolidone (boiling point: 202 ℃ C.), cyclopentanone (boiling point: 131 ℃ C.), butyl acetate (boiling point: 126 ℃ C.) and amyl acetate (boiling point: 149 ℃ C.) is preferable.

The amount of the solvent is not particularly limited, and may be selected so as to have a viscosity capable of handling the resin varnish, and is, for example, preferably 50 to 95% by mass, more preferably 70 to 95% by mass, and still more preferably 80 to 95% by mass, based on the total amount of the resin varnish.

The content of the solvent in the transparent resin film constituting the laminate of the present invention is required to be within a range that satisfies a predetermined relationship in the relationship between the residual solvent amount S (mass%) calculated as the mass reduction rate from 120 ℃ to 250 ℃ obtained by thermogravimetric-differential thermal measurement and the low molecular weight component amount W (%) in the protective film described later. In the present invention, the amount S of the residual solvent in the transparent resin film may be appropriately adjusted based on the relationship with the amount W of the low-molecular weight component in the protective film to be bonded, and is preferably 20% by mass or less, more preferably 17% by mass or less, and still more preferably 15% by mass or less. When the residual solvent amount S is not more than the above upper limit, the obtained transparent resin film can be formed as a free-standing film. The lower limit of the amount S of the residual solvent is not particularly limited, but in the production of a transparent resin film containing a polyimide-based polymer or a polyamide as a resin component, a high boiling point solvent having a boiling point higher than 100 ℃ is generally used as described above, and therefore, it is difficult to completely remove the solvent in the production process, and the amount S is usually 0.001 mass% or more. From the viewpoint of bendability, the amount is preferably 0.005% by mass or more, more preferably 0.01% by mass or more, still more preferably 0.1% by mass or more, and still more preferably 0.5% by mass or more.

In the present invention, the residual solvent amount S is a value calculated as follows: the measurement was carried out using a thermogravimetric-differential thermal (TG-DTA) measurement apparatus, and the mass loss rate S (mass%) from 120 ℃ to 250 ℃ was calculated according to the relational expression (2) from the results of measuring the mass change obtained by raising the temperature of a transparent resin film (sample) to be measured from room temperature to 120 ℃ at a temperature raising rate of 10 ℃/min and holding the film at 120 ℃ for 5 minutes to remove adsorbed water and then raising the temperature (heating) to 400 ℃ at a temperature raising rate of 10 ℃/min.

S (% by mass) 100- (W1/W0) × 100 (2)

In the formula (2), W0 represents the mass of the sample after being held at 120 ℃ for 5 minutes, and W1 represents the mass of the sample at 250 ℃ in the measurement with the thermogravimetric-differential thermal measurement apparatus.

The residual solvent amount S can be controlled by adjusting the amount of solvent contained in the resin varnish for forming the transparent resin film, the type of solvent, and the drying conditions (drying temperature, time, wind speed, and the like) of the coating film formed from the resin varnish.

The thickness of the transparent resin film may be determined as appropriate depending on the use of the transparent resin film, and is usually 10 to 500. mu.m, preferably 15 to 200. mu.m, and more preferably 20 to 100. mu.m. When the thickness of the transparent resin film is within the above range, the flexibility of the transparent resin film is good.

The laminate of the present invention includes a protective film bonded to the transparent resin film. The protective film may be attached to only one surface of the transparent resin film, or may be attached to both surfaces. The protective film to be bonded to the transparent resin film is generally a film for temporarily protecting the surface of the transparent resin film, and is not particularly limited as long as it is a peelable film capable of protecting the surface of the transparent resin film, and is preferably selected from the group consisting of polyolefin resin films such as polyethylene and polypropylene films. When the protective films are bonded to both surfaces of the transparent resin film, the protective films may be the same or different from each other.

