JP2023102975A - surface treatment film - Google Patents

Abstract

To provide a surface treatment film whose fracture is suppressed, regardless of having a thin base material layer.SOLUTION: A surface treatment film includes a base material layer having a thickness of less than 20 μm, a coating layer provided on a surface of the base material layer, and a first end portion having a tear strength of 0.5 N or more at a temperature of 23°C and a relative humidity of 55%.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a surface-treated film, and more particularly to a polarizing plate provided with the surface-treated film and a method for producing the polarizing plate.

As an optical film used in display devices such as liquid crystal display devices and organic EL display devices, a surface treatment film provided with a coating film such as a retardation layer or a hard coat layer by coating a resin composition on the surface of a base layer such as a resin film is known (for example, Patent Documents 1 and 2).

Japanese Patent Application Laid-Open No. 2020-54939 JP 2011-59154 A

In recent years, there has been a demand for reducing the thickness of optical films used in display devices. Along with this, it is required to reduce the thickness of the substrate layer included in the surface-treated film. A surface-treated film in which a coating film is formed on a thin base layer sometimes breaks at the edges during transportation.

SUMMARY OF THE INVENTION An object of the present invention is to provide a surface-treated film in which breakage is suppressed while having a base layer with a small thickness, a polarizing plate having the same, and a method for producing a polarizing plate.

The present invention provides the following surface-treated film, polarizing plate, and method for producing a polarizing plate.
[1] a base layer having a thickness of less than 20 μm;
A coating layer provided on the surface of the base material layer;
and a first end having a tear strength of 0.5 N or more at a temperature of 23° C. and a relative humidity of 55%.
[2] the first end includes an uncoated region where the coating layer is not provided on the surface of the base material layer;
The surface-treated film according to [1], wherein the distance from the edge of the base layer to the edge of the coating layer in the uncoated region is 0.6 mm or more.
[3] The surface treatment film according to [1] or [2], wherein the first end portions are provided along a pair of opposite sides of the surface treatment film in plan view.
[4] The surface-treated film according to any one of [1] to [3], wherein 90 or more cross-hatches remain on the substrate layer in a cross-hatch test performed by forming 100 cross-hatches in the coating layer of the surface-treated film at a temperature of 23° C. and a relative humidity of 55%.
[5] The surface-treated film according to any one of [1] to [4], wherein the substrate layer is a cyclic olefin resin film.
[6] The surface-treated film according to any one of [1] to [5], wherein the coating layer is a cured product layer of a composition containing an ultraviolet curable resin.
[7] The surface-treated film is a long body,
The surface treatment film according to any one of [1] to [6], wherein the first end portions are provided at both width direction end portions of the surface treatment film.
[8] A polarizing plate comprising the surface-treated film according to any one of [1] to [7] and a linear polarizing layer.
[9] A method for producing a polarizing plate according to [8],
A step of preparing a laminate having the surface-treated film and a protective film detachably laminated on the base layer side of the surface-treated film;
A step of conveying the surface-treated film obtained by peeling the protective film from the laminate;
A method for producing a polarizing plate, comprising a step of laminating the surface-treated film obtained in the step of conveying and the linear polarizing layer.

According to the present invention, it is possible to provide a surface-treated film in which breakage is suppressed while having a base layer with a small thickness.

BRIEF DESCRIPTION OF THE DRAWINGS It is a top view which shows typically the surface treatment film which concerns on one Embodiment of this invention. 2 is a cross-sectional view taken along the line XX' of FIG. 1; FIG. FIG. 3 is a plan view schematically showing a sample piece used for measuring tear strength.

Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the following embodiments. All the drawings below are shown to aid understanding of the present invention, and the size and shape of each component shown in the drawings do not necessarily match the size and shape of the actual component.

(Surface treatment film)
FIG. 1 is a plan view schematically showing a surface-treated film according to one embodiment of the invention. FIG. 2 is a cross-sectional view taken along line XX' of FIG.

As shown in FIGS. 1 and 2, the surface-treated film 1 has a base layer 11 having a thickness of less than 20 μm, a coating layer 12 provided on the surface of the base layer 11, and a first end portion 10 having a tear strength of 0.5 N or more at a temperature of 23° C. and a relative humidity of 55%.

In the surface-treated film 1, the substrate layer 11 and the coating layer 12 are in direct contact. The surface-treated film 1 may have a coated region 22 in which the coating layer 12 is formed on the surface of the substrate layer 11 and an uncoated region 21 in which the coating layer 12 is not formed on the surface of the substrate layer 11, or may have the coated region 22 and not the uncoated region 21.

The first end 10 is a region that includes an end that is a tear start position when the surface-treated film 1 is torn, and that is provided along at least a portion of the side 15 where the end is located in plan view of the surface-treated film 1. The first end 10 may be a region extending along the entire side 15 as shown in FIG.

The first end 10 may be provided along part or all of at least one of the sides in plan view of the surface-treated film 1, and may be provided along part or all of two or more sides. The first end portion 10 is preferably provided along a pair of opposite sides 15, 15 of the surface-treated film 1 in plan view. As shown in FIGS. 1 and 2 , when the surface-treated film 1 is elongated, the first end portions 10 are preferably provided at both ends in the width direction W of the surface-treated film 1 .

