JP2017156399A - Set of polarizing plates and liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a set of polarizing plates that can suppress a warp of a liquid crystal panel under a high-temperature environment, and a liquid crystal panel obtained by laminating the set of polarizing plates on a liquid crystal cell.SOLUTION: In a set of polarizing plates including a first polarizing plate arranged on a visible side of a liquid crystal cell and a second polarizing plate arranged on a back side of the liquid crystal cell, the second polarizing plate includes a reflection type polarizing film, and when a shrinkage force per 2 mm in width in an absorption axis direction of the first polarizing plate when being held for four hours at 80°C is F1 and a shrinkage force per 2 mm in width in a transmission axis direction is F2, and a shrinkage force per 2 mm in width in an absorption axis direction of the second polarizing plate when being held for four hours at 80°C is F3 and a shrinkage force per 2 mm in width in a transmission axis direction is F4, (F1×F2)/(F3×F4) is 0.5 to 5.0.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a set of polarizing plates in which warpage of a liquid crystal panel is suppressed under a high temperature environment, and a liquid crystal panel using the set.

  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.

  As the liquid crystal panel is made thinner, there is a problem that the liquid crystal panel warps due to contraction of the polarizing plate bonded to the liquid crystal cell in a high temperature environment, and the liquid crystal panel does not fit in the final product casing.

  In order to suppress such warpage of the liquid crystal display panel, the liquid crystal display has been changed by changing the thickness of the polarizing plate disposed on the liquid crystal cell viewing side and the side opposite to the liquid crystal cell viewing side (back side). Techniques for suppressing panel warpage have been developed. For example, in Japanese Patent Application Laid-Open No. 2012-58429 (Patent Document 1), the thickness of a polarizing film (polarizer in the present invention) of a polarizing plate disposed on the viewing side of a liquid crystal cell is disposed on the back side of the liquid crystal cell. A method for suppressing warpage of a liquid crystal display panel by making it thinner than a polarizing film is described.

  JP 2013-37115 A (Patent Document 2) discloses an optical device in which a polarizing film (a polarizer referred to in the present invention) included in an optical laminate on the viewing side is disposed on the side opposite to the viewing side. There has been proposed a technique for suppressing the warpage of the liquid crystal panel by making it 5 μm or more thicker than the polarizing film included in the laminate. However, these methods can be effective for a liquid crystal cell having a large thickness (for example, 0.5 mm or more, further 0.7 mm or more), but warpage is suppressed for a thin liquid crystal cell. Was insufficient

JP 2012-58429 A JP2013-37115A

  The objective of this invention is providing the liquid crystal panel formed by bonding the set of the polarizing plate which can suppress the curvature of a liquid crystal panel in a high temperature environment, and this polarizing plate set to a liquid crystal cell.

[1] In a set of polarizing plates having a first polarizing plate disposed on the viewing side of the liquid crystal cell and a second polarizing plate disposed on the back side of the liquid crystal cell,
The second polarizing plate has a reflective polarizing film,
When the first polarizing plate is held at 80 ° C. for 4 hours, the contraction force per 2 mm width in the absorption axis direction is F1, and the contraction force per 2 mm width in the transmission axis direction is F2.
When the contraction force per 2 mm width in the absorption axis direction when the second polarizing plate is held at 80 ° C. for 4 hours is F3, and the contraction force per 2 mm width in the transmission axis direction is F4, (F1 × F2 ) / (F3 × F4) is a set of polarizing plates of 0.5 to 5.0.
[2] Each of the first polarizing plate and the second polarizing plate has a polarizer made of a polyvinyl alcohol-based resin film, and the thickness of each of the polarizers is 20 μm or less. Set of polarizing plates.
[3] The set of polarizing plates according to [2], wherein the thickness of the polarizer included in the first polarizing plate is 10 μm or more, and the thickness of the polarizer included in the second polarizing plate is 10 μm or less.
[4] The polarized light according to [2] or [3], wherein the second polarizing plate has a protective film laminated on one surface of the polarizer and the reflective polarizer laminated on the other surface. A set of boards.
[5] The set of polarizing plates according to [4], wherein the moisture permeability of the protective film is 500 g / (m ² · 24 hr) or less.
[6] A liquid crystal panel comprising the polarizing plate set according to any one of [1] to [5] and a liquid crystal cell, wherein the thickness of the liquid crystal cell is 0.4 mm or less.

  ADVANTAGE OF THE INVENTION According to this invention, the curvature in the high temperature environment in a liquid crystal panel can be eliminated, and the liquid crystal panel which can be accommodated in the housing | casing of the final product in a high temperature environment can be obtained.

It is a schematic sectional drawing which shows the example of the preferable layer structure in the set of the polarizing plate which concerns on this invention. It is a schematic sectional drawing which shows the example of the preferable layer structure in the set of the polarizing plate which concerns on this invention. It is a perspective view which shows the example of the preferable axial structure in the set of the polarizing plate which concerns on this invention. It is the schematic of an example of the reflective polarizer used for this invention. It is a schematic sectional drawing which shows the example of the liquid crystal panel of this invention.

