Polycarbonate resin film and cover window for flexible display device using same

Abstract

To provide a film composed of a polycarbonate resin which is excellent in transparency, heat resistance, bending resistance and pencil hardness, and a cover window of a flexible display device using the same.SOLUTION: There is provided a film, wherein a main repeating unit includes a repeating unit (A) derived from 2,2-bis(4-hydroxy-3-methylphenyl)propane, and a repeating unit (B) derived from 2,2-bis(4-hydroxyphenyl)propane, wherein the content of the repeating unit (A) is 40-100 mol%, the content of the repeating unit (B) is 0-60 mol%, and a relation between a viscosity average molecular weight (V) of a polycarbonate resin and a content (W mol%) of the repeating unit (A) satisfies the following expression (4): V≥80W+20,000.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a film made of polycarbonate resin and a cover window for a flexible display device using the same. [Background technology]

[0002] Glass has traditionally been used as a material for transparent components such as the substrate and front panel of various display components, including solar cells and displays. However, glass has drawbacks such as being easily broken and heavy. Furthermore, glass has not been adequately suited to the recent trend toward thinner, lighter, and more flexible displays. Therefore, polyimide-based films, which offer excellent heat resistance and flex resistance, have been investigated as a transparent component for flexible devices to replace glass (Patent Document 1). However, polyimide-based films are generally colored yellowish-brown to dark brown, making them insufficient for optical applications such as displays (Patent Documents 2 and 3). In contrast, transparent polyimides have light absorption properties controlled by the introduction of an aliphatic backbone or halogen atoms, resulting in colorless, transparent films (Patent Document 4). While these molecular designs can improve transparency, they also impair the inherent mechanical properties of polyimides, resulting in poor folding resistance. Furthermore, polyimide films produced by the method of Patent Document 4 suffer from the drawback of being difficult to peel from the support substrate, resulting in poor productivity.

[0003] In recent years, the use of polyesters and other resins other than polyimides has been proposed (Patent Document 5). However, the pencil hardness of polyester films is insufficient, and even when hard-coated, it is difficult to impart scratch resistance sufficient for practical use. Therefore, there is a demand for resin materials with even higher pencil hardness. As described above, a resin film that satisfies the requirements for transparency, heat resistance, flex resistance, and pencil hardness has yet to be realized. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-163309 [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-56825 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-322441 [Patent Document 4] Japanese Patent Application Laid-Open No. 2012-40836 [Patent Document 5] Japanese Patent Application Publication No. 2018-72663 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a film made of polycarbonate resin that is excellent in transparency, heat resistance, flex resistance and pencil hardness, and a cover window for a flexible display device using the same. [Means for solving the problem]

[0006] As a result of extensive research, the present inventors have discovered that a film made of a polycarbonate resin containing a specific repeating unit has excellent transparency, heat resistance, flex resistance, and pencil hardness, and have thus completed the present invention. That is, according to the present invention, the above object is achieved by the following items 1 to 9.

[0007] 1. A film made of a polycarbonate resin whose main repeating units comprise a repeating unit (A) represented by the following formula (1) and a repeating unit (B) represented by the following formula (2), wherein the content of repeating unit (A) is 40 to 100 mol % and the content of repeating unit (B) is 0 to 60 mol %, and the film has a pencil hardness of F or higher measured in accordance with JIS K5600, wherein the polycarbonate resin is a homopolycarbonate resin, a polycarbonate copolymer, or a polycarbonate blend, and the relationship between the viscosity average molecular weight (V) of the polycarbonate resin component constituting the polycarbonate copolymer or polycarbonate blend and the content (W mol %) of repeating unit (A) satisfies the following formula (4): V≧80W+20,000 (4)

[0008] [ka]

[0009] (In formula (1), R 1 and R 2 each independently represents a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an aralkyloxy group having 7 to 20 carbon atoms; R 3 and R 4 each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an aralkyloxy group having 7 to 20 carbon atoms; and X represents a single bond, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkylidene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, a substituted or unsubstituted cyclic alkylene group having 3 to 8 carbon atoms, a sulfur atom, or an oxygen atom.

[0010] [ka]

[0011] (wherein Y is a single bond or at least one group selected from the group consisting of the following formula (3):)

[0012] [ka]

[0013] (In the formula, R11 ,R 12 ,R 13 ,R 14 ,R 15 ,R 16 ,R 17 and R 18 each independently represents at least one group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms; R 19 and R 20 each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms, a nitro group, an aldehyde group, a cyano group, and a carboxyl group; when there are a plurality of groups, they may be the same or different, g is an integer from 1 to 10, and h is an integer from 4 to 7.

[0014] 2. The film according to item 1 above, wherein the polycarbonate resin has a glass transition temperature of 100 to 200°C. 3. The film according to item 1 or 2 above, wherein the repeating unit represented by formula (1) is a repeating unit derived from 2,2-bis(4-hydroxy-3-methylphenyl)propane. 4. The film according to any one of items 1 to 3 above, wherein the repeating unit represented by formula (2) is a repeating unit derived from 2,2-bis(4-hydroxyphenyl)propane. 5. The film according to any one of items 1 to 4 above, wherein the viscosity average molecular weight (V) of the polycarbonate resin is in the range of 22,000 to 65,000. 6. The film according to any one of items 1 to 5 above, wherein the polycarbonate resin has a molecular weight distribution (Mw / Mn), which is the ratio of weight average molecular weight (Mw) to number average molecular weight (Mn), measured by GPC, in the range of 1.3 to 4.0. 7. The film according to any one of the above items 1 to 6, which has a thickness of 10 to 100 μm. 8. The film according to any one of the above items 1 to 7, which can be bent 200,000 times or more. 9. A cover window for a flexible display device using the film according to any one of items 1 to 8 above. [Effects of the Invention]

[0015] The film made of the polycarbonate resin of the present invention is excellent in transparency, heat resistance, flex resistance and pencil hardness, and is useful as a cover window for a flexible display. DETAILED DESCRIPTION OF THE INVENTION

[0016] <Polycarbonate resin> The polycarbonate resin of the present invention is a polycarbonate resin containing a repeating unit (A) represented by the following formula (1).

