Method for manufacturing resin films and processed films

Abstract

The present invention addresses the problem of providing a resin film that can suppress the formation of cracks extending in a direction orthogonal to the thickness direction during the shaping process. The solution is that the resin film of the embodiment of the present invention has a shear strength of 2.5 N or higher.

Description

Technical Field

[0001] This invention relates to resin films and methods for manufacturing processed films. Prior Technology

[0002] Resin films are widely used in various industrial products, and are generally processed into shapes suitable for their intended use. For example, some literature proposes to process acrylic resin films into desired shapes (see, for example, Patent Document 1). However, if the acrylic resin film described in Patent Document 1 is processed to change its shape, cracks extending in a direction orthogonal to the thickness direction may occur on the end face of the acrylic resin film. Previous technical documents Patent documents

[0003] Patent Document 1: Japanese Patent Application Publication No. 2008-213401 Summary of the Invention

[0004] The problem the invention aims to solve The present invention was made to solve the above-mentioned problems, and its main objective is to provide a resin film that can suppress the generation of cracks extending in a direction orthogonal to the thickness direction during the shape processing.

[0005] The means to solve the problem [1] The shear breaking strength of the resin film in one embodiment of the present invention is 2.5 N or more. [2] The resin film described in [1] above can also be made of polycarbonate resin. [3] Another aspect of the present invention is to process the shape of the resin film as described in [1] or [2] above.

[0006] Invention Effects According to an embodiment of the present invention, a resin film that can suppress the formation of cracks extending in a direction orthogonal to the thickness direction during shape processing can be realized. Simple Explanation of the Diagram

[0007] Figure 1 is a schematic cross-sectional view of a resin film according to an embodiment of the present invention. Figure 2 is a schematic cross-sectional view of one embodiment of a polarizing plate having the resin film of Figure 1. Figure 3 is a schematic cross-sectional view of another embodiment of the polarizing plate having the resin film of Figure 1. Figure 4 is a schematic top view of the processed film made from the resin film in Figure 1. Implementation

[0008] The following describes representative embodiments of the present invention, but the present invention is not limited to these embodiments. Furthermore, for the purpose of more clearly illustrating the drawings, the width, thickness, shape, etc., of each part are schematically shown compared to the embodiments, but this is only an example and is not intended to limit the interpretation of the present invention.

[0009] (Definitions of terms and symbols) The terms and symbols used in this manual are defined as follows. (1) Refractive index (nx, ny, nz) "nx" is the refractive index in the direction where the in-plane refractive index reaches its maximum (i.e., the slow axis direction), "ny" is the refractive index in the direction orthogonal to the slow axis (i.e., the fast axis direction), and "nz" is the refractive index in the thickness direction. (2) In-plane phase difference (Re) "Re(λ)" is the in-plane phase difference measured at 23°C using light with a wavelength of λnm. For example, "Re(550)" is the in-plane phase difference measured at 23°C using light with a wavelength of 550nm. Re(λ) can be obtained by the formula: Re(λ) = (nx-ny) ×d when the thickness of the layer (thin film) is d (nm). (3) Phase difference (Rth) in the thickness direction "Rth(λ)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of λnm. For example, "Rth(550)" is the phase difference in the thickness direction measured at 23°C using light with a wavelength of 550nm. Rth(λ) can be obtained by the formula: Rth(λ) = (nx-nz) ×d when the thickness of the layer (thin film) is d (nm).

[0010] A. Overall composition of the resin film Figure 1 is a schematic cross-sectional view of a resin film according to an embodiment of the present invention. As shown in Figure 1, the shear breaking strength (the force required to cut and break the sample) of the resin film 1 is 2.5 N or higher. If the shear breaking strength of the resin film is 2.5 N or higher, then even if the resin film is subjected to the shaping process described later, it is still possible to suppress the generation of cracks on the end face of the shaped resin film (processed film) that extend in a direction orthogonal to the thickness direction (lateral direction).

[0011] The shear strength of the resin film 1 should preferably be 3.0 N or more, and more preferably 3.5 N or more. On the other hand, the shear strength of the resin film 1 should, for example, be 7.0 N or less, preferably 6.0 N or less, and more preferably 5.0 N or less. Furthermore, the shear strength is measured, for example, using the JIS surface-interface cutting method (SAICAS method). If the shear strength of the resin film is within the above range, cracks extending in a direction orthogonal to the thickness direction (surface direction, transverse direction) at the end face of the resin film (processed film) after shaping can be suppressed. Moreover, if the shear strength of the resin film is below the above upper limit, the resin film can be processed smoothly.

