JP2021036328A - Polarizing plate set and liquid crystal panel - Google Patents

Abstract

To provide a polarizing plate set capable of suppressing warpage of a liquid crystal panel in a high temperature environment, and a liquid crystal panel manufactured by bonding the polarizing plate set to a liquid crystal cell.SOLUTION: The polarizing plate set comprises a visible side polarizing plate disposed on a visible side of a liquid crystal cell and a back side polarizing plate disposed on a back side of the liquid crystal cell. The back side polarizing plate has a laminated structure of a luminance improving film and an absorptive polarizing plate; and when the polarizing plate is disposed on the back side of the liquid crystal cell, a distance from the surface of the plate in contact with the liquid crystal cell to the luminance improving film is 100 μm or less. A ratio of a dimensional change rate in an absorption axis direction of the visible side polarizing plate when heated at 85°C for 100 hours, to a dimensional change rate in an absorption axis direction of the absorptive polarizing plate included in the back side polarizing plate when heated at 85°C for 100 hours, is 0.62 or more and 1.25 or less.SELECTED DRAWING: Figure 1

Description

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

In recent years, low power consumption, low voltage operation, lightweight and thin liquid crystal displays have rapidly become widespread as information display devices such as mobile phones, personal digital assistants, computer monitors, and televisions. With the development of liquid crystal technology, various modes of liquid crystal displays have been proposed, and problems of 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 required.

As the liquid crystal panel becomes thinner, there is a problem that the liquid crystal panel warps due to shrinkage of the polarizing plate attached to the liquid crystal cell in a high temperature environment and does not fit in the housing of the final product.

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 arranged on the side (rear side) opposite to the visual side of the liquid crystal cell and the visual side of the liquid crystal cell. A method for suppressing the warp of the panel has been developed. For example, in Japanese Patent Application Laid-Open No. 2012-58429 (Patent Document 1), the thickness of the polarizing film (polarizing film in the present invention) of the polarizing plate arranged on the visible side of the liquid crystal cell is arranged on the back side of the liquid crystal cell. A method of suppressing warpage of a liquid crystal display panel by making it thinner than a polarizing film is described.

Further, in Japanese Patent Application Laid-Open No. 2013-37115 (Patent Document 2), an optical polarizing film (polarizing film referred to in the present invention) included in an optical laminate on the viewing side is arranged on the side opposite to the viewing side. A method of suppressing warpage of a liquid crystal panel by making it thicker than the polarizing film contained in the laminate by 5 μm or more has been proposed. However, there is still a lot of room for improvement in suppressing the warp of the liquid crystal panel.

Japanese Unexamined Patent Publication No. 2012-58429 Japanese Unexamined Patent Publication No. 2013-37115

An object of the present invention is to provide a set of polarizing plates capable of suppressing warpage of a liquid crystal panel in a high temperature environment, and a liquid crystal panel formed by bonding the set of polarizing plates to a liquid crystal cell.

[1] A set of a viewing-side polarizing plate arranged on the viewing side of the liquid crystal cell and a back-side polarizing plate arranged on the back side of the liquid crystal cell.
The back side polarizing plate has a structure in which a brightness improving film and an absorption type polarizing plate are laminated, and the distance from the surface in contact with the liquid crystal cell to the brightness improving film when arranged on the back side of the liquid crystal cell. Is 100 μm or less,
The dimensional change rate in the absorption axis direction when the viewing side polarizing plate is heated at 85 ° C. for 100 hours, and the absorption axis direction when the absorption type polarizing plate contained in the back surface side polarizing plate is heated at 85 ° C. for 100 hours. A set of polarizing plates whose ratio to the dimensional change rate is 0.62 or more and 1.25 or less.
[2] The viewing-side polarizing plate and the back-side polarizing plate each have a polarizing film.
The set of polarizing plates according to [1], wherein both the thickness of the polarizing film of the viewing-side polarizing plate and the thickness of the polarizing film of the back-side polarizing plate are 15 μm or less.
[3] The absorption axis of the viewing side polarizing plate is substantially parallel to the long side direction of the liquid crystal cell, and the absorption axis of the back surface side polarizing plate is substantially parallel to the short side direction of the liquid crystal cell. The set of polarizing plates according to [1] or [2].
[4] The liquid crystal cell and the set of the polarizing plate according to any one of [1] to [3] are included.
The viewing side polarizing plate is arranged on the viewing side of the liquid crystal cell, and the back surface side polarizing plate is arranged on the back side of the liquid crystal cell, and the absolute value of the amount of warpage when heated at 85 ° C. for 240 hours is determined. A liquid crystal panel of 0.5 mm or less.

According to the present invention, it is possible to eliminate the warp of the liquid crystal panel in a high temperature environment, and it is possible to obtain a liquid crystal panel that fits in the housing of the final product even in a high temperature environment.

It is the 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 the 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 the 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 the schematic of an example of the reflection polarizing film used in this invention.

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

The set of polarizing plates of the present invention is composed of a viewing side polarizing plate 30 and a back surface side polarizing plate 60. The layer structure of the viewing side polarizing plate 30 and the back surface side polarizing plate 60 according to the present invention will be described with reference to FIG. In FIG. 1, the viewing-side polarizing plate 30 has protective films 31a and 31b bonded to both sides of the polarizing film 32, respectively. It is also useful to form a surface treatment layer on the surface of the protective film 31a opposite to the surface to be bonded to the polarizing film 32. Regarding the back side polarizing plate 60, in the present invention, the absorption type polarizing plate 50 has a protective film on at least one surface of the polarizing film 52, and as shown in FIG. 1, protective films 51a and 51b are provided on both sides of the polarizing film 52. It may be formed by laminating. Further, the brightness improving film 61 is laminated on the absorption type polarizing plate 50 via the adhesive layer 54 to form the back side polarizing plate 60. These polarizing plates are attached to the liquid crystal cell via the pressure-sensitive adhesive layers 33 and 53, respectively, to form a liquid crystal panel.