In the laminate of the present invention, the protective film may be composed of a base film and a pressure-sensitive adhesive layer formed of, for example, an acrylic pressure-sensitive adhesive, an epoxy pressure-sensitive adhesive, a urethane pressure-sensitive adhesive, a silicone pressure-sensitive adhesive, or the like, laminated thereon, and a resin film having self-adhesiveness such as a polyolefin resin is preferable from the viewpoint of suppressing contamination of the surface of the transparent resin film as much as possible.

In addition, it is considered that whitening of the transparent resin film, which is the subject of the present invention, occurs due to elution of low-molecular components contained in the protective film into a solvent used in the production of the transparent resin film containing a polyimide-based polymer and a polyamide as resin components. In the protective film generally used in the field of the laminate, since the polyolefin resin film tends to contain a large amount of low-molecular components, the effect of the present invention of suppressing whitening of the transparent resin film can be obtained particularly advantageously in a laminate using the polyolefin resin film as the protective film. Therefore, in a preferred embodiment of the present invention, the protective film used for the laminate of the present invention is a polyolefin resin film, and is more preferably a polypropylene resin film or a polyethylene resin film, and even more preferably a polyethylene resin film, from the viewpoint of easy availability and low cost. Examples of the polyethylene resin include high-pressure low-density polyethylene (LDPE), linear short-chain branched polyethylene (LLDPE), medium-low pressure high-density polyethylene (HDPE), and very low-density polyethylene (VLDPE), and the LLDPE is preferable as the resin on the surface adjacent to the transparent resin film from the viewpoint of adhesiveness to the transparent resin film and processability. When the protective films are bonded to both surfaces of the transparent resin film, the protective films may be the same or different from each other on each surface, and the protective film bonded to at least one surface is preferably a polyolefin resin film.

Here, in the present invention, the "low molecular component" contained in the protective film means a component detected in a range of Log M of a spectrum measured by gel permeation chromatography at a measurement temperature of 140 ℃ in the range of 2.82 to 3.32 under the following conditions.

< measurement conditions for gel permeation chromatography >

Column: 1 PLgel Indvidual (5 μm, 50.)

7.5mm ID. times.30 cm, manufactured by Agilent Technologies), and 2 TSKgel GMH_HRH (S) HT (7.5mm ID. times.30 cm, manufactured by TOSOH Co., Ltd.) ligation

Mobile phase: 0.1 w/V% BHT (di-tert-butylhydroxytoluene) was added to o-dichlorobenzene (Special grade, Wako pure chemical industries, Ltd.) and used

Flow rate: 1 mL/min

Temperature of the column oven: 140 deg.C

Autosampler temperature: 140 deg.C

Temperature of a system oven: 40 deg.C

And (3) detection: differential Refractive Index Detector (RID)

RID cell temperature: 140 deg.C

Injection amount of sample solution: 300 μ L

Standard substance solution for GPC column calibration: standard polystyrene manufactured by TOSOH

More detailed measurement conditions of gel permeation chromatography are described in examples described later.

Specifically, the low-molecular component is considered to be a component derived from residual monomers, oligomers, additives, film raw materials, and the like contained in the protective film or in the adhesive layer in the case where the protective film is formed of the base film and the adhesive layer laminated thereon. Examples of the low-molecular-weight component contained in the protective film include components derived from nucleating agents, antioxidants, hydrochloric acid absorbents, heat stabilizers, light stabilizers, ultraviolet absorbers, lubricants, antiblocking agents, antistatic agents, flame retardants, pigments, dyes, dispersants, copper harm inhibitors, neutralizers, foaming agents, plasticizers, bubble inhibitors, fluidity improvers such as crosslinking agents and peroxides, and weld strength improvers; examples of the low-molecular weight component contained in the pressure-sensitive adhesive layer laminated on the protective film include components derived from an adhesion-imparting resin, a softening agent, and the like.

