JP6887222B2 - Polarizing plate set - Google Patents

Description

The present invention relates to a polarizing plate set that can be used for various optical applications.

Polarizers are arranged on both sides of the liquid crystal cell due to the image forming method of the liquid crystal display device.
For example, Patent Document 1 discloses a liquid crystal panel in which polarizers are arranged on the front side and the back side of the liquid crystal cell. Further, Patent Document 2 discloses an optical laminate arranged on the front side and the back side of the liquid crystal cell.
According to the liquid crystal panel disclosed in Patent Document 1 and the optical laminate disclosed in Patent Document 2, the relationship between the thickness of the polarizing film arranged on the front side and the polarizing film arranged on the back side is defined. Attempts have been made to reduce the warpage of the liquid crystal panel.

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

In the past, only the warp in a high temperature environment was focused on, and if this was controlled, the warp of the liquid crystal panel did not become a problem, but as the thickness of the liquid crystal cell becomes thinner (for example, the glass constituting the liquid crystal cell). The warp of the liquid crystal cell can be remarkably confirmed by the stress of the polarizing plate caused by the slight amount of dimensional change generated in a moist heat environment (for example, 60 ° C., 90% humidity) in a substrate thickness of 0.5 mm or less). found.
In the inventions disclosed in Patent Documents 1 and 2, depending on the conditions such as the protective film used and the structure of the polarizing plate, the liquid crystal panel may be peeled off from the touch panel or the backlight unit may fall off due to the warp of the liquid crystal panel in a moist heat environment. There are problems such as doing.

Therefore, an object of the present invention is to provide a polarizing plate set capable of suppressing not only the warp of the liquid crystal panel in a high temperature environment but also the warp of the liquid crystal panel in a moist heat environment.

The present invention includes:
[1] A polarizing plate set including a back-side polarizing plate arranged on one surface side of a liquid crystal cell and a front-side polarizing plate arranged on the other surface side.
The back side polarizing plate has a reflective polarizing plate, a first pressure-sensitive adhesive layer, a first polarizing element, a first protective film, and a second pressure-sensitive adhesive layer.
The front-side polarizing plate has a third pressure-sensitive adhesive layer, a second polarizing element, and a second protective film.
The difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizer in the back side polarizing plate from the thickness dF (μm) of the second polarizer in the front side polarizing plate was defined as Δd (μm). In the case, 0 μm <Δd <5 μm,
The angle formed by the absorption axis of the second polarizer in the front-side polarizing plate and the absorption axis of the first polarizer in the back-side polarizing plate is 90 ° ± 1 °.
Polarizing plate set.
[2] The polarizing plate set according to [1], wherein the angle formed by the absorption axis of the first polarizing element in the back-side polarizing plate and the long side of the back-side polarizing plate is 0 ° ± 0.5 °.
[3] The polarizing plate set according to [1] or [2], wherein the reflective polarizing plate has at least two thin films, and the thin films having at least two layers have different refractive index anisotropy.
[4] It has a liquid crystal cell and a pair of polarizing plates arranged on both sides thereof.
The pair of polarizing plates is the polarizing plate set according to any one of [1] to [3].
A second protective film, a second polarizing element, a third pressure-sensitive adhesive layer, a liquid crystal cell, a second pressure-sensitive adhesive layer, a first protective film, a first-polarizer, a first pressure-sensitive adhesive layer, and reflection. A liquid crystal panel in which type polarizing plates are laminated in this order.

According to the present invention, it is possible to obtain a set of polarizing plates capable of reducing the warp of a liquid crystal panel when exposed to a moist heat environment and a high temperature environment.

It is the schematic sectional drawing explaining one aspect in the polarizing plate set of this invention. It is the schematic explaining the angle formed by the absorption axis of the front side polarizing plate and the absorption axis of the back side polarizing plate. It is a figure explaining the measurement of the amount of warpage.

Hereinafter, the polarizing plate set according to the present invention will be described with reference to appropriate figures, but the present invention is not limited to these aspects.

A polarizing plate set including a back-side polarizing plate arranged on one surface side of a liquid crystal cell and a front-side polarizing plate arranged on the other surface side.
The back side polarizing plate has a reflective polarizing plate, a first pressure-sensitive adhesive layer, a first polarizing element, a first protective film, and a second pressure-sensitive adhesive layer.
The front-side polarizing plate has a third pressure-sensitive adhesive layer, a second polarizing element, and a second protective film.
The difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizer in the back side polarizing plate from the thickness dF (μm) of the second polarizer in the front side polarizing plate was defined as Δd (μm). In the case, 0 μm <Δd <5 μm,
The angle formed by the absorption axis of the second polarizer in the front-side polarizing plate and the absorption axis of the first polarizer in the back-side polarizing plate is 90 ° ± 1 °.
It is a polarizing plate set.
For example, according to the liquid crystal panel provided with the set of polarizing plates of the present invention, it is possible to prevent the liquid crystal panel from peeling off from the touch panel or the backlight unit from falling off, and it is possible to obtain a display device having small display unevenness. it can.

As shown in FIG. 1, the polarizing plate set of the present invention includes a back-side polarizing plate 10 arranged on one surface side of the liquid crystal cell 30, and a front-side polarizing plate 20 arranged on the other surface side. .. The back side polarizing plate 10 has a reflective polarizing plate 11, a first pressure-sensitive adhesive layer 12, a first polarizer 13, a first protective film 14, and a second pressure-sensitive adhesive layer 15. In one aspect, the backside polarizing plate 10 may optionally have an additional layer.

In another embodiment, the back-side polarizing plate 10 includes a reflective polarizing plate 11, a first pressure-sensitive adhesive layer 12, a first polarizer 13, a first protective film 14, and a second pressure-sensitive adhesive layer 15. The polarizing plates are laminated in this order. Further, the back-side polarizing plate 10 may further have a protective film between the first pressure-sensitive adhesive layer 12 and the first polarizer 13 (not shown). That is, the back-side polarizing plate 10 may have protective films on both sides of the first polarizing element 13.

The front-side polarizing plate 20 has a third pressure-sensitive adhesive layer 21, a second polarizing element 22, and a second protective film 23. The front side polarizing plate 20 may have an additional layer, if desired.
In another embodiment, the front-side polarizing plate 20 is a polarizing plate in which a third pressure-sensitive adhesive layer 21, a second polarizing element 22, and a second protective film 23 are laminated in this order. Further, the front-side polarizing plate 20 may further have a protective film between the third pressure-sensitive adhesive layer 21 and the second polarizing element 22 (not shown). That is, the front side polarizing plate 20 may have protective films on both sides of the second polarizing element 22.

The back-side polarizing plate in the present invention is attached to, for example, a surface of the liquid crystal cell opposite to the surface on the visual side. In one aspect, the backside polarizing plate may be attached to the liquid crystal cell so as to be adjacent to a light source provided on the liquid crystal panel, such as a backlight. Further, a narrow double-sided tape may be attached to the edge of the back polarizing plate, and the backlight unit may be attached.
On the other hand, the front-side polarizing plate in the present invention is attached to, for example, the surface on the visual side of the liquid crystal cell.

Although not shown in FIG. 1, for example, the polarizing plate set shown in FIG. 1, that is, the back side polarizing plate 10 and the front side polarizing plate 20 may be provided with a layer other than the above-mentioned layer. Further, the polarizers 13 and 22 and the protective films 14 and 23 are usually bonded to each other via an adhesive layer.

In the polarizing plate set of the present invention, as shown in FIG. 1, the thickness of the second polarizing element on the front side polarizing plate 20 is dF, the thickness of the first polarizer on the back side polarizing plate 10 is dR, and the front surface is defined as dR. When the difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizing element of the back side polarizing plate 10 from the thickness dF (μm) of the second polarizing element of the side polarizing plate 20 is Δd (μm). ,
It has a relationship of 0 μm <Δd <5 μm, and more preferably 1 μm <Δd <5 μm.