In the back-side polarizing plate, the distance from the liquid crystal cell to the brightness improving film 61 is 100 μm or less, preferably 90 μm or less, more preferably 80 μm or less, and may be 60 μm or less. The lower limit is not particularly limited, but is usually 5 μm or more, and more typically 10 μm or more. Further, the rate of dimensional change in the absorption axis direction when the viewing side polarizing plate 30 is heated at 85 ° C. for 100 hours and the absorption type polarizing plate 50 included in the back surface side polarizing plate when heated at 85 ° C. for 100 hours. The ratio to the dimensional change rate in the absorption axis direction is 0.62 or more and 1.25 or less, preferably 0.65 or more and 1.2 or less, and more preferably 0.75 or more and 1.15 or less. preferable. In the present invention, the distance from the liquid crystal cell to the brightness improving film corresponds to the surface of the backside polarizing plate in contact with the liquid crystal cell (for example, in FIGS. 1 to 3, the surface of the pressure-sensitive adhesive layer 53 in contact with the liquid crystal cell corresponds to this). It refers to the distance from the surface of the brightness improving film to the surface on the liquid crystal cell side.

The amount of warpage of the liquid crystal panel is greatly affected by the brightness improving film arranged on the outermost layer from the liquid crystal cell. Therefore, the distance between the liquid crystal panel and the brightness improving film satisfies the above, and the absorption type polarizing plate 50 included in the viewing side polarizing plate 30 and the back side polarizing plate is heated at 85 ° C. for 100 hours in the absorption axis direction. By setting the dimensional change rate within the above range, the amount of warpage of the liquid crystal panel can be reduced.

As shown in FIGS. 2 and 3, in the present invention, since the brightness improving film is brought closer to the liquid crystal cell, the absorption type polarizing plate 50 included in the back side polarizing plate 60 has a protective film only on one side of the polarizing film. This is also a preferable configuration. By arranging the brightness improving film at a position close to the liquid crystal cell in this way, it is possible to reduce the influence of the force generated by the dimensional change of the brightness improving film on the warp of the liquid crystal panel.

Further, the viewing side polarizing plate has an arrangement in which its absorption axis is substantially parallel to the long side direction of the liquid crystal cell, and the back surface side polarizing plate has an arrangement in which its absorption axis is substantially parallel to the short side direction of the liquid crystal cell. Is preferable. Approximately 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. It is more preferably 1 ° or less. With such an axial configuration, the warp of the liquid crystal panel can be reduced more remarkably.

Further, according to the present invention, there is also provided a liquid crystal panel in which the above-mentioned viewing side polarizing plate 30 and back side polarizing plate 60 are laminated on a liquid crystal cell via an adhesive layer.

Hereinafter, the set of the polarizing plate of the present invention and the members constituting the liquid crystal panel will be described in detail. Further, the polarizing film 32 included in the viewing-side polarizing plate and the polarizing film 52 included in the back-side polarizing plate may be collectively referred to simply as a polarizing film, and the protective film 31a, the protective film 31b, and the protective film 51a are protected. The film 51b may be collectively referred to simply as a protective film.

[Polarizing films 32, 52]
As the polarizing films 32 and 52, any suitable one can be used as long as the above-mentioned dimensional change rate and the thickness of the polarizing film are satisfied. 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, and a polyvinyl having the dichroic dye adsorbed. It is produced through a step of treating an alcohol-based resin film with an aqueous boric acid solution and cross-linking the film, and a step of washing with water after the cross-linking treatment with the aqueous boric acid solution.

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

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

The longitudinal uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with a dichroic dye, at the same time as dyeing, or after dyeing. When the longitudinal uniaxial stretching is performed after dyeing, the longitudinal uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Of course, longitudinal uniaxial stretching can also be performed at the plurality of stages shown here. For the longitudinal uniaxial stretching, a method of uniaxial stretching between rolls having different peripheral speeds, a method of uniaxial stretching using a thermal roll, and the like can be adopted. Further, the longitudinal uniaxial stretching may be carried out by dry stretching in which stretching is performed in the atmosphere, or by wet stretching in which the polyvinyl alcohol-based resin film is swollen using a solvent such as water. The draw ratio is usually about 3 to 8 times.

The polyvinyl alcohol-based resin film can be dyed with a dichroic dye, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. The polyvinyl alcohol-based resin film is preferably subjected to a treatment of swelling by immersing it in water before the dyeing treatment.

When iodine is used as the dichroic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted. 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. Is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. The immersion time (staining 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 a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye and dyeing is usually adopted. 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 aid. The temperature of the dichroic organic dye aqueous solution used for dyeing is usually about 20 to 80 ° C. The immersion time (staining time) in this aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye can be performed by immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution. The content of boric acid 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 pigment, 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., and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by immersing the boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of water in the 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 treatment 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 the drying treatment is usually about 30 to 100 ° C, preferably 50 to 80 ° C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to a practical level. The water content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the polarizing film loses its flexibility and may be damaged or broken after drying. Further, when the water content exceeds 20% by weight, the thermal stability tends to be insufficient.

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

Further, the stretching, dyeing, boric acid treatment, washing step, and drying step of the polyvinyl alcohol-based resin film in the polarizing film manufacturing step may be performed according to the method described in, for example, Japanese Patent Application Laid-Open No. 2012-159778. .. In the method described in this document, it is also useful to use a method of forming a polyvinyl alcohol-based resin layer to be a polarizing film by coating a base film with a polyvinyl alcohol-based resin.

In order to suppress the shrinkage force of the polarizing film to a low level and to obtain a desired dimensional change rate of the polarizing plate, the thickness of the polarizing film is preferably 15 μm or less, and may be less than 15 μm. The thickness of the polarizing film is usually 3 μm or more in that good optical characteristics can be imparted.

[Protective films 31a, 31b, 51a, 51b]
As the protective films 31a, 31b, 51a, 51b, those formed of an appropriate transparent resin can be used. Specifically, it is preferable to use a polymer having excellent transparency, uniform optical properties, mechanical strength, thermal stability, and the like. Examples of such a transparent resin film 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. Acrylic film, polycarbonate film, polyether sulfone film, polysulfone film, polyimide film, polyolefin film, polynorbornene film and the like can be used, but the present invention is not limited thereto.