  Hereinafter, a set of polarizing plates according to the present invention and a liquid crystal panel using the same will be described with reference to the drawings, but the present invention is not limited to these embodiments.

  The set of polarizing plates of the present invention includes a first polarizing plate 10 disposed on the viewing side of the liquid crystal cell and a second polarizing plate 11 disposed on the back side of the liquid crystal cell. With reference to FIG. 1, the layer structure of the 1st polarizing plate 10 and the 2nd polarizing plate 11 concerning this invention is demonstrated. In FIG. 1, the first polarizing plate 10 is obtained by bonding protective films 30 a and 30 b to both surfaces of a polarizer 20. It is also useful to form a surface treatment layer on the surface of the protective film 30a opposite to the bonding surface with the polarizer 20. The second polarizing plate 11 preferably has a protective film on at least one surface of the polarizer 21, and protective films 31a and 31b are laminated on both surfaces of the polarizer as shown in FIG. The reflective polarizer 50 may be laminated through the gap. Further, as shown in FIG. 2, a protective film 31a is laminated on one surface of the polarizer 21, and the reflective film is directly reflected on the polarizer 21 via the adhesive layer 40 without the protective film 31b on the other surface. It is also preferable to stack 50. These polarizing plates are bonded to the liquid crystal cell via the pressure-sensitive adhesive layers 32 and 33, respectively, to form a liquid crystal panel.

  In the set of polarizing plates of the present invention, the shrinkage force per 2 mm width in the absorption axis direction when the first polarizing plate is held at 80 ° C. for 4 hours is F1, and the shrinkage force per 2 mm width in the transmission axis direction is F2. When the second polarizing plate is held at 80 ° C. for 4 hours and the contraction force per 2 mm width in the absorption axis direction is F3, and the contraction force per 2 mm width in the transmission axis direction is F4, (F1 × F2 ) / (F3 × F4) is 0.5 to 5.0. It is not sufficient to simply reduce the shrinkage force of the first polarizing plate and the second polarizing plate. By satisfying such a condition, even if the thickness of the liquid crystal cell is thin, the liquid crystal panel Was found to be able to suppress warping of the liquid crystal panel when allowed to stand in an environment of 85 ° C. for 250 hours.

  The inventor presumes the principle as follows, but does not limit the present invention. Here, the contraction force of the polarizing plate affects the warpage of the liquid crystal panel, and it can be estimated that the contraction force in the absorption axis direction of the polarizer included in the polarizing plate becomes more dominant for the warpage of the liquid crystal panel. F3 / F2 is related to the direction of the transmission axis of the first polarizing plate in the liquid crystal panel (the second transmission axis direction) (second transmission axis direction of the second polarizing plate). This relates to the ease of warping in the absorption axis direction of the polarizing plate. The net warpage of the liquid crystal panel is considered to be determined by the ratio (balance) between F1 / F4 and F3 / F2, and the ratio is (F1 × F2) / (F3 × F4).

  The contraction force F1 in the absorption axis direction of the first polarizing plate is preferably 3 N / 2 mm or less, more preferably 2.5 N / 2 mm or less, from the viewpoint of easily satisfying the above formula. It may be greater than 6N / 2mm. The contraction force F2 in the transmission axis direction of the first polarizing plate is preferably 0.3 N / 2 mm or less, more preferably 0.15 N / 2 mm or less, and usually 0.00 N / 2 mm or more.

  The contraction force F3 in the absorption axis direction of the second polarizing plate is preferably 3 N / 2 mm or less, more preferably 2.5 N / 2 mm or less, and further 2 from the viewpoint that the above formula is easily satisfied. It is preferably 0.0 N / 2 mm or less, and more preferably 1.6 N / 2 mm or less. The contraction force F4 in the transmission axis direction of the second polarizing plate is preferably 0.3 N / 2 mm or less, more preferably 0.15 N / 2 mm or less, and usually 0.00 N / 2 mm or more.

  Since the above formula easily satisfies the range of 0.5 to 5.0, the contraction force F3 in the absorption axis direction of the second polarizing plate is smaller than the contraction force F1 in the absorption axis direction of the first polarizing plate. It is preferable.

  In the set of polarizing plates of the present invention, the ratio of the thickness of the first polarizing plate to the thickness of the second polarizing plate is 0.00 in that the range of (F1 × F2) / (F3 × F4) is easy to adjust. It is preferably 8 to 1.5, more preferably 1.01 to 1.5, and still more preferably 1.01 to 1.4. Specifically, the thickness of the first polarizing plate is preferably 80 μm or less, and more preferably 70 μm or less. The thickness of the polarizing plate of the second polarizing plate is preferably 70 μm or less, and more preferably 60 μm or less. In addition, the thickness of a polarizing plate said here does not include the thickness of the adhesive layer for bonding to a liquid crystal cell.

