JP2003029042A - Polarizer, polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizer consisting of a polyvinylalcohol film having sufficient high durability. SOLUTION: In the polarizer consisting of a polyvinylalcohol film dyed with iodine and containing zinc, the ratio of zinc content (wt.%)/iodine content (wt.%) ranges from 0.05 to 0.6.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a polarizer.
The present invention also relates to a polarizing plate using the polarizer, and a liquid crystal display device using the polarizing plate.

[0002]

2. Description of the Related Art Conventionally, a polarizer used for a liquid crystal display device has a high transmittance and a high degree of polarization.
A polyvinyl alcohol film dyed with iodine is used. In addition, the polarizer is usually used as a polarizing plate having a protective film such as a triacetyl cellulose film attached to one side or both sides thereof.

In recent years, liquid crystal display devices are often used for a long period of time under high temperature conditions and the like due to their widespread use, and there is a demand for a liquid crystal display device having a small change in hue according to the intended use. ing. Along with that, on the polarizing plate,
Durability is required so that the optical characteristics do not deteriorate when left under high temperature conditions or under high temperature and humidity conditions.

For example, JP-A-54-16575, JP-A-61-175602, and JP-A-2000-
Japanese Patent No. 35512 discloses that it is possible to improve durability by adding an appropriate amount of zinc ions to a polarizer made of a polyvinyl alcohol film dyed with iodine. More specifically, it has been shown that, as durability, it is possible to prevent red void (polarization of long-wavelength light) that occurs in crossed Nicols, which occurs when left under high temperature conditions. However, liquid crystal display devices are required to have higher durability due to the expansion of their fields of use.

[0005]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a polarizer made of a polyvinyl alcohol film which can satisfy high durability. Another object is to provide a polarizing plate using the polarizer, and a liquid crystal display device using the polarizing plate.

[0006]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have found that the above-mentioned object can be achieved by a polarizer shown below, and have completed the present invention.

That is, according to the present invention, in a polarizer made of a polyvinyl alcohol film dyed with iodine and containing zinc, the value of zinc content (wt%) / iodine content (wt%) is 0.05 to 0. A polarizer characterized by being 0.6.

In the present invention, the zinc content of the polyvinyl alcohol film for improving the durability of the polarizer is not only the content itself, but the ratio to the content of iodine is an important parameter. The inventors have found that, by adjusting the value of zinc content (wt%) / iodine content (wt%) in the polyvinyl alcohol-based film within the above range, a polarizer having high durability was obtained. To obtain a more durable polarizer, zinc content (wt%)
/ Iodine content (wt%) value is 0.05-0.6,
Furthermore, it is preferable to adjust the range to 0.06 to 0.4.

The present invention also relates to a polarizing plate having a transparent protective layer provided on at least one surface of the above-mentioned polarizer. Furthermore, the present invention relates to a liquid crystal display device using at least one of the polarizing plates.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Polyvinyl alcohol or its derivative is used as the material of the polyvinyl alcohol film applied to the polarizer of the present invention. Examples of the derivative of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal, and the like, olefins such as ethylene and propylene, acrylic acid, methacrylic acid, unsaturated carboxylic acids such as crotonic acid, and alkyl esters thereof.
Examples include those modified with acrylamide. Polyvinyl alcohol having a degree of polymerization of about 1000 to 10,000 and a degree of saponification of about 80 to 100 mol% is generally used.

The polyvinyl alcohol-based film may contain additives such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, such as glycerin, diglycerin, and triglycerin. Examples thereof include ethylene glycol, propylene glycol and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is 20 in the polyvinyl alcohol film.
It is preferable that the content is not more than wt%.

The polyvinyl alcohol film (unstretched film) is subjected to a uniaxial stretching treatment, an iodine dyeing treatment and a zinc impregnation treatment, and further a boric acid treatment according to a conventional method. The polyvinyl alcohol-based film (stretched film) that has been subjected to the above treatment is dried according to a conventional method to be a polarizer.

