Method for manufacturing phase difference films

Abstract

To provide a method for manufacturing a retardation film, which can improve transportability of a resin film peeled from a supporting substrate.SOLUTION: A method for manufacturing a retardation film according to an embodiment of the present invention comprises: applying a resin solution containing a resin and a solvent onto a long supporting substrate, to produce a laminate with a coating layer having the supporting substrate and a coating layer provided on one side thereof; heating and drying the coating layer to produce a laminate with a primary resin layer having the supporting substrate and a primary resin layer provided on one side thereof; cooling the first resin layer to 50°C or less; heating and drying the first resin layer to produce a laminate with a second resin layer having the supporting substrate and a second resin layer provided on one side thereof; peeling the second resin layer from the supporting substrate to obtain a long resin film; and stretching the long resin film.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a method for manufacturing a phase difference film. [Background technology]

[0002] In recent years, image display devices, such as liquid crystal displays and electroluminescent (EL) displays (e.g., organic EL displays and inorganic EL displays), have become widespread. In organic EL displays, it is known that problems such as reflection of ambient light and reflection of the background can be prevented by placing a circular polarizer containing a λ / 4 plate on the viewing side of the organic EL cell (e.g., Patent Documents 1 and 2).

[0003] Regarding the λ / 4 plate used in the above-mentioned circular polarizer, from the viewpoint of achieving excellent anti-reflective properties over a wide wavelength range, there is a demand for a phase difference film that exhibits so-called inverse wavelength dispersion characteristics, where the in-plane phase difference is larger in the longer wavelength range. In response to this demand, a technique has been proposed to obtain a phase difference film in which the in-plane phase difference exhibits inverse wavelength dispersion characteristics by stretching a resin film obtained by coating and drying a resin solution containing a cellulose-based resin exhibiting positive birefringence and an ester-based resin exhibiting negative birefringence onto a support substrate (Patent Document 3). [Prior art documents] [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Publication No. 2002-311239 [Patent Document 2] Japanese Patent Publication No. 2002-372622 [Patent Document 3] Japanese Patent Publication No. 2021-140095 [Overview of the project] [Problems that the invention aims to solve]

[0005] The resin film obtained by applying and drying the resin solution onto a support substrate and then peeling it off the substrate tends to curl upwards at the edges. This can lead to transport problems, such as difficulty in winding it onto a roll or inability to properly grip it with a tenter clip when stretching it using a tenter stretching device (poor chucking).

[0006] The present invention was made to solve the above problems, and its primary objective is to provide a method for manufacturing a phase difference film that can improve the transportability of a resin film peeled from a support substrate. A secondary objective of the present invention is to provide a method for manufacturing a phase difference film in which the in-plane phase difference exhibits inverse wavelength dispersion characteristics and has high orientation. [Means for solving the problem]

[0007] According to one aspect of the present invention, a method for manufacturing a phase difference film is provided, comprising: applying a resin solution containing a resin and a solvent onto a long support substrate to produce a laminate with a coating layer having the support substrate and a coating layer provided on one side thereof; heating and drying the coating layer to produce a laminate with a primary resin layer having the support substrate and a primary resin layer provided on one side thereof; cooling the primary resin layer to 50°C or below; heating and drying the primary resin layer to produce a laminate with a secondary resin layer having the support substrate and a secondary resin layer provided on one side thereof; peeling the secondary resin layer from the support substrate to obtain a long resin film; and stretching the long resin film. In one embodiment, the thickness of the phase difference film is 10 μm or more. In one embodiment, the resin is a thermoplastic resin. In one embodiment, the birefringence ΔP(590) in the thickness direction of the resin film before stretching at a measurement wavelength of 590 nm exceeds 0.0005. In one embodiment, the ratio (Rth(450) / Rth(550)) of the phase difference in the thickness direction of the resin film before stretching at a measurement wavelength of 450 nm to the phase difference in the thickness direction at a measurement wavelength of 550 nm is less than 1.00. In one embodiment, the resin film comprises a cellulose-based resin and an ester-based resin, and a nanophase separation structure is formed in the phase difference film. In one embodiment, the cellulose resin has the structural units shown in formula (1) below, and the ester resin has the structural units shown in formula (2) below and the structural units shown in formula (3) below: [ka] (In formula (1), each of R1 to R3 represents a hydrogen atom or a substituent having 1 to 12 carbon atoms;) [ka] (In formula (2), R4 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R 5a R represents one selected from an alkyl group having 1 to 12 carbon atoms, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group; R 5b R6 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R6 represents a species selected from a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amide group, an amino group, a hydroxyl group, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms;) [ka] (In formula (3), R7 represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the above five-membered heterocyclic residue and the above six-membered heterocyclic residue may form a fused ring structure with other cyclic structures)). In one embodiment, the ester resin further comprises the constituent units shown in the following formula (4): [ka] (In formula (4), each of R8 and R9 represents one selected from a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms). In one embodiment, the solvent content in the secondary resin layer is 50% or less of the solvent content in the primary resin layer. In one embodiment, the laminate with the primary resin layer is wound around a roll, and then unwound from the roll to subject the primary resin layer to the heat drying.

Advantages of the Invention

[0008] In the method for producing a retardation film according to an embodiment of the present invention, a resin film obtained by heating and drying a coating layer of a resin solution, once cooling it, and then heating and drying it again is used for stretching. Since such a resin film has a low residual solvent amount, curling at the ends is suppressed, and as a result, problems with conveyance such as poor chucking are unlikely to occur. Further, according to the method for producing a retardation film according to an embodiment of the present invention, a retardation film having an in-plane retardation showing inverse wavelength dispersion characteristics and high orientation can be suitably obtained.

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described, but the present invention is not limited to these embodiments. In this specification, "~" representing a numerical range includes the upper and lower limit numerical values. Further, in this specification, when "weight" is mentioned, it is synonymous with "mass" which is the SI unit system meaning weight.

[0010] (Definition of Terms and Symbols) The definitions of the terms and symbols in this specification are as follows. (1) Refractive Index (nx, ny, nz) "nx" is the refractive index in the direction in which the in-plane refractive index is maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis in the plane (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-Plane Birefringence (Δn) "Δn(λ)" is the in-plane birefringence measured with light of wavelength λnm at 23℃. The in-plane birefringence (Δn) can be calculated from the formula: Δn = nx - ny. (3) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured with light of wavelength λnm at 23°C. For example, "Re(550)" is the in-plane phase difference measured with light of wavelength 550nm at 23°C. Re(λ) can be calculated using the formula: Re(λ) = (nx - ny) × d, where d (nm) is the thickness of the layer (film). (4) Birefringence in the thickness direction (ΔP) "ΔP(λ)" is the birefringence in the thickness direction measured with light of wavelength λnm at 23℃. The birefringence in the thickness direction (ΔP) can be calculated from the formula: ΔP = nx - nz. (5) Phase difference in the thickness direction (Rth) "Rth(λ)" is the phase difference in the thickness direction measured with light of wavelength λnm at 23°C. For example, "Rth(550)" is the phase difference in the thickness direction measured with light of wavelength 550nm at 23°C. Rth(λ) can be calculated using the formula: Rth(λ) = (nx - nz) × d, where d (nm) is the thickness of the layer (film). (6) Nz coefficient The Nz coefficient is calculated using the formula Nz = Rth / Re.