  Furthermore, the first polarizing plate has an arrangement in which the absorption axis is substantially parallel to the short side direction of the liquid crystal cell, and the second polarizing plate has an arrangement in which the absorption axis is substantially parallel to the long side direction of the liquid crystal cell. It is preferable. “Substantially parallel” is not limited to being strictly parallel. For example, the angle formed by the absorption axis of the polarizing plate and each side of the liquid crystal cell is preferably 5 ° or less, and more preferably 3 ° or less. More preferably, it is 1 ° or less.

  Hereinafter, the set of polarizing plates and the members constituting the liquid crystal panel of the present invention will be described in detail. In addition, the polarizer 20 included in the first polarizing plate 10 and the polarizer 21 included in the second polarizing plate 11 may be collectively referred to simply as a polarizer, and the protective film 30a, the protective film 30b, and the protective film may be protected. The film 31a and the protective film 31b may be collectively referred to simply as a protective film.

[Polarizer]
As the polarizers 20 and 21, any appropriate one can be used as long as the curling force is satisfied. A polarizer 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 a 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 polarizer. 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.

  The longitudinal 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 longitudinal uniaxial stretching is performed after dyeing, the longitudinal uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, longitudinal uniaxial stretching can also be performed in a plurality of stages shown here. For the longitudinal 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. The longitudinal 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 the first polarization in that the contraction force of each polarizer can be easily adjusted so that (F1 × F2) / (F3 × F4) satisfies 0.5 to 5.0. When producing the polarizer of a board, 60-70 degreeC is preferable, and when producing the polarizer of a 2nd polarizing plate, 55-65 degreeC is preferable.

  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 polarizer. 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 process, the moisture content in the polarizer 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 flexibility of the polarizer is lost, and it 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 polarizer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be produced.

Further, the stretching, dyeing, boric acid treatment, water washing step, and drying step of the polyvinyl alcohol resin film in the production process of the polarizer may be performed in accordance with, for example, the method described in JP2012-159778A. . In the method described in this document, it is also useful to use a method of forming a polyvinyl alcohol resin layer to be a polarizer by coating a base film with a polyvinyl alcohol resin.

  In order to adjust the contraction force of each polarizing plate in the set of polarizing plates to the above range, it is preferable that the thicknesses of the polarizers of the first polarizing plate and the second polarizing plate are both 20 μm or less, More preferably, it is less than 15 μm. Furthermore, the thickness of the polarizer included in the first polarizing plate is preferably 10 μm or more, and the thickness of the polarizer included in the second polarizing plate is preferably 10 μm or less. The thickness of the polarizer is usually 3 μm or more in that good optical properties can be imparted. Although the contraction force of the polarizing plate is affected by the contraction of the reflective polarizer, by setting the thickness of the polarizer to 20 μm or less, the thickness of the polarizer included in the first polarizing plate and the second By providing a predetermined thickness difference with respect to the thickness of the polarizer of the polarizing plate, the warp of the liquid crystal panel can be easily reduced.

[Protective film]
As protective film 30a, 30b, 31a, 31b, what is formed from appropriate transparent resin can be used. Specifically, it is preferable to use a polymer made of a polymer excellent in transparency, uniform optical properties, mechanical strength, thermal stability, and the like. Examples of such transparent resin films include cellulose films such as triacetyl cellulose and diacetyl cellulose, polyester films such as polyethylene terephthalate, polyethylene isophthalate, and polybutylene terephthalate, polymethyl (meth) acrylate, and polyethyl (meth) acrylate. An acrylic film such as, for example, a polycarbonate film, a polyethersulfone film, a polysulfone film, a polyimide film, a polyolefin film, and a polynorbornene film can be used, but is not limited thereto.

  The protective films 30a and 30b applied to the first polarizing plate 10 and the protective films 31a and 31b applied to the second polarizing plate 11 may be the same or different from each other. There may be.

The protective films 31a and 31b applied to the second polarizing plate 11 preferably have different moisture permeability, and the magnitude of the difference in moisture permeability is 750 g / (under conditions of a temperature of 40 ° C. and a relative humidity of 90%. m ² · 24 hr) or more is preferable, and 1000 g / (m ² · 24 hr) or more is more preferable. For example, the difference in moisture permeability can be increased by using different materials for the protective films 31a and 31b. It is also preferable to omit the protective film 31b of the second polarizing plate and to have a protective film only on one side of the polarizer. In this case, the moisture permeability of the protective film 31a is 500 g / (m ² · 24 hr). Or less, more preferably 250 g / (m ² · 24 hr) or less.

  Prior to bonding to the polarizer, the protective film may be subjected to easy adhesion treatment such as saponification treatment, corona treatment, primer treatment, anchor coating treatment on the bonding surface. The thickness of the protective film is usually in the range of about 5 to 200 μm, preferably 10 μm or more, preferably 80 μm or less, more preferably 40 μm or less, and particularly preferably 35 μm or less.

  Moreover, in order to provide a desired surface optical characteristic or other characteristics, a coating layer (surface treatment layer) can be provided on the outer surface of the protective film 30a. 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.

  When the liquid crystal cell is in an in-plane switching (IPS) mode, the protective film 30b and the protective film 31b are arranged in the thickness direction so as not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. The phase difference value Rth is preferably in the range of −10 to 10 nm. The in-plane retardation value Re is also preferably in the range of −10 to 10 nm.