[0017] [ka]

[0018] (In formula (1), R 1 and R 2 each independently represents a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an aralkyloxy group having 7 to 20 carbon atoms; R 3 and R 4each independently represents a hydrogen atom, a halogen atom, an alkyl group having 1 to 10 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an aryl group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, or an aralkyloxy group having 7 to 20 carbon atoms; and X represents a single bond, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkylidene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, a substituted or unsubstituted cyclic alkylene group having 3 to 8 carbon atoms, a sulfur atom, or an oxygen atom.

[0019] In the repeating unit (A) represented by the formula (1), R 1 and R 2 R preferably each independently represents an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, or an aryl group having 6 to 10 carbon atoms. 3 and R 4 preferably each independently represent a hydrogen atom, an alkyl group having 1 to 6 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, or an aryl group having 6 to 10 carbon atoms. X preferably represents a single bond, a substituted or unsubstituted alkylene group having 1 to 10 carbon atoms, a substituted or unsubstituted alkylidene group having 1 to 10 carbon atoms, an arylene group having 6 to 10 carbon atoms, or a substituted or unsubstituted cyclic alkylene group having 3 to 8 carbon atoms.

[0020] Examples of dihydric phenols that can be used to derive the repeating unit (A) represented by formula (1) include 2,2-bis(4-hydroxy-3-methylphenyl)propane (hereinafter referred to as BPC), 2,2-bis(4-hydroxy-3-isopropylphenyl)propane, 2,2-bis(3-t-butyl-4-hydroxyphenyl)propane, 2,2-bis(3-phenyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-dimethyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-diisopropyl-4-hydroxyphenyl)propane, and 2,2-bis(3,5-diisopropyl-4-hydroxyphenyl)propane. Bis(3,5-di-t-butyl-4-hydroxyphenyl)propane, 2,2-bis(3,5-diphenyl-4-hydroxyphenyl)propane, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, 1,1-bis(4-hydroxy-3-isopropylphenyl)cyclohexane, 1,1-bis(3-t-butyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3-phenyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3 ,5-diisopropyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-di-t-butyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(3,5-diphenyl-4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxy-2,3,5,6-tetramethylphenyl)cyclohexane, 1,1-bis(4-hydroxy-3-methylphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxy-3-isopropylphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis bis(3-t-butyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3-phenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3,5-dimethyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3,5-diisopropyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3,5-di-t-butyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(3,5-diphenyl-4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxy-2,3,5,6-tetramethylphenyl)-3,3,5-trimethylcyclohexane, 4,4'-dihydroxy-3,3'-dimethyl-1,1-biphenyl, 4,4'-dihydroxy-3,3'-dioctyl-1,1-biphenyl, 1,3-bis(2-(4-hydroxy-3-methylphenyl)-2-propyl)benzene, 1,4-bis(2-(4-hydroxy-3-methylphenyl)-2-propyl)benzene Bis(4-hydroxyphenyl)benzene, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 4,4'-dihydroxy-3,3'-dimethyldiphenyl ether, 3,3'-dimethyl-4,4'-dihydroxydiphenyl sulfide, bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane, 2,2-bis(4-hydroxy-3-ethylphenyl)propane, 1,1-bis(3-methyl-4-hydroxyphenyl)decane, and 1,1-bis(2,3-dimethyl-4-hydroxyphenyl)decane are examples of such bis(4-hydroxy-2,6-dimethyl-3-methoxyphenyl)methane.

[0021] Among the above dihydric phenols, BPC, 9,9-bis(4-hydroxy-3-methylphenyl)fluorene, 1,1-bis(4-hydroxy-3-methylphenyl)cyclohexane, and 1,1-bis(4-hydroxy-3-methylphenyl)-3,3,5-trimethylcyclohexane are preferred. The most preferred dihydric phenol from which the repeating unit (A) is derived is BPC.

[0022] The molar fraction of the repeating unit represented by the above formula (1) in the polycarbonate resin of the present invention is 40 mol % or more, preferably 50 mol % or more. If it is less than the lower limit, the pencil hardness will be undesirably low.

[0023] Such a ratio of repeating units (A) may be achieved by using a homopolycarbonate resin or a polycarbonate copolymer, or by mixing polycarbonate resins with different composition ratios (polycarbonate blend).

[0024] The polycarbonate resin of the present invention is a polycarbonate resin containing a repeating unit (B) represented by the following formula (2).

[0025] [ka]

[0026] (wherein Y is a single bond or at least one group selected from the group consisting of the following formula (3):)

[0027] [ka]

[0028] (In the formula, R 11 ,R 12 ,R 13 ,R 14 ,R 15 ,R 16 ,R 17 and R 18 each independently represents at least one group selected from the group consisting of a hydrogen atom, an alkyl group having 1 to 18 carbon atoms, an aryl group having 6 to 14 carbon atoms, and an aralkyl group having 7 to 20 carbon atoms; R 19 and R 20 each independently represents at least one group selected from the group consisting of a hydrogen atom, a halogen atom, an alkyl group having 1 to 18 carbon atoms, an alkoxy group having 1 to 10 carbon atoms, a cycloalkyl group having 6 to 20 carbon atoms, a cycloalkoxy group having 6 to 20 carbon atoms, an alkenyl group having 2 to 10 carbon atoms, an aryl group having 6 to 14 carbon atoms, an aryloxy group having 6 to 10 carbon atoms, an aralkyl group having 7 to 20 carbon atoms, an aralkyloxy group having 7 to 20 carbon atoms, a nitro group, an aldehyde group, a cyano group, and a carboxyl group; when there are a plurality of groups, they may be the same or different, g is an integer from 1 to 10, and h is an integer from 4 to 7.