The protective films 31a and 31b applied to the viewing-side polarizing plate 30 and the protective films 51a and 51b applied to the back-side polarizing plate 60 may be independently the same or different. May be good.

Prior to bonding the above-mentioned protective film to the polarizing film, the bonded surface may be subjected to an easy-adhesion treatment such as a saponification treatment, a corona treatment, a primer treatment, or an anchor coating treatment. 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, and more preferably 40 μm or less.

Further, a coating layer (surface treatment layer 35) can be provided on the outer surface of the protective film 31a in order to impart desired surface optical characteristics 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.

Further, the protective film 31a may use a retardation plate for improving visibility when the screen is viewed through polarized sunglasses. It is desirable to arrange a λ / 4 wave plate as a retardation plate from the viewpoint of improving visibility. Further, when laminating with a long polarizing film, it is preferable that the angle formed by the long side in the long side direction is stretched to approximately 45 ° or 135 ° because a polarizing plate can be produced by roll-to-roll.

When the liquid crystal cell is in the transverse electrolysis (IPS: In-Plane Switching) mode, the protective film 31b and the protective film 51b are positioned in the thickness direction so as not to impair the wide viewing angle characteristics originally possessed by the IPS mode liquid crystal cell. The phase difference value Rth is preferably in the range of -10 to 10 nm. Further, the in-plane retardation value Re is also preferably in the range of -10 to 10 nm.

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

In the equation, nx is the refractive index in the in-plane x-axis direction (in-plane slow-phase axial direction), and ny is the in-plane y-axis direction (in-plane advancing axial direction, x in-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 can be a value at an arbitrary wavelength in the range of about 500 to 650 nm near the center of visible light, but in the present specification, the phase difference value at a wavelength of 590 nm is used as a standard. The phase difference value Rth in the thickness direction and the in-plane phase difference value Re can be measured using various commercially available phase difference meters.

As a method of controlling the retardation value Rth in the thickness direction of the protective film within the range of -10 to 10 nm, there is a method of minimizing the distortion remaining in the plane and in the thickness direction when the film is produced. For example, in the solvent casting method, a method of relaxing the residual shrinkage strain in the in-plane and thickness directions generated when the cast resin solution is dried by heat treatment can be adopted. On the other hand, in the melt extrusion method, in order to prevent the resin film from being extruded from the die and stretched during cooling, the distance from the die to the cooling drum is shortened as much as possible, 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 adopted. Further, as in the solvent casting method, a method of alleviating the strain remaining on the obtained film by heat treatment can also be adopted.

[Brightness improving film 61]
The back side polarizing plate 60 of the present invention has a structure in which a brightness improving film 61 and an absorption type polarizing plate 50 are laminated. A typical example of the brightness improving film 61 is a linearly polarized light separation type reflective polarizing film. FIG. 4 is a schematic cross-sectional view of an example of the reflective polarizing film used in the present invention. The reflective polarizing film 61 is a multi-layer laminated body 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 of the B layer and the refractive index ny in the y-axis direction are substantially the same. It is the same. Therefore, the difference in refractive index between the A layer and the B layer is large in the x-axis direction and 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 stretching direction of the reflective polarizing film.

The layer A is preferably composed of a material that exhibits birefringence by stretching. Representative examples of such materials include polyester naphthalenedicarboxylic acid (eg, polyethylene naphthalate), polycarbonate and acrylic resins (eg, polymethylmethacrylate). Polyethylene naphthalate is preferred. The B layer is preferably composed 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 polarizing film 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. (For example, s wave) is reflected. At the interface between the A layer and the B layer, the reflected light is partially transmitted as light having a first polarization direction and partially reflected as light having a second polarization direction. By repeating such reflection and transmission in large numbers inside the reflective polarizing film, it is possible to improve the efficiency of light utilization.

Preferably, the reflective polarizing film 61 includes a reflective layer R as the outermost layer opposite to the polarizing film 52. By providing the reflective layer R, it is possible to further utilize the light that has returned to the outermost side of the reflective polarizing film without being finally utilized, so that the efficiency of light utilization can be further improved. 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 polarizing film can be appropriately set according to the purpose, the total number of layers contained in the reflective polarizing film, and the like. From the viewpoint of suppressing dimensional changes in a high temperature environment, the total thickness of the reflective polarizing film is preferably 15 μm to 50 μm, more preferably 30 μm or less.

As the reflective polarizing film, for example, those described in JP-A-9-507308 can be used.

As the reflective polarizing film 61, a commercially available product may be used as it is, or the commercially available product may be used after secondary processing (for example, stretching). Examples of commercially available products include trade names DBEF and APF manufactured by 3M.

[Attachment of polarizing film and protective film]
The polarizing film and the protective film can be bonded with an adhesive or an adhesive. The thickness of the adhesive layer for bonding the polarizing film and the protective film can be about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. When the thickness of the adhesive layer is within this range, floating or peeling does not occur between the laminated protective film and the polarizing film, and a practically acceptable adhesive force can be obtained. The thickness of the pressure-sensitive adhesive layer for laminating the polarizing film and the protective film can be about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.

When adhering the polarizing film to the protective film, it is also useful to preliminarily perform a saponification treatment, a corona treatment, a plasma treatment, or the like on the polarizing film or the protective film.

For the formation of the adhesive layer, an appropriate adhesive can be appropriately used depending on the type and purpose of the adherend, and an anchor coating agent can also be used if necessary. Examples of the adhesive include solvent-based adhesives, emulsion-type adhesives, pressure-sensitive adhesives, re-wet-sensitive adhesives, polycondensation-type adhesives, solvent-free adhesives, film-like adhesives, and hot-melt adhesives. Can be mentioned.

