Laminated polarizing plate and liquid crystal display device

【0001】

[Technical Field of Invention]

The present invention relates to a laminated polarizing plate that can obtain linearly polarized light having an excellent degree of polarization and is useful for improving the visibility of a liquid crystal display device or the like.

【0002】

Background of the Invention

Conventionally, a dichroic polarizing plate in which a dichroic substance such as iodine, herapite, or a dye is adsorbed and oriented in a substrate has been known. Such polarizing plates are often used in liquid crystal display devices and the like. However, since the dichroic polarizing plate utilizes the light absorption of the dichroic substance, the polarized light generally obtained is partially polarized light, and there is a problem that light leakage occurs even if it is arranged in the cross Nicol. It was.

【0003】

The above-mentioned light leakage causes a decrease in contrast when the liquid crystal display device is displayed in black, and a method of increasing the adsorption concentration of a dichroic substance to increase the amount of light absorption and reducing the light leakage is displayed in white. It is difficult to improve the visibility because the brightness of the case is remarkably reduced. The problem of reduced visibility due to light leakage is particularly remarkable in the case of a dye-based dichroic polarizing plate having excellent durability at high temperatures because the two-color ratio of the dye itself is low, and is practically used. Above, it cannot be ignored.

【0004】

PROBLEM TO BE SOLVED: To

INDUSTRIAL APPLICABILITY According to the present invention, a polarizing plate capable of forming a liquid crystal display device or the like having excellent visibility by obtaining linearly polarized light having excellent degree of polarization, having less light leakage due to cross Nicol, and having excellent contrast in black display and brightness in white display. Development is an issue.

【0005】

According to the present invention, a bipolar polarizing plate and a polarizing scattering plate exhibiting scattering anisotropy depending on the polarization direction are provided, and light exhibiting a strong scattering property of the absorption axis of the bipolar polarizing plate and the polarizing scattering plate. It is laminated so that the axes are parallel to each other, and the polarizing scattering plate shows the maximum transmittance of linearly polarized light in the optical axis direction (Δn).₂Direction) or the direction of the optical axis orthogonal to it (Δn)₁When linearly polarized light in the direction) is incident<u style="single">In</u> n_{<u style="single">1</u>}direction<u style="single">Diffusion transmittance</u>/ n_{<u style="single">2</u>}Diffusion transmittance in the direction<u style="single">of</u>ratio<u style="single">But</u>It is composed of a transparent film that exhibits scattering anisotropy of 3 or more and contains minute regions with different birefringence characteristics, and the glass transition temperature of the polymer forming the transparent film is 50 ° C or more.<u style="single">Yes</u>And the minute region is made of a liquid crystal polymer with a glass transition temperature of 50 ° C or higher.<u style="single">The difference in refractive index between the minute region and other parts is Δn.</u>_{<u style="single">1</u>}<u style="single">0.03 or more to 1 or less in the direction, and the relevant Δn</u>_{<u style="single">2</u>}<u style="single">Less than 0.03 in the direction</u>Provided are a laminated polarizing plate having a higher degree of polarization than the above-mentioned two-color polarizing plate, and a liquid crystal display device having the laminated polarizing plate as a polarizing plate on the light source side of a liquid crystal display panel. Is what you do.

【0006】

[Effect of the invention]

According to the present invention, the optical axis of the polarized light scattering plate (direction in which it is difficult to scatter) and the transmission axis of the bicolor polarizing plate correspond to each other to efficiently transmit linearly polarized light, and the light transmittance in the axial direction is excellent. In the direction of the optical axis, which shows the strong scattering property of the polarized light scattering plate corresponding to the absorption axis of the bicolor polarizing plate, linearly polarized light is strongly scattered and the light transmittance is reduced, resulting in a large decrease in the light transmittance as a whole. It is possible to obtain polarized light with a high degree of polarization.

[0007] Therefore, it is possible to form a liquid crystal display device or the like having good visibility, which has less light leakage due to cross Nicol and is excellent in contrast in black display and brightness in white display. Further, the laminated polarizing plate according to the present invention can be efficiently manufactured by a simple operation of laminating each cambium and has excellent mass productivity.<u style="single">It also has excellent heat resistance and durability.</u>There is. Further, by arranging the laminated polarizing plate on the light source side of the liquid crystal display panel, it is possible to avoid visual impairment due to backscattering by the polarizing scattering plate, and it is possible to form a liquid crystal display device having excellent visibility such as contrast.

