KR101924160B1 - Polarizing plate, polarizing plate with adhesive and liquid crystal display device - Google Patents

Abstract

The present invention provides a polarizing plate capable of peeling off a polarizing plate without causing breakage when the polarizing plate is peeled from a liquid crystal display device to which a polarizing plate is applied.
A polarizing plate comprising a polarizing film and a protective film, wherein the polarizing film has a thickness of 15 占 퐉 or less, a sticking strength per unit film thickness of 4.5 gf / 占 퐉 or more, a breaking strength of the protective film of 50 MPa Or more.

Description

TECHNICAL FIELD [0001] The present invention relates to a polarizing plate, a polarizing plate having a pressure-sensitive adhesive, and a liquid crystal display device having the polarizing plate and the polarizing plate.

The present invention relates to a polarizing plate, a polarizing plate having a pressure-sensitive adhesive, and a liquid crystal display.

The polarizing plate is widely used as a polarizing light supplying device in a display device such as a liquid crystal display device and also as a polarizing light detecting device. As the polarizing plate, a protective film is generally bonded to one side or both sides of a polarizing film by using an adhesive. In recent years, with the thinness of the liquid crystal display device, the thickness of the polarizing plate is also required.

A polarizing plate corresponding to the thinning of the polarizing plate, in which a protective film is bonded to only one side of the polarizing film, has been developed (Patent Document 1). In this polarizing plate, a pressure sensitive adhesive is directly attached to the surface of the polarizing film opposite to the protective film, and is laminated on a liquid crystal cell or the like on the pressure sensitive adhesive side. Though the polarizing plate is thinned, there is a problem that the polarizing plate is broken at the time of so-called rework, in which the pressure sensitive adhesive layer is peeled off from the liquid crystal cell.

Patent Document 1: JP-A-2001-194528

An object of the present invention is to provide a polarizing plate capable of peeling off a polarizing plate without causing breakage of the polarizing plate when the polarizing plate is detached from a liquid crystal display device to which the polarizing plate is applied.

The present invention includes the following.

[1] A polarizing plate comprising a polarizing film and a protective film,

Wherein the polarizing film has a thickness of 15 占 퐉 or less and a sticking strength per unit film thickness of 4.5 g / 占 퐉 or more,

Wherein the protective film has a breaking strength of 50 MPa or more.

[2] The protective film is at least one film selected from the group consisting of a cycloolefin resin film, a cellulose resin film, a polycarbonate resin film, a polyolefin resin film, a polyester resin film and an acrylic resin film , And the polarizer according to [1].

[3] The polarizing plate according to [1] or [2], wherein the protective film has an in-plane retardation value of 200 nm or less.

[4] The polarizing plate described in any one of [1] to [3], wherein the polarizing film has the protective film laminated on one side thereof and the optical layer laminated on the other side thereof.

[5] The polarizing plate according to [4], wherein the optical layer has a surface treatment layer on at least one side thereof.

[6] A polarizing plate comprising a polarizing plate according to any one of [1] to [5], wherein a pressure-sensitive adhesive layer is formed on the surface of the protective film,

The pressure-sensitive adhesive layer was prepared by cutting the polarizing plate to a width of 25 mm and a length of 150 mm, laminating it on a glass plate through a pressure-sensitive adhesive layer, / 25 mm or less.

[7] The liquid crystal display device according to [6], wherein a polarizing plate provided with a pressure-sensitive adhesive is laminated on at least one surface of a liquid crystal cell.

According to the present invention, in the process (rework process) in which the polarizing plate is peeled off at the interface between the pressure-sensitive adhesive layer or the adhesive layer and the liquid crystal cell after the polarizing plate is laminated on the liquid crystal cell with the pressure-sensitive adhesive layer or the adhesive layer, breakage in the polarizing plate is suppressed . Therefore, it is possible to prevent a rework failure (a small piece of the polarizing plate remaining on the surface of the liquid crystal cell) caused by the breakage of the polarizing plate, so that the liquid crystal cell can be reused.

1 is a schematic cross-sectional view showing a preferred configuration example of the liquid crystal display device of the present invention.
2 is a schematic diagram showing a method of measuring the peeling force of the pressure-sensitive adhesive layer.

[Polarizer]

1, the polarizing plate 1 of the present invention comprises a polarizing film 1 and a protective film 3. The polarizing film 1 has a thickness of 15 μm or less and a stiffness per unit film thickness of 4.5 gf / [Mu] m, and the breaking strength of the protective film 3 is 50 MPa or more. The polarizing film 1 may be laminated with another protective film (second protective film) 5 on the surface opposite to the bonding surface with the protective film 3. When the polarizing plate has a sticking strength per unit film thickness of less than 4.5 gf / 占 퐉, when the polarizing plate is bonded to an adherend such as glass with a pressure-sensitive adhesive layer or an adhesive layer, and then the polarizing plate is peeled from the adherend, The polarizing plate or the polarizing film tends to be broken. Further, even if the breaking strength of the protective film is less than 50 MPa, breakage tends to occur in the polarizing plate or the polarizing film in the same case.

(1) polarizing film

The polarizing film may be one in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin layer. When the thickness of the polarizing film is normally 20 m or less, the polarizing plate can be made thinner. In the present invention, a polarizing film having a thickness of 15 mu m or less is adopted, but the thickness of the polarizing film is preferably 8 mu m or less. Further, the thickness of the polarizing film is usually 2 占 퐉 or more.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. As the polyvinyl acetate resin, a copolymer of vinyl acetate and other monomers copolymerizable therewith may be mentioned in addition to polyvinyl acetate as a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

The degree of saponification of the polyvinyl alcohol resin may be in the range of 80 mol% or more, preferably 90 to 99.5 mol%, and more preferably 94 to 99 mol%. The polyvinyl alcohol-based resin may be a partially modified polyvinyl alcohol, and examples thereof include polyvinyl alcohol-based resins such as olefins such as ethylene and propylene; Unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid and an acrylamide. The average degree of polymerization of the polyvinyl alcohol-based resin is preferably 100 to 10,000, more preferably 1,500 to 8,000, and still more preferably 2,000 to 5,000.

The dichroic dye contained in the polarizing film (adsorption orientation) may be iodine or a dichroic organic dye, and conventionally known dyes may be used. The dichroic dye may be used alone, or two or more dichroic dyes may be used in combination.

In the present invention, it is important that the stiction intensity per unit film thickness when the thickness of the polarizing film is 15 占 퐉 or less and the polarizing film is cracked in the absorption axis direction is 4.5 gf / 占 퐉 or more. The sticking strength per unit film thickness can be increased by lowering the draw ratio at the time of producing the polarizing film. If the sticking strength per unit film thickness is less than 4.5 gf / 탆, the rate of occurrence of cracking of the polarizing film tends to increase, but the length of the generated crack tends to be long.

The polarizing plate has a high strength of the polarizing film itself by adopting a polarizing film having a sticking strength of 4.5 gf / 占 퐉 or more per unit film thickness, so that cracks can be suppressed even when a thin film has a minute defect. The sticking strength per unit film thickness is preferably 5.0 gf / 占 퐉 or more, more preferably 5.5 gf / 占 퐉 or more, and 7.0 gf / 占 퐉 or more. The upper limit is not particularly limited, but is preferably 15 gf / 占 퐉 or less and more preferably 10 gf / 占 퐉 or less in view of being able to impart favorable optical characteristics to the polarizer.

The sticking strength is determined by fixing the polarizing film to the jig and sticking it in the normal direction and measuring the strength when the polarizing film is cracked in the absorption axis direction. For example, the sticking strength can be measured by a compression tester equipped with a load cell. Examples of the compression tester include a handy compression tester "KES-G5 type " manufactured by KATO TECH CORPORATION; and a small table tester" EZ Test "manufactured by Shimadzu Seisakusho.

The measurement of the stuck strength is performed, for example, by sandwiching a polarizing film between two sample pores having circular holes each having a diameter of 15 mm or less through which the stuck jig can pass. The prick jig is preferably a columnar bar and has a prick needle having a spherical or hemispherical tip at its tip in contact with the polarizing film. Preferably, the spherical or hemispherical portion of the tip has a diameter of 0.5 mm or more and 5 mm or less, and the radius of curvature thereof is preferably larger than 0 R and smaller than 0.7 R. The piercing speed of the compression tester is preferably 0.05 cm / sec or more and 0.5 cm / sec or less.

The measurement of the stuck strength can be performed by fixing the test piece to the jig and piercing it in the normal direction to measure the strength when it is cracked in one place horizontally to the stretching direction (absorption axis direction). The measurement is carried out with respect to a test piece of five or more polarizing films, and the average value can be obtained as the striking strength. The stiction intensity per unit film thickness can be calculated by dividing the measured stiction intensity by the film thickness of the polarizing film used for the measurement. In this method, since the polarizing film can be quantitatively measured by pulling the polarizing film in the transmission axis direction and cracking in the absorption axis direction, it is possible to quantitatively measure the strength in the transmission axis direction, can do.

(2) Protective film

A protective film is laminated on at least one surface of the polarizing film. The protective film may be a transparent resin film composed of a thermoplastic resin. Examples of the thermoplastic resin include polyolefin-based resins such as a chain polyolefin-based resin and a cyclic polyolefin-based resin exemplified by polypropylene-based resins; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polyester resins such as polyethylene terephthalate, polyethylene naphthalate and polybutylene terephthalate; Polycarbonate resin; (Meth) acrylic resins; Or a mixture or copolymer thereof, and the like.