In the present invention, the content of the low-molecular component contained in the protective film must be in a range that satisfies a predetermined relationship in the relationship between the amount of the low-molecular component W (%) (defined as the ratio of the area where Log M in a graph measured by gel permeation chromatography at a measurement temperature of 140 ℃ according to the measurement conditions of the above-described gel permeation chromatography is 2.82 to 3.32 with respect to the total area) and the amount of the residual solvent S (mass%) in the transparent resin film described later. In the present invention, the amount of the low-molecular weight component W in the protective film may be appropriately adjusted based on the relationship with the amount S of the residual solvent in the transparent resin film to be bonded, and is preferably 1% or less, more preferably 0.8% or less, further preferably 0.5% or less, and particularly preferably 0.33% or less. When the amount W of the low-molecular component is not more than the above upper limit, the transfer of the low-molecular component contained in the protective film to the transparent resin film is less likely to occur, and the protective film is suitable as a protective film for protecting the surface of the transparent resin film for optical use. The lower limit of the amount W of the low-molecular weight component is not particularly limited, but the protective film used in the field of the optical laminate generally contains a low-molecular weight component derived from the additives and raw materials as exemplified above, and therefore is generally 0.00001% or more, preferably 0.001% or more, more preferably 0.01% or more, and further preferably 0.02% or more.

The thickness of the protective film is not particularly limited, and is usually 10 μm or more, preferably 20 μm or more, and more preferably 25 μm or more, from the viewpoint of protecting the transparent resin film. On the other hand, from the viewpoint of film handling, it is preferably 300 μm or less. When the protective films are bonded to both surfaces of the transparent resin film, the thicknesses of the protective films on the respective surfaces may be the same or different.

In the present invention, the transparent resin film and the protective film are combined so that the residual solvent amount S (mass%) of the transparent resin film constituting the laminate and the low molecular weight component amount W (%) of the protective film bonded to the transparent resin film satisfy the relational expression (1).

S×W≤4.7 (1)

From the viewpoint of whitening suppression effect, the value of S × W (hereinafter, also referred to as "the value of formula (1)) in the laminate of the present invention is preferably 4.5 or less, more preferably 4.0 or less, further preferably 3.5 or less, further more preferably 3.4 or less, particularly preferably 3.3 or less, further particularly preferably 2.0 or less, particularly preferably 0.5 or less, and particularly preferably 0.4 or less.

In addition, it is preferable to combine the transparent film with the protective film so that S and W satisfy the relational expression (1'). The value of sxw in the laminate of the present invention (hereinafter, also referred to as "the value of formula (1')) is preferably 0.007 or more.

0.005≤S×W (1’)

When the protective films are bonded to both surfaces of the transparent resin film, the low-molecular-weight component amount W of each protective film preferably satisfies the above-described equations (1) and (1') in relation to the residual solvent amount S of the transparent resin film.

The value of equation (1) can be controlled by: selecting a protective film having a small amount of low-molecular components when a transparent resin film having a large amount of residual solvent is used, and selecting a transparent resin film having a small amount of residual solvent when a protective film having a large amount of low-molecular components is used; and so on.

The laminate of the present invention has an excellent effect of suppressing whitening on the surface of the transparent resin film to which the protective film is bonded by controlling the amount of the residual solvent of the transparent resin film and the amount of the low-molecular-weight component of the protective film. Therefore, the transparent resin film constituting the laminate of the present invention has excellent transparency, and the haze thereof is preferably 1.0% or less, more preferably 0.7% or less, and further preferably 0.5% or less. The transparent resin film constituting the laminate of the present invention preferably has a total light transmittance of 85% or more, more preferably 87% or more, and even more preferably 90% or more. The yellowness of the transparent resin film constituting the laminate of the present invention is preferably 3.0 or less, more preferably 2.5 or less, and still more preferably 2.2 or less. When the haze and the total light transmittance of the transparent resin film constituting the laminate are within the above ranges, a laminate suitable for optical applications requiring high transparency will be formed. The laminate of the present invention is also suitable for optical applications because the transparent resin film has a low yellowness and is suppressed in coloration. The "whitening of the transparent resin film" in the present invention is a phenomenon that can be recognized by a high-luminance lamp having an irradiation luminous flux of 3000 lumens, as described in examples described later, and the occurrence of the "whitening" does not necessarily directly affect the haze and the total luminous transmittance of the transparent resin film. Since the transparent resin film used after the protective film is peeled from the laminate of the present invention is less likely to cause whitening on the film surface and has excellent transparency, when this transparent resin film is used, for example, a certain luminance can be easily ensured and the emission intensity of a display element or the like can be suppressed as compared with the case of using a resin film having a low transmittance. Therefore, power consumption can be reduced.