The iodine content (% by weight) and the zinc content (% by weight) in the polyvinyl alcohol film (stretched film) have a zinc content / iodine content value of 0.05 to 0.6. Adjusted to be within range. In addition, polyvinyl alcohol film (stretched film)
It is preferable that the content of iodine in the composition is adjusted to usually about 0.5 to 5% by weight, preferably 1 to 3% by weight so that the polarizer exhibits a good polarization degree. Further, the content of zinc is usually 0.03 from the viewpoint of durability.
It is preferable to adjust the amount to about 2% by weight, preferably 0.05 to 1% by weight.

The stretching method in the uniaxial stretching treatment is not particularly limited, and either a wet stretching method or a dry stretching method can be adopted, but the dry stretching method is preferably used. Examples of the stretching means in the dry stretching method include a roll-roll stretching method, a heated roll stretching method, and a compression stretching method. The stretching can be performed in multiple stages. In the stretching means, the unstretched film is usually heated. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the stretch ratio is about 2 to 7 times, preferably 3 to 6.5.
It is desirable to set the number of times, more preferably 3.5 to 6 times. The thickness of the stretched film is preferably about 5 to 40 μm.

The iodine dyeing treatment is generally carried out by immersing a polyvinyl alcohol film in an iodine solution. When an aqueous iodine solution is used as the iodine solution, an aqueous solution containing iodine and iodine as a dissolution aid such as potassium iodide is used. The iodine concentration is about 0.01 to 0.5% by weight, preferably 0.02 to 0.4% by weight, and the potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02%.
It is preferably used in an amount of 8 wt%.

In the iodine dyeing treatment, the temperature of the iodine solution is usually about 20 to 50 ° C, preferably 25 to 40 ° C.
Is. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds. In the iodine dyeing treatment, the iodine content in the polyvinyl alcohol-based film is adjusted to be in the above range by adjusting the conditions such as the concentration of the iodine solution, the immersion temperature of the polyvinyl alcohol-based film in the iodine solution, and the immersion time. . The iodine dyeing treatment may be performed at any stage before the uniaxial stretching treatment, during the uniaxial stretching treatment, and after the uniaxial stretching treatment.

The boric acid treatment is carried out by immersing the polyvinyl alcohol film in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is about 2 to 15% by weight, preferably 3 to 10% by weight. Iodine ions can be added to the boric acid aqueous solution by potassium iodide. A boric acid aqueous solution containing potassium iodide can give a polarizer with little coloring, that is, a so-called neutral gray polarizer having an almost constant absorbance over almost the entire wavelength range of visible light.

In the treatment with boric acid, the temperature of the boric acid aqueous solution is, for example, 50 ° C. or higher, preferably 50 to 85 ° C. The immersion time is usually 100 to 1200 seconds, preferably 150 to 600 seconds, and more preferably 200 to
It is about 500 seconds. The step of applying the boric acid treatment is after the iodine dyeing treatment. The boric acid treatment is performed during or after uniaxial stretching.

A zinc salt solution is used for the zinc impregnation treatment. Examples of zinc salts include zinc halides such as zinc chloride and zinc iodide, zinc sulfate, and zinc acetate. The concentration of zinc ions in the aqueous zinc salt solution is in the range of about 0.2 to 10% by weight, preferably 0.5 to 7% by weight. As the zinc salt solution, it is preferable to use an aqueous solution containing iodide ions such as potassium iodide because zinc ions can be easily impregnated. The concentration of potassium iodide in the zinc salt solution is about 0.5 to 10% by weight, preferably 1 to 8% by weight.

In the zinc impregnation treatment, the temperature of the zinc salt solution is usually about 15 to 60 ° C, preferably 25 to 40 ° C. Immersion time is usually about 1 to 120 seconds, preferably 3
~ 90 seconds range. For zinc impregnation treatment,
By adjusting conditions such as the concentration of the zinc salt solution, the immersion temperature of the polyvinyl alcohol-based film in the zinc salt solution, and the immersion time, the zinc content in the polyvinyl alcohol-based film is adjusted to fall within the above range. The stage of the zinc impregnation treatment is not particularly limited, and may be before the iodine dyeing treatment, before the iodine dyeing treatment, and before the immersion treatment in a boric acid aqueous solution, or after the boric acid treatment. Alternatively, a zinc salt may be allowed to coexist in the iodine dyeing solution, and this may be performed simultaneously with the iodine dyeing process. In order to prevent the precipitation of boric acid by the boric acid aqueous solution, it is preferable to carry out zinc impregnation treatment after boric acid treatment.