As one of the preferable adhesives, a water-based adhesive, that is, one in which the adhesive component is dissolved or dispersed in water can be mentioned. Examples of adhesive components that are soluble in water include polyvinyl alcohol-based resins. Further, to give an example of an adhesive component that can be dispersed in water, there is a urethane-based resin having a hydrophilic group. Water-based adhesives can be prepared by mixing such adhesive components with water, along with additional additives to be added as needed. Examples of commercially available polyvinyl alcohol-based resins that can be water-based adhesives include "KL-318", which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

The water-based adhesive may contain a cross-linking agent, if necessary. Examples of cross-linking agents include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts. When a polyvinyl alcohol-based resin is used as an adhesive component, an aldehyde compound such as glyoxal, a methylol compound such as methylol melamine, and a water-soluble epoxy resin are preferably used as the cross-linking agent. Here, the water-soluble epoxy resin is a polyamide obtained by reacting a polyamide polyamine, which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine with a dicarboxylic acid such as adiponic acid, with epichlorohydrin. It can be an epoxy resin. Examples of commercially available water-soluble epoxy resins include "Sumirace Resin (registered trademark) 650 (30)" sold by Taoka Chemical Industry Co., Ltd.

A polarizing plate can be obtained by applying a water-based adhesive to the adhesive surface of the polarizing film and / or the protective film bonded thereto, bonding the two, and then performing a drying treatment. Prior to bonding, it is also effective to apply an easy-adhesion treatment such as a saponification treatment, a corona discharge treatment, a plasma treatment, or a primer treatment to the protective film to improve the wettability. The drying temperature can be, for example, about 50 to 100 ° C. After the drying treatment, curing at a temperature slightly higher than room temperature, for example, about 30 to 50 ° C. for about 1 to 10 days is preferable in order to further enhance the adhesive strength.

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 bonding between the polarizing film and the protective film is performed by irradiating the coating layer of the adhesive composition with active energy rays or applying heat to the curable epoxy compound contained in the adhesive. Can be done by a method of curing. Curing of the epoxy compound is generally performed by cationic polymerization of the epoxy compound. 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 polymerization, etc., the epoxy compound contained in the curable adhesive composition preferably does not contain an aromatic ring in the molecule. Examples of the epoxy compound containing no aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. The epoxy compound preferably used for such a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline will be described here as well.

The hydrogenated epoxy compound is a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction on an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound in the presence of a catalyst and under pressure. It can be etherified. Aromatic polyhydroxy compounds that are raw materials for aromatic epoxy compounds include, for example, bisphenols such as bisphenol A, bisphenol F, and bisphenol S; phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolac resin. Novolac-type resins; polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. By conducting a nuclear hydrogenation reaction on such an aromatic polyhydroxy compound and reacting the obtained nuclear hydrogenated polyhydroxy compound with epichlorohydrin, glycidyl etherification can be achieved. Suitable hydrogenated epoxy compounds include glycidyl ethers of hydrogenated bisphenol A.

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

_{A compound in which a group in which one or more hydrogen atoms in (CH 2} ) _m are removed in this formula is bonded to another chemical structure can be an alicyclic epoxy compound. _{Further, one or more hydrogen atoms in (CH 2} ) _m forming an alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, epoxy compounds having an oxabicyclohexane ring (m = 3 in the above formula) and an oxabicycloheptane ring (m = 4 in the above formula) have excellent adhesiveness. It is preferably used because it shows. Specific examples of the alicyclic epoxy compound are given below. Here, the compound names are listed first, and then the chemical formulas corresponding to the respective compounds are shown, and the compound names and the corresponding chemical formulas are given the same reference numerals.

A: 3,4-Epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-Epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate), D: bis (3,4-epoxycyclohexylmethyl) adipate, E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate, F: diethylene glycol Bis (3,4-epoxycyclohexylmethyl ether), G: ethylene glycol bis (3,4-epoxycyclohexylmethyl ether), H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxa Trispiro [5.2.2.5.2.2] Henikosan, I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane, J: 4-Vinylcyclohexanedioxide, K: limonendioxide, L: bis (2,3-epoxycyclopentyl) ether, M: dicyclopentadiendioxide, etc.

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

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

The epoxy compound used in the 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, the flexibility of the polarizing plate after curing may decrease or the adhesive strength may decrease. On the other hand, a compound having an epoxy equivalent of more than 3,000 g / equivalent may reduce the compatibility with other components contained in the adhesive composition.

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 add a cationic polymerization initiator to the curable adhesive composition containing the epoxy compound. The cationic polymerization initiator generates a cationic species or Lewis acid by irradiation or heating with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates a polymerization reaction of an epoxy group. From the viewpoint of workability, it is preferable that the cationic polymerization initiator has a potential. Hereinafter, a cationic polymerization initiator that generates a cationic species or Lewis acid by irradiation with an active energy ray and initiates a polymerization reaction of an epoxy group is referred to as a "photocationic polymerization initiator", and a cationic species or Lewis acid is generated by heat. , A cationic polymerization initiator that initiates the polymerization reaction of an epoxy group is referred to as a "thermal cationic polymerization initiator".

The method of curing the adhesive composition by irradiating with active energy rays using a photocationic polymerization initiator enables curing at normal temperature and humidity, reducing the need to consider the heat resistance of the polarizing film or the strain due to expansion. However, it is advantageous in that the protective film and the polarizing film can be adhered well. Further, since the photocationic polymerization initiator acts catalytically with 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 blending amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and preferably 15 parts by weight or less with respect to 100 parts by weight of the epoxy compound. If the blending amount of the photocationic polymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy compound, the curing tends to be insufficient, and the mechanical strength and the adhesive strength of the cured product tend to decrease. On the other hand, when the blending amount of the photocationic polymerization initiator exceeds 20 parts by weight with respect to 100 parts by weight of the epoxy compound, the amount of ionic substances in the cured product increases, so that the hygroscopicity of the cured product increases, and the durability performance becomes high. May decrease.

