TWI645222B - Polarizing plate and liquid crystal display device - Google Patents

Abstract

The present invention provides a polarizing plate which is a polarizing plate which can be peeled off without causing breakage of a polarizing plate when a polarizing plate is peeled off from a liquid crystal display device to which a polarizing plate is applied.

The polarizing plate of the present invention includes a polarizing film having a thickness of 15 μm or less and a puncture strength per unit film thickness of 4.5 gf/μm or more, and a breaking strength of the protective film of 50 MPa or more.

Description

Polarizing plate and liquid crystal display device

The present invention relates to a polarizing plate, a polarizing plate with an adhesive, and a liquid crystal display device.

The polarizing plate is widely used as a polarizing supply element or a polarized detecting element of a display device such as a liquid crystal display device. As the polarizing plate, generally, a member in which a protective film is bonded to one surface or both surfaces of a polarizing film using an adhesive is used. In recent years, as the thickness of the liquid crystal display device is reduced, the thickness of the polarizing plate is also required to be reduced.

In order to reduce the thickness of the polarizing plate, a polarizing plate in which a protective film is bonded to only one surface of the polarizing film has been developed (Patent Document 1). The polarizing plate is provided with an adhesive directly on the surface of the polarizing film opposite to the protective film, and is laminated on the adhesive side to a liquid crystal cell or the like. Although the polarizing plate can be made thinner and peeled off from the adhesive layer together with the liquid crystal cell, when the rework is performed, there is a defect that the polarizing plate is broken or the like.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2001-194528

In order to solve the above problems, the present invention provides a polarizing plate which can be peeled off without causing breakage of a polarizing plate when a polarizing plate is peeled off from a liquid crystal display device to which a polarizing plate is applied.

The 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 μm or less and a puncture strength per unit film thickness of 4.5 gf/μm or more, and the breaking strength of the protective film is 50 MPa or more.

[2] The polarizing plate according to the above [1], 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, and a polyester resin film. And a film of at least one of the group consisting of acrylic resin films.

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

[4] The polarizing plate according to any one of [1], wherein the polarizing film has a protective film in a single-area layer and an optical layer in another area.

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

[6] A polarizing plate with an adhesive attached to any one of [1] to [5] In the polarizing plate, the surface of the protective film is formed with an adhesive layer, wherein the polarizer is cut into a width of 25 mm × a length of 150 mm, and laminated on a glass plate via an adhesive. The peeling force at the time of the 180 degree peeling test in the state which inclined 45 degree from the direction of the perpendicular|stretching was 10 N / 25 mm or less.

[7] A liquid crystal display device in which a polarizing plate with an adhesive according to [6] is laminated on at least a single piece of a liquid crystal cell.

According to the present invention, after the polarizing plate is laminated on the liquid crystal cell with the adhesive layer or the adhesive layer, the step of peeling off the interface between the adhesive layer or the adhesive layer and the liquid crystal cell (rework step) can suppress the occurrence of breakage of the polarizing film. . Therefore, it is possible to prevent the rework caused by the breakage of the polarizing film (small pieces of the polarizing plate remain on the surface of the liquid crystal cell, etc.), so that the liquid crystal cell can be reused.

1‧‧‧ polarizing film

3‧‧‧Protective film (first protective film)

5‧‧‧2nd protective film

10‧‧‧Polar plate

15‧‧‧Adhesive layer

20‧‧‧Liquid Crystal Box

30‧‧‧Aluminum-free glass plate

Fig. 1 is a schematic cross-sectional view showing a preferred configuration of a liquid crystal display device of the present invention.

Fig. 2 is a schematic view showing a method of measuring the peeling force of the adhesive layer.

[Polarizer]

In the polarizing plate of the present invention, the polarizing film 1 and the protective film 3 are provided, and the polarizing film 1 has a thickness of 15 μm or less and a puncture strength per unit film thickness of 4.5 gf/μm or more. Strong break of 3 The degree is 50 MPa or more. On the surface of the polarizing film 1 opposite to the bonding surface of the protective film 3, another protective film (second protective film) 5 may be further laminated. When the puncture strength per unit film thickness of the polarizing film is less than 4.5 gf/μm, the polarizing plate is laminated on the adhesive of glass or the like with an adhesive layer or an adhesive, and the polarizing plate is together with the adhesive layer or the adhesive layer. When the adherend is peeled off, the polarizing plate or the polarizing film tends to be broken. Further, in the case where the breaking strength of the protective film is less than 50 MPa, the polarizing plate or the polarizing film tends to be broken as well.

(1) Polarizing film

The polarizing film may be one in which a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based resin layer extending through one axis. When the thickness of the polarizing film is usually 20 μm or less, the thickness of the polarizing plate can be reduced. In the present invention, a polarizing film having a thickness of 15 μm or less is used, but the thickness of the polarizing film is preferably 8 μm or less. Further, usually, the thickness of the polarizing film is 2 μm or more.

As the polyvinyl alcohol-based resin, a polyvinyl acetate-based resin can be used for saponification. As the polyvinyl acetate-based resin, in addition to the polyvinyl acetate of the homopolymer of vinyl acetate, for example, a copolymer of vinyl acetate and a monomer copolymerizable therewith. As a monomer copolymerizable with vinyl acetate, for example, an unsaturated carboxylic acid, an olefin, a vinyl ether, an unsaturated sulfonic acid, an acrylamide having an ammonium group, or the like.

The degree of saponification of the polyvinyl alcohol-based resin may be in the range of 80 mol% or more, and is preferably in the range of 90 to 99.5 mol%, more preferably in the range of 94 to 99 mol%. a polyvinyl alcohol-based resin, which may be a part of a modified modified polyvinyl alcohol, for example, a polyvinyl alcohol, an ethylene such as ethylene or propylene A hydrocarbon; an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or 2-butenoic acid; an alkyl ester of an unsaturated carboxylic acid; and a modified acrylamide. The average degree of polymerization of the polyvinyl alcohol-based resin is preferably from 100 to 10,000, more preferably from 1,500 to 8,000, still more preferably from 2,000 to 5,000.

The dichroic dye contained in the polarizing film (adsorption alignment) may be iodine or a dichroic organic dye, and conventionally used ones can be used. The dichroic dye may be used alone or in combination of two or more.

In the present invention, it is important that the thickness of the polarizing film is 15 μm or less, and the puncture strength per unit film thickness when the polarizing film is broken in the absorption axis direction is 4.5 gf/μm or more. The puncture strength per unit film thickness can be improved by reducing the stretching ratio at the time of manufacturing the polarizing film. When the puncture strength per unit film thickness is less than 4.5 gf/μm, the ratio at which the polarizing film is broken tends to be high, and the length at which the fracture occurs tends to be long.

Since the polarizing plate has a polarizing film having a puncture strength of 4.5 gf/μm or more per unit film thickness, the strength of the polarizing film itself is sufficiently high, so that even in the case where a thin polarizing film produces minute defects, the crack can be suppressed. occur. The puncture strength per unit film thickness is preferably 5.0 gf/μm or more, more preferably 5.5 gf/μm or more, still more preferably 7.0 gf/μm or more. The upper limit is not particularly limited, but is preferably 15 gf/μm or less, and more preferably 10 gf/μm or less from the viewpoint of imparting good optical characteristics to the polarizer.

The puncture strength can be obtained by puncturing the polarizing film in the normal direction after fixing the auxiliary film, and measuring the strength at the time of fracture in the absorption axis direction. For example, the measurement can be performed by a compression tester having a load cell. As pressure Examples of the shrink tester include a hand-held compression tester "KES-G5 type" manufactured by Kato Technology Co., Ltd., and a small table tester "EZ Test" manufactured by Shimadzu Corporation.

The measurement of the puncture strength is performed, for example, by sandwiching a polarizing film between two sample stages having a circular hole having a diameter of 15 mm or less that can pass through the puncture aid. The puncture aid is a cylindrical rod, and preferably has a spherical or hemispherical puncture needle at the tip end of the polarizing film. a pointed spherical portion or a hemispherical portion having a diameter of preferably 0.5 mm Above, 5mm the following. Moreover, the radius of curvature thereof is preferably greater than 0R and less than 0.7R. The puncture speed of the compression tester is preferably 0.05 cm/sec or more and 0.5 cm/sec or less.

The puncture strength was measured by fixing the test piece to the auxiliary tool and then puncturing it from the normal direction, and measuring the strength at the time of the break in the horizontal direction (absorption axis direction). The measurement can be performed on test pieces of five or more polarizing films, and the average value thereof is used as the puncture strength. The puncture strength per unit thickness can be calculated by dividing the measured puncture strength by the thickness of the polarizing film used in the measurement. In this method, the polarizing film is stretched in the direction of the transmission axis, and the breaking strength at the time of the fracture in the absorption axis direction can be quantitatively measured. Therefore, the strength in the direction of the transmission axis which cannot be measured due to the easy breakage of the polarizing film can be measured.