When Δd (μm), which is the difference obtained by subtracting the thickness dR from the thickness dF, is in such a range, the laminated body (liquid crystal panel) of the front side polarizing plate, the glass (liquid crystal cell), and the back side polarizing plate can be formed. Even when exposed to a high temperature (for example, 85 ° C., humidity 5%) for a long time, the amount of warpage of the laminated body is small. Further, even if the laminated body of the front-side polarizing plate, the glass, and the back-side polarizing plate is placed under the condition of a moist heat environment (for example, 60 ° C., humidity 90%), the warp of the laminated body is suppressed.
As described above, since the laminate provided with the polarizing plate set of the present invention has a small amount of warpage when placed in a moist heat environment and a high temperature environment, it has moist heat resistance and heat resistance, and can be used from a touch panel in a high temperature environment and a high temperature environment. It is considered that the peeling of the light and the falling off of the backlight unit will not occur. In addition, it leads to reduction of display unevenness caused by warpage after the high temperature environment and moist heat environment test.
Further, since Δd (μm) has such a relationship, the polarizing plate set of the present invention can be applied to a liquid crystal panel having various sizes and thicknesses.
In the present specification, the high temperature environment is described as an example for a temperature of 85 ° C. In the present invention, the high temperature environment can mean an environment in which a polarizing plate or the like is exposed to, for example, a temperature of 70 ° C. to 95 ° C. and a humidity of 0% to 20% for at least 30 to 60 minutes.
Further, the moist heat environment will be described as an example under the conditions of a temperature of 60 ° C. and a humidity of 90%. In the present invention, the moist heat environment can mean an environment in which a polarizing plate or the like is exposed to, for example, a temperature of 50 ° C. to 80 ° C. and a humidity of 60% to 95% for at least 30 minutes to 60 minutes.

In one embodiment, the thickness dR of the first polarizing element of the back-side polarizing plate is 15 μm or less, more preferably 0.1 μm or more and 13 μm or less.
Since the back-side polarizing plate has a reflective polarizing plate, the thinner the thickness of the first polarizer, the thinner the back-side polarizing plate can be achieved.

The measurement of each thickness of the polarizing plate set in the present invention can be performed by using a measuring method known in the art.

In the present invention, the angle formed by the absorption axis of the second polarizer in the front polarizing plate and the absorption axis of the first polarizer in the back polarizing plate is 90 ° ± 1 °, more preferably 90 ° ± 0. It is in the range of .5 °.

For example, FIG. 2 is a diagram illustrating the relationship between the absorption axes of the polarizer in one aspect of the present invention. In FIG. 2, the absorption axis of the first polarizing element in the back-side polarizing plate 10 is represented by 10a, and the transmission axis of the first polarizing element is represented by 10b. The long side of the backside polarizing plate is indicated by 10c. On the other hand, in FIG. 2, the absorption axis of the second polarizing element of the front side polarizing plate 20 is represented by 20a, and the transmission axis of the second polarizing element is represented by 20b.
In the present invention, the angle formed by the absorption axis 10a of the first polarizer and the absorption axis 20a of the second polarizer is 90 ° ± 1 ° as described above. This angle can be expressed as, for example, the angle α in FIG.

In one embodiment, the angle formed by the absorption axis of the first polarizing element in the back side polarizing plate and the long side of the back side polarizing plate (first polarizing element) is 0 ° ± 1 °, and in another aspect. The angle formed above is 0 ° ± 0.5 °.

In the present invention, the absorption axis of the second polarizer in the front polarizing plate may be described as the absorption axis of the front polarizing plate, and the absorption axis of the first polarizing element in the back polarizing plate may be referred to as the absorption axis of the first polarizing element in the back polarizing plate. It may be the absorption axis of the back side polarizing plate.

In the polarizing plate set of the present invention, the difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizing element of the back side polarizing plate from the thickness dF (μm) of the second polarizer in the front side polarizing plate is obtained. When Δd (μm)
When 0 μm <Δd <5 μm, for example, even if a liquid crystal panel having a front-side polarizing plate, a glass plate, and a back-side polarizing plate is exposed to a moist heat environment under high temperature conditions, these warpages can be suppressed.

When the polarizing plate in the present invention is exposed to high temperature conditions and the polarizing plate may be slightly warped, for example, a reflective polarizing plate, a first pressure-sensitive adhesive layer, a first polarizing element, a first protective film and a second protective film are used. The pressure-sensitive adhesive layer can warp together. Similarly, the third pressure-sensitive adhesive layer, the second polarizer and the second protective film can warp together.
Therefore, the back-side polarizing plate and the front-side polarizing plate in the present invention cannot usually undergo delamination between at least one of these layers.
In addition, either the back side polarizing plate or the front side polarizing plate may be warped, and both the back side polarizing plate and the front side polarizing plate may be warped.

In the present invention, such warpage can be evaluated by measuring the amount of warpage and the like. For example, this amount of warpage may be evaluated by measuring the amount of warpage under moist heat conditions, or may be evaluated by measuring the amount of warpage under high temperature conditions.
For example, when measuring the amount of warpage under moist heat conditions, the third adhesive of the front polarizing plate and the second adhesive layer of the back polarizing plate are attached to the front and back of the glass panel, and the temperature is 60 ° C. and the humidity is 90%. After allowing to stand for 250 hours, the glass panel was installed so that the backside polarizing plate was on the bottom, and the relative height of the floating of the measuring table from the horizontal plane was measured.

For example, when measuring the amount of warpage in a high temperature state, the third adhesive of the front polarizing plate and the second adhesive layer of the back polarizing plate are attached to the front and back of the glass panel, and the temperature is 85 ° C. and the humidity is 5%. After allowing to stand for 250 hours, a glass panel was installed so that the back side polarizing plate was on the bottom, and the relative height of the floating of the measuring table from the horizontal plane was measured.

[Reflective polarizing plate]
The reflective polarizing plate is also called a brightness improving film, and a polarization conversion element having a function of separating the emitted light from a light source (backlight) into transmitted polarized light and reflected polarized light or scattered polarized light is used. As described above, by arranging the reflective polarizing plate and the polarizer in a predetermined relationship, the emission efficiency of the linearly polarized light emitted from the polarizer is improved by utilizing the retrolight which is the reflected polarized light or the scattered polarized light. be able to. For example, the reflective polarizing plate is laminated in contact with the first pressure-sensitive adhesive layer.

The reflective polarizing plate can be, for example, an anisotropic reflective polarizer. An example of an anisotropic reflective polarizer is an anisotropic multilayer thin film that transmits linearly polarized light in one vibration direction and reflects linearly polarized light in the other vibration direction, and a specific example thereof is DBEF manufactured by 3M. (Japanese Patent Laid-Open No. 4-268505, etc.). Such a reflective polarizing plate is a reflective polarizing plate formed by stretching a multilayer laminate composed of at least two thin films having different refractive index anisotropy. Therefore, such a reflective polarizing plate has at least two thin films, and the stretched at least two thin films have different refractive index anisotropy.

Another example of the anisotropic reflection polarizer is a complex of a cholesteric liquid crystal layer and a λ / 4 plate, and a specific example thereof is a PCF manufactured by Nitto Denko KK (Japanese Patent Laid-Open No. 11-231130, etc.). .. Yet another example of the anisotropic reflection polarizer is a reflection grid polarizer, a specific example of which is a metal lattice reflection polarizer (USA) in which a metal is finely processed to emit reflected polarized light even in the visible light region. Patent No. 6288840, etc.), a film obtained by adding fine metal particles into a polymer matrix and stretching it (Japanese Patent Laid-Open No. 8-184701).

