JP2017083820A - Polarizing plate and liquid crystal panel, and manufacturing method of polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate that can be easily laminated on a liquid crystal cell despite its thinness, and a liquid crystal panel using the same.SOLUTION: There is provided a polarizing plate in a rectangular shape including, in this order, a surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer, wherein the angle formed by an absorption axis of the polarizing film and a slow axis of the optical film is 45±20° or 135±20°; in at least one pair of sides sharing an apex, of the four sides of a sheet, the difference in size between curls at both ends is 3 mm or more; the size of the curls at the apices is positive.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a polarizing plate, a liquid crystal panel using the polarizing plate, and a method for manufacturing a polarizing plate.

  In recent years, low-power consumption, low-voltage, light-weight and thin liquid crystal displays are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. With the development of liquid crystal technology, liquid crystal displays in various modes have been proposed, and problems with liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved. In addition, with the spread of mobile liquid crystal displays, thin and light liquid crystal panels are also required.

  Under such circumstances, thinning of the polarizing plate is strongly demanded, and the protective film of the polarizing film and the polarizing film are being thinned (for example, Patent Documents 1 to 3).

  However, since the rigidity of the polarizing plate has decreased with the thinning of the polarizing plate, when the polarizing plate is bonded to the liquid crystal cell, the polarizing plate is first applied to the liquid crystal panel at a portion other than the portion in contact with the bonding roll. In addition, when the bonding roll passes through the portion, there is a problem that an appearance defect due to deformation of the polarizing plate and a bright spot defect due to the entrapment of bubbles occur.

Japanese Patent Laying-Open No. 2015-079254 JP 2014-178364 A JP2013-008019A

  An object of the present invention is to provide a polarizing plate that can be easily bonded to a liquid crystal cell while being a thin-walled polarizing plate, and a liquid crystal panel using the polarizing plate.

[1] A rectangular polarizing plate including a surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer in this order,
The angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is 45 ± 20 ° or 135 ± 20 °,
A polarizing plate in which at least one set of four sides of a sheet has a difference in curl size between both ends of two sides sharing the apex is 3 mm or more, and the apex has a positive curl size.
[2] The polarizing plate according to [1], wherein a difference in curl size between one pair of vertices is 2 mm or less at the four vertices of the sheet.
[3] The polarizing plate according to [2], wherein the difference in curl between the other pair of apexes is 2 mm or less.
[4] The polarizing plate according to any one of [1] to [3], wherein the optical film includes a cellulose resin.
[5] The polarizing plate according to any one of [1] to [4], further including a transparent protective film between the polarizing film and the pressure-sensitive adhesive layer.
[6] A liquid crystal panel in which the polarizing plate according to any one of [1] to [5] is disposed on at least one surface of the liquid crystal cell.
[7] A surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer are included in this order,
A polarizing plate having an angle between the absorption axis of the polarizing film and the slow axis of the optical film of 45 ± 20 ° or 135 ± 20 °,
The manufacturing method of a polarizing plate including the process of storing in the environment whose temperature is 18-27 degree | times and humidity is 30-70% RH.
[8] The method for producing a polarizing plate according to claim 7, wherein the length of the storing step is 30 minutes to 30 days.

  According to the present invention, it is possible to provide a polarizing plate that can be bonded without causing appearance defects or bright spot defects even when a thinned polarizing plate is bonded to a liquid crystal cell.

It is an example of the top view when a polarizing plate is cut out to a defined shape. It is an example of the top view which shows the preferable curl form which the polarizing plate of this invention has. It is the perspective view which showed the method of measuring the amount of curls in this invention. It is the schematic which shows the axial structure of the polarizing plate in an Example.

  The polarizing plate of the present invention comprises a surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer in this order. The angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is 45 ± 20 ° or 135 ± 20 °, and shares at least the apex among the four sides of the sheet body obtained by cutting the polarizing plate into a rectangle 2 The difference in curl size between both ends of the side is 3 mm or more. In addition, it is preferable that the size of the vertex curl is positive, and the size of the vertex curl that does not share a side with the vertex is also positive. Usually, in this field, curling of a polarizing plate has been regarded as something to be avoided, but surprisingly, when the polarizing plate is bonded to a liquid crystal cell by giving the above-mentioned curling characteristics to the polarizing plate. In addition, since the polarizing plate does not stick to the liquid crystal panel at a portion other than the portion in contact with the bonding roll, it has been found that problems are unlikely to occur when the polarizing plate is bonded to the liquid crystal cell.

  In addition, in this specification, the magnitude | size of the curl of each vertex means what was measured as follows. First, the polarizing plate is placed on a horizontal table so that the surface protective film is disposed on the lower side, and the curl amount at four corners (for example, the length of the double arrow 30 in FIG. 3) is measured. At this time, when a separate film is provided on the pressure-sensitive adhesive layer in the polarizing plate, the curl amount is measured in a state where the separate film is peeled off. Next, the polarizing plate is placed on a horizontal table so that the pressure-sensitive adhesive layer is disposed on the lower side, and the curl amounts at the four corners are measured.

  The curl at the four corners is calculated by adding the numerical values, with the sign of the curl amount when the surface protective film is down being minus and the sign of the curl amount when the surface of the adhesive layer is down is plus. When the added curl size is a positive value, the vertex curl size is positive, and when it is negative, the vertex curl size is negative.

  Moreover, it is preferable that an optical film consists of a cellulose resin. Since the cellulose film has a large dimensional change in the stretching direction in an environment of 23 ° C./55% RH set in a clean room, the difference in curl size on one side of the cut out polarizing plate can be controlled to 3 mm or more. This is because it becomes easy. It is also useful to form a surface treatment layer on the surface of the optical film opposite to the polarizing film bonding surface.

  Furthermore, it is preferable that the polarizing plate of this invention has a transparent protective film between a polarizing film and an adhesive layer.