(2) Protective film

A protective film is laminated on at least one side of the polarizing film. The protective film may be a transparent resin film composed of a thermoplastic resin. Examples of the thermoplastic resin include a chain polyolefin resin such as a polypropylene resin and a polyolefin resin such as a cyclic polyolefin resin; cellulose triacetate and fibers. A cellulose ester resin such as a diacetate; a polyester resin such as polyethylene terephthalate, polyethylene naphthalate or polybutylene terephthalate; or a polycarbonate resin (meth)acrylic resin; or such mixtures, copolymers, and the like.

The cyclic polyolefin-based resin is a general term for a resin in which a cyclic olefin is polymerized by a polymerization unit. For example, JP-A No. 1-240517, JP-A No. 3-148882, and JP-A No. 3-122137 The resin described. Specific examples of the cyclic polyolefin-based resin include a ring-opened (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a chain olefin such as ethylene or propylene, and a cyclic olefin ( Representative of a random copolymer) and such graft copolymers modified with an unsaturated carboxylic acid or a derivative thereof, and such hydrides and the like. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin.

Cyclic polyolefin resins are sold in various commercial products. As an example of the commercial product of the cyclic polyolefin resin, the product name is "TOPAS" (registered trademark) and JSR which are produced by Topas advanced Polymers GmbH and sold by Polyplastics Co., Ltd. in Japan. "ARTON" (registered trademark) sold by the company, "ZEONOR" (registered trademark) and "ZEONEX" (registered trademark) sold by Japan ZEON Co., Ltd., and "Apel" (registered trademark) sold by Mitsui Chemicals Co., Ltd. )Wait.

Further, a film-formed cyclic polyolefin-based resin film can be used as the protective film. As an example of a commercial item, it is represented by a product name, and "ARTON FILM" sold by JSR Co., Ltd. ("ARTON" is a registered trademark of the same company), "Esushina" (registered trademark) and "SCA40" sold by Sekisui Chemical Industry Co., Ltd., and limited sales of Japanese ZEON shares. "ZEONOR FILM" (registered trademark) and so on.

The cellulose ester-based resin is usually cellulose triacetate, cellulose diacetate, cellulose tripropionate, cellulose diacetate, or the like, and may be used. Part of it is modified by other substituents. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, these copolymers may be used, and a part of the hydroxyl group may be modified with another substituent. Among these, cellulose triacetate (cellulose triacetate: TAC) is particularly preferred. Many products of cellulose triacetate are commercially available, and it is also advantageous in terms of availability and cost. Examples of commercial products of cellulose triacetate are represented by trade names such as "Fujitac (registered trademark) TD80", "Fujitac (registered trademark) TD80UF", "Fujitac (registered trademark) sold by Fujifilm Co., Ltd. ) TD80UZ" and "Fujitac (registered trademark) TD40UZ", TAC film "KC8UX2M", "KC2UA" and "KC4UY" manufactured by Konica Minolta Co., Ltd.

The protective film may be an optical function such as a retardation film. The retardation film can be formed by, for example, extending a transparent resin film (one-axis stretching or biaxial stretching) or forming a liquid crystal layer on the protective film, whereby an arbitrary retardation value can be imparted. 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, for example, 200 nm or less. In-plane retardation value, preferably 150 nm or less, more preferably 100 nm Hereinafter, it is more preferably 50 nm or less. When the in-plane retardation value exceeds 200 nm, the monoaxiality of the film becomes strong, and it is likely to be broken along the extending direction.

The protective film can be subjected to an easy subsequent treatment such as a saponification treatment, a corona treatment, a primer treatment, an anchor coating treatment, or the like on the surface opposite to the polarizing film. These processes can be carried out by conventional methods.

In the present invention, the breaking strength of the protective film which is applied to the adhesive layer of the liquid crystal cell is set to 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 addition, from the viewpoint of thinning of the polarizing plate, the thickness of the protective film is preferably as small as possible (for example, 30 μm or less, preferably 20 μm or less), in order to effectively suppress the polarizing plate or even when the protective film of the film is used. The breaking strength of the polarizing film and the breaking strength per unit film thickness of the protective film are preferably 3.5 MPa/μm or more, more preferably 4.0 MPa/μm or more, still more preferably 5.0 MPa/μm or more. The upper limit is not particularly limited, but the breaking strength per unit thickness of the protective film is usually 15 MPa/μm or less, preferably 10 MPa/μm or less.

The polarizing film may have the above protective film (first protective film) in one area layer and another protective film (second protective film) in another area layer. In this case, the same resin film as the first protective film may be used as the second protective film, and 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 may be different films.

The optical layer constituting the second protective film is, for example, a front plate, a brightness enhancement film, or a curable resin layer. As the front panel, for example, glass, glass substitute layer (plastic, resin cured, etc.). The brightness enhancement film is, for example, a multilayer film laminate having two or more layers of two or more kinds of materials having a refractive index difference, a vapor deposited multilayer film having a different refractive index used in a beam splitter, and a composite refractive index. Two or more layers of the birefringent layer multilayer film laminate of two or more kinds of materials, and two or more resin laminates of two or more kinds of resins having birefringence are used. The curable resin layer is, for example, a cured product of an active energy ray-curable compound. The active energy ray-curable compound means a compound which can be cured by irradiation with an active energy ray such as ultraviolet light, visible light, electron beam or X-ray. The active energy ray-curable compound may be a compound containing a cationically polymerizable compound, or may contain a radically polymerizable compound, or both of them may be contained.

The optical layer is preferably provided with a surface treatment layer on a surface opposite to the surface on which the layer on which the polarizing film is laminated. As the surface treatment layer, for example, a surface treatment layer (coating layer) of a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, an antifouling layer, or the like.

The thickness of the first protective film and the second protective film is preferably thinner from the viewpoint of thinning of the polarizing plate, but the strength is lowered when the thickness is too thin, and the workability is deteriorated. Therefore, the thickness of the first protective film and the second protective film is preferably 5 to 90 μm or less, more preferably 60 μm or less, still more preferably 30 μm or less, and particularly preferably 20 μm 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 via an adhesive layer or an adhesive layer, respectively. The adhesive layer is, for example, the same adhesive layer as that to be described later, which is disposed on the polarizing plate of the liquid crystal cell. The adhesive layer for laminating the polarizing film and the protective film may be the same adhesive layer or different from the adhesive layer to be attached to the polarizing plate to be bonded to the liquid crystal cell. As an adhesive for forming an adhesive layer, for example, an active energy ray-curable adhesive which can be cured by irradiation with an active energy ray such as ultraviolet light, visible light, electron beam or X-ray, or an adhesive component is dissolved in water or dispersed in A water-based adhesive or the like.

In the case of using an active energy ray-curable adhesive, the adhesive layer becomes its cured layer. More preferably, the epoxy-based compound which is cured by cationic polymerization is an active energy ray-curable adhesive which is a curable component, and more preferably an ultraviolet-curable adhesive which is a curable component of the epoxy-based compound. The epoxy compound herein means a compound having an average of one or more, preferably two or more epoxy groups in the molecule. The epoxy compound may be used alone or in combination of two or more.

Examples of the epoxy-based compound which can be suitably used include an alicyclic polyol obtained by subjecting an aromatic ring of an aromatic polyol to hydrogenation reaction, and reacting with epichlorohydrin, thereby obtaining a hydrogenated epoxy compound (having An aliphatic epoxy compound such as a polyglycidyl ether of an aliphatic alicyclic ring or an alkylene oxide adduct thereof; and one or more bonds in the molecule; An alicyclic epoxy compound of an epoxy group epoxy compound of a cyclic ring.

The active energy ray-curable adhesive may further contain a radically polymerizable (meth)acrylic compound as a curable component. The (meth)acrylic compound is, for example, a (meth) acrylate monomer having at least one (meth) propylene fluorenyloxy group in the molecule; and a compound obtained by reacting two or more kinds of functional groups, and intramolecular A (meth)acryloxy group-containing compound having at least two (meth) acryloxy group-containing (meth) acrylate oligomers.

The active energy ray-curable adhesive contains a epoxide-based compound which is cured by cationic polymerization as a curable component, and preferably contains a photocationic polymerization initiator. Examples of the photocationic polymerization initiator include an aromatic diazonium salt; an aromatic iodonium salt; an onium salt such as an aromatic sulfonium salt; an iron-aromatic hydrocarbon complex. In addition, when the active energy ray-curable adhesive contains a radically polymerizable curable component such as a (meth)acrylic compound, it is preferred to contain a photoradical polymerization initiator. As a photoradical polymerization initiator, for example, an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, xanthone, an anthrone , camphor, benzaldehyde, hydrazine and so on.

The active energy ray-curable adhesive may contain a cationic polymerization accelerator such as oxetane or a polyol, a photosensitizer, an ion scavenger, an antioxidant, a chain transfer agent, a tackifier, and a thermoplastic resin, as needed. Additives such as fillers, flow regulators, plasticizers, defoamers, antistatic agents, leveling agents, solvents, 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 μm, preferably 0.01 to It is about 5 μm, more preferably 2 μm or less (and even more preferably 1 μm or less).