【0008】

BEST MODE FOR CARRYING OUT THE INVENTION The laminated polarizing plate according to the present invention comprises a bipolar polarizing plate and a polarizing scattering plate exhibiting scattering anisotropy depending on the polarization direction, and the absorption axis of the bipolar polarizing plate and strong scattering of the polarizing scattering plate. It is laminated so that it is parallel to the optical axis showing the property, and the polarizing scattering plate shows the maximum transmittance of linearly polarized light in the optical axis direction (Δn).₂Direction) or the direction of the optical axis orthogonal to it (Δn)₁When linearly polarized light in the direction) is incident<u style="single">In</u> n_{<u style="single">1</u>}direction<u style="single">Diffusion transmittance</u>/ n_{<u style="single">2</u>}Diffusion transmittance in the direction<u style="single">of</u>ratio<u style="single">But</u>It is composed of a transparent film that exhibits scattering anisotropy of 3 or more and contains minute regions with different birefringence characteristics, and the glass transition temperature of the polymer forming the transparent film is 50 ° C or more.<u style="single">Yes</u>And the minute region is made of a liquid crystal polymer with a glass transition temperature of 50 ° C or higher.<u style="single">The difference in refractive index between the minute region and other parts is Δn.</u>_{<u style="single">1</u>}<u style="single">0.03 or more to 1 or less in the direction, and the relevant Δn</u>_{<u style="single">2</u>}<u style="single">Less than 0.03 in the direction</u>It exhibits a higher degree of polarization than the above-mentioned dichroic polarizing plate. Examples are shown in Fig. 1 and Fig. 2. 1 is a dichroic polarizing plate, 3 is a polarization scattering plate, and 2 is an adhesive layer as needed.

【0009】

As the dichroic polarizing plate, an appropriate one having a transmission axis and an absorption axis of linearly polarized light can be used. By the way, as an example, a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, an ethylene-vinyl acetate copolymerization system partially saponified film, and a bicolor substance such as iodine or a bicolor dye. Examples thereof include an iodine-based or dye-based film obtained by adsorbing and stretching the film, and a polarizing film such as a dehydrated product of polyvinyl alcohol or a dehydrogenated product of polyvinyl chloride in which polyene is oriented.

【0010】

Further, a dichroic polarizing plate having a transparent protective layer provided on one side or both sides of the polarizing film can also be mentioned. The transparent protective layer may be provided for an appropriate purpose such as protecting the polarizing film from heat, humidity, etc., for example, an appropriate transparent polymer, in particular, transparency, mechanical strength, and thermal stability. It can be formed of a polymer having excellent moisture shielding properties and the like.

【0011】

Incidentally, examples of the transparent polymer include cellulose-based polymers such as cellulose diacetate and cellulose triacetate, polyethylene and polypropylene, olefin-based polymers such as polyolefins having a cyclo-norbornene structure, and olefin-based polymers such as ethylene-propylene copolymers, and polymethyl methacrylate. Acrylic polymers such as acrylic polymers, ester polymers such as polyethylene terephthalate and polyethylene naphthalate, styrene polymers such as polystyrene and acrylonitrile-styrene copolymers (AS polymers), and amide polymers such as nylon and aromatic polyamide. ..

【0012】

In addition, carbonate-based polymers and vinyl chloride-based polymers, imide-based polymers and sulfone-based polymers, polyether sulfone and polyether ether ketones, polyphenylene sulfide and vinyl alcohol-based polymers, vinylidene chloride-based polymers and vinyl butyral-based polymers, allylate-based polymers and poly Oxymethylene, silicone-based polymers and urethane-based polymers, ether-based polymers and vinyl acetate-based polymers, blends of the above polymers, phenol-based and melamine-based, acrylic and urethane-based, urethane acrylic-based, epoxy-based and silicone-based, etc. Heat-curable or ultraviolet-curable polymers are also examples of the above-mentioned transparent polymers.

【0013】

The transparent protective layer can be formed by an appropriate method such as a transparent polymer coating method or a polymer film laminating method. For example, silica or alumina having an average particle size of 0.5 to 50 μm, titania or zirconia, tin oxide or the like can be formed on the transparent protective layer. It contains transparent fine particles such as inorganic fine particles that may be conductive such as indium oxide, cadmium oxide and antimony oxide, and organic fine particles such as crosslinked or uncrosslinked polymers to impart a fine uneven structure to the surface and provide light diffusivity. It can also be used to indicate. Further, the transparent protective layer can also be used as a polarizing scattering plate, and in that case, the polarizing scattering plates that also serve as the transparent protective layer can be provided on both sides of the polarizing film.