The tear strength of the first end portion 10 at a temperature of 23 ° C. and a relative humidity of 55% is 0.5 N or more, preferably 0.8 N or more, 1.0 N or more, 1.2 N or more, 1.5 N or more, 1.8 N or more, usually 5.0 N or less, 4.5 N or less, or 4.0 N or less.

The tear strength of the first end portion 10 is the tear strength when the surface-treated film 1 is torn from the edge of the surface-treated film 1 in a direction that intersects the side 15 where the edge is located, with the edge of the surface-treated film 1 as the tear-starting position, and can be measured by the method described in the examples described later. As shown in FIG. 1, if the side 15 is straight, the tearing direction is perpendicular to the side 15 . The tearing direction may be rephrased as the direction in which the tear progresses when torn.

A method for forming the first end portion 10 having the tear strength in the surface-treated film 1 is not particularly limited. For example, the first end 10 is formed so as to include an uncoated region 21 in which the coating layer 12 is not provided on the surface of the base layer 11. The thickness of the end of the base layer 11 on which the first end 10 is formed is made larger than the thickness of the base layer 11 other than the end. A method such as forming a large coating layer 12 can be used.

When first end 10 includes uncoated region 21 , first end 10 may or may not include coated region 22 . When the first end 10 includes the uncoated region 21, the distance L from the end of the base layer 11 to the end of the coating layer 12 at the first end 10 is preferably 0.6 mm or more, 0.8 mm or more, 1.0 mm or more, or 1.5 mm or more. Although the upper limit of the distance L is not particularly limited, it may be, for example, 50 mm or less, or 40 mm or less. The distance L is the average value of the shortest distances from the end of the base layer 11 to the end of the coating layer 12 at a total of three positions, i.e., the central position in the extending direction of the first end 10 of the sample taken from the surface-treated film 1 and the position 1 cm in both directions (horizontal direction) along the extending direction from the central position, and can be determined by the method described in the examples described later. When the surface-treated film 1 is a long body, samples are collected from both ends in the length direction of the long body, and the average value of the shortest distances determined by the above procedure for each of the two collected samples is further averaged to obtain the distance L. When the surface-treated film 1 is a sheet, it is sampled at an arbitrary position.

When the distance L is within the above range, it becomes easier to adjust the tear strength of the first end portion 10 within the above range. When the surface-treated film 1 is a long body, it is stored and transported in the form of a rolled-up surface-treated film 1 . In the roll body, the end face of the roll body may be wavy due to the difference between the thickness of the coated region 22 and the thickness of the uncoated region 21 of the surface-treated film 1 and the difference in behavior such as shrinkage and expansion occurring during storage of the surface-treated film 1. Deformation may also occur in the surface-treated film 1 unwound from a roll having a wavy end surface. In the surface-treated film 1, when the distance L is within the above range, it is possible to form a well-wound roll body, and it is possible to suppress deformation of the surface-treated film 1 unwound from the roll body.

Since the surface-treated film 1 has the first end 10, for example, when the surface-treated film 1 is transported in the manufacture of a polarizing plate, which will be described later, the first end 10 is torn in a direction intersecting the side 15. Breakage of the first end 10 can be suppressed. On the other hand, in a surface-treated film having edges with a tear strength of less than 0.5 N, the edges tend to break during transport. This is presumably because, in the case of the surface-treated film 1 having a small thickness of the base layer 11, such as when the thickness of the base layer 11 is less than 20 μm, it is difficult for the base layer 11 to absorb the impact, and the hard coating layer 12 on the base layer 11 is easily damaged, so that the coating region 22 becomes brittle. It is believed that the brittle region is likely to break when subjected to external force or deformation. Since the surface-treated film 1 is likely to be subjected to an external force or deformed at its ends during transportation or the like, the surface-treated film 1 having the first end 10 having a tear strength of 0.5 N or more is presumed to be able to suppress breakage of the first end 10.

The surface-treated film 1 preferably has 90 or more cross-hatches remaining on the base layer 11 in a cross-hatch test performed by forming 100 cross-hatches in the coating layer 12, more preferably 95 or more, and even more preferably 100. Such a surface-treated film 1 is considered to have excellent adhesion between the substrate layer 11 and the coating layer 12 . In the surface-treated film 1 having excellent adhesion, it is considered that the above-described breakage is likely to occur at the edges that are subjected to an external force or are deformed. Therefore, by providing the above-described first end portion 10 to the surface treatment film 1 having excellent adhesion between the base material layer 11 and the coating layer 12, breakage of the first end portion 10 of the surface treatment film 1 can be effectively suppressed. The cross hatch test is performed by cutting 100 cross hatches of 1 mm square on the surface of the coating layer 12 of the surface treatment film 1 at a temperature of 23 ° C. and a relative humidity of 55%, and peeling off the adhesive tape attached to the cross hatches.

