TW201739626A - Method for producing polarizing plate - Google Patents

Abstract

A method for producing polarizing plate of this invention is capable of suppressing decrease in degree of polarization due to displacement of absorption axis of polarizing film caused by dimensional change of optical film during heat resistance test. The method for producing polarizing plate of the present invention includes an optical film, a polarizing film and an adhesive layer in this order, wherein the thickness of the polarizing film is 15 [mu] m or less, the angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is about 45 DEG or about 135 DEG, wherein, the method comprising a step of heat-treating the optical film before laminating the optical film to the polarizing film.

Description

Polarizing plate manufacturing method

The present invention relates to a method of manufacturing a polarizing plate.

In recent years, light-weight and thin liquid crystal displays that consume low power and operate at low voltage have rapidly spread as information display devices such as mobile phones, mobile information terminals, monitors for computers, and televisions. With the development of liquid crystal technology, liquid crystal displays of various modes have been proposed, and problems such as response speed or contrast, narrow viewing angle liquid crystal displays have been gradually solved. Moreover, with the spread of liquid crystal displays for mobile use, for example, when used outdoors, there is a case where the liquid crystal display is recognized by wearing polarized sunglasses. In this case, the liquid crystal display also requires that even through polarized sunglasses. Seeing the picture, the recognition is also excellent.

There have been some proposals for improving the visibility at the time of viewing a picture through polarized sunglasses (Patent Documents 1 to 9).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-122454

[Patent Document 2 Japanese Patent Laid-Open Publication No. 2011-107198

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2011-215646

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2012-230390

[Patent Document 5] Japanese Patent Laid-Open Publication No. 03-174512

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2013-231761

[Patent Document 7] Japanese Laid-Open Patent Publication No. 2011-113018

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2013-182162

[Patent Document 9] Japanese Patent Laid-Open Publication No. 2013-200445

The method for improving the visibility when viewing a screen through polarized sunglasses is to convert a linear polarized light emitted from a polarizing plate disposed on an identification side of an image display element such as a liquid crystal cell into an elliptical (or circular) polarized phase. A method in which a differential plate (for example, a λ/4 wavelength plate) is disposed on the identification side of the above-described polarizing plate (Patent Documents 1 to 9).

However, such a phase difference plate is stretched and a large number of layers are laminated on the polarizing film directly via the adhesive layer. Further, the angle formed by the absorption axis of the polarizing plate and the slow axis of the phase difference plate is set to a predetermined angle (for example, 45°), and the phase difference plate which is extended during the heat resistance test is inclined in size, and the polarizing film is absorbed. The axis changes locally, and there is a problem that the degree of polarization is lowered.

[1] A method for producing a polarizing plate, comprising: an optical film, a polarizing film, and an adhesive layer, wherein the polarizing film has a thickness of 15 μm or less, and an absorption axis of the polarizing film and a slow axis of the optical film constitute an angle The degree is about 45° or about 135°, and the step of heat-treating the optical film before the optical film is bonded to the polarizing film.

[2] The method for producing a polarizing plate according to [1], wherein the heat treatment is performed at a temperature of from Tg -30 ° C to Tg - 5 ° C with respect to a glass transition temperature (Tg) of the optical film.

The method for producing a polarizing plate according to the above aspect, wherein the optical film is selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, and a polyester. At least one of a group consisting of a resin or a (meth)acrylic resin.

[4] The method for producing a polarizing plate according to any one of [1] to [3] wherein the polarizing film and the adhesive layer further have a protective film.

According to the present invention, it is possible to provide a method for producing a polarizing plate which can suppress a decrease in the degree of polarization caused by a shift in the absorption axis of the polarizing film caused by a change in the size of the optical film during the heat resistance test.

10‧‧‧Polar plate

11‧‧‧Optical film

14‧‧‧ polarizing film

15‧‧‧Protective film

16‧‧‧Adhesive layer

20‧‧‧Surface treatment layer

30‧‧‧Absorption axis of polarizing film

31‧‧‧The direction of the absorption axis of the polarizing film is 45°

32‧‧‧The direction of the absorption axis of the polarizing film is 135°

33‧‧‧45°

34‧‧‧135°

40‧‧‧Polarizer for measuring dimensional change rate

Fig. 1 is a view showing an example of a cross-sectional schematic view showing a layer configuration of a polarizing plate of the present invention.

Fig. 2 (a) and (b) show an example of a plan view showing the relationship between the axial directions in the polarizing plate obtained by the production method of the present invention.

Referring to Fig. 1, a description will be given of a manufacturing method by the present invention. The layer of the polarizing plate 10 is formed. The polarizing plate obtained by the production method of the present invention is preferably formed by sequentially laminating the optical film 11, the polarizing film 14, and the adhesive layer 16. The angle formed by the absorption axis of the polarizing film 14 and the slow axis of the optical film 11 is about 45 or about 135. The surface of the optical film 11 opposite to the bonding surface of the polarizing film may also be used to form the surface treatment layer 20.

Moreover, it is preferable that the optical film 11 contains at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth)acrylic resin. membrane.

The polarizing film 14 preferably has a thickness of 15 μm or less.

Further, according to the present invention, it is also possible to provide a polarizing plate 10 having a protective film 15 between the polarizing film 14 and the adhesive 16.

Hereinafter, the members relating to the method for producing a polarizing plate of the present invention will be described in detail.

[Polarizing film 14]

The polarizing film 14 can be usually produced by a step of uniaxially stretching a polyvinyl alcohol-based resin film, and dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye. a step of crosslinking a polyvinyl alcohol-based resin film having a dichroic dye adsorbed thereon with a boric acid aqueous solution; and a step of washing with a boric acid aqueous solution after cross-linking treatment.

The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be vinyl acetate and may be used in addition to the polyvinyl acetate of the homopolymer of vinyl acetate. a copolymer of other monomers copolymerized therewith. Other single systems which can be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

The degree of saponification of the polyvinyl alcohol-based resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, polyethylene formaldehyde or polyethylene acetal modified with an aldehyde may be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually from about 1,000 to 10,000, preferably from about 1,500 to 5,000.