  According to the present invention, there is also provided a liquid crystal panel in which the above-mentioned composite polarizing plate is laminated on at least one of the liquid crystal cells via an adhesive layer.

  Hereinafter, the member which comprises the polarizing plate and liquid crystal panel of this invention is demonstrated in detail.

[Polarized film]
The polarizing film is usually a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol-based resin film with a dichroic dye, a polyvinyl on which the dichroic dye is adsorbed The alcohol-based resin film is manufactured through a step of crosslinking with a boric acid aqueous solution and a step of washing with water after the crosslinking treatment with the boric acid aqueous solution.

  The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The film thickness of a polyvinyl alcohol-type resin raw film is about 10-100 micrometers, for example, Preferably it is about 10-50 micrometers.

  Uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, the uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can also be performed in a plurality of stages shown here. For uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. Uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this 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. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this 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 of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably 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 assistant. The temperature of the aqueous dichroic organic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

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

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

  After washing with water, a drying process is performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying 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 reduced to a practical level. The moisture content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

  As described above, a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced. The thickness of the obtained polarizing film can be set to about 3 to 40 μm, for example.

  The thickness of the polarizing film is preferably 12 μm or less from the viewpoint that the contraction force of the polarizing film can be kept low and the present invention has a more remarkable effect. The thickness of the polarizing film is usually 3 μm or more in that good optical properties can be imparted.

[Optical film]
The optical film is particularly preferably composed of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. The optical film preferably contains a cellulose resin, a polyolefin resin, or an acrylic resin because the retardation value can be easily controlled and is easily available. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin. Especially, since it is easy to control the curl of a polarizing plate to prescribe | regulate to this invention, it is preferable to contain a cellulose resin.

  The cellulose resin may be an organic acid ester or mixed organic acid ester of cellulose in which part or all of the hydrogen atoms in the hydroxyl group of cellulose are substituted with an acetyl group, a propionyl group, and / or a butyryl group. Examples include cellulose acetate, propionate, butyrate, and mixed esters thereof. Of these, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate and the like are preferable.

  The cellulose resin may contain an appropriate additive as long as the transparency is not impaired. Additives such as antioxidants, ultraviolet absorbers, antistatic agents, lubricants, nucleating agents, antifogging agents, antiblocking agents, phase difference reducing agents, stabilizers, processing aids, plasticizers, impact aids , Matting agents, antibacterial agents, fungicides and the like. Antioxidants include, for example, phenolic antioxidants, phosphorus antioxidants, sulfur antioxidants, hindered amine light stabilizers, and the like, and, for example, phenolic antioxidant mechanisms and phosphorus in one molecule. It is also possible to use a composite type antioxidant having a unit having a system antioxidant mechanism. Examples of the ultraviolet absorber include a 2-hydroxybenzophenone-based ultraviolet absorber, a hydroxyphenylbenzotriazole-based ultraviolet absorber, and a benzoate-based ultraviolet blocker. The antistatic agent may be polymer type, oligomer type or monomer type. Examples of the lubricant include higher fatty acid amides such as erucic acid amide and oleic acid amide, higher fatty acids such as stearic acid, and salts thereof. Examples of the nucleating agent include sorbitol nucleating agents, organophosphate nucleating agents, and polymer nucleating agents such as polyvinylcycloalkane. As the anti-blocking agent, fine particles having a spherical shape or a shape close thereto can be used regardless of inorganic type or organic type. A plurality of these additives may be used in combination.

  In order to form a film from a cellulose-based resin, a method corresponding to the resin may be appropriately selected. For example, a solvent cast method in which a resin dissolved in a solvent is cast on a metal band or drum, and the solvent is removed by drying to obtain a film. The resin is heated above its melting temperature, kneaded and extruded from a die. A melt extrusion method for obtaining a film by cooling can be used. In the melt extrusion method, a single layer film can be extruded or a multilayer film can be coextruded.

  In this invention, it laminates | stacks so that the angle which the absorption axis of a polarizing film and the slow axis of an optical film make may be 45 +/- 20 degree or 135 +/- 20 degree. The optical film is preferably subjected to stretching treatment, and may be a stretched film. The stretching method may be uniaxial stretching or biaxial stretching. When the optical film is produced by uniaxial stretching, the stretching method may be longitudinal stretching or transverse stretching. When the optical film is produced by biaxial stretching, the biaxial stretching method may be sequential biaxial stretching or simultaneous biaxial stretching. The angle between the absorption axis of the polarizing film and the slow axis of the optical film is preferably 45 ± 10 ° or 135 ± 10 ° in that the curling of the polarizing plate is easy to control as defined in the present invention. More preferably, it is 45 ± 5 ° or 135 ± 5 °.

  In general, a long polarizing film has an absorption axis in the long side direction, so that an optical film can be bonded to a long optical film and a long polarizing film by roll-to-roll. It is preferable that it is manufactured by being obliquely stretched by biaxial stretching. As the stretching method, a film produced by simultaneous biaxial stretching is preferred because it is easy to control the curling of the polarizing plate as defined in the present invention. The method of simultaneous biaxial stretching is not particularly limited, but both ends of the unstretched film are gripped by chucks, the feed rates of the chucks at both ends are differentiated, and further spread in a direction (TD) perpendicular to the machine flow direction. Can be manufactured. Simultaneous biaxial stretching includes stretching in one direction and contracting the other tension by relaxing.

  Although the thickness of the optical film is not particularly limited, it is preferably 5 μm or more, more preferably 10 μm or more from the viewpoint of handleability of the optical film 20, and preferably 90 μm or less, more preferably 60 μm from the viewpoint of thinning. It is as follows. Thus, even if it is a case where a thin and firm optical film is used, according to this invention, it is easy to bond a polarizing plate to a liquid crystal cell.