An optical layer such as a hard coat layer, an antiglare layer, a light diffusion layer, and a retardation layer having a retardation value of 1/4 wavelength is provided on the surface of the reflective polarizing plate on the side opposite to the first pressure-sensitive adhesive layer. You may. By forming the optical layer, the adhesion to the backlight tape and the uniformity of the displayed image can be improved. The thickness of the reflective polarizing plate can be about 5 to 100 μm, but is preferably 10 to 40 μm, more preferably 10 to 30 μm from the viewpoint of reducing warpage of the liquid crystal panel.

In the polarizing plate set of the present invention, the surface of the reflective polarizing plate on the side of the first pressure-sensitive adhesive layer can be subjected to a surface activation treatment. This surface activation treatment is performed prior to the bonding of the reflective polarizing plate and the first pressure-sensitive adhesive layer. As a result, a polarizing plate having excellent moist heat durability can be obtained, in which peeling between the first pressure-sensitive adhesive layer and the reflective polarizing plate is unlikely to occur in a moist heat environment.

The surface activation treatment can be a surface hydrophilic treatment, and may be a dry treatment or a wet treatment. Examples of the dry treatment include discharge treatment such as corona treatment, plasma treatment, and glow discharge treatment; flame treatment; ozone treatment; UV ozone treatment; ultraviolet treatment, ionization active ray treatment such as electron beam treatment, and the like. Examples of the wet treatment include ultrasonic treatment using a solvent such as water and acetone, alkali treatment, and anchor coating treatment. These processes may be performed alone or in combination of two or more.

Above all, from the viewpoint of the effect of suppressing peeling of the reflective polarizing plate in a moist heat environment and the productivity of the polarizing plate, the surface activation treatment is preferably corona treatment and / or plasma treatment. According to these surface activation treatments, even when the thickness of the reflective polarizing plate is thin, for example, 30 μm or less, peeling between the first pressure-sensitive adhesive layer and the reflective polarizing plate in a moist heat environment can be prevented. It can be effectively suppressed. The surface of the first pressure-sensitive adhesive layer on the luminance-reflecting polarizing plate side may also be subjected to a surface activation treatment.

[First adhesive layer]
The first pressure-sensitive adhesive layer is a layer interposed between the first polarizing element and the reflective polarizing plate. The first pressure-sensitive adhesive layer is typically laminated directly on the polarizer so that the first polarizer and the first pressure-sensitive adhesive layer are in contact with each other. The first pressure-sensitive adhesive layer can be composed of a pressure-sensitive adhesive composition containing a resin as a main component, such as acrylic-based, rubber-based, urethane-based, ester-based, silicone-based, and polyvinyl ether-based. Among them, a pressure-sensitive adhesive composition using an acrylic resin having excellent transparency, weather resistance, heat resistance and the like as a base polymer is preferable. The pressure-sensitive adhesive composition may be an active energy ray-curable type or a thermosetting type.

Examples of the acrylic base polymer include (meth) acrylic acid ester-based polymers such as butyl (meth) acrylate, ethyl (meth) acrylate, isooctyl (meth) acrylate, and 2-ethylhexyl (meth) acrylate. Polymers and copolymer-based base polymers using two or more of these (meth) acrylic acid esters are preferably used. It is preferable that the base polymer is copolymerized with a polar monomer. Examples of the polar monomer include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, hydroxyethyl (meth) acrylate, (meth) acrylamide, N, N-dimethylaminoethyl (meth) acrylate, and glycidyl (). Examples thereof include monomers having a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group and the like, such as meta) acrylate.

The pressure-sensitive adhesive composition usually further contains a cross-linking agent. The cross-linking agent is a divalent or higher metal ion that forms a carboxylic acid metal salt with a carboxyl group; a polyamine compound that forms an amide bond with a carboxyl group; poly. Epoxy compounds and polyols that form an ester bond with a carboxyl group; polyisocyanate compounds that form an amide bond with a carboxyl group are exemplified. Of these, polyisocyanate compounds are preferable.

The active energy ray-curable pressure-sensitive adhesive composition has a property of being cured by being irradiated with active energy rays such as ultraviolet rays and electron beams, and has adhesiveness even before irradiation with active energy rays. It is a pressure-sensitive adhesive composition having the property of being able to adhere to an adherend such as, etc., and being cured by irradiation with active energy rays to adjust the adhesion force. The active energy ray-curable pressure-sensitive adhesive composition is preferably an ultraviolet-curable type. The active energy ray-curable pressure-sensitive adhesive composition further contains an active energy ray-polymerizable compound in addition to the base polymer and the cross-linking agent. Further, if necessary, a photopolymerization initiator, a photosensitizer, or the like may be contained.

The pressure-sensitive adhesive composition contains fine particles for imparting light scattering properties; beads; resins other than the base polymer; pressure-sensitive adhesives; fillers; antioxidants; ultraviolet absorbers; pigments; additives such as colorants. be able to.

The first pressure-sensitive adhesive layer can be formed by applying an organic solvent diluted solution of the above-mentioned pressure-sensitive adhesive composition on a substrate and drying it. The base material can be a polarizer, a reflective polarizing plate, a separator, or the like. When the active energy ray-curable pressure-sensitive adhesive composition is used, the formed pressure-sensitive adhesive layer can be irradiated with active energy rays to obtain a desired cured product.

The first pressure-sensitive adhesive layer preferably exhibits a storage elastic modulus of 0.15 to 1.2 MPa in a temperature range of 23 to 80 ° C. As a result, the durability of the polarizing plate can be improved by suppressing the dimensional change that tends to occur with the shrinkage of the polarizing element in a high temperature and moist heat environment. In addition, even when a liquid crystal panel equipped with a polarizing plate (for example, a liquid crystal panel for small and medium-sized mobile terminals) is placed in a high temperature and moist heat environment, the movement of the polarizing plate is suppressed, so that the reliability of the liquid crystal panel can be improved. Can be enhanced.

"Exhibiting a storage elastic modulus of 0.15 to 1.2 MPa in a temperature range of 23 to 80 ° C." means that the storage elastic modulus is a value within the above range at any temperature in this range. .. Since the storage elastic modulus usually gradually decreases as the temperature rises, if the storage elastic modulus at 23 ° C. and 80 ° C. is both within the above range, the storage elastic modulus within the above range is indicated at the temperature in this range. Can be seen as. The storage elastic modulus of the first pressure-sensitive adhesive layer can be measured using a commercially available viscoelasticity measuring device, for example, a viscoelasticity measuring device “DYNAMIC ANALYZER RDA II” manufactured by REOMETRIC as shown in the examples below. it can.

As a method for adjusting the storage elastic modulus within the above range, an oligomer, specifically, a urethane acrylate-based oligomer is further added to a pressure-sensitive adhesive composition containing a base polymer and a cross-linking agent to form an active energy ray-curable type. A pressure-sensitive adhesive composition (preferably an ultraviolet curable pressure-sensitive adhesive composition) may be used. More preferably, the pressure-sensitive adhesive layer is appropriately cured by irradiating it with active energy rays.

The thickness of the first pressure-sensitive adhesive layer can be 30 μm or less. It is preferably 25 μm or less, particularly preferably 20 μm or less, and particularly preferably 15 μm or less. When the thickness of the first pressure-sensitive adhesive layer is in such a range, it is possible to suppress a dimensional change of the polarizing plate while maintaining good processability. The thickness of the first pressure-sensitive adhesive layer can be appropriately adjusted so that the interlayer thickness is within a predetermined range.

[Polarizer]
A polarizer is an absorption-type polarized light having the property of absorbing linearly polarized light having a vibration plane parallel to its absorption axis and transmitting linearly polarized light having a vibration plane orthogonal to the absorption axis (parallel to the transmission axis). is there. The first and second polarizers used in the polarizing plate set of the present invention may be the same or different polarizers as long as their thicknesses have a predetermined relationship. .. For example, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film can be preferably used. The polarizer is, for example, 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; It can be produced by a method including a step of treating the alcohol-based resin film with an aqueous boric acid solution; and a step of washing with water after the treatment with the aqueous boric acid solution.