Such a polyvinyl alcohol-based resin can be used as a film of a polarizing film. The method for forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. The film thickness of the polyvinyl alcohol-based resin embryo film is, for example, about 10 to 100 μm, preferably about 10 to 50 μm.

The uniaxial extension of the polyvinyl alcohol-based resin film can be carried out before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing, and when uniaxially stretching after dyeing, the uniaxial extension can be treated with boric acid It can also be carried out before the boric acid treatment. Of course, uniaxial stretching can also be performed at the plural stages shown here. The uniaxial stretching system may be a method in which a roller having a different circumferential speed is extended toward a single shaft, or a method in which a heat roller is used to extend toward a single shaft. Further, the uniaxial stretching system can be carried out by dry stretching in the air, or by stretching the polyvinyl alcohol resin film in a state in which the polyvinyl alcohol resin film is swollen by stretching using a solvent such as water. The stretching ratio is usually about 3 to 8 times.

The polyvinyl alcohol-based resin film can be dyed with a dichroic dye by, for example, impregnating a polyvinyl alcohol in an aqueous solution containing a dichroic dye. The method of the resin film is carried out. As the dichroic dye, specifically, iodine or a dichroic organic dye can be used. Moreover, it is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment of immersing in water and swelling it 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 solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and 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 solution used for dyeing is usually about 20 to 40 °C. Further, the immersion time (dyeing time) of the aqueous solution is usually about 20 to 1,800 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 an aqueous solution containing a water-soluble dichroic organic dye and dyed is usually used. The content of the dichroic organic dye in the aqueous solution is usually from about 1 × 10 ^-4 to 10 parts by weight, preferably from 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous solution of the dichroic organic dye used in the dyeing is usually about 20 to 80 °C. Further, the immersion time (dyeing time) of the aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be carried out by immersing the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The boric acid content in the aqueous solution containing boric acid is usually from 2 to 15 parts by weight, preferably from 5 to 12 weights per 100 parts by weight of water. Quantities. When iodine is used as the dichroic dye, it is preferred that the aqueous solution containing boric acid contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid is usually from 0.1 to 15 parts by weight, preferably from 5 to 12 parts by weight, per 100 parts by weight of water. The immersion time for the aqueous solution containing boric acid is usually from about 60 to 1,200 seconds, preferably from 150 to 600 seconds, more preferably from 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. 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 in the water washing treatment is usually about 5 to 40 °C. Further, the immersion time is usually about 1 to 120 seconds.

After washing with water, a drying treatment can be 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 from about 30 to 100 ° C, preferably from 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is lowered to a practical level. The moisture content is usually from about 5 to 20% by weight, preferably from 8 to 15% by weight. If the moisture content is lowered to 5% by weight, the flexibility of the polarizing film may be lost, and the film may be damaged or broken after drying. Moreover, when the water content exceeds 20% by weight, thermal stability tends to be insufficient.

As described above, the polarizing film 14 in which the dichroic dye is adsorbed on the polyvinyl alcohol-based resin film can be produced.

In order to suppress a decrease in the degree of polarization caused by the shift of the absorption axis of the polarizing film 14 caused by the dimensional change of the optical film 11, a polarizing film is preferred. The contraction force of 14 itself is also set low, and the present invention uses a polarizing film having a thickness of 15 μm or less. In order to further reduce the contraction force of the polarizing film 14, it is preferable that the thickness of the polarizing film 14 is 12 μm or less. The point of the polarizing film is usually 3 μm or more in terms of imparting good optical characteristics.

[Optical film 11]

In the polarizing plate used in the present invention, the optical film 11 is particularly excellent in materials such as transparency, mechanical strength, thermal stability, and moisture shielding properties. For example, a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (such as a decene-based resin); for example, cellulose triacetate or cellulose II; Cellulose resin such as cellulose ester resin of acetate; polyester resin; polycarbonate resin; (meth)acrylic resin; polystyrene resin; or mixtures thereof, copolymers, etc. .

Preferably, the optical film 11 satisfies the following formula: (1) 100 nm ≦R _e (590) ≦ 180 nm, (2) 0.5 < R _th (590) / R _e (590) ≦ 0.8, (3) 0.85 ≦ A film of R _e (450) / R _e (550) < 1.00, and (4) 1.00 < R _e (630) / R _e (550) ≦ 1.1. In the formula, R _e (590), R _e (450), R _e (550), and R _e (630) represent the in-plane retardation values of the measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively, R _th (590 The system indicates the thickness direction phase difference value in the measurement wavelength of 590 nm. These in-plane phase difference values and thickness direction phase difference values were measured in an environment of a temperature of 23 ° C and a relative humidity of 55%.

The in-plane retardation value R _e and the thickness direction retardation value R _th of the optical film 11 are such that the refractive index in the in-plane slow axis direction is n _x and the in-plane fast axis direction (direction orthogonal to the in-plane slow axis direction). When the refractive index is n _y , the refractive index in the thickness direction is n _z , and the thickness of the optical film 11 is d, the following formula is used: R _e = (n _{x -} n _y ) × d R _th = [{(n _x + n _y )/2}-n _z ]×d is defined.

The optical film 11 which exhibits the phase difference characteristics and the wavelength dispersion characteristics of the above formulas (1) to (4) is disposed on the liquid crystal display on the identification side, and can effectively suppress the directions (azimuth and polar angle) from the polarized sunglasses. The color tone changes when viewing the screen, and the recognition of the liquid crystal display can be improved. On the other hand, when any one of the above formulas (1) to (4) is not satisfied, the above-described suppression of the color tone change may be insufficient.

From the viewpoint of more effectively suppressing the change in color tone, R _e (590) in the formula (1) is preferably from 105 to 170 nm, and R _th (590) / R _e (590) in the formula (2) is preferably from 0.6 to 0.75, R _e (450) / R _e (550) in the formula (3) is preferably 0.86 to 0.98, and R _e (630) / R _e (550) in the formula (4) is preferably 1.01 to 1.06.

The optical film 11 has one type of retardation film that converts linearly polarized light emitted from the polarizing film 14 toward the optical film 11 into elliptically polarized light (including circular polarized light), and exhibits this function as an absorption axis of the polarizing film. The angle formed by the slow axis of the optical film is laminated to be about 45 or about 135. When the angle of the configuration is outside this range, the function of converting the linearly polarized light into the elliptically polarized light cannot be obtained, and as a result, the above-described suppression of the color tone change may be insufficient. The angle of constitution is preferably 35 to 55 or 125 to 145, more preferably 40 to 50 or 130 to 140.