The obtained polarizer can be made into a polarizing plate having a transparent protective layer on at least one surface thereof according to a conventional method. The transparent protective layer can be provided as a coating layer made of a polymer or as a laminated layer of a film. As the transparent polymer or film material for forming the transparent protective layer, an appropriate transparent material can be used, but a material having excellent transparency, mechanical strength, thermal stability, moisture barrier property and the like is preferably used. Examples of the material for forming the transparent protective layer include polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, acrylic polymers such as polymethylmethacrylate, polystyrene and acrylonitrile. Examples thereof include styrene polymers such as styrene copolymers (AS resin) and polycarbonate polymers. Also, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers. , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer,
Vinyl alcohol-based polymers, vinylidene chloride-based polymers, vinyl butyral-based polymers, arylate-based polymers, polyoxymethylene-based polymers, epoxy-based polymers, and blends of the aforementioned polymers are also examples of polymers forming the transparent protective layer. .

The surface of the transparent protective film on which the polarizer is not adhered (the surface on which the coating layer is not provided) is subjected to a hard coat layer, an antireflection treatment, a sticking prevention treatment, and a treatment for the purpose of diffusion or antiglare. May be

The hard coat treatment is carried out for the purpose of preventing scratches on the surface of the polarizing plate, and for example, a cured film excellent in hardness and sliding properties made of an appropriate ultraviolet curable resin such as acrylic or silicone is used. It can be formed by a method of adding to the surface of the transparent protective film.
The antireflection treatment is carried out for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to conventional methods. Further, the sticking prevention treatment is performed for the purpose of preventing adhesion with an adjacent layer.

The antiglare treatment is carried out for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visual recognition of the light transmitted through the polarizing plate. For example, a sandblasting method or an embossing method is used. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a surface-rendering method or a method of blending transparent particles. The fine particles to be contained in the formation of the surface fine uneven structure are, for example, conductive particles made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles and organic fine particles made of a crosslinked or uncrosslinked polymer are used. When forming the surface fine uneven structure, the amount of the fine particles used is generally about 2 to 50 parts by weight based on 100 parts by weight of the transparent resin forming the surface fine uneven structure.
25 parts by weight is preferred. The anti-glare layer may also serve as a diffusion layer (such as a viewing angle enlarging function) for diffusing the light transmitted through the polarizing plate and enlarging the viewing angle.

The antireflection layer, the antisticking layer, the diffusion layer, the antiglare layer and the like can be provided on the transparent protective film itself, or can be provided as an optical layer separately from the transparent protective layer. it can.

An adhesive is used for the adhesion treatment between the polarizer and the transparent protective film. Examples of the adhesive include isocyanate adhesives, polyvinyl alcohol adhesives, gelatin adhesives, vinyl latex adhesives, and water-based polyesters. The adhesive is usually used as an adhesive composed of an aqueous solution, and is usually 0.5 to 60% by weight.
Of solid content.

The polarizing plate of the present invention is manufactured by laminating the transparent protective film and the polarizer together using the adhesive. The adhesive may be applied to either the transparent protective film or the polarizer, or to both. After the bonding, a drying step is performed to form an adhesive layer composed of a coating and drying layer. The lamination of the polarizer and the transparent protective film can be performed with a roll laminator or the like.
The thickness of the adhesive layer is not particularly limited, but is usually 0.1 to 5
It is about μm.