As the water-based adhesive, for example, an adhesive composition containing a polyvinyl alcohol-based resin or an amine ester resin as a main component is preferable. The thickness of the adhesive layer formed of the water-based adhesive is usually 1 μm or less.

In the case where a polyvinyl alcohol-based resin is used as a main component of the adhesive, the polyvinyl alcohol-based resin may be a carboxyl-modified polyvinyl alcohol in addition to the partially saponified polyvinyl alcohol or the fully saponified polyvinyl alcohol. A modified polyvinyl alcohol-based resin such as an ethylene glycol-modified polyvinyl alcohol, a methylol-modified polyvinyl alcohol, or an amine-modified polyvinyl alcohol. The polyvinyl alcohol-based resin, in addition to the vinyl alcohol homopolymer obtained by saponification of the polyvinyl acetate homopolymer of vinyl acetate, may also be a copolymer of vinyl acetate and other monomers copolymerizable therewith. The obtained polyvinyl alcohol-based copolymer is saponified.

A 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 subsequent agent is usually 1 to 10 parts by weight, preferably 5 parts by weight or less based on 100 parts by weight of water.

In the adhesive composition comprising an aqueous solution of a polyvinyl alcohol-based resin, in order to improve the adhesion, it is preferred to add a hardening of a polyvalent aldehyde, a melamine-based compound, a zirconia compound, a zinc compound, glyoxal, and a water-soluble epoxy resin. Sexual components, crosslinkers. As the water-soluble epoxy resin, for example, a polyamine amine obtained by reacting a polyalkylene polyamine such as di-ethyltriamine or tri-ethylethylamine with a dicarboxylic acid such as adipic acid can be suitably used. A polyamidamine polyamine epoxy resin obtained by reacting with epichlorohydrin. As such a polyamine Commercial products of polyamine epoxy resin, such as "SUMIREZ RESIN (registered trademark) 650" and "SUMIREZ RESIN (registered trademark) 675" manufactured by Takaoka Chemical Industry Co., Ltd., "WS-525" manufactured by Starlight PMC Co., Ltd. "Wait. The amount of the hardening component and the crosslinking agent to be added (the total amount of the curing component and the crosslinking agent added together) is usually 1 to 100 parts by weight, preferably 1 to 100 parts by weight, based on 100 parts by weight of the polyvinyl alcohol resin. It is 1 to 50 parts by weight. When the amount of the hardening component and the crosslinking agent added is less than 1 part by weight based on 100 parts by weight of the polyvinyl alcohol-based resin, the effect of improving the adhesion tends to be small, and the curing component and the crosslinking agent are preferred. When the amount of addition is more than 100 parts by weight based on 100 parts by weight of the polyvinyl alcohol-based resin, the adhesive layer tends to become brittle.

Further, in the case of using an amine ester resin as a main component of the adhesive, as an example of a suitable adhesive composition, for example, a mixture of a polyester-based ionic polymer-type amine ester resin and a compound having a glycidyl group. The polyester-based ionic polymer-type amine ester resin refers to an amine ester resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced therein. Such an ionic polymer type amine ester resin is suitable as a water-based adhesive because it is directly emulsified in water to form an emulsion without using an emulsifier.

[Method of Manufacturing Polarizing Plate]

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

[a] A polyvinyl alcohol-based resin film (hereinafter also referred to as "polarizing film") having a polarizing property as a polarizing film is a single-layer film, and is made of a polyvinyl alcohol-based resin film, and is bonded to one side or both sides thereof. A method of protecting a film.

[b] coating at least one side of the base film with a polyvinyl alcohol-based resin After the coating liquid is formed into a polyvinyl alcohol-based resin layer, the obtained laminated film is subjected to a predetermined treatment to form a polarizing film on the polyvinyl alcohol-based resin layer, and the polarizing laminated film is bonded to the protective film to be peeled off. A method of a substrate film. In this method, after the base film is peeled off, the protective film may be bonded to the other surface.

(Manufacturing method [a])

In the production method [a], a polyvinyl alcohol-based resin film formed by forming a film of the polyvinyl alcohol-based resin is used as a starting material to prepare a polarizing film. As a method of forming a film of a polyvinyl alcohol-based resin, for example, a conventional method such as a melt extrusion method or a solvent casting method can be employed. The thickness of the unstretched polyvinyl alcohol-based resin film is, for example, about 10 to 150 μm.

The production method [a] may include, for example, a step of stretching a polyvinyl alcohol-based resin film, a step of dyeing a polyvinyl alcohol-based resin film by a dichroic dye to adsorb a dichroic dye, and adsorbing a dichroic dye; a step of treating the polyvinyl alcohol-based resin film with an aqueous solution of boric acid; and a water washing step after treatment with an aqueous solution of boric acid.

The one-axis extension of the polyvinyl alcohol-based resin film can be carried out before dyeing of the dichroic dye, simultaneously with dyeing, or after dyeing. The one-axis extension is carried out after dyeing, and the one-axis extension can be carried out before boric acid treatment or boric acid treatment. Moreover, one-axis extension can also be performed at these multiple stages.

One-axis extension can be carried out between rollers with different speeds, or with a hot roller. Further, the one-axis extension may be a dry stretching in which the stretching is performed in the atmosphere, or may be a wet stretching in which the polyvinyl alcohol-based resin film is stretched in a state of being expanded using a solvent. The stretching ratio is usually about 3 to 17 times, preferably 4 times or more, and preferably 8 times or less.

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

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide and dyed is usually used. The content of iodine in the aqueous dyeing solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water. Further, 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 aqueous dyeing solution is usually about 20 to 40 °C. Further, the immersion time (dyeing time) of the aqueous dyeing solution is usually about 20 to 1800 seconds.

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

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

The amount of boric acid in aqueous boric acid, usually relative to 100 The water by weight is about 2 to 15 parts by weight, preferably about 5 to 12 parts by weight. In the case where iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The amount of potassium iodide in the aqueous boric acid 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. As the aqueous solution of boric acid, sulfuric acid, hydrochloric acid, acetic acid, ascorbic acid or the like may be added as a pH adjuster. The immersion time in the aqueous boric acid solution is usually about 60 to 1200 seconds, preferably about 150 to 600 seconds, more preferably about 200 to 400 seconds. The temperature of the aqueous boric acid solution is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C.

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

After washing with water, drying treatment was 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 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds.

By drying, the moisture ratio of the polarizing film is reduced to a practical level. The moisture ratio is usually from 5 to 20% by weight, preferably from 8 to 15% by weight. When the water content is less than 5% by weight, the polarizing film loses flexibility, and the polarizing film may be damaged or broken after drying. Moreover, when the moisture ratio is more than 20% by weight, the thermal stability of the polarizing film may be deteriorated. Happening.

The first protective film may be bonded to at least one surface of the polarizing film by using an adhesive, and the adhesive may be cured to produce a polarizing plate. The second protective film may be attached to the other side of the polarizing film as needed.

The method of bonding the first protective film and the second protective film to the polarizing film using an active energy ray-curable adhesive, a water-based adhesive, or an adhesive, for example, one or both of the two films that have been bonded together The bonding surface, after applying an adhesive or an adhesive, a method of laminating two films by interposing the adhesive layer or the adhesive layer. For the application of the adhesive or the adhesive, for example, a casting method, a bar coating method, a gravure coating method, a slanting wheel coating method, a knife coating method, a slit coating method, a dip coating method, a spray method, or the like may be employed. . The casting method is a method in which the film to be bonded is moved in a direction substantially perpendicular to the direction of the object, in a substantially horizontal direction, or in an oblique direction therebetween, and the adhesive is applied to the surface thereof to spread. The film laminate which is laminated by the adhesive is usually pressed up and down by a pinch roller (a bonding roller) or the like.

When the protective film is bonded to the polarizing film, the bonding surface of the protective film and/or the polarizing film may be subjected to plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, etc., in order to improve adhesion. It is easy to carry out the treatment, wherein it is preferred to carry out plasma treatment, corona treatment or saponification treatment. For example, when the protective film is made of a cyclic polyolefin resin, plasma treatment or corona treatment is usually performed on the bonding surface of the protective film. Further, when the protective film is made of a cellulose ester-based resin, the saponification treatment is usually performed on the bonding surface of the protective film. As a saponification treatment, for example, a method of immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

In the case of using a water-based adhesive, it is preferred to carry out a drying step of the dried film laminate in order to remove water contained in the adhesive layer composed of the water-based adhesive after the film is bonded. Drying can be carried out, for example, by introducing a film laminate into a drying oven. The drying temperature (temperature of the drying oven) is preferably from 30 to 90 °C. When it is less than 30 ° C, the protective film tends to be easily peeled off from the polarizing film. Further, when the drying temperature exceeds 90 ° C, there is a fear that the polarizing performance of the polarizing film is deteriorated due to 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, more preferably 150 to 600 seconds.