The cyclic polyolefin-based resin is generally a resin that is polymerized using cyclic olefins as polymerized units, and examples thereof include those described in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137 And resins described in, for example, JP-A-2004-346991. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically, random copolymers) of chain olefins such as ethylene and propylene with cyclic olefins, Graft polymers modified with carboxylic acids or their derivatives, and hydrides thereof. Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

Various products of cyclic polyolefin resin are commercially available. Examples of commercially available products of cyclic polyolefin resins are all trade names and are sold by TOPAS ADVANCED POLYMERS GmbH and sold by TOPAS (registered trademark) of JSR Corporation, which is commercially available from Polyplastics in Japan "Zeonoa" (registered trademark) and "Zeonex" (registered trademark) sold by Nippon Zeon Co., Ltd., "Artel" (registered trademark) sold by Mitsui Chemicals, Registered trademark).

Further, a commercially available product of the film-formed annular polyolefin-based resin film may be used as a protective film. Examples of commercially available products include all products sold under the names "ATHON FILM" ("Aton" is a registered trademark of the company) sold by JSR Kabushiki Kaisha, "ESHINA" sold by Sekisui Kagaku Kogyo Kogyo Co., "SCA40", "ZeonoAFIL" (registered trademark) sold by Nippon Zeon Co., Ltd., and the like.

Examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, they may be copolymerized with each other or a group in which a part of the hydroxyl group is modified with another substituent may be used. Of these, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate are all trade names and include Fujisac (registered trademark) TD80, Fujisac (registered trademark) TD80UF, Fujisan (registered trademark) TD80UZ "and" Fujisak (registered trademark) TD40UZ ", TAC films "KC8UX2M "," KC2UA ", and "KC4UY" manufactured by Konica Minolta K.K.

The protective film may be a film having an optical function such as a retardation film. The retardation film is given an arbitrary retardation value by, for example, stretching (uniaxially stretching or biaxially stretching) a transparent resin film or forming a liquid crystal layer or the like on a protective film. In this case, the in-plane retardation value of the protective film may be appropriately set in accordance with the type of the liquid crystal cell to be applied, and may be 200 nm or less, for example. The in-plane retardation value is preferably 150 nm or less, more preferably 100 nm or less, further preferably 50 nm or less. When the in-plane retardation value exceeds 200 nm, the uniaxial property of the film becomes strong, and the film tends to crack along the stretching direction.

In the protective film, the surface opposite to the polarizing film may be subjected to this adhesion treatment such as saponification treatment, corona treatment, primer treatment, anchor coating treatment and the like. These treatments can be carried out by known methods.

In the present invention, the breaking strength of the protective film provided with the pressure-sensitive adhesive layer for bonding to the liquid crystal cell is 50 MPa or more. The upper limit of the breaking strength is not particularly limited, but is usually 500 MPa or less, preferably 200 MPa or less, and more preferably 100 MPa or less.

In view of thinning of the polarizing plate, the thickness of the protective film is preferably as small as possible (for example, 30 탆 or less, preferably 20 탆 or less), but even in such a thin protective film, , The breaking strength per unit film thickness of the protective film is preferably 3.5 MPa / 탆 or more, more preferably 4.0 MPa / 탆 or more, and more preferably 5.0 MPa / 탆 or more. Although the upper limit is not particularly limited, the breaking strength per unit film thickness of the protective film is usually 15 MPa / 탆 or less, preferably 10 MPa / 탆 or less.

The polarizing film can be laminated on one side thereof with the protective film (first protective film) and another protective film (second protective film) laminated on the other side. In this case, as the second protective film, a resin film such as the first protective film may be used, or another optical layer may be laminated. When the second protective film is a resin film, the first protective film and the second protective film may be the same film or different films.

Examples of the optical layer constituting the second protective film include a front plate, a brightness enhancement film, and a curable resin layer. Examples of the front plate include glass and a glass substitution layer (plastic, resin cured product, and the like). Examples of the brightness enhancement film include an evaporated multilayer thin film having a different refractive index used for a multilayer thin film laminate of two or more layers or a beam splitter formed of two or more kinds of materials having a refractive index difference or a multilayer thin film of two or more birefringent layers A thin film laminate, and a laminate of two or more layers of a resin laminate using two or more resins having birefringence. Examples of the curable resin layer include a cured product of an active energy ray curable compound. The active energy ray-curable compound means a compound that can be cured by irradiation with active energy rays such as ultraviolet rays, visible light, electron beams, and X-rays. The active energy ray-curable compound may be a compound containing a cationic polymerizable compound, a compound containing a radical polymerizable compound, or a compound containing both of them.

It is preferable that the optical layer has a surface treatment layer on the surface opposite to the surface on which the polarizing film is laminated. Examples of the surface treatment layer include a surface treatment layer (coating layer) such as a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer and an antifouling layer.

Thickness of the first protective film and the second protective film is preferably thin from the viewpoint of thinning of the polarizing plate, but if it is too thin, the strength is lowered and the workability is poor. Therefore, the thickness of the first protective film and the second protective film is preferably 5 to 90 占 퐉 or less, more preferably 60 占 퐉 or less, further preferably 30 占 퐉 or less, particularly preferably 20 占 퐉 or less.

(3) Adhesive layer

The lamination of the polarizing film and the first protective film and the lamination of the polarizing film and the second protective film are performed through the adhesive layer or the pressure-sensitive adhesive layer, respectively. As the pressure-sensitive adhesive layer, there can be mentioned a pressure-sensitive adhesive layer such as a pressure-sensitive adhesive layer which will be described later and disposed on the polarizing plate to be bonded to the liquid crystal cell. The pressure-sensitive adhesive layer for laminating the protective film and the polarizing film and the pressure-sensitive adhesive layer to be described later disposed on the polarizing plate for bonding to the liquid crystal cell may be the same or different. Examples of the adhesive for forming the adhesive layer include an active energy ray curable adhesive that can be cured by irradiation with active energy rays such as ultraviolet rays, visible rays, electron beams, X-rays, etc., an adhesive agent dissolved in water, .

When an active energy ray-curable adhesive is employed, the adhesive layer becomes the cured layer. As the adhesive, an active energy ray curable adhesive containing an epoxy compound curable by cationic polymerization as a curable component is more preferable, and an ultraviolet curable adhesive containing an epoxy compound as a curable component is more preferable. The epoxy compound referred to herein means a compound having an average of at least one, preferably two or more epoxy groups in the molecule. The epoxy compound may be used alone, or two or more epoxy compounds may be used in combination.

Examples of suitable epoxy compounds include a hydrogenated epoxy compound obtained by reacting an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to a hydrogenation reaction with epichlorohydrin Cidyl ether); Aliphatic epoxy compounds such as aliphatic polyhydric alcohols or polyglycidyl ethers of alkylene oxide adducts thereof; And an alicyclic epoxy compound which is an epoxy compound having at least one epoxy group bonded to an alicyclic ring in the molecule.

The active energy ray-curable adhesive may further contain a (meth) acrylic compound that is a radical polymerization as a curable component. Examples of the (meth) acrylic compound include (meth) acrylate monomers having at least one (meth) acryloyloxy group in the molecule; (Meth) acryloyloxy group-containing compounds such as (meth) acrylate oligomers obtained by reacting two or more kinds of functional group-containing compounds and having at least two (meth) acryloyloxy groups in the molecule.

When the active energy ray-curable adhesive contains an epoxy compound curable by cationic polymerization as a curable component, it preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include aromatic diazonium salts; Onium salts such as aromatic iodonium salts and aromatic sulfonium salts; Iron-arene complexes and the like. When the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth) acrylic compound, it preferably contains a photo radical polymerization initiator. Examples of the photo radical polymerization initiator include an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, fluorenone, camphorquinone, benzaldehyde and anthraquinone.

The active energy ray curable adhesive may contain a cationic polymerization accelerator such as oxetane or polyol, a photosensitizer, an ion trapping agent, an antioxidant, a chain transfer agent, a tackifier, a thermoplastic resin, a filler, a flow regulator, , An antistatic agent, a leveling agent, a solvent, and the like.

The thickness of the adhesive layer formed of the active energy ray-curable adhesive is, for example, about 0.01 to 10 mu m, preferably about 0.01 to 5 mu m, more preferably 2 mu m or less (more preferably 1 mu m or less).

As the water-based adhesive, for example, an adhesive composition using a polyvinyl alcohol-based resin or a urethane resin as a main component is preferable. The thickness of the adhesive layer formed of the aqueous adhesive is usually 1 占 퐉 or less.

When a polyvinyl alcohol-based resin is used as the main component of the adhesive, the polyvinyl alcohol-based resin may be a partially saponificated polyvinyl alcohol, a fully saponified polyvinyl alcohol, a carboxyl group-modified polyvinyl alcohol, an acetoacetyl group-modified polyvinyl alcohol, Modified polyvinyl alcohol-based resins such as modified polyvinyl alcohol and amino group-modified polyvinyl alcohol. The polyvinyl alcohol-based resin may be a polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate which is a homopolymer of vinyl acetate. It may be combined.

The water-based adhesive containing a polyvinyl alcohol-based resin as an adhesive component is usually an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 5 parts by weight or less, based on 100 parts by weight of water.