The laminate of the present invention can be produced by laminating a transparent resin film and a protective film by a known method and apparatus/equipment. Specifically, for example, the present invention can be manufactured by a method including the steps of:

coating a resin varnish obtained by mixing and stirring a resin composition for forming a transparent resin film and a solvent on a support base;

forming a layer of a transparent resin film on the support substrate by drying the coated resin varnish to remove the solvent;

bonding a protective film to a surface of a transparent resin film formed on a support base material, the surface being opposite to the support base material; and the number of the first and second groups,

the support base is peeled from the layer of the transparent resin film formed on the support base.

For example, when a transparent resin film is continuously produced by a method including a step of applying a resin varnish containing a solvent to form a film and then removing the solvent by drying, such as a casting method, it is difficult to completely remove the solvent by drying, and the transparent resin film is often used in a subsequent step while the solvent remains in a state of being left in the transparent resin film, and whitening is likely to occur when a protective film is attached. Even in such a case, the whitening on the surface of the transparent resin film to which the protective film is bonded can be easily and effectively suppressed by selecting the protective film so as to satisfy the relationship of the above expression (1) in accordance with the amount of the residual solvent in the transparent resin film, and by controlling the drying condition of the transparent resin film so as to satisfy the relationship of the above expression (1) in accordance with the amount of the low-molecular component of the protective film to be used. Further, the above formula (1') is preferably satisfied.

In the case of producing the laminate of the present invention by the above method, the support base to which the resin varnish is applied is a film-like base, and may be, for example, a resin film base or a steel base (e.g., SUS tape). As the resin film substrate, for example, a polyethylene terephthalate (PET) film is available. The thickness of the supporting substrate is not particularly limited, but is, for example, 10 to 500. mu.m, preferably 50 to 300. mu.m.

In the drying step of the coating film, the solvent is preferably removed by drying so that the solvent in the resin varnish falls within a desired range. The drying for removing the solvent may be performed by natural drying, air drying, heat drying or reduced pressure drying, and a combination thereof. From the viewpoint of production efficiency, etc., heat drying is preferable. The drying conditions may be appropriately determined within a range not to impair the optical properties of the transparent resin film, depending on the kind of solvent used, the solvent content in the film, and the like. For example, the heating may be performed at a temperature of 50 to 300 ℃, preferably 70 to 250 ℃, for about 5 to 100 minutes.

Next, a protective film having a low molecular weight satisfying the relationship of the above formula (1) is laminated on the surface of the transparent resin film opposite to the support base material to obtain a laminated film in which a layer of the transparent resin film is formed on the support base material and a protective film is further laminated on the layer of the transparent resin film. Then, the support base is peeled off from the layer of the transparent resin film, whereby a laminated film in which a protective film is laminated on the transparent resin film can be obtained. If necessary, a protective film may be attached to the surface of the transparent resin film from which the support base material has been peeled.

The laminate of the present invention can suppress whitening on the surface of the transparent resin film to which the protective film is attached, and has high transparency and good appearance, and therefore, is particularly suitable for optical applications such as displays of various image display devices.

Examples

The present invention will be described in further detail below with reference to examples. Unless otherwise specified, "%" and "parts" in the examples are mass% and parts by mass. The residual solvent amount of the transparent resin film used in examples and comparative examples and the low-molecular weight component amount of the protective film were measured and calculated by the following methods.

