KR100763113B1 - Method for manufacturing polarization plate and liquid crystal display device having the polarization plate - Google Patents

Abstract

Provided are a liquid crystal display device comprising a polarizing plate having a high transmittance and high polarization characteristic and a polarizing plate obtained by this method.

In a method of manufacturing a polarizing plate by dyeing a polyvinyl alcohol (PVA) film with a dye solution containing iodine having a dichroic property, crosslinking with a crosslinking agent, and stretching using at least one pair of rolls in the above process, The bath containing the said crosslinking agent is provided 2 times or more, and the draw ratio of the 1st bath is 1 to 4 times, and the draw ratio after the 2nd bath is extended | stretched by elongation higher than the draw ratio of the said 1st bath.

Description

Method for manufacturing polarization plate and liquid crystal display device having the polarization plate

The present invention relates to a method for producing a polarizing plate for use in a liquid crystal display device (hereinafter sometimes abbreviated as LCD) and a liquid crystal display device having a polarizing plate obtained thereby. More specifically, the present invention relates to a method for manufacturing a polarizing plate having characteristics of high transmittance and high polarization and a liquid crystal display device having the same.

LCDs are used in personal computers and the like, and are rapidly increasing in recent years. The use of LCD is diversified, and it is also recently used for a monitor use.

In a polarizing plate used for a display device such as an LCD, when the transmittance is low, the degree of polarization increases, but the amount of light transmitted decreases, and the display becomes dark. On the contrary, when transmittance | permeability becomes high, there exists a problem that a polarization degree falls and contrast deteriorates.

Patent No. 2512408 proposes a method in which the draw ratio of the first bath is higher than the draw ratio of the second bath in the definition of the draw ratio of the first and second baths to be crosslinked.                         

However, even in the above method, it was difficult to obtain a polarizing plate having high transmittance and high polarization characteristics.

An object of the present invention is to provide a method for producing a polarizing plate having high transmittance and high polarization characteristics and a liquid crystal display device having the polarizing plate obtained by this method in order to solve the above conventional problems.

In order to achieve the above object, the manufacturing method of the polarizing plate of the present invention, at least one pair in the process, at the same time by dyeing a polyvinyl alcohol (PVA) film with a dye solution containing iodine having a dichroic property and crosslinking with a crosslinking agent In the method of extending | stretching using the roll of and manufacturing the polarizing plate, the bath containing the said crosslinking agent is installed 2 times or more, and the draw ratio of the 1st bath is 1 times or more and 4 times or less, and the draw ratio of 2 times or less is It extends | stretches by elongation higher than the said draw ratio of the said 1st bath, It is characterized by the above-mentioned.

In the said method, it is preferable that at least 1 bath temperature after the 2nd bath is higher than the temperature of the 1st bath in which the crosslinking agent was put, 5 degreeC or more higher than the crosslinking bath temperature of the 1st bath.

In the said method, it is preferable that the temperature of the 1st bath containing a crosslinking agent is 10 degreeC or more and 90 degrees C or less.

In the said method, it is preferable that the draw ratio of the PVA film in the dye bath containing the dyeing solution is 5 times or less.

In the said method, it is preferable that the temperature of the dyeing bath which put the dyeing solution is 15 degreeC or more and 50 degrees C or less.

Moreover, it is preferable to form a reflective polarizing plate or a semi-transmissive reflecting plate type polarizing plate by bonding a reflecting plate or a semi-transmissive reflecting plate to the polarizing plate manufactured by the said method.

Moreover, it is preferable to form an ellipse or a circular polarizing plate by bonding a retardation plate or (lambda) plate to the polarizing plate manufactured by the said method.

Moreover, it is preferable to bond a visual compensation film to the polarizing plate manufactured by the said method, and to form a polarizing plate.

Moreover, it is preferable to bond a brightness improving film to an polarizing plate manufactured by the said method, using an adhesive agent or an adhesive, and to form a polarizing plate.

Next, the liquid crystal display device of the present invention is characterized in that the polarizing plate produced by the above method is provided on at least one side of the liquid crystal cell.