The optical properties of the optical film are not particularly limited, but for example, those satisfying the following formulas (1) to (4) are preferably employed.
(1) 100 nm ≦ R _e (590) ≦ 180 nm,
(2) 0.5 <R _th (590) / R _e (590) ≦ 0.8,
(3) 0.85 ≦ 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 in-plane retardation values at measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively, and R _th ( 590) represents a thickness direction retardation value at a measurement wavelength of 590 nm. These in-plane retardation value and thickness direction retardation value are values measured in an environment of a temperature of 23 ° C. and a relative humidity of 55%.

Plane retardation value R _e, and the thickness direction retardation value R _th, refraction of the refractive index in the in-plane slow axis direction n _x, plane fast axis direction (perpendicular to the plane slow axis direction) When the rate is _ny , the refractive index in the thickness direction is _nz , and the thickness of the optical film is d, the following formula:
_{R e = (n x -n y} ) × d
_{R th = [{(n x} + n y) / 2} -n z] × d
Defined by

  According to the optical laminate in which the optical films showing the retardation characteristics and wavelength dispersion characteristics of the above formulas (1) to (4) are laminated on the viewing side of the polarizer, when applied to an image display device (more specifically, (When applied as a polarizing plate arranged on the viewing side of the image display element), effectively suppresses changes in color when the screen is viewed from various directions (azimuth and polar angles) through polarized sunglasses. And the visibility of the image display device can be improved. On the other hand, when any one or more of the above formulas (1) to (4) are not satisfied, the color change is not sufficiently suppressed.

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

  In addition, a coating layer (surface treatment layer) can be provided on the outer surface of the optical film in order to impart desired surface optical properties or other characteristics. 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 for forming the coating layer is not particularly limited, and a known method can be used.

[Transparent protective film]
The transparent protective film is particularly preferably composed of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. The transparent protective film preferably contains a cellulose resin, a polyolefin resin, or an acrylic resin because the retardation value can be easily controlled and is easily available. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin. In the present specification, the transparent protective film refers to a film having a single transmittance of 80% or more in the visible light region.

  As the cellulose resin, the same resin as that used in the optical film can be used.

  The cyclic polyolefin-based resin is obtained by polymerizing cyclic olefin monomers such as norbornene and other cyclopentadiene derivatives in the presence of a catalyst. When such a cyclic polyolefin-based resin is used, a protective film having a predetermined retardation value described later can be easily obtained.

  As the cyclic polyolefin-based resin, for example, ring-opening metathesis polymerization is performed from cyclopentadiene and olefins or (meth) acrylic acid or esters thereof using norbornene obtained by Diels-Alder reaction or a derivative thereof as a monomer. Resin obtained by hydrogenation; ring-opening metathesis polymerization using dicyclopentadiene and olefins or (meth) acrylic acid or esters thereof by tetracyclododecene or a derivative thereof obtained by Diels-Alder reaction, Resin obtained by subsequent hydrogenation; ring-opening metathesis copolymerization of at least two monomers selected from norbornene, tetracyclododecene, derivatives thereof, and other cyclic olefin monomers, Resins obtained by hydrogenation; resins obtained by addition copolymerization of aromatic compounds having chain olefins and / or vinyl groups with cyclic olefins such as norbornene, tetracyclododecene, or derivatives thereof Can be mentioned.

  As the cyclic polyolefin-based resin, a commercially available product can be easily obtained. Examples of commercially available products are “TOPAS” produced by TOPAS ADVANCED POLYMERS GmbH and sold by Polyplastics Co., Ltd. in Japan, and “ARTON” (registered by JSR Corporation). Trademark) ”,“ ZEONOR (registered trademark) ”and“ ZEONEX (registered trademark) ”sold by Nippon Zeon Co., Ltd., and“ APEL (registered trademark) ”sold by Mitsui Chemicals, Inc.

  Typical examples of the chain polyolefin resin are a polyethylene resin and a polypropylene resin. Among them, a homopolymer of propylene, or a copolymer obtained by copolymerizing propylene as a main component and a comonomer copolymerizable therewith, for example, ethylene in a proportion of 1 to 20% by weight, preferably 3 to 10% by weight. Preferably used.

  The polypropylene resin may contain an alicyclic saturated hydrocarbon resin. By containing the alicyclic saturated hydrocarbon resin, the retardation value can be easily controlled. The content of the alicyclic saturated hydrocarbon resin is advantageously 0.1 to 30% by weight with respect to the polypropylene resin, and more preferably 3 to 20% by weight. When the content of the alicyclic saturated hydrocarbon resin is less than 0.1% by weight, the effect of controlling the retardation value cannot be sufficiently obtained, while when the content exceeds 30% by weight, the protective film Therefore, there is a concern that the alicyclic saturated hydrocarbon resin may bleed out over time.

  The acrylic resin is typically a polymer containing 50% by weight or more of methyl methacrylate units. The content of methyl methacrylate units is preferably 70% by weight or more, and may be 100% by weight.

  As a method for forming a film from the resin as described above, a method corresponding to each resin may be appropriately selected. For example, the solvent casting method, the melt extrusion method described above, or the like can be employed. Among these, for polyolefin resins and acrylic resins, the melt extrusion method is preferably employed from the viewpoint of productivity. On the other hand, a cellulose resin is generally formed into a film by a solvent casting method.

  When the liquid crystal cell is in an in-plane switching (IPS) mode, the transparent protective film has a retardation value Rth in the thickness direction of − in order not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. It is preferable that it exists in the range of 10-10 nm.

  As a method for controlling the retardation value Rth in the thickness direction of the transparent protective film within the range of −10 to 10 nm, there is a method for minimizing the distortion remaining in the plane and in the thickness direction as much as possible. . For example, in the solvent casting method, a method of relaxing residual shrinkage strain in the plane and in the thickness direction generated when the cast resin solution is dried by heat treatment can be employed. On the other hand, in the melt extrusion method, the distance from the die to the cooling drum is reduced as much as possible in order to prevent the resin film from being drawn from the die and cooled, and the extrusion amount and the rotation speed of the cooling drum are reduced. A method of controlling the film so that the film is not stretched can be employed. Moreover, the method of relieving the distortion which remains in the obtained film by heat processing similarly to the solvent casting method is also employable.