[0011] A. Method for manufacturing phase difference film The method for manufacturing a phase difference film according to an embodiment of the present invention is: A resin solution containing resin and solvent is applied to a long support substrate to produce a laminate with a coated layer having the support substrate and a coated layer provided on one side thereof. The coated layer is heated and dried to produce a laminate with a primary resin layer having the support substrate and a primary resin layer provided on one side thereof. The primary resin layer is cooled to 50°C or below. The primary resin layer is heated and dried to produce a laminate with a secondary resin layer having the support substrate and a secondary resin layer provided on one side thereof. The secondary resin layer is peeled off the support substrate to obtain a long resin film, and Stretching the elongated resin film, Includes. The following describes in detail a method for manufacturing a phase difference film according to embodiments of the present invention. In this description, the heat drying performed on the coating layer and the heat drying performed on the primary resin layer may be referred to as "primary drying" and "secondary drying," respectively.

[0012] A-1. Fabrication of laminated bodies with coated layers The laminate with a coated layer comprises a support substrate and a coated layer provided on one side thereof. The laminate with a coated layer is manufactured by applying a resin solution containing a resin and a solvent onto a long support substrate. In this specification, "long" means an elongated shape in which the length is sufficiently longer than the width, and includes, for example, an elongated shape in which the length is 10 times or more, preferably 20 times or more, than the width. The long film can be wound into a roll.

[0013] A-1-1. Resin solution The resin solution is prepared by dissolving the resin in a solvent. The resin solution may contain any other suitable components as needed.

[0014] Typical examples of the resins used are thermoplastic resins. As will be described later, from the viewpoint of obtaining a resin film that exhibits so-called inverse wavelength dispersion characteristics, which has a certain level of birefringence in the thickness direction and in which the phase difference in the thickness direction increases with increasing wavelength of the measured light, it is preferable to use a combination of a cellulose-based resin that exhibits positive birefringence and an ester-based resin that exhibits negative birefringence. Note that "exhibiting positive birefringence" means that when the polymer is oriented by stretching or the like, the refractive index in the direction perpendicular to the stretching direction becomes relatively small. In other words, it means that the refractive index in the stretching direction becomes large. "Exhibiting negative birefringence" means that when the polymer is oriented by stretching or the like, the refractive index in the stretching direction becomes relatively small. In other words, it means that the refractive index in the direction perpendicular to the stretching direction becomes large.

[0015] The cellulose-based resin exhibiting the above-mentioned positive birefringence is not limited as long as the effects of the present invention are obtained, and for example, cellulose, cellulose derivatives, etc., can be used. Examples of cellulose derivatives include cellulose ethers in which at least some of the hydroxyl groups of cellulose are etherified, and cellulose ether esters in which at least some of the hydroxyl groups are esterified. Among these, cellulose ether can be preferably used. The cellulose-based resin may be used alone or in combination of two or more types.

[0016] Cellulose resins are typically polymers in which β-glucose units are polymerized in a linear manner, and have the constituent units shown in the following formula (1). [ka] (In formula (1), each of R1 to R3 represents a hydrogen atom or a substituent having 1 to 12 carbon atoms).

[0017] Examples of substituents having 1 to 12 carbon atoms represented by R1 to R3 in formula (1) above include alkyl groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, decanyl, dodecanyl, isobutyl, and t-butyl groups; cycloalkyl groups such as cyclohexyl groups; aryl groups such as phenyl and naphthyl groups; aralkyl groups such as benzyl groups; acyl groups such as acetyl and propionyl groups; cyanoalkyl groups such as cyanoethyl groups; aminoalkyl groups such as aminoethyl groups; and hydroxyalkyl groups such as 2-hydroxyethyl and 3-hydroxypropyl groups. In equation (1) above, R1 to R3 may be the same or different from each other. Preferably, R1 to R3 in formula (1) above are a hydrogen atom and an alkyl group having 1 to 12 carbon atoms, more preferably a hydrogen atom and an alkyl group having 1 to 4 carbon atoms, and even more preferably a hydrogen atom and an ethyl group.

[0018] The degree of substitution (hereinafter referred to as DS) of cellulose resins is typically between 1.5 and 2.95, preferably between 1.8 and 2.8. DS represents the percentage of hydroxyl groups substituted in the cellulose resin, with DS being 3 when 100% substitution occurs. DS can be calculated from the peak area of ​​gas chromatography, as described in the 17th edition of the Japanese Pharmacopoeia.

[0019] The number-average molecular weight (Mn) of cellulose resins, in terms of standard polystyrene equivalent, is, for example, 1 × 10⁻⁶. 3 The above 1 x 10 6 The following is preferably 5 × 10 3 The above 2 x 10 5 The following applies: The manganese content (Mn) of cellulose-based resins can be calculated from the elution curve measured by gel permeation chromatography (GPC). If the Mn content of the cellulose-based resin falls within the above range, the mechanical properties and / or moldability of the resin film can be improved.

[0020] The glass transition temperature (Tg) of cellulose-based resins is, for example, 140°C or lower, preferably 135°C or lower, and for example, 120°C or higher, preferably 125°C or higher. The glass transition temperature (Tg) of cellulose-based resins can be measured by a thermal analyzer such as a DSC (Differential Scanning Calorimetry).

[0021] Specific examples of cellulosic resins include alkylcellulose such as methylcellulose, ethylcellulose, and propylcellulose; hydroxyalkylcellulose such as hydroxyethylcellulose and hydroxypropylcellulose; aralkylcellulose such as benzylcellulose; cyanoalkylcellulose such as cyanoethylcellulose; carboxyalkylcellulose such as carboxymethylcellulose and carboxyethylcellulose; carboxyalkylalkylcellulose such as carboxymethylmethylcellulose and carboxymethylethylcellulose; and aminoalkylcellulose such as aminoethylcellulose. Cellulosic resins can be used alone or in combination. Among cellulose-based resins, alkylcellulose is preferred, and ethylcellulose is more preferred.

[0022] The ester resin exhibiting negative birefringence described above is not limited as long as the effects of the present invention are obtained. For example, an ester resin having the constituent units shown in formula (2) and the constituent units shown in formula (3) below can be used. The ester resin exhibiting negative birefringence may be used alone or in combination of two or more types. [ka] (In formula (2), R4 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R 5a R represents one selected from an alkyl group having 1 to 12 carbon atoms, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group; R 5b R6 represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; R6 represents a species selected from a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amide group, an amino group, a hydroxyl group, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms. [ka] (In formula (3), R7 represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the above five-membered heterocyclic residue and the above six-membered heterocyclic residue may form a fused ring structure with other cyclic structures).)

[0023] The structural unit shown in the above formula (2) is a cinnamic acid ester residue unit. Examples of the alkyl group having 1 to 12 carbon atoms represented by R4 in the above formula (2) include a methyl group, an ethyl group, an isopropyl group, an n-propyl group, an n-butyl group, an s-butyl group, a t-butyl group, an isobutyl group, and an ethylhexyl group. Among R4 in the above formula (2), preferably, an alkyl group having 1 to 4 carbon atoms is exemplified, and more preferably, an ethyl group and an isobutyl group are exemplified. Among R of the above formula (2) 5a , preferably, an alkyl group having 1 to 12 carbon atoms and a cyano group are exemplified, more preferably, an alkyl group having 1 to 4 carbon atoms and a cyano group are exemplified, and still more preferably, a cyano group is exemplified. Among R of the above formula (2) 5b , preferably, a hydrogen atom and an alkyl group having 1 to 4 carbon atoms are exemplified. R6 in the above formula (2) may be bonded to the benzene ring only once or may be bonded to the benzene ring two or more times. Among R6 in the above formula (2), preferably, a carboxylic acid group and a hydroxy group are exemplified.

