JP2002221618A - Polarizing plate and liquid crystal display device using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate with optical characteristics more excellent than the conventional one and a liquid crystal display device using the same with excellent display characteristics. SOLUTION: In the polarizing plate constructed by sticking a polarizer formed by dying, cross-linking, stretching and drying a synthetic resin film to a protective film, the polarizing plate has <=3 standard deviation of parallel transmittance measured in increments of 10 nm in 420-700 nm light wavelength region and further has >=300 minimum value of a ratio (parallel transmittance/vertical transmittance) measured in increments of 10 nm in 420-700 nm light wavelength region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate used in a liquid crystal display device (hereinafter, may be abbreviated as LCD) and a liquid crystal display device using the same.

[0002]

2. Description of the Related Art LCDs are used in personal computers and the like, and the demand for LCDs has been rapidly increasing in recent years. The use of LCDs is expanding, and in recent years, LCDs are also being used for monitors.

A polarizing plate used for an LCD is, for example, a dyeing step of dyeing a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film with iodine or a dichroic dye having dichroism. After a cross-linking step of cross-linking with borax or the like and a stretching step of uniaxial stretching, the film is dried to form a polarizer.
It may be abbreviated as TAC. ) It is manufactured by bonding a protective layer such as a film. The steps of dyeing, crosslinking, and stretching do not need to be performed separately, and may be performed simultaneously, and the order of the steps may be arbitrary.

[0004]

In recent years, as described above, LC
As D is used for various purposes, LCDs are required to have higher display characteristics than before. The optical characteristics of the polarizing plate used for the LCD greatly affect the display characteristics of the LCD.

[0005] However, there has been a problem that the conventional polarizing plate cannot always sufficiently satisfy the above requirements. That is, conventionally, when the hue when the polarization axes of the two polarizing plates are made parallel is neutral, the hue when the polarization axes of the two polarizing plates are made orthogonal becomes blue, and conversely, the hue when the polarization axes become orthogonal is changed. When the neutral state is set, there is a problem that the hue at the time of parallel becomes yellow. For this reason, if the display color when a white screen is displayed on a normally white LCD using this polarizing plate is set to neutral, the blue light is not cut off in the black screen display portion, and the contrast is reduced. If the display color at the time of performing the black screen display is made neutral, there is a problem that the white screen display portion is colored yellow.

As described above, conventionally, there has been a problem that the display color of the white screen display of the LCD cannot be made neutral and high contrast cannot be obtained.

Therefore, an object of the present invention is to provide a polarizing plate having more excellent optical characteristics and a liquid crystal display device having excellent display characteristics using the same in order to solve the above-mentioned conventional problems.

[0008]

Means for Solving the Problems To achieve the above object, a polarizing plate of the present invention is constituted by laminating a protective film with a polarizer formed by dyeing, crosslinking, stretching and drying a synthetic resin film. In the polarizing plate, the wavelength of light is 420 to
The standard deviation of the parallel transmittance at every 10 nm between 700 nm is 3 or less, and the minimum value of (parallel transmittance / orthogonal transmittance) at every 10 nm between light wavelengths of 420 to 700 nm is 300 or more. It is characterized by being.

When the wavelength of light is 420 to 700 nm,
By setting the standard deviation of the parallel transmittance for every 0 nm to 3 or less, the transmittance for each wavelength becomes uniform, and the display color when white screen display is performed on the liquid crystal display device becomes neutral. If the standard deviation exceeds 3, the transmittance of each wavelength will not be uniform, and the white screen display will be colored. Where 4
When the wavelength is less than 20 nm, the light is absorbed when the ultraviolet absorbent is used, so that the transmittance is reduced. In addition, light having a wavelength exceeding 700 nm is not a problem because it cannot be seen visually.