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

In the case of using an active energy ray-curable adhesive, after the film is bonded, a curing step of curing the adhesive layer composed of the active energy ray-curable adhesive is performed. The hardening of the adhesive layer can be carried out by irradiating the film laminate with an active energy ray. The active energy ray is usually irradiated from the side of the first protective film. The active energy ray is preferably ultraviolet light.

The light source of the active energy ray is not particularly limited, but an active energy ray having a luminescent distribution of a wavelength of 400 nm or less is preferable. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a chemical lamp, a black lamp, A microwave excited mercury lamp, a metal halide lamp or the like is preferred.

The intensity of the active energy ray of the adhesive layer formed of the active energy ray-curable adhesive is appropriately determined depending on the composition of the adhesive, but is preferably a wavelength region effective for activation of the polymerization initiator. The irradiation intensity is set to be 0.1 to 6000 mW/cm ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and when it is 6000 mW/cm ² or less, the heat radiated from the light source and the heat generated by the active energy ray-curable adhesive harden are caused. Further, the yellowing of the agent layer and the occurrence of deterioration of the polarizing film are reduced.

The irradiation time of the active energy ray is appropriately determined depending on the composition of the adhesive. However, it is preferable to set the cumulative light amount indicated by the product of the irradiation intensity and the irradiation time to 10 to 10000 mJ/cm ² . When the cumulative amount of light is 10 mJ/cm ² or more, the active material derived from the polymerization initiator can be sufficiently generated, and the curing reaction can be more reliably performed. When the amount is 10000 mJ/cm ² or less, the irradiation time does not become too long. Can maintain good productivity.

The irradiation of the active energy ray is preferably carried out under the conditions of not reducing the degree of polarization of the polarizing film, the transmittance, the color tone, and the transparency of the protective film.

When the first protective film and the second protective film are laminated on the polarizing film, any protective film may be laminated on the polarizing film, and another protective film may be laminated, and the two protective films may be substantially simultaneously laminated on the polarizing film.

(Manufacturing method [b])

In the production method [b], a polyvinyl alcohol-based resin layer to be a polarizing film can be formed by applying a polyvinyl alcohol-based resin to a base film, for example, a resin layer forming step, an extending step, a dyeing step, and a first step. Fitting step and stripping From the step, a polarizing plate can be manufactured. An example of the production method [b] is, for example, the method described in Patent Document 1.

In the case of the second protective film of the other layer of the polarizing film, the second bonding step of bonding the second protective film to the other surface of the polarizing film may be performed after the peeling step. Further, in the case of the two-layer protective film, 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 liquid containing a polyvinyl alcohol-based resin is applied to at least one side of the base film, and then dried to form a polyvinyl alcohol-based resin layer to obtain a laminated film. This polyvinyl alcohol-based resin layer is a layer which becomes a polarizing film after an extension process and a dyeing process. The polyvinyl alcohol-based resin layer can be formed by applying a coating liquid containing a polyvinyl alcohol-based resin to one side or both surfaces of a base film, and drying the coating layer. A method of forming a polyvinyl alcohol-based resin layer by such coating is advantageous in that it is easy to obtain a polarizing film of a film.

The base film may be composed of a thermoplastic resin, and it is preferably composed of a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation. Specific examples of such a thermoplastic resin include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins; polyester resins; (meth)acrylic resins; cellulose triacetate and fibers. A cellulose ester resin such as a diacetate; a polycarbonate resin; a polyvinyl alcohol resin; a polyvinyl acetate resin; a polyarylate resin; a polystyrene resin; a polyether oxime resin; Lanthanide resin; polyamine resin; An amine resin; and such a mixture, copolymer, and the like.

The base film may be a single layer structure including one resin layer composed of one or two or more thermoplastic resins, or may be a plurality of layers of a resin layer composed of one or two or more thermoplastic resins. structure.

The chain-like polyolefin resin is a copolymer composed of two or more kinds of chain olefins, in addition to a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin. The base film composed of the chain polyolefin resin is preferable from the viewpoint of being easily and stably extended at a high magnification. Among them, the base film is composed of a polypropylene resin (a polypropylene resin of a homopolymer of propylene, a copolymer mainly composed of propylene), a polyethylene resin (a polyethylene resin of a homopolymer of ethylene, and ethylene as a main component). The copolymer) is preferably formed.

A copolymer mainly composed of propylene, which is an example of a thermoplastic resin constituting a base film, is a copolymer of propylene and another monomer copolymerizable therewith. As other monomers copolymerizable with propylene, for example, ethylene or an α-olefin. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and an α-olefin having 4 to 10 carbon atoms is more preferable. An α-olefin having 4 to 10 carbon atoms, for example, a linear monoolefin such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene or 1-decene; a branched monoolefin such as a 1-butene, a 3-methyl-1-pentene or a 4-methyl-1-pentene; a vinylcyclohexane or the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer.

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

Among the above, as the polypropylene resin, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer or a propylene-ethylene-1-butene random copolymer can be preferably used.

The stereoregularity of the polypropylene-based resin is preferably substantially isotactic or syndiotactic. The base film composed of a polypropylene-based resin having substantially three-dimensional regularity in the same row or in the opposite row has good workability and good mechanical strength in a high-temperature environment.

The polyester resin is a resin having an ester bond, and is generally composed of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof such as terephthalic acid, isophthalic acid, dimethyl terephthalate or dimethyl naphthalate may be used. As the polyol, a divalent diol such as ethylene glycol, propylene glycol, butanediol, neopentyl glycol, cyclohexanedimethanol or the like can be used.

As a representative example of the polyester resin, for example, polyethylene terephthalate of a polycondensate of terephthalic acid and ethylene glycol. Polyethylene terephthalate is a crystalline resin, and it is easy to carry out the treatment such as stretching before the crystallization treatment. The crystallization treatment can be carried out by heat treatment or the like after stretching or stretching as needed. Further, it is also suitable for use in a copolymerized polyester in which the crystallinity is lowered (or becomes amorphous) after recombining other kinds of monomers in the skeleton of polyethylene terephthalate. As an example of such a resin, for example, it is copolymerized with cyclohexanedimethanol or isophthalic acid. The Resin, etc., is also suitable for use due to its excellent extendability.

Specific examples of the polyester-based resin other than polyethylene terephthalate and copolymers thereof include, for example, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polybutylene. Propylene phthalate, propylene naphthalate, polyhexyl dimethyl terephthalate, cyclohexyl dimethyl naphthalate, mixtures, copolymers, and the like.

The (meth)acrylic resin is a resin mainly composed of a compound having a (meth)acryl fluorenyl group. As the (meth)acrylic resin, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-(meth)acrylic acid Ester copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and alicyclic hydrocarbon group A copolymer of a compound (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl (meth) acrylate), and the like. The (meth)acrylic resin is preferably a polymer containing a polyalkyl (meth)acrylate having a carbon number of from 1 to 6 as a main component, and more preferably methyl methacrylate as a main component. (50 to 100% by weight, preferably 70 to 100% by weight) of a methyl methacrylate-based resin.

The polycarbonate resin is an engineering plastic composed of a polymer having a monomer unit bonded through a carbonate group, and has a resin having high impact resistance, heat resistance, flame retardancy, and transparency. The polycarbonate resin may be a resin called a modified polycarbonate which has been modified to reduce the photoelastic coefficient, or a copolymerized polycarbonate which improves the wavelength dependence. Wait. A suitable commercial product can be used for the polycarbonate resin. As an example of a commercial item, it is represented by the brand name, for example, "PANLITE (registered trademark)" by Teijin Chemicals Co., Ltd., "IUPILON (registered trademark)" by Mitsubishi Engineering-Plastic Co., Ltd., and Sumika Styron Polycarbonate "SD POLYCA (registered trademark)" manufactured by the company, "CALIBRE (registered trademark)" manufactured by DOW Chemical Co., Ltd., etc.

Among the above, a polypropylene resin is preferably used from the viewpoints of elongation, heat resistance and the like.

The cyclic olefin resin and the cellulose ester resin used as the base film are referred to the matters described in the protective film. In addition, the chain polyolefin resin, the polyester resin, the (meth)acrylic resin, and the polycarbonate resin described above may be used as a protective film.

In addition to the above thermoplastic resin, any suitable additive may be added to the base film. As such an additive, for example, an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a mold release agent, a coloring preventive agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, a colorant, and the like.

The thickness of the base film can be appropriately determined, and is generally 1 to 500 μm, more preferably 300 μm or less, still more preferably 200 μm or less, and most preferably 5 to 150 μm from the viewpoint of workability such as strength and workability. .

The tensile modulus of the base film is preferably 100 MPa to 1500 MPa at 80 ° C, more preferably 140 MPa to 1000 MPa, 150 MPa. It is even better to 500 MPa. When the tensile modulus is too small, the hardness of the base film during the stretching process is insufficient, and defects such as wrinkles are likely to occur, and when it is too high, the workability at the time of stretching is deteriorated.