As the polyvinyl alcohol-based resin, a saponified polyvinyl acetate-based resin can be used. Examples of the polyvinyl acetate-based resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and another monomer copolymerizable with the 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-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 be used. The average degree of polymerization of the polyvinyl alcohol-based resin is usually about 1000 to 10000, preferably about 1500 to 5000. The average degree of polymerization of the polyvinyl alcohol-based resin can be determined in accordance with JIS K 6726.

A film formed of such a polyvinyl alcohol-based resin is used as a raw film for a polarizing element (polarizing film). The method for forming a film of the polyvinyl alcohol-based resin is not particularly limited, and a known method is adopted. The thickness of the polyvinyl alcohol-based raw film is not particularly limited, but in order to reduce the thickness of the polarizer to, for example, 15 μm or less, it is preferable to use a raw film having a thickness of about 5 to 35 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing the dichroic dye, at the same time as dyeing, or after dyeing. If the uniaxial stretching is performed after staining, the uniaxial stretching may be performed before the boric acid treatment or during the boric acid treatment. Moreover, uniaxial stretching may be performed in these a plurality of steps.

In uniaxial stretching, rolls having different peripheral speeds may be uniaxially stretched, or thermal rolls may be used to uniaxially stretch the rolls. The uniaxial stretching may be a dry stretching in which the film is stretched in the atmosphere, or a wet stretching in which the polyvinyl alcohol-based resin film is swollen with a solvent. The draw ratio is usually about 3 to 8 times.

As a method of dyeing a polyvinyl alcohol-based resin film with a dichroic dye, for example, a method of immersing the film in an aqueous solution containing a dichroic dye is adopted. As the dichroic dye, iodine or a dichroic organic dye is used. The polyvinyl alcohol-based resin film is preferably immersed in water before the dyeing treatment.

As the dyeing treatment with iodine, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually adopted. The iodine content in this aqueous solution can be about 0.01 to 1 part by weight per 100 parts by weight of water. The content of potassium iodide can be about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution can be about 20 to 40 ° C. On the other hand, as a dyeing treatment with a dichroic organic dye, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic organic dye is usually adopted. The aqueous solution containing the dichroic organic dye may contain an inorganic salt such as sodium sulfate as a dyeing aid. The content of the dichroic organic dye in this aqueous solution can be about ^{1 × 10 -4 to 10 parts by weight per 100 parts by weight of water.} The temperature of this aqueous solution can be about 20 to 80 ° C.

As the boric acid treatment after dyeing with a dichroic dye, a method of immersing the dyed polyvinyl alcohol-based resin film in a boric acid-containing aqueous solution is usually adopted. When iodine is used as the dichroic pigment, the boric acid-containing aqueous solution preferably contains potassium iodide. The amount of boric acid in the boric acid-containing aqueous solution can be about 2 to 15 parts by weight per 100 parts by weight of water. The amount of potassium iodide in this aqueous solution can be about 0.1 to 15 parts by weight per 100 parts by weight of water. The temperature of this aqueous solution can be 50 ° C. or higher, for example 50-85 ° 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 water washing treatment may be carried out with water containing potassium iodide. The temperature of the water in the water washing treatment is usually about 5 to 40 ° C.

After washing with water, it is dried to obtain a polarizer. The drying process can be performed using a hot air dryer or a far-infrared heater. The thickness of the polarizer is preferably 15 μm or less, more preferably 13 μm or less. The thickness of the polarizer is usually 4 μm or more. In one aspect, the thickness dR of the first polarizer in the back side polarizing plate is 15 μm or less. In one aspect, the thickness dF of the second polarizing element in the front polarizing plate is 15 μm or less, more preferably 0.1 μm or more and 13 μm or less.
The thickness of the polarizer can be appropriately adjusted so as not to deviate from the scope of the present invention.

[Protective film]
The first protective film is a film laminated on the surface of the first polarizing element opposite to the first pressure-sensitive adhesive layer. The second protective film is a film laminated on the surface of the second polarizing element opposite to the third pressure-sensitive adhesive layer. The first protective film and the second protective film may be the same film or different films.
The protective film is a translucent (preferably optically transparent) thermoplastic resin, for example, a polyolefin such as a chain polyolefin resin (polypropylene resin or the like) or a cyclic polyolefin resin (norbornen resin or the like). Resins; Cellulosic resins such as triacetyl cellulose and diacetyl cellulose; Polyester resins such as polyethylene terephthalate and polybutylene terephthalate; Polycarbonate resins; Acrylic resins such as (meth) acrylic resins; Polystyrene resins; Polyvinyl chloride resin; Acrylonitrile / butadiene / styrene resin; Acrylonitrile / styrene resin; Polyvinyl acetate resin; Polyvinylidene chloride resin; Polyamide resin; Polyacetal resin; Modified polyphenylene ether resin; Polysulfone resin; A film made of a polyether sulfone-based resin; a polyarylate-based resin; a polyamide-based resin; a polyimide-based resin, or the like can be used. Of these, it is preferable to use a polyolefin-based resin or an acrylic-based resin, and particularly preferably a cyclic polyolefin-based resin.

Examples of the chain polyolefin resin include homopolymers of chain olefins such as polyethylene resin and polypropylene resin, and copolymers composed of two or more kinds of chain olefins.

Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin resin include an open (co) polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a copolymer of a cyclic olefin and a chain olefin such as ethylene and propylene (typically). Is a random copolymer), a graft polymer obtained by modifying these with an unsaturated carboxylic acid or a derivative thereof, and a hydride thereof. Of these, a norbornene-based resin using a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer is preferably used as the cyclic olefin. In a preferred embodiment, the protective film according to the present invention contains a cyclic polyolefin resin.

The cellulosic resin is obtained by substituting a part or all of hydrogen atoms in the hydroxyl groups of cellulose obtained from raw material cellulose such as cotton linter and wood pulp (perforated tree pulp, coniferous tree pulp) with acetyl group, propionyl group and / or butyryl group. Also, it refers to a cellulose organic acid ester or a cellulose mixed organic acid ester. For example, those composed of acetic acid ester of cellulose, propionic acid ester, butyric acid ester, mixed ester thereof and the like can be mentioned.

A preferable specific example of the acrylic resin film is a film containing a methyl methacrylate resin. The methyl methacrylate-based resin is a polymer containing 50% by weight or more of methyl methacrylate units. The content of the methyl methacrylate unit is preferably 70% by weight or more, and may be 100% by weight. The polymer having 100% by weight of methyl methacrylate is a methyl methacrylate homopolymer obtained by polymerizing methyl methacrylate alone.

In this methyl methacrylate-based resin, a monofunctional monomer containing methyl methacrylate as a main component and a polyfunctional monomer used as needed are usually used as a radical polymerization initiator and, if necessary. It can be obtained by polymerizing in the presence of a chain transfer agent.

Monofunctional monomers capable of copolymerizing with methyl methacrylate include, for example, ethyl methacrylate, butyl methacrylate, cyclohexyl methacrylate, phenyl methacrylate, benzyl methacrylate, 2-ethylhexyl methacrylate, and 2-hydroxy methacrylate. Methacrylic acid esters other than methyl methacrylate such as ethyl; methyl acrylate, ethyl acrylate, butyl acrylate, cyclohexyl acrylate, phenyl acrylate, benzyl acrylate, 2-ethylhexyl acrylate, and 2-hydroxyethyl acrylate. Acrylic acid esters such as; methyl 2- (hydroxymethyl) acrylate, methyl 3- (hydroxyethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, and hydroxy such as butyl 2- (hydroxymethyl) acrylate. Acrylic acid esters; unsaturated acids such as methacrylic acid and acrylic acid; halogenated styrenes such as chlorostyrene and bromostyrene; substituted styrenes such as vinyltoluene and α-methylstyrene; unsaturateds such as acrylonitrile and methacrylic nitrile Examples thereof include nitriles; unsaturated acid anhydrides such as maleic anhydride and citraconic anhydride; and unsaturated imides such as phenylmaleimide and cyclohexylmaleimide. Such monomers may be used alone or in combination of two or more.