【0014】

Further, for example, a dichroic polarizing plate having at least an orientation layer made of a dichroic dye-containing liquid crystal material or a coating film of a dichroic lyotropic liquid crystal dye can be mentioned. By the way, as an example of a dichroic polarizing plate using a liquid crystal material containing a dichroic dye, an appropriate dye exhibiting absorption dichroism is mixed with the liquid crystal material, and the mixed solution is developed to orient the liquid crystal material. Something like that. As the liquid crystal material, for example, one or more suitable types such as a nematic type or smectic type liquid crystal or a liquid crystal polymer may be used. Further, an appropriate alignment means such as an alignment film, an alignment base material, an electric field or a magnetic field can be applied to the alignment treatment of the liquid crystal material.

【0015】

On the other hand, as an example of a dichroic polarizing plate using a dichroic lyotropic liquid crystal dye, a chromogen composed of an azo or a polycyclic compound imparts liquid crystal property, and a sulfonic acid or a salt thereof imparts water solubility. As a whole, the lyotropic liquid crystallinity is shown by the formula: (chromogen) (SO).₃M) A solution of a water-soluble organic dye represented by n (Japanese Patent Publication No. 8-511109) coated under shear stress can be mentioned. In this case, the orientation treatment can be performed by the applied shear stress.

【0016】

A dichroic polarizing plate having an alignment layer of a coating film is a transparent protective layer in which an alignment layer of the coating film is provided on one side or both sides of a supporting base material made of an exemplary polymer or the like, or a coating film thereof. It can be obtained in an appropriate form such as that covered with a transparent protective layer, and it is also possible to obtain the alignment layer of the coating film as being supported by the polarizing scattering plate by using a polarizing scattering plate as the supporting base material. it can. In this case, the dichroic polarizing plate having the alignment layer of the coating film is generally excellent in thinness, and the polarizing scattering plate also serves as the supporting base material, and a separate supporting base material can be omitted, so that the coating film itself has two colors. It is possible to form the entire sex polarizing plate to obtain a laminated polarizing plate that is superior in thinness.

【0017】

The alignment layer of the polarizing film or coating film that forms the above-mentioned dichroic polarizing plate has a light transmittance similar to that of the dye-based material containing the above-mentioned dichroic substance because of the improvement of brightness and contrast. Those having an excellent degree of polarization Among them, those having a light transmittance of 40% or more and a degree of polarization of 95% or more are preferably used.

[0018] On the other hand, as the polarization scattering plate used for forming the laminated polarizing plate, one exhibiting a specific scattering anisotropy depending on the polarization direction is used.<u style="single">,And</u>It has an optical axis that shows the maximum transmittance of linearly polarized light and an optical axis that strongly scatters linearly polarized light in the direction orthogonal to the optical axis by dispersing and containing birefringent minute regions with different refractive indexes in a transparent film. thing<u style="single">Used by</u>Be done.

【0019】

The scattering anisotropy is the optical axis showing the maximum transmittance of linearly polarized light or the light axis with the weakest scattering of linearly polarized light from the viewpoint of suppressing light leakage by cross Nicol and achieving high light transmittance. Direction ( n₂Direction) or the direction orthogonal to it or the optical axis direction (Δn) that scatters linearly polarized light most strongly.₁The diffusion transmittance when linearly polarized light in the direction) is incident is Δn._{<u style="single">1</u>}Direction / n_{<u style="single">2</u>}It shows 3 or more characteristics based on the direction ratio, and it is preferable to show 5 or more characteristics.

【0020】

Further, from the point of view of brightness due to polarization transmission in the Δn2 direction in the case of a laminated polarizing plate, the higher the light transmittance of the linearly polarized light in the Δn2 direction is, the more preferable it is, and 80% or more, particularly 90% or more of all. It is preferable that it shows the light transmittance. On the other hand, from the viewpoint of improving the degree of polarization, the lower the light transmittance of linearly polarized light in the Δn1 direction, the more preferable, and it is preferable that the total light transmittance is less than 80%, particularly 75% or less.