In order to improve the adhesiveness, it is preferable to add a curing component such as a polyaldehyde, a melamine compound, a zirconia compound, a zinc compound, a glyoxal and a water-soluble epoxy resin, or a crosslinking agent to the adhesive composed of an aqueous solution of a polyvinyl alcohol- Do. Examples of the water-soluble epoxy resin include epoxy resins obtained by reacting epichlorohydrin with polyamide amines obtained by reacting polyalkylene polyamines such as diethylene triamine and triethylene tetramine with dicarboxylic acids such as adipic acid A polyamide polyamine epoxy resin can be suitably used. Examples of commercially available products of such polyamidepolyamine epoxy resins include "Sumirez Resin (registered trademark) 650" and "Sumirez Resin (registered trademark) 675" manufactured by Daoka Kagaku Kogyo K.K., manufactured by Seiko PMC Kabushiki Kaisha "WS-525" and the like. The amount of the curable component and the amount of the crosslinking agent (the total amount when the curable component and the crosslinking agent are added together) is usually 1 to 100 parts by weight, preferably 1 to 50 parts by weight, per 100 parts by weight of the polyvinyl alcohol resin . When the amount of the curable component or the crosslinking agent to be added is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol resin, the effect of improving the adhesiveness tends to be small. When the addition amount of the curable component or the cross- When the amount is more than 100 parts by weight based on 100 parts by weight of the resin, the adhesive layer tends to become fragile.

When a urethane resin is used as the main component of the adhesive, a mixture of a polyester-based ionomer-type urethane resin and a compound having a glycidyloxy group may be mentioned as an example of a suitable adhesive composition. The polyester-based ionomer-type urethane resin is a urethane resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced into the urethane resin. Such an ionomeric urethane resin is suitable as an aqueous adhesive since it emulsifies directly in water without using an emulsifier to form an emulsion.

[Polarizing plate production method]

The polarizing plate can be produced, for example, by the following method.

(A) A polyvinyl alcohol-based resin film having a polarizing performance as a polarizing film (hereinafter also referred to as a " polarizing film ") is used as a single-layer film and is made from a polyvinyl alcohol- Lt; / RTI >

[B] A coating solution containing a polyvinyl alcohol-based resin is coated on at least one surface of the base film to form a polyvinyl alcohol-based resin layer, and the resulting laminated film is subjected to a predetermined treatment to form a polyvinyl alcohol- The base layer is made to be a polarizing film, the protective film is bonded to the obtained polarizing laminated film, and then the base film is peeled off. In this method, after the base film is peeled off, a protective film may be bonded to the other side.

(Production method [a])

In the production method [a], a polarizing film can be produced from a polyvinyl alcohol-based resin film formed by film-forming the above-mentioned polyvinyl alcohol-based resin as a starting material. As a method for forming the polyvinyl alcohol-based resin, known methods such as melt extrusion method and solvent casting method may be employed. The thickness of the polyvinyl alcohol-based resin film before stretching is, for example, about 10 to 150 占 퐉.

The production method [a] includes, for example, a step of uniaxially stretching a polyvinyl alcohol-based resin film; Dyeing a polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye; Treating a polyvinyl alcohol-based resin film adsorbed with a dichroic dye with an aqueous solution of boric acid; And a step of washing with water after treatment with an aqueous boric acid solution.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing the dichroic dye. When uniaxial stretching is carried out after dyeing, the uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. In addition, uniaxial stretching may be carried out in a plurality of these steps.

The uniaxial stretching may be performed between rolls having different circumferential velocities, or may be performed using hot rolls. The uniaxial stretching may be a dry stretching in which stretching is performed in the atmosphere, or a wet stretching in which a polyvinyl alcohol based resin film is stretched by using a solvent. The stretching magnification is usually 3 to 17 times, preferably 4 times or more, and more preferably 8 times or less.

As a method for dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution (dyeing solution) containing a dichroic dye is employed. The polyvinyl alcohol-based resin film is preferably subjected to immersion treatment (swelling treatment) in water before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally employed. The content of iodine in the dyeing aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the dyeing aqueous solution is usually about 20 to 40 ° C. The time for dipping in the dyeing aqueous solution (dyeing time) is usually about 20 to 1800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of dying and dyeing a polyvinyl alcohol-based resin film into a dyeing aqueous solution containing a water-soluble dichroic organic dye is generally employed. The content of the dichroic organic dye in the dyeing aqueous solution is usually about 1 × 10 ^-4 to 10 parts by weight per 100 parts by weight of water and preferably about 1 × 10 ^-3 to 1 part by weight. The dyeing aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dyeing aqueous solution is usually about 20 to 80 ° C. The time for dipping in the dyeing aqueous solution (dyeing time) is usually about 10 to 1800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be carried out by immersing the dyed polyvinyl alcohol resin film in a boric acid solution.

The amount of boric acid in the aqueous solution of boric acid is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, it is preferable that the aqueous solution of boric acid contains potassium iodide. The amount of potassium iodide in the boric acid aqueous solution is usually about 0.1 to 15 parts by weight, preferably about 5 to 12 parts by weight, per 100 parts by weight of water. To the aqueous solution of boric acid, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid or the like may be added as a pH adjusting agent. The time for immersion in the boric acid aqueous solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, and more preferably about 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 占 폚 or higher, preferably 50 to 85 占 폚, and more preferably 60 to 80 占 폚.

The polyvinyl alcohol resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of the water in the water washing treatment is usually about 5 to 40 캜. The immersion time is usually about 1 to 120 seconds.

After washing with water, drying treatment is carried out to obtain a polarizing film. The drying treatment can be carried out using a hot-air dryer or a far-infrared heater. The temperature of the drying treatment is usually about 30 to 100 캜, preferably 50 to 80 캜. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

By the drying treatment, the water content of the polarizing film is reduced to the practical level. The water content thereof is usually 5 to 20% by weight, preferably 8 to 15% by weight. If the water content is less than 5% by weight, flexibility of the polarizing film may be lost, and the polarizing film may be damaged or broken after drying. If the water content exceeds 20% by weight, the thermal stability of the polarizing film may be poor.

The first protective film is bonded to at least one surface of the polarizing film using an adhesive and the adhesive is cured to produce a polarizing plate. If necessary, the second protective film may be bonded to the other surface of the polarizing film.

As a method for bonding a first protective film and a second protective film to a polarizing film using an active energy ray curable adhesive or an aqueous adhesive, an adhesive is applied to one or both of the bonding surfaces of the two films to be bonded, For example, a method in which two films are polymerized through a film. The coating of the adhesive can be carried out by, for example, a softening method, a Meyer bar coating method, a gravure coating method, a comma coater method, a doctor blade method, a die coating method, a dip coating method or a spraying method. The casting method is a method in which a film to be joined is moved in a substantially vertical direction, in a substantially horizontal direction, or in an oblique direction between the two, while causing an adhesive to flow on the surface of the film to be spread. The film laminate obtained by polymerizing through the adhesive layer is usually pressed up and down through a nip roll (bonding roll) or the like.

In the bonding of the protective film to the polarizing film, a bonding surface of the protective film and / or the polarizing film is preferably provided with a surface treatment such as plasma treatment, corona treatment, ultraviolet ray irradiation treatment, flame treatment and saponification treatment It is preferable to carry out a plasma treatment, a corona treatment or a saponification treatment. For example, in the case where the protective film is made of a cyclic polyolefin-based resin, a plasma treatment or a corona treatment is generally performed on the bonding surface of the protective film. When the protective film is made of a cellulose ester resin, the bonding surface of the protective film is usually saponified. As the saponification treatment, a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide can be mentioned.

When an aqueous adhesive is used, it is preferable to carry out a drying step of drying the film laminate in order to remove water contained in the adhesive layer made of an aqueous adhesive after bonding the above-mentioned films. Drying can be carried out, for example, by introducing a film laminate into a drying furnace. The drying temperature (temperature of the drying furnace) is preferably 30 to 90 占 폚. If it is less than 30 DEG C, the protective film tends to be easily peeled off from the polarizing film. If the drying temperature exceeds 90 DEG C, there is a fear that the polarization performance of the polarizing film is deteriorated by heat. The drying time can be set to about 10 to 1000 seconds, and from the viewpoint of productivity, it is preferably 60 to 750 seconds, and more preferably 150 to 600 seconds.

After the drying step, the polarizing plate may be cured at room temperature or slightly higher temperature, for example, at a temperature of about 20 to 45 ° C for about 12 to 600 hours. The curing temperature is generally set to be lower than the drying temperature.

In the case of using an active energy ray-curable adhesive, the above-mentioned film is bonded, and then a curing step of curing the adhesive layer made of the active energy ray-curable adhesive is performed. The curing of the adhesive layer can be performed by irradiating an active energy ray to the film laminate. The active energy ray is usually irradiated on the first protective film side. The active energy ray is preferably ultraviolet radiation.

A light source of an active energy ray is not particularly limited, but an active energy ray having a light emission distribution at a wavelength of 400 nm or less is preferable. Specifically, a low energy mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, Mercury lamp, metal halide lamp and the like are preferably used.

The irradiation intensity of the active energy ray on the adhesive layer made of the active energy ray curable adhesive is appropriately determined according to the composition of the adhesive but is set so that the irradiation intensity in the wavelength range effective for activation of the polymerization initiator is 0.1 to 6000 mW / . Heat and active energy radiated from the light source when the irradiation intensity is not more than 6000 mW / cm 2 when the irradiation intensity is not less than 0.1 mW / cm 2 and the reaction time is not excessively long. The yellowing or polarization of the adhesive layer due to heat generation during curing of the adhesive There is little possibility of causing deterioration of the film.