[0012] The tensile impact strength of the resin film 1 is, for example, 300 kJ / m² or higher, preferably 400 kJ / m² or higher. On the other hand, the tensile impact strength of the resin film 1 is, for example, 700 kJ / m² or lower, preferably 600 kJ / m² or lower, and more preferably 500 kJ / m² or lower. Furthermore, the tensile impact strength is measured according to JIS K 7160, for example. If the tensile impact strength of the resin film is within the above range, cracks extending in the thickness direction (longitudinal direction) can be suppressed at the end face of the resin film (processed film) after shaping.

[0013] The thickness of the resin film 1 is, for example, 10µm or more, preferably 30µm or more, and more preferably 40µm or more. On the other hand, the thickness of the resin film 1 is, for example, 130µm or less, preferably 100µm or less, and more preferably 80µm or less. If the thickness of the resin film is within the above range, crack formation can be stably suppressed during the shaping process.

[0014] The following details the resin film.

[0015] B. Resin film The resin film 1 comprises any suitable resin material as its main component. Specific examples of such resin material include: polyvinyl chloride... Transparent resins include cyclic olefin (COP) resins such as olefins; polyester resins such as polyethylene terephthalate (PET) resins; cellulose resins such as cellulose triacetate (TAC) resins; polycarbonate (PC) resins; (meth)acrylic resins; polyvinyl alcohol resins; polyamide resins; polyimide resins; polyether resins; polyurethane resins; polystyrene resins; polyolefin resins; and acetate resins. Also, thermosetting or UV-curing resins such as (meth)acrylic resins, carbamate resins, (meth)acrylate carbamate resins, epoxy resins, and polysiloxane resins can be used. Furthermore, "(meth)acrylic resin" refers to acrylic resins and / or methacrylic resins. Other examples include glassy polymers such as silicate polymers. Also, polymer films described in Japanese Patent Application Publication No. 2001-343529 (WO01 / 37007) can be used. As a material for this film, for example, a resin composition can be used containing a thermoplastic resin with substituted or unsubstituted amide groups on the side chains, and a thermoplastic resin with substituted or unsubstituted phenyl and nitrile groups on the side chains. Examples include resin compositions comprising an alternating copolymer of isobutylene and N-methylmaleimide and an acrylonitrile-styrene copolymer. The polymer film can be, for example, an extruded product of the aforementioned resin composition. The resin film material can be used alone or in combination.

[0016] Among the resin materials mentioned, PC-based resins are particularly suitable.

[0017] PC-based resins contain at least a constituent unit derived from a dihydroxy compound having the bonding structure shown in the following structural formula (1), and are manufactured by reacting a dihydroxy compound, which contains at least one dihydroxy compound having at least one intramolecular bonding structure -CH2-O-, with a diester in the presence of a polymerization catalyst. In other words, PC-based resins contain a structural unit derived from a dihydroxy compound and a carbonate group derived from a diester. [Chemical Formula 1]

[0018] Here, as a dihydroxy compound having the bonding structure shown in structural formula (1), if it is a compound containing two alcoholic hydroxyl groups and having a linker group -CH2-O- in the molecule, and can react with diester carbonate in the presence of a polymerization catalyst to generate polycarbonate, then any compound with any structure can be used, and multiple compounds can be used together.

[0019] Furthermore, it is permissible to use dihydroxy compounds that do not have the bonding structure shown in the above structural formula (1) as dihydroxy compounds for PC resins. Hereinafter, dihydroxy compounds having the bonding structure shown in structural formula (1) will sometimes be referred to as dihydroxy compounds (A), and dihydroxy compounds that do not have the bonding structure shown in structural formula (1) will sometimes be referred to as dihydroxy compounds (B).

[0020] (Dihydroxy compound (A)) In dihydroxy compound (A), the "linking group -CH2-O-" refers to the molecular structure formed by bonding with atoms other than hydrogen atoms. In this linking group, at least one atom that can bond with an oxygen atom, or a carbon atom that can bond with both an oxygen atom, should preferably be a carbon atom. The number of "linking groups -CH2-O-" in dihydroxy compound (A) should preferably be 1 or more, more preferably 2 to 4.