【0021】

As mentioned above<u style="single">Diffusion transmittance ratio of 3 or more</u>The polarizing scattering plate showing scattering anisotropy has Δn in the above-mentioned minute region and other parts.₁0.03 or more in the direction<u style="single">~ 1 or less</u>Refractive index difference ( n₁), Above 0.035<u style="single">Up,</u>In particular, the difference in refractive index of 0.04 or more and 0.5 or less (Δn)₁), N₂Refractive index difference less than 0.03 in the direction (Δn₂), Especially 0.02 or less, especially 0.01 or less, etc., as small as possible refractive index difference (Δn)₂)<u style="single">Noto</u>Can be obtained. Therefore, the relevant Δn₂Is as close to zero as possible, that is, the refractive index of the minute region and the other portion are substantially the same. By using the above-mentioned difference in refractive index, Δn₁Excellent scattering in the direction, n₂It can be excellent in the maintainability of the polarized state in the direction and the straight-line transparency.

【0022】

In the above, the refractive index difference characteristics of Δn1 and Δn2 cause scattering anisotropy, but the formation of such a polarizing scattering plate is made of an appropriate material having excellent transparency, such as polymers and liquid crystals. It can be carried out by an appropriate method such as a method of obtaining an alignment film by using one type or two or more types in a combination of forming regions having different birefringence characteristics by an appropriate orientation treatment such as a stretching treatment.

【0023】

Incidentally, examples of the above combinations include a combination of polymers and liquid crystals, a combination of an isotropic polymer and an anisotropic polymer, and a combination of anisotropic polymers. From the viewpoint of the dispersion distribution of minute regions, the combination of phase separation is preferable, and the dispersion distribution can be controlled by the compatibility of the materials to be combined. The phase separation can be carried out by an appropriate method such as a method of solubilizing the incompatible material with a solvent or a method of mixing the incompatible material under heating and melting.

【0024】

When the orientation treatment is performed by the stretching method in the above combination, the combination of the polymers and the liquid crystal and the combination of the isotropic polymer and the anisotropic polymer are a combination of the anisotropic polymers at an arbitrary stretching temperature and stretching ratio. Then, the desired polarizing scattering plate can be formed by appropriately controlling the stretching conditions. Anisotropic polymers are classified as positive or negative based on the characteristics of the change in refractive index in the stretching direction. However, in the present invention, either positive or negative anisotropic polymers can be used, and positive or negative, positive or negative, or positive or negative. It can be used in any combination.

【0025】

Examples of the above-mentioned polymers include the transparent polymers exemplified in the above-mentioned transparent protective layer. In particular, as the polymer forming the transparent film, a polymer having a weighted deflection temperature of 80 ° C. or higher and a glass transition temperature of 110 ° C. or higher is preferable from the viewpoint of thermal stability of optical characteristics.

[0026] Examples of liquid crystals include a nematic phase and a smectic phase at room temperature or high temperature such as cyanobiphenyl type, cyanophenylcyclohexane type, cyanophenyl ester type, benzoic acid phenyl ester type, phenylpyrimidin type and mixtures thereof. Present<u style="single">Rack</u>Examples thereof include bridging liquid crystal monomers and liquid crystal polymers that exhibit a nematic phase or a smectic phase at room temperature or high temperature. The crosslinkable liquid crystal monomer is usually subjected to an orientation treatment and then crosslinked by an appropriate method such as heat or light to obtain a polymer.

【0027】<u style="single">In the above</u>From the point of obtaining a polarizing scattering plate with excellent heat resistance and durability<u style="single">、</u>Polymers with a glass transition temperature of 50 ° C or higher, especially 80 ° C or higher, especially polymers with a glass transition temperature of 110 ° C or higher and a weighted deflection temperature of 80 ° C or higher, and crosslinkable liquid crystal monomers or liquid crystal polymers. Used in combination of<u style="single">To.</u>As the liquid crystal polymer, an appropriate one such as a main chain type or a side chain type can be used, and the type is not particularly limited. A liquid crystal polymer that can be preferably used in terms of the formability and thermal stability of minute regions having excellent uniformity of particle size distribution, moldability into a film, and ease of orientation treatment has a degree of polymerization of 8 or more, especially 10 As mentioned above, especially those of 15 to 5000.

【0028】

For the formation of a polarizing scattering plate using a liquid crystal polymer, for example, one or two or more kinds of polymers for forming a transparent film and one or more kinds of liquid crystal polymers for forming a minute region are mixed. Then, a polymer film in which the liquid crystal polymer is dispersed and contained in a minute region is formed and oriented by an appropriate method to form regions having different birefringence characteristics.