The retardation value Rth in the thickness direction is a value obtained by multiplying the value obtained by subtracting the refractive index in the thickness direction from the in-plane average refractive index, and is defined by the following formula (a). The in-plane retardation value Re is a value obtained by multiplying the in-plane refractive index difference by the film thickness, and is defined by the following formula (b).
Rth = [(nx + ny) / 2-nz] × d (a)
Re = (nx−ny) × d (b)

  In the formula, nx is the refractive index in the x-axis direction (in-plane slow axis direction) in the film plane, and ny is the y-axis direction (in-plane fast axis direction in the film plane, and x in the plane). The refractive index in the direction perpendicular to the axis), nz is the refractive index in the z-axis direction (thickness direction) perpendicular to the film surface, and d is the thickness of the film.

  Here, the phase difference value may be a value at an arbitrary wavelength in the range of about 500 to 650 nm near the center of visible light, but in this specification, the phase difference value at a wavelength of 590 nm is used as a standard. The retardation value Rth in the thickness direction and the in-plane retardation value Re can be measured using various commercially available retardation meters.

  Examples of the method for controlling the retardation value Rth in the thickness direction of the protective film within a range of −10 to 10 nm include 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.

[Reflective polarizer 50]
The second polarizing plate 11 of the present invention has a reflective polarizer 50. FIG. 4 is a schematic cross-sectional view of an example of a reflective polarizer used in the present invention. The reflective polarizer 50 is a multilayer laminate in which layers A having birefringence and layers B having substantially no birefringence are alternately laminated. For example, in the illustrated example, the refractive index nx in the x-axis direction of the A layer is larger than the refractive index ny in the y-axis direction, and the refractive index nx in the x-axis direction and the refractive index ny in the y-axis direction of the B layer are substantially equal. Are the same. Accordingly, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and is substantially zero in the y-axis direction. As a result, the x-axis direction becomes the reflection axis, and the y-axis direction becomes the transmission axis. The difference in refractive index between the A layer and the B layer in the x-axis direction is preferably 0.2 to 0.3. The x-axis direction corresponds to the extending direction of the reflective polarizer.

  The A layer is preferably made of a material that exhibits birefringence by stretching. Representative examples of such materials include naphthalene dicarboxylic acid polyesters (for example, polyethylene naphthalate), polycarbonates, and acrylic resins (for example, polymethyl methacrylate). Polyethylene naphthalate is preferred. The B layer is preferably made of a material that does not substantially exhibit birefringence even when stretched. A typical example of such a material is a copolyester of naphthalenedicarboxylic acid and terephthalic acid.

  The reflective polarizer transmits light having a first polarization direction (for example, p-wave) at the interface between the A layer and the B layer, and has a second polarization direction orthogonal to the first polarization direction. Reflects light (eg, s-wave). The reflected light is partially transmitted as light having the first polarization direction and partially reflected as light having the second polarization direction at the interface between the A layer and the B layer. The light utilization efficiency can be increased by repeating such reflection and transmission many times inside the reflective polarizer.

  Preferably, the reflective polarizer 50 includes a reflective layer R as an outermost layer opposite to the polarizer 21. By providing the reflective layer R, it is possible to further use the light that has not been finally used and has returned to the outermost part of the reflective polarizer, so that the light use efficiency can be further increased. The reflective layer R typically exhibits a reflective function due to the multilayer structure of the polyester resin layer.

  The total thickness of the reflective polarizer can be appropriately set according to the purpose, the total number of layers included in the reflective polarizer, and the like. From the viewpoint of suppressing dimensional changes in a high temperature environment, the total thickness of the reflective polarizer is preferably 15 μm to 50 μm, more preferably 30 μm or less.

  As the reflective polarizer, for example, the one described in JP-T-9-507308 can be used.

As the reflective polarizer 50, a commercially available product may be used as it is, or a commercially available product may be used after secondary processing (for example, stretching). As a commercial item, 3M company brand name DBEF and APF are mentioned, for example.

[Bonding of polarizer and protective film]
Bonding with a polarizer and a protective film can be bonded with an adhesive or an adhesive. The adhesive layer that bonds the polarizer 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 adhesive film having no practical problem can be obtained without causing floating or peeling between the protective film to be laminated and the polarizer. The pressure-sensitive adhesive layer that bonds the polarizer and the protective film can have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.

  In bonding the polarizer and the protective film, it is also useful to perform saponification treatment, corona treatment, plasma treatment, or the like in advance on the polarizer or the protection film.

[adhesive]
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 “Smilease Resin (registered trademark) 650 (30)” sold by Taoka Chemical Co., Ltd.

  A polarizing plate can be obtained by applying a water-based adhesive to the polarizer and / or the adhesive surface of the protective film to be bonded to the polarizer 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 that is cured by irradiation with active energy rays or heating. Examples of the curable adhesive composition include a curable adhesive composition containing a radical polymerizable compound such as an acrylic compound and a curable adhesive composition containing a cationic polymerizable compound such as an epoxy compound. Can be mentioned. Each of these compositions preferably contains a radical polymerization initiator or a cationic polymerization initiator.