[0029] Examples of dihydric phenols from which the repeating unit (B) represented by the formula (2) is derived include 2,2-bis(4-hydroxyphenyl)propane (hereinafter referred to as BPA), 1,1-bis(4-hydroxyphenyl)cyclohexane, 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane, 1,1-bis(4-hydroxyphenyl)-4-isopropylcyclohexane, 4,4'-dihydroxy-1,1-biphenyl, 4,4'-dihydroxydiphenyl ether, 4,4'-dihydroxydiphenyl thioether, 1,3-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, 1,4-bis(2-(4-hydroxyphenyl)-2-propyl)benzene, α,α'-bis(4-hydroxyphenyl)-o-diisopropylbenzene, α,α'-bis(4-hydroxyphenyl)-m-diisopropylbenzene, and α,α'-bis(4-hydroxyphenyl)-p -diisopropylbenzene, 9,9-bis(4-hydroxyphenyl)fluorene, 4,4'-dihydroxydiphenyl sulfone, 2,4'-dihydroxydiphenyl sulfone, 4,4'-dihydroxydiphenyl sulfoxide, 4,4'-dihydroxydiphenyl sulfide, 1,1-bis(4-hydroxyphenyl)methane, 2,4'-dihydroxydiphenylmethane, bis(2-hydroxyphenyl)methane, bis(4-hydroxyphenyl)methane, bis(4-hydroxyphenyl)cyclohexylmethane, bis(4-hydroxyphenyl)diphenylmethane, 1,1-bis(4-hydroxyphenyl)ethane, 2,2-bis(4-hydroxyphenyl)butane, 2,2-bis(4-hydroxyphenyl)pentane, 4,4-bis(4-hydroxyphenyl)heptane, 2,2-bis(4-hydroxyphenyl)octane, 1,1-bis(4-hydroxyphenyl)decane.

[0030] Among the above dihydric phenols, BPA, 1,1-bis(4-hydroxyphenyl)cyclohexane, and 1,1-bis(4-hydroxyphenyl)-3,3,5-trimethylcyclohexane are preferred. The most preferred dihydric phenol from which the repeating unit (A) is derived is BPA.

[0031] The molar fraction of the repeating unit represented by the above formula (2) in the polycarbonate resin of the present invention is 60 mol % or less, preferably 50 mol % or less, more preferably 40 mol % or less, and even more preferably 30 mol % or less. Within this range, the polycarbonate resin has excellent pencil hardness and heat resistance.

[0032] Such a ratio of repeating units (B) may be achieved by a polycarbonate copolymer or by mixing polycarbonate resins with different composition ratios (polycarbonate blend).

[0033] Furthermore, other dihydroxy compounds and diol compounds can be used as compounds from which the repeating unit (C) can be derived, other than the repeating units (A) and (B).

[0034] Suitable examples of other dihydroxy compounds include 2,6-dihydroxynaphthalene, hydroquinone, resorcinol, resorcinol substituted with an alkyl group having 1 to 3 carbon atoms, 3-(4-hydroxyphenyl)-1,1,3-trimethylindan-5-ol, 1-(4-hydroxyphenyl)-1,3,3-trimethylindan-5-ol, 6,6'-dihydroxy-3,3,3',3'-tetramethylspiroindane, 1-methyl-1,3-bis(4-hydroxyphenyl)-3-isopropylcyclohexane, 1-methyl-2-(4-hydroxyphenyl)-3-[1-(4-hydroxyphenyl)isopropyl]cyclohexane, and 1,6-bis(4-hydroxyphenyl)-1,6-hexanedione. Further details of such dihydric phenols are described in, for example, WO03 / 080728, JP-A-6-172508, JP-A-8-27370, JP-A-2001-55435, and JP-A-2002-117580.

[0035] In addition, examples of diol compounds include isosorbide:1,4:3,6-dianhydro-D-sorbitol, tricyclodecane dimethanol (TCDDM), 4,8-bis(hydroxymethyl)tricyclodecane, tetramethylcyclobutanediol (TMCBD), 2,2,4,4-tetramethylcyclobutane-1,3-diol, mixed isomers, cis / trans-1,4-cyclohexanedimethanol (CHDM), cis / trans-1,4-bis(hydroxymethyl)cyclohexane, cyclohex-1,4-ylenedimethanol, and the like. Examples of suitable cyclohexanedimethanol include ethanol, trans-1,4-cyclohexanedimethanol (tCHDM), trans-1,4-bis(hydroxymethyl)cyclohexane, cis-1,4-cyclohexanedimethanol (cCHDM), cis-1,4-bis(hydroxymethyl)cyclohexane, cis-1,2-cyclohexanedimethanol, 1,1'-bi(cyclohexyl)-4,4'-diol, spiroglycol, dicyclohexyl-4,4'-diol, 4,4'-dihydroxybicyclohexyl, and poly(ethylene glycol).

[0036] The molar fraction of the repeating unit (C) is preferably 20 mol % or less, more preferably 10 mol % or less.

[0037] (Manufacturing method) The polycarbonate resin used in the present invention is obtained by reacting the dihydric phenol compound with a carbonate precursor. Reaction methods include interfacial polycondensation, melt transesterification, solid-phase transesterification of carbonate prepolymers, and ring-opening polymerization of cyclic carbonate compounds. In the case of interfacial polycondensation, a monohydric phenol-based end-stopper is usually used.

[0038] The polycarbonate resin used in the present invention can be copolymerized with a fatty acid, if necessary, such as 1,10-dodecanedioic acid (DDDA), adipic acid, hexanedioic acid, isophthalic acid, 1,3-benzenedicarboxylic acid, terephthalic acid, 1,4-benzenedicarboxylic acid, 2,6-naphthalenedicarboxylic acid, 3-hydroxybenzoic acid (mHBA), and 4-hydroxybenzoic acid (pHBA).