< method for measuring residual solvent amount S >

Thermogravimetric-differential thermal (TG-DTA) assay

TG/DTA6300 manufactured by Hitachi High-Tech Science Corporation was used as a TG-DTA measuring device. About 20mg of a sample was obtained from the prepared transparent polyimide film. The sample was heated from room temperature to 120 ℃ at a heating rate of 10 ℃/min, and after being held at 120 ℃ for 5 minutes, the sample was heated (heated) to 400 ℃ at a heating rate of 10 ℃/min, and the change in mass of the sample was measured. FIG. 1 shows the results of TG-DTA measurement of a transparent polyimide film produced in example 1 described later.

From the results of TG-DTA measurement, the mass loss rate S (% by mass) from 120 ℃ to 250 ℃ was calculated by the following equation (2).

S (% by mass) 100- (W1/W0) × 100 (2)

In the formula (2), W0 represents the mass of the sample after being held at 120 ℃ for 5 minutes, and W1 represents the mass of the sample at 250 ℃.

The calculated mass reduction rate S was defined as the amount of residual solvent S (mass%) in the transparent resin film.

< method for measuring amount of Low molecular weight component >

The low molecular weight component was determined by Gel Permeation Chromatography (GPC). The GPC measurement was performed under the following conditions. The low molecular weight component was determined by Gel Permeation Chromatography (GPC). The obtained chromatogram was plotted by plotting an electric signal value (intensity Y) derived from the difference in refractive index between the test solution and the reference solution against the molecular weight Log M in terms of polystyrene. In this figure, a line connecting points where Log M is 2.82 and 7.61 is defined as a base line. The portion where the intensity Y value corrected by the baseline becomes a negative value is 0.

(1) Conditions for sample solution preparation

Solvent: 0.1 w/V% BHT (di-tert-butylhydroxytoluene) was added to o-dichlorobenzene (Special grade, Wako pure chemical industries, Ltd.) and used

Concentration of sample solution: 1mg/mL

Automatic oscillator for dissolution: DF-8020 (manufactured by TOSOH corporation)

Dissolution conditions: a5 mg sample was sealed in a 1000 mesh SUS-made mesh bag, the mesh bag in which the sample was sealed was placed in a test tube, and 5mL of a solvent was added to the test tube. Next, a test tube capped with aluminum foil was placed on DF-8020 and stirred at 140 ℃ for 120 minutes at a stirring speed of 60 round trips/minute.

(2) Measurement conditions

(GPC apparatus and software)

A measuring device: HLC-8121GPC/HT (manufactured by TOSOH corporation)

Measurement software: GPC-8020 model II data Collection version 4.32 (manufactured by TOSOH Co., Ltd.)

Analysis software: GPC-8020 Pattern II data analysis version 4.32 (manufactured by TOSOH Co., Ltd.)

(measurement conditions)

GPC column: 1 PLgel Indvidual (5 μm, 50.)

Mobile phase: 0.1 w/V% BHT was added to o-dichlorobenzene (Special grade manufactured by Wako pure chemical industries, Ltd.) and used

Flow rate: 1 mL/min

Temperature of the column oven: 140 deg.C

Autosampler temperature: 140 deg.C

Temperature of a system oven: 40 deg.C

And (3) detection: differential Refractive Index Detector (RID)

RID cell temperature: 140 deg.C

Injection amount of sample solution: 300 μ L

Standard substance solution for GPC column calibration: TOSOH (strain) was weighed to prepare standard polystyrene, 5mL of o-dichlorobenzene (same composition as the mobile phase) was added thereto, and the polystyrene was completely dissolved at room temperature to prepare a solution

[ Table 1]

Test tube 1	F700 0.4mg	F20 0.9mg	A5000 1.2mg
				Test tube 2	F288 0.4mg	F10 1.0mg	A2500 1.2mg
Test tube 3	F80 0.7mg	F4 1.1mg	A1000 1.3mg
				Test tube 4	F40 0.8mg	F2 1.1mg	A500 1.3mg

From the GPC measurement result, the low molecular weight component W (%) was calculated by the relational expression (3).

W(％)＝V0/V1 (3)

In the formula (3), V0 represents an area of 2.82 to 3.32 in Log M and V1 represents an area of the whole spectrum, which are measured by GPC.

