JP7220311B1 - surface treatment film - Google Patents

Abstract

Kind Code: A1 A surface-treated film is provided that has a thin base layer and is less likely to break. The surface-treated film comprises a base layer having a thickness of less than 20 μm, a coating layer provided on the surface of the base layer, and a tear strength of 0.5 N or more at a temperature of 23° C. and a relative humidity of 55%. and a first end. [Selection drawing] Fig. 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 coating film such as a retardation layer or a hard coat layer is formed 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, etc.).

JP 2020-54939 A 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] At a temperature of 23 ° C. and a relative humidity of 55%, a cross hatch test is performed by forming 100 cross hatches in the coating layer of the surface treatment film, and 90 or more crosses are formed on the base layer. The surface-treated film according to any one of [1] to [3], which leaves a hatch.
[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 conveying step 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 comprises a substrate layer 11 having a thickness of less than 20 μm, a coating layer 12 provided on the surface of the substrate layer 11, a temperature of 23° C., a relative humidity of 55 and a first end portion 10 having a tear strength in % of 0.5 N or more.

In the surface-treated film 1, the substrate layer 11 and the coating layer 12 are in direct contact. The surface-treated film 1 has 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 have the uncoated region 21 .

The first end portion 10 includes an end that is a tear start position when the surface-treated film 1 is torn, and is provided along at least a part of the side 15 where the end is located when the surface-treated film 1 is viewed from above. It is an area where 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 of the surface-treated film 1 in plan view, and along part or all of two or more sides may be provided. 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 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, may be 1.0 N or more, or 1.2 N or more. , may be 1.5 N or more, may be 1.8 N or more, is usually 5.0 N or less, may be 4.5 N or less, and may be 4.0 N or less There may be.

The tearing strength of the first end 10 is the tearing strength when the surface-treated film 1 is torn from the end of the surface-treated film 1 in a direction intersecting the side 15 where the end is located, with the tear-starting position being the end of the surface-treated film 1. , can be measured by the method described in Examples below. 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 end of the base layer 11 where the first end 10 is formed so as to include the uncoated region 21 where the coating layer 12 is not provided on the surface of the base layer 11 The first end portion 10 is coated with a coating material containing a solvent that is less likely to cause deterioration of the base layer 11 by making the thickness of the end portion larger than the thickness of the base layer 11 other than the end portion over the entire portion. Examples include a method of forming the coating layer 12 and a method of forming the coating layer 12 having high toughness on the first end portion 10 .

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 in the first end 10 is preferably 0.6 mm or more, It may be 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 distance between the central position in the extending direction of the first end 10 of the sample taken from the surface treatment film 1 and the position 1 cm in both directions (horizontal direction) along the extending direction from this central position. It refers to the average value of the shortest distances from the edge of the base material layer 11 to the edge of the coating layer 12 at a total of three points, and can be determined by the method described in Examples below. 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 calculated. Let distance L be the value obtained by averaging. 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 long, it is stored and transported in a rolled state. In the roll body, the difference between the thickness of the coated region 22 and the uncoated region 21 of the surface-treated film 1 and the difference in behavior such as shrinkage and expansion that occur during storage of the surface-treated film 1 are caused. Therefore, the end face of the roll body may be wavy. The surface-treated film 1 unwound from a roll having wavy edges may also be deformed. 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 suppress deformation of the surface-treated film 1 unwound from the roll body. You can also

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 to be described later, the first end 10 is torn in a direction intersecting the side 15. Breakage of the end portion 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 because, in 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 surface on the base layer 11 is hard to absorb. It is presumed that the coating region 22 is fragile due to the coating layer 12 being susceptible to damage. 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 edges during transportation or the like, the surface-treated film 1 having the first edge 10 having a tear strength of 0.5 N or more as described above cannot be It is presumed that breakage of the one end portion 10 can be suppressed.

The surface-treated film 1 preferably leaves 90 or more cross-hatches on the base layer 11 in a cross-hatch test performed by forming 100 cross-hatches in the coating layer 12, and preferably 95 or more. It is more preferable that there remain, and it is further preferable that 100 remain. 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-treated film 1 having excellent adhesion between the substrate layer 11 and the coating layer 12, breakage of the first end portion 10 of the surface-treated film 1 can be prevented. can be effectively suppressed. In the crosshatch test, at a temperature of 23° C. and a relative humidity of 55%, 100 crosshatch of 1 mm square are cut on the surface of the coating layer 12 of the surface treatment film 1, and the adhesive tape attached to the crosshatch is peeled off. This is a test, and can be performed by the method described in the examples below.

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 film; (meth)acrylic resin film composed of poly(meth)acrylic acid ester; cellulose resin film such as triacetyl cellulose; polycarbonate film; polyamide film such as nylon or aromatic polyamide; be done. 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, is usually 1 μm or more, and may be 5 μm or more. .