When a photocationic polymerization initiator is used, the curable adhesive composition may further contain a photosensitizer, if desired. 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, photoreducing dyes and the like. When the photosensitizer is blended, the amount thereof is preferably in the range of 0.1 to 20 parts by weight with respect to 100 parts by weight of the curable adhesive composition. Further, a sensitizing aid such as a naphthoquinone derivative may be used to improve the curing rate.

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

The curable adhesive composition containing the epoxy compound is preferably cured by photocationic polymerization as described above, but the above-mentioned thermal cationic polymerization initiator may be present and cured by thermal cationic polymerization, or light Cationic polymerization and thermal cationic polymerization can also be used in combination. When photocationic polymerization and thermal cationic polymerization are used in combination, it is preferable that the curable adhesive composition contains both a photocationic polymerization initiator and a thermal cationic polymerization initiator.

In addition, 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 the oxetane compound is blended, the amount thereof is usually 5 to 95% by weight, preferably 5 to 50% by weight in the curable adhesive composition. Further, the polyol compound may be alkylene glycol or an oligomer thereof including ethylene glycol, hexamethylene glycol, polyethylene glycol and the like, 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 the curable adhesive composition.

Further, the curable adhesive composition is filled with other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, as long as the adhesiveness is not impaired. It can contain agents, flow conditioners, plasticizers, antifoaming agents and the like. Examples of the ion trapping agent include powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and inorganic compounds including a mixture thereof, and examples of the antioxidant include antioxidants. , Hindered phenolic antioxidants and the like.

A curable adhesive composition containing an epoxy compound is applied to the adhesive surface of a polarizing film or a protective film, or both of these adhesive surfaces, and then bonded to the coated surface of the adhesive to generate active energy rays. The uncured adhesive layer can be cured by irradiating or heating the film to bond the polarizing film and the protective film. As an adhesive coating method, 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 since each coating method has an optimum viscosity range, the viscosity can be adjusted. May contain a solvent for this purpose. The solvent is preferably an organic solvent that satisfactorily dissolves each component including an epoxy compound without deteriorating the optical performance of the polarizing film. For example, hydrocarbons typified by toluene and ethyl acetate typified. Esters and the like can be used.

When the adhesive composition is cured by irradiation with active energy rays, the various active energy rays described above can be used, but since it is easy to handle and the amount of irradiation light can be easily controlled, ultraviolet rays are emitted. It is preferably used. The irradiation intensity and irradiation amount of active energy rays, for example, ultraviolet rays, do not affect various optical performances such as the degree of polarization of the polarizing film and various optical performances such as the transparency and retardation characteristics of the protective film. Therefore, it is appropriately determined so that an appropriate productivity can be maintained.

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

[Adhesive]
The pressure-sensitive adhesive may be any pressure-sensitive adhesive having excellent optical transparency and excellent pressure-sensitive adhesive properties including appropriate wettability, cohesiveness, adhesiveness, etc., but more preferably one having excellent durability and the like. Specifically, as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferable.

The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin containing an acrylic acid alkyl ester as a main monomer, such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate. Polar monomers are usually copolymerized with this acrylic resin. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group, wherein the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and is also polar functional. 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 ( There are meta) acrylate, glycidyl (meth) acrylate and the like.

Further, the acrylic pressure-sensitive adhesive usually contains a cross-linking agent together with the acrylic resin. As a typical example of the cross-linking agent, an isocyanate compound having at least two isocyanato groups (-NCO) in the molecule can be mentioned.

Various additives may be further blended in the pressure-sensitive adhesive. Suitable additives include silane coupling agents, antistatic agents and the like. Silane coupling agents are effective in increasing the adhesive force 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 the pressure-sensitive adhesive composition directly on a polarizing film or a protective film, and drying and removing the solvent. Alternatively, the above pressure-sensitive adhesive composition is applied to the mold-released surface of the base film made of the resin film that has been subjected to the mold-release treatment, and the solvent is dried and removed to form an pressure-sensitive adhesive layer, which is then placed on the transparent protective film. It can be formed by a method of sticking and transferring the pressure-sensitive adhesive layer. When an adhesive layer is formed on a transparent protective film by the former direct coating method, a resin film (also called a separator) that has undergone a mold release treatment is attached to the surface of the adhesive layer, and the surface of the adhesive layer is kept until use. It is customary to protect the temporary wear. From the viewpoint of handleability of the pressure-sensitive adhesive composition which is an organic solvent solution, the latter transfer method is often adopted. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also convenient in that it can be used as a separator as it is after being attached to a polarizing plate.

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

[Adhesive layers 33, 53, adhesive layer 54]
An adhesive layer can be used for bonding the polarizing plate and the liquid crystal cell, and an adhesive or an adhesive can be used for bonding the absorbent polarizing plate 50 and the brightness improving film 61. It is preferable to use an adhesive for bonding. The pressure-sensitive adhesive layer may have excellent optical transparency and excellent pressure-sensitive adhesive properties including appropriate wettability, cohesiveness, adhesiveness, etc., but more preferably one having excellent durability and the like. Specifically, as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferable.

As the pressure-sensitive adhesive layer, a layer equivalent to that used for bonding the above-mentioned polarizing film and the protective film can be used. As the pressure-sensitive adhesive, different ones may be used or similar ones may be used.

Before laminating the pressure-sensitive adhesive on the polarizing plate, it is also useful to perform corona treatment, plasma treatment, or the like in advance on the polarizing film surface, the protective film surface, and the pressure-sensitive adhesive surface. Further, when laminating the brightness improving film, it is also useful to perform corona treatment, plasma treatment, or the like in advance on the bonding surface and the pressure-sensitive adhesive surface of the brightness improving film 61. From the viewpoint of bringing the brightness improving film 61 closer to the liquid crystal cell, the pressure-sensitive adhesive layer used for laminating the brightness improving film 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.

In the set of the polarizing plates of the present invention described above, the absorption axis of the polarizing film 32 is substantially parallel to the long side direction of the liquid crystal cell in the viewing side polarizing plate 30, and the polarizing film 52 in the back surface side polarizing plate 60. It is preferable that the absorption axis of the liquid crystal cell is substantially parallel to the short side direction of the liquid crystal cell.