[Adhesive layer]
The bonding between the polarizing film and the optical film and the bonding between the polarizing film and the transparent protective film can be bonded with an adhesive. In this specification, the optical film and the transparent protective film may be collectively referred to simply as a protective film.
The adhesive layer for laminating the polarizing film and the protective film can have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. If the thickness of the adhesive layer is within this range, the protective film and the polarizing film to be laminated do not float or peel off, and an adhesive force having no practical problem can be obtained.

  In adhering the polarizing film and the protective film, it is also useful to perform a saponification treatment, a corona treatment, a plasma treatment or the like on the polarizing film or the protective film in advance.

  In forming the adhesive layer, an appropriate adhesive can be used as appropriate according to the type and purpose of the adherend, and an anchor coating agent can be used as necessary. Examples of the adhesive include a solvent-type adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet-adhesive, a polycondensation-type adhesive, a solventless-type adhesive, a film-type adhesive, and a hot-melt-type adhesive. Can be mentioned.

  One preferred adhesive is an aqueous adhesive, that is, an adhesive component in which the adhesive component is dissolved or dispersed in water. Examples of adhesive components that can be dissolved in water include polyvinyl alcohol resins. An example of an adhesive component that can be dispersed in water is a urethane resin having a hydrophilic group. The water-based adhesive can be prepared by mixing such an adhesive component with water together with an additional additive added as necessary. Examples of commercially available polyvinyl alcohol resins that can be used as water-based adhesives include “KL-318”, which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

  The water-based adhesive can contain a crosslinking agent as necessary. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts. When a polyvinyl alcohol resin is used as an adhesive component, an aldehyde compound such as glyoxal, a methylol compound such as methylol melamine, a water-soluble epoxy resin, or the like is preferably used as a crosslinking agent. Here, the water-soluble epoxy resin is, for example, a polyamide obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. It can be an epoxy resin. An example of a commercially available water-soluble epoxy resin is “SUMIREZ RESIN (registered trademark) 650 (30)” sold by Taoka Kogyo Co., Ltd.

  A polarizing plate can be obtained by applying a water-based adhesive to the polarizing film and / or the adhesive surface of the protective film to be bonded to the polarizing film and bonding them together, followed by drying treatment. Prior to adhesion, it is also effective to subject the protective film to easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment to enhance wettability. A drying temperature can be about 50-100 degreeC, for example. After the drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days is preferable for further enhancing the adhesive force.

  Another preferred adhesive is a curable adhesive composition containing an epoxy compound that is cured by irradiation with active energy rays or heating. Here, the curable epoxy compound has at least two epoxy groups in the molecule. In this case, the adhesive between the polarizing film and the protective film is performed by irradiating the applied layer of the adhesive composition with an active energy ray or applying heat to the adhesive composition, and a curable epoxy compound contained in the adhesive. It can carry out by the method of hardening. Curing of the epoxy compound is generally performed by cationic polymerization of the epoxy compound. Further, from the viewpoint of productivity, this curing is preferably performed by irradiation with active energy rays.

  From the viewpoint of weather resistance, refractive index, cationic polymerizability, etc., the epoxy compound contained in the curable adhesive composition is preferably one that does not contain an aromatic ring in the molecule. Examples of epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. The epoxy compound suitably used in such a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline is also described here.

  The hydrogenated epoxy compound is a glycidyl compound obtained by subjecting an aromatic polyhydroxy compound, which is a raw material of an aromatic epoxy compound, to a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction in the presence of a catalyst and under pressure. It can be etherified. Examples of the aromatic polyhydroxy compound that is a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F, and bisphenol S; And novolak type resins; polyhydroxy compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. A glycidyl ether can be obtained by performing a nuclear hydrogenation reaction on such an aromatic polyhydroxy compound and reacting the resulting hydrogenated polyhydroxy compound with epichlorohydrin. Suitable hydrogenated epoxy compounds include hydrogenated glycidyl ether of bisphenol A.

  An 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 a bridged oxygen atom —O— in the structure represented by the following formula, and m is an integer of 2 to 5.

A compound in which one or more hydrogen atoms in (CH ₂ ) _m in this formula are removed and bonded to another chemical structure can be an alicyclic epoxy compound. Further, one or more hydrogen atoms in (CH ₂ ) _m forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m = 3 in the above formula) or an oxabicycloheptane ring (m = 4 in the above formula) has excellent adhesion. It is preferably used from the indication. Specific examples of the alicyclic epoxy compound are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas 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-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] henicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide,
K: Limonene dioxide
L: bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxide and the like.

  The aliphatic epoxy compound can be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; diglycidyl ether of 1,4-butanediol; diglycidyl ether of 1,6-hexanediol; triglycidyl ether of glycerin; triglycidyl ether of trimethylolpropane; ethylene Polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol such as glycol, propylene glycol, and glycerin Can be mentioned.

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

  The epoxy compound used in the curable adhesive composition usually has an epoxy equivalent in the range of 30 to 3,000 g / equivalent, and this epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent. 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 curing is lowered or the adhesive strength is lowered. On the other hand, in a compound having an epoxy equivalent exceeding 3,000 g / equivalent, compatibility with other components contained in the adhesive composition may be reduced.

  From the viewpoint of reactivity, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For that purpose, it is preferable to mix | blend a cationic polymerization initiator with the curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction. From the viewpoint of workability, it is preferable that the cationic polymerization initiator is provided with latency. Hereinafter, a cationic polymerization initiator that generates a cationic species or Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”, and generates a cationic species or a Lewis acid by heat. The cationic polymerization initiator that initiates the polymerization reaction of the epoxy group is referred to as “thermal cationic polymerization initiator”.