The irradiation time of the active energy ray is preferably determined in accordance with the composition of the adhesive but is preferably set so that the integrated amount of light represented by the irradiation intensity and irradiation time is 10 to 10000 mJ / cm 2. When the accumulated light quantity is 10 mJ / cm 2 or more, a sufficient amount of active species originating from the polymerization initiator can be sufficiently generated to allow the curing reaction to proceed more surely. When the total light quantity is 10,000 mJ / cm 2 or less, the irradiation time is not excessively long, .

It is preferable that the active energy ray is irradiated under such a condition that all functions of the polarizing plate such as the degree of polarization, transmittance and hue of the polarizing film, and transparency of the protective film are not deteriorated.

In lamination of the first protective film and the second protective film with respect to the polarizing film, either one of the protective films may be laminated on the polarizing film, and then the other protective film may be laminated. Alternatively, May be laminated on the polarizing film at the same time.

(Production method [b])

In the production method [b], a polyvinyl alcohol-based resin layer to be a polarizing film can be formed by coating a base film with a polyvinyl alcohol-based resin. For example, a resin layer forming step, a stretching step, a dyeing step, A polarizing film can be produced through a process and a peeling process. As an example of the production method [b], the method described in Patent Document 1 can be mentioned.

In the case of laminating the second protective film on the other surface of the polarizing film, a second bonding step of bonding the second protective film to the other surface of the polarizing film may be performed after the peeling step. On the other hand, when the protective film is laminated on both surfaces, the second protective film may be laminated in the first bonding step and the first protective film may be laminated in the second bonding step.

(Resin layer forming step)

In this step, a coating solution containing a polyvinyl alcohol-based resin is coated on at least one surface of a base film and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film. The polyvinyl alcohol-based resin layer is a layer that becomes a polarizing film after being subjected to a drawing process and a dyeing process. The polyvinyl alcohol-based resin layer can be formed by coating a coating liquid containing a polyvinyl alcohol-based resin on one side or both sides of a base film and drying the coating layer. The method of forming the polyvinyl alcohol-based resin layer by such coating is advantageous in that it is easy to obtain a polarizing film of a thin film.

The base film may be composed of a thermoplastic resin, and it is preferable that the base film is made of a thermoplastic resin having excellent transparency, mechanical strength, thermal stability, stretchability and the like. Specific examples of such a thermoplastic resin include polyolefin-based resins such as a chain polyolefin-based resin and a cyclic polyolefin-based resin; Polyester-based resin; (Meth) acrylic resins; Cellulose ester-based resins such as cellulose triacetate and cellulose diacetate; Polycarbonate resin; Polyvinyl alcohol-based resin; Polyvinyl acetate resin; Polyarylate resins; Polystyrene type resin; Polyether sulfone type resin; Polysulfone resins; Polyamide based resin; Polyimide resin; And mixtures and copolymers thereof.

The base film may be a single layer structure composed of one resin layer made of one kind or two or more kinds of thermoplastic resins, or a multilayer structure in which a plurality of resin layers made of one kind or two or more kinds of thermoplastic resins are laminated.

Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins. A base film composed of a chain polyolefin-based resin is preferable because it is easy to stably stretch at a high magnification. Among them, the base film is preferably made of a polypropylene resin (a polypropylene resin which is a homopolymer of propylene or a copolymer mainly composed of propylene), a polyethylene resin (a polyethylene resin which is a homopolymer of ethylene or a copolymer mainly comprising ethylene ) Is more preferable.

A copolymer mainly composed of propylene, which is one of examples suitably used as a thermoplastic resin constituting the base film, is a copolymer of propylene and other monomers copolymerizable therewith. Examples of other monomers copolymerizable with propylene include ethylene and? -Olefin. As the? -olefin, an? -olefin having 4 or more carbon atoms is preferably used, and an? -olefin having 4 to 10 carbon atoms is more preferable. Examples of the? -Olefin having 4 to 10 carbon atoms include straight chain monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; Vinylcyclohexane and the like. The copolymer of propylene and other monomer copolymerizable therewith may be a random copolymer or a block copolymer.

The content of other monomers is, for example, 0.1 to 20% by weight, preferably 0.5 to 10% by weight, in the copolymer. The content of the other monomers in the copolymer can be determined by infrared (IR) spectrum measurement according to the method described in "Polymer Analysis Handbook" (1995, published by Kinokuniya Shoten), page 616.

Of the above, propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer or propylene-ethylene-1-butene random copolymer are preferably used as the polypropylene type resin.

The stereoregularity of the polypropylene resin is preferably substantially isotactic or syndiotactic. A base film made of a polypropylene resin having substantially isotactic or syndiotactic stereoregularity is relatively easy to handle and has excellent mechanical strength under a high temperature environment.

The polyester-based resin is a resin having an ester bond, and is generally composed of a polycondensation product of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polycarboxylic acid or its derivative, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethylterephthalate, dimethyl naphthalenedicarboxylate and the like. As the polyhydric alcohol, a dihydric diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

As a representative example of the polyester-based resin, polyethylene terephthalate which is a polycondensation product of terephthalic acid and ethylene glycol can be mentioned. Polyethylene terephthalate is a crystalline resin, but it is easy to carry out processing such as stretching in a state before crystallization treatment. If necessary, the crystallization treatment can be performed by stretching or after heat treatment after stretching. In addition, copolymerized polyesters having reduced crystallinity (or made amorphous) by copolymerizing monomers of other species in addition to the skeleton of polyethylene terephthalate are also suitably used. Examples of such resins include copolymers obtained by copolymerizing cyclohexane dimethanol or isophthalic acid. These resins are also excellent in stretchability and therefore can be suitably used.

Specific examples of the polyester resin other than the polyethylene terephthalate and the copolymer thereof include polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, Hexanedimethyl terephthalate, polycyclohexanedimethanol naphthalate, and mixtures and copolymers thereof.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Examples of the (meth) acrylic resin include poly (meth) acrylic acid esters such as polymethyl methacrylate; Methyl methacrylate- (meth) acrylic acid copolymer; Methyl methacrylate- (meth) acrylic acid ester copolymer; Methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.) . As the (meth) acrylic resin, a polymer mainly composed of a poly (meth) acrylic acid alkyl ester having 1 to 6 carbon atoms in the alkyl group is preferable, and methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100 By weight) is more preferable.

The polycarbonate resin is an engineering plastic composed of a polymer having a monomer unit bonded thereto through a carbonate group, and is a resin having high impact resistance, heat resistance, flame retardancy and transparency. The polycarbonate resin may be a resin called a modified polycarbonate such as a polymer skeleton modified to lower the photoelastic coefficient, or a copolymerized polycarbonate improved in wavelength dependency. Suitable commercially available products can be used for the polycarbonate resin. Examples of commercially available products include all products such as "Panlight (registered trademark) " manufactured by Dejing Chemical Co., Ltd.," Yuplon (registered trademark) " manufactured by Mitsubishi Engineering Plastics Corporation, and Sumikastarite Polycarbonate SD Polycar (registered trademark) "manufactured by Nippon Synthetic Chemical Industry Co., Ltd., and" Kaliba (registered trademark) "manufactured by Dow Chemical Company.

Of these, a polypropylene resin is preferably used from the viewpoint of stretchability and heat resistance.

As to the cyclic polyolefin-based resin and the cellulose ester-based resin to be used as the base film, matters described in relation to the protective film are cited. The chain polyolefin resin, polyester resin, (meth) acrylic resin and polycarbonate resin described above in relation to the base film can also be used as a constituent material of the protective film.

In addition to the thermoplastic resin, any appropriate additives may be added to the base film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a releasing agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment and a colorant.

The thickness of the base film can be suitably determined, but is generally from 1 to 500 탆, more preferably 300 탆 or less, further preferably 200 탆 or less from the viewpoint of workability such as strength and handling properties, 150 [mu] m is most preferable.

The tensile elastic modulus of the base film is preferably 100 MPa to 1500 MPa at 80 캜, more preferably 140 MPa to 1000 MPa, and even more preferably 150 MPa to 500 MPa. When the tensile modulus is too small, the hardness of the base film is not sufficient at the time of stretching, and defects such as wrinkles are likely to occur. When the tensile modulus is too high, the workability in stretching is deteriorated.

The coating liquid containing the polyvinyl alcohol-based resin to be coated on the base film is preferably a polyvinyl alcohol-based resin solution obtained by dissolving a polyvinyl alcohol-based resin powder in a good solvent (for example, water). The coating liquid may contain an additive such as a plasticizer and a surfactant if necessary. As the plasticizer, a polyol or a condensate thereof can be used. Examples of the plasticizer include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The blending amount of the additive is preferably 20% by weight or less of the polyvinyl alcohol-based resin.

The method of applying the coating liquid on the base film may be a wire bar coating method; A roll coating method such as reverse coating and gravure coating; Die coating method; Comma coat method; Lip coating method; Spin coating method; Screen coating method; Fountain coating method; Dipping method; Spraying method, and the like. When the coating solution is coated on both surfaces of the base film, it is possible to coat the base film on the both surfaces of the base film at the same time by using the above-described method in sequence or by using a dipping method, a spray coating method or other special apparatus It is possible.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set according to the type of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 2 to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed on only one side of the base film or on both sides. It is possible to suppress the curling of the film which may occur in the production of the polarizing laminated film and to obtain two polarizing plates from one polarizing laminated film and therefore it is also advantageous in terms of production efficiency of the polarizing plate .