In practical use, the polarizing plate of the present invention can be used as an optical film laminated with another optical layer.
The optical layer is not particularly limited, but for example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as 1/2 or 1/4), and a viewing angle compensation film. One or two or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate obtained by further laminating a reflective plate or a semi-transmissive reflective plate on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarized light obtained by further laminating a retardation plate on the polarizing plate. A wide-viewing-angle polarizing plate formed by laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate formed by laminating a brightness enhancement film on the polarizing plate is preferable.

The reflective polarizing plate is a polarizing plate provided with a reflective layer, and is for forming a liquid crystal display device of the type that reflects incident light from the viewing side (display side) to display. Further, there is an advantage that it is possible to omit the incorporation of a light source such as a backlight and to easily reduce the thickness of the liquid crystal display device. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like, if necessary.

As a specific example of the reflective polarizing plate, a transparent protective film matt-treated as necessary may be provided with a foil or a vapor deposition film made of a reflective metal such as aluminum to form a reflective layer. can give. Further, by incorporating fine particles into the transparent protective film to form a surface fine uneven structure,
There is also one having a reflective layer having a fine concavo-convex structure thereon. The reflective layer having the fine concavo-convex structure has the advantage that diffused incident light is diffused to prevent directivity and glare, and uneven brightness can be suppressed. In addition, the transparent protective film containing fine particles has an advantage that incident light and reflected light thereof are diffused when they pass therethrough to further suppress uneven brightness. The formation of the reflective layer having a fine concavo-convex structure reflecting the surface fine concavo-convex structure of the transparent protective film is performed by, for example, a vacuum deposition method, an ion plating method,
It can be performed by a method of directly attaching a metal to the surface of the transparent protective layer by an appropriate method such as a vapor deposition method such as a sputtering method or a plating method.

The reflection plate may be used as a reflection sheet or the like in which a reflection layer is provided on an appropriate film according to the transparent film, instead of the method of directly applying it to the transparent protective film of the polarizing plate. Since the reflective layer is usually made of a metal, the use state in which the reflective surface is covered with a transparent protective film, a polarizing plate, or the like prevents the reduction of the reflectance due to oxidation, and thus the initial reflectance is maintained for a long time. It is more preferable from the viewpoint of avoiding the additional provision of the protective layer.

The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light in the reflective layer. The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when the liquid crystal display device is used in a relatively bright atmosphere,
An image is displayed by reflecting incident light from the viewing side (display side), and in a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built into the back side of the semi-transmissive polarizing plate. It is possible to form a liquid crystal display device of the type that displays That is, the semi-transmissive polarizing plate can save energy for using a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device of a type that can be used with a built-in light source even in a relatively bright atmosphere. Is.

An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called ¼ wavelength plate (also called a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also called a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of a spurts twisted nematic (STN) type liquid crystal display device and is used for black and white display without the coloring. Used effectively. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed obliquely. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection. Specific examples of the above-mentioned retarder include polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate, and a birefringent film obtained by stretching a film made of a suitable polymer such as polyamide. And an alignment film of a liquid crystal polymer, a film in which an alignment layer of a liquid crystal polymer is supported by a film, and the like. The retardation plate may be one having an appropriate retardation according to the purpose of use, such as various wavelength plates or one for the purpose of compensating for the viewing angle and the like due to birefringence of the liquid crystal layer, and may be two or more kinds. It may be one in which retardation plates are laminated to control optical properties such as retardation.

The elliptically polarizing plate and the reflection type elliptically polarizing plate are obtained by laminating a polarizing plate or a reflection type polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can be formed by sequentially stacking them separately in the manufacturing process of a liquid crystal display device so as to form a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate is excellent in quality stability and stacking workability, and has an advantage that manufacturing efficiency of a liquid crystal display device can be improved.