Since the phase difference characteristics and the wavelength dispersion characteristics of the above formulas (1) to (4) are easily imparted, and the moisture permeability and the moist heat resistance of the optical laminate are improved due to the low moisture permeability, the optical film 11 is preferably The cyclic polyolefin resin, the polycarbonate resin, the cellulose resin, the polyester resin, or the (meth)acrylic resin, or two or more thereof, and more preferably the resin component is selected from the group consisting of One or more of the components.

The chain-like polyolefin resin is a homopolymer of a chain olefin of a polyethylene resin or a polypropylene resin, and examples thereof include a copolymer composed of two or more kinds of chain olefins.

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene or propylene ( Representative examples are random copolymers, and graft polymers which have been modified with unsaturated carboxylic acids or derivatives thereof, and the like, and the like. Among them, a norbornene-based resin using a norbornene-based monomer such as a norbornene or a polycyclic norbornene-based monomer as a cyclic olefin is preferable.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Further, it is also possible to use such a copolymer or a part of a hydroxyl group to be modified with another substituent. Among these, cellulose triacetate (triethyl fluorenyl cellulose: TAC) is particularly preferred.

A polyester resin is a resin having an ester bond, generally consisting of A polycarboxylic acid or a derivative thereof and a polycondensate of a polyol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalene dicarboxylate. . As the polyol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polytrimethylene terephthalate. Ester, propylene naphthalate, dimethyl dimethyl terephthalate, cyclohexane dimethyl phthalate.

The polycarbonate resin is composed of a polymer bonded to a monomer unit via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate such as a polymer skeleton, or a copolymerized polycarbonate.

The (meth)acrylic resin is a resin having a compound having a (meth)acryl fluorenyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-( Methyl) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of a compound of an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl (meth) acrylate), and the like. It is preferred to use a polymer having a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate as a main component, and more preferably methyl methacrylate as a main component (50). To 100% by weight, preferably 70 to 100% by weight, based on the methyl methacrylate resin.

The optical film 11 can be produced by stretching a film containing the above thermoplastic resin. The stretching treatment may be, for example, uniaxial stretching or biaxial stretching. The direction of extension may be, for example, a mechanical movement direction (MD) of the unstretched film, a direction orthogonal thereto (TD), a direction oblique to the mechanical movement direction (MD), and the like. The two-axis extension system may be a two-axis extension extending simultaneously in two extending directions, or may be a two-axis extension extending in a predetermined direction and extending in other directions. The extension processing system may use, for example, a nip roller that increases the peripheral speed of the outlet side by 2 or more, and extends in the longitudinal direction (mechanical movement direction: MD), or the both ends of the unstretched film are held by the chuck. The mechanical movement direction is orthogonal to the direction (TD) extension. At this time, by adjusting the thickness of the film or adjusting the stretching ratio, the phase difference value and the wavelength dispersion can be controlled within the range of the above formulas (1) to (2). Further, by adding a wavelength dispersion adjusting agent to the resin, the wavelength dispersion value can be controlled within the range of the above formulas (3) to (4).

The thickness of the optical film 11 is not particularly limited as long as the above formulae (1) to (4) are sufficient. From the viewpoint of film formation of the polarizing plate, it is preferably 90 μm or less, more preferably 60 μm or less. From the viewpoint of workability, it is preferably 5 μm or more, and more preferably 10 μm or more.

According to the manufacturing method of the present invention, since the optical film 11 is subjected to heat treatment, even if the ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is 1.5 or more, or 3 or more, The decrease in the degree of polarization is effectively suppressed. Generally, the ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is 10 or less.

The optical film 11 may contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.

Further, in order to impart desired surface optical characteristics or other characteristics, a coating layer (surface treatment layer 20) may be provided on the outer surface of the optical film 11. Specific examples of the coating layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. The method of forming the coating layer is not particularly limited, and a known method can be used.

[Protective film 15]

The excellent protective film 15 is made of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and the like. The protective film 15 is preferably a cellulose resin, a polyolefin resin, or an acrylic resin, since it is easy to control the retardation value. The polyolefin resin as used herein includes a chain polyolefin resin and a cyclic polyolefin resin.

A cellulose resin, an environmental olefin resin, or an acrylic resin can be used in the same manner as the user of the above optical film.

The method of producing a film from the above resin may be a method of appropriately selecting a resin according to the respective resins. For example, a solvent casting method, a melt extrusion method, or the like described above may be employed. Among them, the polyolefin resin or the acrylic resin is preferably a melt extrusion method from the viewpoint of productivity. On the other hand, the cellulose resin is generally a film formed by a solvent casting method.

The liquid crystal cell is driven by a transverse electric field (IPS: In-Plane) In the Switching mode, in order to not damage the wide viewing angle characteristics of the liquid crystal cell of the IPS mode, the transparent protective film preferably has a phase difference Rth in the thickness direction of -10 to 10 nm.

The method of controlling the phase difference Rth in the thickness direction of the transparent protective film to be in the range of -10 to 10 nm is, for example, a method of reducing the deformation remaining in the in-plane and thickness directions as much as possible in the production of the film. For example, in the solvent casting method, a method in which the residual shrinkage deformation in the in-plane and thickness directions generated when the casting resin solution is dried can be alleviated by heat treatment. On the other hand, in the above melt extrusion method, in order to prevent the resin film from being stretched from the die to the cooling, the distance from the die to the cooling drum can be minimized, and the amount of extrusion and the cooling drum can be controlled. The method of rotating the speed to prevent the film from being stretched. Further, similarly to the solvent casting method, a method of alleviating the deformation of the obtained film by heat treatment may be employed.

[Adhesive layer, adhesive layer]

The bonding of the polarizing film and the optical film and the bonding of the polarizing film and the protective film can be carried out by an adhesive or an adhesive.