(Coating layer)
The coating layer 12 is a layer for providing the surface treatment film 1 with at least one or more specific functions selected from hard coat properties, antiglare properties, antireflection properties, antistatic properties, antifouling properties, and the like. can be 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 preferable. 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 are, for example, a method of coating using a gravure roll that has been unevenly processed according to the width of the coated region 22; The gravure roll and the substrate layer 11 can be formed by a method of coating such that the gravure roll and the base material layer 11 are not in contact by, for example, attaching a film or providing claws on the surface of the gravure roll 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, and 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. In order to suitably form the coating layer 12 and/or the functions possessed by the coating layer 12, the coating material includes, in addition to the curable compounds and resins described above, 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 may be included.

The curable compound contained in the composition containing a curable compound includes active energy ray-curable resins such as ultraviolet-curable resins and electron beam-curable resins; thermosetting resins; A monomer having a polymerizable group; an oligomer having a polymerizable group; 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. (Meth)acrylate monomers and/or (meth)acrylic resins include polyfunctional (meth)acrylates, polyfunctional urethanized (meth)acrylates, polyol (meth)acrylates, and, if necessary, two or more hydroxyl groups. and a curable mixture containing a (meth)acrylic polymer having an alkyl group containing.

Examples of polyfunctional (meth)acrylates include, for example, di- or tri-(meth)acrylate of trimethylolpropane, tri- or tetra-(meth)acrylate of pentaerythritol, and (meth) having at least one hydroxyl group in the molecule. Polyfunctional urethane-modified (meth)acrylates, which are reaction products of acrylates and diisocyanates, and the like can be mentioned. 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 hydroxy (meth) acrylate having at least one hydroxyl group in the molecule is prepared from (meth) acrylic acid and/or a (meth) acrylic acid ester and a polyol, and this is reacted with a diisocyanate, Polyfunctional urethanized (meth)acrylates can be produced. The polyfunctional urethane-modified (meth)acrylate produced in this manner functions as the UV-curable resin described above. In its production, (meth)acrylic acid and / or (meth)acrylic acid ester may be used alone or in combination of two or more. Similarly, polyols and diisocyanates One type may be used, or two or more types may be used in combination.

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

The polyol used in forming the polyfunctional urethanized (meth)acrylate is a compound having at least two hydroxyl groups in the molecule, and specific examples thereof 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, 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 , glucose 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 are used. Specific examples thereof include tetramethylene diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, 2,4-tolylene diisocyanate, 4,4′-diphenyl diisocyanate, 1,5-naphthalene diisocyanate, 3,3′-dimethyl -4,4'-diphenyl diisocyanate, xylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, and among these diisocyanates having an aromatic ring, nucleus-hydrogenated diisocyanates.

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 2,3-dihydroxypropyl ( A polymer containing meth)acrylate as a structural unit, a polymer containing 2-hydroxyethyl (meth)acrylate as a structural unit together with 2,3-dihydroxypropyl (meth)acrylate, and the like can be mentioned.

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 was subjected to a pencil hardness test ( (measured with the surface-treated film placed on a glass plate) preferably exhibits a hardness of 8B or more, and may be 5B or more. 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 substance).

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, or 1 μm or more. Moreover, it may be 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 applied to the surface of the base layer 11 (the side opposite to the side to which the protective film is laminated). It can be formed 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, and inkjet coating. and the like. 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 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 a property of transmitting linearly polarized light having a plane of vibration 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, and has a composition containing a compound having absorption anisotropy and liquid crystallinity. It may be a film containing a liquid crystalline linear polarizing layer formed by coating a material on a substrate 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, is obtained by subjecting a PVA-based film such as a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene-vinyl acetate copolymer-based partially saponified film, to a dyeing treatment with iodine and a stretching treatment. and the like. 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 linear polarizing layer, which is a PVA-based film, involves 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. may include a step of forming a resin layer on the substrate. 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, then the base film and the 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, or may be 5 μm or more, and is preferably 30 μm or less, and 15 μm or less. is more preferable, and may be 10 μm or less, or may be 8 μm or less.

A film containing a liquid crystalline linear polarizing layer is obtained by coating a base film with 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. A linear polarizing layer obtained by The liquid crystalline linear polarizing layer may be a cured product of a polymerizable liquid crystal compound and may contain an orientation 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 base 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 substrate film and the linearly polarizing layer formed as described above is preferably as small as possible. It is 5 μm or less, more preferably 0.5 to 3 μm.

(other layers)
Protective layers as other layers include, for example, a protective film that is a film formed from a thermoplastic resin that is excellent in transparency, mechanical strength, thermal stability, water barrier properties, isotropy, stretchability, etc.; Examples thereof include an overcoat layer formed from a composition excellent in solvent properties, transparency, mechanical strength, thermal stability, shielding properties, isotropy, 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.