The viewing angle compensation film is a film for widening the viewing angle so that the image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction, not perpendicular to the screen. Such a viewing angle compensating retardation plate includes, for example, a retardation film, an alignment film such as a liquid crystal polymer, or a transparent substrate on which an alignment layer such as a liquid crystal polymer is supported. A normal retardation film is a polymer film having birefringence that is uniaxially stretched in its plane direction, while a retardation plate used as a viewing angle compensation film is biaxially stretched in its plane direction. A polymer film having birefringence, a biaxially oriented film such as a polymer having birefringence in which the refractive index in the thickness direction is uniaxially stretched in the plane direction and also controlled in the thickness direction and the birefringence is controlled, Used. Examples of the obliquely oriented film include those obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to stretching treatment and / or shrinking treatment under the action of the shrinkage force caused by heating, and those obtained by obliquely orienting a liquid crystal polymer. Can be mentioned. The raw material polymer of the retardation plate is the same as the polymer explained in the previous retardation plate, which prevents coloration due to the change of the viewing angle due to the phase difference due to the liquid crystal cell and enlarges the viewing angle for good viewing. An appropriate one can be used for the purpose such as.

From the standpoint of achieving a wide viewing angle for good visibility, an optically anisotropic layer composed of a liquid crystal polymer alignment layer, particularly a discotic liquid crystal polymer tilt alignment layer, was supported by a triacetyl cellulose film. An optical compensation retardation plate can be preferably used.

A polarizing plate in which a polarizing plate and a brightness enhancement film are bonded together is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from the backlight of a liquid crystal display device or the back side, and transmits other light. The polarizing plate in which the brightness enhancement film and the polarizing plate are laminated, receives light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state and reflects light other than the predetermined polarization state without transmitting it. It The light reflected on the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the back side thereof and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in a predetermined polarization state to achieve brightness. The brightness can be improved by increasing the amount of light transmitted through the improvement film and by increasing the amount of light that can be used for liquid crystal display image display and the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is,
When light is incident from the back side of the liquid crystal cell through the polarizer without using the brightness enhancement film, almost all light with a polarization direction that does not match the polarization axis of the polarizer will enter the polarizer. It is absorbed and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for displaying the liquid crystal image is reduced accordingly, and the image becomes dark. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be first reflected by the brightness enhancement film without being incident on the polarizer and then inverted through a reflection layer or the like provided behind it. Repeatedly re-increasing the brightness to the plate, and reflecting between them,
The brightness enhancement film transmits only the polarized light in which the polarization direction of the inverted light is such that it can pass through the polarizer, and the polarizer absorbs the polarized light. It can be used to display an image on a display device and can brighten the screen.

The above-mentioned brightness enhancing film is, for example, a multilayer thin film of a dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies, transmits linearly polarized light of a predetermined polarization axis and reflects other light. Which exhibits the properties of, such as an alignment film of a cholesteric liquid crystal polymer or a film in which the alignment liquid crystal layer is supported on a film substrate, reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate materials such as those exhibiting characteristics can be used.

Therefore, in the brightness enhancement film of the type which transmits the linearly polarized light having the predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned, thereby suppressing the absorption loss by the polarizing plate. It can be efficiently transmitted. On the other hand, with a brightness enhancement film that drops circularly polarized light like a cholesteric liquid crystal layer, it is possible to make it enter the polarizer as it is, but from the viewpoint of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. By using a ¼ wavelength plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

The retardation plate functioning as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer functioning as a quarter-wave plate and another phase difference for a light color light having a wavelength of 550 nm. It can be obtained by a method of superposing a retardation layer exhibiting characteristics, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one layer or two or more retardation layers.

Regarding the cholesteric liquid crystal layer,
Two layers or three layers with different reflection wavelengths
By arranging the layers so as to overlap each other, it is possible to obtain an element that reflects circularly polarized light in a wide wavelength range such as a visible light region, and based on that, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-mentioned polarization separation type polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above reflective polarizing plate or semi-transmissive polarizing plate is combined with a retardation plate.

The optical film in which the optical layer is laminated on the polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. Has an advantage that it is excellent in quality stability and assembling work and can improve the manufacturing process of a liquid crystal display device or the like. Appropriate adhesion means such as an adhesive layer may be used for lamination. In adhering the above-mentioned polarizing plate and other optical films, the optical axes thereof can be set at an appropriate arrangement angle according to the intended retardation characteristics and the like.