Examples of the polyfunctional monomer copolymerizable with methyl methacrylate include ethylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, and tetraethylene glycol di (meth) acrylate. , Nonaethylene glycol di (meth) acrylate, and tetradecaethylene glycol (meth) acrylate and other ethylene glycols or oligomers thereof esterified with acrylic acid or methacrylic acid; both ends of propylene glycol or oligomers thereof. The hydroxyl group is esterified with acrylic acid or methacrylic acid; the hydroxyl group of a dihydric alcohol such as neopentyl glycol di (meth) acrylate, hexanediol di (meth) acrylate, and butanediol di (meth) acrylate is acrylic acid or methacrylic. Acid esterified; Bisphenol A, alkylene oxide adduct of Bisphenol A, or esterified hydroxyl groups at both ends of these halogen substituents with acrylic acid or methacrylic acid; Multivalent such as trimethylpropane and pentaerythritol Alcohol esterified with acrylic acid or methacrylic acid, and those having an epoxy group of glycidyl acrylate or glycidyl methacrylate added to these terminal hydroxyl groups by ring opening; succinic acid, adipic acid, terephthalic acid, phthalic acid, halogen substitutions thereof. Examples thereof include dibasic acids such as those obtained by ring-opening addition of an epoxy group of glycidyl acrylate or glycidyl methacrylate to dibasic acids such as these alkylene oxide adducts; aryl (meth) acrylates; and diaryl compounds such as divinylbenzene. Of these, ethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate and neopentyl glycol dimethacrylate are preferably used.

The methyl methacrylate-based resin may be a modified methyl methacrylate-based resin modified by carrying out a reaction between the functional groups of the resin. The reactions include, for example, a demethanol condensation reaction in a polymer chain between a methyl ester group of methyl acrylate and a hydroxyl group of methyl 2- (hydroxymethyl) acrylate, and a carboxyl group of acrylic acid and 2- (hydroxymethyl). ) Intrapolymer chain dehydration condensation reaction with the hydroxyl group of methyl acrylate and the like can be mentioned.

It is also useful to control the phase difference value of the protective film to a value suitable for the liquid crystal panel. For example, it is preferable to use a film having a substantially zero phase difference value for the liquid crystal panel in the in-plane switching (IPS) mode. When the phase difference value is substantially zero, the in-plane retardation value at a wavelength of 590 nm is 10 nm or less, the absolute value of the thickness direction retardation value at a wavelength of 590 nm is 10 nm or less, and the thickness direction position at a wavelength of 480 to 750 nm. It means that the absolute value of the phase difference value is 15 nm or less.

Depending on the mode of the liquid crystal panel, the protective film may be stretched and / or shrunk to give a suitable retardation value.

The thickness of the protective film can be about 1 to 30 μm, but is preferably 5 to 25 μm, more preferably 5 to 20 μm from the viewpoint of strength, handleability, and the like. If the thickness is within this range, the polarizer can be mechanically protected, the polarizer does not shrink even when exposed to a moist heat environment, and stable optical characteristics can be maintained. The thickness of the protective film can be appropriately adjusted so that the interlayer thickness is within a predetermined range.

The protective film can be attached to the polarizer via an adhesive layer. As the adhesive forming the adhesive layer, a water-based adhesive or an active energy ray-curable adhesive can be used.

Examples of the water-based adhesive include an adhesive composed of a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. Of these, a water-based adhesive composed of an aqueous solution of a polyvinyl alcohol-based resin is preferably used. Examples of the polyvinyl alcohol-based resin include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, and co-polymers of vinyl acetate and other monomers copolymerizable therewith. A polyvinyl alcohol-based copolymer obtained by saponifying the polymer, or a modified polyvinyl alcohol-based polymer in which the hydroxyl groups thereof are partially modified can be used. The water-based adhesive may contain a cross-linking agent such as an aldehyde compound, an epoxy compound, a melamine compound, a methylol compound, an isocyanate compound, an amine compound, and a polyvalent metal salt.

When a water-based adhesive is used, it is preferable to carry out a step of adhering the polarizer and the protective film and then drying the water-based adhesive in order to remove water contained in the water-based adhesive. After the drying step, a curing step of curing at a temperature of, for example, about 20 to 45 ° C. may be provided.

The active energy ray-curable adhesive refers to an adhesive that cures by irradiating with active energy rays such as ultraviolet rays, and includes, for example, a polymerizable compound and a photopolymerization initiator, and a photoreactive resin. Examples thereof include those containing a binder resin and a photoreactive cross-linking agent. Examples of the polymerizable compound include a photopolymerizable monomer such as a photocurable epoxy monomer, a photocurable acrylic monomer, and a photocurable urethane monomer, and an oligomer derived from the photopolymerizable monomer. Examples of the photopolymerization initiator include substances that generate active species such as neutral radicals, anion radicals, and cationic radicals when irradiated with active energy rays such as ultraviolet rays. As the active energy ray-curable adhesive containing a polymerizable compound and a photopolymerization initiator, those containing a photocurable epoxy monomer and a photocationic polymerization initiator can be preferably used.

When an active energy ray-curable adhesive is used, the active energy ray-curable adhesive is obtained by adhering the polarizer and the protective film, performing a drying step as necessary, and then irradiating the active energy ray. Perform a curing step to cure. The light source of the active energy ray is not particularly limited, but ultraviolet rays having an emission distribution having a wavelength of 400 nm or less are preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a chemical lamp, a black light lamp, and a micro lamp. A wave-excited mercury lamp, a metal halide lamp, or the like can be used.

When the polarizer and the protective film are bonded, saponification treatment, corona treatment, plasma treatment, or the like can be applied to at least one of these bonding surfaces.

[Second and third adhesive layers]
As the pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer, conventionally known pressure-sensitive adhesives may be appropriately selected, and an environment in which the polarizing plate is exposed, a moist heat environment, or an environment in which high temperature and low temperature are repeated. Underneath, it suffices as long as it has adhesiveness to the extent that peeling does not occur. Specific examples thereof include an acrylic pressure-sensitive adhesive, a silicone-based pressure-sensitive adhesive, and a rubber-based pressure-sensitive adhesive, and the acrylic-based pressure-sensitive adhesive is particularly preferable in terms of transparency, weather resistance, heat resistance, and processability.
Further, the first pressure-sensitive adhesive layer, the second pressure-sensitive adhesive layer and / or the third pressure-sensitive adhesive layer may use the same type of pressure-sensitive adhesive, or may use different types of pressure-sensitive adhesive.
In a preferred embodiment, the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer are formed from an acrylic pressure-sensitive adhesive.

Adhesives include fillers, pigments, colorants, fillers, antioxidants, UV absorbers consisting of tackifiers, plasticizers, glass fibers, glass beads, metal powders, other inorganic powders, etc., as required. , Antistatic agent, silane coupling agent, and various other additives may be appropriately blended.