【0029】

In the above, the above-mentioned refractive index difference Δn due to the orientation treatment¹, n²From the viewpoint of controllability, a liquid crystal polymer having a glass transition temperature of 50 ° C. or higher and exhibiting a nematic liquid crystal phase in a temperature range lower than the glass transition temperature of the combined polymers can be preferably used. Incidentally, as a specific example thereof, a side chain type liquid crystal polymer having a monomer unit represented by the following general formula can be mentioned.

【0030】

General formula:<img he="26" id="000002" wi="42" file="2_0003594868.tif" img-format="tif" img-content="drawing" /> 【0031】

In the above general formula, X is a skeletal group that forms the main chain of the liquid crystal polymer, and may be formed of an appropriate connecting chain such as linear, branched, or cyclic. By the way, examples include polyacrylates and polymethacrylates, poly-α-haloacrylates and poly-α-cyanoacrylates, polyacrylamides and polyacrylonitrile, polymethacrylonitrile and polyamides, polyesters and the like. Examples thereof include polyurethanes, polyethers, polyimides, and polysiloxanes.

【0032】

Further, Y is a spacer group branched from the main chain, and preferred spacer groups Y are, for example, ethylene, propylene, butylene, pentylene, hexylene, octylene, decylene, etc. Undecylene, dodecylene, octadecylene, ethoxyethylene, methoxybutylene, etc.

【0033】

On the other hand, Z is a mesogen group that imparts nematic orientation, and examples thereof include the following compounds.<img he="97" id="000003" wi="104" file="3_0003594868.tif" img-format="tif" img-content="drawing" /> 【0034】

The terminal substituent A in the compound is, for example, a haloalkyl group, a haloalkenyl group, or a haloalkenyl group in which one or more of a cyano group, an alkyl group, an alkenyl group, an alkoxy group, an oxaalkyl group, or hydrogen is substituted with fluorine or chlorine. It may be an appropriate one such as.

【0035】

In the above, the spacer group Y and the mesogen group Z may be bonded via an ether bond, that is, -O-. Further, the phenyl group in the mesogen group Z may have one or two hydrogens substituted with a halogen, and in that case, chlorine or fluorine is preferable as the halogen.

【0036】

The side chain type liquid crystal polymer having the nematic orientation described above may be an appropriate thermoplastic polymer such as a homopolymer or a copolymer having a monomer unit represented by the general formula, and the one having excellent monodomain orientation is particularly excellent. preferable. The liquid crystal polymer can also be used for forming the above-mentioned dichroic polarizing plate.

【0037】

The formation of the polarization scattering plate using the above-mentioned nematically oriented liquid crystal polymer is, for example, a polymer for forming a polymer film and a glass transition exhibiting a nematic liquid crystal phase in a temperature range lower than the glass transition temperature of the polymer. A liquid crystal polymer having a temperature of 50 ° C or higher, especially 60 ° C or higher, particularly 70 ° C or higher is mixed to form a polymer film in which the liquid crystal polymer is dispersed and contained in a minute region, and then the minute region is formed. The liquid crystal polymer to be subjected to heat treatment can be oriented to the nematic liquid crystal phase, and the orientation state can be cooled and fixed.

【0038】

The polymer film containing the above-mentioned minute regions in a dispersed manner, that is, the film to be oriented, can be formed by an appropriate method such as a casting method, an extrusion molding method, an injection molding method, a roll molding method, or a casting method. It can also be developed in a monomer state and polymerized by heat treatment or radiation treatment such as ultraviolet rays to form a film.

【0039】

A method of forming a film by a casting method, a casting method, or the like is preferable from the viewpoint of obtaining a polarizing scattering plate having excellent uniform distribution in a minute region. In that case, the size and distribution of the minute region can be controlled by the type of solvent, the viscosity of the mixed solution, the drying rate of the mixed solution developing layer, and the like. Incidentally, in order to reduce the area of a minute region, it is advantageous to reduce the viscosity of the mixed solution and accelerate the drying rate of the mixed solution developing layer.

【0040】

The thickness of the film to be oriented can be appropriately determined, but is generally 1 μm to 3 mm, especially 5 μm to 1 mm, and particularly 10 to 500 μm from the viewpoint of alignment processability and the like. When forming the film, for example, an appropriate additive such as a dispersant, a surfactant, an ultraviolet absorber, a color tone adjusting agent, a flame retardant, a mold release agent, and an antioxidant can be added.