[0039] The polycarbonate resin used in the present invention includes polyester carbonate copolymerized with an aromatic or aliphatic (including alicyclic) bifunctional carboxylic acid. The aliphatic bifunctional carboxylic acid is preferably an α,ω-dicarboxylic acid. Preferred examples of the aliphatic bifunctional carboxylic acid include linear saturated aliphatic dicarboxylic acids such as sebacic acid (decanedioic acid), dodecanedioic acid, tetradecanedioic acid, octadecanedioic acid, and icosane dicarboxylic acid, as well as alicyclic dicarboxylic acids such as cyclohexanedicarboxylic acid. These carboxylic acids may be copolymerized to the extent that the objective is not impaired. The polycarbonate resin used in the present invention may also be copolymerized with a repeating unit containing a polyorganosiloxane unit, if necessary.

[0040] The polycarbonate resin used in the present invention may be copolymerized with a repeating unit containing a trifunctional or higher polyfunctional aromatic compound, if necessary, to form a branched polycarbonate.

[0041] Suitable examples of trifunctional or higher polyfunctional aromatic compounds used in branched polycarbonates include 4,6-dimethyl-2,4,6-tris(4-hydroxyphenyl)heptene-2, 2,4,6-trimethyl-2,4,6-tris(4-hydroxyphenyl)heptane, 1,3,5-tris(4-hydroxyphenyl)benzene, 1,1,1-tris(4-hydroxyphenyl)ethane, 1,1,1-tris(3,5-dimethyl-4-hydroxyphenyl)ethane, 2,6-bis(2-hydroxy-5-methylbenzyl)-4-methylphenol, and trisphenols such as 4-{4-[1,1-bis(4-hydroxyphenyl)ethyl]benzene}-α,α-dimethylbenzylphenol. Of these, 1,1,1-tris(4-hydroxyphenyl)ethane is preferred. The repeating units derived from such polyfunctional aromatic compounds preferably account for 0.03 to 1.5 mol %, more preferably 0.1 to 1.2 mol %, and particularly preferably 0.2 to 1.0 mol %, of a total of 100 mol % including repeating units derived from other dihydric phenol components.

[0042] The branched structural units may be derived not only from polyfunctional aromatic compounds but also from side reactions occurring during polymerization by melt transesterification without using polyfunctional aromatic compounds. 1 It can be calculated by H-NMR measurement.

[0043] In reactions using, for example, phosgene as a carbonate precursor, the reaction is usually carried out in the presence of an acid binder and a solvent. Examples of acid binders include alkali metal hydroxides such as sodium hydroxide and potassium hydroxide, and amine compounds such as pyridine. Examples of solvents include halogenated hydrocarbons such as methylene chloride and chlorobenzene. To promote the reaction, a catalyst such as a tertiary amine or a quaternary ammonium salt can also be used. The reaction temperature is usually 0 to 40°C, and the reaction time is several minutes to 5 hours.

[0044] Transesterification using, for example, a carbonate diester as a carbonate precursor is carried out by stirring a predetermined proportion of aromatic dihydroxy component with the carbonate diester under heating in an inert gas atmosphere, and distilling off the resulting alcohol or phenol. The reaction temperature varies depending on the boiling point of the resulting alcohol or phenol, but is typically in the range of 120 to 300°C. The reaction is completed by reducing the pressure from the beginning of the reaction to distill off the resulting alcohol or phenol. A catalyst typically used in transesterification can also be used to promote the reaction. Examples of carbonate diesters used in the transesterification reaction include diphenyl carbonate, dinaphthyl carbonate, bis(diphenyl)carbonate, dimethyl carbonate, diethyl carbonate, and dibutyl carbonate. Of these, diphenyl carbonate is particularly preferred.

[0045] Commonly used monofunctional phenols can be used as end terminators. In particular, in the case of reactions using phosgene as a carbonate precursor, monofunctional phenols are commonly used as end terminators to control molecular weight. Furthermore, the resulting polycarbonate resins have excellent thermal stability compared to those without end terminators, since their terminals are blocked with groups based on monofunctional phenols. Specific examples of the monofunctional phenols include phenol, m-methylphenol, p-methylphenol, m-propylphenol, p-propylphenol, 1-phenylphenol, 2-phenylphenol, p-tert-butylphenol, p-cumylphenol, isooctylphenol, and p-long-chain alkylphenols.

[0046] (Viscosity average molecular weight (V)) The viscosity average molecular weight (V) of the polycarbonate resin of the present invention is preferably 22,000 to 65,000, more preferably 23,000 to 60,000, and even more preferably 24,000 to 50,000. A viscosity average molecular weight within the above range is preferred because of excellent flex resistance, productivity, and processability.

[0047] The viscosity average molecular weight (V) of the polycarbonate resin in the present invention is determined by first calculating the specific viscosity (η SP ) was determined using an Ostwald viscometer from a solution of 0.7 g of resin dissolved in 100 ml of methylene chloride at 20°C. Specific viscosity (η SP )=(t-t0) / t0 [t0 is the number of seconds that methylene chloride falls, and t is the number of seconds that the sample solution falls] The calculated specific viscosity (η SP ) and the viscosity average molecular weight Mv was calculated using the following formula: η SP / c=[η]+0.45×[η] 2 c (where [η] is the intrinsic viscosity) [η]=1.23×10 -4 Mv 0.83 c=0.7

[0048] (Weight average molecular weight: Mw / Number average molecular weight: Mn) In addition to the viscosity-average molecular weight described above, the molecular weight of a polycarbonate resin can also be evaluated by weight-average molecular weight and number-average molecular weight measured by GPC. The ratio of weight-average molecular weight to number-average molecular weight (Mw / Mn), which indicates the molecular weight distribution, is preferably 1.3 to 4.0, more preferably 1.4 to 3.5, even more preferably 1.5 to 3.0, and most preferably 1.6 to 2.8. A ratio within this range is preferred because it provides excellent flex resistance.