  The method of curing the adhesive composition by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at normal temperature and humidity, reducing the need to consider the distortion due to heat resistance or expansion of the polarizing film. And it is advantageous in that the protective film and the polarizing film can be satisfactorily bonded. In addition, since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.

  Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably, it is 15 weight part or less. If the amount of the cationic photopolymerization initiator is less than 0.5 parts by weight based on 100 parts by weight of the epoxy compound, curing will be insufficient and the mechanical strength and adhesive strength of the cured product will tend to be reduced. On the other hand, when the blending amount of the cationic photopolymerization initiator exceeds 20 parts by weight with respect to 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, resulting in an increase in the hygroscopic property of the cured product and durability performance. May be reduced.

  When using a photocationic polymerization initiator, the curable adhesive composition may further contain a photosensitizer as necessary. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. When mix | blending a photosensitizer, it is preferable to make the quantity into the range of 0.1-20 weight part with respect to 100 weight part of curable adhesive compositions. Further, a sensitizing aid such as a naphthoquinone derivative may be used for improving the curing rate.

  On the other hand, examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide.

  The curable adhesive composition containing the epoxy compound is preferably cured by photocationic polymerization as described above, but can be cured by thermal cationic polymerization in the presence of the above-mentioned thermal cationic polymerization initiator. Cationic polymerization and thermal cationic polymerization can be used in combination. When photocationic polymerization and thermal cationic polymerization are used in combination, the curable adhesive composition preferably contains both a photocationic polymerization initiator and a thermal cationic polymerization initiator.

  The curable adhesive composition may further contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound. An oxetane compound is a compound having a 4-membered ring ether in the molecule. When mix | blending an oxetane compound, the quantity is 5-95 weight% normally in 100 weight% of curable adhesive compositions, Preferably it is 5-50 weight%. The polyol compound may be alkylene glycol including ethylene glycol, hexamethylene glycol, polyethylene glycol or the like, or an oligomer thereof, polyester polyol, polycaprolactone polyol, polycarbonate polyol and the like. When the polyol compound is blended, the amount thereof is usually 50% by weight or less, preferably 30% by weight or less in 100% by weight of the curable adhesive composition.

  In addition, the curable adhesive composition may have other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, as long as the adhesiveness is not impaired. Agents, flow modifiers, plasticizers, antifoaming agents, and the like. Examples of the ion trapping agent include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Examples of the antioxidant include And hindered phenolic antioxidants.

  After applying the curable adhesive composition containing the epoxy compound to the adhesive surface of the polarizing film or the protective film, or to the adhesive surface of both of them, it is pasted on the adhesive-coated surface, and active energy rays. The polarizing film and the protective film can be bonded by curing the uncured adhesive layer by irradiating or heating. As an adhesive coating method, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.

  This curable adhesive composition can basically be used as a solvent-free adhesive that does not substantially contain a solvent, but each coating system has an optimum viscosity range, so that the viscosity is adjusted. For this purpose, a solvent may be contained. The solvent is preferably an organic solvent that dissolves each component including an epoxy compound well without degrading the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, etc. Esters can be used.

  When the adhesive composition is cured by irradiation with active energy rays, the above-mentioned various types of active energy rays can be used, but since the handling is easy and the amount of irradiation light is easy to control, ultraviolet rays are not emitted. Preferably used. Active energy rays such as ultraviolet irradiation intensity and irradiation dose do not affect various optical performance including polarization degree of polarizing film, and various optical performance including transparency and retardation characteristics of protective film. Therefore, it is determined as appropriate so as to maintain an appropriate productivity.

  When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator compounded in the curable adhesive composition generates cationic species and Lewis acid, and the specific heating temperature is, for example, about 50 to 200 ° C. .

[Adhesive layer]
The pressure-sensitive adhesive layer for laminating the polarizing plate and the liquid crystal cell is excellent in optical transparency and has excellent adhesive properties including appropriate wettability, cohesiveness, adhesiveness, etc. Furthermore, what is excellent in durability etc. is preferable. Specifically, as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferable.

  The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of an acrylic acid alkyl ester such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate. This acrylic resin is usually copolymerized with a polar monomer. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group. Here, the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group. The group can be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. Specific examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl ( Examples include meth) acrylate and glycidyl (meth) acrylate.

  The acrylic pressure-sensitive adhesive usually contains a crosslinking agent together with the acrylic resin. A typical example of the crosslinking agent is an isocyanate compound having at least two isocyanato groups (—NCO) in the molecule.

  Various additives may be further blended in the adhesive. Suitable additives include silane coupling agents and antistatic agents. A silane coupling agent is effective in increasing the adhesive strength with glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

  The pressure-sensitive adhesive layer is prepared by preparing a pressure-sensitive adhesive composition in which the above-mentioned pressure-sensitive adhesive components are dissolved in an organic solvent, and applying the composition directly onto the transparent protective film, followed by drying and removing the solvent, or separating. Apply the above-mentioned pressure-sensitive adhesive composition to the release-treated surface of a base film made of a resin film that has been subjected to a mold treatment, dry the solvent to remove it to form a pressure-sensitive adhesive layer, and paste this onto the transparent protective film It can be formed by a method of transferring the pressure-sensitive adhesive layer. When a pressure-sensitive adhesive layer is formed on the transparent protective film by the former direct coating method, a resin film (also called a separator or a separate film) that has been subjected to a release treatment is bonded to the surface, and the pressure-sensitive adhesive is used until use. It is customary to protect the surface of the layer temporarily. The latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition that is an organic solvent solution. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also advantageous in that it can be used as a separator after being attached to a polarizing plate.

  Before laminating the pressure-sensitive adhesive on the transparent protective film, it is also useful to perform corona treatment or plasma treatment on the transparent protective film surface or the pressure-sensitive adhesive surface in advance.