[0024] Specific examples of the constituent units (cinnamic acid ester residue units) shown in formula (2) above include α-cyano-4-hydroxycinnamate methyl residue unit, α-cyano-2-hydroxycinnamate ethyl residue unit, α-cyano-3-hydroxycinnamate ethyl residue unit, α-cyano-4-hydroxycinnamate ethyl residue unit, α-cyano-4-hydroxycinnamate n-propyl residue unit, α-cyano-4-hydroxycinnamate isopropyl residue unit, α-cyano-4-hydroxycinnamate n-butyl residue unit, and α-cyano-4-hydroxycinnamate α-cyano-hydroxycinnamic acid ester residue units such as isobutyl hydroxycinnamate residue units, α-cyano-4-hydroxycinnamate s-butyl residue units, and α-cyano-2,4-dihydroxycinnamate methyl residue units; α-cyano-carboxycinnamic acid ester residue units such as α-cyano-4-carboxycinnamate methyl residue units, α-cyano-4-carboxycinnamate ethyl residue units, α-cyano-2,3-dicarboxycinnamate methyl residue units, and α-cyano-2,3-dicarboxycinnamate ethyl residue units; α-Cyano-2-carboxy-3-hydroxycinnamate methyl residue unit, α-Cyano-2-carboxy-3-hydroxycinnamate ethyl residue unit, and other α-Cyano-2-carboxy-3-hydroxycinnamate ethyl residue unit; 3-alkyl-3-(hydroxyphenyl)-propa-2-enoate methyl residue unit, 3-ethyl-3-(hydroxyphenyl)-propa-2-enoate ethyl residue unit, and other 3-alkyl-3-(hydroxyphenyl)-propa-2-enoate ethyl residue unit; 3-methyl-3-(carboxyphenyl 3-alkyl-3-(carboxyphenyl)-propa-2-enoic acid ester residue units such as methyl methyl residue units and ethyl ethyl ethyl 3-ethyl-3-(carboxyphenyl)-propa-2-enoic acid residue units; 2-cyano-3-alkyl-3-(hydroxyphenyl)-propa-2-enoic acid ester residue units such as methyl methyl 2-cyano-3-methyl-3-(hydroxyphenyl)-propa-2-enoic acid residue units and ethyl ethyl 2-cyano-3-ethyl-3-(hydroxyphenyl)-propa-2-enoic acid residue units;Examples include 2-cyano-3-alkyl-3-(carboxyphenyl)-propa-2-enoic acid ester residue units such as 2-cyano-3-methyl-3-(carboxyphenyl)-propa-2-enoic acid methyl residue units and 2-cyano-3-ethyl-3-(carboxyphenyl)-propa-2-enoic acid ethyl residue units.

[0025] The ester resin may contain only one of the constituent units shown in formula (2) above, or it may contain two or more. Among the constituent units shown in formula (2) above, preferred examples include α-cyano-hydroxycinnamic acid ester residue units, α-cyano-carboxycinnamic acid ester residue units, 3-alkyl-3-(hydroxyphenyl)-propa-2-enoic acid ester residue units, and 3-alkyl-3-(carboxyphenyl)-propa-2-enoic acid ester residue units.

[0026] The content of the constituent units of formula (2) in the ester resin is, for example, 21 mol% or more, for example, 70 mol% or less, preferably 60 mol% or less, and more preferably 49 mol% or less. The content of each constituent unit in the ester resin is, for example, 1 It can be measured by 1H-NMR.

[0027] Specific examples of the ring structure represented by R7 in formula (3) above include 1-vinylpyrrole residue units, 2-vinylpyrrole residue units, 1-vinylindole residue units, 9-vinylcarbazole residue units, 2-vinylquinoline residue units, 4-vinylquinoline residue units, N-vinylphthalimide residue units, N-vinylsuccinimide residue units, 2-vinylfuran residue units, and 2-vinylbenzofuran residue units, with 9-vinylcarbazole residue units and N-vinylphthalimide residue units being preferred.

[0028] The ester resin may contain only one of the constituent units shown in formula (3) above, or it may contain two or more. The content of the constituent unit of formula (3) in the ester resin is, for example, 21 mol% or more, preferably 35 mol% or more, and for example, 70 mol% or less, preferably 60 mol% or less.

[0029] The ester resin preferably has, in addition to the constituent units shown in (2) and (3) above, the constituent unit shown in the following formula (4). [ka] (In formula (4), R8 and R9 each represent one selected from a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms.) In formula (4) above, examples of linear alkyl groups having 1 to 12 carbon atoms represented by R8 and R9 include methyl group, ethyl group, n-propyl group, n-butyl group, n-pentyl group, n-hexyl group, and the like. In formula (4) above, examples of branched alkyl groups having 3 to 12 carbon atoms represented by R8 and R9 include isopropyl group, isobutyl group, sec-butyl group, tert-butyl group, etc. In formula (4) above, examples of cyclic alkyl groups having 3 to 6 carbon atoms represented by R8 and R9 include cyclopropyl group, cyclobutyl group, and cyclohexyl group. In equation (4) above, R8 and R9 may be the same or different from each other. In formula (4) above, R8 is preferably a hydrogen atom and a linear alkyl group having 1 to 12 carbon atoms, and more preferably a hydrogen atom and a methyl group. In formula (4) above, R9 is preferably a branched alkyl group having 3 to 12 carbon atoms, and more preferably a branched alkyl group having 3 to 8 carbon atoms.

[0030] The constituent units shown in formula (4) above are typically acrylic resin residue units. Specific examples of the constituent units shown in formula (4) above include acrylic acid residue units, methacrylic acid residue units, 2-ethyl acrylic acid residue units, 2-propyl acrylic acid residue units, 2-isopropyl acrylic acid residue units, 2-pentyl acrylic acid residue units, 2-hexyl acrylic acid residue units, methyl acrylate residue units, ethyl acrylate residue units, n-propyl acrylate residue units, isopropyl acrylate residue units, n-butyl acrylate residue units, isobutyl acrylate residue units, sec-butyl acrylate residue units, n-pentyl acrylate residue units, isopentyl acrylate residue units, sec-pentyl acrylate residue units, 3-pentyl acrylate residue units, neopentyl acrylate residue units, n-hexyl acrylate residue units, isohexyl acrylate residue units, neohexyl acrylate residue units, methyl methacrylate residue units, ethyl methacrylate residue units, and methacrylate residue units. Examples include n-propyl methacrylate residue units, isopropyl methacrylate residue units, n-butyl methacrylate residue units, isobutyl methacrylate residue units, sec-butyl methacrylate residue units, n-pentyl methacrylate residue units, isopentyl methacrylate residue units, sec-pentyl methacrylate residue units, 3-pentyl methacrylate residue units, neopentyl methacrylate residue units, n-hexyl methacrylate residue units, isohexyl methacrylate residue units, neohexyl methacrylate residue units, methyl 2-ethylacrylate residue units, ethyl 2-ethylacrylate residue units, n-propyl 2-ethylacrylate residue units, isopropyl 2-ethylacrylate residue units, n-butyl 2-ethylacrylate residue units, isobutyl 2-ethylacrylate residue units, sec-butyl 2-ethylacrylate residue units, and the like, with isobutyl acrylate residue units being preferred.