Further, by setting the minimum value of (parallel transmittance / orthogonal transmittance) for each 10 nm between light wavelengths of 420 to 700 nm to 300 or more, a liquid crystal display device having excellent contrast can be obtained. it can. When the value of (parallel transmittance / orthogonal transmittance) is less than 300 in all wavelength ranges, sufficient contrast cannot be obtained, and only the value of (parallel transmittance / orthogonal transmittance) in a specific wavelength range is reduced. If it exceeds 300, the black screen display section will be colored.

In the polarizing plate of the present invention, the synthetic resin film is preferably a polyvinyl alcohol film, and the protective film is preferably a triacetyl cellulose film.

Further, it is preferable to provide an adhesive layer on the polarizing plate of the present invention.

The polarizing plate of the present invention is preferably provided with an anti-glare layer.

It is preferable that a reflector or a semi-transmissive reflector is attached to the polarizing plate of the present invention.

Preferably, a retardation plate or a λ plate is attached to the polarizing plate of the present invention.

Further, it is preferable to attach a viewing angle compensation film to the polarizing plate of the present invention.

It is preferable that a brightness enhancement film is attached to the polarizing plate of the present invention.

Next, a liquid crystal display device according to the present invention is characterized in that the polarizing plate is used on at least one side of a liquid crystal cell.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate used in the present invention is a polarizing film which is obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching, and having a light wavelength of 420 to 700 n.
By setting the standard deviation of the parallel transmittance every 10 nm between m to 3 or less, the transmittance at each wavelength becomes uniform, becomes neutral when the liquid crystal display device is displayed on a white screen, and the light wavelength is 420 to By setting the minimum value of (parallel transmittance / orthogonal transmittance) for each 10 nm between 700 nm to 300 or more, a liquid crystal display device with excellent contrast can be obtained.

The polarizing plate of the present invention comprises a polarizing film which is obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching, dyeing the polyvinyl alcohol by immersing it in an aqueous solution of iodine, and stretching it to 3 to 7 times its original length. Can be produced. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. If necessary, the polyvinyl alcohol film may be immersed in water and washed with water before dyeing. Washing the polyvinyl alcohol film with water not only removes stains on the surface of the polyvinyl alcohol film and the antiblocking agent, but also has an effect of preventing unevenness such as uneven dyeing by swelling the polyvinyl alcohol film.

The stretching may be performed after dyeing with iodine, or may be performed while dyeing. Stretching can be performed in an aqueous solution of boric acid or potassium iodide or in a water bath. If the stretching is not performed in a water bath, the polyvinyl alcohol swells, causing wrinkles or breakage.

The thickness of the polarizing film is usually 5 to 80 μm, but is not limited to this. The polarizing plate may be a polarizing film itself or a polarizing film provided with a transparent protective layer on one or both sides of the polarizing film. The transparent protective layer can be formed by an appropriate method such as a film laminating method or a coating method, and an appropriate transparent resin or the like can be used for the formation.

Preferred transparent protective layers are excellent in transparency, mechanical strength, heat stability, moisture shielding property, isotropy and the like. Examples thereof include plastics such as polyolefins, polyesters, polycarbonates, polyamides, polyimides, polyethersulfones, polysulfones, polystyrenes, acrylic resins and acetate resins, acrylics and urethanes, acrylic urethanes and epoxies, and silicones. Heat-curable or ultraviolet-curable resins. The thickness of the protective layer is generally 500 μm
Hereinafter, the thickness is preferably 1 to 300 μm, particularly preferably 5 to 200 μm.

A transparent protective film that can be particularly preferably used in view of polarization characteristics and durability is a triacetyl cellulose film whose surface is saponified with an alkali or the like. When transparent protective films are provided on both sides of the polarizing film, transparent protective films made of the same polymer or the like may be used on the front and back sides, or transparent protective films made of different polymers or the like may be used.