At least one polarizing plate or at least one polarizing plate is used.
An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the optical film having the layers laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited, but for example, acrylic polymer, silicone polymer, polyester,
It is possible to appropriately select and use a polymer having a base polymer such as polyurethane, polyamide, polyether, or a polymer of fluorine type or rubber type. In particular, an acrylic pressure-sensitive adhesive, which has excellent optical transparency, exhibits appropriate wettability, cohesiveness and adhesiveness, and has excellent weather resistance and heat resistance, can be preferably used.

In addition to the above, prevention of foaming phenomenon and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cells, and further formation of a liquid crystal display device having high quality and excellent durability, etc. From this point of view, an adhesive layer having a low moisture absorption rate and excellent heat resistance is preferable.

The adhesive layer is made of, for example, natural or synthetic resins, in particular, tackifying resins, fillers, pigments, colorants, and oxidizers made of glass fibers, glass beads, metal powder, other inorganic powders and the like. It may contain an additive such as an inhibitor that is added to the adhesive layer. Further, it may be an adhesive layer containing fine particles and exhibiting light diffusion property.

The adhesive layer may be attached to one side or both sides of the polarizing plate or the optical film by an appropriate method. As an example thereof, a pressure-sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a single solvent or a mixture of appropriate solvents such as toluene and ethyl acetate is prepared, A method in which it is directly attached on the polarizing plate or the optical film by an appropriate developing method such as a casting method or a coating method, or an adhesive layer is formed on the separator according to the above and the adhesive layer is formed on the polarizing plate or the optical film. There is a method of transferring to the top.

The pressure-sensitive adhesive layer may be provided on one side or both sides of the polarizing plate or the optical film as a layer in which different compositions or types are laminated. Further, when it is provided on both surfaces, an adhesive layer having different composition, type and thickness may be provided on the front and back of the polarizing plate or the optical film. The thickness of the adhesive layer can be appropriately determined according to the purpose of use, adhesive strength, etc., and is generally 1 to
500 μm, preferably 5 to 200 μm, particularly 1
0 to 100 μm is preferable.

The exposed surface of the pressure-sensitive adhesive layer is temporarily covered with a separator for the purpose of preventing contamination and the like until it is put into practical use. As a result, it is possible to prevent contact with the adhesive layer in the usual handling state. As a separator,
Except for the above thickness conditions, for example, plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foamed sheet or metal foil, or an appropriate thin sheet such as a laminated body thereof may be used, if necessary, silicone type or long mirror alkyl type. It is possible to use an appropriate one according to the prior art, such as one coated with an appropriate release agent such as fluorine-based or molybdenum sulfide.

In the present invention, each layer such as a polarizer, a transparent protective film, an optical film, etc. forming the above-mentioned polarizing plate, and each layer such as an adhesive layer may be, for example, a salicylic acid ester compound, a benzophenol compound, a benzotriazole compound. Alternatively, it may be one having an ultraviolet absorbing ability by a method such as a method of treating with an ultraviolet absorber such as a cyanoacrylate compound or a nickel complex salt compound.

The polarizing plate or optical film of the present invention can be preferably used for forming various devices such as liquid crystal display devices. The liquid crystal display device can be formed in a conventional manner. That is, a liquid crystal display device is generally formed by appropriately raising components such as a liquid crystal cell, a polarizing plate or an optical film, and optionally an illumination system and incorporating a drive circuit. There is no particular limitation except that the polarizing plate or the optical film according to the present invention is used, and the conventional method can be applied. The liquid crystal cell may be of any type such as TN type, STN type, and π type.

It is possible to form an appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is arranged on one side or both sides of a liquid crystal cell or a liquid crystal display device using a backlight or a reflector in an illumination system. In that case, the polarizing plate or optical film according to the present invention can be installed on one side or both sides of the liquid crystal cell. When a polarizing plate or an optical film is provided on both sides, they may be the same or different. Further, when forming the liquid crystal display device, for example, a diffusion plate, an anti-glare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusion plate, a backlight, and other appropriate components are provided at appropriate positions in a single layer or Two or more layers can be arranged.