The surface-treated film 1 may be a sheet or an elongated body that can be continuously transported. In this specification, a long body refers to a surface-treated film having a length of, for example, 30 m or more and 15000 m or less. When the surface-treated film 1 is elongated, it is preferable that the first ends 10 are provided at both ends in the width direction W as shown in FIG.

The surface treatment film 1 can have at least one or more functions among hard coat properties, antiglare properties, antireflection properties, antistatic properties, antifouling properties, and the like. These properties can be imparted by the coating layer 12 . By bonding the surface-treated film 1 to the surface of an adherend such as a linearly polarizing layer to be described later, it is possible to provide the adherend with the properties described above. The substrate layer 11 side of the surface-treated film 1 is preferably bonded to an adherend.

(Base material layer)
The base material layer 11 is used to cover the surface of the adherend and support the coating layer 12 . The base material layer 11 is preferably a resin film, preferably a transparent resin film. As the transparent resin film, for example, a film formed using a resin known in the field of optical films, or the like can be used. Examples of transparent resin films include polyolefin films such as polyethylene, polypropylene, and ethylene/propylene copolymers; cyclic olefin resin films made of norbornene-based polymers, etc.; polyester films made of polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate; (meth)acrylic resin films made of poly(meth)acrylic acid esters; The transparent resin film is preferably one or more of a cyclic olefin resin film, a polyester film, and a (meth)acrylic resin film, and more preferably a cyclic olefin resin film. "(Meth)acryl" represents at least one of acryl and methacryl. The same applies to "(meth)acrylate" and the like.

The thickness of the base material layer 11 is less than 20 μm, may be 18 μm or less, may be 15 μm or less, may be 13 μm or less, and is usually 1 μm or more, and may be 5 μm or more.

(Coating layer)
The coating layer 12 is a layer for imparting to the surface-treated film 1 at least one or more specific functions among hard coat properties, antiglare properties, antireflection properties, antistatic properties, antifouling properties, and the like. The coating layer 12 includes a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, an antifouling layer, and the like.

The coating layer 12 can be formed by coating the substrate layer 11 with a coating material for forming the coating layer 12 . As the coating method of the coating material, known methods can be used without particular limitation, but die coating or gravure coating is preferred. From the viewpoint of coating accuracy, gravure coating is more preferable.

The uncoated region 21 and the coated region 22 of the surface-treated film 1 can be formed, for example, by a method of coating using a gravure roll that has been unevenly processed to match the width of the coated region 22; a method of coating so that the gravure roll and the base material layer 11 are not in contact with each other by, for example, attaching a film or providing claws on the surface of the gravure roll where the uncoated region 21 is to be formed. The width of the coating area 22 can be adjusted by adjusting the condition of the surface of the gravure roll as described above. The width of the uncoated area 21 can be adjusted by the viscosity of the coating material used to form the coated area 22 . When manufacturing the surface-treated film 1, it is preferable to adjust the viscosity of the coating material so that the variation in the width of the uncoated region 21 is within 0.5 mm.

The viscosity of the coating material at a temperature of 25° C. is, for example, 1 mPa·s or more and 150 mPa·s or less, preferably 3 mPa·s or more and 100 mPa·s or less, more preferably 5 mPa·s or more and 50 mPa·s or less. If the viscosity is too low, coating unevenness may become noticeable, and if the viscosity is too high, it may be difficult to adjust the film thickness. When the viscosity is 1 mPa·s or more and 150 mPa·s or less, it tends to be easy to adjust the coating film thickness. The viscosity can be a value measured by a Brookfield type viscometer (B type viscometer, manufactured by Brookfield).

The coating material includes a composition containing a curable compound; a composition containing a resin other than the curable compound, and the like. The coating material may contain fillers such as organic fine particles or inorganic fine particles, antistatic agents, antifouling agents, colorants, ultraviolet absorbers, antioxidants, light stabilizers, flame retardants, viscosity modifiers, cross-linking agents, coupling agents, leveling agents, antifoaming agents, solvents, and the like, in addition to the above-described curable compounds and resins, in order to form the coating layer 12 and/or the functions of the coating layer 12 appropriately.

Examples of the curable compound contained in the composition containing a curable compound include active energy ray-curable resins such as ultraviolet-curable resins and electron beam-curable resins; thermosetting resins; monomers having polymerizable groups such as (meth)acryloyl groups and vinyl groups; oligomers having polymerizable groups. Examples of resins other than curable compounds include thermoplastic resins.

The coating layer 12 is preferably a cured layer of a composition containing an active energy ray-curable resin, more preferably a cured layer of a composition containing an ultraviolet-curable resin. The composition containing an ultraviolet curable resin is preferably an acrylic resin composition containing a (meth)acrylate monomer and/or a (meth)acrylic resin. Examples of (meth)acrylate monomers and/or (meth)acrylic resins include polyfunctional (meth)acrylates, polyfunctional urethanized (meth)acrylates, polyol (meth)acrylates, and optionally curable mixtures containing (meth)acrylic polymers having alkyl groups containing two or more hydroxyl groups.