The transparent protective film used for the protective layer is
As long as the object of the present invention is not impaired, a hard coat layer, an antireflection treatment, a treatment for sticking prevention, diffusion or antiglare may be performed. The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate, and for example, a cured film having an excellent hardness and a sliding property by an appropriate ultraviolet curable resin such as an acrylic resin or a silicone resin is applied to a transparent protective film. It can be formed by a method of adding to the surface of.

On the other hand, the anti-reflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an anti-reflection film or the like according to the related art. In addition, anti-sticking is performed for the purpose of preventing adhesion to an adjacent layer, and anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and obstructing the visibility of light transmitted through the polarizing plate. For example, the transparent protective film can be formed by giving a fine uneven structure to the surface of the transparent protective film by an appropriate method such as a roughening method by a sand blast method or an embossing method or a method of blending transparent fine particles.

The fine particles to be contained in the formation of the transparent protective layer having the above-mentioned fine surface unevenness structure are, for example, those having an average particle size of 0.1.
Transparent inorganic fine particles of 5 to 50 μm such as silica, alumina, titania and zirconia, tin oxide and indium oxide, cadmium oxide and antimony oxide, and organic fine particles of a crosslinked or uncrosslinked polymer. Fine particles are used. The amount of the fine particles to be used is generally 2 to 50 parts by mass, preferably 5 to 25 parts by mass, per 100 parts by mass of the transparent resin.

The antiglare layer containing the transparent fine particles can be provided as the transparent protective layer itself or as a coating layer on the surface of the transparent protective layer. The anti-glare layer is a diffusion layer that diffuses the light transmitted through the polarizing plate to increase the viewing angle
(Such as a viewing angle enlargement function). The above-described anti-reflection layer, anti-sticking layer, diffusion layer, anti-glare layer and the like can be provided as an optical layer made of a sheet or the like provided with such a layer, separately from the transparent protective layer.

The bonding treatment between the polarizer (polarizing film) and the transparent protective film as the protective layer is not particularly limited. For example, an adhesive composed of a vinyl alcohol polymer, boric acid or boric acid may be used. It can be carried out via an adhesive comprising at least a water-soluble crosslinking agent of a vinyl alcohol-based polymer such as sand, glutaraldehyde, melamine, and oxalic acid. Such an adhesive layer can be formed as a coating and drying layer of an aqueous solution, for example, and when the aqueous solution is adjusted, other additives and a catalyst such as an acid can be blended as necessary.

The polarizing film of the present invention can be used as an optical member laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including a wavelength plate such as 波長 or ４), or a viewing angle compensation film is formed. One or two suitable optical layers that may be used
Layer or more, in particular, a polarizing plate comprising the polarizer and the protective layer of the present invention described above, a reflective polarizing plate or a semi-transmissive polarizing plate further laminated with a reflecting plate or a semi-transmissive reflecting plate, The above-mentioned polarizer and a polarizing plate comprising a protective layer, an elliptically polarizing plate or a circularly polarizing plate obtained by further laminating a retardation plate, the above-described polarizer comprising a polarizer and a protective layer, further a viewing angle compensation film is laminated. A wide viewing angle polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the above-described polarizing plate comprising a polarizer and a protective layer is preferable.

The reflection type polarizing plate is provided with a reflecting layer on the polarizing plate, and is used for forming a liquid crystal display device of a type which reflects incident light from the viewing side (display side) to display. In addition, there is an advantage that the light source such as a backlight can be omitted and the liquid crystal display device can be easily made thinner.

The reflection type polarizing plate can be formed by an appropriate method such as a method in which a reflection layer made of metal or the like is provided on one side of the polarizing plate via a transparent protective layer or the like, if necessary.