[Surface protection film]
The surface protective film is composed of a resin film and a pressure-sensitive adhesive layer laminated thereon. The surface protective film is a protective film used for protecting the surface of the polarizing plate, and usually the surface protective film has, for example, after the polarizing plate with the surface protective film is bonded to an image display element or other optical member. The entire adhesive layer is peeled off.

  The resin constituting the resin film is, for example, a thermoplastic resin such as a polyethylene resin such as polyethylene, a polypropylene resin such as polypropylene, a polyester resin such as polyethylene terephthalate or polyethylene naphthalate, or a polycarbonate resin. Can do. Polyester resins such as polyethylene terephthalate are preferable. The resin film may have a single-layer structure or a multi-layer structure, but is preferably a single-layer structure from the viewpoints of manufacturability and manufacturing cost. About the adhesive layer which a surface protective film has, the description about the adhesive layer mentioned above is quoted.

[Production method of polarizing plate]
Although the manufacturing method of the polarizing plate of this invention is not specifically limited, For example, an optical film, a polarizing film, and a transparent protective film are bonded with an adhesive agent, and a polarizing plate is produced. Thereafter, the surface protective film is bonded to the optical film side of the polarizing plate. An adhesive is applied to the thus-prepared polarizing plate with a surface protective film to form an adhesive layer. At this time, it is preferable that a separator film is bonded to the pressure-sensitive adhesive surface.

  The polarizing plate thus produced is usually cut into a predetermined size by a cutting machine and bonded to a liquid crystal cell. Usually, the polarizing plate is processed and used in a clean room in order to reduce defects due to foreign matters.

  In order to make the difference in curl size between both ends of at least two sides sharing at least one of the four sides of a sheet cut out of a polarizing plate into 3 mm or more, for example, polarized light having a layer configuration as described above Curling can be controlled by adjusting the period during which the plates are stored in a clean room.

  The clean room is set to an environment of approximately 23 ° C./55% RH. In the clean room environment, when the optical film is a film having a high moisture permeability such as a cellulose resin film, the optical film has a slow axis. Directional dimension changes occur.

  Since the polarizing plate is stored in a clean room environment until the work is completed, the polarizing plate is shipped and used in a state in which the dimensional change of the optical film occurs. At this time, the curl shape of the polarizing plate is twisted as shown in FIG. 2, and the difference in curl size can be 3 mm or more.

  In terms of easy control of curling of the polarizing plate, the period for storing the polarizing plate in a clean room environment is preferably 30 minutes to 30 days, and more preferably 30 minutes to 7 days. The storage period refers to the period from when the polarizing plate is manufactured until it leaves the clean room. The clean room environment preferably has a temperature of 18 to 27 ° C. and a humidity of 30 to 70% RH.

  The polarizing plate of the present invention is preferably rectangular, the length of the short side is preferably 30 to 300 mm, and the length of the long side is preferably 50 to 500 mm. Cutting out the polarizing plate to such a size is preferable because curling of the polarizing plate is easily controlled.

  When the polarizing plate is rectangular, it is preferable that the absorption axis of the polarizing film is substantially parallel to any one of the four sides of the polarizing plate. By adopting such a configuration, the slow axis direction of the optical film can be easily directed to the apex direction, and the curl size at the apex can be easily made positive, so that the curl can be easily controlled. In the present invention, “substantially parallel” does not necessarily have to be strictly parallel, but preferably 0 ± 10 °, more preferably 0 ± 5 °.

  The difference in curl between both ends of the two sides sharing the apex of at least one pair of the four sides of the polarizing plate sheet obtained as described above is preferably 4 mm or more. More preferably, it is 20 mm or less, and more preferably 10 mm or less. By controlling the size of the curl within the above range, it is possible to effectively suppress the entrapment of bubbles when the polarizing plate is bonded to the liquid crystal cell. Referring to FIG. 2, for example, for side 1 and side 4 sharing the vertex 11 at the upper left of the page, the absolute value of the difference between the curl size at the vertex 12 and the curl size at the vertex 11 is 3 mm or more. In the side 4, the absolute value of the difference between the curl size at the vertex 12 and the curl size at the vertex 11 is 3 mm or more.

  Further, at the four apexes of the polarizing plate sheet, the difference in curl size between one apex is preferably 2 mm or less, and more preferably 1 mm or less. Furthermore, the difference in the curl size between the other apex is preferably 2 mm or less, and more preferably 1 mm or less. By controlling the size of the curl within the above range, it is possible to more effectively suppress the entrapment of bubbles when the polarizing plate is bonded to the liquid crystal cell. The term “vertical vertex” refers to a pair of two vertices that do not share an edge. Referring to FIG. 2, for example, the vertex 12 at the upper right of the paper and the vertex 12 at the lower left of the paper are a set of vertices that do not share a side. The absolute value of the difference from the curl size is preferably 2 mm or less.

[Liquid Crystal Cell]
The liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the substrates. In general, the cell substrate is often made of glass, but may be a plastic substrate. In addition, the liquid crystal cell itself used in the liquid crystal panel of the present invention can be composed of various types employed in this field.

[LCD panel]
A liquid crystal panel can be produced by bonding a polarizing plate to a liquid crystal cell via an adhesive layer. Usually, although a polarizing plate is bonded on both surfaces of a liquid crystal cell, the composite polarizing plate of this invention is used suitably for the visual recognition side of a liquid crystal display device, a back surface side, or its both surfaces.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, the parts and% representing the content or amount used are based on weight unless otherwise specified. In addition, each physical property in the following examples was measured by the following method.