  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 the curable adhesive composition is applied to the adhesive surface of the polarizer or the protective film, or both of the adhesive surfaces, it is bonded on the adhesive-coated surface and irradiated with active energy rays, or By heating, the uncured adhesive layer can be cured to bond the polarizer and the protective film. 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 polarizer. 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 the degree of polarization of the polarizer, and various optical performance including the transparency and retardation characteristics of the protective film. Therefore, it is determined as appropriate so as to maintain an appropriate productivity.

[Adhesive]
The pressure-sensitive adhesive is not particularly limited as long as it has excellent optical transparency and excellent pressure-sensitive adhesive properties including appropriate wettability, cohesiveness, adhesiveness, and the like. 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 pressure-sensitive adhesive component as described above is dissolved in an organic solvent, applying this directly onto a polarizer or a protective film, and removing the solvent by drying. Alternatively, the above pressure-sensitive adhesive composition is applied to the release-treated surface of a base film made of a resin film that has been subjected to a release treatment, and the solvent is removed by drying to form a pressure-sensitive adhesive layer on the transparent protective film. It can be formed by sticking and 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) that has been subjected to a release treatment is bonded to the surface, and the surface of the pressure-sensitive adhesive layer is kept until use. It is customary to protect 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 polarizer or the protective film, it is also useful to perform corona treatment or plasma treatment on the polarizer surface, the protective film surface, and the pressure-sensitive adhesive surface in advance.

[Lamination of other components]
An adhesive layer can be used for laminating the polarizing plate and the liquid crystal cell, and an adhesive or an adhesive can be used for the adhesive layer used for laminating the reflective polarizer 50. It is preferable to use an adhesive. The pressure-sensitive adhesive layer is not particularly limited as long as it has excellent optical transparency and excellent pressure-sensitive adhesive properties including appropriate wettability, cohesiveness, adhesion, and the like. 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.

  As an adhesive layer, the thing equivalent to what is used for pasting of the above-mentioned polarizer and a protective film can be used. Different adhesives may be used, or the same adhesive may be used.

  Before laminating the pressure-sensitive adhesive on the polarizing plate, it is also useful to perform corona treatment or plasma treatment on the polarizer surface, the protective film surface and the pressure-sensitive adhesive surface in advance. Moreover, when laminating | stacking a reflection type polarizer, it is also useful to perform a corona treatment, a plasma processing, etc. to the bonding surface and adhesive surface of the reflection type polarizer 50 previously. The pressure-sensitive adhesive layer used for laminating the reflective polarizer 50 is preferably 25 μm or less. More preferably, it is 15 μm or less. Usually, the thickness of the pressure-sensitive adhesive layer is 3 μm or more.

[Liquid crystal cell, liquid crystal panel]
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 is composed of various types employed in this field (for example, known modes such as IPS mode, VA mode, and TN mode as drive modes). Can do. Recently, since the thickness of the liquid crystal cell has been reduced and its rigidity has been reduced, warpage is very likely to occur when a liquid crystal panel is formed. Therefore, the conventional polarizing plate set capable of reducing the warpage of the liquid crystal panel was effective for a liquid crystal cell having a large thickness (for example, 0.5 mm or more). When applied to a liquid crystal cell, the liquid crystal panel may also be warped. However, according to the set of polarizing plates of the present invention, even if the thickness of the liquid crystal cell is 0.4 mm or less, or even 0.3 mm or less, warpage can be significantly reduced. In the present invention, the thickness of the liquid crystal cell includes the thickness of the liquid crystal layer and a pair of substrates sandwiching the liquid crystal layer.

As shown in FIG. 5, a liquid crystal panel can be produced by bonding a set of polarizing plates of the present invention to a liquid crystal cell via an adhesive layer.
From another viewpoint, in the liquid crystal panel of the present invention, the absolute value of the warp amount when heated at 85 ° C. for 250 hours is 0.5 mm or less, preferably 0.3 mm or less. By bonding the polarizing plate set of the present invention to the liquid crystal cell, the liquid crystal panel of the present invention is a liquid crystal display panel integrated with a front plate that is suppressed from warping in a high temperature environment and fits in the casing of the final product. .

  The shape of the polarizing plate is preferably a rectangular shape having a long side and a short side in that the effect of the present invention can be made more remarkable. When the polarizing plate of the present invention has a rectangular shape having a long side and a short side, the ratio of the length of the long side to the length of the short side is preferably 10: 1 to 1: 1, and 2: 1 to 2: 1. More preferably, it is 1: 1. The size of the polarizing plate is preferably 50 mm or more, and more preferably 150 mm or more, and the length of the short side is preferably 40 mm or more, and 80 mm or more. It is more preferable that Specifically, the size of the polarizing plate of the present invention is, for example, preferably 2.7 type (55 mm × 41 mm) or more, and preferably 11.3 type (174 mm × 231 mm) or less.