The pressure-sensitive adhesive layer is usually formed by applying a pressure-sensitive adhesive solution on a release sheet and drying the pressure-sensitive adhesive solution. For coating on the release sheet, for example, a roll coating method such as reverse coating or gravure coating, a spin coating method, a screen coating method, a fountain coating method, a dipping method, a spray method or the like can be adopted. The release sheet provided with the pressure-sensitive adhesive layer is used by a method of transferring the release sheet or the like. The thickness of the pressure-sensitive adhesive layer is usually about 3 to 30 μm, preferably 10 to 30 μm, and more preferably 10 to 25 μm. In a preferred embodiment, the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer have such a thickness, so that the polarizing plate can be prevented from being broken, and when incorporated into a liquid crystal display device, the edge portion of the liquid crystal panel is covered. It is possible to suppress the occurrence of light leakage. The thickness of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer can be appropriately adjusted so that the interlayer thickness is within a predetermined range.

The storage elastic modulus of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer at 80 ° C. is preferably 0.025 MPa or more, more preferably 0.07 MPa or more. If the storage elastic modulus of the pressure-sensitive adhesive layer is less than 0.025 MPa, cohesive failure of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer may occur. However, when incorporated into a liquid crystal display device, light leakage occurs at the edge of the liquid crystal panel, which adversely affects the display. Preferably, the storage elastic modulus of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer at 80 ° C. is 1.1 MPa or less, preferably 0.9 MPa or less. When the storage elastic modulus of the pressure-sensitive adhesive layer at 80 ° C. exceeds 1.1 MPa, the heat resistance and durability of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer and the glass or panel deteriorates, and bubbles are generated between the layers. It will be easier.

A separator may be provided to protect the surface of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer until they are bonded to another member. For example, a film made of a transparent resin such as polyethylene terephthalate, which has been treated with a mold release agent such as silicone, is used.

[Manufacturing method of backside polarizing plate]
The back-side polarizing plate of the present invention is, for example, a step of subjecting the surface of the first pressure-sensitive adhesive layer side of the reflective polarizing plate to a surface activation treatment, and a first surface on the surface of the surface activation treatment. It is produced through the process of laminating the pressure-sensitive adhesive layer.

Further, in the back-side polarizing plate of the present invention, for example, a first protective film is attached to one side of the polarizing element via an adhesive layer, and the surface of the first protective film opposite to the first polarizing element. The second pressure-sensitive adhesive layer is laminated on the surface, the first pressure-sensitive adhesive layer is bonded to the surface of the first polarizer on the side opposite to the first protective film, and the first polarizer in the first pressure-sensitive adhesive layer is bonded. Includes laminating a reflective polarizing plate on the opposite surface. By going through these steps, the backside polarizing plate of the present invention can be obtained. A separator may be temporarily attached to the outer surface of the second pressure-sensitive adhesive layer, or a surface activation treatment may be applied to the surface of the first pressure-sensitive adhesive layer to be bonded to the reflective polarizing plate.

The method of bonding the reflective polarizing plate to the first pressure-sensitive adhesive layer may be a single-wafer bonding method, or a sheet-roll composite bonding method as described in Japanese Patent Application Laid-Open No. 2004-262701. May be good. In addition, when it is possible to produce a long product and the required quantity is large, a roll-to-roll bonding method is also useful.

As described above, the method for producing the back side polarizing plate of the present invention can be produced by a method known in the art.

[Manufacturing method of front side polarizing plate]
The method for producing a back-side polarizing plate of the present invention can be produced by a method known in the art. For example, the front side polarizing plate can be obtained through the same steps as the above-described method for manufacturing the back side polarizing plate.

[LCD panel]
The polarizing plate set according to the present invention can be preferably applied to a liquid crystal panel. The liquid crystal panel includes a liquid crystal cell and a polarizing plate according to the present invention attached to the surface thereof. The back side polarizing plate can be attached to the liquid crystal cell via the second pressure-sensitive adhesive layer. The back-side polarizing plate according to the present invention is usually used as a polarizing plate arranged on the backlight side of the liquid crystal cell.
On the other hand, the front side polarizing plate can be attached to the liquid crystal cell via the third pressure-sensitive adhesive layer. The front-side polarizing plate according to the present invention is usually used as a polarizing plate arranged on the visual side of the liquid crystal cell.

In one aspect, it has a liquid crystal cell and a pair of polarizing plates arranged on both sides thereof.
The pair of polarizing plates is the above-mentioned polarizing plate set.
A second protective film, a second polarizing element, a third pressure-sensitive adhesive layer, a liquid crystal cell, a second pressure-sensitive adhesive layer, a first protective film, a first-polarizer, a first pressure-sensitive adhesive layer, and reflection. A liquid crystal panel in which type polarizing plates are laminated in this order is provided.

The driving method of the liquid crystal cell may be any conventionally known method, but the IPS mode is preferable. The liquid crystal panel using the polarizing plate according to the present invention has excellent wet and heat durability.

According to the present invention, an organic electroluminescence display device can be obtained by laminating each polarizing plate to an organic electroluminescence display via a second pressure-sensitive adhesive layer and a third pressure-sensitive adhesive layer.

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,% and parts representing the content or the amount used are based on weight unless otherwise specified.

The thickness of the film was measured according to the following.

(1) Measurement of film thickness The film was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

[Preparation of polarizer]
(Manufacturing Example P1)
A 60 μm-thick polyvinyl alcohol film (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) was stretched about 5 times vertically and uniaxially by dry stretching, and pure water at 60 ° C. was further maintained in a tense state. Was immersed in an aqueous solution at 28 ° C. having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 for 60 seconds. Then, it was immersed in an aqueous solution at 72 ° C. having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 for 300 seconds. Subsequently, the mixture 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. In the following, this polarizer may be referred to as a polarizer (23 μm).

(Manufacturing example P2)
A 30 μm-thick polyvinyl alcohol film (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) was stretched about 5 times in the longitudinal uniaxial manner by dry stretching, and pure water at 60 ° C. was further maintained in a tense state. Was immersed in an aqueous solution at 28 ° C. having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 for 60 seconds. Then, it was immersed in an aqueous solution at 72 ° C. having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 for 300 seconds. Subsequently, the mixture 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 12 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film. In the following, this polarizer may be referred to as a polarizer (12 μm).

(Manufacturing Example P3)
It was produced by the same method except that the draw ratio of Production Example P2 was adjusted, and a polarizer having a thickness of 11 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film was obtained. In the following, this polarizer may be referred to as a polarizer (11 μm).

(Manufacturing Example P4)
A 20 μm-thick polyvinyl alcohol film (average degree of polymerization of about 2,400, saponification degree of 99.9 mol% or more) was uniaxially stretched about 5 times by dry stretching, and further uniaxially stretched at 60 ° C. while maintaining a tense state. After immersing in pure water 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. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the mixture was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizer having a thickness of 7 μm in which iodine was adsorbed and oriented on a polyvinyl alcohol film. In the following, this polarizer may be referred to as a polarizer (7 μm).

(Manufacturing Example P5)
It was produced by the same method except that the draw ratio of Production Example P4 was adjusted, and a polarizer having a thickness of 8 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film was obtained. In the following, this polarizer may be referred to as a polarizer (8 μm).

[Example of Preparation of First Adhesive Layer]
A mold release treatment of a 38 μm-thick polyethylene terephthalate film (release film) in which an organic solvent solution obtained by adding a urethane acrylate oligomer and an isocyanate-based cross-linking agent to a copolymer of butyl acrylate and acrylic acid is subjected to a mold release treatment. The surface was coated with a die coater so that the thickness after drying was 5 μm, and an adhesive sheet obtained by drying was obtained.

[Preparation Example of Second Adhesive Layer and Third Adhesive Layer]
A commercially available pressure-sensitive adhesive sheet in which an acrylic pressure-sensitive adhesive layer having a thickness of 20 μm is provided on the mold-release-treated surface of a polyethylene terephthalate film (release film) having a thickness of 38 μm. Urethane acrylate oligomer is not blended.

[Reflective polarizing plate]
As the reflective polarizing plate-1, "Advanced Polarizer Film, Version 3" (thickness 26 μm) manufactured by 3M Co., Ltd. was used.