The thickness of the polyvinyl alcohol-based resin layer in the laminated film is preferably 3 to 60 占 퐉, more preferably 3 to 30 占 퐉, and still more preferably 5 to 20 占 퐉. Within this range, a polarizing film having good dyability of the dichroic dye and excellent in polarization performance and having a sufficiently small thickness can be obtained. If the thickness of the polyvinyl alcohol-based resin layer exceeds 60 탆, the thickness of the polarizing film may exceed 20 탆, and if the thickness of the polyvinyl alcohol-based resin layer is less than 3 탆, the film becomes too thin after stretching to deteriorate the dyeability There is a tendency.

In order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer prior to coating of the coating liquid, at least the surface of the base film on which the polyvinyl alcohol-based resin layer is formed is subjected to corona treatment, plasma treatment, Flame) treatment may be performed.

In addition, in order to improve adhesion between the base film and the polyvinyl alcohol-based resin layer prior to coating of the coating liquid, a polyvinyl alcohol-based resin layer may be formed on the base film through a primer layer or an adhesive layer.

The primer layer can be formed by coating a coating solution for forming a primer layer on the surface of a base film, followed by drying. The coating solution for forming a primer layer preferably includes a component exhibiting a strong adhesion to some extent to both the base film and the polyvinyl alcohol-based resin layer. The coating solution for forming a primer layer usually contains such a resin component and a solvent. As the resin component, a thermoplastic resin excellent in transparency, thermal stability, stretchability and the like is used, and examples thereof include a (meth) acrylic resin and a polyvinyl alcohol resin. Among them, a polyvinyl alcohol-based resin which gives good adhesion is preferably used.

Examples of the polyvinyl alcohol-based resin include a polyvinyl alcohol resin and derivatives thereof. As the derivative of the polyvinyl alcohol resin, polyvinyl formal, polyvinyl acetal, etc., polyvinyl alcohol resins modified with olefins such as ethylene and propylene; Modified with an unsaturated carboxylic acid such as acrylic acid, methacrylic acid and crotonic acid; An alkyl ester of an unsaturated carboxylic acid; Acrylamide, and the like. Of the polyvinyl alcohol-based resins described above, polyvinyl alcohol resins are preferably used.

As the solvent, a general organic solvent or an aqueous solvent capable of dissolving the resin component is usually used. Examples of the solvent include aromatic hydrocarbons such as benzene, toluene and xylene; Ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; Esters such as ethyl acetate and isobutyl acetate; Chlorinated hydrocarbons such as methylene chloride, trichlorethylene and chloroform; Ethanol, 1-propanol, 2-propanol and 1-butanol. However, when a primer layer is formed using a coating solution for forming a primer layer containing an organic solvent, the base film may be dissolved, so it is preferable to select a solvent in consideration of the solubility of the base film. Considering the environmental impact, it is preferable to form the primer layer with a coating solution containing water as a solvent.

As the coating solution for forming the primer layer, a crosslinking agent may be added to increase the strength of the primer layer. As the crosslinking agent, an appropriate one among known ones such as an organic type and an inorganic type is appropriately selected depending on the kind of the thermoplastic resin to be used. Examples of the crosslinking agent include epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agents.

As the epoxy cross-linking agent, any one of a one-liquid curing type and a two-liquid curing type may be used, and examples thereof include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di- or tri- glycidyl ether, Diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl amine and the like.

Examples of the isocyanate cross-linking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane-tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane) triisocyanate, isophorone diisocyanate, Block water or phenol block water.

Examples of the dialdehyde-based crosslinking agent include glyoxal, malondialdehyde, succindialdehyde, glutarialdehyde, maleindialdehyde, phthalaldehyde and the like.

Examples of the metal-based cross-linking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. Examples of the metal salt, metal oxide and metal hydroxide include salts of metals having a valence of 2 or more such as magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, silicon, boron, zinc, copper, vanadium, chromium, Oxides and hydroxides.

The organometallic compound is a compound having at least one structure in which an organic group is directly bonded to a metal atom or an organic group is bonded through an oxygen atom or a nitrogen atom. The organic group means a monovalent or multivalent group containing at least a carbon element, and may be, for example, an alkyl group, an alkoxy group, an acyl group, or the like. The term " bond " means not only a covalent bond but also a coordination bond by coordination with a chelate-type compound.

Suitable examples of the organometallic compound include an organic titanium compound, an organic zirconium compound, an organoaluminum compound, and an organosilicon compound. The organometallic compound may be used alone, or two or more of them may be used in combination.

Examples of the organic titanium compound include titanium ortho esters such as tetra n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetra (2-ethylhexyl) titanate and tetramethyl titanate; Titanium chelates such as titanium acetylacetonate, titanium tetraacetylacetonate, polytitanacetylacetonate, titanium octylene glycolate, titanium lactate, titanium triethanolamine and titanium ethylacetoacetate; And titanium acylate such as polyhydroxy titanium stearate.

Examples of the organic zirconium compound include zirconium n-propionate, zirconium n-butyrate, zirconium tetraacetylacetonate, zirconium monoacetylacetonate, zirconium bisacetylacetonate, and zirconium acetylacetonate isobutylacetoacetate.

Examples of the organoaluminum compound include aluminum acetylacetonate and aluminum organic acid chelate. As the organosilicon compound, for example, there can be mentioned a compound in which the ligand exemplified above in the organic titanium compound and organic zirconium compound is bonded to silicon.

In addition to the above crosslinking agent (low molecular weight crosslinking agent), a high molecular weight crosslinking agent such as methylol melamine resin and polyamide epoxy resin may also be used. Examples of commercially available products of polyamide epoxy resin include "Sumirez Resin (registered trademark) 650 (30)" and "Sumirez Resin (registered trademark)" sold by Daoka Kagaku Kogyo K.K. under trade names, 675 ".

When the primer layer is formed of a polyvinyl alcohol-based resin, a polyamide epoxy resin, a methylol melamine resin, a dialdehyde-based cross-linking agent, a metal chelate-based cross-linking agent and the like are suitably used as a cross-linking agent.

The ratio of the resin component and the crosslinking agent in the coating liquid for forming the primer layer may be appropriately determined in accordance with the kind of the resin component and the kind of the crosslinking agent, etc. in the range of about 0.1 to 100 parts by weight of the crosslinking agent per 100 parts by weight of the resin component, Particularly preferably about 0.1 to 50 parts by weight. The coating solution for forming a primer layer preferably has a solid concentration of about 1 to 25% by weight.

The thickness of the primer layer is preferably about 0.05 to 1 mu m, more preferably 0.1 to 0.4 mu m. If the thickness is smaller than 0.05 占 퐉, the effect of improving adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and if it is thicker than 1 占 퐉, it is disadvantageous for making the polarizing plate thinner.

The method of coating the primer layer-forming coating solution onto the base film may be the same as the coating solution for forming the polyvinyl alcohol-based resin layer. The primer layer is applied to the surface (one surface or both surfaces of the base film) onto which the coating solution for forming the polyvinyl alcohol-based resin layer is coated. The drying temperature and the drying time of the coating layer composed of the coating solution for forming the primer layer are set according to the type of the solvent contained in the coating solution. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. When the solvent includes water, the drying temperature is preferably 80 DEG C or higher. The drying time is, for example, 30 seconds to 20 minutes.

When a primer layer is provided, the order of coating on the base film is not particularly limited. For example, in the case of forming a polyvinyl alcohol-based resin layer on both surfaces of a base film, a primer layer is formed on both surfaces of the base film, A polyvinyl alcohol resin layer may be formed on both sides of the base film, and a primer layer and a polyvinyl alcohol-based resin layer may be sequentially formed on one side of the base film, and then a primer layer, a polyvinyl alcohol- And resin layers may be sequentially formed.

(Drawing step)

The present step is a step of obtaining a stretched film comprising a stretched base material film and a polyvinyl alcohol-based resin layer by subjecting a laminated film comprising a base film and a polyvinyl alcohol-based resin layer to stretching treatment. The stretching magnification of the laminated film can be appropriately selected according to the desired polarization characteristics, but it is preferably more than 4 times and not more than 17 times, more preferably more than 4 times and not more than 8 times the original length of the laminated film . If the stretching magnification is 4 times or less, the polyvinyl alcohol-based resin layer is not sufficiently oriented, so that the degree of polarization of the polarizing film may not be sufficiently increased. On the other hand, when the stretching magnification exceeds 17 times, the film tends to break at the time of stretching, and the thickness of the stretched film becomes thin more than necessary, which may lower the workability and handling property in the subsequent step. The stretching treatment is usually uniaxial stretching.

The stretching treatment is not limited to stretching in one stage but may be carried out in multiple stages. In this case, all of the multi-stage drawing process may be performed continuously before the dyeing process, and the drawing process after the second step may be performed simultaneously with the dyeing process and / or the crosslinking process in the dyeing process. In such a multi-stage stretching treatment, it is preferable to perform the stretching treatment so that the entire stages of the stretching treatment are combined so as to have a stretching magnification of more than 4 times.