The manufacturing method of a polarizing film generally crosslinks in a bath containing the crosslinking agent of PVA, such as a boric acid and borax, and the "dyeing process" which dyes a PVA film in the bath containing the dichromatic characteristic iodine or dye. Crosslinking step ”and three steps of“ drawing step ”for stretching PVA. In addition, a "stretching process" is usually performed simultaneously with a "dyeing process" and a "crosslinking process", but may be performed by another process. Moreover, a dyeing process and a crosslinking process may also be performed simultaneously. The polarizing film is manufactured by bonding to one or both of a film such as a triacetyl cellulose (TAC) film or a polyethylene terephthalate (PET) film, which is dried to form a protective layer after the three steps.                     

In this process of the dyeing, crosslinking and stretching, the bath containing the crosslinking agent is provided at least two baths, and the stretching ratio of the first bath is drawn at one or more times and four times or less, followed by two baths containing the crosslinking agent. Since it extended | stretched by extending | stretching magnification higher than the draw ratio of the 1st bath in which the draw ratio put the crosslinking agent after it, it discovered that the polarizing plate which has the characteristic of high transmittance and high polarization degree was obtained. When the bath containing the crosslinking agent is, for example, a third bath, the magnification after the second bath becomes a magnification of the second bath magnification x third bath.

In the present invention as described above, the magnification after the second bath is higher than the draw ratio of the first bath.

Moreover, although shown in the comparative example 2, the draw ratio of the bridge | crosslinking bath of this invention is produced on the conditions of 1st bath <2 bath than the characteristic of the polarizing plate from which the draw ratio of a bridge | crosslinking bath is produced by 1st bath> 2nd bath. It can be seen that the polarizing plate has good characteristics.

The dyeing bath may contain, in addition to the dye or iodine, a crosslinking agent such as iodide such as potassium iodide or boric acid. In order to prevent the occurrence of staining, it is preferable that the temperature of the dyeing bath is 15 ° C or more and 50 ° C or less. When the temperature of the dyeing bath is less than 15 ° C, swelling of the PVA is likely to be insufficient, and swelling stains occur in the plane, and the dyeing stains are likely to occur. Moreover, when it exceeds 50 degreeC, swelling of PVA will become high too much, and swelling unevenness in surface will generate | occur | produce, or PVA will melt | dissolve in part, and dyeing will be easy to stain and it is unpreferable.

Although the draw ratio of the PVA film in a dye bath is not specifically limited, When the draw ratio exceeds 5 times, since the optical property is good, ie, the transmittance | permeability and the polarization degree are hard to be obtained, 5 times or less are preferable, and further, Preferably it is 1.5-5 times. Moreover, when less than 1.5 times, running of a stable film becomes difficult.

In the dyeing step, when the solution in the dye bath is dyed while stirring, the stripe-shaped dyeing stain in the stretching direction is eliminated, and thus the display staining can be improved. Moreover, the method of stirring is not limited, You may use what kind of method. However, if the water flow directly touches the PVA film, traces of the water flow easily remain as stains of dyeing, and it is preferable that the water flow does not directly contact the film. In addition, it goes without saying that it is preferable to make the temperature in a bath uniform. Moreover, it is preferable to extend | stretch a film so that the film in a bath may not loosen, and the loose part will become easy to generate | occur | produce a stain of dyeing. Therefore, you may dye, removing wrinkles by weakly pulling in the horizontal direction at the time of dyeing. Moreover, you may dye along a roll so that wrinkles may not enter.

Moreover, the bath line of the film in a bath is not prescribed | regulated, It is preferable to make the bath line which does not directly contact a film with water flow.

Moreover, according to the production method of the present invention, the bath containing the crosslinking agent is provided at least two baths, the draw ratio of the first bath is made 1 to 4 times, and the draw ratio after the second bath is drawn to the first bath. Although extending | stretching is carried out by elongation higher than magnification, it is because a film will break easily when the draw ratio of 1st bath exceeds 4 times. The draw ratio of the first bath is more preferably 1.2 to 3.5 times.

In the above method, it is preferable that at least one bath temperature after the second bath is higher than the temperature of the first bath containing the crosslinking agent at least 5 ° C. or more than the first bath's crosslinking bath temperature, and each bath temperature is not particularly limited. However, the temperature of the first bath is preferably 10 ° C or more and 90 ° C or less, and more preferably 15 ° C or more and 60 ° C or less. It is because crosslinking will become inadequate when the temperature of 1st bath is less than 10 degreeC, and when it exceeds 90 degreeC, a film will melt | dissolve and break easily.