[0021] Dihydroxy compounds (A) can be specifically listed as follows: 9,9-bis(4-(2-hydroxyethoxy)phenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-methylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-isopropylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-isobutylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-trimethylbutylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-cyclohexylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3-phenylphenyl) piracetam, 9,9-bis(4-(2-hydroxyethoxy)-3,5-dimethyl ... Compounds exemplified by (4-(2-hydroxyethoxy)-3-tert-butyl-6-methylphenyl) monazine, 9,9-bis(4-(3-hydroxy-2,2-dimethylpropoxy)phenyl) monazine, having an aromatic group in the side chain and an ether group bonded to the aromatic group in the main chain; bis[4-(2-hydroxyethoxy)phenyl]methane, bis[4-(2-hydroxyethoxy)phenyl]diphenylmethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]ethane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-1-phenylethane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)-3-methylphenyl]propane, 2,2-bis[ 3,5-Dimethyl-4-(2-hydroxyethoxy)phenyl]propane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]-3,3,5-trimethylcyclohexane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,4-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,3-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 2,2-bis[4-(2-hydroxyethoxy)-3-phenylphenyl]propane, 2,2-bis[(2-hydroxyethoxy)-3-isopropylphenyl]propane, 2,2-bis[3-tert-butyl-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]butane, 2, 2-bis[4-(2-hydroxyethoxy)phenyl]-4-methylpentane, 2,2-bis[4-(2-hydroxyethoxy)phenyl]octane, 1,1-bis[4-(2-hydroxyethoxy)phenyl]decane, 2,2-bis[3-bromo-4-(2-hydroxyethoxy)phenyl]propane, 2,2-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]propane and bis(hydroxyalkoxyaryl)alkanes; 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane, 1,1-bis[3-cyclohexyl-4-(2-hydroxyethoxy)phenyl]cyclohexane and 1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclopentane and bis(hydroxyalkoxyaryl)cycloalkanes;Dihydroxyalkoxy diaryl ethers exemplified by 4,4'-bis(2-hydroxyethoxy)diphenyl ether and 4,4'-bis(2-hydroxyethoxy)-3,3'-dimethyldiphenyl ether; dihydroxyalkoxy aryl sulfides exemplified by 4,4'-bis(2-hydroxyethoxyphenyl)sulfide and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]sulfide; dihydroxyalkoxy aryl sulfides exemplified by 4,4'-bis(2-hydroxyethoxyphenyl)ene and 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]ene; 4,4'-bis(2-hydroxyethoxyphenyl)ene, 4,4'-bis[4-(2-dihydroxyethoxy)-3-methylphenyl]ene -Dihydroxyalkoxyaryl compounds exemplified by bis[4-(2-dihydroxyethoxy)-3-methylphenyl] benzox; dihydroxyalkoxybenzenes exemplified by 1,4-dihydroxyethoxybenzene; 1,3-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 1,4-bis[2-[4-(2-hydroxyethoxy)phenyl]propyl]benzene; 4,4'-bis(2-hydroxyethoxy)biphenyl; 1,3-bis[4-(2-hydroxyethoxy)phenyl]-5,7-dimethylaluminothane; sugar anhydrides exemplified by dihydroxy compounds of formula (2) below; and compounds having a cyclic ether structure exemplified by spiroglycerol of general formula (3) below. Dihydroxy compound (A) can be used alone or in combination.

[0022] [Chemical Formula 2]

[0023] [Chemical Formula 3]

[0024] Among these dihydroxy compounds (A), the dihydroxy compound shown in formula (2) above is also suitable. Examples of dihydroxy compounds shown in formula (2) above include isosorbide, dehydromannitol, and isotretinoin, which are stereoisomers. One of these compounds may be used alone or in combination of two or more. Furthermore, among dihydroxy compounds (A), isosorbide, which is obtained by dehydration condensation of sorbitol produced from various starches that are abundant in resources and readily available, is the best in terms of ease of acquisition and manufacture, optical properties, and formability.

[0025] Compared to the structural units derived from all dihydroxy compounds in PC-based resins, the proportion of structural units derived from dihydroxy compound (A) is, for example, 10 mol% or more, preferably 40 mol% or more, and more preferably 60 mol% or more. On the other hand, the proportion of structural units derived from dihydroxy compound (A) is, for example, 100 mol% or less, preferably 90 mol% or less, more preferably 80 mol% or less, and more preferably 70 mol% or less. If the proportion of dihydroxy compound (A) is within the above range, the shear strength of the resin film can be stably adjusted within the above range.