[Protective film]
The following protective film was used.
HC-TAC: A triacetyl cellulose film having a thickness of 32 μm and having a hard-coated surface (Toppan TOMOEGAWA Optical Film Co., Ltd., 25 KCHC-TC),

TAC: Triacetyl cellulose film (TAC) with a thickness of 25 μm [Product name “KC2UA” manufactured by Konica Minolta Co., Ltd.]

COP-1: A 23 μm-thick norbornene-based resin film that has not been stretched [trade name “ZEONOR” manufactured by Zeon Corporation]

COP-2: Unstretched 13 μm thick norbornene resin film [Product name “ZEONOR” manufactured by Zeon Corporation]

"Preparation of water-based adhesive"
An aqueous polyvinyl alcohol solution was prepared by dissolving 3 parts by weight of carboxyl group-modified polyvinyl alcohol [“KL-318” manufactured by Kuraray Co., Ltd.] in 100 parts by weight of water. To the obtained aqueous solution, add a water-soluble polyamide epoxy resin [“Sumirace Resin 650 (30)” manufactured by Taoka Chemical Industry Co., Ltd., solid content concentration 30% by weight] to 1.5 parts by weight with respect to 100 parts by weight of water. Mixing in proportions gave an aqueous adhesive.

[Example of Fabrication of Front Polarizing Plate]
(Example of Fabrication of Front Polarizing Plate A)
A water-based adhesive is applied to one side of the polarizer (12 μm), HC-TAC is attached as a second protective film, and COP-1 is laminated on the other side using the above-mentioned adhesive at 80 ° C. The protective film and the polarizer were adhered to each other by drying for 5 minutes. After bonding, it was cured at 40 ° C. for 168 hours. Further, a third pressure-sensitive adhesive layer was bonded to the surface of COP-1 opposite to the polarizer. This laminated body was designated as the front side polarizing plate A. The laminated body has a rectangular shape with a long side length of 155.25 mm and a short side length of 95.90 mm.

(Example of Fabrication of Front Polarizing Plate B)
It was produced in the same manner as the front side polarizing plate A except that the polarizer of the front side polarizing plate A was changed to a polarizer (11 μm). This laminated body was designated as the front side polarizing plate B.

(Example of Fabrication of Front Polarizing Plate C)
It was produced in the same manner as the front side polarizing plate A except that the polarizer of the front side polarizing plate A was changed to a polarizer (23 μm). This laminated body was designated as the front side polarizing plate C.

[Example of manufacturing a backside polarizing plate]
(Example of Fabrication of Polarizing Plate A on the Back Side)
A water-based adhesive is applied to one side of the polarizer (11 μm), TAC is attached as a protective film, and COP-2 is laminated as a first protective film on the other side using the above-mentioned adhesive. The protective film and the polarizer were bonded by drying at ° C. for 5 minutes. After bonding, it was cured at 40 ° C. for 168 hours. Further, a second pressure-sensitive adhesive layer was bonded to the surface of COP-2 opposite to the polarizer. Further, a reflective polarizing plate was attached to the surface of the TAC opposite to the polarizer via the first pressure-sensitive adhesive. This laminated body was designated as the back side polarizing plate A. The laminated body has a rectangular shape with a long side length of 155.25 mm and a short side length of 95.90 mm.

(Example of Fabrication of Backside Polarizing Plate B)
A water-based adhesive was applied to one side of the polarizer (8 μm), COP-2 was laminated as the first protective film, and the film was dried at 80 ° C. for 5 minutes to bond the protective film and the polarizer. Further, a second pressure-sensitive adhesive layer was bonded to the surface of COP-2 opposite to the polarizer. Further, a reflective polarizing plate was attached to the surface of the polarizer on the opposite side of the first protective film via the first adhesive. This laminated body was designated as the back side polarizing plate B. The laminated body has a rectangular shape with a long side length of 155.25 mm and a short side length of 95.90 mm.

(Example of Fabrication of Backside Polarizing Plate C)
It was produced in the same manner as the back side polarizing plate B except that the polarizer of the back side polarizing plate B was changed to a polarizer (7 μm). This laminated body was designated as the front side polarizing plate C.

(Example of Fabrication of Backside Polarizing Plate D)
It was produced in the same manner as the back side polarizing plate A except that the polarizer of the back side polarizing plate A was changed to a polarizer (12 μm). This laminated body was designated as the front side polarizing plate D.

Table 1 shows the configurations of the polarizing plates obtained in this manner in Examples and Comparative Examples. In addition, the physical properties of each of the obtained polarizing plates were evaluated according to the following description. The results are shown in Table 1.

[Measurement of warpage amount]
(Preparation of laminate)
The amount of warpage of the polarizing plate produced above was measured by the following method. First, in the produced back-side polarizing plate, the surface of the second pressure-sensitive adhesive layer opposite to the first protective film is attached to ^{a glass having a thickness of 0.4 mm (manufactured by Corning Inc., product number: EAGLE XG (registered trademark)).} Matched.
Next, the surface of the front side polarizing plate on the third pressure-sensitive adhesive layer opposite to the second polarizer was attached to the surface of the glass opposite to the second pressure-sensitive adhesive layer side.
The first polarizing plate on the back side polarizing plate is attached so that the absorption axis of the second polarizing element on the front side polarizing plate and the absorption axis of the first polarizer on the back side polarizing plate are formed at an angle of 90 °. A laminate was prepared so that the angle between the absorption axis of the polarizer and the long side of the backside polarizing plate was 0 °.

(Warp in a moist heat environment)
The laminate having the composition of the back side polarizing plate / glass / front side polarizing plate was allowed to stand for 250 hours in an environment of 60 ° C. and 90% humidity. The laminate was taken out from the test tank and placed on a measuring table of a two-dimensional measuring instrument (NEXIV (registered trademark) MR-12072 manufactured by Nikon Corporation) so that the front polarizing plate was on the upper side.
Next, the surface of the measuring table was focused, and the height from the reference focal point was measured by focusing on 25 points on the glass sample surface with reference to the surface. The difference between the maximum value and the minimum value of the height at 25 measurement points was defined as the amount of warpage. Specifically, the point 40 shown in FIG. 3 was used as the measurement point. The 25 points shown in FIG. 3 are points in a region 7 mm inside from the end of the polarizing plate, and are provided at intervals of about 20 mm in the short side direction and at intervals of about 35 mm in the long side direction. Further, in FIG. 3, reference numeral 50 indicates a polarizing plate, and 60 indicates a glass plate.
The judgment was as follows. The results are shown in Table 1.
In the examples, no floating or peeling of the entire laminate, or floating or peeling between the layers was observed in any of the samples.
<Judgment>
The case where the amount of warpage of the glass sample left to stand in a moist heat environment was less than 0.6 mm was evaluated as “◯”.
The case where the amount of warpage of the glass sample left to stand in a moist heat environment was 0.6 mm or more was defined as “x”.

(Warp in high temperature environment)
In the laminate having the configuration of the back side polarizing plate / glass / front side polarizing plate, the laminate was allowed to stand for 250 hours in an environment of 85 ° C. and 5% humidity so that the front side polarizing plate was on the upper side. .. Take out the laminate from the test tank, and place the warped laminate on the measuring table of a two-dimensional measuring instrument (NEXIV® MR-12072, manufactured by Nikon Corporation) so that the front polarizing plate is on the upper side. placed. The amount of warpage was measured in the same manner as described above.
<Judgment>
The case where the amount of warpage of the glass sample left to stand in a high temperature environment was 0.6 mm or less was evaluated as “◯”.
The case where the amount of warpage of the glass sample left to stand in a high temperature environment exceeds 0.6 mm was defined as “x”.