The stretching treatment may be longitudinal stretching in which stretching is performed in the longitudinal direction of the film (film transport direction), or transverse stretching or warp stretching in stretching in the film width direction. Examples of the longitudinal stretching method include roll-to-roll stretching using a roll, compression stretching, and stretching using a chuck. The transverse stretching method includes a tenter method and the like. Any of the wet drawing method and the dry drawing method can be employed for the drawing treatment, but a dry drawing method is preferable because the drawing temperature can be selected in a wide range.

The stretching temperature is set at a temperature higher than the temperature at which the entire polyvinyl alcohol resin layer and the substrate film can be stretched to exhibit fluidity and is preferably set to a temperature of -30 ° C to + 30 ° C (melting point or glass transition temperature) More preferably in the range of -30 ° C to + 5 ° C, and more preferably in the range of -25 ° C to + 0 ° C. When the base film is composed of a plurality of resin layers, the phase transition temperature means the highest phase transition temperature among the phase transition temperatures of the plurality of resin layers.

When the stretching temperature is lower than -30 캜 of the phase transition temperature, high-magnification stretching exceeding 4 times is difficult to achieve, or the fluidity of the base film is too low to make the stretching process difficult. If the stretching temperature exceeds + 30 ° C of the phase transition temperature, the fluidity of the base film becomes too high, and the stretching tends to be difficult. The stretching temperature is within the above-mentioned range, and more preferably 120 DEG C or more because it is easy to draw at a high magnification rate exceeding 4 times. When the stretching temperature is 120 占 폚 or more, it is not accompanied by difficulty in the stretching treatment even at a high magnification elongation exceeding 4 times.

The stretching treatment may be carried out while heating the laminated film. Examples of the heating method include a zone heating method (for example, heating in a drawing zone such as a heating furnace heated to a predetermined temperature by blowing hot air); A method of heating the roll itself when the roll is stretched; A heater heating method (a method in which an infrared heater, a halogen heater, a panel heater, or the like is placed on the top and bottom of a laminated film and heated by radiant heat). In the roll-to-roll stretching method, the zone heating method is preferable from the viewpoint of the uniformity of the stretching temperature. In this case, the two nip roll pairs may be provided in a temperature-controlled stretching zone or outside the stretching zone, but it is preferable that they are provided outside the stretching zone to prevent adhesion between the laminated film and the nip roll.

On the other hand, the stretching temperature means the atmospheric temperature in the zone (for example, inside the heating furnace) in the case of the zone heating method and the atmospheric temperature inside the furnace in the case of heating in the furnace. In the case of the method of heating the roll itself, it means the surface temperature of the roll.

Prior to the stretching process, a preheating process for preheating the laminated film may be performed. As the preheating method, the same method as the heating method in the stretching treatment can be used. In the case where the stretching treatment method is roll-to-roll stretching, the preheating may be performed at any timing before passing through the nip roll on the upstream side, during passing, or after passing. When the stretching treatment is a thermal roll stretching, preheating is preferably carried out at a timing before passing the hot roll. In the case of the stretching process using a chuck, preheating is preferably performed at a timing before widening the chuck distance. The preheating temperature is preferably in the range of -50 占 폚 to 占 0 占 폚 of the stretching temperature, and more preferably in the range of -40 占 폚 to -10 占 폚 of the stretching temperature.

In addition, after the stretching process in the stretching process, a heat fixing process may be performed. The heat-setting treatment is a process of heat-treating the end portion of the stretched film at a crystallization temperature or higher, while keeping the end portion of the stretched film in a state of being held by a clip. By the heat-setting treatment, the crystallization of the polyvinyl alcohol-based resin layer is promoted. The heat-setting treatment temperature is preferably in the range of -0 to -80 占 폚 of the stretching temperature, and more preferably in the range of -0 to -50 占 폚 of the stretching temperature.

(Dyeing process)

This step is a step of obtaining a polarizing laminated film by dyeing a polyvinyl alcohol-based resin layer of a stretched film with a dichroic dye and forming a polarizing film by adsorbing and orienting the dye. Through this step, a polarizing laminated film in which a polarizing film is laminated on one side or both sides of a base film can be obtained. The dyeing step can be carried out by immersing the entire stretched film in a solution (dyeing solution) containing a dichroic dye. As the dyeing solution, a solution obtained by dissolving the dichroic dye in a solvent can be used. As the solvent of the dyeing solution, water is generally used, but an organic solvent having compatibility with water may be further added. The concentration of the dichroic dye in the dyeing solution is preferably 0.01 to 10% by weight, more preferably 0.02 to 7% by weight, and still more preferably 0.025 to 5% by weight.

When iodine is used as the dichroic dye, the dyeing efficiency can be further improved, so it is preferable to add iodide to the dyeing solution containing iodine. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The concentration of iodide in the dyeing solution is preferably 0.01 to 20% by weight. It is preferable to add potassium iodide even in iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably 1: 6 to 1:80, 7 to 1: 70.

The time for immersing the stretched film in the dyeing solution is usually in the range of 15 seconds to 15 minutes, preferably 30 seconds to 3 minutes. The temperature of the dyeing solution is preferably in the range of 10 to 60 ° C, more preferably 20 to 40 ° C.

On the other hand, the stretched film may be subjected to further stretching treatment during the dyeing step. As an embodiment of this case, 1) an embodiment in which the stretching process is performed such that 1) the stretching process is performed at a lower magnification than the target, and then the total stretching ratio becomes the target magnification during the staining process in the staining process; In the case of performing the crosslinking treatment after the dyeing treatment, 2) the stretching step is carried out at a lower magnification than the target in the drawing step, and the total drawing magnification does not reach the target magnification during the dyeing processing in the dyeing step And then the stretching process is performed during the crosslinking process so that the final total stretching ratio becomes the target multiplication ratio.

The dyeing process may include a crosslinking process performed after the dyeing process. The crosslinking treatment can be carried out by immersing the dyed film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known materials can be used, and examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

Specifically, the crosslinking solution may be a solution in which a crosslinking agent is dissolved in a solvent. As the solvent, for example, water may be used, but an organic solvent having compatibility with water may be further included. The concentration of the crosslinking agent in the crosslinking solution is preferably in the range of 1 to 20% by weight, and more preferably in the range of 6 to 15% by weight.

The crosslinking solution may comprise iodide. By adding iodide, the polarization performance in the plane of the polarizing film can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide and titanium iodide. The concentration of iodide in the crosslinking solution is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

Further, the crosslinking solution may contain other components such as a pH adjusting agent. As the pH adjuster, for example, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid and the like may be added.

The time for immersing the dyed film in the crosslinking solution is usually 15 seconds to 20 minutes, preferably 30 seconds to 15 minutes. The temperature of the crosslinking solution is preferably in the range of 10 to 90 占 폚.

On the other hand, the crosslinking treatment may be carried out simultaneously with the dyeing treatment by blending the crosslinking agent into the dyeing solution. The stretching treatment may be performed during the crosslinking treatment. The specific embodiment in which the stretching treatment is carried out during the crosslinking treatment is as described above.

After the dyeing step, it is preferable to carry out a cleaning step and a drying step before the first bonding step to be described later. The cleaning process usually includes a water cleaning process. The water washing treatment can be carried out by immersing the film after the dyeing treatment or after the crosslinking treatment in purified water such as ion-exchanged water and distilled water. The water washing temperature is usually in the range of 3 to 50 캜, preferably 4 to 20 캜. The immersion time is usually from 2 to 300 seconds, preferably from 3 to 240 seconds.

The cleaning step may be a combination of a water cleaning step and a cleaning step with an iodide solution. The washing liquid used in the water washing step and / or the washing treatment with the iodide solution may suitably contain, in addition to water, a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol and propanol.

As the drying step performed after the cleaning step, any suitable method such as natural drying, air blow drying, and heat drying can be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95 ° C, and the drying time is usually about 1 to 15 minutes.

(First bonding step)

This step is a step of obtaining a bonded film by bonding a first protective film on a polarizing film of a polarizing laminated film, that is, a surface of the polarizing film opposite to the base film side with an adhesive. When the polarizing laminated film has a polarizing film on both sides of the base film, the protective film is usually bonded onto the polarizing film on both sides. In this case, these protective films may be the same kind of protective film or different kinds of protective films.

(Peeling process)

In this step, the base film is peeled off from the bonding film obtained by bonding the first protective film to obtain a polarizing plate having a one-side protective film. Through this process, it is possible to obtain a polarizing plate having a one-side protective film in which the first protective film is laminated on one side of the polarizing film. When the polarizing laminated film has polarizing films on both sides of the base film and a protective film is bonded to both polarizing films, the one polarizing laminated film has two one-side protective films A polarizing plate can be obtained.

The method of peeling off the base film can be peeled off in the same manner as the peeling process of a separator (peeling film) which is performed in a polarizing plate having a usual pressure-sensitive adhesive. The base film may be peeled off immediately after the first bonding step, or may be rolled up once in the form of a roll after the first bonding step and peeled off in the subsequent step.

(Second bonding step)

In this step, a polarizing plate is obtained by bonding another protective film on the polarizing film of the polarizing plate having the one surface protective film, that is, the surface opposite to the protective film bonded in the first joining step, through an adhesive or a pressure- Process. In the case of carrying out the second bonding step, the second protective film may be bonded in the first bonding step, and in this case, the first protective film is bonded in this step.