【0041】

As described above, the orientation treatment is performed by applying an electric field or a magnetic field at a temperature equal to or higher than, for example, a uniaxial or biaxial, sequential biaxial or Z-axis stretching treatment method or rolling method, a glass transition temperature or a liquid crystal transition temperature, and quenching the orientation. One or two appropriate methods that can control the refractive index by orientation, such as the immobilization method, the flow orientation method during film formation, and the self-orientation method of the liquid crystal based on the slight orientation of the isotropic polymer. It can be carried out using the above. Therefore, the obtained polarizing scattering plate may be a stretched film or a non-stretched film. When the stretched film is used, a brittle polymer can be used, but a polymer having excellent extensibility can be particularly preferably used.

【0042】

When the minute region is composed of the above-mentioned liquid crystal polymer, for example, the liquid crystal polymer dispersed and distributed as a minute region in the polymer film is heated to a temperature at which the desired liquid crystal phase such as the nematic phase is exhibited and melted, and the orientation is regulated. It can also be carried out by a method of aligning under the action of force and quenching to fix the oriented state. It is preferable that the orientation state of the minute region is in the monodomain state as much as possible from the viewpoint of preventing variations in optical characteristics.

【0043】

As the orientation regulating force, for example, a stretching force by a method of stretching a polymer film at an appropriate magnification, a sharing force at the time of film formation, an appropriate regulating force capable of orienting a liquid crystal polymer such as an electric field or a magnetic field can be used. It can be applied, and the alignment treatment of the liquid crystal polymer can be performed by applying one or more of the regulatory forces.

【0044】

Therefore, the portion of the polarizing scatter plate other than the minute region may be birefringent or isotropic. A polarizing scattering plate that exhibits birefringence as a whole can be obtained by using an orientation birefringent polymer for film formation by the molecular orientation in the film forming process described above, and if necessary, for example, stretching. Birefringence can be imparted or controlled by adding known orientation means such as treatment. As for the polarizing scattering plate whose portion other than the minute region is isotropic, for example, an isotropic polymer is used for film formation, and the film is stretched in a temperature region equal to or lower than the glass transition temperature of the polymer. It can be obtained by a method such as

【0045】

Therefore, the above-mentioned alignment treatment of the minute region is an operation of orienting a material such as a liquid crystal polymer forming the minute region in a certain direction as much as possible to increase the difference in refractive index in the Δn1 direction, or the operation of increasing the refractive index difference in the Δn2 direction. It can also be positioned as an operation to reduce the difference in refractive index, or an operation to achieve both of them.

【0046】

It is preferable that the minute regions in the polarizing scattering plate are dispersed and distributed as evenly as possible from the viewpoint of homogeneity such as the scattering effect. The size of the minute region, especially the length in the Δn1 direction, which is the scattering direction, is related to backscattering (reflection) and wavelength dependence. Improvement of light utilization efficiency, prevention of coloring due to wavelength dependence, prevention of visual obstruction of minute areas or prevention of obstruction of clear display, and preferable size of minute areas from the viewpoint of film forming property and film strength. In particular, the preferred length in the Δn1 direction is 0.05 to 500 μm, especially 0.08 to 250 μm, particularly 0.1 to 50 μm, based on the average length.

【0047】

The minute region usually exists in the polarization scattering plate in the state of the domain, but the length in the Δn2 direction is not particularly limited. The ratio of minute regions to the polarizing scattering plate can be appropriately determined from the viewpoint of scattering property in the Δn1 direction, but generally 0.1 to 70% by weight, especially 0.5 to 50% by weight, in consideration of film strength and the like. In particular, it is said to be 1 to 30% by weight.

【0048】

The polarization scattering plate can be formed by a single layer of a film exhibiting the above-mentioned birefringence characteristics, or can be formed by superimposing two or more such films. By superimposing the film, a synergistic scattering effect of an increase in thickness or more can be exhibited. The superposed body may be one in which the film is superposed at an arbitrary arrangement angle in the Δn1 direction or the Δn2 direction, but the Δn1 direction has a parallel relationship between the upper and lower layers from the viewpoint of expanding the scattering effect. It is preferable that they are superimposed in this way. The number of superposed films may be an appropriate number of two or more layers.