[0049] The weight average molecular weight and number average molecular weight can be measured by dissolving 10 mg of polycarbonate resin in 5 ml of chloroform and using a GPC (gel permeation chromatography) apparatus under the following conditions. Apparatus: Tosoh Corporation GPC system (HLC8220) Detector: CH-2 (UV wavelength 254 nm) Column: Tsk-gel Super HZ4000+3000+2000 Standard material: Tosoh standard polystyrene Eluent: chloroform, 0.35 ml / min

[0050] (glass transition temperature: Tg) The glass transition temperature (Tg) of the polycarbonate resin is preferably in the range of 100 to 200°C, more preferably 110 to 180°C, and even more preferably 120 to 150°C. A Tg within the above range is preferred because it provides good heat resistance stability and moldability. The glass transition temperature (Tg) is measured using a 2910 DSC manufactured by TA Instruments Japan Co., Ltd. at a heating rate of 20°C / min.

[0051] (Pencil hardness) The pencil hardness of the polycarbonate resin of the present invention is preferably F or higher, preferably H or higher, and more preferably 2H or higher. When used as a cover window for a flexible display or the like, the resin film is used as a laminate with a hard coat applied. In this case, the higher the pencil hardness of the base resin film, the higher the pencil hardness of the laminate, which is preferable. Higher pencil hardness of the resin film allows for a wider selection of hard coat types, which is preferable because it allows for a balance between flex resistance and other physical properties. In the present invention, pencil hardness refers to the hardness at which no scratch marks remain when the resin of the present invention is rubbed with a pencil of a specific pencil hardness. It is preferable to use the pencil hardness used in the surface hardness test for coating films, which can be measured according to JIS K-5600, as an index. Pencil hardness increases in the following order: 9H, 8H, 7H, 6H, 5H, 4H, 3H, 2H, H, F, HB, B, 2B, 3B, 4B, 5B, and 6B, with the hardest being 9H and the softest being 6B.

[0052] (Relationship between the content (W) of repeating units (A) and viscosity average molecular weight (V)) The polycarbonate resin of the present invention includes either a polycarbonate copolymer or a polycarbonate blend, and is characterized in that the relationship between the viscosity average molecular weight (V) of the polycarbonate resin component constituting the polycarbonate copolymer or polycarbonate blend and the content (W mol %) of the repeating unit (A) satisfies the following formula (4): When this formula is satisfied, the balance of heat resistance, flex resistance, and pencil hardness is excellent, which is preferable. In the case of a polycarbonate blend, each of the blended polycarbonate resin components must satisfy the following formula (4). V≧80W+20,000 (4)

[0053] (Other ingredients) The polycarbonate resin of the present invention may contain various additives to impart various properties to the resin composition, provided that the object of the present invention is not impaired. Additives that can be used include mold release agents, heat stabilizers, ultraviolet absorbers, bluing agents, antistatic agents, flame retardants, heat-shielding agents, fluorescent dyes (including fluorescent brighteners), pigments, light diffusing agents, reinforcing fillers, other resins, elastomers, etc.

[0054] Preferably, the release agent is one that is composed of 90% by weight or more of an ester of alcohol and fatty acid. Specific examples of the ester of alcohol and fatty acid include ester of monohydric alcohol and fatty acid, and partial or complete ester of polyhydric alcohol and fatty acid. Specific examples of the ester of monohydric alcohol and saturated fatty acid include stearyl stearate, palmityl palmitate, butyl stearate, methyl laurate, and isopropyl palmitate. Stearyl stearate is preferred. Examples of partial or full esters of polyhydric alcohols and saturated fatty acids include stearic acid monoglyceride, stearic acid diglyceride, stearic acid triglyceride, stearic acid monosorbitate, behenic acid monoglyceride, pentaerythritol monostearate, pentaerythritol tetrastearate, pentaerythritol tetrapelargonate, propylene glycol monostearate, biphenyl biphenate, sorbitan monostearate, 2-ethylhexyl stearate, and full or partial esters of dipentaerythritol such as dipentaerythritol hexastearate. Among these esters, stearic acid monoglyceride, stearic acid triglyceride, pentaerythritol tetrastearate, and mixtures of stearic acid triglyceride and stearyl stearate are preferred, with stearic acid monoglyceride and pentaerythritol tetrastearate being more preferred.

[0055] The amount of the release agent to be added is preferably in the range of 0.05 to 0.5 parts by weight, more preferably 0.1 to 0.4 parts by weight, and even more preferably 0.12 to 0.3 parts by weight, relative to 100 parts by weight of the polycarbonate resin.

[0056] Examples of heat stabilizers include phosphorus-based heat stabilizers, sulfur-based heat stabilizers, and hindered phenol-based heat stabilizers. Examples of phosphorus-based heat stabilizers include phosphorous acid, phosphoric acid, phosphonous acid, phosphonic acid, and esters thereof. Specific examples include bis(2,4-dicumylphenyl)pentaerythritol diphosphite, tris(2,4-di-tert-butylphenyl)phosphite, tris(2,6-di-tert-butylphenyl)phosphite, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, [1,1-biphenyl]-4,4-diylbis[bis(2,4-di-tert-butylphenoxy)phosphine], 3,9-bis(2,6-di-tert-butylphenyl)propionate ... butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane is preferred, and tris(2,4-di-tert-butylphenyl)phosphite, 3-(3,5-di-tert-butyl-4-hydroxyphenyl)stearyl propionate, and 3,9-bis(2,6-di-tert-butyl-4-methylphenoxy)-2,4,8,10-tetraoxa-3,9-diphosphaspiro[5.5]undecane are more preferred.

[0057] The amount of the heat stabilizer to be added is preferably in the range of 0.001 to 0.5 parts by weight, more preferably 0.005 to 0.4 parts by weight, and even more preferably 0.01 to 0.3 parts by weight, relative to 100 parts by weight of the polycarbonate resin.