[Polarizing plate with pressure-sensitive adhesive]

The polarizing plate may be a pressure-sensitive adhesive layer or a pressure-sensitive adhesive layer (for example, a pressure-sensitive adhesive layer or a pressure-sensitive adhesive layer) on the surface of the protective film having a breaking strength of 50 MPa or more, opposite to the surface on which the polarizing films are laminated To an adherend such as a liquid crystal cell. That is, it is preferable that the polarizing plate is bonded to the liquid crystal cell such that the order of lamination is a liquid crystal cell / pressure-sensitive adhesive layer or a protective film / polarizing film having an adhesive layer / breaking strength of 50 MPa or more. As the pressure-sensitive adhesive or adhesive for forming the pressure-sensitive adhesive layer or the adhesive layer, any known one can be suitably used, but it is preferable to use a pressure-sensitive adhesive from the viewpoint of reworkability.

Examples of the pressure-sensitive adhesive include acrylic pressure-sensitive adhesives, silicone pressure-sensitive adhesives, and rubber pressure-sensitive adhesives. From the viewpoints of transparency, weather resistance, heat resistance and workability, acrylic pressure-sensitive adhesives are preferable. Various additives such as a filler, a pigment, a colorant, a filler, an antioxidant, an ultraviolet absorber, and a silane coupling agent, which are composed of a tackifier, a plasticizer, a glass fiber, a glass bead, a metal powder and other inorganic powders, May be appropriately blended.

The pressure-sensitive adhesive is applied on a suitable substrate and dried to form a pressure-sensitive adhesive layer. This substrate is generally a plastic film, and a typical example thereof is a release film subjected to release treatment. The release film may be a film formed of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyalate, etc., in which a release agent such as silicone treatment is applied to the surface on which the pressure-sensitive adhesive is formed . The application of the pressure-sensitive adhesive may be carried out by, for example, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method and a spraying method.

The formation of the pressure-sensitive adhesive layer on the protective film can be carried out by a known method such as a method of transferring a release sheet provided with a pressure-sensitive adhesive layer. The thickness of the pressure-sensitive adhesive layer is usually about 3 to 100 占 퐉, preferably 5 to 50 占 퐉.

(Peeling force of the pressure-sensitive adhesive layer)

The pressure-sensitive adhesive layer preferably has a peel force of 180 N / 25 mm or less when subjected to a 180 ° peel test. When the peeling force exceeds 10 N / 25 mm, the polarizing plate tends to be broken when the polarizing plate provided with a pressure-sensitive adhesive is peeled from the adherend for each of the pressure-sensitive adhesive layers after the polarizing plate provided with the pressure-sensitive adhesive is bonded to the adherend. The peel force is preferably 5 N / 25 mm or more, more preferably 7 N / 25 mm or more. When the peel force is 5 N / 25 mm or more, peeling or the like tends to be difficult to occur in an endurance test such as a heat resistance test.

The peeling force of the pressure-sensitive adhesive layer can be measured by the following method. First, the pressure-sensitive adhesive composition was coated on a release-treated surface of a release-treated polyethylene terephthalate (PET) film so as to have a thickness of 20 탆 after drying using an applicator and dried at 100 캜 for 1 minute to obtain a sheet- For 7 days. Subsequently, the pressure-sensitive adhesive sheet was bonded to the protective film side of the polarizing plate, cut into a piece having a width of 25 mm and a length of 150 mm so that the absorption axis of the polarizing plate was parallel to the side in the width direction, . This is subjected to an autoclave treatment at a temperature of 50 캜 under a load of 5 kg for 20 minutes and then left under an environment of a temperature of 23 캜 and a relative humidity of 60% RH for 10 hours. Thereafter, the end of the polarizing plate was peeled off, and it was confirmed that the adhesive was attached to the polarizing plate side. Then, using a tensile tester, peeling at 1000 mm / min such that the angle between the width direction and the peeling direction was 45 degrees 180 ° peel test is carried out at a speed of 180 °. As the tensile tester, a universal testing machine "Autograph AG-I" manufactured by Shimadzu Seisakusho Co., Ltd. or the like can be used.

[Liquid crystal display device]

The polarizing plate of the present invention is bonded to a liquid crystal cell through a pressure-sensitive adhesive layer or an adhesive layer to form a liquid crystal display panel, and combined with a backlight or the like to form a liquid crystal display device. The polarizing plate of the present invention can be obtained by combining a protective film (first protective film) having a breaking strength of 50 MPa or more with a polarizing film having a thickness of 15 탆 or less and a sticking strength per unit film thickness of 4.5 gf / It is possible to prevent the polarizing film from being broken when the polarizing plate is peeled from the interface with the layer or the adhesive layer.

[ Example ]

Hereinafter, the present invention will be described in more detail with reference to examples, but the present invention is not limited to these examples. In the examples, the corona treatment and the breaking strength measurement of the protective film were measured by the following methods.

<Corona treatment>

The corona treatment was carried out by a corona discharge device manufactured by Kasuga Electric Co., Ltd. Specifically, a corona surface treatment frame "STR-1764", a high frequency power source "CT-0212" and a high pressure transformer "CT-T02W" were used.

<Measurement of Breaking Strength of Protective Film>

The breaking strength of the protective film was measured by the following method. First, using a universal testing machine "Autograph AG-I" manufactured by Shimadzu Seisakusho Co., Ltd., equipped with a load cell 500 N and a thermostat, the protective film to be measured was cut into 15 mm wide × 150 mm long pieces And the distance between the markers of the measuring instrument was set at 100 mm. On the other hand, the longitudinal direction of the film piece was cut so as to be parallel to the conveying direction. Then, according to JIS K 7127: 1999 "Tensile test method for plastic film and sheet", the modulus of elasticity at a test speed of 50 mm / min was determined. Further, the film was pulled out until the film was broken at a test speed of 50 mm / min, and the stress when the film was broken was regarded as the breaking strength of the film.

[Example 1]

A polyvinyl alcohol film (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) having a thickness of 20 占 퐉 was uniaxially stretched by about 5 times by dry stretching and immersed in pure water at 60 占 폚 for one minute And then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C for 20 seconds, and then dried at 65 ° C to produce a polarizing film having a thickness of 7 μm in which iodine was adsorbed and oriented on a polyvinyl alcohol film.

A protective film (product name "Zeonoafilm (registered trademark) ZF14-013" Re = 2 nm, manufactured by Nippon Zeon Co., Ltd.) having a thickness of 13 占 퐉 was bonded to one side of the polarizing film with a polyvinyl alcohol- An acrylic adhesive layer having a thickness of 15 占 퐉 was laid on the other surface (opposite to the polarizing film) of the film. On the other side of the polarizing film (opposite to the protective film), a brightness enhancement film (trade name "APF-V4HC" manufactured by 3M Co., Ltd.) having a thickness of 19 占 퐉 was laminated on the other side Trade name "NFC-L2 ", manufactured by Kao Corporation) to prepare a polarizing plate. The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 59 탆. The puncture strength per unit film thickness of the polarizing film was 9.6 gf / 占 퐉, the breaking strength of the protective film was 60 MPa, and the breaking strength per unit film thickness of the protective film was 4.6 MPa / 占 퐉. On the other hand, the polyvinyl alcohol-based adhesive is prepared by adding 2 parts by weight of acetoacetyl-modified polyvinyl alcohol (trade name: GOSEPHASE (registered trademark) Z-200, manufactured by Nippon Gosei Kagaku Kogyo K.K.) , And 2 parts by weight of sodium glyoxylate (trade name "SPM-01 ", manufactured by Nippon Gosei Chemical Industry Co., Ltd.).

[Example 2]

(1) Resin layer formation process

As the base film, an unoriented polypropylene (PP) film (melting point: 163 占 폚) having a thickness of 90 占 퐉 was used and its surface was subjected to corona treatment to form a primer layer on the corona-treated surface. The primer layer was prepared by dissolving a polyvinyl alcohol powder (trade name "Z-200" manufactured by Nippon Gosei Chemical Industry Co., Ltd., average degree of polymerization: 1100, degree of saponification: 99.5 mol% , And 5 parts by weight of a crosslinking agent (trade name: Sumirez Resin (registered trademark) 650 manufactured by Daoka Kagaku Kogyo K.K.) was added to 6 parts by weight of polyvinyl alcohol powder, . For forming the primer layer, this mixed aqueous solution was coated on the corona-treated surface of the base film with a small-diameter gravure coater, and this was dried at 80 DEG C for 10 minutes. The thickness of the primer layer was 0.2 탆.

Then, a polyvinyl alcohol powder (trade name: "PVA124" manufactured by Kabushiki Kaisha Kuraray Co., Ltd., average degree of polymerization: 2400, degree of saponification: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 8% did. The resulting aqueous solution was coated on the primer layer using a lip coater and dried at 80 DEG C for 20 minutes to produce a three-layer laminated film comprising a base film, a primer layer and a resin layer.

(2) Stretching process

The laminated film was subjected to free-end uniaxial stretching at 160 캜 at a stretch ratio of 4.8 times using a longitudinal uniaxial stretching apparatus of a float to obtain a stretched film.