The adhesive layer for bonding the polarizing film and the optical film and the adhesive layer for bonding the polarizing film and the protective film may have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, more preferably 0.05 to 5 μm. When the thickness of the adhesive layer is in this range, floating or peeling does not occur between the laminated polarizing film and the optical film and the protective film and the polarizing film, and an adhesive force which is practically problem-free can be obtained. When the adhesive layer is used, the adhesive layer may have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, more preferably 10 to 25 μm.

When the polarizing film is bonded to the optical film and the polarizing film and the protective film are bonded to each other, the polarizing film, the optical film, and the protective film may be subjected to saponification treatment, corona treatment, plasma treatment, or the like.

The formation of the subsequent layer may suitably use an appropriate adhesive depending on the kind or purpose of the adherend, and an anchor coating agent may be used as needed. Examples of the adhesive agent include a solvent-based adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet adhesive, a polycondensation adhesive, a solventless adhesive, a film adhesive, and a hot melt adhesive. Wait.

One of the preferred adhesives is, for example, a water-based adhesive, that is, an adhesive component which is dissolved or dispersed in water. For example, a polyvinyl alcohol-based resin is used as an example of an adhesive component soluble in water. Further, as an example of an adhesive component which can be dispersed in water, for example, a urethane-based resin having a hydrophilic group is used. The water-based adhesive can be prepared by mixing an additional additive such as such an adhesive component as needed, and mixing it in water. An example of a commercially available polyvinyl alcohol-based resin which can be used as a water-based adhesive is "KL-318" which is a carboxylated polyvinyl alcohol sold from Kuraray Co., Ltd., and the like.

The aqueous binder may contain a crosslinking agent as needed. Examples of the crosslinking agent include an amine compound, an aldehyde compound, a methylol compound, a water-soluble epoxy resin, an isocyanate compound, a polyvalent metal salt, and the like. When a polyvinyl alcohol-based resin is used as the adhesive component, an aldehyde compound typified by glyoxal, a methylol compound typified by methylol melamine, a water-soluble epoxy resin or the like is preferably used as the crosslinking agent.

Here, the water-soluble epoxy resin may be, for example, such as diethylenetriamine or tri A polyamine amine polyamine obtained by reacting ethylene tetraamine with a reaction product of an alkyl polyamine and a dicarboxylic acid such as adipic acid, and a polyamine epoxy resin obtained by reacting with epichlorohydrin. For example, "Sumirez resin (registered trademark) 650 (30)" sold from the company of Tiangang Industrial Co., Ltd., for example, is a commercially available product of a water-soluble epoxy resin.

A water-based adhesive can be applied to the polarizing film and/or the surface of the optical film or the protective film bonded thereto, and after the two are bonded together, a drying treatment can be applied to obtain a polarizing plate. Before the next step, the protective film is subjected to an easy subsequent treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment, and it is also effective to improve the wettability in advance. The drying temperature may be, for example, about 50 to 100 °C. After the drying treatment, the temperature is slightly higher than the room temperature, for example, at a temperature of about 30 to 50 ° C for about 1 to 10 days, and it is preferable to further increase the adhesion.

As another preferable adhesive agent, for example, a curable adhesive composition containing an epoxy compound which is cured by irradiation with an active energy ray or heating can be mentioned. Here, the curable epoxy compound is one having at least two epoxy groups in the molecule. At this time, the adhesion between the polarizing film and the protective film is performed by irradiating the coating layer of the adhesive composition with an active energy ray or imparting heat, and curing the curable epoxy compound contained in the adhesive. The hardening of the epoxy compound is generally carried out by cationic polymerization of an epoxy compound. Further, from the viewpoint of productivity, the hardening is preferably carried out by irradiation with an active energy ray.

From the viewpoints of weather resistance, refractive index, cationic polymerizability and the like, the epoxy compound contained in the curable adhesive composition preferably contains no aromatic ring in the molecule. As an epoxidized ring containing no aromatic ring in the molecule Examples of the compound include a hydrogenated epoxy compound, an alicyclic epoxy compound, and an aliphatic epoxy compound. An epoxy compound which is preferably used in such a hardenable adhesive composition is described in detail in, for example, Japanese Laid-Open Patent Publication No. 2004-245925, but is also briefly described herein.

The hydrogenated epoxy compound can be obtained by selectively hydrogenating a polyhydroxy compound obtained by subjecting an aromatic polyhydroxy compound of a raw material of an aromatic epoxy compound to a nuclear hydrogenation reaction in the presence of a catalyst and under pressure. The propyl group is formed. Examples of the aromatic polyhydroxy compound of the raw material of the aromatic epoxy compound include bisphenol A, bisphenol F, and bisphenol S bisphenols; for example, phenol novolak resin, cresol novolak resin, and hydroxybenzene A novolac type resin of a formaldehyde phenol novolak resin; a polyfunctional compound such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. The aromatic hydrogenation reaction of the aromatic polyhydroxy compound is carried out to react the obtained nuclear hydrogenated polyhydroxy compound with epichlorohydrin, whereby the epoxypropyl etherification can be carried out. A suitable hydrogenated epoxy compound is, for example, a hydrogenated bisphenol A epoxidized propyl ether.

The alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in the molecule. The "epoxy group bonded to the alicyclic ring" means an oxygen atom -O- which is crosslinked in the structure shown by the following formula, wherein m is an integer of 2 to 5.

A compound in a form in which one or a plurality of hydrogen atoms in (CH ₂ ) _m in the formula is bonded to another chemical structure can be used as an alicyclic epoxy compound. Further, one or a plurality of hydrogen atoms of (CH ₂ ) _m forming an alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an epoxycyclopentane ring (m=3 in the above formula) or an epoxycyclohexane ring (m=4 in the above formula) It shows excellent adhesion and is therefore preferred. Specific examples of the alicyclic epoxy compound are disclosed below. Here, the compound name is listed first, and thereafter, the chemical name corresponding to each chemical formula is shown, and the compound name is given the same reference numeral as the chemical formula corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy -6-methylcyclohexanecarboxylate, C: ethylene bis(3,4-epoxycyclohexanecarboxylate), D: bis(3,4-epoxycyclohexylmethyl)adipate , E: bis(3,4-epoxy-6-methylcyclohexylmethyl)adipate, F: diethylene glycol bis(3,4-epoxycyclohexylmethyl ether), G: Ethylene glycol bis(3,4-epoxycyclohexylmethyl ether), H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxaspiro[5.2.2.5 .2.2] Eicosane, I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-dioxaspiro[5.5]undecane, J:4- Vinyl cyclohexene dioxide, K: limonene dioxide, L: bis(2,3-epoxycyclopentyl)ether, M: dicyclopentadiene dioxide, and the like.