[0031] The ester resin may contain only one of the constituent units shown in formula (4) above, or it may contain two or more. The content of the constituent unit of formula (4) in the ester resin is, for example, 0 mol% or more, preferably 1 mol% or more, and for example, 30 mol% or less.

[0032] Ester resins may contain monomer residue units other than those of formulas (2) to (4) above. Examples of such monomer residue units include styrene residues such as styrene residues and α-methylstyrene residues; vinylnaphthalene residues; vinyl ester residues such as vinyl acetate residues and vinyl propionate residues; vinyl ether residues such as methyl vinyl ether residues, ethyl vinyl ether residues and butyl vinyl ether residues; N-substituted maleimide residues such as N-methylmaleimide residues, N-cyclohexylmaleimide residues and N-phenylmaleimide residues; acrylonitrile residues; methacrylonitrile residues; fumarate ester residues; fumarate residues; and olefin residues such as ethylene residues and propylene residues.

[0033] The number-average molecular weight (Mn) of ester resins on a standard polystyrene basis is, for example, 1 × 10⁻⁶. 3 The above 5 x 10 6 The following is preferably 5 × 10 3 The above 3 x 10 5 The following applies: The manganese (Mn) content of ester resins can be calculated from the elution curve measured by gel permeation chromatography (GPC). If the Mn content of the ester resin falls within the above range, the mechanical properties and / or moldability of the resin film can be improved.

[0034] The glass transition temperature (Tg) of ester resins is, for example, 220°C or lower, preferably 210°C or lower, and for example, 180°C or higher, preferably 190°C or higher. The glass transition temperature (Tg) of ester resins can be measured by a thermal analyzer such as a DSC (Differential Scanning Calorimetry).

[0035] Specific examples of such ester resins include α-cyano-2-hydroxycinnamic acid ester-styrene-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-1-vinylindole-acrylic acid ester copolymer, α-cyano-2-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-styrene-acrylic acid ester copolymer, α -Cyano-3-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-1-vinylindole-acrylic acid ester copolymer, α-cyano-3-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-styrene-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester-2-vinylnaphthalene-acrylic acid ester copolymer, α-cyano-4-hydroxycinnamic acid ester Stel-1-vinylindole-acrylic acid copolymer, α-cyano-4-hydroxycinnamic acid ester-9-vinylcarbazole-acrylic acid copolymer, α-cyano-2-hydroxycinnamic acid ester-styrene-methacrylic acid copolymer, α-cyano-2-hydroxycinnamic acid ester-2-vinylnaphthalene-methacrylic acid copolymer, α-cyano-2-hydroxycinnamic acid ester-1-vinylindole-methacrylic acid copolymer, α-cyano-2-hydroxycinnamic acid ester-9-vinylcarbazole α-Cyano-3-hydroxycinnamic acid-styrene-methacrylic acid copolymer, α-Cyano-3-hydroxycinnamic acid-2-vinylnaphthalene-methacrylic acid copolymer, α-Cyano-3-hydroxycinnamic acid-1-vinylindole-methacrylic acid copolymer, α-Cyano-3-hydroxycinnamic acid-9-vinylcarbazole-methacrylic acid copolymer, α-Cyano-4-hydroxycinnamic acid-styrene-methacrylic acid copolymer,Examples include α-cyano-4-hydroxycinnamic acid ester-2-vinylnaphthalene-methacrylate copolymer, α-cyano-4-hydroxycinnamic acid ester-1-vinylindole-methacrylate copolymer, and α-cyano-4-hydroxycinnamic acid ester-9-vinylcarbazole-methacrylate copolymer.

[0036] The content of the cellulose-based resin in the resin solution (and consequently, the content of the cellulose-based resin in the resin film) is typically more than 50% by mass, preferably 70% by mass or more, and more preferably 80% by mass or more, when the total amount of the cellulose-based resin and ester-based resin is taken as 100% by mass. The upper limit of the cellulose-based resin content is typically 90% by mass or less. If the cellulose-based resin content is above the lower limit, a resin film can be obtained that has a certain level of birefringence in the thickness direction and exhibits inverse wavelength dispersion characteristics in the phase difference in the thickness direction. Furthermore, the cellulose-based resin and ester-based resin can stably form a nanophase separation structure in the obtained resin film. A phase difference film obtained by stretching a resin film having a nanophase separation structure also has a nanophase separation structure, thereby suppressing rapid shrinkage in high temperature and high humidity environments (for example, 110°C and 85% RH (relative humidity)).

[0037] In this specification, "nanophase separation structure" refers to a structure in which two components with different electron densities are phase-separated by domain sizes on the nano-order (typically at the level of several tens of nanometers). The resin exhibiting positive birefringence (cellulose-based resin) and the resin exhibiting negative birefringence (ester-based resin) may be in a sea-island structure or a co-continuous structure. Examples of means for confirming the nanophase separation structure include transmission electron microscopy (TEM), scanning electron microscopy (SEM), atomic force microscopy (AFM), and small-angle X-ray scattering (SAXS), with TEM observation of a film cross-section being preferred. When a nanophase separation structure is formed in the film under observation, two types of domains with different electron densities can be confirmed by TEM observation of the film cross-section, and it can be confirmed that the size (maximum length) of all domains is less than 100 nm.

[0038] Other components listed above may be appropriately selected depending on the purpose. Examples of other components include antioxidants such as hindered phenol antioxidants, phosphorus antioxidants, sulfur antioxidants, lactone antioxidants, amine antioxidants, hydroxylamine antioxidants, vitamin E antioxidants, and other antioxidants; hindered amine light stabilizers; UV absorbers such as benzotriazole, benzophenone, triazine, and benzoate; surfactants; polymer electrolytes; conductive complexes; pigments; dyes; antistatic agents; antiblocking agents; and lubricants. The content ratio of other components is, for example, 0.01 to 0.3 parts by weight per 100 parts by weight of the resin component.

[0039] As for the solvent, from the viewpoint of minimizing solvent residue on the resin film, a solvent with a boiling point of 200°C or lower is preferred, and a solvent with a boiling point of 170°C or lower is more preferred. Specific examples of solvents include halogenated hydrocarbons such as chloroform, dichloromethane, carbon tetrachloride, dichloroethane, tetrachloroethane, trichloroethylene, tetrachloroethylene, chlorobenzene, and dichlorobenzene; phenols such as phenol and chlorophenol; aromatic hydrocarbons such as benzene, toluene, xylene, methoxybenzene, mesitylene, and dimethoxybenzene; ketone solvents such as acetone, methyl ethyl ketone, methyl isobutyl ketone (MIBK), cyclohexanone, cyclopentanone (CPN), 2-pyrrolidone, and N-methyl-2-pyrrolidone; ester solvents such as ethyl acetate and butyl acetate; and butanol, t-butyl alcohol, glycerin, and ethyl acetate. Examples of solvents include alcohol-based solvents such as ethylene glycol, triethylene glycol, ethylene glycol monomethyl ether, diethylene glycol dimethyl ether, propylene glycol, dipropylene glycol, and 2-methyl-2,4-pentanediol; amide-based solvents such as dimethylformamide and dimethylacetamide; nitrile-based solvents such as acetonitrile and butyronitrile; ether-based solvents such as 1,3-dioxolane, cyclopentyl methyl ether (CPME), propylene glycol methyl ether acetate (PGMEA), diethyl ether, dibutyl ether, and tetrahydrofuran; carbon disulfide, ethyl cellosolve, butyl cellosolve, and mixtures thereof.