(1) Measurement of thickness:
Measurement was performed using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation and thickness direction retardation:
In-plane retardation and thickness direction retardation at a predetermined wavelength at a temperature of 23 ° C. using a phase difference meter “KOBRA (registered trademark) -WPR” based on the parallel Nicol rotation method manufactured by Oji Scientific Instruments Co., Ltd. Was measured.
(3) Measurement of Curling Amount of Polarizing Plate With the separate film of the polarizing plate peeled off, the amount of curling at the four corners of the polarizing plate is measured with the surface protective film as the bottom surface. Next, the amount of curl at the four corners of the polarizing plate is measured with the adhesive surface as the bottom surface. The curl at the four corners is calculated by adding the numerical values with the sign of the curl amount when the surface protection film is down as the minus and the sign of the curl amount when the adhesive surface is down as the plus. For the measurement, a JIS class 1 metal scale was used.

[Production Example 1] Production of Polarizing Film A 30 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched by about 4 times by dry stretching, and the tension state is maintained. The sample was immersed in pure water at 40 ° C. for 40 seconds, and then immersed in an aqueous solution having an iodine / potassium iodide / water weight ratio of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds to perform a dyeing treatment. It was. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorption polarizer having a thickness of 12 μm was obtained.

[Production Example 2] Preparation of water-based adhesive 3 parts by weight of carboxyl group-modified 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 was dissolved in the aqueous solution. 1.5 parts by weight of a resin-based polyamide epoxy additive [trade name “Smileise Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30 wt%] was added. A water-based adhesive was prepared.

[Adhesive layer]
Adhesive layer: 25 μm thick sheet adhesive (“P-3132” manufactured by Lintec Corporation)
Prepared.

[Transparent protective films A, B, C]
The following two types of protective films were prepared.
Protective film A: Triacetyl cellulose film manufactured by Konica Minolta, Inc .; KC2CT (thickness 20 μm, in-plane retardation value at wavelength 590 nm = 1.2 nm, thickness direction retardation at wavelength 590 nm = 1.3 nm)
Protective film B: Cyclic polyolefin resin film manufactured by Nippon Zeon Co., Ltd .; ZF14-023 (thickness 23 μm, in-plane retardation value at wavelength 590 nm = 0.5 nm, thickness direction retardation at wavelength 590 nm = 4.3 nm)
Protective film C: Triacetyl cellulose film with hard coat manufactured by Konica Minolta Co., Ltd .; 25KCHCN-TC (in-plane retardation value at a thickness of 32 μm, wavelength of 590 nm = 1.1 nm, thickness direction retardation at a wavelength of 590 nm = 14. 2nm)

[Optical film]
Optical film: Triacetyl cellulose film produced by oblique stretching manufactured by Konica Minolta, Inc .; KC4UGR-HC (thickness 44 μm, in-plane retardation value at wavelength 590 nm = 106 nm, thickness direction retardation at wavelength 590 nm = 75 nm, Rth (590) / Re (590) = 0.71, Re (450) / Re (550) = 0.96, Re (630) / Re (550) = 1.02) were prepared.

[Surface protection film]
As a surface protective film, AY-638 manufactured by Fujimori Kogyo Co., Ltd. (consisting of an adhesive layer having a thickness of 15 μm on a polyester film having a thickness of 38 μm) was prepared.

[Example 1]
The protective film A and the optical film were saponified. The optical film, the polarizing film, and the protective film A were bonded with an aqueous adhesive to obtain a polarizing plate. The layer structure of the polarizing plate is in the order of optical film / polarizing film / protective film A. The polarizing plate was laminated so that the angle formed by the absorption axis of the polarizing film and the slow axis of the optical film was 45 °. Furthermore, the surface protective film was bonded on the optical film of the obtained polarizing plate, and the polarizing plate with a surface protective film was produced. Subsequently, the protective film A surface in the polarizing plate with a surface protective film was subjected to corona treatment, and an adhesive layer with a separate film was bonded.

  The polarizing plate thus produced was cut into a rectangle of 65 mm in the absorption axis direction of the polarizing film and 115 mm in a direction perpendicular to the absorption axis of the polarizing film. That is, the axial configuration of the obtained polarizing plate was as shown in FIG. In FIG. 4, the double arrow 5 represents the absorption axis direction of the polarizing film, and the double arrow 6 represents the slow axis direction of the optical film. The sheet-shaped polarizing plate thus cut was left in an environment of 23 ° C./55% RH for 1 hour.

The separator film of the polarizing plate was peeled off, and the above curl measurement was performed. Using FIG. 4, the curl size of each vertex is 3.0 mm, and the curl size of the vertex 11 at the upper left corner of the paper is −2.5 mm. Yes, the size of the curl at the top right corner of the paper was −2.5 mm, and the size of the curl at the bottom right corner of the paper was 2.5 mm. That is, the difference in curl size of side 1 is 5.5 mm, the difference in curl size of side 2 is 5.0 mm, and the difference in curl size of side 3 is 5.0 mm. The difference in the size of the curl on side 4 was 5.5 mm.
For example, side 1 and side 4 share vertices that constitute paired vertex 11, and the difference in curl size of side 1 and the difference in curl size of side 4 are both 3 mm or more. In addition, the curl size of the vertex 11 was positive.

  The polarizing plate thus obtained was bonded to Eagle XG glass made by Corning Corporation having a length of 200 mm and a width of 120 mm using a hand roller. At this time, a portion having a short side curl amount of −2.5 mm was first brought into close contact with the glass, and the hand roller was moved and bonded so that the angle formed with the absorption axis of the polarizing plate was approximately 45 °. After bonding, no appearance defects or bright spot defects occurred, and it was in a good state.

[Example 2]
The bonding surface of the protective film B with the polarizing film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The optical film, the polarizing film, and the corona-treated surface of the protective film B were bonded with an aqueous adhesive to obtain a polarizing plate. The layer configuration of the polarizing plate is the order of optical film / polarizing film / protective film B. The polarizing plate was laminated so that the angle formed by the absorption axis of the polarizing film and the slow axis of the optical film was 45 °. Furthermore, the surface protective film was bonded on the optical film of the obtained polarizing plate, and the polarizing plate with a surface protective film was produced. Subsequently, the protective film B surface in the polarizing plate with a surface protective film was subjected to corona treatment, and an adhesive layer with a separate film was bonded.