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

The coating liquid is applied to the substrate film by a wire bar coating method, a reverse coating method, a gravure coating method or the like, a roller coating method, a slit coating method, a notch wheel coating method, and a lip coating method. The cloth method; the spin coating method; the screen coating method; the spray coating method; the impregnation method; the spray method, and the like are appropriately selected. When the coating liquid is applied to both surfaces of the base film, each of the single surfaces may be sequentially used by the above method, or may be simultaneously applied to both surfaces of the base film by an impregnation method, a spray method, or another special device.

The drying temperature and drying time of the coating layer (polyvinyl alcohol-based resin layer before drying) are set depending on the kind of the solvent contained in the coating liquid. The drying temperature is, for example, 50 to 200 ° C, preferably 60 to 150 ° C. In the case where the solvent contains water, the drying temperature is preferably 80 ° C or higher. The drying time is, for example, 2 to 20 minutes.

The polyvinyl alcohol-based resin layer may be formed only on one side of the base film or on both sides. When formed on both sides, the polarization product can be suppressed The film is curled during the production of the film, and since two polarizing plates can be obtained from one polarizing laminated film, it is advantageous in terms of production efficiency of the polarizing plate.

The thickness of the polyvinyl alcohol-based resin layer of the laminated film is preferably from 3 to 60 μm, more preferably from 3 to 30 μm, still more preferably from 5 to 20 μm. When it is in this range, a polarizing film which is excellent in dyeability of a dichroic dye, is excellent in polarizing performance, and has a sufficiently small thickness can be obtained. When the thickness of the polyvinyl alcohol-based resin layer exceeds 60 μm, the thickness of the polarizing film exceeds 20 μm, and when the thickness of the polyvinyl alcohol-based resin layer is less than 3 μm, the thickness of the polyvinyl alcohol-based resin layer becomes too thin after stretching, and the dyeability tends to be deteriorated.

Before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, at least on the surface of the base film on the side of the polyvinyl alcohol-based resin layer, corona treatment and electricity can be performed. Slurry treatment, flame treatment, and the like.

Further, before the application of the coating liquid, in order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based system may be formed on the base film by a primer coating or an adhesive layer. Resin layer.

The undercoat layer can be formed by applying a coating liquid for forming an undercoat layer onto the surface of the base film and then drying it. The coating liquid for forming an undercoat layer preferably contains a component which can exert a certain strength of adhesion to both the base film and the polyvinyl alcohol-based resin layer. The coating liquid for forming an undercoat layer usually contains such a resin component and a solvent. As the resin component, a thermoplastic resin such as a (meth)acrylic resin or a polyvinyl alcohol-based resin, which is excellent in transparency, thermal stability, and elongation, is preferably used. Among them, it is better to use Fu A polyvinyl alcohol-based resin having a good adhesion.

As the polyvinyl alcohol-based resin, for example, a polyvinyl alcohol resin and a derivative thereof. As a derivative of a polyvinyl alcohol resin, in addition to polyvinyl formal, polyvinyl acetal, etc., for example, a polyvinyl alcohol resin is modified with an olefin such as ethylene or propylene; and acrylic acid, methacrylic acid, and 2- A modification of an unsaturated carboxylic acid such as crotonic acid; a modification of an alkyl ester of an unsaturated carboxylic acid; a modification by acrylamide or the like. Among the above polyvinyl alcohol-based resins, a polyvinyl alcohol resin is preferably used.

As the solvent, a general organic solvent or an aqueous solvent which can dissolve 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; dichloromethane and trichlorochloride; Chlorinated hydrocarbons such as ethylene and chloroform; alcohols such as ethanol, 1-propanol, 2-propanol and 1-butanol. However, when the undercoat layer is formed by using the coating liquid for forming an undercoat layer containing an organic solvent, the base film may be dissolved, and the solubility of the base film may be considered to select a solvent. When considering the influence on the environment, it is preferred to form an undercoat layer from a coating liquid containing water as a solvent.

A coating liquid for forming an undercoat layer may be added with a crosslinking agent in order to increase the strength of the undercoat layer. The crosslinking agent is suitably selected from conventional ones such as an organic system and an inorganic system depending on the type of the thermoplastic resin to be used. Examples of the crosslinking agent include an epoxy-based, isocyanate-based, dialdehyde-based, and metal-based crosslinking agent.

As the epoxy-based crosslinking agent, any one of a one-liquid curing type and a two-liquid curing type, for example, ethylene glycol diglycidyl ether or polyethylene glycol can be used. Alcohol diglycidyl ether, glycerol di- or tri-glycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether, diglycidyl aniline, diglycidyl Amines, etc.

As the isocyanate crosslinking agent, for example, methylphenyl diisocyanate, hydrogenated methylphenyl diisocyanate, trimethylolpropane-methylphenyl diisocyanate adduct, triphenylmethane triisocyanate, methylene double (4-phenylmethane) triisocyanate, isophorone diisocyanate, and such ketoxime blocks or phenolic blocks.

Examples of the dialdehyde crosslinking agent include glyoxal, malondialdehyde, succinaldehyde, glutaraldehyde, maleic aldehyde, and o-phthalaldehyde.

Examples of the metal-based crosslinking agent include metal salts, metal oxides, metal hydroxides, and organometallic compounds. As a metal salt, a metal oxide, or a metal hydroxide, for example, magnesium, calcium, aluminum, iron, nickel, zirconium, titanium, lanthanum, boron, zinc, copper, vanadium, chromium, and tin have a valence of two or more valences. Metal salts and their oxides, hydroxides.

The organometallic compound refers to a compound having a structure in which at least one organic group is directly bonded to a metal atom in the molecule, or an organic group is bonded through an oxygen atom or a nitrogen atom. The organic group means a monovalent or polyvalent group containing at least a carbon element, and may be, for example, an alkyl group, an alkoxy group, a decyl group or the like. Further, the term "bonding" means not only a covalent bond but also a coordination bond of a chelating compound or the like.

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

As an organic titanium compound, for example, tetra-n-butyl titanate, tetraisopropyl titanate, butyl titanate dimer, tetrakis(2-ethylhexyl) titanate, and tetramethyl titanate a titanium chelate compound such as titanium acetonate, titanium tetraacetone, titanium acetylacetonate, titanium octoate, titanium lactate, titanium triethanolamine, and titanium ethoxide acetate; polyhydroxystearic acid; Titanium telluride such as titanium.

Examples of the organic zirconium compound include zirconium n-propoxide, zirconium n-butoxide, zirconium tetraethoxide, zirconium monoacetate, zirconium acetonide, zirconium acetoacetate, and ethyl zirconium acetoacetate.

As the organoaluminum compound, for example, aluminum acetonate, an aluminum organic acid chelate or the like. As the organic ruthenium compound, for example, the ligands exemplified by the ligands exemplified above for the organotitanium compound and the organozirconium compound are bonded to the ruthenium.

In addition to the above crosslinking agent (low molecular crosslinking agent), a polymer crosslinking agent such as a methylolated melamine resin or a polyamide resin may be used. For example, "SUMIREZ RESIN (registered trademark) 650 (30)" and "SUMIREZ RESIN (registered trademark) are sold under the trade name of the company. ) 675" and so on.

When the undercoat layer is formed of a polyvinyl alcohol-based resin, a polyamine solvent epoxy resin, a methylolated melamine, a dialdehyde-based crosslinking agent, a metal chelate-based crosslinking agent or the like is preferably used as the crosslinking agent.

The ratio of the resin component to the crosslinking agent in the coating liquid for forming an undercoat layer is in the range of about 0.1 to 100 parts by weight based on 100 parts by weight of the resin component, depending on the type of the resin component. The type of the crosslinking agent can be appropriately determined, especially in the range of 0.1 to 50 parts by weight. The choice within the right range is preferred. Moreover, it is preferable that the coating liquid for forming an undercoat layer has a solid content concentration of about 1 to 25% by weight.

The thickness of the undercoat layer is preferably from about 0.05 to 1 μm, more preferably from 0.1 to 0.4 μm. When it is thinner than 0.05 μm, the effect of improving the adhesion between the base film and the polyvinyl alcohol-based resin layer is small, and if it is thicker than 1 μm, it is disadvantageous for thinning of the polarizing plate.

The method of applying the coating liquid for forming an undercoat layer to the base film can be the same as the coating liquid for forming a polyvinyl alcohol resin. The undercoat layer is applied to a surface (on one side or both sides of a base film) coated with a coating liquid for forming a polyvinyl alcohol resin. The drying temperature and drying time of the coating layer composed of the coating liquid for forming an undercoat layer are set depending on 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. In the case where the solvent contains water, the drying temperature is preferably 80 ° C or higher. The drying time is, for example, 30 seconds to 20 minutes.

In the case where the undercoat layer is provided, the order of application of the substrate film is not particularly limited. For example, in the case where a polyvinyl alcohol-based resin layer is formed on both surfaces of the substrate film, after the undercoat layer is formed on both surfaces of the substrate film, Further, a polyvinyl alcohol-based resin layer is formed on both sides, and an undercoat layer or a polyvinyl alcohol-based resin layer may be sequentially formed on one surface of the substrate film, and then a primer layer may be sequentially formed on the other side of the substrate film. A polyvinyl alcohol-based resin layer.