[0058] <Film> The method for producing a film made of the polycarbonate resin of the present invention is not particularly limited, and examples thereof include melt extrusion and solution casting (flow casting). A specific method for melt extrusion involves, for example, feeding a fixed amount of polycarbonate resin into an extruder, heating and melting it, extruding the molten resin into a sheet shape from the tip of a T-die into a mirror-finished roll, taking it up while cooling it with multiple rolls, and cutting it to an appropriate size or winding it up when it solidifies. A specific method for solution casting involves, for example, casting a solution (concentration 5 to 40% by mass) of polycarbonate resin dissolved in methylene chloride from a T-die onto a mirror-polished stainless steel plate, passing it through a temperature-controlled oven in stages to peel the film, further peeling it to remove the solvent, cooling it, and winding it up.

[0059] (Thickness) The thickness of the film is preferably in the range of 10 to 100 μm, more preferably in the range of 30 to 75 μm, and even more preferably in the range of 40 to 60 μm. The thickness in the above range is preferable because it provides excellent flex resistance and pencil hardness.

[0060] (Total light transmittance / haze) The polycarbonate resin film of the present invention preferably has high transparency. The total light transmittance is preferably 70% or more, more preferably 80% or more, even more preferably 85% or more, and particularly preferably 88% or more. The haze is preferably 2.0% or less, more preferably 1.5% or less, and even more preferably 1.0% or less. Within the above ranges, the film is preferred for its high transparency and excellent visibility when used as a cover window film for flexible displays, etc. Total light transmittance (%) and haze (%) are measured using a polycarbonate resin film with a Haze Meter NDH 2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with ASTM D1003.

[0061] (Bending resistance) The polycarbonate resin film of the present invention preferably has high flex resistance. Flex resistance can be evaluated by conducting a flex resistance test using a rotational oscillation durability tester (TCDM111LH) manufactured by Yuasa System Co., Ltd., with a curvature radius R of 2.0 mm, a flex angle of ±135°, a flex speed of 100 rpm, and a load of 50 gf. In the flex resistance test, the film is repeatedly flexed until it breaks, and the more flexes it has at the time of breakage, the higher its flex resistance. The number of flexes is preferably 200,000 or more, and more preferably 250,000 or more. A flex resistance in the above range is preferred because it provides high flex resistance when used as a cover window film for flexible displays, etc. [Example]

[0062] The present invention will be described in more detail below with reference to examples, but these examples are not intended to limit the scope of the present invention. Unless otherwise specified, parts in the examples are parts by mass. Evaluations were made according to the following methods.

[0063] (1) Polymer composition ratio Each repeating unit was measured by proton NMR using JNM-AL400 manufactured by JEOL Ltd., and the polymer composition ratio (mol %) was calculated.

[0064] (2) Viscosity average molecular weight (Mv) The specific viscosity (η SP ) was measured using an Ostwald viscometer from a solution of 0.7 g of sample dissolved in 100 ml of methylene chloride at 20°C. Specific viscosity (η SP )=(t-t0) / t0 [t0 is the number of seconds that methylene chloride falls, and t is the number of seconds that the sample solution falls] The calculated specific viscosity (η SP ) and the viscosity average molecular weight Mv was calculated using the following formula: η SP / c=[η]+0.45×[η] 2 c (where [η] is the intrinsic viscosity) [η]=1.23×10 -4 Mv 0.83 c=0.7

[0065] (3) Relationship between the content of repeating units (A) (W mol%) and viscosity average molecular weight (V) When the relationship between the content (W mol %) of the repeating unit (A) and the viscosity average molecular weight (V) satisfied the following formula (4), it was evaluated as "Good"; when it did not, it was evaluated as "Poor." V≧80W+20,000 (4)

[0066] (4) Weight average molecular weight (Mw) / number average molecular weight (Mn) 10 mg of the obtained polycarbonate resin was dissolved in 5 ml of chloroform, and the weight average molecular weight Mw and number average molecular weight Mn were measured using a GPC (gel permeation chromatography) apparatus under the following conditions. Apparatus: Tosoh Corporation GPC system (HLC8220) Detector: CH-2 (UV wavelength 254 nm) Column: Tsk-gel SuperHZ4000+3000+2000 Standard material: Tosoh standard polystyrene Eluent: chloroform, 0.35 ml / min

[0067] (5) Glass transition temperature (Tg) The polycarbonate resin obtained was measured using a 2910 Model DSC manufactured by TA Instruments Japan Co., Ltd. at a heating rate of 20°C / min.

[0068] (6) Pencil hardness The obtained polycarbonate resin was press-molded using a heat press molding machine (Shinto Metal Industries Co., Ltd., compression molding machine: SFV-10, vacuum pump unit: GXD-360) to obtain a disk-shaped resin plate approximately 3 mm thick. The press molding conditions were a mold temperature of 150 to 300°C, a primary pressure of 1 MPa (30 seconds), and a secondary pressure of 1.5 MPa (5 minutes). Using this resin plate, a line was drawn on the surface of the resin plate in accordance with JIS K5600 in a thermostatic chamber at an ambient temperature of 23°C, with a pencil held at a 45° angle and a load of 750 g applied, and the surface condition was evaluated visually. Load: 750g Measurement speed: 50mm / min Measurement distance: 7mm Pencil: Mitsubishi Pencil Hi-uni

[0069] (7) Flexibility The obtained film was cut into a size of 10 × 150 mm and subjected to a bending resistance test using a rotational oscillation type durability tester (TCDM111LH) manufactured by Yuasa System Co., Ltd. The test was conducted with a radius of curvature R of 2.0 mm, a bending angle of ±135°, a bending speed of 100 rpm, and a load of 50 gf. The film was repeatedly bent until it broke, and the number of bending cycles at which it broke was recorded.

[0070] (8) Total light transmittance / haze The total light transmittance (%) and haze (%) of the obtained film were measured using a Haze Meter NDH 2000 manufactured by Nippon Denshoku Kogyo Co., Ltd. in accordance with ASTM D1003.