The aliphatic epoxy compound may be a polyepoxypropyl ether of an aliphatic polyol or an alkylene oxide adduct thereof. Further systems include, for example, diglycidyl ether of propylene glycol; diepoxypropyl ether of 1,4-butanediol; diepoxypropyl ether of 1,6-hexanediol; a propyl ether; a tri-glycidyl ether of trimethylolpropane; an addition of an alkylene oxide such as ethylene glycol, propylene glycol, and glycerol to an alkylene oxide (ethylene oxide or propylene oxide) A polyepoxypropyl ether of an ether polyol (for example, a diepoxypropyl ether of polyethylene glycol) or the like.

In the curable adhesive composition, the epoxy compound may be used alone or in combination of two or more. Among them, the epoxy compound preferably contains an alicyclic epoxy compound having at least one epoxy group bonded to the alicyclic ring in the molecule.

The epoxy compound used in the composition of the curable adhesive usually has an epoxy equivalent in the range of 30 to 3,000 g/eq, and the epoxy equivalent is preferably in the range of 50 to 1,500 g/eq. When an epoxy compound having an epoxy equivalent of less than 30 g/equivalent is used, there is a possibility that the flexibility of the polarizing plate after hardening is lowered, or the strength is lowered. On the other hand, in the compound having an epoxy equivalent of more than 3,000 g/eq, the compatibility with other components contained in the adhesive composition may be lowered.

From the viewpoint of reactivity, cationic polymerization is preferably used as the hardening reaction of the epoxy compound. Therefore, the curable adhesive composition containing an epoxy compound is preferably formulated with a cationic polymerization initiator. The cationic polymerization initiator activates the polymerization of an epoxy group by irradiation or heating of visible light rays, ultraviolet rays, X-rays, and an active energy ray of an electron beam to produce a cationic species or a Lewis acid. From the point of view of workability The sub-polymerization initiator is preferred to the latent person. Hereinafter, a cationic species or Lewis acid is generated by irradiation of an active energy ray, and a cationic polymerization initiator which initiates polymerization of an epoxy group is referred to as a "photocationic polymerization initiator", and a cationic species is generated by heat or The Lewis polymerization agent, a cationic polymerization initiator which initiates polymerization of an epoxy group, is called a "thermal cationic polymerization initiator".

The photocationic polymerization initiator is used to harden the adhesive composition by irradiation with an active energy ray, which can be hardened under normal temperature and humidity, and the necessity of heat resistance or deformation due to expansion of the polarizing film is reduced. It is advantageous to make the protective film and the polarizing film follow well. Further, since the photocationic polymerization initiator acts as a catalyst by light, it is excellent in storage stability and workability even when it is mixed with an epoxy compound.

The photocationic polymerization initiator may, for example, be an aromatic diazonium salt; an aromatic iodonium salt or an aromatic sulfonium salt sulfonium salt or an iron-propadiene complex compound. The compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, more preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound.

When the amount of the photocationic polymerization initiator is less than 0.5 part by weight based on 100 parts by weight of the epoxy compound, the curing is insufficient, and the mechanical strength and the subsequent strength of the cured product tend to be lowered.

On the other hand, when the amount of the photocationic polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, and the hygroscopic property of the cured product becomes high and durable. Performance is reduced.

When a photocationic polymerization initiator is used, the curable adhesive composition may further contain a photosensitizer as needed. Use photosensitizer to improve The reactivity of cationic polymerization increases the mechanical strength and subsequent strength of the cured product. The photosensitizer may, for example, be a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo compound, a diazo compound, a halogen compound or a photoreductive dye. When the photosensitizer is formulated, the amount thereof is preferably in the range of 0.1 to 20 parts by weight based on 100 parts by weight of the curable adhesive composition. Further, in order to increase the curing speed, a photo-sensitizer of a naphthoquinone derivative can also be used.

On the other hand, the thermal cationic polymerization initiator may, for example, be a benzyl sulfonium salt, a thiophenyl sulfonium salt, a thiolanium salt, a benzyl ammonium salt, a pyridinium salt, a hydrazine salt, or a carboxy group. Acid esters, sulfonates, amine imines, and the like.

The curable adhesive composition containing an epoxy compound is preferably cured by photocationic polymerization as described above, or the above-mentioned thermal cationic polymerization initiator may be present and hardened by thermal cationic polymerization. Photocationic polymerization and thermal cationic polymerization can also be used in combination. When photocationic polymerization and thermal cationic polymerization are used, it is preferred to contain both a photocationic polymerization initiator and a thermal cationic polymerization initiator in the curable adhesive composition.

Further, the curable adhesive composition may further contain a compound which promotes cationic polymerization such as an oxycyclobutane compound or a polyol compound. The oxycyclobutane compound is a compound having a 4-membered cyclic ether in the molecule. When the oxygenated cyclobutane compound is blended, the amount thereof is usually from 5 to 95% by weight, preferably from 5 to 50% by weight, based on the composition of the curable adhesive. Further, the polyol compound may be an alkanediol containing ethylene glycol, hexanediol, polyethylene glycol or the like. Or an oligomer thereof, a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol, or the like. When the polyol compound is blended, the amount thereof is usually 50% by weight or less, preferably 30% by weight or less, based on the curable adhesive composition.

Further, the adhesive agent may be a composition containing a radically polymerizable (meth)acrylic compound. The (meth)acrylic compound may, for example, be a (meth) acrylate monomer having at least one (meth) propylene fluorenyloxy group in the molecule; and reacting two or more kinds of compounds containing a functional group, A (meth)acryloxy group-containing compound such as a (meth) acrylate oligomer having at least two (meth) acryloxy groups in the molecule.

At this time, the adhesive preferably contains a photoradical polymerization initiator. The photoradical polymerization initiator may, for example, be an acetophenone-based initiator, a benzophenone-based initiator, a benzoin ether-based initiator, a thioxanthone-based initiator, or oxonone. Anthrone, camphorquinone, benzaldehyde, anthraquinone, etc.