[0026] (Dihydroxy compound (B)) The dihydroxy compound that forms the structural unit of the PC resin can be used together with dihydroxy compound (A) and dihydroxy compound (B). If dihydroxy compounds (A) and (B) are used together, the shear failure strength of the resin film can be more stably adjusted within the above-mentioned range.

[0027] Dihydroxy compound (B) represents any dihydroxy compound other than dihydroxy compound (A). Examples of dihydroxy compound (B) include alicyclic dihydroxy compounds, aliphatic dihydroxy compounds, oxoalkyl diols, aromatic dihydroxy compounds, and diols with cyclic ether structures. Dihydroxy compound (B) can be used alone or in combination. Among dihydroxy compounds (B), alicyclic dihydroxy compounds are preferred.

[0028] Alicyclic dihydroxy compounds are not particularly limited, but compounds that typically contain a 5-membered or 6-membered ring structure are acceptable. Furthermore, the 6-membered ring structure can be covalently fixed into a chair or boat shape. By using a 5- or 6-membered ring structure in the alicyclic dihydroxy compound, the heat resistance of the resulting PC resin can be improved. The number of carbon atoms in the alicyclic dihydroxy compound should be, for example, 70 or less, preferably 50 or less, and more preferably 30 or less.

[0029] Alicyclic dihydroxy compounds containing a 5-membered ring structure or a 6-membered ring structure can be specifically exemplified by the alicyclic dihydroxy compounds shown in general formula (I) or (II) below. HOCH2-R1-CH2OH (I) HO-R2-OH (II) (In formulas (I) and (II), R1 and R2 each represent cycloalkyl groups with 4 to 20 carbon atoms).

[0030] Cyclohexanediethanol, belonging to the alicyclic dihydroxy compounds shown in general formula (I) above, includes various isomers of general formula (I) where R1 is represented by the following general formula (Ia) (where R3 represents an alkyl group with 1 to 12 carbon atoms or a hydrogen atom). Specific examples of such isomers include 1,2-cyclohexanediethanol, 1,3-cyclohexanediethanol, and 1,4-cyclohexanediethanol.

[0031] [Chemical Formula 4]

[0032] Tricyclic decanediethanol or pentacyclic pentadecanediethanol, belonging to the alicyclic dihydroxy compounds shown in the above general formula (I), includes various isomers of general formula (I) represented by the following general formula (Ib) (where n represents 0 or 1).

[0033] [Chemical Formula 5]

[0034] The decahydronaphthyldiethanol or tricyclotetradecanediethanol belonging to the alicyclic dihydroxy compounds shown in general formula (I) above includes various isomers of general formula (I) represented by the following general formula (Ic) (where m represents 0 or 1). Specific examples of such isomers include 2,6-decahydronaphthyldiethanol, 1,5-decahydronaphthyldiethanol, and 2,3-decahydronaphthyldiethanol.

[0035] [Chemical Formula 6]

[0036] Norbornenediethanol, belonging to the alicyclic dihydroxy compounds of general formula (I) above, includes various isomers of general formula (I) represented by the following general formula (Id). Specific examples of such isomers include 2,3-norbornenediethanol and 2,5-norbornenediethanol.

[0037] [Chemical Formula 7]

[0038] Adamantanediethanol, alicyclic dihydroxy compound of general formula (I), includes various isomers of general formula (I) where R1 is represented by the following general formula (Ie). Specific examples of such isomers include 1,3-adamantanediethanol.

[0039] [Chemical Formula 8]

[0040] The cyclohexanediol of the alicyclic dihydroxy compound shown in general formula (II) above includes various isomers of general formula (IIa) in which R2 is represented by the following general formula (IIa) (where R3 represents an alkyl group with 1 to 12 carbon atoms or a hydrogen atom). Specific examples of such isomers include 1,2-cyclohexanediol, 1,3-cyclohexanediol, 1,4-cyclohexanediol, and 2-methyl-1,4-cyclohexanediol.