(3) Dyeing process

Thereafter, the stretched film was immersed in a dyeing solution which is a mixed aqueous solution of iodine and potassium iodide at 30 占 폚 for about 180 seconds, and then dyed. Then, the necessary iodine solution was washed away with pure water at 10 占 폚. Subsequently, the substrate was immersed in the crosslinked solution 1 at 78 ° C for 120 seconds and then immersed in the crosslinked solution 2 at 70 ° C containing boric acid and potassium iodide for 60 seconds. Thereafter, it was washed with pure water at 10 캜 for 10 seconds, and finally dried at 40 캜 for 300 seconds. By the above steps, a polarizing film layer having a thickness of 5 占 퐉 was formed from the resin layer to obtain a polarizing laminated film. The mixing ratio of each solution is as follows.

<Dyeing solution>

Water: 100 parts by weight

Iodine: 0.6 parts by weight

Potassium iodide: 10 parts by weight

&Lt; Crosslinking solution 1 &

Water: 100 parts by weight

Boric acid: 9.5 parts by weight

&Lt; Crosslinking solution 2 &

Water: 100 parts by weight

Boric acid: 5.0 parts by weight

Potassium iodide: 6 parts by weight

(4) First bonding step

The joint surface of a protective film having a thickness of 13 占 퐉 (product name "Zeonoiafilm (registered trademark) ZF14-013" Re = 2 nm, manufactured by Zeon) was subjected to corona treatment to obtain the same poly Using a vinyl alcohol-based adhesive, the polarizing laminated film produced in (3) was bonded to the polarizing film layer on the side opposite to the base film with a corona-treated face.

(5) Second bonding step

The base film was peeled off from the film having the five-layer structure prepared in the above (4) to obtain a polarizing plate having a one-side protective film. The base film was easily peeled off. (Trade name: "APF-V4HC ", trade name, manufactured by 3M Co., Ltd.) was laminated on the other side of the polarizing film (the side opposite to the protective film) with an ultraviolet curable pressure- ") To prepare a polarizing plate. On the other surface (the surface opposite to the polarizing film) of the protective film of the polarizing plate, an acrylic pressure-sensitive adhesive layer having a thickness of 15 占 퐉 was laid. The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 57 mu m. The sticking strength per unit film thickness of the polarizing film was 5.2 gf / 占 퐉, the breaking strength of the protective film was 60 MPa, and the breaking strength per unit film thickness of the protective film was 4.6 MPa / 占 퐉.

[Example 3]

A polarizing plate in which a protective film having a thickness of 13 占 퐉 (trade name: "Zeonoafilm (registered trademark) ZF14-013" Re = 2 nm, manufactured by Zeon) was laminated instead of the brightness enhancement film of Example 1. The lamination of the protective films was carried out by corona treatment on the bonding surfaces, and the following ultraviolet curing adhesive was coated on the treated surface with a microgravure coater and laminated on the coated surface. Thereafter, an ultraviolet ray was irradiated from the protective film side so that the accumulated light quantity was 250 mJ / cm 2 using an ultraviolet ray irradiator equipped with a belt conveyer equipped with an ultraviolet lamp "D bulb" manufactured by Fusion UV Systems Co., . The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 48 탆. The puncture strength per unit film thickness of the polarizing film was 9.6 gf / 占 퐉, the breaking strength of the protective film was 60 MPa, and the breaking strength per unit film thickness of the protective film was 4.6 MPa / 占 퐉.

The above-mentioned ultraviolet ray-curable adhesive was prepared by mixing the following components and defoaming them into a liquid state. On the other hand, the photocationic polymerization initiator obtained in the form of a 50% propylene carbonate solution was used. The blending amount (2.25 parts) described above is a solid amount.

3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate 75 parts

20 parts of 1,4-butanediol diglycidyl ether

5 parts of 2-ethylhexyl glycidyl ether

Triarylsulfonium hexafluorophosphate based light-ion polymerization initiator 2.25 parts

[Example 4]

Except that a protective film having a thickness of 20 占 퐉 (manufactured by Konica Minolta Corporation under the trade name of "Zero Nofilm (registered trademark) ZF14-013 ", trade name; manufactured by Nippon Zeon Co., Quot; Re = 3 nm] was used as a polarizing plate. The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 66 탆. The puncture strength per unit film thickness of the polarizing film was 9.6 gf / 占 퐉, the breaking strength of the protective film was 150 MPa, and the breaking strength per unit film thickness of the protective film was 7.5 MPa / 占 퐉.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 2 except that the stretching magnification of the polarizing film was changed to 5.2 times. The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 57 mu m. The sticking strength per unit film thickness of the polarizing film was 4.2 gf / 占 퐉, the breaking strength of the protective film was 60 MPa, and the breaking strength per unit film thickness of the protective film was 4.6 MPa / 占 퐉.

[Comparative Example 2]

Except that the protective film was changed to a 15 占 퐉 -thick polyolefin-based resin film (trade name: ARTON FILM (registered trademark) FEKB015D3? Re = 1 nm, manufactured by JSR Corporation). The thickness of the polarizing plate including the pressure-sensitive adhesive layer was 48 占 퐉. The puncture strength per unit film thickness of the polarizing film was 9.6 gf / 占 퐉, the breaking strength of the protective film was 45 MPa, and the breaking strength per unit film thickness of the protective film was 3.0 MPa / 占 퐉.

Table 1 shows the measurement result of the stiction intensity per unit film thickness of the polarizing film and the evaluation of the releasability with respect to the polarizing plate produced in Examples and Comparative Examples.

(Measurement of the stiction intensity per unit film thickness when the polarizing film is cracked in the absorption axis direction)

Polarizing plates prepared in Examples and Comparative Examples were immersed in cyclohexane while being attached to an ultrasonic cleaner to dissolve and remove the protective film bonded to both surfaces, and the polarizing film was taken out and subjected to a sticking test. The piercing test was carried out using a handy compression tester "KES-G5 Needle Penetration Measurement Specification" manufactured by KATO TECH CORPORATION equipped with a needle having a tip diameter of 1 mmφ and 0.5 R. The measurement was conducted under the conditions of a temperature of 23 占 占 폚 and at a threshing speed of 0.33 cm / sec. The sticking strength measured in the sticking test was a piercing test of 12 test pieces, and the average value was determined. The thickness of the polarizing film was measured with a contact type film thickness meter (trade name: "DIGIMICRO (registered trademark) MH-15M ", manufactured by Nikon Corporation) to determine the stiction intensity per unit film thickness. The results are shown in the &quot; sting intensity &quot;

(Evaluation of reworkability)

The test piece was cut into a size of 25 mm in width and 150 mm in length so that the absorption axis of the polarizing plate was parallel to the side in the width direction. This was pressed on alkali-free glass through the acrylic pressure-sensitive adhesive layer in a state inclined by 45 占 in the vertical tensile direction and autoclaved at a temperature of 50 占 폚 and a load of 5 kg for 20 minutes and then subjected to autoclave treatment at a temperature of 23 占 폚 and a relative humidity of 60% Under the environment for 10 hours. Thereafter, the end of the polarizing plate was peeled off, and after confirming that the pressure-sensitive adhesive adhered to the polarizing plate side, it was peeled off at 180 ° using a tensile tester ("Autograph AG-I" manufactured by Shimadzu Seisakusho Co., I took the test. On the other hand, the test was carried out at a room temperature (25 캜) at a tensile speed of 1000 mm / min.

(Criteria for reworkability)

X: Breakage occurred in the polarizing plate during peeling.

?: The polarizing plate could be peeled without peeling during peeling.

[Table 1]

According to the present invention, in the process (rework process) in which the polarizing plate is peeled off at the interface between the pressure-sensitive adhesive layer or the adhesive layer and the liquid crystal cell after the polarizing plate is laminated on the liquid crystal cell with the pressure-sensitive adhesive layer or the adhesive layer, breakage in the polarizing plate is suppressed .

1: polarizing film
3: Protective film (first protective film)
5: Second protective film
10: polarizer
15: Pressure-sensitive adhesive layer
20: liquid crystal cell
30: Non-alkali glass plate

Claims (9)

A polarizing plate comprising a polarizing film and a protective film,
Wherein the polarizing film has a thickness of 15 占 퐉 or less and a sticking strength per unit film thickness of 4.5 gf / 占 퐉 or more and 15 gf / 占 퐉 or less,
The breaking strength of the protective film is 50 MPa or more,
Wherein the protective film has a pressure-sensitive adhesive layer on a surface opposite to a surface bonded to the polarizing film,
Wherein the pressure-sensitive adhesive layer is for bonding to a liquid crystal cell. The polarizing plate according to claim 1, wherein the protective film has an in-plane retardation value of 200 nm or less. The polarizing plate according to claim 1 or 2, wherein the polarizing film has the protective film laminated on one side thereof and the optical layer laminated on the other side thereof. The polarizing plate according to claim 3, wherein the optical layer has a surface treatment layer on at least one side thereof. The protective film according to claim 1 or 2, wherein the protective film is selected from the group consisting of a cycloolefin resin film, a cellulose resin film, a polycarbonate resin film, a polyolefin resin film, a polyester resin film and an acrylic resin film At least one layer of a polarizing plate. The polarizing plate according to claim 1 or 2, wherein the protective film has a breaking strength per unit film thickness of 3.5 MPa / 탆 or more. The polarizing plate according to claim 1 or 2, wherein the pressure-sensitive adhesive layer has a peel force of not more than 10 N / 25 mm when subjected to a 180 ° peel test. The liquid crystal display device according to claim 1 or 2, wherein the polarizing plate has a liquid crystal panel laminated on the liquid crystal cell through the pressure-sensitive adhesive layer. delete

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