Further, the adhesive agent may contain other additives as long as it does not impair its adhesion, such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, flow regulators, plasticizers. , defoamer, etc. The ion scavenger may, for example, be a powdery lanthanum, lanthanide, magnesium, aluminum, calcium, or titanium, or an inorganic compound containing such a mixed system, and the antioxidant may, for example, be a hindered phenol antioxidant. .

After the adhesive is applied to the adhesive film or the adhesive film or the adhesive film, the adhesive is applied to the coated surface, and the uncured adhesive is irradiated by the active energy ray or heating. The layer is hardened to allow the polarizing film to adhere to the protective film (or optical film). The coating method of the subsequent agent can be, for example, a doctor blade, a wire bar, a die coater, a notch applicator, a gravure Various coating methods such as applicators.

The curable adhesive composition can be basically used as a solvent-free adhesive which is substantially free of a solvent. However, since each coating method has various optimum viscosity ranges, the viscosity can be adjusted to contain a solvent. The solvent is preferably such that the optical performance of the polarizing film is not lowered, and the organic solvent containing each component of the epoxy compound is satisfactorily dissolved. For example, a hydrocarbon containing toluene, an ester containing ethyl acetate, or the like can be used.

When the adhesive composition is cured by the irradiation of the active energy ray, the active energy ray system can be used in the prior art. However, since the operability is easy, the control of the amount of the illuminating light or the like is easy to handle, so that it is preferable to use ultraviolet rays. The intensity of the active energy ray, for example, ultraviolet ray, and the amount of irradiation are in a range that does not affect various optical properties including the degree of polarization of the polarizing film and various optical properties including the transparency or phase difference characteristics of the protective film to maintain moderateness. The mode of production is appropriately determined.

When the adhesive composition is hardened by heat, it can be heated by a generally known method. Usually, the thermal cationic polymerization initiator blended in the curable adhesive composition is heated at a temperature above which a cationic species or a Lewis acid is generated, and the specific heating temperature is, for example, about 50 to 200 °C.

[Adhesive layer 16]

The adhesive layer 16 formed on the opposite side of the bonding surface of the protective film 15 and the polarizing film 14 is used to bond the polarizing plate to the adhesive layer of the liquid crystal cell, as long as it contains excellent optical transparency and moderateness. Wettability, condensation It is preferable that the adhesive property such as collectability and adhesion is excellent, and it is preferable that it is excellent in durability, etc. Specifically, the adhesive which forms the adhesive layer 16 is an adhesive (acrylic adhesive) containing an acrylic resin. good.

The acrylic resin contained in the acrylic adhesive is a resin containing, for example, butyl acrylate, ethyl acrylate, isooctyl acrylate, and alkyl acrylate of 2-ethylhexyl acrylate as a main monomer. In this acrylic resin, a polar monomer is usually copolymerized. The polar single system has a polymerizable unsaturated bond and a polar functional group. Here, the polymerizable unsaturated bond is generally derived from a (meth) acrylonitrile group, and the polar functional group may be a carboxyl group. Hydroxy, amidino, amine, epoxy, and the like. Specific examples of the polar monomer include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, and (meth)acrylamide, 2 -N,N-dimethylaminoethyl (meth) acrylate, epoxy propyl (meth) acrylate, and the like.

Further, an acrylic adhesive is usually formulated with a crosslinking agent together with an acrylic resin.

Representative examples of the crosslinking agent include, for example, an isocyanate compound having at least two isocyanato groups (-NCO) in the molecule.

Various additives can be formulated in the adhesive system. Suitable additives are, for example, a decane coupling agent or an antistatic agent. The decane coupling agent is effective in increasing the adhesion to the glass. Antistatic agents are effective in reducing or preventing the occurrence of static electricity.

The adhesive layer 16 is an adhesive composition prepared by dissolving the above adhesive component in an organic solvent, and can be directly coated by the adhesive. a method of drying a solvent on either or both sides of a subsequent bonding surface (polarizing film or protective film), or a release-treated surface of a substrate film formed by a resin film subjected to release treatment The above-described adhesive composition is applied, and the solvent is dried and removed to form an adhesive layer, which is attached to either surface of the bonding surface (polarizing film or protective film) and formed by transferring the adhesive layer. When the adhesive layer 16 is formed by the direct coating method of the former, the resin film (also referred to as a separation film) subjected to the release treatment is attached to the surface thereof, and the surface of the adhesive layer is temporarily protected when used. For the general case. From the viewpoint of the handleability of the adhesive composition of the organic solvent solution, the latter transfer method is often used, and in this case, the release-treated base film which is initially used for the formation of the adhesive layer is attached to the polarized light. After the plate, it can be directly used as a separation membrane, which is preferable.

In the heat resistance test, in order to ensure sufficient adhesion or dimensional stability, it is preferred that the storage modulus of the adhesive at 80 ° C is 5 MPa or less. More preferably, it is 1 MPa or less.

When the protective film 15 and the adhesive layer 16 are bonded together, it is also useful to perform corona treatment, plasma treatment, or the like on the surface of the protective film 15 and the adhesive layer 16, respectively.

[Method of Manufacturing Polarizing Plate]

The method of producing the polarizing plate is not particularly limited. For example, the optical film 11, the polarizing film 14, and the protective film 15 are passed through the adhesive layer and bonded to each other by a roll to a roll, whereby the polarizing plate 10 can be obtained. Further, the adhesive layer 16 is formed on the protective film 15, and a polarizing plate with an adhesive can be obtained. Polarizing plate with adhesive The adhesive layer 16 is adhered to the liquid crystal cell.

Since the optical film 11 is provided with a desired phase difference characteristic and is subjected to a large amount of stretching treatment, for example, the dimensional change may be large when placed in a high-temperature environment such as 85 ° C. Therefore, the manufacturing method of the present invention includes a step of heat-treating the optical film 11 before bonding the optical film 11 and the polarizing film 14. Further, in the stage of manufacturing the optical film 11, there is a case where the film is heated during the stretching treatment, but the step of performing the heat treatment in the manufacturing method of the present invention is different from the heating in the stretching treatment, and the stretching treatment is performed. The optical film after the end is subjected to heat treatment. That is, in the step of performing the heat treatment in the production method of the present invention, the optical film is not substantially extended. The fact that it is not substantially extended means that the stretching ratio is 1.1 times or less, preferably 1.05 times or less.