(extension step)

In this step, a laminate film composed of a base film and a polyvinyl alcohol-based resin layer is subjected to an elongation treatment to obtain a stretched film composed of a base film and a polyvinyl alcohol-based resin layer after stretching. The extension ratio of the laminated film can be The polarizing characteristics are appropriately selected depending on the desired polarizing characteristics, and are preferably more than 4 times and 17 times or less, more preferably more than 4 times and 8 times or less with respect to the original length of the laminated film. When the stretching ratio is 4 or less, the polyvinyl alcohol-based resin layer is not sufficiently aligned, and the degree of polarization of the polarizing film may not be sufficiently high. On the other hand, when the stretching ratio exceeds 17 times, the film is likely to be broken at the time of stretching, and the thickness of the stretching film is reduced to a required level or more, and the workability and workability in the subsequent step are likely to be lowered. The extension process is typically a one-axis extension.

The extension process is not limited to one-stage extension, but can also be performed in multiple stages. In this case, the multi-stage stretching treatment may be continuously performed before the dyeing step, or the stretching treatment after the second stage may be performed simultaneously with the dyeing treatment and/or the crosslinking treatment in the dyeing step. As described above, when the stretching process is performed in multiple stages, it is preferable to carry out the stretching process so that the total length of all the stages of the stretching process is more than four times the stretching ratio.

The stretching treatment may be a longitudinal extension extending in the longitudinal direction of the film (the conveying direction of the film), or a lateral stretching or oblique stretching extending in the width direction of the film. As the longitudinal stretching method, for example, stretching between rollers, stretching and stretching using a roller, extension using a chuck, or the like is used as a lateral stretching method such as a tenter method. The stretching treatment may be either a wet stretching method or a dry stretching method, but it is preferable to use a dry stretching method from the viewpoint of selecting a stretching temperature from a wide range.

The elongation temperature is set to a temperature at which the polyvinyl alcohol-based resin layer and the base film exhibit fluidity to the extent that they can be extended. Preferably, the phase transition temperature (melting point or glass transition temperature) of the substrate film is in the range of -30 ° C to +30 ° C, more preferably in the range of -30 ° C to +5 ° C, still more preferably -25 ° C. To the range of +0 °C. In the case where 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 indicated by the plurality of resin layers.

When the elongation temperature is lower than -30 ° C of the phase transition temperature, it is difficult to achieve a high-magnification extension of more than 4 times, or the fluidity of the base film is too low, and the elongation treatment tends to be difficult. When the elongation temperature exceeds the phase transition temperature of +30 ° C, the fluidity of the base film is too high, and the elongation tends to be difficult. Since it is easier to achieve a high-magnification extension of more than 4 times, the stretching temperature is in the above range, more preferably 120 °C or more. In the case where the extension temperature is 120 ° C or more, even if it is extended by more than 4 times, the elongation treatment does not cause difficulty.

The stretching treatment can be carried out while heating the laminated film. As the heating method, there is a zone heating method (for example, a method of heating in a furnace extension region in which hot air is blown and adjusted to a predetermined temperature); a method of heating using a roller, a method of heating the roller itself; and a heater heating method ( An infrared heater, a halogen heater, a plate heater, or the like is provided on the upper and lower sides of the laminated film, and heated by radiant heat. The method of extending between the rolls is preferably a zone heating method from the viewpoint of uniformity of elongation temperature. In this case, the two pairs of clamping rollers can be disposed in the temperature-adjusted extension region, or can be disposed outside the extension region, in order to prevent the adhesion of the laminated film and the clamping roller, to be disposed outside the extended region. Preferably.

In addition, the extension temperature refers to the ambient temperature in the region (for example, in the heating furnace) in the case of the zone heating method, and is heated by the heater. The method of heating in the furnace refers to the ambient temperature in the furnace. Moreover, in the case of the method of heating the roller body, it means the surface temperature of the roller.

A preheating step of preheating the laminated film may be provided before the extending step. As the preheating method, the same method as the heating method of the elongation treatment can be used. In the case where the extension processing method is the extension between the rollers, the preheating can be performed at any timing before, during or after passing through the clamping roller on the upstream side. In the case where the extension processing method is the extension of the hot roller, the preheating is preferably performed at a timing point before passing through the hot roller. The extension processing method is a case where the extension of the chuck is used, and it is preferable that the preheating is performed at a timing point before the distance between the chucks becomes wider. The preheating temperature is preferably in the range of -50 ° C to ± 0 ° C of the extension temperature, more preferably in the range of -40 ° C to -10 ° C of the extension temperature.

Moreover, after the stretching process in the extending step, a heat fixing process step may be provided. In the heat-fixing treatment, the heat treatment is performed at a temperature higher than the crystallization temperature while maintaining the stretched state in a state where the end portion of the stretched film is held by the jig. The crystallization of the polyvinyl alcohol-based resin layer is promoted by the heat setting treatment. The temperature of the heat setting treatment is preferably in the range of -0 ° C to -80 ° C of the extension temperature, more preferably in the range of -0 ° C to -50 ° C of the extension temperature.

(staining step)

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

In the case where iodine is used as the dichroic dye, the dyeing efficiency can be further improved, and it is preferable to further add the 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, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide of the dyeing solution is preferably from 0.01 to 20% by weight. Among the iodides, potassium iodide is preferably added. In the case of adding potassium iodide, the ratio of iodine to potassium iodide is expressed by weight ratio, preferably in the range of 1:5 to 1:100, more preferably in the range of 1:6 to 1:80, still more preferably 1:7. The range of 1:70.

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

Further, in the dyeing step, an additional stretching treatment may be performed on the stretched film. As an embodiment of the case, for example, 1) in the above-described extending step, after the stretching treatment is performed at a lower magnification than the target, the stretching treatment is performed in such a manner that the total stretching ratio becomes the target magnification in the dyeing step of the dyeing step. As described later, in the case where the cross-linking treatment is performed after the dyeing treatment, 2) in the above-described extending step, the stretching is performed at a lower magnification than the target After the treatment, in the dyeing treatment in the dyeing step, the stretching treatment is performed to the extent that the total stretching ratio is less than the target magnification, and then the stretching treatment is performed in the crosslinking treatment in such a manner that the final total stretching ratio becomes the target magnification. .

The dyeing step may include a cross-linking treatment step performed after the dyeing treatment. 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, a conventionally known one can be used, for example, a boron compound such as boric acid or borax, glyoxal or glutaraldehyde. The crosslinking agent may be used alone or in combination of two or more.

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

The crosslinking solution can comprise an iodide. By the addition of iodide, the in-plane polarization performance 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, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The concentration of the iodide of the crosslinking solution is preferably from 0.05 to 15% by weight, more preferably from 0.5 to 8% by weight.

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

The immersion time of the dyed film to the crosslinking solution is usually from 15 seconds to 20 minutes, preferably from 30 seconds to 15 minutes. and, The temperature of the crosslinking solution is preferably in the range of 10 to 90 °C.

Further, the crosslinking treatment can be carried out simultaneously by dyeing treatment by formulating a crosslinking agent in the dyeing solution. Moreover, the elongation treatment can also be performed in the crosslinking treatment. The specific aspect in which the elongation treatment is carried out in the crosslinking treatment is as described above.

After the dyeing step, it is preferred to perform a washing step and a drying step before the first bonding step to be described later. The washing step typically includes a water washing step. The water washing treatment can be carried out by immersing the film after the dyeing treatment or the crosslinking treatment in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 to 50 ° C, preferably from 4 to 20 ° C. The immersion time is usually from 2 to 300 seconds, preferably from 3 to 240 seconds.

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

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

(1st bonding step)

This step is a step of attaching the first protective film to the polarizing film of the polarizing laminated film, that is, the surface of the polarizing film opposite to the substrate film side via the adhesive to obtain a bonded film. In the case where the polarizing laminated film has a polarizing film on both surfaces of the base film, the protective film is bonded to each of the polarizing films on both surfaces. In this In some cases, the protective films may be the same kind of protective film or different kinds of protective films.

(peeling step)

In this step, a step of removing the base film by the bonded film obtained by bonding the first protective film to obtain a polarizing plate having a protective film on one side is obtained. Through this step, a polarizing plate in which a first protective film is laminated on a single surface of one surface of the polarizing film with a protective film is obtained. The polarizing laminated film has a polarizing film on both surfaces of the base film, and when the protective film is bonded to the polarizing film, two peeling steps can provide two single-sided protection from one polarizing laminated film. A polarizing plate for the film.

The method of peeling off the base film can be peeled off by the same method as the peeling step of the separator (release film) by the polarizing plate usually attached with the adhesive. The base film can be peeled off immediately after the first bonding step, or can be temporarily wound into a roll shape after the first bonding step, and then peeled off while being wound up in the subsequent steps.