Examples of polyfunctional (meth)acrylates include trimethylolpropane di- or tri-(meth)acrylates, pentaerythritol tri- or tetra-(meth)acrylates, and polyfunctional urethanized (meth)acrylates which are reaction products of (meth)acrylates and diisocyanates having at least one hydroxyl group in the molecule. These polyfunctional (meth)acrylates may be used alone or in combination of two or more.

Polyfunctional urethane-modified (meth)acrylates are produced using, for example, (meth)acrylic acid and/or (meth)acrylic acid esters, polyols, and diisocyanates. Specifically, a polyfunctional urethanized (meth)acrylate can be produced by preparing a hydroxy (meth)acrylate having at least one hydroxyl group in the molecule from (meth)acrylic acid and/or a (meth)acrylic acid ester and a polyol and reacting it with a diisocyanate. The polyfunctional urethane-modified (meth)acrylate produced in this manner functions as the UV-curable resin described above. In the production thereof, (meth)acrylic acid and/or (meth)acrylic acid ester may be used alone or in combination of two or more. Polyols and diisocyanates may be used either alone or in combination of two or more.

As the (meth)acrylic ester used for forming the polyfunctional urethane-modified (meth)acrylate, a linear or cyclic alkyl ester of (meth)acrylic acid can be used, and specific examples thereof include alkyl (meth)acrylates such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, isopropyl (meth)acrylate, and butyl (meth)acrylate; and cycloalkyl (meth)acrylates such as cyclohexyl (meth)acrylate.

The polyol used in forming the polyfunctional urethane-modified (meth)acrylate is a compound having at least two hydroxyl groups in the molecule, and specific examples include ethylene glycol, propylene glycol, 1,3-propanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, 1,3-butanediol, 1,4-butanediol, 1,6-hexanediol, 1,9-nonanediol, 1,10-decanediol, and 2,2,4-trimethyl. -1,3-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol ester of hydroxypivalic acid, cyclohexanedimethylol, 1,4-cyclohexanediol, spiroglycol, tricyclodecanedimethylol, hydrogenated bisphenol A, ethylene oxide-added bisphenol A, propylene oxide-added bisphenol A, trimethylolethane, trimethylolpropane, glycerin, 3-methylpentane-1,3,5-triol, pentaerythritol , dipentaerythritol, tripentaerythritol, glucoses, and the like.

The diisocyanate used in forming the polyfunctional urethanized (meth)acrylate is a compound having two isocyanato groups (-NCO) in the molecule, and various aromatic, aliphatic or alicyclic diisocyanates can be used. Specific examples include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 3,3'- Examples include dimethyl-4,4'-diphenyl diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and nucleus-hydrogenated diisocyanates having an aromatic ring among these.

A (meth)acrylic polymer having an alkyl group containing two or more hydroxyl groups has an alkyl group containing two or more hydroxyl groups in one structural unit, and specific examples thereof include a polymer containing 2,3-dihydroxypropyl (meth)acrylate as a structural unit, and a polymer containing 2,3-dihydroxypropyl (meth)acrylate and 2-hydroxyethyl (meth)acrylate as structural units.

A composition containing a curable compound can contain a polymerization initiator in addition to the curable compound. Examples of the polymerization initiator include photopolymerization initiators and radical polymerization initiators, and known polymerization initiators can be used.

When the coating layer 12 is a hard coat layer, the coating layer 12 has a function of improving the surface hardness of the base material layer 11, and can improve the scratch resistance of the surface. The hard coat layer preferably exhibits a value of 8B or harder in a pencil hardness test (measured by placing the surface-treated film on a glass plate) defined in JIS K 5600-5-4:1999 "General test methods for paint-Part 5: Mechanical properties of coating film-Section 4: Scratch hardness (pencil method)", and may be 5B or harder. The coating layer 12 is preferably a hard coat layer.

When the coating layer 12 is an antiglare layer, the coating layer 12 can have functions such as improving visibility, suppressing reflection of external light, and reducing moire (interference fringes). The antiglare layer can have a fine uneven shape on the surface. The fine irregularities can be formed by adding a filler to the antiglare layer, or by finely embossing the surface.

When the coating layer 12 is an antireflection layer, the coating layer 12 can have a function of suppressing reflection of external light. The antireflection layer can be a layer having a refractive index smaller than that of the substrate layer 11, and may contain fine particles, for example.

When the coating layer 12 is an antistatic layer, the coating layer 12 can have a function of suppressing the generation of static electricity. The antistatic layer can contain an antistatic agent (conductive material).

When the coating layer 12 is an antifouling layer, the coating layer 12 can impart functions such as water repellency, oil repellency, sweat resistance, and antifouling properties to the surface-treated film 1 . The antifouling layer can contain antifouling agents such as fluorine-containing organic compounds such as fluorocarbons, perfluorosilanes, and polymeric compounds thereof.

The thickness of the coating layer 12 may be, for example, 1 nm or more, 10 nm or more, 50 nm or more, 500 nm or more, 1 μm or more, 15 μm or less, 10 μm or less, or 5 μm or less.