[0071] (9) Overall rating The overall evaluation was given as "Good" if all of the following (i) to (iv) were satisfied, and as "Poor" if none were satisfied: transparency, heat resistance, flex resistance, pencil hardness (i) Glass transition temperature of 100°C or higher (ii) Pencil hardness F or higher (iii) Total light transmittance of 70% or more and haze of 2.0% or less (iv) Number of bending cycles: 200,000 or more

[0072] [Example 1] A reactor equipped with a thermometer, stirrer, and reflux condenser was charged with 10,663 parts of ion-exchanged water and 6,015 parts of 25% aqueous sodium hydroxide. 2,921 parts of BPC (dihydric phenol) and 5.84 parts of hydrosulfite were dissolved in the solution. 12,588 parts of methylene chloride was then added, and 1,500 parts of phosgene was bubbled in over 70 minutes at 16 to 24°C with stirring. 911 parts of 25% aqueous sodium hydroxide and 0.58 parts of triethylamine were then added, followed by a solution of 30.76 parts of p-tert-butylphenol in 277 parts of methylene chloride. The mixture was then emulsified with stirring. While stirring, 2.30 parts of triethylamine were added at a temperature of 28°C, and the mixture was stirred for 1 hour at 26 to 31°C, at which point the reaction was terminated. After the reaction was completed, the organic phase was separated, diluted with methylene chloride, and repeatedly washed with ion-exchanged water. When the washings became neutral, the mixture was washed with acidic hydrochloric acid water. The resin was then washed repeatedly with ion-exchanged water until the conductivity of the aqueous phase was nearly equal to that of the ion-exchanged water. The mixture was then placed in a kneader filled with warm water and stirred to evaporate the solvent, yielding a resin powder. After dehydration, the mixture was dried at 100°C for 12 hours in a hot air circulating dryer. The resulting powder was subjected to various evaluations using the methods described above, and the results are shown in Table 1.

[0073] The resulting polycarbonate resin was then formed into a film by solution casting. Methylene chloride was used as the solvent, and the amount of resin was adjusted to a concentration range of 5 to 40% by mass depending on the viscosity of the resin solution. The resulting solution was dried by gradually increasing the temperature from a T-die in the range of 25°C to 130°C, yielding a film with a thickness of 51 μm. This film was subjected to various evaluations using the methods described above, and the results are shown in Table 2.

[0074] [Example 2] A polycarbonate resin powder was produced in the same manner as in Example 1, except that p-tert-butylphenol was changed to 41.35 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0075] [Example 3] A polycarbonate resin powder was produced in the same manner as in Example 1, except that the dihydric phenol was changed to 2337 parts of BPC, 519 parts of BPA, and 37.59 parts of p-tert-butylphenol. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0076] [Example 4] A reactor equipped with a thermometer, stirrer, and reflux condenser was charged with 12,784 parts of ion-exchanged water and 5,682 parts of 25% aqueous sodium hydroxide. 1,517 parts of BPC and 1,349 parts of BPA (dihydric phenols), and 5.73 parts of hydrosulfite were dissolved in the reaction mixture. 12,074 parts of methylene chloride was added, and 1,500 parts of phosgene was blown in over 70 minutes at 16 to 24°C with stirring. 947 parts of 25% aqueous sodium hydroxide was then added, followed by a solution of 24.86 parts of p-tert-butylphenol in 224 parts of methylene chloride. 0.60 parts of triethylamine was then added and the mixture was stirred to form an emulsion. With stirring, 2.39 parts of triethylamine was added at a temperature of 28°C, and the mixture was stirred for 1 hour at a temperature of 26 to 31°C, at which point the reaction was terminated. After the reaction was completed, the organic phase was separated, diluted with methylene chloride, and repeatedly washed with ion-exchanged water. When the washings became neutral, the solution was washed with hydrochloric acid-acidic water. After repeated washing with ion-exchanged water, the aqueous phase reached a conductivity almost identical to that of the ion-exchanged water. The solution was then placed in a kneader filled with warm water, and the solvent was evaporated while stirring to obtain a resin powder. After dehydration, the solution was dried at 100°C for 12 hours in a hot air circulating dryer. The obtained powder was subjected to various evaluations using the methods described above, and the results are shown in Table 1. A film was also produced using the same method as in Example 1. The evaluation results of the film are shown in Table 2.

[0077] [Example 5] A polycarbonate resin powder was produced in the same manner as in Example 4, except that p-tert-butylphenol was changed to 35.51 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0078] [Example 6] A polycarbonate resin powder was produced in the same manner as in Example 4, except that p-tert-butylphenol was changed to 40.84 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0079] [Example 7] A polycarbonate resin powder was produced in the same manner as in Example 4, except that p-tert-butylphenol was changed to 53.27 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0080] [Example 8] A polycarbonate resin powder was produced in the same manner as in Example 4, except that the dihydric phenol was changed to 1214 parts of BPC, 1619 parts of BPA, and 53.27 parts of p-tert-butylphenol. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0081] [Example 9] A reactor equipped with a thermometer, stirrer, and reflux condenser was charged with 14,876 parts of ion-exchanged water and 6,612 parts of 25% aqueous sodium hydroxide solution. 3,140 parts of BPA (dihydric phenol) and 6.28 parts of hydrosulfite were dissolved in the solution. 14,050 parts of methylene chloride was added, and 1,500 parts of phosgene was blown in over 70 minutes at 16 to 24 °C with stirring. Then, 1,102 parts of 25% aqueous sodium hydroxide solution was added, followed by a solution of 59.92 parts of p-tert-butylphenol in 251 parts of methylene chloride. The mixture was stirred to form an emulsion. With stirring, 2.78 parts of triethylamine was added at 28 °C, and the mixture was stirred for 1 hour at 26 to 31 °C, at which point the reaction was terminated. After the reaction was completed, the organic phase was separated, diluted with methylene chloride, and repeatedly washed with ion-exchanged water. When the washings became neutral, the mixture was washed with hydrochloric acid-acidic water. After that, it was repeatedly washed with ion-exchanged water until the conductivity of the aqueous phase was almost the same as that of the ion-exchanged water. Then, it was put into a kneader filled with warm water and stirred to evaporate the solvent, yielding a polycarbonate resin powder. After dehydration, it was dried in a hot air circulating dryer at 100°C for 12 hours to obtain a BPA homopolycarbonate resin powder (9-I).