[0041] [Chemical Formula 9]

[0042] Tricyclic decanediol or pentacyclic pentadecanediol, belonging to the alicyclic dihydroxy compounds shown in general formula (II) above, includes various isomers of general formula (II) in which R2 is represented by the following general formula (IIb) (where n represents 0 or 1).

[0043] [Chemical Formula 10]

[0044] The decahydronaphthyldiol or tricyclic tetradecanediol belonging to the alicyclic dihydroxy compounds shown in general formula (II) above includes various isomers of general formula (II) in which R2 is represented by the following general formula (IIc) (where m represents 0 or 1). Specific examples of such isomers include 2,6-decahydronaphthyldiol, 1,5-decahydronaphthyldiol, and 2,3-decahydronaphthyldiol.

[0045] [Chemical Formula 11]

[0046] Norbornene diols belonging to the alicyclic dihydroxy compounds shown in general formula (II) above include various isomers of general formula (II) represented by general formula (IId). Specific examples of such isomers include 2,3-norbornene diol and 2,5-norbornene diol.

[0047] [Chemical Formula 12]

[0048] Adamantanediols belonging to the alicyclic dihydroxy compounds shown in general formula (II) above include various isomers of general formula (II) where R2 is represented by the following general formula (IIe). Specific examples of such isomers include 1,3-adamantanediol.

[0049] [Chemical Formula 13]

[0050] Among the specific examples of the aforementioned alicyclic dihydroxy compounds, cyclohexanediethanol, tricyclodecanediethanol, adamantanediol, and pentacyclopentadecanedimethanol are also suitable examples. From the perspective of availability and ease of disposal, 1,4-cyclohexanediethanol, 1,3-cyclohexanediethanol, 1,2-cyclohexanediethanol, and tricyclodecanediethanol are more suitable examples, with tricyclodecanediethanol being the most suitable.

[0051] Compared to the structural units derived from all dihydroxy compounds contained in PC resins, the proportion of structural units derived from dihydroxy compounds (B) is, for example, 0 mol% or more, preferably 10 mol% or more, more preferably 20 mol% or more, and even more preferably 30 mol% or more. On the other hand, the proportion of structural units derived from dihydroxy compounds (B) is, for example, 90 mol% or less, preferably 60 mol% or less, and more preferably 40 mol% or less.

[0052] Details of these PC-based resins are described, for example, in Japanese Patent Application Publication No. 2012-31370 (Japanese Patent No. 5448264). This specification incorporates the description in that patent document by way of reference.

[0053] In one embodiment, the PC-based resin comprises: a structural unit derived from the dihydroxy compound (A) shown in formula (2) above, a structural unit derived from the alicyclic dihydroxy compound (B) shown in general formula (I) above, and carbonate groups linking them. When the PC-based resin comprising these structural units is applied to a resin film, the shear failure strength of the resin film can be more stably adjusted within the aforementioned range. In the PC-based resin, the molar ratio (A:B) of the structural unit derived from the dihydroxy compound (A) shown in formula (2) and the structural unit derived from the alicyclic dihydroxy compound (B) shown in general formula (I) is, for example, 5:5 to 9:1, preferably 6:4 to 8:2. In the PC resin, the combination of the dihydroxy compound (A) shown in formula (2) and the alicyclic dihydroxy compound (B) shown in general formula (I) is preferably a combination of isosorbide and tricyclodecanediethanol.

[0054] In addition to the resin material described above, the resin film 1 may also contain any suitable additives. Examples of additives include antioxidants, ultraviolet absorbers, light stabilizers, nucleating agents, fillers, pigments, surfactants, and antistatic agents. Any suitable surface treatment layer may also be provided on the surface of the resin film 1. Examples of surface treatment layers include hard coatings, easy-adhesion layers, easy-slip layers, anti-adhesion layers, antistatic layers, anti-reflective layers, and anti-oligomery layers.

[0055] The resin film 1 represents optically isotropic. In this specification, "optically isotropic" means that the in-plane phase difference Re (550) and the phase difference Rth (550) in the thickness direction are within the following ranges. The in-plane phase difference Re(550) of the resin film 1 is, for example, less than 10 nm, preferably less than 5 nm, and more preferably less than 3 nm. On the other hand, the lower limit of the in-plane phase difference Re(550) of the resin film 1 represents 0 nm. The phase difference Rth(550) in the thickness direction of the resin film 1 is, for example, -10nm to +10nm, and preferably -5nm to 5nm.