As the polarizer (polarizing film), for example, a film made of a conventionally suitable vinyl alcohol polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol, or a dichroic substance made of iodine, dichroic dye or the like in the method of the present invention. By performing treatment such as dyeing treatment, stretching treatment, crosslinking treatment, or the like, and when natural light is incident, a suitable one that transmits linearly polarized light can be used. In particular, it is preferable that it is excellent in light transmittance and polarization degree.

As a protective film material which consists of a transparent protective layer provided in one or both sides of a polarizer (polarizing film), a suitable transparent film can be used. As an example of the polymer, an acetate-based resin such as triacetyl cellulose is generally used, but is not limited thereto.

The transparent protective film which can be used especially preferably from the point of polarization characteristic, durability, etc. is the triacetyl cellulose film which saponified the surface with alkali etc. Moreover, when providing a transparent protective film on both sides of a polarizing film, you may use the transparent protective film which consists of a polymer etc. in the front and back.

As long as the objective of this invention is not impaired, the transparent protective film used for a protective layer may perform the process for the purpose of a hard-coat process, an antireflection process, sticking prevention, a diffusion, antiglare, etc. The hard coat treatment is carried out for the purpose of preventing damage to the surface of the polarizing plate, and the like, for example, by forming a cured film having excellent hardness and sliding property by a suitable ultraviolet curable resin such as silicone-based on the surface of the transparent protective film. Can be.

On the other hand, antireflection processing is performed for the purpose of antireflection of external light on the surface of a polarizing plate, and can be achieved by forming antireflection films etc. according to the prior art. In addition, sticking prevention is for preventing adhesion to an adjacent layer, and antiglare treatment is performed for the purpose of preventing external light from reflecting off the surface of the polarizing plate and impairing visibility of the polarizing plate transmitted light. It can form by providing a fine concavo-convex structure to the surface of a transparent protective film by a suitable method, such as a roughening system by an embossing system, the compounding method of transparent fine particles, etc.

Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, and the like, which may be used. Organic microparticles | fine-particles etc. which consist of a crosslinked or uncrosslinked polymer granular material, etc. may be used. The amount of the transparent fine particles used is generally 2 to 70 parts by weight, particularly 5 to 50 parts by weight, per 100 parts by weight of the transparent resin.

The antiglare layer of the transparent fine particle mixture can be provided as a transparent protective layer or as a coating layer on the surface of a transparent protective layer. The antiglare layer may also serve as a diffusion layer (visual compensation function, etc.) for diffusing the polarized plate transmitted light to enlarge the time. The antireflection layer, the sticking prevention layer, the diffusion layer, the antiglare layer, and the like may be provided as a separate optical layer from the transparent protective layer as an optical layer made of a sheet provided with these layers or the like.

Although the adhesive treatment of a polarizer (polarizing film) and the transparent protective film which is a protective layer in this invention is not specifically limited, For example, the adhesive agent which consists of a vinyl alcohol type polymer, or vinyl alcohol, such as a boric acid, borax, glutaraldehyde, melamine, oxalic acid, etc. It can carry out through the adhesive agent etc. which consist of at least the water-soluble crosslinking agent of a system type polymer. Such an adhesive layer can be formed as an application dry layer of an aqueous solution, and at the time of preparation of the aqueous solution, other additives, a catalyst such as an acid, and the like can also be blended.

The polarizing plate by this invention can be used as an optical member laminated | stacked with the other optical layer at the time of practical use. Although there is no limitation in particular about this optical layer, For example, liquid crystal displays, such as a reflecting plate, a semi-transmissive reflecting plate, retardation plate (it also includes lambda plates, such as a 1/2 wave plate and a quarter wave plate), an optical compensation film, a brightness enhancement film, etc. One or two or more layers of a suitable optical layer used for forming an apparatus or the like can be used, and in particular, a reflection type in which a reflecting plate or a semi-transmissive reflecting plate is laminated on a polarizing plate made of the polarizer or the protective layer of the present invention described above. In the polarizing plate or semi-transmissive reflecting plate type polarizing plate, the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above, the ellipse or circular polarizing plate in which retardation plate is laminated, and the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above, and visual compensation The brightness enhancement film is further laminated on the polarizing plate on which the film is laminated or the polarizing plate made of the polarizer and the protective layer of the present invention described above. The polarizing plate is preferable.