(2nd bonding step)

This step is applied to the polarizing film of the polarizing plate with the protective film on one side, that is, on the side opposite to the protective film attached to the first bonding step, and the other adhesive is adhered via an adhesive or an adhesive. Membrane, and the step of obtaining a polarizing plate. In the case of performing the second bonding step, the second protective film may be bonded to the first bonding step. In this case, the first protective film is bonded in this step.

[Polarizer with Adhesive]

The polarizing plate has a surface opposite to the surface on which the polarizing film is laminated on the protective film having a breaking strength of 50 MPa or more (on the side of the first protective film in the case of the two-layer protective film of the polarizing film), via the adhesive layer or Layer layer It is preferable to use an adhesive body such as a liquid crystal cell. In other words, it is preferable to laminate the polarizing plate to the liquid crystal cell in such a manner that the liquid crystal cell/adhesive layer or the adhesive layer/the protective film/polarizing film having a breaking strength of 50 MPa or more is laminated in the order of lamination. As the adhesive or adhesive for forming the adhesive layer or the adhesive layer, a conventional one can be suitably used, and from the viewpoint of reworkability, it is preferred to use an adhesive.

As the adhesive, for example, an acrylic adhesive, a polyoxygen adhesive, a rubber adhesive, or the like is preferably an acrylic adhesive from the viewpoint of transparency, weather resistance, heat resistance, and workability. The adhesive may be appropriately formulated with a tackifier, a plasticizer, a filler composed of glass fiber, glass beads, metal powder, other inorganic powder, a pigment, a coloring agent, a filler, an antioxidant, an ultraviolet absorber, and the like. Various additives such as a decane coupling agent.

The adhesive is applied to a suitable substrate and allowed to dry to form an adhesive layer. The substrate is generally a plastic film, and as a typical example thereof, for example, a release film after release treatment is applied. The release film may be a surface formed by an adhesive such as a film composed of various resins such as polyethylene terephthalate, polybutylene terephthalate, polycarbonate, or polyarylate. Oxygen treatment, etc. For the application of the adhesive, for example, a roll coating method such as a reverse coating method or a gravure coating method, a spin coating method, a screen coating method, a spray coating method, an impregnation method, a spray method, or the like can be used.

The formation of the adhesive layer of the protective film can be carried out by a conventional method such as a method of transferring a release sheet provided with an adhesive layer. The thickness of the adhesive layer is usually from about 3 to 100 μm, preferably from 5 to 50 μm.

(peeling force of the adhesive layer)

The adhesive layer preferably has a peeling force of 10 N/25 mm or less when subjected to a 180-degree peeling test. When the peeling force exceeds 10 N/25 mm, the polarizing plate with the adhesive adheres to the adherend, and when the polarizing plate with the adhesive is peeled off from the adhesive together with the adhesive layer, the polarizing plate tends to be broken. Further, the peeling force is preferably 5 N/25 mm or more, more preferably 7 N/25 mm or more. When the peeling force is 5 N/25 mm or more, the endurance test such as the heat resistance test tends to be less likely to cause peeling or the like.

The peeling force of the adhesive layer can be measured by the following method. First, an adhesive composition was applied to a release-treated surface of a release-treated polyethylene terephthalate (PET) film using an applicator so that the thickness after drying became 20 μm and at 100 ° C. After drying for 1 minute to form a sheet-like adhesive, it was aged at room temperature for 7 days. After the adhesive sheet is bonded to the protective film side of the polarizing plate, the absorption axis of the polarizing plate is cut into a width of 25 mm × a length of 150 mm so that the absorption axis of the polarizing plate is parallel to the width direction, and the PET film is peeled off. Combined with glass. This was autoclaved at a temperature of 50 ° C and a weight of 5 kg for 20 minutes, and then allowed to stand in an environment of a temperature of 23 ° C and a relative humidity of 60% RH for 10 hours. Then, the end portion of the polarizing plate was peeled off, and it was confirmed that the adhesive was adhered to the polarizing plate side, and then the tensile tester was used. As shown in Fig. 2, the angle between the width direction and the peeling direction was 45 degrees. A 180 degree peel test was performed at a peel speed of 1000 mm/min. As the tensile tester, a universal tester "Autograph AG-I" manufactured by Shimadzu Corporation can be used.

[Liquid Crystal Display Device]

The polarizing plate of the present invention is bonded to the adhesive layer or the adhesive layer The liquid crystal cell is used as a liquid crystal display panel, and is combined with a backlight or the like to form a liquid crystal display device. The polarizing plate of the present invention is a polarizing film having a thickness of 15 μm or less and a puncture strength per unit film thickness of 4.5 gf/μm or more, and a protective film (first protective film) having a breaking strength of 50 MPa or more is combined so that the glass and the adhesive are adhered. When the polarizing plate is peeled off at the interface of the agent layer or the adhesive layer, the breakage of the polarizing film can be suppressed.

[Examples]

Hereinafter, the present invention will be described more specifically by way of examples, but the invention is not limited to the examples. In the examples, the measurement of the breaking strength of the corona treatment and the protective film was carried out by the following method.

<Corona treatment>

Corona treatment is carried out by a corona discharge device with limited restrictions from Kasuga Electric Co., Ltd. Specifically, a corona surface treatment frame "STR-1764", a high frequency power supply "CT-0212", and a high voltage transformer "CT-T02W" are used.

<Measurement of breaking strength of protective film>

The breaking strength of the protective film was measured by the following method. First, the protective film to be measured was cut into a piece having a width of 15 mm × a length of 150 mm using a universal testing machine "AUTOGRAPH AG-I" manufactured by Shimadzu Corporation, which has a dynamometer (500 N) and a constant temperature bath, and the mark of the measuring machine was used. The distance between the lines is set to 100 mm and the segment is placed therein. Further, the length direction of the segment of the film is cut in parallel with the conveying direction. Then, according to JIS K7127:1999 "Test method for tensile test of plastic film and sheet", the modulus of elasticity at the time of stretching at a test speed of 50 mm/min was obtained. Moreover, the film was stretched at a test speed of 50 mm/min until the film was broken, and when the film was broken The stress is the breaking strength of the protective film.

[Example 1]

A polyvinyl alcohol film having a thickness of 20 μm (average degree of polymerization: 2400, a degree of saponification of 99.9 mol% or more) was stretched by about 5 times by dry stretching, and then kept in a stretched state for 1 minute after immersing in pure water at 60 ° C for 1 minute. It was immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.05/5/100 at 28 ° C for 60 seconds. Then, an aqueous solution having a weight ratio of potassium iodide/boric acid/water of 8.5/8.5/100 was immersed at 72 ° C for 300 seconds. Subsequently, the mixture was washed with pure water at 26 ° C for 20 seconds, and then dried at 65 ° C to prepare a polarizing film having a thickness of 7 μm which was adsorbed to the polyvinyl alcohol film by iodine.

On the single side of the polarizing film, a protective film having a thickness of 13 μm (trade name “ZEONOR (registered trademark) ZF14-013, manufactured by Japan ZEON Co., Ltd., Re=2 nm) was used as a protective film. On the other side (the surface on the opposite side to the polarizing film), an acrylic pressure-sensitive adhesive layer having a thickness of 15 μm was attached. The other surface of the polarizing film (the surface opposite to the protective film) is a UV-curable adhesive having a thickness of 5 μm (trade name "NFC-L2" manufactured by Lintech Co., Ltd.), and a brightness-increasing film having a thickness of 19 μm (manufactured by 3M Co., Ltd.) The trade name "APF-V4HC"], and made a polarizing plate. The polarizing plate had a thickness of 59 μm after the adhesive layer was included. The puncture strength per unit film thickness of the polarizing film was 9.6 gf/μm, 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/μm. In addition, the polyvinyl alcohol-based adhesive is a polyvinyl alcohol-modified polyvinyl alcohol (trade name "GOHSEFIMER (registered trademark) Z-200, manufactured by Nippon Synthetic Chemical Co., Ltd.) in 100 parts by weight of water. 〕 2 parts by weight, sodium glyoxylate [trade name "SPM-01" manufactured by Nippon Synthetic Chemical Co., Ltd.) was prepared in an amount of 2 parts by weight.

[Embodiment 2]

(1) Resin layer forming step

As the base film, an unstretched polypropylene (PP) film (melting point: 163 ° C) having a thickness of 90 μm was used, and after the surface was subjected to corona treatment, an undercoat layer was formed on the corona-treated surface. The undercoat layer is formed of a mixed aqueous solution obtained by using a polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Co., Ltd., trade name "Z-200", an average degree of polymerization of 1100, and an average degree of saponification of 99.5 mol%] The solution was dissolved in a hot water of 95° C. to prepare a 3% by weight aqueous solution, and a crosslinking agent was prepared in an amount of 5 parts by weight based on 6 parts by weight of the polyvinyl alcohol powder. [Taiwan Chemical Industry Co., Ltd., trade name "SUMIREZ" RESIN (registered trademark) 650"]. The undercoat layer was formed by applying the mixed aqueous solution to the corona-treated surface of the substrate film using a small-diameter gravure coater, and drying it at 80 ° C for 10 minutes. The thickness of the undercoat layer was 0.2 μm.