(Polarizer)
The polarizing plate of this embodiment has a surface treatment film 1 and a linear polarizing layer. The polarizing plate can have the surface treatment film 1 on one side or both sides of the linear polarizing layer. When the surface-treated films 1 are provided on both sides of the linear polarizing layer, the two surface-treated films 1 may be of the same type or of different types. It is preferable that the substrate layer 11 side of the surface-treated film 1 faces the linear polarizing layer.

The polarizing plate may have a bonding layer for bonding the surface-treated film 1 and the linear polarizing layer. The lamination layer is a pressure-sensitive adhesive layer or an adhesive layer. When the polarizing plate has a bonding layer, it is preferably provided on the substrate layer 11 side of the surface-treated film 1 .

When the polarizing plate has the surface-treated film 1 on one side of the linearly polarizing layer, the other side of the linearly polarizing layer may have a layer other than the surface-treated film 1 . Other layers include a protective layer, a retardation layer, an adhesive layer, and the like. The linear polarizing layer and another layer may be laminated so as to be in direct contact, or may be laminated via a bonding layer when the other layer is a protective layer or a retardation layer.

(Manufacturing method of polarizing plate)
The manufacturing method of the polarizing plate of this embodiment includes:
A step of preparing a laminate having a surface-treated film 1 and a protective film peelably laminated on the substrate layer 11 side of the surface-treated film 1;
A step of conveying the surface-treated film 1 obtained by peeling the protective film from the laminate;
A step of laminating the surface-treated film 1 obtained in the step of conveying and a linearly polarizing layer can be included.

In the preparation step, for example, after laminating a protective film on one side of the base layer 11, the coating layer 12 is formed on the surface of the base layer 11 (the side opposite to the side where the protective film is laminated) to obtain a laminate. The coating layer 12 can be formed by coating a coating material on the side of the substrate layer 11 opposite to the protective film side. Examples of the method of applying the coating material include known methods, such as gravure coating, bar coating, spray coating, spin coating, dip coating, die coating, inkjet coating, and the like. It can be carried out by one or more methods. After applying the coating material to the base material layer 11, depending on the type of the coating material, drying and/or curing of a curable compound contained in the coating material may be performed.

In the transporting step, for example, while transporting the laminate, the protection film can be peeled off from the laminate to separate the surface treatment film 1 and the protection film, and these can be transported respectively. The laminate, the surface-treated film 1, and the protection film can be transported by a known transport method, such as transport rolls and/or transport belts. The tension during transport by the transport rolls can be adjusted so that the transported film is transported without meandering. The tension during transport by the transport rolls can be adjusted so that the transported film is not broken.

In the lamination step, for example, the side of the surface-treated film 1 exposed by peeling off the protective film (base material layer 11 side) and the linear polarizing layer can be laminated via a bonding layer or the like.

The surface treatment film 1 has the tear strength of the first end portion 10 within the range described above. Therefore, in the surface-treated film 1 conveyed in the conveying step, breakage of the first end portion 10, which is likely to receive an external force or be deformed, can be suppressed. Thereby, a yield can be improved and a polarizing plate can be manufactured.

(linear polarizing layer)
The linearly polarizing layer has the property of transmitting linearly polarized light having a vibration plane perpendicular to the absorption axis when non-polarized light is incident thereon. The linear polarizing layer may be a polyvinyl alcohol-based resin film (hereinafter sometimes referred to as "PVA-based film") in which iodine is adsorbed and oriented, or may be a film including a liquid crystalline linear polarizing layer formed by applying a composition containing a compound having absorption anisotropy and liquid crystallinity to a base film. The compound having absorption anisotropy and liquid crystallinity may be a mixture of a dye having absorption anisotropy and a compound having liquid crystallinity, or may be a dye having absorption anisotropy and liquid crystallinity.

The linear polarizing layer, which is a PVA-based film, includes, for example, a PVA-based film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, and a partially saponified ethylene/vinyl acetate copolymer film, which is dyed with iodine and stretched. If necessary, the PVA-based film having iodine adsorbed and oriented by the dyeing treatment may be treated with an aqueous boric acid solution, followed by a washing step of washing off the aqueous boric acid solution. A known method can be adopted for each step.

A polyvinyl alcohol-based resin (hereinafter sometimes referred to as "PVA-based resin") can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be polyvinyl acetate, which is a homopolymer of vinyl acetate, or may be a copolymer of vinyl acetate and another monomer that can be copolymerized with vinyl acetate. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The saponification degree of the PVA-based resin is usually about 85 to 100 mol %, preferably 98 mol % or more. The PVA-based resin may be modified, and for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The average degree of polymerization of the PVA-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000. The degree of saponification and average degree of polymerization of the PVA-based resin can be determined according to JIS K 6726 (1994). If the average degree of polymerization is less than 1,000, it is difficult to obtain desirable polarizing performance, and if it exceeds 10,000, film workability may be poor.