< method for measuring elastic modulus >

The transparent resin films obtained in examples and comparative examples were dried at 200 ℃ for 20 minutes and cut into strips of 10mm × 100mm using a dumbbell cutter, to obtain samples. The elastic modulus of this sample was measured by using an automatic plotter (Autograph) AG-IS (manufactured by Shimadzu corporation) under conditions of a chuck-to-chuck distance of 500mm and a stretching speed of 20 mm/min, and the elastic modulus of the optical film was calculated from the slope thereof.

< method for measuring Total light transmittance >

The transparent resin films obtained in examples and comparative examples were cut into a size of 30mm × 30mm, and the total light transmittance (%) of the optical film at a thickness of 50 μm was measured using a haze computer (Suga Test Instruments co., ltd., "HGM-2 DP").

< method for measuring haze value >

The transparent resin films obtained in examples and comparative examples were cut into a size of 30mm × 30mm, and the haze (%) was measured using a haze computer (Suga Test Instruments co., ltd., "HGM-2 DP").

< method for measuring yellowness >

The transparent resin films obtained in examples and comparative examples were cut into a size of 30mm × 30mm, and the tristimulus values (X, Y, Z) were obtained using an ultraviolet-visible near-infrared spectrophotometer (V-670, manufactured by Nippon Denshoku Co., Ltd.) and substituted into the formula (4) to calculate the YI value.

YI＝100×(1.2769X-1.0592Z)/Y (4)

Production example 1: preparation of transparent polyimide-based Polymer

A reactor having a separable flask equipped with a silicone tube, a stirrer, and a thermometer, and an oil bath were prepared. Into the flask were charged 75.52g of 4, 4 ' - (hexafluoroisopropylidene) diphthalic anhydride (6FDA) and 54.44g of 2, 2 ' -bis (trifluoromethyl) -4, 4 ' -diaminobiphenyl (TFMB). While stirring at 400rpm, 519.84g of N, N-dimethylacetamide (DMAc) was added, and the stirring was continued until the content of the flask became a uniform solution. Then, the stirring was continued for a further 20 hours while adjusting the temperature in the vessel to 20 to 30 ℃ by using an oil bath, and the reaction was carried out to produce polyamic acid. After 30 minutes, the stirring speed was changed to 100 rpm. After stirring for 20 hours, the reaction system was returned to room temperature, and DMAc 649.8g was added to adjust the polymer concentration to 10% by weight. Further, 32.27g of pyridine and 41.65g of acetic anhydride were added thereto, and the mixture was stirred at room temperature for 10 hours to effect imidization. The polyimide varnish was taken out of the reaction vessel. The obtained polyimide varnish was dropped into methanol to reprecipitate, and the obtained powder was heated and dried to remove the solvent, thereby obtaining a transparent polyimide polymer as a solid. The weight average molecular weight of the resulting polyimide polymer was 360,000 as measured by GPC.

Production example 2: preparation of transparent polyamideimide-based Polymer

50g (156.13mmol) of TFMB and 642.07g of DMAc were added to a 1L separable flask equipped with a stirring blade under a nitrogen atmosphere, and the TFMB was dissolved in the DMAc while stirring at room temperature. Subsequently, 6FDA20.84g (46.91mmol) was added to the flask, and the mixture was stirred at room temperature for 3 hours. Subsequently, 9.23g (31.27mmol) of 4, 4' -oxybis (benzoyl chloride) (OBBC) was added to the flask, and then 15.87g (78.18mmol) of terephthaloyl chloride (TPC) was added thereto, followed by stirring at room temperature for 1 hour. Then, 9.89g (106.17mmol) of 4-methylpyridine and 14.37g (140.73mmol) of acetic anhydride were added to the flask, and the mixture was stirred at room temperature for 30 minutes, then heated to 70 ℃ using an oil bath, and further stirred for 3 hours to obtain a reaction solution.