  The polarizing plate thus produced was cut into a rectangle of 65 mm in the absorption axis direction of the polarizing film and 115 mm in a direction perpendicular to the absorption axis of the polarizing film. The sheet-shaped polarizing plate thus cut was left in an environment of 23 ° C./55% RH for 1 hour.

The separator film of the polarizing plate was peeled off, and the above curl measurement was performed. Using FIG. 4, the curl size of each vertex is 3.5 mm, and the curl size of the vertex 11 at the upper left corner of the paper is −2.0 mm. Yes, the size of the curl at the top right corner of the paper was -2.5 mm, and the size of the curl at the bottom right corner of the paper was 3.0 mm. That is, the difference in curl size of side 1 is 6.0 mm, the difference in curl size of side 2 is 5.5 mm, and the difference in curl size of side 3 is 5.0 mm. The difference in the size of the curl on side 4 was 5.5 mm.
For example, side 1 and side 4 share vertices that constitute paired vertex 11, and the difference in curl size of side 1 and the difference in curl size of side 4 are both 3 mm or more. In addition, the curl size of the vertex 11 was positive.

  The polarizing plate thus obtained was bonded to Eagle XG glass made by Corning Corporation having a length of 200 mm and a width of 120 mm using a hand roller. At this time, a portion having a short side curl amount of −2.5 mm was first brought into close contact with the glass, and the hand roller was moved and bonded so that the angle formed with the absorption axis of the polarizing plate was approximately 45 °. After bonding, no appearance defects or bright spot defects occurred, and it was in a good state.

[Comparative Example 1]
The protective film A and the protective film C were saponified. The triacetyl cellulose surface of the protective film C, the polarizing film, and the triacetyl cellulose surface of the protective film A were adhered with an aqueous adhesive to obtain a polarizing plate. The layer structure of the polarizing plate is in the order of protective film A / polarizing film / protective film C. The protective film C has no slow axis. Furthermore, the surface protective film was bonded on the protective film C of the obtained polarizing plate, and the polarizing plate with a surface protective film was produced. Subsequently, the protective film A surface of the polarizing plate with a surface protective film was subjected to corona treatment, and an adhesive layer with a separate film was bonded.

  The polarizing plate thus produced was cut into a rectangle of 65 mm in the absorption axis direction of the polarizing film and 115 mm in a direction perpendicular to the absorption axis of the polarizing film. The sheet-shaped polarizing plate thus cut was left in an environment of 23 ° C./55% RH for 1 hour.

The separator film of the polarizing plate was peeled off, and the above curl measurement was performed. When the curl size of each vertex is shown using FIG. 4, the curl size of the vertex 11 at the upper left of the paper surface is −1.0 mm, and the curl size of the vertex 12 at the lower left of the paper surface is −1.0 mm. The size of the curl at the top right corner of the paper was -0.5 mm, and the size of the curl at the bottom right corner of the paper was -1.5 mm. That is, the difference in curl size on side 1 is 0.5 mm, the difference in curl size on side 2 is 1.0 mm, and the difference in curl size on side 3 is 0.5 mm. The difference in the size of the curl on side 4 was 0.0 mm.
All four sides had a difference in curl size between both ends of less than 3 mm.

  The polarizing plate thus obtained was bonded to Eagle XG glass made by Corning Corporation having a length of 200 mm and a width of 120 mm using a hand roller. At this time, a portion having a short side curl amount of −1.5 mm was first brought into close contact with the glass, and the hand roller was moved and bonded so that the angle formed with the absorption axis of the polarizing plate was approximately 45 °. However, before the hand roller passed, the short side portion was in close contact with the glass, and air bubbles were bitten along the short side. Upon inspection, it was a bright spot defect.

The results are shown in Table 1. Note that the sides 1 to 4 and the paired vertex 1 and the paired vertex 2 in the table coincide with the reference numerals in FIG. Moreover, the criteria for the bonding test are as follows.
○: When air bubbles are not bitten at the time of pasting, and there are no appearance defects or bright spot defects, etc. ×: When air bubbles are bitten at the time of pasting, there are faulty appearance or bright spot defects, etc.

1 side 1
2 side 2
3 Side 3
4 sides 4
5 Absorption axis direction of polarizer 6 Slow axis direction of optical film 11 Vertex 1
12 Vertex 2
20 Polarizing plate 30 Curling amount

Claims (8)

A rectangular-shaped polarizing plate including a surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer in this order,
The angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is 45 ± 20 ° or 135 ± 20 °,
A polarizing plate in which at least one set of four sides of a sheet has a difference in curl size between both ends of two sides sharing the apex is 3 mm or more, and the apex has a positive curl size.   The polarizing plate according to claim 1, wherein a difference in curl size between one pair of vertices is 2 mm or less at the four vertices of the sheet.   The polarizing plate according to claim 2, wherein the difference in curl size between the other apex is 2 mm or less.   The polarizing plate according to claim 1, wherein the optical film includes a cellulose resin.   The polarizing plate according to claim 1, further comprising a transparent protective film between the polarizing film and the pressure-sensitive adhesive layer.   The liquid crystal panel by which the polarizing plate in any one of Claims 1-5 is arrange | positioned on the at least one surface of the liquid crystal cell. Including a surface protective film, an optical film, a polarizing film having a thickness of 15 μm or less, and an adhesive layer in this order,
A polarizing plate having an angle between the absorption axis of the polarizing film and the slow axis of the optical film of 45 ± 20 ° or 135 ± 20 °,
The manufacturing method of a polarizing plate including the process of storing in the environment whose temperature is 18-27 degree | times and humidity is 30-70% RH.   The method for producing a polarizing plate according to claim 7, wherein a length of the storing step is 30 minutes to 30 days.

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