[0082] 500 parts of the BPA homopolycarbonate resin powder (9-I) and 500 parts of the BPC homopolycarbonate produced in Example 2 were dissolved in methylene chloride, and the resulting solution was placed in a kneader filled with warm water. The solvent was evaporated with stirring to obtain a polycarbonate blend powder. After dehydration, the mixture was dried at 100°C for 12 hours in a hot air circulation dryer. The obtained powder was subjected to various evaluations using the methods described above, and the results are shown in Table 1. A film was also produced in the same manner as in Example 1. The evaluation results of the film are shown in Table 2.

[0083] [Comparative Example 1] A polycarbonate resin powder was produced in the same manner as in Example 4, except that the dihydric phenol was changed to 910 parts of BPC, 1,889 parts of BPA, and 53.27 parts of p-tert-butylphenol. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0084] Comparative Example 2 A polycarbonate resin powder was produced in the same manner as in Example 4, except that p-tert-butylphenol was changed to 70.76 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0085] Comparative Example 3 A polycarbonate resin powder was produced in the same manner as in Example 1, except that p-tert-butylphenol was changed to 51.26 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0086] Comparative Example 4 A polycarbonate resin powder was produced in the same manner as in Example 1, except that the dihydric phenol was changed to 2337 parts of BPC, 519 parts of BPA, and 54.68 parts of p-tert-butylphenol. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0087] Comparative Example 5 A polycarbonate resin powder was produced in the same manner as in Example 9, except that p-tert-butylphenol was changed to 27.89 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0088] Comparative Example 6 A polycarbonate resin powder was produced in the same manner as in Example 9, except that the amount of p-tert-butylphenol was changed to 88.84 parts. A film was also produced in the same manner as in Example 1. The evaluation results are shown in Tables 1 and 2.

[0089] Comparative Example 7 320 parts of the polycarbonate resin powder produced in Example 5 and 680 parts of the polycarbonate resin powder produced in Comparative Example 2 were dissolved in methylene chloride, and the resulting solution was placed in a kneader filled with warm water. The solvent was evaporated while stirring to obtain a polycarbonate blend powder. After dehydration, the mixture was dried at 100°C for 12 hours in a hot air circulation dryer. The obtained powder was subjected to various evaluations using the methods described above, and the results are shown in Table 1. A film was also produced using the same method as in Example 1. The film evaluation results are shown in Table 2. This film had the same copolymer composition and viscosity-average molecular weight as Example 7 and satisfied formula (4), but exhibited poor flex resistance. This was due to the fact that the polycarbonate copolymer (produced in Comparative Example 2) constituting the blend was a low-molecular-weight product that did not satisfy formula (4).

[0090] [Comparative Example 8] BPC homopolycarbonate resin powder (8-I) was obtained in the same manner as in Example 1, except that the amount of p-tert-butylphenol was changed to 49.56 parts. BPA homopolycarbonate resin powder (8-II) was also obtained in the same manner as in Example 9, except that the amount of p-tert-butylphenol was changed to 59.92 parts. 500 parts of resin powder (8-I) and 500 parts of resin powder (8-II) were dissolved in methylene chloride, and the solution was placed in a kneader filled with warm water. The solvent was evaporated while stirring to obtain a polycarbonate blend powder. After dehydration, the mixture was dried at 100°C for 12 hours in a hot air circulating dryer. The obtained powder was subjected to various evaluations using the methods described above, and the results are shown in Table 1. A film was also produced in the same manner as in Example 1. The evaluation results of the film are shown in Table 2. This film had the same copolymer composition and viscosity-average molecular weight as in Example 7 and satisfied formula (4), but exhibited poor flex resistance. This is because the BPC homopolycarbonate (8-I) constituting the blend is a low molecular weight substance that does not satisfy formula (4).

[0091] [Table 1]

[0092] [Table 2] [Industrial Applicability]

[0093] A film made of the polycarbonate resin of the present invention has excellent transparency, heat resistance, pencil hardness and flex resistance, and is useful as a display cover panel or touch panel for office automation and electronic equipment, and particularly as a cover window for flexible displays.

Claims

1. A film made of a polycarbonate resin having a pencil hardness of F or higher as measured in accordance with JIS K5600, the film comprising as main repeating units a repeating unit (A) derived from 2,2-bis(4-hydroxy-3-methylphenyl)propane and a repeating unit (B) derived from 2,2-bis(4-hydroxyphenyl)propane, the content of the repeating unit (A) being in the range of 40 to 100 mol % and the content of the repeating unit (B) being in the range of 0 to 60 mol %, the polycarbonate resin being a homopolycarbonate resin, a polycarbonate copolymer, or a polycarbonate blend, and the relationship between the viscosity average molecular weight (V) of the polycarbonate resin component constituting the homopolycarbonate resin, polycarbonate copolymer, or polycarbonate blend and the content (W mol %) of the repeating unit (A) satisfies the following formula (4): V≧80W+20,000 (4)

2. 2. The cover window of a flexible display device according to claim 1, wherein the polycarbonate resin has a glass transition temperature of 100 to 200°C.

3. 3. The cover window for a flexible display device according to claim 1, wherein the viscosity average molecular weight (V) of the polycarbonate resin is in the range of 22,000 to 65,000.

4. The cover window of a flexible display device according to any one of claims 1 to 3, wherein the polycarbonate resin has a molecular weight distribution (Mw / Mn), which is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn), measured by a GPC method, in the range of 1.3 to 4.

0.

5. A cover window for a flexible display device described in any one of claims 1 to 4, wherein the film has a thickness of 10 to 100 μm.

6. A cover window for a flexible display device described in any one of claims 1 to 5, wherein the film has been bent 200,000 times or more.

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