[0054]

EXAMPLES The present invention will be specifically described below with reference to Examples and Comparative Examples. In addition,% in each example is% by weight.

Example 1 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization: 2400, saponification degree: 99.9%) was placed in an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. After soaking at 60 ° C for 60 seconds for dyeing, and then stretching it up to 6 times while soaking in an aqueous boric acid solution having a boric acid concentration of 4% at 50 ° C for 60 seconds, potassium iodide concentration of 4% and zinc sulfate heptahydrate Concentration of 2. 5% in 30% at 8% aqueous solution
Soaked for 2 seconds. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. Both sides of the polarizer have a saponified thickness of 8
A 0 μm triacetyl cellulose film was attached with a polyvinyl alcohol-based adhesive and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

Example 2 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization: 2400, saponification degree: 99.9%) was placed in an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. After soaking at 60 ° C for 60 seconds for dyeing, and then stretching it up to 6 times while soaking in an aqueous boric acid solution having a boric acid concentration of 4% at 50 ° C for 60 seconds, potassium iodide concentration of 4% and zinc sulfate heptahydrate Was immersed in an aqueous solution of 4% concentration at 30 ° C. for 5 seconds. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. The thickness of both sides of the polarizer is 80μ, saponified.
The triacetyl cellulose film of m was adhered with a polyvinyl alcohol-based adhesive and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

Example 3 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization: 2400, saponification degree: 99.9%) was placed in an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. After soaking at 60 ° C for 60 seconds for dyeing, and then stretching it up to 6 times while soaking in an aqueous boric acid solution having a boric acid concentration of 4% at 50 ° C for 60 seconds, potassium iodide concentration of 4% and zinc sulfate heptahydrate 5% aqueous solution of 5% at 30 ℃
Soaked for 2 seconds. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. Both sides of the polarizer have a saponified thickness of 8
A 0 μm triacetyl cellulose film was attached with a polyvinyl alcohol-based adhesive and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

Example 4 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization: 2400, saponification degree: 99.9%) was added to an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. After dipping at 60 ° C for 60 seconds, dyeing, and then stretching up to 6 times while soaking in boric acid aqueous solution having a boric acid concentration of 4% at 50 ° C for 60 seconds, potassium iodide concentration of 7% and zinc sulfate heptahydrate Was immersed in an aqueous solution having a concentration of 7% at 30 ° C. for 5 seconds. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. The thickness of both sides of the polarizer is 80μ, saponified.
The triacetyl cellulose film of m was adhered with a polyvinyl alcohol-based adhesive and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

Comparative Example 1 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization: 2400, saponification degree: 99.9%) was placed in an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. Dip at 60 ° C for 60 seconds to dye it, then stretch it up to 6 times while soaking it in a boric acid aqueous solution with a boric acid concentration of 4% at 50 ° C for 60 seconds, and then dilute it with an aqueous solution of 4% potassium iodide at 30 ° C for 5 seconds Soaked. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. After laminating a triacetyl cellulose film having a thickness of 80 μm on the both sides of the polarizer with a polyvinyl alcohol-based adhesive, 6
A polarizing plate was obtained by drying at 0 ° C. for 4 minutes.

Comparative Example 2 A polyvinyl alcohol film having a thickness of 80 μm (average degree of polymerization 2400, saponification degree 99.9%) was added to an aqueous iodine solution having a potassium iodide concentration of 0.3% and an iodine concentration of 0.05%. After soaking at 60 ° C for 60 seconds for dyeing, and then stretching it up to 6 times while soaking in an aqueous boric acid solution having a boric acid concentration of 4% at 50 ° C for 60 seconds, potassium iodide concentration of 4% and zinc sulfate heptahydrate Was immersed in an aqueous solution having a concentration of 8% at 30 ° C. for 5 seconds. Then, it dried at 50 degreeC for 4 minutes, and obtained the polarizer. The thickness of both sides of the polarizer is 80μ, saponified.
The triacetyl cellulose film of m was adhered with a polyvinyl alcohol-based adhesive and then dried at 60 ° C. for 4 minutes to obtain a polarizing plate.