【0049】

The films to be superposed may have the same Δn1 or Δn2, or may be different. It is preferable that the parallel relationship between the upper and lower layers in the Δn1 direction is as parallel as possible, but deviation due to work error is allowed. If there is a variation in the Δn1 direction, etc., it is based on the average direction. The film in the superposed body may be simply stacked, but it is possible to prevent the optical axis from shifting in the Δn1 direction and prevent foreign matter from entering each interface through an adhesive layer or the like. It is preferable that they are adhered. For the adhesion, an appropriate adhesive such as a hot melt type or an adhesive type can be used. An adhesive layer having a refractive index difference with the film as small as possible is preferable from the viewpoint of suppressing reflection loss, and the film or a polymer forming a minute region thereof can be used for adhesion.

【0050】

The laminated polarizing plate according to the present invention is obtained by laminating them so that the absorption axis of the dichroic polarizing plate and the optical axis (Δn1 direction) showing the strong scattering property of the polarizing scattering plate are in a parallel relationship. For the formation, the polarization scattering plate 3 can be arranged on the front and back of the dichromatic polarizing plate 1 as illustrated in FIG. The polarization scattering plates on the front and back sides of the parallel relationship and the case where the polarization scattering plates are arranged on the front and back surfaces of the dichroic polarizing plate can be the same as the case of forming the above-mentioned superimposed type polarizing scattering plate. When a dichroic polarizing plate and a polarizing scattering plate are formed by a stretching method, the absorption axis and the Δn1 direction are usually the stretching directions. Can be continuously and efficiently formed.

【0051】

In the practical use of the laminated polarizing plate according to the present invention, it is also possible to obtain a laminated body to which an appropriate optical component such as a retardation plate is added as needed. The laminated body and the laminated polarizing plate according to the present invention may be simply stacked or bonded via an adhesive layer or the like. The adhesive layer can be the same as the case of forming the above-mentioned superimposed type polarizing scattering plate.

【0052】

The optical component to be laminated is not particularly limited, and may be, for example, a backlight such as a retardation plate or a light guide plate, a polarizing separation plate made of a reflector or a multilayer film, a liquid crystal cell, or the like. Further, the optical components such as the retardation plate to be laminated may be of various types. That is, for retardation plates, 1/4 wave plate, 1/2 wave plate, stretched film type with uniaxial or biaxial, tilted film type with molecular orientation in the thickness direction, liquid crystal polymer type, viewing angle and birefringence There are various types such as a type that compensates for the phase difference due to birefringence and a type in which they are laminated, and any of these types can be used in the present invention. Incidentally, specific examples of the retardation plate include a stretched film and a liquid crystal polymer made of a transparent polymer exemplified by the transparent protective layer and a scattering polarizing plate, and a liquid crystal polymer having a twisted orientation.

【0053】

As a specific example of the light guide plate, a linear light source such as a (cold, hot) cathode fluorescent lamp or a light source such as a light emitting diode or EL is arranged on the side surface of the transparent resin plate, and the light source is transmitted through the resin plate. Examples include those in which light is emitted to one side of a plate by diffusion, reflection, diffraction, interference, or the like. When forming a laminated polarizing plate including a light guide plate, a prism array layer made of a prism sheet or the like for controlling the light emission direction, a diffusion plate for obtaining uniform light emission, and a light guide plate for emitting light from a linear light source. Auxiliary means such as a light source holder for guiding to the side surface of the light guide plate may be arranged at a predetermined position such as the upper and lower surfaces of the light guide plate or the side surface as necessary, and one layer or two or more layers may be arranged to form an appropriate combination.

【0054】

When forming the laminate, one type or two or more types of optical components can be used, and for example, two or more layers of the same type of optical components such as a retardation plate can be laminated. In that case, the characteristics of the optical components such as the phase difference may be the same or different. The optical components may be arranged at appropriate positions outside or inside the laminate. The above-mentioned laminated polarizing plate and laminated body can be formed by a method in which the forming layers are sequentially and separately laminated in a manufacturing process of, for example, a liquid crystal display device, but the laminated polarizing plate and the laminated body should be formed in advance as a laminated integrated product as described above. However, it is preferable in terms of quality stability and efficiency of laminating work.

【0055】

Further, as necessary, an ultraviolet absorber such as a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound, a cyanoacrylate compound, or a nickel complex salt compound is blended in each layer forming the laminated polarizing plate or the laminate. It can have the ability to absorb ultraviolet rays.

【0056】

Based on the above-mentioned features, the laminated polarizing plate according to the present invention can be used for an appropriate application according to a conventional product, for example, for forming a liquid crystal display device. An appropriate type of liquid crystal display panel can be used in forming the liquid crystal display device, and the type is not particularly limited.