[0056] The total light transmittance of the resin film 1 is, for example, 80% or more, preferably 85% or more, more preferably 90% or more, and even more preferably 95% or more. The haze value of the resin film 1 is, for example, 2.0% or less, preferably 1.5% or less, more preferably 1.0% or less, even more preferably 0.7% or less, particularly preferably 0.5% or less, and especially preferably 0.3% or less. The lower limit of the haze value of the resin film 1 represents 0.05%. If the total light transmittance and / or haze value of the resin film are within the specified range, the resin film can be used for optical applications.

[0057] C. Applications of Resin Films The resin films described in items A and B above can be applied to various industrial products. Examples of industrial products include optical components such as polarizing plates, decorative films, and protective films for finished products. The aforementioned resin film is particularly suitable for use in polarizing plates and decorative films.

[0058] C-1. Decorative film Although not illustrated, in one embodiment, the resin film 1 is applied to a decorative film. More specifically, the resin film 1 may be used as a substrate for the decorative film. The decorative film comprises: a resin film 1 as a substrate; an adhesive layer disposed on one side of the resin film 1; and a printing layer disposed on the surface of the adhesive layer opposite to the substrate. The decorative film is attached to the surface of the substrate in such a way that the printed layer comes into contact with the substrate. Then, the decorative film is heated as needed and peeled off from the surface of the substrate. In this way, the printed layer is transferred to the surface of the substrate, thus giving the substrate the desired design.

[0059] C-2. Polarizing plate Furthermore, as shown in Figures 2 and 3, the resin film 1 can also be applied to the polarizing plate 100. More specifically, the resin film 1 can be used as a protective layer for the polarizing element 2. The polarizing plate 100 includes the polarizing element 2 and the resin film 1 as a protective layer. The resin film 1 is disposed on at least one side of the polarizing element 2. The resin film 1 is attached to the polarizing element 2 through any suitable adhesive layer (adhesive layer or mordant layer). As shown in Figure 3, the resin film 1 as a protective layer can also be provided on both sides of the polarizing element 2.

[0060] C-2-1. Polarizing element The polarizer 2 can be any suitable polarizer. For example, the resin film forming the polarizer can be composed of a single layer of resin film, or it can be modulated using two or more layers of laminate.

[0061] Specific examples of polarizing elements composed of single-layer resin films include: those made by dyeing and stretching hydrophilic polymer films such as polyvinyl alcohol (PVA) films, partially formalized PVA films, and partially saponified ethylene-vinyl acetate copolymer films using dichroic substances such as iodine or dichroic dyes; and polyene-based oriented films such as dehydrated PVA products or dehydrochlorinated polyvinyl chloride products. From the perspective of superior optical properties, polarizing elements obtained by dyeing PVA films with iodine and then uniaxially stretching them are preferable.

[0062] Specific examples of polarizing elements obtained using a laminate include: a laminate consisting of a resin substrate and a PVA-based resin layer (PVA-based resin film) laminated on the resin substrate, or a laminate consisting of a resin substrate and a PVA-based resin layer coated on the resin substrate. A polarizing element obtained using a laminate consisting of a resin substrate and a PVA-based resin layer coated on the resin substrate can be manufactured, for example, by the following steps: coating a PVA-based resin solution onto a resin substrate and drying it to form a PVA-based resin layer on the resin substrate, thereby obtaining a laminate of the resin substrate and the PVA-based resin layer; and extending and dyeing the laminate to form a polarizing element from the PVA-based resin layer. In one embodiment of the invention, it is preferable to form a polyvinyl alcohol-based resin layer containing a halide and a polyvinyl alcohol-based resin on one side of the resin substrate. Extending typically includes extending the laminate by immersing it in an aqueous boric acid solution. Furthermore, depending on the requirements, the stretching can be further included by air-stretching the laminate at a high temperature (e.g., above 95°C) before stretching in a boric acid aqueous solution. In another embodiment of the invention, the laminate is preferably subjected to a drying shrinkage treatment, which involves heating the laminate while conveying it along its long side, thereby shrinking it by more than 2% in the width direction. For example, the manufacturing method of this embodiment includes sequentially performing air-assisted stretching, dyeing, underwater stretching, and drying shrinkage treatments on the laminate. By introducing assisted stretching, even when PVA is coated onto a thermoplastic resin, the crystallinity of PVA can be improved, achieving high optical properties. Furthermore, by simultaneously improving the orientation of PVA beforehand, problems such as reduced orientation or dissolution of PVA can be prevented when immersed in water during subsequent dyeing or stretching steps, thus achieving high optical properties. Furthermore, when the PVA-based resin layer is immersed in a liquid, the orientation disorder of polyvinyl alcohol molecules and the reduction of orientation are suppressed more effectively compared to the case where the PVA-based resin layer does not contain halides. Therefore, the optical properties of the polarizing element obtained by immersing the laminate in a liquid through dyeing and water-stretching processes can be improved. Furthermore, the optical properties can be further improved by shrinking the laminate in the width direction through a drying shrinkage process. The resulting resin substrate / polarizing element laminate can be used directly (i.e., the resin substrate can also be used as a protective layer for the polarizing element), or the resin substrate can be peeled off from the resin substrate / polarizing element laminate and then used after applying any suitable protective layer with the desired surface area. Detailed descriptions of the manufacturing method of the polarizing element are provided, for example, in Japanese Patent Application Publication No. 2012-73580 and Japanese Patent No. 6470455. The entire contents of these publications are incorporated herein by reference.