(Evaluation) Fluorescent X-ray analysis was performed on the polarizers prepared in the examples and comparative examples to measure the iodine content (%) and the zinc content (%). The value of zinc content (%) / iodine content (%) was determined from the measurement results. The results are shown in Table 1.
Shown in.

Further, a change Δab in orthogonal hue when the polarizing plate was left for 240 hours under the condition of 80 ° C. was obtained. The change Δab in the orthogonal hue is the initial orthogonal chromaticity (a ₀ , b ₀ ).
And the orthogonal chromaticity (a ₂₄₀ , b ₂₄₀ ) when left for 240 hours under the condition of 80 ° C., the formula: Δab = √
Is a value determined from ^{_{{(a 240 -a 0) 2}} + (a 240 -b 0) 2}. The a value and the b value are the a value and the b value in the Hunter color system. The results are shown in Table 1.

[0063]

[Table 1] From the examples and comparative examples, it can be seen that when the zinc content / iodine content is 0.05 to 0.6, the change Δab in the orthogonal hue during heating becomes 2 or less, and the hue change is small.

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[Procedure amendment]

[Submission date] May 28, 2002 (2002.5.2)
8)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] 0032

[Correction method] Change

[Correction content]

The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light in the reflective layer. The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when the liquid crystal display device is used in a relatively bright atmosphere,
An image is displayed by reflecting incident light from the viewing side (display side), and in a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built into the back side of the semi-transmissive polarizing plate. It is possible to form a liquid crystal display device of the type that displays That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0038

[Correction method] Change

[Correction content]

A polarizing plate in which a polarizing plate and a brightness enhancement film are bonded together is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light is incident due to reflection from the backlight of a liquid crystal display device or the back side, and transmits other light. The polarizing plate in which the brightness enhancement film and the polarizing plate are laminated, receives light from a light source such as a backlight to obtain transmitted light in a predetermined polarization state and reflects light other than the predetermined polarization state without transmitting it. It The light reflected on the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the back side thereof and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light in a predetermined polarization state to achieve brightness. The brightness can be improved by increasing the amount of light transmitted through the improvement film and by increasing the amount of light that can be used for liquid crystal display image display and the like by supplying polarized light that is difficult to be absorbed by the polarizer. That is,
When light is incident from the back side of the liquid crystal cell through the polarizer without using the brightness enhancement film, almost all light with a polarization direction that does not match the polarization axis of the polarizer will enter the polarizer. It is absorbed and does not pass through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display and the like is reduced accordingly, and the image becomes dark. The brightness enhancement film causes light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and then inverted through a reflection layer or the like provided behind it. The light-increasing film is made to pass only the polarized light whose polarization direction reflected and inverted between the two is such that it can pass through the polarizer. Since the light is supplied to the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI Theme Coat (reference) G02F 1/1335 510 G02F 1/1335 510 (72) Inventor Seiichi Kusumoto 1-1 1-1 Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Co., Ltd. (72) Inventor Naofumi Mihara 1-2 1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Ichimori Shoda 1-2-1, Shimohozumi, Ibaraki-shi, Osaka F-term (reference) within Nitto Denko Corporation 2H049 BA02 BA27 BB33 BB43 BB51 BC22 2H091 FA08X FA08Z FA21X FA21Z FA29X FA29Z FA37X FA37Z FA41Z FB02 HA07 HA10 KA10 LA01 4F071 DG47 BC0 AE47 BC0 AE07 BC02 AE02 BC0 AE02 A019A02 AE02 A029A01 AE02 A029A02 GF00 GP00

Claims (3)

[Claims] 1. A polarizer comprising a polyvinyl alcohol film dyed with iodine and containing zinc, wherein the value of zinc content (% by weight) / iodine content (% by weight) is 0.05 to 0.6. A polarizer characterized by being present. 2. A polarizing plate comprising a transparent protective layer provided on at least one surface of the polarizer according to claim 1. 3. A liquid crystal display device using at least one polarizing plate according to claim 2.