Specific examples of the reflective polarizing plate include a transparent protective layer, which is matted as necessary, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum to one surface of the transparent protective layer. Is mentioned. Further, there may be mentioned a transparent protective layer containing fine particles to form a fine surface unevenness structure, and a reflective layer having a fine unevenness structure formed thereon. The reflective layer having the fine uneven structure described above has an advantage that the incident light can be diffused by diffuse reflection to prevent directivity and glare, and that unevenness in brightness can be suppressed. Also,
The transparent protective layer containing fine particles also has an advantage that the incident light and the reflected light thereof are diffused when transmitting the light and the unevenness of brightness and darkness can be further suppressed. The reflective layer having a fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective layer is formed by, for example, making the metal transparent by an appropriate method such as an evaporation method such as a vacuum evaporation method, an ion plating method, or a sputtering method, or a plating method. It can be carried out by a method of directly attaching to the surface of the protective layer.

The reflection plate can be used as a reflection sheet in which a reflection layer is provided on an appropriate film corresponding to the transparent film, instead of the method of directly applying the reflection film to the transparent protective film of the polarizing plate. In addition, the reflective layer is usually
Since it is made of metal, its reflective surface is coated with a transparent protective layer or a polarizing plate to prevent reduction in reflectance due to oxidation, and thus to maintain the initial reflectance for a long period of time. Is more preferable.

The transflective polarizing plate can be obtained by forming a transflective reflective layer such as a half mirror that reflects and transmits light with the reflective layer. The transflective polarizing plate is usually provided on the back side of the liquid crystal cell, and when a liquid crystal display device or the like is used in a relatively bright atmosphere,
An image is displayed by reflecting the incident light from the viewing side (display side), and in a relatively dark atmosphere, the image is displayed using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. A liquid crystal display device or the like of a type that displays the same can be formed. That is, the transflective 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 dark atmosphere. is there.

An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the above-mentioned polarizing plate comprising a polarizer and a protective layer will be described.

When changing linearly polarized light to elliptically or circularly polarized light, or changing elliptically or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light, a retardation plate or the like is used. A so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes the light into circularly polarized light or changes the circularly polarized light into linearly polarized light. 1/2 wave plate
(Also referred to as a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

An elliptically polarizing plate compensates (prevents) coloring (blue or yellow) caused by birefringence of a liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device to perform black-and-white display without the coloring. It is used effectively for such purposes. Furthermore, 3
It is preferable to control the dimensional refractive index because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflection type liquid crystal display device for displaying an image in color, and also has an antireflection function.

As a specific example of the above-mentioned retardation plate, a multilayer film obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate, or polyamide is used. Examples thereof include a refractive film, an alignment film of a liquid crystal polymer, and an alignment layer of a liquid crystal polymer supported by a film. The retardation plate may have an appropriate retardation in accordance with the intended use, such as, for example, various wavelength plates or those for the purpose of compensating a viewing angle or the like due to birefringence of the liquid crystal layer,
One in which two or more retardation plates are laminated to control optical characteristics such as retardation may be used.

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 elliptically polarizing plates and the like,
(Reflection type) It can also be formed by sequentially and separately laminating them in the manufacturing process of the liquid crystal display device so as to be a combination of a polarizing plate and a retardation plate. The liquid crystal display has excellent advantages in quality stability, laminating workability, and the like, and can improve manufacturing efficiency of a liquid crystal display device and the like.

The viewing angle compensating 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 direction not perpendicular to the screen but slightly oblique.

Such a viewing angle compensating retardation plate includes, for example, a retardation film, an alignment film such as a liquid crystal polymer, and a transparent substrate on which an alignment layer such as a liquid crystal polymer is supported. A normal retardation plate is a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film is biaxially stretched in the plane direction. Polymer films having birefringence, or bidirectionally stretched films such as birefringent polymers or obliquely oriented films, which are uniaxially stretched in the plane direction and are also stretched in the thickness direction and have a controlled refractive index in the thickness direction. Used. Examples of the obliquely oriented film include a film obtained by bonding a heat shrinkable film to a polymer film and subjecting the polymer film to a stretching treatment and / or a shrinkage treatment under the action of the shrinkage force caused by heating, or a film obtained by obliquely orienting a liquid crystal polymer. No. As the raw material polymer of the retardation plate, the same polymer as that described in the above retardation plate is used. Prevention of coloring due to a change in the viewing angle based on the phase difference by the liquid crystal cell and expansion of the viewing angle for good visibility. Any suitable one for the purpose can be used.