A method for producing a linearly polarizing layer that is a PVA-based film may include a step of preparing a base film, applying a solution of a resin such as a PVA-based resin on the base film, and performing drying or the like to remove the solvent to form a resin layer on the base film. A primer layer can be formed in advance on the surface of the substrate film on which the resin layer is formed. As the base film, a film using a resin material described as a thermoplastic resin used for forming a protective film as a protective layer to be described later can be used. Examples of the material for the primer layer include a resin obtained by cross-linking the hydrophilic resin used for the linear polarizing layer.

Next, the amount of solvent such as moisture in the resin layer is adjusted as necessary, and then the base film and resin layer are uniaxially stretched, and then the resin layer is dyed with iodine to adsorb and align iodine on the resin layer. Next, if necessary, the resin layer in which iodine is adsorbed and oriented is treated with an aqueous boric acid solution, followed by a washing step of washing off the aqueous boric acid solution. As a result, a resin layer in which iodine is adsorbed and oriented, that is, a PVA-based film to be a linear polarizing layer is produced. A known method can be adopted for each step.

A linearly polarizing layer produced by a production method using a base film can be obtained by laminating a protective layer and then peeling off the base film.

The thickness of the linear polarizing layer, which is a PVA-based film, is preferably 1 μm or more, may be 2 μm or more, may be 5 μm or more, is preferably 30 μm or less, more preferably 15 μm or less, may be 10 μm or less, and may be 8 μm or less.

A film containing a liquid crystalline linear polarizing layer is obtained by applying a composition containing a dye having liquid crystallinity and absorption anisotropy, or a composition containing a dye having absorption anisotropy and a polymerizable liquid crystal to a base film. The liquid crystalline linear polarizing layer may be a cured product of a polymerizable liquid crystal compound and may contain an alignment layer. The film containing the liquid crystalline linear polarizing layer may be a liquid crystalline linear polarizing layer or may have a laminated structure of a liquid crystalline linear polarizing layer and a substrate film. Examples of the base film include a film using a resin material described as a thermoplastic resin used for forming a protective film as a protective layer to be described later. Films containing a liquid crystalline linear polarizing layer include, for example, polarizing layers described in JP-A-2013-33249.

The total thickness of the base film and the linearly polarizing layer formed as described above is preferably as small as possible, but if it is too small, the strength tends to decrease and the workability tends to be poor.

(other layers)
Protective layers as other layers include, for example, a protective film that is a film formed from a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, stretchability, etc.; an overcoat layer formed from a composition having excellent solvent resistance, transparency, mechanical strength, thermal stability, shielding properties, isotropy, etc., and the like. The protective film is preferably laminated on the linearly polarizing layer via the bonding layer, and the overcoat layer is preferably laminated so as to be in direct contact with the linearly polarizing layer.

Polyamide resins such as nylon and aromatic polyamides; Polyimide resins; Polyolefin resins such as polyethylene, polypropylene, and ethylene/propylene copolymers; Vinyl alcohol resins, as well as mixtures thereof, may be mentioned. The thickness of the protective film is preferably 3 μm or more, more preferably 5 μm or more, and preferably 50 μm or less, more preferably 30 μm or less.

The overcoat layer can be formed, for example, by applying a material (composition) for forming the overcoat layer on the linear polarizing layer. Materials constituting the overcoat layer include, for example, photocurable resins, water-soluble polymers, and the like, and (meth)acrylic resins, polyvinyl alcohol-based resins, polyamide epoxy resins, and the like can be used. The thickness of the overcoat layer can be, for example, 0.1 μm or more and 10 μm or less.

The retardation layer as another layer may be a stretched film, or may include a cured product layer of a polymerizable liquid crystal compound. As the stretched film and the cured product layer constituting the retardation layer, known ones can be used.

The pressure-sensitive adhesive layer as another layer is a pressure-sensitive adhesive layer formed using a pressure-sensitive adhesive composition. The pressure-sensitive adhesive composition or the reaction product of the pressure-sensitive adhesive composition develops adhesiveness by attaching itself to an adherend such as a display element of a display device, and is referred to as a so-called pressure-sensitive adhesive. Moreover, the adhesive layer formed using the active-energy-ray-curable adhesive composition mentioned later can adjust a crosslinking degree and adhesive strength by irradiating an active-energy-ray.

As the pressure-sensitive adhesive composition, any known pressure-sensitive adhesive having excellent optical transparency can be used without particular limitation. For example, a pressure-sensitive adhesive composition containing a base polymer such as an acrylic polymer, a urethane polymer, a silicone polymer, or polyvinyl ether can be used. The adhesive composition may also be an active energy ray-curable adhesive composition, a heat-curable adhesive composition, or the like. Among these, a pressure-sensitive adhesive composition using an acrylic resin as a base polymer, which is excellent in transparency, adhesive strength, removability (reworkability), weather resistance, heat resistance, etc., is preferable. The pressure-sensitive adhesive layer preferably comprises a reaction product of a pressure-sensitive adhesive composition containing a (meth)acrylic resin, a cross-linking agent and a silane compound, and may contain other components.