The step of performing the heat treatment is preferably carried out within 3 days of bonding the optical film 11 and the polarizing film 14, and it is preferably carried out within 24 hours, and more preferably within 60 minutes. In this manner, a heating step is provided before the bonding, and wrinkles due to the pressure-bonding of the optical film 11 can be corrected, and a polarizing plate excellent in appearance quality can be formed.

The heat treatment is preferably carried out with respect to the glass transition temperature (Tg) of the optical film 11, preferably at a temperature of from Tg - 60 ° C to Tg ° C, and at a temperature of from Tg -30 ° C to Tg - 5 ° C. good. More preferably, it is Tg-20 ° C to Tg - 5 ° C. Through such a heat treatment step, the dimensional change of the optical film 11 in a high temperature environment can be suppressed. Therefore, it is considered that the degree of polarization of the polarizing plate in the heat resistance test can be suppressed from being lowered.

The method of heat treatment can be pre-advanced by oven or the like. Various methods such as a method of heat treatment or a method of heating and holding a hot drum before bonding with a polarizing film.

The polarizing plate produced in this manner can also have a dimensional change ratio D1 of 45° in the direction of the absorption axis of the polarizing film and a direction of 135° with the absorption axis of the polarizing film when it is allowed to stand for 100 hours in an environment of 85° C. The dimensional change rate D2 is 0.25% or less, and the decrease in the degree of polarization during the heat resistance test can be suppressed.

[Examples]

The invention is illustrated by the following examples, but the invention is not limited by the examples. In the examples, the parts and % indicating the content or the amount used are based on weight unless otherwise specified. Further, the measurement of each physical property in the following examples was carried out in the following manner.

(1) Determination of thickness:

It was measured using a Digital Micrometer "MH-15M" manufactured by Nikon Co., Ltd.

(2) Determination of in-plane retardation and thickness direction delay:

The phase difference meter "KOBRA (registered trademark) - WPR" based on the parallel Nicols rotation method manufactured by Oji Scientific Instruments Co., Ltd. was used to measure the in-plane retardation and thickness at a predetermined wavelength at a temperature of 23 ° C. The direction is delayed.

(3) Determination of the degree of polarization and monomer transmittance of the polarizing plate:

Using a spectrophotometer with an integrating sphere [Japan Separation Co., Ltd. The measurement was performed by "V7100", 2 degree field of view, and C light source.

(4) Method for measuring dimensional change rate of polarizing plate

The dimensional change rate D1 of the polarizing plate in the direction in which the absorption axis of the polarizing film was 45° when it was allowed to stand for 100 hours in an environment of 85° C., and the change in the size of the polarizing plate in the direction in which the absorption axis of the polarizing film was 135° were measured. The method of the rate D2 was measured using the two-dimensional measuring instrument "NEXIV VMR-12072" manufactured by NIKON Co., Ltd. as follows. First, the polarizing plate is cut into the absorption axis of the polarizing film (100 mm in the direction of 45°) × (100 mm in the direction of 135 ° C), and is allowed to stand for 1 day in an environment of a temperature of 23 ° C and a humidity of 55%. The dimension (L0 (45)) in the direction of the absorption axis of the polarizing film in the direction of 45° and the dimension (L0 (135)) in the direction of 135° from the absorption axis of the polarizing film were measured. Next, the polarizing plate was allowed to stand in an environment of 85 ° C for 100 hours, and the size (L1 (45)) in the direction of the absorption axis of the polarizing film after standing in a high temperature environment and absorption with the polarizing film was measured. The shaft has a dimension of 135° (L1 (135)). As a result, dimensional change rates D1 (%) and D2 (%) were obtained from the equations (5) and (6).

Dimensional change rate D1=[(L0(45)-L1(45))/L0(45)]×100 (5)

Dimensional change rate D2=[(L0(135)-L1(135))/L0(135)]×100 (6)

[Manufacturing Example 1] Production of polarizing film

A polyvinyl alcohol film having a thickness of 20 μm (having an average degree of polymerization of about 2400 and a degree of saponification of 99.9 mol% or more) was subjected to dry stretching for about 4 times of uniaxial stretching, and further immersed in pure water at 40 ° C in a state of maintaining tension. After 40 seconds, the weight ratio of immersion in iodine/potassium iodide/water at 28 ° C was 0.052/5.7/100. The dyeing treatment was carried out for 30 seconds in the aqueous solution. Thereafter, it was immersed in an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 11.0/6.2/100 at 70 ° C for 120 seconds. Then, after washing with pure water of 8 ° C for 15 seconds, it was dried at 60 ° C for 50 seconds while being held at a tension of 300 N, and then dried at 75 ° C for 20 seconds to obtain a directional iodine adsorbed on the polyvinyl alcohol film. An absorption type polarizer having a thickness of 7 μm.

[Production Example 2] Production of a water-based adhesive

3 parts by weight of a carboxyl group-denatured polyvinyl alcohol [trade name "KL-318" obtained from Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water, and a water-soluble epoxy resin polyether amine epoxy system was added to the aqueous solution. The additive [Sumirez resin (registered trademark) 650 (30)" obtained from the company, which is obtained from the company, and the aqueous solution having a solid content of 30% by weight, was added in an amount of 1.5 parts by weight to prepare a water-based adhesive.

[adhesive]

Adhesive A: A sheet-like adhesive having a thickness of 25 μm [P-3132 manufactured by Lintech Co., Ltd.] was prepared.

[protective film]

Prepare the following protective film.

Protective film: a cyclic polyolefin resin film manufactured by Zeon Co., Ltd.; ZF14-013 (thickness: 13 μm, in-plane retardation at a wavelength of 590 nm = 0.5 nm, phase difference in thickness direction at a wavelength of 590 nm = 3.3 nm)

[Optical film]

Optical film A: Prepared a triethylenesulfonated cellulose film manufactured by Konica Minolta Co., Ltd.; KC4UGR-HC (thickness: 44 μm, in-plane retardation at a wavelength of 590 nm = 106 nm, phase difference in thickness direction at a wavelength of 590 nm = 75 nm, Rth (590) / Re (590) = 0.71, Re (450) / Re (550) = 0.96, Re (630) / Re (550) = 1.02, glass transition temperature = 200 ° C).