[0063] The aforementioned dyeing using iodine can be performed, for example, by immersing the PVA-based film in an aqueous iodine solution. The uniaxial stretching ratio is preferably 3 to 7 times. Stretching can be performed after dyeing or during dyeing. Alternatively, it can be performed after stretching and then dyeing. Depending on the needs, the PVA-based film may undergo swelling, cross-linking, washing, or drying treatments. For example, immersing the PVA-based film in water before dyeing can not only remove dirt or anti-adhesive agents from the surface of the PVA-based film but also cause the film to swell, preventing uneven dyeing.

[0064] The thickness of the polarizing element 2 is, for example, 1µm to 80µm, preferably 1µm to 15µm, more preferably 1µm to 12µm, and even more preferably 3µm to 12µm. If the thickness of the polarizing element is within the above range, curling during heating can be well suppressed, and good appearance durability during heating can be obtained.

[0065] Polarizing element 2 represents the system exhibiting absorption dichroism at any wavelength from 380 nm to 780 nm. The transmittance of a single element of polarizing element 2 is, for example, 41.5% to 46.0%, preferably 43.0% to 46.0%, and more preferably 44.5% to 46.0%. The polarization degree of polarizing element 2 is preferably 97.0% or higher, more preferably 99.0% or higher, and even more preferably 99.9% or higher.

[0066] D. External shaping In one embodiment, the resin film described in items A and B above, or the article containing the resin film described in item C above, is shaped into a desired shape. In this way, a processed film 3 (or an article containing the processed film 3) having the desired external shape is manufactured.

[0067] The external shape can be machined using any suitable method. Examples of external shape machining include blanking using a punch, cutting using a rotary axis, and laser machining. Among these external shape machining methods, laser machining is particularly suitable. Various conditions during the shape processing can be adjusted arbitrarily and appropriately.

[0068] There are no particular restrictions on the external shape of the processed film 3 (or the article containing the processed film 3). Such shapes may include, for example, rectangles and irregular shapes other than rectangles. Irregular shapes may include, for example, polygons other than quadrilaterals, circles, ellipses, and shapes with irregularly shaped processing parts.

[0069] As shown in Figure 4, in one embodiment, the processed film 3 (or an article containing the processed film 3) has a shaped processing portion 31. The shaped processing portion 31 may be, for example, a recess that extends inward from the outer edge of the processed film 3, or a through hole that penetrates the processed film 3. In the example shown, the processed film 3 has a recess 31a as a shaped processing part. The shape of the recess is not particularly limited, and examples include V-shape and U-shape.

[0070] Compared to processing a resin film (or an article containing a resin film) into a rectangular shape, processing a resin film (or an article containing a resin film) into an irregular shape makes it easier for cracks extending in a direction orthogonal to the thickness direction to form on the end face of the resin film. On the other hand, in one embodiment, the shear strength of the resin film is 2.5 N or more, so even if the resin film (or an article containing a resin film) is processed into an irregular shape as described above, the formation of cracks extending in a direction orthogonal to the thickness direction on the end face of the processed film can still be stably suppressed.

[0071] Example The present invention will now be specifically described by way of examples, but the present invention is not limited to these examples. Furthermore, the methods for measuring each characteristic are as described below.