[0040] Among the solvents, mixed solvents are preferred. Examples of mixed solvent combinations include ester solvent / aromatic hydrocarbons, ether solvent / aromatic hydrocarbons, ester solvent / ether solvent, ester solvent / alcohol solvent, ester solvent / ketone solvent, two types of ether solvents, and two types of ester solvents.

[0041] More preferably, the mixed solvent is an ester solvent / aromatic hydrocarbon, even more preferably ethyl acetate / toluene, and particularly preferably a mixed solvent of ethyl acetate / toluene = 40% by mass / 60% by mass to 60% by mass / 40% by mass. When the solvent is such a mixed solvent, the cellulose resin and the ester resin can form a nanophase separation structure more stably in the phase difference film.

[0042] The solid content concentration of the resin solution is, for example, 1% to 30% by weight, preferably 5% to 30% by weight, and more preferably 10% to 24% by weight.

[0043] The viscosity of the resin solution is preferably 100 cps to 30,000 cps, more preferably 300 cps to 20,000 cps, and even more preferably 500 cps to 15,000 cps, from the viewpoint of productivity and moldability. The viscosity of the resin solution can be adjusted by the molecular weight and concentration of each component, the type of solvent, etc.

[0044] A-1-2. Supporting base material Examples of supporting substrates include polymer substrates made of polyester, polycarbonate, polystyrene, polyethylene, polypropylene, polyvinyl chloride, polyvinylidene chloride, triacetylcellulose, polyvinyl alcohol, polyimide, polyarylate, polysulfone, polyethersulfone, epoxy resins, etc.; glass substrates such as glass plates and quartz substrates; metal substrates such as aluminum, stainless steel, and ferrotype; and inorganic substrates such as ceramic substrates. The above substrates are preferably polymer substrates or metal substrates.

[0045] A-1-3. Application The coating method is not particularly limited, and conventional methods can be used. Examples include the T-die method, doctor blade method, bar coater method, slot die method, lip coater method, reverse gravure coating method, microgravure method, spin coating method, brush coating method, roll coating method, and flexographic printing method. Molding conditions can be appropriately set according to the composition and type of resin used, the desired properties of the resin film, etc.

[0046] The coating thickness of the resin solution (thickness of the coated layer) is, for example, 50 μm to 1000 μm, preferably 50 μm to 900 μm, more preferably 70 μm to 800 μm, and even more preferably 100 μm to 700 μm (for example, 300 μm to 700 μm). If the coating thickness is within this range, the film thickness after stretching can be ensured without significantly reducing the in-plane orientation per unit thickness, and for example, the in-plane phase difference characteristics required for a λ / 4 plate can be secured.

[0047] A-2. Fabrication of a laminate with a primary resin layer The laminate with the primary resin layer comprises a support substrate and a primary resin layer provided on one side thereof. The laminate with the primary resin layer is manufactured, for example, by subjecting the laminate with the coated layer to a heated environment and heating and drying the coated layer. Specifically, the primary resin layer is obtained by reducing the solvent content in the coated layer through heating and drying.

[0048] Typically, the production of laminates with a coated layer and laminates with a primary resin layer are carried out on the same conveyor line. Specifically, long laminates with a coated layer undergo heating and drying of the coated layer, for example, within the coating equipment or on the conveyor line, before being wound onto rolls by a winding device, to become laminates with a primary resin layer.

[0049] The solvent content in the primary resin layer is, for example, 3% to 30% by weight, preferably 3% to 20% by weight, and more preferably 3% to 10% by weight. In one embodiment, the solvent content in the primary resin layer is, for example, greater than 3% by weight, and also greater than 4% by weight.

[0050] The thickness of the primary resin layer is, for example, 55 μm to 220 μm, preferably 75 μm to 200 μm, and more preferably 105 μm to 200 μm.

[0051] The reduction rate (R1) of solvent content (by weight) during primary drying is, for example, 59% to 99%, preferably 75% to 99%, and more preferably 87% to 99%. Here, the reduction rate (R1) of solvent content is calculated using the formula: R1 (%) = (solvent content of the coating layer - solvent content of the primary resin layer) / solvent content of the coating layer × 100. The solvent content of the coating layer substantially corresponds to the solvent content of the resin solution.

[0052] Primary drying may be performed at a constant temperature or while the temperature is varied. For example, primary drying may be performed by gradually or stepwise increasing the temperature. The heating temperature (or, if drying is performed at a varying temperature, a weighted average with processing time at each temperature) is, for example, 60°C to 140°C, preferably 70°C to 140°C, more preferably 70°C to 130°C, and even more preferably 70°C to 100°C.

[0053] The drying time can be appropriately set depending on the type of solvent, the thickness of the coating layer, the solvent content of the coating layer, etc. The drying time is, for example, 60 seconds to 1200 seconds, preferably 60 seconds to 900 seconds, and more preferably 90 seconds to 900 seconds.

[0054] When primary drying is performed with a stepwise increase in temperature, the heating temperature for the first stage is set to, for example, 35°C to 65°C, preferably 45°C to 65°C, and the heating time for the first stage is set to, for example, 1 minute to 30 minutes, preferably 1 minute to 8 minutes. Thereafter, the heating temperature is increased in each stage, for example, 10°C to 130°C, preferably 10°C to 40°C. The heating time for each stage from the second stage onward is typically shorter than the heating time for the first stage, preferably 20 seconds to 20 minutes, more preferably 30 seconds to 5 minutes. The number of stages in primary drying is preferably 2 to 4, more preferably 3 or less. The maximum temperature in primary drying is, for example, 165°C or less, preferably less than 130°C, more preferably less than 120°C, even more preferably 115°C or less, and for example, 100°C or higher. By performing primary drying in multiple stages as described above, a resin film having a nanophase separation structure (ultimately a phase difference film) can be suitably obtained.

[0055] Any suitable heating method can be used during the heating and drying process. Specific examples of heating methods include hot air blowers, heating rollers, and far-infrared heaters.

[0056] By performing primary drying under the conditions described above, a resin film having desirable orientation (for example, wavelength dispersion characteristics of ΔP and Rth as described in Section A-5) can be suitably obtained as the raw material film to be stretched.

[0057] A-3. Cooling of the primary resin layer Next, the primary resin layer is cooled to 50°C or below, preferably 40°C or below, and more preferably 30°C or below (for example, room temperature (23°C)). By cooling the primary resin layer produced by primary drying, the orientation of the resin and the nanophase separation structure can be immobilized, and these can be maintained during the subsequent secondary drying while the solvent content can be sufficiently reduced.

[0058] The primary resin layer can be cooled, for example, by subjecting the laminate with the primary resin layer to natural cooling, forced air cooling, or the like. In one embodiment, the laminate with the primary resin layer is wound onto a roll, then unwound from the roll, and subjected to heat drying of the primary resin layer. According to this embodiment, even without any special cooling treatment, the temperature of the primary resin layer can be reduced to 50°C or below during winding onto and unwound from the roll. Furthermore, compared to natural cooling on the conveyor line, the line length can be shortened, enabling space savings.

[0059] The winding speed, winding tension, and unwinding speed of the laminate with the primary resin layer are not particularly limited and can be within the range commonly used.

[0060] The roll from which the primary resin-coated laminate has been wound may be immediately unwound and used to produce the secondary resin-coated laminate, or it may be stored for a predetermined period (for example, one day or more) before being used to produce the secondary resin-coated laminate.