Further, in order to achieve a wide viewing angle with good visibility, it was supported by an acetylcellulose film having an alignment layer of a liquid crystal polymer, particularly an optically anisotropic layer composed of an inclined alignment layer of a discotic liquid crystal polymer. An optical compensation retardation plate can be preferably used.

A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film reflects linearly polarized light having a predetermined polarization axis or circularly polarized light having a predetermined direction when natural light is incident due to reflection from a backlight or a back side of a liquid crystal display device, and has a property of transmitting other light. A polarizing plate obtained by laminating a brightness enhancement film with a polarizing plate comprising the above-described polarizer and a protective layer, while allowing light from a light source such as a backlight to enter to obtain transmitted light of a predetermined polarization state and the predetermined polarization state. Other light is reflected without transmitting. The light reflected on the surface of the brightness enhancement film is further inverted through a reflection layer or the like provided on the rear side thereof and re-entered on the brightness enhancement film, and a part or all of the light is transmitted as light of a predetermined polarization state to achieve brightness. In addition to increasing the amount of light transmitted through the enhancement film, it is also possible to increase the amount of light that can be used for liquid crystal display and image display by supplying polarized light that is hardly absorbed by the polarizer, thereby improving the luminance. That is, when light is incident from the back side of the liquid crystal cell through a polarizer with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not match the polarization axis of the polarizer is almost polarized. Is absorbed by the polarizer and does not pass through the polarizer. For this reason, although it depends on the characteristics of the polarizer used, about 5
0% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for liquid crystal image display and the like is reduced, and the image becomes darker.
The brightness enhancement film is such that light having a polarization direction that is absorbed by the polarizer is once reflected by the brightness enhancement film without being incident on the polarizer, and further inverted through a reflection layer or the like provided on the rear side thereof. The brightness enhancement film transmits only the polarized light whose polarization direction is such that the polarization direction of the light reflected and inverted between the two can pass through the polarizer. Since the light is absorbed by 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.

As the above-mentioned brightness improving film, linearly polarized light having a predetermined polarization axis is transmitted and other light is reflected, such as a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropy. Such as a cholesteric liquid crystal layer, particularly 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, reflecting either left-handed or right-handed circularly polarized light, Any suitable light such as a light-transmitting light may be used.

Therefore, in the brightness enhancement film of the type that transmits the linearly polarized light having the predetermined polarization axis, the transmitted light is directly incident on the polarization plate with the polarization axis aligned, thereby suppressing absorption loss by the polarization plate. It can be transmitted efficiently. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light, such as a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the point of suppressing absorption loss, the circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on a polarizing plate. By using a quarter-wave plate as the retardation plate, circularly polarized light can be converted to linearly polarized light.

A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light having a wavelength of 550 nm and another retardation layer. It can be obtained by a method of superimposing 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 or more retardation layers.

Incidentally, the cholesteric liquid crystal layer also
Two layers or three layers in combination with different reflection wavelengths
By adopting an arrangement structure in which layers are superimposed, it is possible to obtain circularly polarized light in a wide wavelength range such as a visible light region, and to obtain transmitted circularly polarized light in a wide wavelength range based on the reflected light.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers as in the above-mentioned polarized light separating type polarizing plate. Therefore, a reflective elliptically polarizing plate or a transflective elliptically polarizing plate obtained by combining the above-mentioned reflective polarizing plate, transflective polarizing plate and retardation plate may be used. An optical member in which two or three or more optical layers are laminated,
Although it can be formed by a method of sequentially laminating in the manufacturing process of a liquid crystal display device or the like, an optical member preliminarily laminated is excellent in quality stability and assembly work, etc. There is an advantage that a manufacturing process of a device or the like can be improved.
Appropriate bonding means such as an adhesive layer can be used for lamination. When bonding the above-mentioned polarizing plate and other optical members, their optical axes can be arranged at an appropriate angle in accordance with the intended retardation characteristics.