Then, polyvinyl alcohol powder (trade name "PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a concentration of 8 wt%. An aqueous solution of polyvinyl alcohol. The obtained aqueous solution was applied onto the undercoat layer using a lip coater, and dried at 80 ° C for 20 minutes to prepare a three-layer laminated film composed of a base film, an undercoat layer, and a resin layer.

(2) Extension step

Use a floating longitudinal one-axis extension device for the above laminated film to 160 The °C was subjected to a 4.8-fold free-end one-axis extension to obtain a stretched film.

(3) Dyeing step

Next, the stretched film was immersed in a dyeing solution of a mixed aqueous solution of iodine and potassium iodide at 30 ° C for about 180 seconds to carry out dyeing, and then the excess iodine solution was washed with pure water at 10 ° C. Then, the crosslinking solution 1 of a boric acid aqueous solution at 78 ° C was immersed for 120 seconds, and then immersed in a crosslinking solution 2 containing boric acid and potassium iodide at 70 ° C for 60 seconds. Subsequently, it was washed with pure water of 10 ° C for 10 seconds, and finally, dried at 40 ° C for 300 seconds. From the above procedure, a polarizing film layer of 5 μm was formed from the resin layer to obtain a polarizing laminated film. The proportion of each solution was as follows.

<staining solution>

Water: 100 parts by weight

Iodine: 0.6 parts by weight

Potassium iodide: 10 parts by weight

<Crosslinking solution 1>

Water: 100 parts by weight

Boric acid: 9.5 parts by weight

<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

Protective film having a thickness of 13 μm (trade name “ZEONOR Film (registered trademark) ZF14-013, manufactured by ZEON Co., Ltd., Japan, Re=2 nm] The bonding surface was subjected to a corona treatment, and the same polyvinyl alcohol-based adhesive used in Example 1 was used, and the surface of the polarizing film layer of the polarizing laminated film produced in (3) on the opposite side to the substrate film was used. Fit with a corona treated surface.

(5) Second bonding step

The base film was peeled off from the film of the five-layer structure produced in the above (4), and a polarizing plate having a protective film on one side thereof was obtained. The base film can be easily peeled off. On the other side of the polarizing film (the surface opposite to the protective film), a UV-curable adhesive (trade name "NFC-L2" manufactured by Lintech Co., Ltd.) was used to laminate the brightness-enhancing film (trade name "APF" manufactured by 3M Company). -V4HC"], making a polarizing plate. An acrylic adhesive layer having a thickness of 15 μm was attached to the other surface (surface opposite to the polarizing film) of the protective film of the polarizing plate. The polarizing plate had a thickness of 57 μm after the adhesive layer was included. The puncture strength per unit film thickness of the polarizing film was 5.2 gf/μm, 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/μm.

[Example 3]

A protective film (trade name "ZEONOR Film (registered trademark) ZF14-013" manufactured by ZEON Co., Ltd., Japan, Re = 2 nm) was laminated to a thickness of 13 μm to replace the brightness enhancement film of Example 1, and a polarizing plate was produced. The laminate of the protective film was subjected to corona treatment on the bonding surface, and the following ultraviolet curable adhesive was applied to the treated surface by a micro gravure coater to coat the area layer. Then, using an ultraviolet irradiation device equipped with a belt conveyor of a UV lamp "D bulb" manufactured by FUSION UV Systems, the ultraviolet light is irradiated from the protective film side so that the cumulative amount of light becomes 250 mJ/cm ² . The agent then hardens. The polarizing plate had a thickness of 48 μm after the adhesive layer was included. The puncture strength per unit film thickness of the polarizing film was 9.6 gf/μm, 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/μm.

The ultraviolet curable adhesive is prepared by mixing the following components, defoaming, and preparing in a liquid state. Further, the photocationic polymerization initiator was obtained by using a 50% propylene carbonate solution. The amount of the above-described formulation (2.25 parts) is a solid content.

[Example 4]

In place of the protective film having a thickness of 20 μm (trade name “ZEROTAC” manufactured by Konica Minolta Co., Ltd., Re=3 nm], the protective film of Example 1 (trade name “ZEONOR manufactured by Japan ZEON Co., Ltd.” was used instead. A polarizing plate was produced in the same manner as in Example 1 except for ZF14-013. The thickness of the polarizing plate including the adhesive layer was 66 μm, and the puncture strength per unit film thickness of the polarizing film was 9.6 gf/μm. The breaking strength was 150 MPa, and the breaking strength per unit film thickness of the protective film was 7.5 MPa/μm.

[Comparative Example 1]

A polarizing plate was produced in the same manner as in Example 2 except that the stretching ratio of the polarizing film was 5.2. The polarizing plate has a thickness of 57 μ after the adhesive layer m. The puncture strength per unit film thickness of the polarizing film was 4.2 gf/μm, 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/μm.

[Comparative Example 2]

A polarizing plate was produced according to Example 3 except that the protective film was changed to a polyolefin resin film (product name "ARTON FILM (registered trademark) FEKB015D3" manufactured by JSR Co., Ltd., Re = 1 nm). The polarizing plate had a thickness of 48 μm after the adhesive layer was included. The puncture strength per unit film thickness of the polarizing film was 9.6 gf/μm, 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/μm.

The polarizing plates produced in the examples and the comparative examples were subjected to measurement of the puncture strength per unit thickness of the polarizing film and evaluation of the workability, and the results are shown in Table 1.

(Measurement of puncture strength per unit film thickness when the absorption axis direction of the polarizing film is broken)

The polarizing plates produced in the examples and the comparative examples were immersed in cyclohexane, and placed in an ultrasonic cleaner to dissolve and remove the protective film bonded to both surfaces to obtain a polarizing film, and a puncture test was performed. Puncture test using a loading tip diameter of 1 mm , 0.5R needle, Kato Technology Co., Ltd. Handheld compression tester "KES-G5 needle penetration force measurement specification", under the condition of temperature 23 ± 3 ° C, the puncture speed is 0.33 cm / sec under the measurement conditions The measurement was carried out. The puncture strength measured by the puncture test was performed by puncture test on 12 test pieces as the average value. The thickness of the polarizing film was measured by a contact type film thickness meter (trade name "DIGIMICRO (registered trademark) MH-15M" manufactured by NIKON Co., Ltd.), and the puncture strength per unit film thickness of the polarizing film was determined. The results are shown in the "Puncture Strength" column of Table 1.

(evaluation of heavy work)

The absorption axis of the polarizing plate was cut into a width of 25 mm × a length of 150 mm in parallel with the side in the width direction, and was used as a test piece. It was laminated to an alkali-free glass by a dielectric adhesive at a state inclined by 45 degrees from the vertical stretching direction, and autoclaved at a temperature of 50 ° C and a load of 5 kg for 20 minutes, and then at a temperature of 23 ° C, relative The mixture was allowed to stand for 10 hours under an environment of humidity of 60% RH. Then, the end portion of the polarizing plate was peeled off, and it was confirmed that the adhesive adhered to the polarizing plate side, and then a 180-degree peeling test was performed using a tensile tester [Universal Tester "Autograph AG-I" manufactured by Shimadzu Corporation). Further, the test was carried out in an environment of a stretching speed of 1000 mm/min and room temperature (25 ° C).

(Reliability benchmark)

×: The polarizing plate is broken in the peeling

○: The polarizing plate was not broken during peeling, and it was peelable.

[Industrial availability]

According to the present invention, after the polarizing plate is laminated on the liquid crystal cell with the adhesive layer or the adhesive, the step of peeling off the interface between the adhesive layer or the adhesive layer and the liquid crystal cell (rework step) can suppress the breakage of the polarizing film. .

Claims (8)

A polarizing plate having a polarizing film and a protective film, wherein the polarizing film has a thickness of 15 μm or less and a puncture strength per unit film thickness of 4.5 gf/μm or more and 15 gf/μm or less, and the breaking strength of the protective film is 50 MPa or more. An adhesive layer is provided on a surface of the protective film opposite to the bonding surface of the polarizing film, and the adhesive layer is used for bonding to a liquid crystal cell, and the piercing strength is measured by using a tip diameter of 1 mm. The 0.5R needle was carried out under the conditions of a temperature of 23 ± 3 ° C and a puncture speed of 0.33 cm / sec. The polarizing plate according to claim 1, wherein the in-plane retardation value of the protective film is 200 nm or less. The polarizing plate according to claim 1 or 2, wherein the polarizing film has the protective film in a single-area layer and an optical layer in another area layer. The polarizing plate of claim 3, wherein the optical layer has a surface treatment layer on at least one side. The polarizing plate 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, and a poly A film of at least one layer of the group consisting of an ester resin film and an acrylic resin film. 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/μm. on. The polarizing plate according to claim 1 or 2, wherein the adhesive layer has a peeling force of 10 N/25 mm or less when subjected to a 180-degree peeling test. A liquid crystal display device comprising a liquid crystal panel in which a polarizing plate according to any one of claims 1 to 7 is laminated on a liquid crystal cell via the above-mentioned adhesive layer.