  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 shrinkage force For a polarizing plate that does not have an adhesive layer for bonding to a liquid crystal cell, a super cutter (width 2 mm, length 50 mm so that the direction in which the shrinkage force is measured is the long side ( (Made by Hadano Seiki Seisakusho Co., Ltd.). The obtained strip-shaped chip was used as a test piece. The shrinkage force of the test piece was measured using a thermomechanical analyzer (model II TMA / 6100, manufactured by SII Nano Technology Co., Ltd.). This measurement was performed in the constant dimension mode, and the distance between chucks was set to 10 mm. After leaving the test piece in a room at 23 ° C. and 55% for 24 hours or more, the temperature in the sample room is raised from 23 ° C. to 80 ° C. over 1 minute, and after the temperature rise, the temperature in the sample room is maintained at 80 ° C. Was set as follows. After allowing the temperature to rise for another 4 hours, the contraction force in the long side direction of the test piece was measured in an environment at 80 ° C. In this measurement, the static load was 0 mN, and a SUS probe was used as the jig.

(3) Measurement of warpage amount of liquid crystal panel The warpage amount of the manufactured liquid crystal panel in a high temperature environment was measured by the following method. First, the prepared liquid crystal display panel was allowed to stand in an environment of 85 ° C. for 250 hours, and then on a measuring table of a Nikon Corporation two-dimensional measuring instrument “NEXIV VMR-12072” with the first polarizing plate facing upward. Put it on. Next, after focusing on the surface of the measuring table and using that as a reference, focusing on each of the four corners, four sides of the liquid crystal panel and the center of the liquid crystal panel surface, and measuring the distance from the reference focus The warp amount is the longest distance from the measuring table, and the warp of the panel warp on the viewing side of the liquid crystal panel is a positive warp, and the warp of the panel warp on the back side is a negative warp. It was. The results are summarized in Table 1.

(4) Measurement of moisture permeability of protective film The moisture permeability was measured according to the cup method defined in JIS Z 0208 under the conditions of a temperature of 40 ° C and a relative humidity of 90%.

[Example 1]
The viewing side polarizing plate was produced as follows. A 30 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is about 5 times longitudinally uniaxially stretched by dry stretching and further maintained in a 60 ° C. pure water while maintaining tension. After being immersed for 1 minute, it was immersed for 60 seconds in a 28 ° C. aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100. Then, it was immersed for 300 seconds in the 70 degreeC aqueous solution whose weight ratio of potassium iodide / boric acid / water is 8.5 / 8.5 / 100. Subsequently, after washing with pure water at 26 ° C. for 20 seconds, drying treatment was performed at 65 ° C. to obtain a polarizer having a thickness of 12 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

Next, on both sides of this polarizer, 3 parts by weight of carboxyl group-modified polyvinyl alcohol [“KL-318” manufactured by Kuraray Co., Ltd.] is dissolved in 100 parts by weight of water to prepare an aqueous solution of polyvinyl alcohol. Water-soluble polyamide epoxy resin (“SUMIREZ RESIN (registered trademark) 650 (30)” manufactured by Sumitomo Chemical Co., Ltd., solid content concentration: 30% by weight) in a ratio of 1.5 parts by weight per 100 parts by weight of water A mixed aqueous adhesive is applied, and a 25 μm thick triacetylcellulose film (trade name “KC2UA” manufactured by Konica Minolta Opto Co., Ltd.) as a protective film and a 15 μm thick norbornene film [JSR stock] company under the trade name "ARTON (registered trademark)" in-plane retardation value at a wavelength 590 nm _R 0 = 0 nm, the thickness direction Retardation value pasted the _R th = 0 nm]. The polarizing plate was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. On the other side of the polarizer, a 20 μm thick adhesive [trade name “#KT” manufactured by Lintec Corporation] was bonded to obtain a viewing side polarizing plate.

  The back side polarizing plate was produced as follows. A 20 μm-thick polyvinyl alcohol film (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is about 5 times longitudinally uniaxially stretched by dry stretching and further kept in a pure water at 60 ° C. while maintaining tension. After being immersed for 1 minute, it was immersed for 60 seconds in a 28 ° C. aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100. Then, it was immersed for 300 seconds in 65 degreeC aqueous solution whose weight ratio of potassium iodide / boric acid / water is 8.5 / 8.5 / 100. Subsequently, after washing with pure water at 26 ° C. for 20 seconds, drying treatment was performed at 65 ° C. to obtain a 7 μm thick polarizer in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

  The aqueous adhesive is applied to one surface of a polarizer, and a norbornene-based film having a thickness of 13 μm as a protective film [trade name “ZEONOR (registered trademark)” manufactured by Nippon Zeon Co., Ltd., an in-plane retardation value Re = 0.8 nm], dried at 80 ° C. for 5 minutes, and cured at 40 ° C. for 168 hours. On the other side of the polarizer, a 5 μm-thick adhesive (trade name “# L2” manufactured by Lintec Corporation) is bonded, and a 26 μm-thick brightness enhancement film (trade name made by 3M “Advanced Polarized”) is attached thereto. Film, Version 3) was pasted, and then a 20 μm thick adhesive (trade name “#KT” manufactured by Lintec Corporation) was pasted on the norbornene-based film side to obtain a back side polarizing plate.