From these results, in the polarizing plate set of the present invention, the warp of the liquid crystal panel is suppressed even when the polarizing plate is exposed to a moist heat environment under high temperature conditions. Further, the cohesive failure of the second pressure-sensitive adhesive layer and the third pressure-sensitive adhesive layer can be suppressed. Further, the polarizing plate of the present invention has extremely good visibility even when exposed to a moist heat environment under high temperature conditions, and light leakage of the polarizing plate does not occur.
As described above, since the polarizing plate set of the present invention has a small amount of warpage when placed in a moist heat environment and a high temperature environment, it is possible to reduce or avoid peeling from the touch panel and falling off of the backlight unit. In addition, it leads to reduction of display unevenness caused by warpage that may occur when exposed to a high temperature environment and a moist heat environment.

According to the present invention, there is provided a polarizing plate set in which warpage caused by shrinkage of, for example, a polarizer and a reflective polarizing plate is suppressed. Further, according to the present invention, there is provided a polarizing plate set in which the cohesive failure of the pressure-sensitive adhesive layer bonded to the glass substrate of the liquid crystal cell is also suppressed.

10 Back side polarizing plate 11 Reflective type polarizing plate 12 1st pressure-sensitive adhesive layer 13 1st polarizing element 14 1st protective film 15 2nd pressure-sensitive adhesive layer 20 Front-side polarizing plate 21 3rd pressure-sensitive adhesive layer 22 2nd polarizing element 23 2 Protective film 30 Liquid crystal cell 40 Measurement point 50 Polarizing plate 60 Glass plate

Claims (8)

A polarizing plate set including a back-side polarizing plate arranged on one surface side of a liquid crystal cell and a front-side polarizing plate arranged on the other surface side.
In the back side polarizing plate, a reflective polarizing plate, a first pressure-sensitive adhesive layer, a first polarizer, a first protective film, and a second pressure-sensitive adhesive layer are laminated in this order, and the second It is affixed to the liquid crystal cell via an adhesive layer and
In the front side polarizing plate, a third pressure-sensitive adhesive layer, a second polarizing element, and a second protective film are laminated in this order, and are bonded to the liquid crystal cell via the third pressure-sensitive adhesive layer. ,
The first polarizing element and the second polarizing element are polarizing films in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film and uniaxially stretched at a stretching magnification of 3 to 8 times.
The difference dF-dR obtained by subtracting the thickness dR (μm) of the first polarizer in the back side polarizing plate from the thickness dF (μm) of the second polarizer in the front side polarizing plate was defined as Δd (μm). In this case, dF is 15 μm or less, dR is 15 μm or less, and Δd is 1 μm or more and 4 μm or less.
The angle formed by the absorption axis of the second polarizer in the front-side polarizing plate and the absorption axis of the first polarizer in the back-side polarizing plate is 90 ° ± 1 °.
The front-side polarizing plate further has a protective film between the third pressure-sensitive adhesive layer and the second polarizing element.
The first protective film, the second protective film, and the protective film held between the third pressure-sensitive adhesive layer and the second polarizing element are films made of a polyolefin resin or a cellulosic resin.
The protective film provided between the first protective film and the third pressure-sensitive adhesive layer and the second polarizing element has a thickness of 5 μm to 30 μm.
The second protective film has a thickness of 5 μm to 32 μm and has a thickness of 5 μm to 32 μm.
The reflective polarizing plate has a thickness of 10 to 30 μm and has a thickness of 10 to 30 μm.
The thickness of the first pressure-sensitive adhesive layer is 15 μm or less, and the thickness is 15 μm or less.
The thickness of the second pressure-sensitive adhesive layer is 10 to 25 μm.
The thickness of the third pressure-sensitive adhesive layer is 10 to 25 μm.
The front side polarizing plate has a rectangular shape and has a rectangular shape.
The back side polarizing plate has a rectangular shape and has a rectangular shape.
In the rear-side polarizing plate, the absorption axis of the first polarizer, the angle formed between the long sides of the back side polarizing plate Ri 0 ° ± 1 ° der,
When a laminate was prepared using the back side polarizing plate and the front side polarizing plate according to the following and the amount of warpage in a moist heat environment and the amount of warpage in a high temperature environment were measured, the amount of warpage in the moist heat environment. and warpage are both Ru der less than 0.6mm in the high temperature environment,
Polarizing plate set.
Preparation of Laminate: The back side polarizing plate and the front side polarizing plate have a rectangular shape having a long side length of 155.25 mm and a short side length of 95.90 mm, respectively. In the back-side polarizing plate, the angle formed by the absorption axis of the first polarizing element and the long side of the back-side polarizing plate is set to 0 °, and the side of the second pressure-sensitive adhesive layer opposite to the first protective film. The surface is attached to a glass having a thickness of 0.4 mm, and then the surface of the front-side polarizing plate on the third pressure-sensitive adhesive layer opposite to the second polarizing element is attached to the second pressure-sensitive adhesive layer on the glass. A laminate is produced by laminating the surface on the side opposite to the side so that the angle formed by the absorption axis of the second polarizer and the absorption axis of the first polarizer is 90 °.
Measurement of the amount of warpage in a moist heat environment: The laminate prepared as described above is allowed to stand in an environment of 60 ° C. and 90% humidity for 250 hours. The laminated body thus obtained is placed on the measuring table of the two-dimensional measuring instrument so that the front-side polarizing plate is on the upper side. Focus on the surface of the measuring table, use the surface as a reference, focus on 25 points on the laminate, measure the height from the reference focus, and measure the height at the 25 measurement points. The difference between the maximum value and the minimum value of the height is taken as the amount of warpage in a moist heat environment.
Measurement of Warpage Amount in High Temperature Environment: The laminate prepared as described above is allowed to stand for 250 hours in an environment of 85 ° C. and 5% humidity with the front side polarizing plate facing up. The laminated body thus obtained is placed on the measuring table of the two-dimensional measuring instrument so that the front-side polarizing plate is on the upper side. Focus on the surface of the measuring table, use the surface as a reference, focus on 25 points on the laminate, measure the height from the reference focus, and measure the height at the 25 measurement points. The difference between the maximum value and the minimum value of the height is taken as the amount of warpage in a high temperature environment.
However, in the measurement of the amount of warpage in the moist heat environment and the measurement of the amount of warpage in the high temperature environment, the 25 points are points in a region 7 mm inside from the end portion of the front side polarizing plate, and the short side direction is It shall be provided at intervals of about 20 mm and at intervals of about 35 mm in the long side direction. The polarizing plate set according to claim 1, wherein the thickness of the first pressure-sensitive adhesive layer is 5 μm or less. The polarizing plate set according to claim 1 or 2, wherein the back-side polarizing plate is the first pressure-sensitive adhesive layer directly laminated on the first polarizer. The polarizing plate set according to claim 1 or 2, wherein the back-side polarizing plate further has a protective film between the first pressure-sensitive adhesive layer and the first polarizer. The first protective film is attached to the first polarizer via an adhesive layer formed from an aqueous adhesive.
The polarizing plate set according to any one of claims 1 to 4, wherein the second protective film is attached to the second polarizer via an adhesive layer formed of an aqueous adhesive. The polarizing plate set according to any one of claims 1 to 5 , wherein the reflective polarizing plate has at least two thin films, and the thin films having at least two layers have different refractive index anisotropy. It has a liquid crystal cell and a pair of polarizing plates arranged on both sides thereof.
The pair of polarizing plates is the polarizing plate set according to any one of claims 1 to 6.
The second protective film, the second polarizing element, the third pressure-sensitive adhesive layer, the liquid crystal cell, the second pressure-sensitive adhesive layer, the first protective film, the first-polarizer, the first pressure-sensitive adhesive layer, and the like. A liquid crystal panel in which reflective polarizing plates are laminated in this order. The liquid crystal panel according to claim 7 , wherein the thickness of the glass substrate constituting the liquid crystal cell is 0.5 mm or less.

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