The above-mentioned polarizing plate or optical member may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. For the formation thereof, it is possible to use an adhesive substance or an adhesive having an appropriate polymer such as an acrylic polymer or a silicone polymer, a polyester or a polyurethane, a polyamide or a polyether, or a suitable polymer such as a fluorine or a rubber as a base polymer. There is no particular limitation. Above all, those having excellent optical transparency such as an acrylic adhesive, exhibiting appropriate wettability, cohesiveness and adhesive properties such as adhesiveness, and having excellent weather resistance and heat resistance can be preferably used.

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

For the adhesive layer, for example, fillers, pigments, colorants, and the like made of natural or synthetic resins, particularly, tackifying resins, glass fibers and glass beads, metal powders and other inorganic powders, and the like. It may contain an appropriate additive such as an antioxidant which may be added to the adhesive layer. Further, an adhesive layer containing fine particles and exhibiting light diffusibility may be used.

The attachment of the adhesive layer to one or both sides of the polarizing plate or the optical member can be performed by an appropriate method. As an example, for example, an adhesive substance or a composition thereof is dissolved or dispersed in a solvent consisting of a proper solvent alone or a mixture such as toluene or ethyl acetate to prepare an adhesive liquid of about 10 to 40% by mass. Then, it is directly applied to the optical member by an appropriate developing method such as a casting method or a coating method, or a method of forming an adhesive layer on a separator according to the above and transferring it to the optical member. And the like.

The adhesive layer may be provided on one or both sides of a polarizing plate or an optical member as a superposed layer of different compositions or types. When the optical member is provided on both sides, it is also possible to form an adhesive layer having a different composition, type and thickness on the front and back of the optical member. The thickness of the pressure-sensitive adhesive layer can be appropriately determined depending on the purpose of use, adhesive strength, and the like, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly 10 to 100 μm.

A separator is temporarily attached to the exposed surface of the pressure-sensitive adhesive layer for the purpose of preventing contamination and the like until it is practically used, and is covered. Thus, it is possible to prevent the adhesive layer from coming into contact with the adhesive layer in a normal handling state.

Except for the above thickness conditions, a suitable thin leaf such as a plastic film or rubber sheet, paper or cloth, non-woven fabric or net, foamed sheet or metal foil, or a laminate thereof may be used as necessary. Appropriate conventional materials, such as those coated with an appropriate release agent such as silicone, long-chain alkyl, fluorine, or molybdenum sulfide, can be used.

In the present invention, each layer such as a polarizing film, a transparent protective layer and the like, which forms the above-mentioned polarizing plate and optical member, and a layer such as an adhesive layer may be made of, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound or the like. A material having ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorber such as a cyanoacrylate compound or a nickel complex compound may be used.

The polarizing plate can be preferably used for forming various devices such as a liquid crystal display device. The formation of the liquid crystal display device can be performed according to the related art. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate, an optical compensation retardation plate, and an illumination system as needed, and incorporating a drive circuit,
In the present invention, there is no particular limitation except that the polarizing plate according to the present invention is used, and it can be in accordance with the conventional one. As for the liquid crystal cell, any type such as TN type, STN type and π type can be used.

Appropriate liquid crystal display devices such as a liquid crystal display device in which a polarizing plate is arranged on one or both sides of a liquid crystal cell, and a lighting system using a backlight or a reflector can be formed. In that case, the polarizing plate according to the present invention can be installed on one side or both sides of the liquid crystal cell. When polarizing plates and optical members are provided on both sides, they may be the same or different. Further, in forming the liquid crystal display device, for example, a suitable component such as a diffusion plate or an anti-glare layer, an antireflection film or a protection plate, a prism array or a lens array sheet, a light diffusion plate or a backlight is placed in one layer or at an appropriate position. Two or more layers can be arranged.