Optical film B: Prepared a cycloolefin polymer film manufactured by Zeon Co., Ltd.; ZD12-099063-C1330 UHD (thickness 28 μm, in-plane retardation at a wavelength of 590 nm = 97 nm, thickness direction at a wavelength of 590 nm = 65 nm) Rth(590)/Re(590)=0.67, Re(450)/Re(550)=1.01, Re(630)/Re(550)=0.99, glass transition temperature=120°C).

[Example 1]

The optical film A was placed in an oven at 150 ° C for 3 minutes, and heat treatment was performed. Then, the optical film A which has been subjected to heat treatment is subjected to saponification treatment. That is, the heat treatment temperature is Tg - 50 °C.

Corona treatment is performed on one side of the protective film. The corona-treated surface of the protective film and the polarizing film were further subjected to a polarizing film by further adhering the polarizing film and the optical film A with a water-based adhesive.

After the optical film A was heat-treated, the time until it adhered to the polarizing film was 30 minutes. At this time, the absorption axis of the polarizing plate was bonded to the slow axis of the optical film A to be 45°.

Further, on the protective film side of the obtained polarizing plate, the adhesive A is obtained. A polarizing plate comprising an adhesive layer composed of a layer of an optical film A/polarizing film/protective film/adhesive layer A is obtained.

The polarizing plate has a degree of polarization of 99.994%.

The dimensional change rates D1 and D2 of the obtained polarizing plate were D1 = 0.06% and D2 = 0.21%.

The polarizing plate produced in this manner was cut into a square of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.972%.

Similarly, the polarizing plate was cut out to a size of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 85 ° C for 500 hours. The degree of polarization after the heat resistance test was 99.975%.

[Embodiment 2]

The optical film A was placed in an oven at an ambient temperature of 200 ° C for 3 minutes, and heat treatment was performed. That is, the heat treatment temperature is equal to Tg. Then, the optical film A which has been subjected to heat treatment is subjected to saponification treatment. In the same manner as in Example 1, a polarizing plate comprising an adhesive layer composed of a layer of an optical film A/polarizing film/protective film/adhesive layer A was obtained. The polarizing plate of this polarizing plate is 99.995%.

The dimensional change rates D1 and D2 of the obtained polarizing plate were D1 = 0.05% and D2 = 0.15%.

Cut the polarizing plate made in this way to 40mm flat The film was bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.980%.

Similarly, the polarizing plate was cut out to a size of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 85 ° C for 500 hours. The degree of polarization after the heat resistance test was 99.981%.

[Example 3]

The optical film B was placed in an oven at 120 ° C for 3 minutes, and heat treatment was performed. That is, the heat treatment temperature is equal to Tg. Then, the optical film B which has been subjected to heat treatment is subjected to corona treatment. A polarizing plate comprising an adhesive layer of a layer of an optical film B/polarizing film/protective film/adhesive layer A was obtained in the same manner as in Example 1 except that the optical film B was used instead of the optical film A. The polarizing plate has a degree of polarization of 99.993%.

The dimensional change rates D1 and D2 of the obtained polarizing plate were D1 = 0.03% and D2 = 0.10%.

The polarizing plate produced in this manner was cut into a square of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.985%.

Similarly, the polarizing plate was cut out to a size of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 85 ° C for 500 hours. Heat test The post-test polarization was 99.987%.

[Comparative Example 1]

One side of the protective film was subjected to corona treatment, and the optical film A was subjected to saponification treatment. The corona-treated surface of the protective film, the polarizing film, and the optical film A were sequentially followed by a water-based adhesive to obtain a polarizing plate. The optical film A is not subjected to heat treatment until the polarizing film and the optical film A are bonded. The absorption axis of the obtained polarizing plate and the slow axis of the optical film were made 45°. Further, a pressure-sensitive adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain a polarizing plate comprising an adhesive layer composed of a layer of the optical film A/polarizing film/protective film/adhesive layer A. The polarizing plate has a degree of polarization of 99.995%.

The dimensional change rates D1 and D2 of the obtained polarizing plate were D1 = 0.07% and D2 = 0.30%.

The polarizing plate produced in this manner was cut into a square of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.954%.

Similarly, the polarizing plate was cut out to a size of 40 mm, and bonded to Eagle XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample prepared in this manner was placed in an oven at 85 ° C for 500 hours. The degree of polarization after the heat resistance test was 99.954%.

As shown in the above Table 1, the polarizing plates of Examples 1 to 3 which were subjected to the heat treatment of the optical film as compared with the polarizing plate of Comparative Example 1 which was not subjected to the heat treatment had a small decrease in the degree of polarization after the heat resistance test.

[Industry use possibility]

According to the present invention, it is possible to provide a method for producing a polarizing plate which is useful for suppressing a decrease in the degree of polarization caused by a shift in an absorption axis of a polarizing film due to a dimensional change of an optical film during a heat resistance test. .

10‧‧‧Polar plate

11‧‧‧Optical film

14‧‧‧ polarizing film

15‧‧‧Protective film

16‧‧‧Adhesive layer

20‧‧‧Surface treatment layer

Claims (4)

A method for producing a polarizing plate, comprising: an optical film, a polarizing film, and an adhesive layer, wherein the polarizing film has a thickness of 15 μm or less, and an absorption axis of the polarizing film and an optical axis of the optical film form an angle of about 45 ° or about 135°, wherein the optical film is heat-treated before the optical film is bonded to the polarizing film. The method for producing a polarizing plate according to the first aspect of the invention, wherein the heat treatment is performed at a temperature of from Tg -30 ° C to Tg - 5 ° C with respect to a glass transition temperature (Tg) of the optical film. The method for producing a polarizing plate according to claim 1 or 2, wherein the optical film comprises a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin or At least one of the group consisting of (meth)acrylic resins. The method for producing a polarizing plate according to any one of claims 1 to 3, wherein a protective film is further provided between the polarizing film and the pressure-sensitive adhesive layer.