[0072] (1) Determination of shear strength of resin film The shear strength of the resin films obtained in the examples and comparative examples was determined using the surface-interface cutting method (SAICAS method). The results are shown in Table 1. More specifically, a resin film was cut into approximately 2 cm square pieces to prepare a sample. Next, using a SAICAS DN-20 cutter (manufactured by DAIPLA WINTES CO., LTD.), the sample was cut at a horizontal speed of 5 µm / min and a vertical speed of 0.5 µm / min. The parallel load FH [kN] and vertical displacement d [m] when the sample was cut at an angle were measured. The cutter width was 1 mm, the cutter angle was 10°, and the cutter was made of single-crystal diamond. Then, the shear failure strength τ was calculated from the parallel load FH [kN], the cutter width W [m], and the vertical displacement d [m] according to the following formula. τ[N] =FH[kN] / (2×Wd[m2] ×cotφ)

[0073] (2) Are there any cracks in the resin film during irregular shape processing? The resin films obtained in the examples and comparative examples were shaped using CO2 laser processing to obtain processed films with recesses serving as irregularly shaped processing portions. Then, it was checked whether the end faces of the processed films had cracks extending in a direction orthogonal to the thickness direction (lateral). The results are shown in Table 1.

[0074] [Example 1] Relative to 81.98 parts by mass of isosorbide (ISB), 47.19 parts by mass of tricyclodecanediethanol (TCDDM), 175.1 parts by mass of diphenyl carbonate (DPC), and 0.979 parts by mass of a 0.2% by mass aqueous solution of cesium carbonate as a catalyst were added to a reaction vessel. In the first stage of the reaction, under nitrogen atmosphere, the heating tank temperature was raised to 150°C, and the reactants were stirred to dissolve as needed (approximately 15 minutes). Next, the pressure was changed from atmospheric pressure to 13.3 kPa, and the heating tank temperature was raised to 190°C over 1 hour, while the generated phenol was discharged from the reaction vessel. After maintaining the entire reaction vessel at 190°C for 15 minutes, in the second stage, the pressure inside the reaction vessel was set to 6.67 kPa, and the heating tank temperature was raised to 230°C over 15 minutes, with the generated phenol being discharged from the reaction vessel again. Since the stirring torque of the agitator increases over time, the pressure inside the reaction vessel was lowered to below 0.200 kPa in order to raise the temperature to 250°C within 8 minutes and remove the generated phenol. After reaching the predetermined stirring torque, the reaction was stopped, and the resulting reactants were extruded into water to obtain PC resin pellets. The obtained PC resin was vacuum dried at 100°C for 12 hours, and then a film forming apparatus with a thickness of 40 µm was produced using a single-shaft extruder (manufactured by Toshiba Machinery Co., Ltd., cylinder set temperature: 250°C), a T-die (1700 mm wide, set temperature: 250°C), a casting roller (set temperature: 60°C), and a winding machine. The in-plane phase difference Re(550) of the PC resin film was 3.0 nm.

[0075] [Comparative Example 1] Prepare an acrylic resin film with a thickness of 40µm (manufactured by Kaneka Corporation, product name "HTX-Z").

[0076] [Table 1]

[0077] [Evaluate] As can be clearly seen from Table 1, if the shear strength of the resin film is above 2.5N, the transverse cracks at the end face of the resin film can be suppressed during the shaping process.

[0078] Industrial availability The resin film of this invention can be applied to various industrial products, and is especially suitable for use in decorative films, polarizing plates and other optical components.

[0079] 1: Resin film 2:Polarizer 3: Processing thin films 31: Irregular Shape Processing Department 31a: concave part 100:Polarizing plate

Claims

1. A resin film having a shear breaking strength of 2.5 N or more; a thickness of 40 µm or more; an in-plane phase difference Re(550) of 3 nm or less; and being composed of a polycarbonate resin; wherein the polycarbonate resin comprises: a structural unit derived from a dihydroxy compound (A) of formula (2) below, a structural unit derived from an alicyclic dihydroxy compound (B) of formula (I) below, and a carbonate group connected thereto; HOCH2-R1-CH2OH (I) (in formula (I), R1 represents a cycloalkyl group having 4 to 20 carbon atoms).

2. A method for manufacturing a processed film, comprising shaping the resin film as claimed in claim 1.

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