[0060]

The present invention will be described more specifically below with reference to examples and comparative examples.

Example A non-stretched PVA film having a degree of polymerization of 2400, a raw material thickness of 80 μm and a raw material width of 800 mm as a synthetic resin film was dyed in a 0.3% by mass aqueous solution of iodine. Stretched 6.8 times in an aqueous solution of 3% by mass of boric acid and 3% by mass of potassium iodide.
After drying at 4 ° C. for 4 minutes, the film was wound as a polarizer.

Next, an adhesive consisting of a 7% by mass aqueous solution of polyvinyl alcohol was applied to both surfaces of the polarizer, and the two polarizers were laminated as protective films so as to sandwich the polarizer at 60 ° C. After drying for 4 minutes, a polarizing plate was obtained. The thickness of this TAC film is 80 μm.
The TAC film has an ultraviolet absorber, "Tinuvin 32" manufactured by Ciba Specialty Chemicals Co., Ltd.
6 "and" Tinuvin 328 ".

Comparative Example 1 As a synthetic resin film, the degree of polymerization was 2400, the thickness of the raw material was 80 μm, and the width of the raw material was 800 mm.
The unstretched PVA film was dyed in an aqueous solution of 0.3% by mass of iodine, and then stretched 5.4 times in an aqueous solution of 4% by mass of boric acid and 2% by mass of potassium iodide.
After drying at 0 ° C. for 4 minutes, the film was wound as a polarizer.

Next, an adhesive composed of a 7% by mass aqueous solution of polyvinyl alcohol was applied to both surfaces of the polarizer, and the two polarizers were laminated as protective films by sandwiching the polarizer between two TAC films. After drying for 4 minutes, a polarizing plate was obtained. The thickness of this TAC film is 80 μm.
m, and the TAC film contains the above-mentioned tinuvin 326 and tinuvin 328 as an ultraviolet absorber.

Comparative Example 2 As a synthetic resin film, the degree of polymerization was 2400, the thickness of the raw material was 80 μm, the width of the raw material was 800 mm,
The unstretched PVA film is dyed in an aqueous solution of 0.3% by mass of iodine, and then stretched 5.4 times in an aqueous solution of 4% by mass of boric acid and 4% by mass of potassium iodide.
After drying at 0 ° C. for 4 minutes, the film was wound as a polarizer.

Next, an adhesive composed of a 7% by mass aqueous solution of polyvinyl alcohol was applied to both sides of the polarizer, and the two polarizers were laminated as protective films so as to sandwich the polarizer at 80 ° C. After drying for 4 minutes, a polarizing plate was obtained. The thickness of this TAC film is 80 μm.
m, and the TAC film contains the above-mentioned tinuvin 326 and tinuvin 328 as an ultraviolet absorber.

(Evaluation) Using the spectrophotometer, the polarizing plates obtained in the examples, comparative examples 1 and 2 were used to adjust the light wavelength to 38.
The single transmittance, parallel transmittance and orthogonal transmittance at every 10 nm between 0 and 700 nm were measured, and the standard deviation of the parallel transmittance at each wavelength and the (parallel transmittance / orthogonal transmittance) of each wavelength were measured. The minimum was determined from the values.

FIGS. 1, 2 and 3 show the spectra of the polarizing plates produced in the examples, comparative examples 1 and 2, respectively. Table 1 shows that the wavelength of light is 420 to 700.
The standard deviation of parallel transmittance every 10 nm between nm and the minimum value of (parallel transmittance / cross transmittance) are shown.

[0069]

[Table 1]

Next, each of the polarizing plates produced in Example, Comparative Example 1 and Comparative Example 2 was replaced with a thin film transistor (TFT).
Brightness on a white screen display and CIE using a luminance meter “BM-5A” manufactured by Topcon Co., Ltd.
1931 The chromaticity coordinates of the color system were measured. Further, the luminance of the black screen display was measured, and the contrast was calculated from (the luminance of the white screen display / the luminance of the black screen display). Table 2 shows the results.