The thickness of the viewing side polarizing plate was 52 μm, the thickness of the back side polarizing plate was 51 μm, and the thickness ratio was 1.02. Under conditions of a temperature of 40 ° C. and a relative humidity of 90%, the norbornene-based film used for the back-side polarizing plate had a moisture permeability of 30 g / (m ² · 24 hr).

[Example 2]
The viewing side polarizing plate was produced as follows. A polarizer having a thickness of 12 μm was prepared in the same manner as in Example 1, and the water-based adhesive described in Example 1 was applied to both sides thereof. A 25 μm-thick triacetylcellulose film [manufactured by Konica Minolta Opto Co., Ltd. A film in which an acrylic hard coat layer having a thickness of 7 μm is laminated on a product name “KC2UA” and a norbornene-based film having a thickness of 23 μm that has not been stretched (trade name “ZEONOR (registered trademark)” manufactured by Nippon Zeon Co., Ltd.) Was pasted. The polarizing plate was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. Thereafter, an adhesive having a thickness of 20 μm [trade name “#KT” manufactured by Lintec Corporation] was bonded to the norbornene-based film side to obtain a viewing-side polarizing plate.

  The back side polarizing plate used in Example 1 was used for the back side polarizing plate.

  The thickness of the viewing side polarizing plate was 67 μm, the thickness of the back side polarizing plate was 51 μm, and the thickness ratio was 1.31.

[Comparative Example 1]
The viewing side polarizing plate was produced as follows. A polarizer having a thickness of 7 μm was prepared in the same manner as in Example 1 except that the temperature of the aqueous solution composed of potassium iodide / boric acid / water was 70 ° C., and the aqueous adhesive described in Example 1 was applied to both sides thereof. A film in which an acrylic hard coat layer having a thickness of 7 μm is laminated on a 25 μm thick triacetyl cellulose film (trade name “KC2UA” manufactured by Konica Minolta Opto Co., Ltd.) as a protective film, and a 20 μm thick triacetyl film A cellulose film (trade name “KC2CTW” manufactured by Konica Minolta Opto Co., Ltd., in-plane retardation value R ₀ = 1.2 nm at a wavelength of 590 nm, thickness direction retardation value R _th = 1.3 nm) was bonded. It was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. Thereafter, a 20 μm-thick adhesive (trade name “#KT” manufactured by Lintec Corporation) was bonded to the 20 μm-thick triacetylcellulose film side to obtain a viewing-side polarizing plate.

  The back side polarizing plate was produced as follows. A polarizer having a thickness of 12 μm was prepared in the same manner as in Example 1 except that the temperature of the aqueous solution composed of potassium iodide / boric acid / water was 65 ° C., and the aqueous adhesive described in Example 1 was applied to both sides thereof. As a protective film, a 25 μm thick triacetylcellulose film (trade name “KC2UA” manufactured by Konica Minolta Opto Co., Ltd.) and a non-stretched 23 μm thick norbornene film (trade name manufactured by Nippon Zeon Co., Ltd.) “ZEONOR (registered trademark)”] was bonded. It was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. A 5 μm-thick adhesive (trade name “# L2” manufactured by Lintec Corporation) is bonded to the triacetyl cellulose film surface, and a 26 μm-thick brightness enhancement film (trade name manufactured by 3M “Advanced Polarized Film, Version 3) was bonded, and then a 20 μm thick adhesive [trade name “#KT” manufactured by Lintec Corporation] was bonded to the norbornene-based film side to obtain a back side polarizing plate.

The thickness of the viewing side polarizing plate was 59 μm, the thickness of the back side polarizing plate was 91 μm, and the thickness ratio was 0.65. Under conditions of a temperature of 40 ° C. and a relative humidity of 90%, the moisture permeability of the triacetyl cellulose film is 1200 g / (m ² · 24 hr), and the moisture permeability of the norbornene film is 6 g / (m ² · 24 hr). there were.

[Comparative Example 2]
The viewing side polarizing plate used in Example 1 was used for the viewing side polarizing plate.
The back side polarizing plate used in Comparative Example 1 was used as the back side polarizing plate.

  The thickness of the viewing side polarizing plate was 52 μm, the thickness of the back side polarizing plate was 91 μm, and the thickness ratio was 0.57.

[Comparative Example 3]
The viewing side polarizing plate used in Example 2 was used as the viewing side polarizing plate.