[0061] Winding onto rolls and storing the rolls can be carried out, for example, in a temperature environment of 0°C to 50°C, preferably 5°C to 40°C.

[0062] A-4. Fabrication of a laminate with a secondary resin layer The laminate with a secondary resin layer comprises a support substrate and a secondary resin layer provided on one side thereof. The laminate with a secondary resin layer is manufactured, for example, by subjecting the laminate with a primary resin layer to a heated environment and heating and drying the primary resin layer. By reducing the solvent content in the primary resin layer through heating and drying, the primary resin layer becomes the secondary resin layer.

[0063] The solvent content in the secondary resin layer is, for example, 0% to 4% by weight, preferably 0% to 3% by weight, and more preferably 0% to 2% by weight. When the solvent content is within the above range, it is possible to reduce the curl that occurs at the edges of the resin film obtained by peeling the secondary resin layer from the support substrate over time (for example, between peeling and being transported to the stretching device).

[0064] The reduction rate (R2) of solvent content (by weight) during secondary drying is, for example, 50% or more. In other words, the solvent content in the secondary resin layer is 50% or less of the solvent content in the primary resin layer. The reduction rate (R2) of solvent content is preferably 50% to 100%, more preferably 70% to 100%. Here, the reduction rate (R2) of solvent content is calculated using the formula: R2(%) = (solvent content of primary resin layer - solvent content of secondary resin layer) / solvent content of primary resin layer × 100. When the reduction rate of solvent content is within the above range, a suitable effect of suppressing curl at the film edges can be obtained without disturbing the orientation exhibited in the primary resin layer.

[0065] Secondary drying may be performed at a constant temperature or while the temperature is varied. For example, secondary drying may be performed by gradually or stepwise increasing the temperature. The heating temperature (a weighted average with processing time at each temperature as the weight if drying is performed at a varying temperature) is, for example, 110°C or higher, preferably 120°C or higher, more preferably 130°C or higher, and for example, 180°C or lower, preferably 165°C or lower, more preferably 150°C or lower, and even more preferably 140°C or lower. The heating temperature in secondary drying is typically higher than the highest heating temperature in primary drying. In one embodiment, secondary drying is performed at a constant temperature.

[0066] The drying time can be appropriately set depending on the type of solvent, the thickness of the primary resin layer, the solvent content of the primary resin layer, etc. The drying time is, for example, 1 minute or more, preferably 5 minutes or more, more preferably 15 minutes or more, and for example, 60 minutes or less, preferably 45 minutes or less.

[0067] Any suitable heating method can be used during the heating and drying process. Specific examples of heating methods include hot air blowers, heating rollers, and far-infrared heaters.

[0068] A-5. Preparation of resin film A long resin film is obtained by peeling the secondary resin layer from the support substrate of a laminate with a secondary resin layer. The solvent content of the obtained resin film is typically less than or equal to the solvent content of the secondary resin layer. In resin films obtained by peeling and drying the primary resin layer from the support without subjecting it to secondary drying, the edges may curl over time after peeling, potentially leading to poor transport and chucking. However, by peeling the secondary resin layer, in which the residual solvent content has been sufficiently reduced, from the support, curling at the edges of the obtained resin film can be suppressed, resulting in better transport and chucking thereafter. Furthermore, while changes in solvent content during stretching can change the stress generated in the resin film, a resin film with a low solvent content suppresses such stress changes, thus enabling the production of a phase difference film with reduced orientation angle unevenness or phase difference unevenness. In addition, resin films with a low solvent content exhibit excellent orientation properties, allowing them to produce a large phase difference even at low stretching ratios.

[0069] The birefringence (ΔP(590)) in the thickness direction of the resin film at a measurement wavelength of 590 nm is, for example, greater than 0.0005, preferably 0.0007 or more, and more preferably 0.001 or more. The upper limit of ΔP(590) is, for example, 0.004 or less, preferably 0.0035 or less. Since a resin film having ΔP(590) within the above range can exhibit high in-plane birefringence upon stretching, a phase difference film with a desired in-plane phase difference and small thickness can be suitably obtained.

[0070] The in-plane birefringence (Δn(590)) of the resin film at a measurement wavelength of 590 nm is, for example, 0.0003 or less, and preferably 0 to 0.00005. A resin film having Δn(590) within the above range can exhibit stable in-plane orientation after stretching.

[0071] The resin film preferably exhibits reverse wavelength dispersion characteristics with respect to the retardation in the thickness direction. The resin film satisfies, for example, the relationship of Rth(450) / Rth(550) < 1.00, preferably satisfies the relationship of 0.60 < Rth(450) / Rth(550) < 0.98, and more preferably satisfies the relationship of 0.80 < Rth(450) / Rth(550) < 0.98. According to the resin film satisfying the above relationship, a retardation film that exhibits reverse wavelength dispersion characteristics with respect to the in-plane retardation can be suitably obtained.

[0072] The thickness of the resin film is, for example, 50 μm to 200 μm, preferably 70 μm to 180 μm, and more preferably 100 μm to 180 μm.

[0073] A-6. Stretching Subsequently, the long resin film obtained above is stretched. The stretching is performed using, for example, a tenter-type stretching device, a roll stretcher, etc. The tenter-type stretching device can stretch the film by gripping and conveying the widthwise ends of the long film with gripping tools that travel along the guide rails.

[0074] As described above, since the solvent content of the resin film is low, the generation of curl is suppressed until it is conveyed to the tenter stretching device after peeling. As a result, chucking failure is prevented, and the widthwise ends of the long resin film can be satisfactorily gripped by the gripping tools.

[0075] The stretching direction can be set arbitrarily according to the pattern of the guide rails, the running speed of the gripping tools, etc., and can be, for example, the longitudinal direction, the width direction, or the diagonal direction. In one embodiment, the stretching direction is the width direction.

[0076] The stretching ratio can be appropriately set according to the retardation desired for the retardation film. The stretching ratio is, for example, 8 times or less, preferably 2 times to 8 times, and more preferably 2.5 times to 7.5 times.

[0077] The thickness of the stretched resin film is, for example, 10 μm to 80 μm, preferably 10 μm to 70 μm, and more preferably 10 μm to 50 μm.

[0078] The stretching temperature can vary depending on the desired in-plane phase difference and thickness of the phase difference film, the type of resin used, the thickness of the resin film, the stretching ratio, etc. The stretching temperature fluctuates in relation to the Tg of the materials contained in the resin film, and is, for example, Tg1-20°C to Tg1+50°C, preferably Tg1-20°C to Tg1+40°C, and more preferably Tg1-10°C to Tg1+40°C, relative to the glass transition temperature (Tg1) of the resin with the lowest Tg among the oriented resins. If the stretching temperature is within this range, the film can be stretched stably.

[0079] The stretching speed is, for example, 1 mm / second or more, preferably 2 mm / second or more, and for example, 200 mm / second or less, preferably 100 mm / second or less.

[0080] The resin film is preferably preheated before stretching. The preheating temperature is set with respect to Tg1, similar to the stretching temperature. The preheating temperature is, for example, Tg1-20°C or higher, preferably Tg1-10°C or higher, and for example, Tg1+50°C or lower, preferably Tg1+40°C or lower. Typically, the preheating temperature is higher than the stretching temperature, preferably 5°C or higher than the stretching temperature.