[0071]

[Table 2]

As is apparent from Tables 1 and 2, when the standard deviation of the parallel transmittance is 3 or less, the hue of the white screen display of the liquid crystal display device is neutral. The minimum value of (parallel transmittance / orthogonal transmittance) is 30.
When it is 0 or more, it is understood that the contrast is high.

As a result, the wavelength of light is 420 to 700 n
By setting the standard deviation of the parallel transmittance for every 10 nm between m and m to be 3 or less, the white screen display becomes neutral, and the light wavelength between 420 nm and 700 nm for every 10 nm (parallel transmittance / perpendicular). By setting the minimum value of (transmittance) to 300 or more, a liquid crystal display device having excellent contrast can be obtained.

[0074]

As described above, according to the present invention, the standard deviation of the parallel transmittance at every 10 nm between light wavelengths of 420 to 700 nm is 3 or less, and the minimum value of (parallel transmittance / orthogonal transmittance). Is 300 or more, it is possible to provide a polarizing plate having more excellent optical characteristics and a liquid crystal display device having excellent display characteristics using the polarizing plate, and its industrial value is great.

[Brief description of the drawings]

FIG. 1 is a diagram showing a spectrum of a polarizing plate manufactured in an example.

FIG. 2 is a diagram showing a spectrum of a polarizing plate manufactured in Comparative Example 1.

FIG. 3 is a view showing a spectrum of a polarizing plate manufactured in Comparative Example 2.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/00 313 G09F 9/00 313 324 324 (72) Inventor Seiichi Kusumoto 1-chome Shimohozumi, Ibaraki-shi, Osaka 1-2-2 Nitto Denko Corporation (72) Inventor Yoichiro Sugino 1-2-1, Shimohozumi, Ibaraki-shi, Osaka F-term in Nitto Denko Corporation (reference) 2H042 BA02 BA03 BA20 2H049 BA02 BA03 BA04 BA06 BA07 BA27 BA42 BA43 BB03 BB33 BB43 BB51 BB52 BB61 BB63 BB65 BC03 BC22 2H091 FA08X FA08Z FA11X FA11Z GA16 5G435 AA00 BB12 BB15 BB16 FF01 FF03 FF05 GG09 HH03 KK07

Claims (9)

[Claims] Claims: 1. A synthetic resin film is dyed, cross-linked, stretched,
In a polarizing plate formed by bonding a polarizer formed by drying and a protective film, the wavelength of light is 420 to 70.
The standard deviation of the parallel transmittance every 10 nm between 0 nm is 3
And the minimum value of (parallel transmittance / orthogonal transmittance) for every 10 nm when the light wavelength is between 420 and 700 nm is 3
A polarizing plate having a thickness of at least 00. 2. The polarizing plate according to claim 1, wherein the synthetic resin film is a polyvinyl alcohol film, and the protective film is a triacetyl cellulose film. 3. A polarizing plate comprising the polarizing plate according to claim 1 and an adhesive layer. 4. A polarizing plate comprising the polarizing plate according to claim 1 and an anti-glare layer. 5. A polarizing plate comprising the polarizing plate according to claim 1 and a reflecting plate or a transflective plate. 6. A polarizing plate comprising the polarizing plate according to claim 1 and a retardation plate or a λ plate attached to the polarizing plate. 7. A polarizing plate comprising the polarizing plate according to claim 1 and a viewing angle compensation film bonded thereto. 8. A polarizing plate comprising the polarizing plate according to claim 1 and a brightness enhancement film bonded thereto. 9. The method according to claim 1, wherein at least one side of the liquid crystal cell is provided.
A liquid crystal display device comprising the polarizing plate according to any one of Items 1 to 8.