The active energy ray-curable pressure-sensitive adhesive composition can form a harder pressure-sensitive adhesive layer by blending the above-described pressure-sensitive adhesive composition with an ultraviolet-curable compound such as a polyfunctional acrylate and irradiating the layer formed by coating with ultraviolet rays to cure it. The active energy ray-curable pressure-sensitive adhesive composition has the property of being cured by being irradiated with energy rays such as ultraviolet rays and electron beams. Since the active energy ray-curable pressure-sensitive adhesive composition has adhesiveness even before energy ray irradiation, it adheres to an adherend and is cured by energy ray irradiation to adjust the adhesive strength.

The pressure-sensitive adhesive composition and the active energy ray-curable pressure-sensitive adhesive composition may optionally contain additives such as antioxidants, tackifiers, thermoplastic resins, fillers, flow modifiers, plasticizers, antifoaming agents, antistatic agents, and solvents.

(Lamination layer)
The lamination layer is a pressure-sensitive adhesive layer or an adhesive layer. The pressure-sensitive adhesive layer includes those described above. The adhesive layer can be formed by curing the curable component in the adhesive composition. Examples of the adhesive composition for forming the adhesive layer include adhesives other than pressure-sensitive adhesives (adhesives), such as water-based adhesives and active energy ray-curable adhesives.

Examples of water-based adhesives include adhesives obtained by dissolving or dispersing polyvinyl alcohol resin in water. The method of drying when a water-based adhesive is used is not particularly limited. For example, a method of drying using a hot air dryer or an infrared ray dryer can be employed.

Active energy ray-curable adhesives include, for example, solvent-free active energy ray-curable adhesives containing curable compounds that are cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. Adhesion between layers can be improved by using a non-solvent active energy ray-curable adhesive.

(protection film)
The protective film is detachably laminated on the substrate layer 11 side of the surface-treated film 1 and used to cover and protect the surface of the surface-treated film. The protective film may have a multilayer structure in which a resin film and an adhesive layer are laminated, or may be a self-adhesive film having a single-layer structure.

As the resin film, for example, a film formed using a resin known in the field of optical films, or the like can be used. Examples of the resin constituting the resin film include polyolefins such as polyethylene and polypropylene; cyclic olefin resins such as norbornene-based polymers; polyvinyl alcohol; polyesters such as polyethylene terephthalate, polybutylene terephthalate, and polyethylene naphthalate;

When the protective film is a self-adhesive film, it may be a film formed from a polypropylene-based resin, a polyethylene-based resin, or the like.

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but the present invention is not limited to these examples.

[Examples 1 to 10, Comparative Examples 1 and 2, Reference Examples 1 to 3]
As a substrate layer, a cyclic olefin resin film (hereinafter sometimes referred to as "COP film") having a thickness shown in Table 1 was prepared. An acrylic resin composition containing an ultraviolet curable resin was gravure-coated on one side of the COP film so that an uncoated area was formed along a pair of opposing sides (both ends in the width direction) to form a coating film. The viscosity of the acrylic resin composition measured by the method described later was 20 mPa·s. After the coating film was dried, it was irradiated with ultraviolet rays to form a coating layer as a hard coat layer on the surface of the substrate layer, thereby obtaining a surface-treated film.

The COP film side of a sample collected from the surface-treated film was pasted to a glass plate, and the shortest distance between the end of the COP film and the coating layer was determined at a total of three positions: the center position in the extending direction of the end of the COP film (the end where the coating layer is not formed) and the position 1 cm in the left and right direction (both directions along the extending direction) from this center position. A distance L was determined. The shortest distance was determined by acquiring a thickness plot while moving from the edge of the COP film of the sample toward the coating layer using a dual-mode 3D confocal and interferometric system PLμ2300 (manufactured by Sensoso Japan Co., Ltd.) (lens: 20x (EPI 20x)). Table 1 shows the determined value of the distance L1.

The tear strength of the end of the surface-treated film where the uncoated region was formed (the substrate layer in Reference Examples 1 and 3) was measured by the procedure described later. The cross-hatch test was performed on the surface-treated films other than Reference Examples 1 and 3 according to the procedure described later. Table 1 shows the results.

Further, a long surface-treated film was obtained by forming a coating layer in the same manner as described above, except that a long base material layer was used as the base material layer. In Reference Examples 1 and 3, a long base material layer having no coating layer was used. Whether or not the long surface-treated film (the long base material layer in Reference Examples 1 and 3) was transported by transport rolls so as not to cause transport problems such as meandering was checked for breakage. Table 1 shows the results.