[Liquid crystal cell]
The liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the substrate. The cell substrate is generally 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 shall be composed of various types used in this field (for example, known drive modes such as IPS mode, VA mode, TN mode, etc.). Can be done.

[Liquid crystal panel]
A liquid crystal panel can be manufactured by adhering a polarizing plate to a liquid crystal cell via an adhesive layer.

In the liquid crystal panel of the present invention, the distance from the liquid crystal cell to the brightness improving film is 100 μm or less, and the dimensional change rate in the absorption axis direction when the viewing side polarizing plate is heated at 85 ° C. for 100 hours is included in the back side polarizing plate. A set of polarizing plates having a ratio of 0.62 or more to 1.25 or less in the absorption axis direction when the absorption type polarizing plate is heated at 85 ° C. for 100 hours is used. From another point of view, in the liquid crystal panel of the present invention, the absolute value of the amount of warpage when heated at 85 ° C. for 240 hours is 0.5 mm or less, preferably 0.3 mm or less. By attaching such a set of polarizing plates to a liquid crystal cell, the liquid crystal panel of the present invention is a liquid crystal display panel that is suppressed from warping in a high temperature environment and fits in the housing of the final product.

The liquid crystal panel of the present invention is particularly preferably used for small and medium-sized liquid crystal display devices that are often exposed to high temperatures such as outdoors. For example, it is suitable when the size of the liquid crystal panel is 15 inches or less diagonally.

Further, the distance from the liquid crystal cell to the luminance improving film is preferably 90 μm or less, more preferably 80 μm or less, and 60 μm or less in that the warp of the liquid crystal panel in a high temperature environment can be further reduced. May be good. The ratio of the dimensional change rate in the absorption axis direction when the viewing side polarizing plate is heated at 85 ° C. for 100 hours is the ratio of the dimensional change rate in the absorption axis direction when the back surface polarizing plate is heated at 85 ° C. for 100 hours. It is preferably 0.65 or more and 1.2 or less, and more preferably 0.7 or more and 1.15 or less.

The dimensional change rate in the absorption axis direction when the viewing side polarizing plate is heated at 85 ° C. for 100 hours is preferably 0.8% or more, more preferably 1.0% or more. Further, the dimensional change rate in the absorption axis direction when the absorption type polarizing plate contained in the back side polarizing plate is heated at 85 ° C. for 100 hours is preferably 1.4% or less, more preferably 1.3% or less. .. The dimensional change rate in the absorption axis direction of the polarizing plate is controlled, for example, by adjusting the length and temperature of the drying process after the protective film is attached to the polarizing film, the thickness of the polarizing film, the draw ratio of the polarizing film, and the like. can do.

Further, it is also useful to adjust the dimensional change rate in the absorption axis direction of the polarizing plate by performing a heat treatment in the range of 40 ° C. to 80 ° C. after producing the polarizing plate. From the viewpoint of avoiding poor appearance due to rapid shrinkage of the polarizing plate, it is more preferable to perform the heat treatment in the range of 40 ° C. to 60 ° C.

The dimensional change rate in the absorption axis direction when the polarizing plate was heated at 85 ° C. for 100 hours was measured as follows. First, the polarizing plate is cut into a size of 100 mm in the long direction x 100 mm in the width direction, left to stand in an environment of a temperature of 23 ° C. and a humidity of 55% for one day, and the dimension (L0) in the MD direction (absorption axis direction) is measured. To do. Next, the mixture is allowed to stand in an environment of 85 ° C. for 100 hours, and the dimension (L1) in the MD direction after being allowed to stand in a high temperature environment is measured. Based on the result, the dimensional change rate (%) was obtained from the formula (c).

Dimensional change rate = [(L0-L1) / L0] x 100 (c)

The ratio of the dimensional change rate can be obtained by the following formula (d) from the value of the dimensional change rate A of the viewing side polarizing plate and the dimensional change rate B of the absorption type polarizing plate included in the back side polarizing plate.

Ratio of dimensional change rate = A / B (d)

The layer structure of the polarizing plate for measuring the dimensional change rate is such that a protective film is bonded to one side or both sides of the polarizing film, and the adhesive layer and other films for bonding to the liquid crystal panel are Measure with the removed state. When the back-side polarizing plate is a laminate of the absorption-type polarizing plate and the brightness-improving film, the dimensions of the absorption-type polarizing plate before the brightness-improving film is attached or the absorption-type polarizing plate remaining after the brightness-improving film is removed. Measure the rate of change.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these examples. In the examples, the part and% indicating the content or the amount used are based on weight unless otherwise specified. The physical properties of each of the following examples were measured by the following methods.

(1) Thickness measurement:
The measurement was performed using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation and thickness direction retardation:
Using the phase difference meter "KOBRA (registered trademark) -WPR" manufactured by Oji Measuring Instruments Co., Ltd. based on the parallel Nicol rotation method, in-plane lettering and thickness direction lettering at a wavelength of 590 nm at a temperature of 23 ° C. It was measured.
(3) Measurement of Dimensional Change Rate Measurement was performed using a two-dimensional measuring instrument "NEXIV VMR-12072" manufactured by Nikon Corporation.
(4) Measurement of the amount of warpage of the polarizing plate After allowing the produced liquid crystal panel to stand in an environment of 85 ° C. for 240 hours, the two-dimensional measuring instrument "NEXIV VMR-12072" manufactured by Nikon Corporation with the polarizing plate on the viewing side facing up. Placed on the measuring table. Next, focus on the surface of the measuring table, use that as a reference, focus on the four corners of the liquid crystal panel, the center of each of the four sides, and the center of the liquid crystal panel surface, and measure the distance from the reference focus. , The distance from the measuring table that is the longest in absolute value is taken as the amount of warpage.