The obtained reaction solution was cooled to room temperature, put into a large amount of methanol in a linear form, and the precipitated precipitate was taken out, immersed in methanol for 6 hours, and then washed with methanol. Then, the precipitate was dried under reduced pressure at 100 ℃ to obtain a transparent polyamideimide polymer. The polyamideimide polymer thus obtained was subjected to GPC measurement, and the weight average molecular weight was 420,000.

Production example 3: preparation of silica sols

Gamma-butyrolactone (hereinafter, also referred to as GBL) substituted silica sol was prepared by using as a raw material amorphous silica sol (amophorus silica sol) having a BET diameter (average primary particle diameter measured by the BET method) of 27nm prepared by a sol-gel method, and by solvent substitution. The obtained sol was filtered through a membrane filter having a mesh size of 10 μm to obtain a GBL-substituted silica sol. The silica particles in the GBL substituted silica sol obtained are all 30-32 mass%.

Example 1: production of laminate

The transparent polyimide polymer obtained in production example 1 was dissolved at a concentration of 16.5% in a mixed solvent in which GBL and DMAc were mixed at a ratio of 1: 9 to obtain a resin varnish. The obtained resin varnish was applied to a polyethylene terephthalate (PET) film substrate (188 μm thick, product name: Cosmo Shine (registered trademark) a4100, manufactured by tokyo corporation) by tape casting to form a film. Thereafter, the coating film was dried by heating at 50 ℃ for 30 minutes and at 140 ℃ for 10 minutes, and the PET substrate was peeled off from the coating film. Thereafter, the resultant was heated at 200 ℃ for 12 minutes, thereby obtaining a transparent resin film having a thickness of about 80 μm. The residual solvent content of the obtained transparent resin film was 1 mass%. The obtained transparent resin film had a total light transmittance of 92.5%, a haze of 0.3%, a yellowness index of 2.1 and an elastic modulus of 4 GPa.

Next, Toretec (registered trademark) N-711 manufactured by ltd was prepared as a protective film by TORAY ADVANCED FILM co. The amount of the low molecular weight component in the protective film was 0.33%. The transparent resin film thus produced was bonded to a roll to produce a laminate.

< evaluation of whitening >

Whitening of the obtained transparent resin film was confirmed.

The laminate produced in example 1 was left to stand in an environment at a temperature of 23 ℃ and a humidity of 50% for 24 hours. Thereafter, the bonded protective film was peeled off, and the surface of the transparent resin film bonded with the protective film was wiped with a cleaning cloth sheet. Thereafter, the film appearance (whitening) was evaluated using a high-brightness lamp having a luminous flux of 3,000 lumens according to the following evaluation criteria. The results are shown in Table 2.

< evaluation criteria for whitening >

○ No whitening confirmation

X: whitening was observed on the surface of the transparent resin film

Example 2

The transparent polyimide polymer obtained in production example 1 was dissolved at a concentration of 16.5% in a mixed solvent in which GBL and DMAc were mixed at a ratio of 1: 9 to obtain a resin varnish. The obtained resin varnish was applied to a PET film substrate (188 μm thick, product name: Cosmo Shine A4100, manufactured by Toyo Boseki Co., Ltd.) by casting to form a film. Thereafter, the coating film was dried by heating at 50 ℃ for 30 minutes and at 140 ℃ for 10 minutes, and the PET substrate was peeled off from the coating film to obtain a transparent resin film having a thickness of 80 μm. The residual solvent content of the obtained transparent resin film was 10 mass%. A laminate was obtained in the same manner as in example 1, except that this was used as a transparent resin film.