[Measurement of tear strength]
FIG. 3 is a plan view schematically showing a sample piece used for measuring tear strength. At the end where the uncoated region of the surface-treated film was formed, a rectangular sample piece 31 was cut out so as to include the end of the surface-treated film, the uncoated region 21, and the coated region 22, and to have a size of 50 mm in the direction in which the side where the end of the surface-treated film was located and a size of 70 mm in a direction orthogonal to the side (FIG. 3). Two lead tapes (Piolan cloth curing tape green, 50 mm × 25 mm, Y-09-GR, manufactured by Diatex) 35, 35 were attached to one side of the sample piece 31 so as to straddle the side 33, the uncoated region 21, and the coated region 22 of the sides of the sample piece 31 (side 33 to which the lead tape was attached is sometimes referred to as “mounting side 33”). Each lead tape 35 had a length of 50 mm and a width of 20 mm, and was attached to the sample piece 31 so that a gap of 1 mm was formed between the two lead tapes 35, 35 at the center of the attachment side 33 of the sample piece 31, the width direction of the lead tape 35 was parallel to the attachment side 33, and a 10 mm length range from one end was placed on the sample piece 31. Two lead tapes were also attached to the other surface of the sample piece 31 so as to overlap the lead tapes 35, 35 attached to one surface of the sample piece 31. FIG. As a result, as shown in FIG. 3, two sets of lead tapes (lead tapes attached to both sides of the sample piece 31) overlapped with each other were attached to the attachment side 33 of the sample piece 31 with an interval (gap) of 1 mm in the plan view of the sample piece 31.

Of the longitudinal ends of the lead tape 35 attached to the sample piece 31, the ends opposite to the side attached to the sample piece 31 were fixed to the upper and lower chucks of an autograph ("AGS-50NX", manufactured by Shimadzu Corporation). After that, a 180° tensile test was performed by pulling at a speed of 300 mm/min in opposite directions with respect to the plane of the sample piece 31 (vertical direction with respect to the plane of the sample piece 31) so that one of the two sets of lead tape groups was on one side with respect to the plane of the sample piece 31 and the other of the two sets of lead tape groups was on the other side with respect to the plane of the sample piece 31, and the end including the attachment side 33 of the sample piece 31 was torn. Occasionally appearing peak values (magnitude of force) were measured. The measurement was performed under conditions of a temperature of 23° C. and a relative humidity of 55%. This measurement was performed 5 times, and the average value of the magnitude of the measured force was taken as the tear strength.

[Tear test (sensory evaluation)]
A rectangular sample piece was prepared by the procedure described in the tear strength measurement above. Under conditions of a temperature of 23 ° C. and a relative humidity of 55%, the ease of tearing was evaluated by manually tearing the sample piece from the side of the sample piece where the edge of the surface treatment film (the edge where the uncoated area is formed) is located in the direction perpendicular to the side. The ease of tearing was evaluated as less likely to tear when the base layer (Reference Example 1) with a thickness of 13 μm was torn according to the above procedure (“B” below), and was evaluated as follows based on this.
A: Less likely to tear than B.
B: Hard to tear.
C: It is easier to tear than B.

[Measurement of viscosity]
The viscosity of the acrylic resin composition was measured at a temperature of 25° C. with a Brookfield viscometer (Brookfield viscometer).

[Cross hatch test]
100 (10×10) cross hatches of 1 mm square were cut into the coating layer surface of the surface treatment film so that the coating layer penetrated. An adhesive tape having a width of 24 mm (adhesive cellophane tape CT405AP-24, manufactured by Nichiban Co., Ltd.) was attached to the crosshatch, and then the adhesive tape was peeled off in a direction of 45° to the crosshatch surface. After peeling off the adhesive tape, the number of cross hatches remaining on the substrate layer was counted. The crosshatch test was performed under conditions of a temperature of 23°C and a relative humidity of 55%.

1 surface-treated film, 10 first end, 11 base layer, 12 coating layer, 15 side, 21 uncoated area, 22 coated area, 31 sample piece, 33 side (attachment side), 35 lead tape.

Claims (9)

a base layer having a thickness of less than 20 μm;
A coating layer provided on the surface of the base material layer;
and a first end having a tear strength of 0.5 N or more at a temperature of 23° C. and a relative humidity of 55%. The first end includes an uncoated region where the coating layer is not provided on the surface of the base material layer,
The surface-treated film according to claim 1, wherein the distance from the edge of the base material layer to the edge of the coating layer in the uncoated area is 0.6 mm or more. The surface treatment film according to claim 1 or 2, wherein the first end portion is provided along a pair of opposite sides of the surface treatment film in plan view. At a temperature of 23 ° C. and a relative humidity of 55%, 90 or more cross hatches remain on the base layer in a cross hatch test performed by forming 100 cross hatches in the coating layer of the surface treatment film. The surface treatment film according to any one of claims 1 to 3. The surface-treated film according to any one of claims 1 to 4, wherein the substrate layer is a cyclic olefin resin film. The surface treatment film according to any one of claims 1 to 5, wherein the coating layer is a cured product layer of a composition containing an ultraviolet curable resin. The surface-treated film is a long body,
The surface treatment film according to any one of claims 1 to 6, wherein the first end portions are provided at both width direction end portions of the surface treatment film. A polarizing plate comprising the surface-treated film according to any one of claims 1 to 7 and a linear polarizing layer. A method for manufacturing a polarizing plate according to claim 8,
A step of preparing a laminate having the surface-treated film and a protective film detachably laminated on the base layer side of the surface-treated film;
A step of conveying the surface-treated film obtained by peeling the protective film from the laminate;
A method for producing a polarizing plate, comprising a step of laminating the surface-treated film obtained in the step of conveying and the linear polarizing layer.

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