[0081] If necessary, the process may include a step of heat-shrinking the stretched resin film in the stretching direction. The heat shrinkage temperature is set with respect to Tg1, similar to the preheating and stretching temperatures, and is, for example, Tg1-20°C or higher, preferably Tg1-15°C or higher, and for example, Tg1+45°C or lower, preferably Tg1+35°C or lower. The heat shrinkage temperature is more preferably below the stretching temperature. The shrinkage rate is typically 1% to 5%.

[0082] B. Phase difference film The retardation film produced by the method for producing a retardation film according to item A typically exhibits a refractive index characteristic showing a relationship of nx > ny ≧ nz. Here, "ny = nz" includes not only the case where ny and nz are exactly equal but also the case where they are substantially equal. Therefore, within a range that does not impair the effects of the present invention, ny < nz may occur.

[0083] The in-plane birefringence (Δn(590)) of the retardation film (in other words, the resin film after stretching) at a measurement wavelength of 590 nm typically exceeds 0.003, preferably exceeds 0.0035, more preferably is 0.0037 or more, and still more preferably is 0.0040 or more. The Δn(590) of the retardation film can be, for example, 0.007 or less.

[0084] The in-plane retardation of the retardation film can be any appropriate value according to the application and the like. In one embodiment, the retardation film can function as a λ / 4 plate. In this case, Re(550) of the retardation film is preferably 100 nm to 190 nm, more preferably 110 nm to 170 nm, and still more preferably 130 nm to 160 nm.

[0085] The Nz coefficient of the retardation film is preferably 0.9 to 3, more preferably 0.9 to 2.5, still more preferably 0.9 to 1.5, and particularly preferably 0.9 to 1.3. By satisfying such a relationship, when used in an image display device as a circular polarizing plate in combination with a polarizer, a very excellent reflected hue can be achieved.

[0086] The retardation film typically exhibits an inverse dispersion wavelength characteristic in which the in-plane retardation increases as the wavelength of the measurement light increases. The retardation film typically satisfies the relationship of Re(450) / Re(550) < 0.90, preferably satisfies the relationship of Re(450) / Re(550) < 0.88, and more preferably satisfies the relationship of 0.70 < Re(450) / Re(550) < 0.88. When a retardation film satisfying such a relationship is used in an image display device as a circular polarizing plate in combination with a polarizer, very excellent antireflection characteristics can be realized.

[0087] The thickness of the phase difference film is, for example, 10 μm to 80 μm, preferably 10 μm to 50 μm, and more preferably 10 μm to 30 μm. The phase difference film obtained by the manufacturing method of the embodiment of the present invention has high in-plane birefringence, and therefore can have a practically sufficient in-plane phase difference with a small thickness. [Examples]

[0088] The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight. (1) Thickness The measurement was performed using a dial gauge (PEACOCK Corporation, product name "DG-205 type pds-2"). (2) In-plane phase difference (Re(λ)) and phase difference in the thickness direction (Rth(λ)) The film to be measured was cut into sections 4 cm long and 4 cm wide to form the measurement samples. The in-plane phase difference or the phase difference in the thickness direction at a measurement wavelength of λ nm was measured for these samples using an Axometrics Axoscan device. The measurement temperature was 23°C. (3) In-plane birefringence (Δn(λ)) and birefringence in the thickness direction (ΔP(λ)) The in-plane phase difference at the measurement wavelength λnm of the sample measured in (2) above was divided by the thickness of the sample to calculate the in-plane birefringence at the measurement wavelength λnm. Similarly, the thickness-direction birefringence at the measurement wavelength λnm of the sample measured in (2) above was divided by the thickness of the sample to calculate the thickness-direction birefringence at the measurement wavelength λnm. (4) Glass transition temperature (Tg) Measurements were taken in accordance with JIS K 7121. (5) Solvent content • Solvent content of the primary resin layer After fabricating the laminate with the primary resin layer, it was left to stand for more than half a day in an environment of 22°C and 40% RH, and the primary resin layer was peeled off from the support substrate. The weight (A) of the primary resin layer was measured immediately after peeling. The primary resin layer was dried in a drying oven at 130°C for 2.5 hours, and then left to stand for more than half a day in an environment of 22°C and 40% RH, after which its weight (B) was measured. The solvent content was calculated using the following formula. Solvent content (weight %) = (weight (A) - weight (B)) / weight (A) × 100 • Solvent content of the secondary resin layer The solvent content of the secondary resin layer was determined in the same manner as the solvent content of the primary resin layer.

[0089] [Synthesis Example 1] Synthesis of cinnamic acid ester copolymer (9-vinylcarbazole / α-cyano-4-hydroxycinnamate isobutyl / acrylate isobutyl) 12.20 g of 9-vinylcarbazole, 7.74 g of isobutyl α-cyano-4-hydroxycinnamate, 4.05 g of isobutyl acrylate, and 0.453 g of 2,5-dimethyl-2,5-di(2-ethylhexanoylperoxy)hexane and 36.00 g of methyl ethyl ketone, which are polymerization initiators, were placed in a 50 mL glass ampoule. After repeated nitrogen purging and pressure release, the ampoule was sealed under reduced pressure. Radical polymerization was carried out by placing this ampoule in a 54°C constant temperature bath and maintaining it for 24 hours. After the polymerization reaction was complete, the polymer was removed from the ampoule, 100 g of tetrahydrofuran was added, and this polymer solution was added dropwise to 800 g of methanol / water mixed solvent (weight ratio 80 / 20) to precipitate. After filtration, the filtrate was washed five times with 110 g of methanol / water mixed solvent (weight ratio 90 / 10) and filtered again. The obtained resin was vacuum-dried at 80°C for 10 hours to yield 22.3 g of a cinnamic acid ester copolymer exhibiting negative birefringence. The number-average molecular weight of the obtained cinnamic acid ester copolymer was 50,000, and the ratio of residue units was 50 mol% 9-vinylcarbazole residue units, 25 mol% α-cyano-4-hydroxycinnamate isobutyl residue units, and 25 mol% isobutyl acrylate residue units.

[0090] [Example 1] 80g of ethylcellulose (Dow Chemical Company's "ETHOCEL standard 100," number average molecular weight Mn=58,000, weight average molecular weight Mw=180,000, Mw / Mn=3.2, degree of total substitution DS=2.51) as a cellulosic resin, 20g of cinnamic acid ester resin obtained in Synthesis Example 1 as an ester resin, and 0.1g of a hindered phenol antioxidant (BASF Japan, product name "Irganox 245") were dissolved in a toluene / ethyl acetate = 4 / 6 (weight ratio) solution to obtain a resin solution with a resin concentration of 16% by weight (solvent content: 84% by weight). This solution was poured onto a long polyethylene terephthalate (PET) film using a coater to obtain a long laminate with a coated layer having a [coated layer / PET film] structure. The thickness of the coated layer was 560 μm. The coated laminate was dried by passing it through an oven set to 65°C in chambers 1 to 6, 80°C in chamber 7, and 110°C in chambers 8 to 9 for 10 minutes, thereby obtaining a laminate with a primary resin layer having the structure of [primary resin layer / PET film] (heating time at each temperature is proportional to the number of chambers). The solvent content of the primary resin layer was 4.2% by weight, and the thickness of the primary resin layer was 112 μm. Next, the laminate with the primary resin layer was transported by roll to a winding device at room temperature (approximately 23°C), wound onto the roll, and stored at 23°C for 72 hours or more. The coating device, oven, and winding device were all located on the same transport line. Next, the laminate with the primary resin layer was unwound from the roll and passed through an oven set to 130°C for approximately 18 minutes to dry the primary resin layer and obtain a laminate with a secondary resin layer having the structure of [secondary resin layer / PET film]. The solvent content of the secondary resin layer was 1.4% by weight. The secondary resin layer was peeled off from the laminate with the secondary resin layer after passing through the oven to obtain a resin film 1. The resin film 1 was roll-transported to a tenter stretching machine, and the ends in the width direction were gripped with a gripping device. A phase difference film was obtained by uniaxial stretching to 3.0 times its original size at 157°C. The thickness of resin film 1 before stretching was 109 μm, ΔP(590) was 0.0021, and Rth(450) / Rth(550) was 0.93. The thickness of the stretched resin film 1 (phase difference film) was 35 μm, Δn(590) was 0.0042, and Re(450) / Re(550) was 0.866.