The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 3

A laminate was obtained in the same manner as in example 1, except that Toretec 7832C (TORAY ADVANCED FILM co., ltd., low molecular weight component: 0.48%) was used as the protective film. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 4

A laminate was obtained in the same manner as in example 2 except that Toray BO 25-MK01 (manufactured by Toray Co., Ltd., amount of low molecular weight component: 0.04%) was used as the protective film. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 5

A laminate was obtained in the same manner as in example 2, except that the transparent polyamideimide polymer obtained in the above production example 2 was dissolved in a DMAc solvent at a concentration of 10% to obtain a resin varnish. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 6

The transparent polyamideimide polymer obtained in production example 2 was dissolved in GBL, and GBL-substituted silica sol obtained in production example 3 was added thereto and sufficiently mixed to obtain a transparent polyamideimide polymer/silica particle mixed varnish (hereinafter, sometimes referred to as mixed varnish) having a composition shown in table 2. At this time, a mixed varnish was prepared so that the concentration of the polyamideimide polymer/silica particles (concentration based on the total mass of the resin and the silica particles) became 10 mass%. Then, the obtained mixed varnish was applied to a polyethylene terephthalate (PET) film substrate (188 μm thick, product name: Cosmo Shine A4100, Toyo Boseki Co., Ltd.) by tape casting to form a film. Thereafter, the coating film was dried by heating at 50 ℃ for 30 minutes and at 140 ℃ for 10 minutes, and the PET substrate was peeled off from the coating film to obtain a transparent resin film having a thickness of 50 μm. The residual solvent content of the obtained transparent resin film was 14 mass%. A laminate was obtained in the same manner as in example 1, except that this was used as a transparent resin film. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 7

The transparent polyamideimide polymer obtained in production example 2 was dissolved in DMAc at a concentration of 12% to obtain a resin varnish. A laminate was obtained in the same manner as in example 2, except that the drying conditions of the coating film were changed to 70 ℃ for 30 minutes and 140 ℃ for 15 minutes. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Example 8

A laminate was obtained in the same manner as in example 1, except that the PET substrate was peeled off from the coating film and then heated at 200 ℃ for 14 hours. The thickness of the obtained transparent resin film was 79 μm, and the residual solvent content was 0.024 mass%. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Comparative example 1

A laminate was obtained in the same manner as in example 2, except that Toretec 7832C (TORAY ADVANCED FILM co., ltd., low molecular weight component: 0.48%) was used as the protective film. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

Comparative example 2

A laminate was obtained in the same manner as in example 6, except that Toretec 7832C (TORAY ADVANCED FILM co., ltd., low molecular weight component: 0.48%) was used as the protective film. The appearance (whitening) of the film was evaluated in the same manner as in example 1. The results are shown in Table 2.

[ Table 2]

Claims

1. A laminate comprising a transparent resin film and a protective film bonded to at least one surface of the transparent resin film, wherein the transparent resin film comprises 1 or more kinds of solvents and at least 1 kind selected from the group consisting of polyimide, polyamide and polyamideimide, and is produced by a casting method using the 1 or more kinds of solvents,

the boiling point of the solvent with the highest boiling point in the more than 1 solvents is 120-300 ℃,

a residual solvent amount S (mass%) of the transparent resin film calculated as a mass reduction rate from 120 ℃ to 250 ℃ obtained by thermogravimetry-differential thermal (TG-DTA) measurement and a low molecular component amount W (%) of the protective film defined as a ratio of an area where Log M in a graph measured at a measurement temperature of 140 ℃ by gel permeation chromatography is 2.82 to 3.32 with respect to a total area satisfy a relational expression (1),

S×W≤4.7 (1)，

s is 0.01 mass% or more and W is 1% or less.

2. The laminate of claim 1, wherein S and W satisfy the relationship (1'):

0.005≤S×W (1’)。

3. the laminate according to claim 1 or 2, wherein the transparent resin film has a haze of 1.0% or less.

4. The laminate according to any one of claims 1 to 3, wherein the transparent resin film has a total light transmittance of 85% or more.

5. The laminate according to any one of claims 1 to 4, wherein the transparent resin film comprises at least 1 solvent selected from the group consisting of N, N-dimethylacetamide, γ -butyrolactone, N-methylpyrrolidone, cyclopentanone, butyl acetate, and amyl acetate.

6. The laminate according to any one of claims 1 to 5, wherein the protective film is a polyolefin resin film.