[Production Example 1] Preparation of polarizing film 1 A polyvinyl alcohol film having a thickness of 30 μm (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 4 times by dry stretching to further reduce tension. After immersing it in pure water at 40 ° C for 40 seconds while maintaining it, it is immersed in an aqueous solution with a weight ratio of iodine / potassium iodide / water of 0.052 / 5.7 / 100 at 28 ° C for 30 seconds for dyeing treatment. went. Then, 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 and then drying at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while holding the film at a tension of 300 N, iodine is adsorbed and oriented on the polyvinyl alcohol film. An absorbent polarizing film 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.] is dissolved in 100 parts by weight of water, and a water-soluble epoxy is dissolved in the aqueous solution. Add 1.5 parts by weight of a polyamide epoxy-based additive that is a resin [trade name "Smilase Resin (registered trademark) 650 (30)" obtained from Taoka Chemical Industry Co., Ltd., an aqueous solution with a solid content concentration of 30% by weight]. To prepare a water-based adhesive.

[Adhesives A and B]
The following two types of adhesives were prepared.
Adhesive A: Sheet adhesive with a thickness of 20 μm [“NCF # KT” manufactured by Lintec Corporation] Adhesive B: Sheet adhesive with a thickness of 5 μm [“NCF # L2” manufactured by Lintec Corporation] Adhesive C: Thickness 15 μm sheet adhesive [“NCF # L1” manufactured by Lintec Corporation]

[Protective films A, C, D]
The following four types of protective films were prepared.
Protective film A: Triacetyl cellulose film with hard coat manufactured by Konica Minolta Co., Ltd .; 25KCHCN-TC (thickness 32 μm)
Protective film C: Cyclic polyolefin resin film manufactured by Nippon Zeon Corporation; 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 D: Triacetyl cellulose film manufactured by Konica Minolta Co., Ltd .; KC2UA (thickness 25 μm)

[Brightness improvement film A]
The following brightness improving films were prepared.
Brightness improving film A: 26 μm thick brightness improving film (3M product name “Advanced Polarized Film, Version 3)”

[Manufacturing Example 3] Production of Visually Seen Polarizing Plate 1 The protective film A was subjected to a saponification treatment, and one surface of the protective film C was subjected to a corona treatment. The protective film A, the polarizing film 1, and the protective film C are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film A and the corona-treated surface of the protective film C are bonded surfaces to the polarizing film 1, respectively. , Drying treatment was carried out to obtain a viewing side polarizing plate 1.
The dimensional change rate of the viewing side polarizing plate 1 in the MD direction was 1.4%. The dimensional change rate was adjusted by adjusting the drying time in the above drying treatment.
Further, the pressure-sensitive adhesive A was bonded onto the protective film C of the viewing-side polarizing plate 1, to form a pressure-sensitive adhesive layer. At this time, the surface of the protective film and the surface of the adhesive were subjected to corona treatment in advance.

[Manufacturing Examples 4 to 10] Production of Visually Seen Polarizing Plates 2 to 8 Production Example 3 except that the drying time in the above drying process is adjusted so that the dimensional change rate in the MD direction (absorption axis direction) is different. The viewing side polarizing plates 2 to 8 were respectively produced in the same manner as in the above manner, and then the pressure-sensitive adhesive A was bonded onto the protective film C to form a pressure-sensitive adhesive layer. The dimensional change rates of the viewing side polarizing plates 2 to 8 were as follows.
Visualizing side polarizing plate 2: 1.28
Visualizing side polarizing plate 3: 1.11
Visualizing side polarizing plate 4: 1.05
Visualizing side polarizing plate 5: 0.99
Visualizing side polarizing plate 6: 0.88
Visualizing side polarizing plate 7: 1.63
Visualizing side polarizing plate 8: 0.76

[Manufacturing Example 11] Preparation of Backside Polarizing Plate 1 The protective film D was subjected to a saponification treatment, and one surface of the protective film C was subjected to a corona treatment. The protective film D, the polarizing film 1, and the protective film C are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film D and the corona-treated surface of the protective film C are bonded surfaces to the polarizing film 1, respectively. An absorbent polarizing plate was obtained. The dimensional change rate of the obtained absorption-type polarizing plate in the absorption axis direction was 1.25%. Next, the pressure-sensitive adhesive B was bonded to the protective film D surface of the obtained absorbent polarizing plate to form a pressure-sensitive adhesive layer. At this time, the surface of the protective film D and the surface of the adhesive B were subjected to corona treatment in advance. Next, the brightness improving film A was bonded to the surface of the pressure-sensitive adhesive B opposite to the surface to which the protective film D was bonded to prepare the back side polarizing plate 1. At this time, the surface of the brightness improving film A was subjected to corona treatment in advance.
The pressure-sensitive adhesive A was bonded to the protective film C surface of the back-side polarizing plate 1 thus obtained to form a pressure-sensitive adhesive layer. Also at this time, the surface of the protective film C and the surface of the adhesive A were subjected to corona treatment in advance.

[Manufacturing Example 12] Preparation of Backside Polarizing Plate 2 The protective film D was subjected to a saponification treatment, and one surface of the protective film C was subjected to a corona treatment. The protective film D, the polarizing film 1, and the protective film C are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film D and the corona-treated surface of the protective film C are bonded surfaces to the polarizing film 1, respectively. , Drying treatment was carried out to obtain an absorbent polarizing plate. The dimensional change rate of the obtained absorption-type polarizing plate in the absorption axis direction was 0.91%. The dimensional change rate was adjusted by adjusting the drying time in the above drying treatment. Next, the pressure-sensitive adhesive C was bonded to the protective film D surface of the obtained absorbent polarizing plate to form a pressure-sensitive adhesive layer. At this time, the surface of the protective film D and the surface of the adhesive C were subjected to corona treatment in advance. Next, the brightness improving film A was bonded to the surface of the pressure-sensitive adhesive C opposite to the surface to which the protective film D was bonded to prepare the back side polarizing plate 2. At this time, the surface of the brightness improving film A was subjected to corona treatment in advance. The pressure-sensitive adhesive A was bonded to the protective film C surface of the back-side polarizing plate 2 thus obtained to form a pressure-sensitive adhesive layer. Also at this time, the surface of the protective film C and the surface of the adhesive A were subjected to corona treatment in advance.