Specific examples of thermoplastic resins for forming protective films include cellulose resins such as triacetyl cellulose; polyester resins such as polyethylene terephthalate and polyethylene naphthalate; polyethersulfone resins; polysulfone resins; polycarbonate resins; Polyamide resin such as polyamide; Polyimide resin; Polyolefin resin such as polyethylene, polypropylene, ethylene/propylene copolymer; Resins; polystyrene resins; polyvinyl alcohol resins, and mixtures thereof. 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 called a so-called pressure-sensitive adhesive. It is a thing. 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, known pressure-sensitive adhesives having excellent optical transparency can be used without particular limitation. can use objects. 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 is obtained by blending an ultraviolet-curable compound such as a polyfunctional acrylate with the above-described pressure-sensitive adhesive composition, and curing the layer formed by coating with ultraviolet rays. can form a harder pressure-sensitive adhesive layer. An 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 the adherend and is cured by energy ray irradiation, thereby adjusting the adhesive strength. have

The pressure-sensitive adhesive composition and the active energy ray-curable pressure-sensitive adhesive composition optionally contain an antioxidant, a tackifier, a thermoplastic resin, a filler, a flow control agent, a plasticizer, an antifoaming agent, and an antistatic agent. , solvents and other additives.

(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. be done. 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; Ester; cellulosic resins such as triacetylcellulose, diacetylcellulose and cellulose acetate propionate; polycarbonate; polysulfone; polyethersulfone; polyetherketone; polyphenylene sulfide;

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 The present invention will be described in more detail below 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 is gravure-coated on one side of the COP film so that an uncoated area is formed along a pair of opposing sides (both ends in the width direction). formed. 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 the sample collected from the surface-treated film was attached to a glass plate, and the center position of the end of the COP film (the end where the coating layer was not formed) in the extending direction and this center position The shortest distance from the end of the COP film to the coating layer is determined at a total of three points, 1 cm in the left and right direction (both directions along the extension direction) from the point of the bottom, and averaged to obtain the surface The distance L between the edge of the COP film of the treated film and the edge of the coating layer was determined. The shortest distance is determined by acquiring a thickness plot while moving from the edge of the sample COP film toward the coating layer using a dual-mode 3D confocal/interferometry system PLμ2300 (manufactured by Senso 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. It was confirmed whether or not there was breakage when the long surface-treated film (the long base material layer for Reference Examples 1 and 3) was transported by transport rolls so as not to cause transport problems such as meandering. . 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. In the end portion where the uncoated region of the surface treatment film is formed, the edge of the surface treatment film, the uncoated region 21, and the coated region 22 are included, and the side where the end of the surface treatment film is located extends. A rectangular sample piece 31 was cut out so as to have a size of 50 mm in the direction and 70 mm in the direction orthogonal to the side (FIG. 3). Two lead tapes are placed on one surface 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 that constitute the above-mentioned sides of the surface-treated film. (Piolan cloth curing tape green, 50 mm x 25 mm, Y-09-GR, manufactured by Diatex) 35, 35 are attached (hereinafter, the side 33 to which the lead tape is attached is sometimes referred to as "attachment side 33". ). Each lead tape 35 has a length of 50 mm and a width of 20 mm. A gap of 1 mm is formed between the two lead tapes 35 at the center of the mounting side 33 of the sample piece 31, and the width direction of the lead tape 35 is the mounting side. It was attached to the sample piece 31 so that it was parallel to 33 and a length of 10 mm 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, a lead tape group in which two lead tapes (the lead tapes attached to both sides of the sample piece 31) are superimposed on the sample piece 31 in plan view as shown in FIG. were attached with an interval (gap) of 1 mm.

Of the lengthwise ends of the lead tape 35 attached to the sample piece 31, the end opposite to the side attached to the sample piece 31 was vertically scanned with an autograph ("AGS-50NX" manufactured by Shimadzu Corporation). Each was fixed to a chuck. Then, one of the two lead tape groups is placed on one side with the plane of the sample piece 31 as a reference, and the other of the two lead tape groups is placed with the plane of the sample piece 31 as a reference. A 180 ° tensile test is performed by pulling at a speed of 300 mm / min in mutually opposite directions (vertical direction with respect to the plane of the sample piece 31) with respect to the plane of the sample piece 31 so that it is on the other side. The peak value (magnitude of force) that appears when the end portion including the attachment side 33 of is torn was 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%, 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, the sample is placed in a direction perpendicular to the side Ease of tearing was evaluated when a piece was torn by hand. Evaluation of easiness to tear is evaluated as difficult to tear when the base layer (Reference Example 1) having a thickness of 13 μm is torn according to the above procedure (following "B"). evaluated as
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 (7)

a base layer having a thickness of less than 20 μm;
A coating layer provided on the surface of the base material layer;
a first end having a tear strength of 1.7 N or more at a temperature of 23 ° C. and a relative humidity of 55%;
The thickness of the coating layer is 5 μm or less,
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, wherein the distance from the edge of the base material layer to the edge of the coating layer in the uncoated region is 5.5 mm or more and 50 mm or less. The surface treatment film according to claim 1, wherein the first end 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 in which 100 cross hatches are formed in the coating layer of the surface treatment film. , The surface-treated film according to claim 1 or 2. The surface-treated film according to any one of claims 1 to 3, wherein the base material layer is a cyclic olefin resin film. The surface treatment film according to any one of claims 1 to 4, 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 5, 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 6 and a linear polarizing layer.

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