【0057】

The position of the laminated polarizing plate in the liquid crystal display device is not particularly limited and can be arranged on the viewing side. However, the light source of the liquid crystal display panel is more important than avoiding visual impairment due to backward scattering by the scattering polarizing plate. It is preferable to arrange it as a polarizing plate on the side.

【0058】

[Example]

Example 1 Norbornen-based resin with a glass transition temperature of 182 ° C (JSR, Arton, weight deflection temperature 165 ° C) 970 parts (weight part, the same applies hereinafter) and a glass transition temperature of 80 ° C expressed by the following formula. A polymer film with a thickness of 70 μm was formed by a casting method using a 20 wt% dichloromethane solution in which 30 parts of a liquid crystal polymer having a nematic liquefaction temperature of 100 to 290 ° C was dissolved, and the polymer film was formed in an atmosphere of 180 ° C in an atmosphere of 180 ° C. After stretching treatment twice, it was rapidly cooled to obtain a polarization scattering film.

【0059】<img he="29" id="000004" wi="97" file="4_0003594868.tif" img-format="tif" img-content="drawing" /> 【0060】

The polarizing scattering film is a transparent birefringent film made of a norbornene-based resin in which a liquid crystal polymer is dispersed in a domain having substantially the same shape with a major axis in the stretching direction.₁Is 0.230, n₂Was 0.029. In addition, the size of the minute region (domain) due to the liquid crystal polymer was estimated from the coloring due to the phase difference by observing with a polarizing microscope.₁The average length in the direction was 1 μm.

【0061】

Furthermore, as a result of measuring the diffusion transmittance of linearly polarized light in the polarizing scattering film using a haze meter, Δn₁In the direction (minimum transmittance)<u style="single">67</u>%, n₂In the direction (maximum transmittance)<u style="single">11</u>% And its ratio n_{<u style="single">1</u>}Direction / n_{<u style="single">2</u>}The direction was 6.1. In addition, as a result of measuring the total light transmittance with an integrating sphere spectrophotometer with linearly polarized light incident, Δn₁75% in the direction, n₂It was 92% in the direction.

【0062】

An iodine-based bicolor polarizing plate having a transmittance of 44% and a degree of polarization of 97.0%, which is composed of the above-mentioned polarizing scattering film and an iodine-dyed polyvinyl alcohol-based stretched film, has an absorption axis of Δn of the polarizing scattering film._{<u style="single">1</u>}A laminated polarizing plate was obtained by adhering through an acrylic adhesive layer so as to be parallel to the direction.

【0063】

Example 2 A laminated polarizing plate was obtained according to Example 1 except that a polarizing scattering film was adhered to both sides of the dichroic polarizing plate.

【0064】

Example 3 A laminated polarizing plate was obtained according to Example 1 except that two layers of polarizing scattering films were laminated and adhered to the same side of the dichroic polarizing plate.

【0065】

Example 4 A laminated polarizing plate was obtained according to Example 1 except that a dye-based bicolor polarizing plate having a transmittance of 41% and a degree of polarization of 90.0% was used instead of the iodine-based bicolor polarizing plate.

【0066】

Comparative Example 1 The iodine-based dichroic polarizing plate of Example 1 was used alone without using the polarizing scattering film.

【0067】

Comparative Example 2 The dye-based dichroic polarizing plate of Example 4 was used alone without using the polarizing scattering film.

【0068】

The light transmittance of the (laminated) polarizing plates obtained in the evaluation test examples and comparative examples was examined by an integrating sphere spectrophotometer. In addition, the two sheets are placed in parallel Nicol or Cross Nicol to check the light transmittance, and the formula: Polarization = 100 × {(Parallel transmittance-Orthogonal transmittance) / (Parallel transmittance + Orthogonal transmittance) The degree of polarization was calculated by.

【0069】

The above results are shown in the table below.<img he="52" id="000005" wi="123" file="5_0003594868.tif" img-format="tif" img-content="drawing" /> 【0070】

From the table, it can be seen that the degree of polarization can be improved by combining with the scattering polarizing plate without significantly reducing the light transmittance. Further, it can be seen that when a two-layer polarization scattering plate is arranged on the dichroic polarizing plate, the degree of polarization can be further increased.

[Simple explanation of drawings]

FIG. 1 is a cross-sectional view of an embodiment. FIG. 2 is a cross-sectional view of another embodiment.

1: Dichroic polarizing plate 2: Adhesive layer 3: Polarized light scattering plate