[Manufacturing Example 13] Preparation of Backside Polarizing Plate 3 The protective film D was subjected to a saponification treatment, and one surface of the protective film C was subjected to a corona treatment. The protective film D, the polarizing film 1, and the protective film C are bonded with an aqueous adhesive so that the triacetyl cellulose surface of the protective film D and the corona-treated surface of the protective film C are bonded surfaces to the polarizing film 1, respectively. , Drying treatment was carried out to obtain an absorbent polarizing plate. The dimensional change rate of the obtained absorption-type polarizing plate in the absorption axis direction was 0.91%. The dimensional change rate was adjusted by adjusting the drying time in the above drying treatment. Next, the pressure-sensitive adhesive A was bonded to the protective film D surface of the obtained absorbent polarizing plate to form a pressure-sensitive adhesive layer. At this time, the surface of the protective film D and the surface of the adhesive A were subjected to corona treatment in advance. Next, the brightness improving film A was bonded to the surface of the pressure-sensitive adhesive A opposite to the surface to which the protective film D was bonded to prepare the back side polarizing plate 3. At this time, the surface of the brightness improving film A was subjected to corona treatment in advance. The pressure-sensitive adhesive A was bonded to the protective film C surface of the back-side polarizing plate 3 thus obtained to form a pressure-sensitive adhesive layer. Also at this time, the surface of the protective film C and the surface of the adhesive A were subjected to corona treatment in advance.

[Liquid crystal cell]
Google Inc. A liquid crystal cell was obtained by peeling off the viewing side polarizing plate and the back side polarizing plate from the Nexus 7 liquid crystal panel manufactured by Nexus 7.

[Example 1]
The viewing side polarizing plate 1 is cut into a diagonal 7-inch size so that the absorption axis of the polarizing film is parallel to the long side of the liquid crystal cell, and the back side polarizing plate 1 is cut into a polarizing film with respect to the short side of the liquid crystal cell. The film was cut into a diagonal 7-inch size so that the absorption axes of the films were parallel to each other. The polarizing plates thus produced were attached to the liquid crystal cells via an adhesive to prepare a liquid crystal panel. The ratio of the dimensional change rate between the viewing side polarizing plate and the back surface side polarizing plate was 1.12. The distance from the brightness improving film to the liquid crystal cell was 85 μm.

The liquid crystal panel thus produced was allowed to stand in an environment of 85 ° C. for 240 hours, and then the amount of warpage was measured and found to be 0.4 mm.

[Examples 2 to 8 and Comparative Examples 1 to 2]
A liquid crystal panel was produced in the same manner as in Example 1 except that the viewing side polarizing plate and the back side polarizing plate shown in Table 1 were used, and the amount of warpage of the liquid crystal panel was measured.

Dimensional change rate of the viewing side polarizing plate used in Examples 1 to 8 and Comparative Examples 1 and 2 in the absorption axis direction, dimensional change rate of the absorption type polarizing plate included in the back side polarizing plate in the absorption axis direction, and back side polarization. Table 1 summarizes the distance from the brightness-improving film to the liquid crystal cell and the ratio of the dimensional change rate on the plate.

According to the present invention, it is possible to eliminate the warp of the liquid crystal panel in a high temperature environment, and it is possible to obtain a liquid crystal panel that fits in the housing of the final product in the high temperature environment, which is useful.

30 Visible side polarizing plate, 60 Back side polarizing plate 50 Absorption type polarizing plate 32, 52 Polarizing film 35 Surface treatment layer 31a, 31b, 51a, 51b Protective film 33, 53 Adhesive layer 54 Adhesive layer 61 Brightness improving film

Claims (5)

A liquid crystal panel including a liquid crystal cell and a set of polarizing plates.
The set of the polarizing plates is a set of a viewing-side polarizing plate arranged on the viewing side of the liquid crystal cell and a back-side polarizing plate arranged on the back side of the liquid crystal cell.
The absorption axis of the viewing side polarizing plate is substantially parallel to the long side direction of the liquid crystal cell, and the absorption axis of the back surface side polarizing plate is substantially parallel to the short side direction of the liquid crystal cell.
The viewing side polarizing plate is obtained by attaching a protective film to a polarizing film.
The protective film has an outer surface and
The back-side polarizing plate has a structure in which a brightness-improving film and an absorption-type polarizing plate are laminated via an adhesive layer, and when arranged on the back side of the liquid crystal cell, the surface of the back-side polarizing plate comes into contact with the liquid crystal cell. The distance to the brightness improving film is 100 μm or less,
The luminance improving film is a stretched film containing a layer having birefringence, and has a thickness of 15 μm or more and 30 μm or less.
The pressure-sensitive adhesive layer is formed of an acrylic pressure-sensitive adhesive and has a thickness of 3 μm or more and 25 μm or less.
The dimensional change rate in the absorption axis direction when the viewing side polarizing plate is heated at 85 ° C. for 100 hours, and the absorption axis direction when the absorption type polarizing plate contained in the back surface side polarizing plate is heated at 85 ° C. for 100 hours. A liquid crystal panel having a ratio of 0.62 or more and 1.25 or less with the dimensional change rate. The liquid crystal panel according to claim 1, wherein the absolute value of the amount of warpage when heated at 85 ° C. for 240 hours is 0.5 mm or less. The liquid crystal panel according to claim 1 or 2, wherein the protective film is provided with a surface treatment layer on the outer surface. The liquid crystal panel according to claim 3, wherein the surface treatment layer is a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer or an antifouling layer. The viewing-side polarizing plate and the back-side polarizing plate each have a polarizing film and have a polarizing film.
The liquid crystal panel according to any one of claims 1 to 4, wherein both the thickness of the polarizing film of the viewing-side polarizing plate and the thickness of the polarizing film of the back-side polarizing plate are 15 μm or less.

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