The back side polarizing plate was produced as follows. A polarizer having a thickness of 12 μm was prepared in the same manner as in Example 1 except that the temperature of the aqueous solution composed of potassium iodide / boric acid / water was 65 ° C., and the aqueous adhesive described in Example 1 was applied to both sides thereof. As a protective film, a 25 μm thick triacetyl cellulose film (trade name “KC2UA” manufactured by Konica Minolta Opto Co., Ltd.) and a non-stretched 15 μm thick norbornene film (trade name “manufactured by JSR Corporation”) ARTON (registered trademark) ”, in-plane retardation value R ₀ = 0 nm, thickness direction retardation value R _th = 0 nm at a wavelength of 590 nm. The polarizing plate was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. A 5 μm-thick adhesive (trade name “# L2” manufactured by Lintec Corporation) is bonded to the triacetyl cellulose film surface, and a 26 μm-thick brightness enhancement film (trade name manufactured by 3M “Advanced Polarized Film, Version 3) was bonded, and then a 20 μm thick adhesive (trade name “#KT” manufactured by Lintec Corporation) was bonded to the norbornene-based film side to obtain a back side polarizing plate at a temperature of 40 ° C. Under the condition of a relative humidity of 90%, the moisture permeability of the triacetyl cellulose film was 1200 g / (m ² · 24 hr), and the moisture permeability of the norbornene film was 140 g / (m ² · 24 hr).

  The thickness of the viewing side polarizing plate was 67 μm, the thickness of the back side polarizing plate was 83 μm, and the thickness ratio was 0.81.

[Comparative Example 4]
The viewing side polarizing plate used in Example 2 was used as the viewing side polarizing plate.

  The back side polarizing plate was produced as follows. First, a polyvinyl alcohol film having a thickness of 60 μm (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further, while maintaining a tension state, After immersing in pure water of 1 ° C. for 1 minute, it was immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 65 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer having a thickness of 23 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

Next, the aqueous adhesive described in Example 1 was applied to both sides of the 23 μm polarizer, and a 40 μm thick triacetyl cellulose film (trade name “KC4UY” manufactured by Konica Minolta Opto Co., Ltd.) was used as a protective film. Then, an unstretched 23 μm-thick norbornene-based film [trade name “ZEONOR (registered trademark)” manufactured by Nippon Zeon Co., Ltd.] was bonded. The polarizing plate was dried at 80 ° C. for 5 minutes and then cured at 40 ° C. for 168 hours. Thereafter, a 5 μm-thick adhesive (trade name “# L2” manufactured by Lintec Corporation) is pasted on the triacetylcellulose film surface, and a 26 μm-thick brightness enhancement film (trade name “3M product” Advanced Polarized) Film, Version 3) was pasted, and then a 20 μm thick adhesive (trade name “#KT” manufactured by Lintec Corporation) was pasted on the norbornene-based film side to obtain a back side polarizing plate. ° C., under the conditions of 90% relative humidity, the moisture permeability of the triacetyl cellulose film is ^{830g / (m 2 · 24hr)} , the moisture permeability of the norbornene-based film was 6g / (m ² · 24hr) .

  The thickness of the viewing side polarizing plate was 67 μm, the thickness of the back side polarizing plate was 116 μm, and the thickness ratio was 0.58.

  The results are shown in Table 1.

  ADVANTAGE OF THE INVENTION According to this invention, since the curvature in the high temperature environment in a liquid crystal panel can be eliminated and the liquid crystal panel which can be accommodated in the housing | casing of the final product in a high temperature environment can be obtained, it is useful.

DESCRIPTION OF SYMBOLS 10 1st polarizing plate, 11 2nd polarizing plate 20, 21 Polarizer 30a, 30b, 31a, 31b Protective film 32, 33 Adhesive layer 60 F1
61 F2
62 F3
63 F4
70 liquid crystal layer 71 substrate 72 liquid crystal cell

Claims (6)

In a set of polarizing plates having a first polarizing plate disposed on the viewing side of the liquid crystal cell and a second polarizing plate disposed on the back side of the liquid crystal cell,
The second polarizing plate has a reflective polarizing film,
When the first polarizing plate is held at 80 ° C. for 4 hours, the contraction force per 2 mm width in the absorption axis direction is F1, and the contraction force per 2 mm width in the transmission axis direction is F2.
When the contraction force per 2 mm width in the absorption axis direction when the second polarizing plate is held at 80 ° C. for 4 hours is F3, and the contraction force per 2 mm width in the transmission axis direction is F4, (F1 × F2 ) / (F3 × F4) is a set of polarizing plates of 0.5 to 5.0.   2. The polarizing plate according to claim 1, wherein each of the first polarizing plate and the second polarizing plate has a polarizer made of a polyvinyl alcohol-based resin film, and the thickness of each of the polarizers is 20 μm or less. Set.   The set of polarizing plates according to claim 2, wherein the thickness of the polarizer of the first polarizing plate is 10 µm or more, and the thickness of the polarizer of the second polarizing plate is 10 µm or less.   The set of polarizing plates according to claim 2 or 3, wherein the second polarizing plate has a protective film laminated on one surface of the polarizer and the reflective polarizer laminated on the other surface. The set of polarizing plates according to claim 4, wherein the moisture permeability of the protective film is 500 g / (m ² · 24 hr) or less.   A liquid crystal panel comprising the set of polarizing plates according to claim 1 and a liquid crystal cell, wherein the thickness of the liquid crystal cell is 0.4 mm or less.

Images