[0091] A sample was taken from the vicinity of the center in the thickness direction of the stretched resin film 1 (phase difference film) (specifically, a region within ±20% of the center in the thickness direction of the phase difference film when the thickness of the phase difference film is set to 100%). The cross-section of the phase difference film was observed using a TEM (HT7820, Hitachi Corporation) by an ultrathin sectioning method including heavy metal staining (cross-sectional TEM observation), and it was confirmed that a nanophase separation structure was formed in which the size (maximum length) of all domains was less than 100 nm.

[0092] [Example 2] Resin film 2 was obtained in the same manner as in Example 1, except that the thickness of the coating layer was 890 μm (the thickness of the obtained primary resin layer was 180 μm). The resin film 2 was roll-transported to a tenter stretcher, and the ends in the width direction were gripped with a gripping device. A phase difference film was obtained by uniaxial stretching to 2.8 times its original size at 162°C. The thickness of the resin film 2 before stretching was 170 μm, ΔP(590) was 0.00157, and Rth(450) / Rth(550) was 0.96. The thickness of the stretched resin film 2 (phase difference film) was 36 μm, Δn(590) was 0.0038, and Re(450) / Re(550) was 0.91.

[0093] [Comparative Example 1] The procedure was the same as in Example 1, except that the primary resin layer was peeled from the PET film to obtain resin film C1, and the resin film C1 was roll-transported to a tenter stretcher at room temperature without being wound up and subjected to transverse uniaxial stretching.

[0094] [Comparative Example 2] The procedure was the same as in Example 2, except that the primary resin layer was peeled from the PET film to obtain resin film C2, and the resin film C2 was roll-transported to a tenter stretcher at room temperature without being wound up and subjected to transverse uniaxial stretching.

[0095] Curl measurements and transportability evaluations were performed for the above examples and comparative examples. The results are shown in Table 1. <Curl measurement> In the examples and comparative examples, a 10cm x 10cm square was cut from the center of the widthwise portion of the resin film, and the resin layer side was placed facing upwards (in other words, the side that peeled off from the support substrate was facing downwards) and left to stand for half a day. After standing, the height of the curl at the four corners was measured with a ruler, and the average value was taken as the amount of curl (mm).

[0096] <Evaluation of transportability> The resin films obtained in the examples and comparative examples were fixed with tape just before chucking by the clips of the tenter stretcher and left to stand for more than two hours. After that, film transport and chucking were started, and it was evaluated whether the film could be transported for more than 50m without breaking. ○: It was possible to transport it. ×: The clip came loose midway through the process, causing the resin film to break inside the tenter stretcher's oven.

[0097] [Table 1]

[0098] As shown in Table 1, in the resin film obtained by peeling off the secondary resin layer, in which the amount of residual solvent has been sufficiently reduced, curling at the edges was suppressed, and as a result, chucking problems when being taken up by the tenter stretching device were improved. [Industrial applicability]

[0099] The phase difference film obtained by the manufacturing method of the present invention can be suitably used in image display devices such as liquid crystal displays and EL displays, and in particular in organic EL displays.

Claims

1. A resin solution containing resin and solvent is applied to a long support substrate to produce a laminate with a coated layer having the support substrate and a coated layer provided on one side thereof. The coated layer is heated and dried at 70°C to 140°C to produce a laminate with a primary resin layer having the support substrate and a primary resin layer having solvent content A provided on one side thereof. The primary resin layer is cooled to 50°C or below. The primary resin layer is heated and dried to produce a laminate with a secondary resin layer having the support substrate and a secondary resin layer having solvent content B provided on one side thereof. The secondary resin layer is peeled off the support substrate to obtain a long resin film, and Stretching the elongated resin film, Includes, A method for producing a phase difference film, wherein the solvent content B is 0% to 3% by weight.

2. The method for manufacturing a phase difference film according to claim 1, wherein the thickness of the phase difference film is 10 μm or more.

3. The method for manufacturing a phase difference film according to claim 1 or 2, wherein the resin is a thermoplastic resin.

4. A method for manufacturing a phase difference film according to claim 1 or 2, wherein the birefringence ΔP(590) in the thickness direction of the resin film before stretching at a measurement wavelength of 590 nm is greater than 0.0005.

5. A method for manufacturing a phase difference film according to claim 1 or 2, wherein the ratio of the phase difference in the thickness direction of the resin film before stretching at a measurement wavelength of 450 nm to the phase difference in the thickness direction at a measurement wavelength of 550 nm (Rth(450) / Rth(550)) is less than 1.

00.

6. The aforementioned resin film comprises a cellulose resin and an ester resin. A method for manufacturing a phase difference film according to claim 1 or 2, wherein a nanophase separation structure is formed in the phase difference film.

7. The cellulose-based resin has the constituent units shown in the following formula (1), The method for manufacturing a phase difference film according to claim 6, wherein the ester resin comprises a structural unit shown in the following formula (2) and a structural unit shown in the following formula (3): 【Chemistry 1】 (In formula (1), R １ ~R ３ Each of these represents a hydrogen atom or a substituent having 1 to 12 carbon atoms;) 【Chemistry 2】 (In formula (2), R ４ R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; ５ａ R represents one selected from an alkyl group having 1 to 12 carbon atoms, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, or a thiol group; R ５ｂ R represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms; ６ This indicates a species selected from a hydrogen atom, a nitro group, a bromo group, an iodo group, a cyano group, a chloro group, a sulfonic acid group, a carboxylic acid group, a fluoro group, a phenyl group, a thiol group, an amide group, an amino group, a hydroxyl group, an alkoxy group having 1 to 12 carbon atoms, or an alkyl group having 1 to 12 carbon atoms. 【Transformation 3】 (In formula (3), R ７ This represents a five-membered heterocyclic residue or a six-membered heterocyclic residue containing one or more nitrogen or oxygen atoms as heteroatoms (the five-membered heterocyclic residue and the six-membered heterocyclic residue may form a fused ring structure with other cyclic structures).

8. The ester resin further comprises the constituent units shown in the following formula (4), wherein the method for manufacturing a phase difference film according to claim 7: 【Chemistry 4】 (In formula (4), each of R ８ and R ９ represents one selected from a hydrogen atom, a linear alkyl group having 1 to 12 carbon atoms, a branched alkyl group having 3 to 12 carbon atoms, or a cyclic alkyl group having 3 to 6 carbon atoms).

9. A method for manufacturing a phase difference film according to claim 1 or 2, wherein the solvent content B of the secondary resin layer is 50% or less of the solvent content A of the primary resin layer.

10. A method for manufacturing a phase difference film according to claim 1 or 2, comprising winding the laminate with the primary resin layer onto a roll, then unwinding it from the roll and subjecting the primary resin layer to the heat drying process.

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