In the above description of the reflecting plate, the reflecting plate is provided in the polarizing plate to form a reflecting polarizing plate. The reflecting polarizing plate is usually provided inside the liquid crystal cell, and reflects and displays incident light from the viewing side (display side). Liquid crystal display device, etc. can be formed, built-in light source such as backlight can be omitted, and the liquid crystal display device can be thinned easily.

Formation of a reflective polarizing plate can be performed by a suitable method, such as a method of laying a reflective layer made of metal or the like on one side of the polarizing plate through the transparent protective film or the like as necessary. In addition, as a specific example, what provided the reflective layer by laying the foil and vapor deposition film which consisted of reflective metals, such as aluminum, on one surface of the transparent protective film which carried out the mat process as needed.

Moreover, the reflection type polarizing plate etc. which have a reflecting layer which contained the microparticles | fine-particles on the said transparent protective film which made microparticles | fine-particles structure as surface fine uneven structure are reflected. The reflective layer of the surface fine uneven structure has the advantage of preventing the directivity and the shiny appearance by diffusing the incident light by diffuse reflection, and suppressing unevenness of light and dark. Formation of a reflective layer having a fine uneven structure reflecting the surface fine uneven structure of the transparent protective film may be performed by forming a metal in a suitable manner such as a vapor deposition method such as vacuum deposition method, ion plating method, sputtering method or plating method. It can carry out by the method of directly laying on a surface.

Moreover, instead of the method of directly attaching to the transparent protective film of the said polarizing plate, a reflecting plate can also be used for the reflecting sheet etc. which form a reflecting layer in the suitable film based on the said transparent protective film. Since the reflecting layer of the reflecting plate is usually made of metal, the use mode in which the reflecting surface is covered with a film, a polarizing plate, or the like prevents the lowering of the reflectance due to oxidation, and furthermore, the long-term sustaining point of the initial reflectance or the protective layer. It is preferable at the point of avoiding the separate laying of.

In addition, the semi-transmissive polarizing plate can be obtained by using the above-mentioned reflective layer as a semi-transmissive reflective layer such as a half mirror which reflects light and transmits it. The semi-transmissive polarizing plate is usually provided inside the liquid crystal cell, and when using a liquid crystal display device or the like in a relatively bright atmosphere, reflects incident light from the viewing side (display side) to display an image. A liquid crystal display device of a type for displaying an image can be formed by using a built-in light source such as a backlight built in the backside of the polarizing plate. That is, the transflective polarizing plate can save energy of using a light source such as a backlight in a bright atmosphere, and is useful for forming a liquid crystal display device of the type that can be used using a built-in light source even in a relatively dark atmosphere.

Next, the ellipse or circular polarizing plate in which the retardation plate is laminated | stacked further on the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above is demonstrated.

When the linearly polarized light is changed into ellipse or circularly polarized light, the ellipse or circularly polarized light is changed into linearly polarized light, or the polarization direction of the linearly polarized light is changed, a retardation plate or the like is used, and in particular, the linearly polarized light is changed into elliptic or circularly polarized light. Alternatively, a so-called quarter-wave plate (also referred to as λ / 4 plate) is used as a phase difference plate for converting ellipse or circularly polarized light into linearly polarized light. The half-wave plate (also referred to as λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

The elliptical polarizing plate compensates for the coloring (blue or sulfur) generated by the birefringence of the liquid crystal layer of the STN type liquid crystal display device, and is effectively used for a black and white display without the coloring. In addition, it is preferable to control the three-dimensional refractive index because the coloring degree generated when the screen of the liquid crystal display device is viewed in the oblique direction can be prevented (prevented). The circular polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflection type liquid crystal display device in which an image becomes color display, and also has a function of antireflection.

In addition, as a specific example of the retardation plate, birefringence formed by stretching a film made of a suitable polymer such as polycarbonate, polyvinyl alcohol, polystyrene or polymethyl methacrylate, polypropylene or other polyolefin, polyarylate or polyamide The thing which supported the orientation film of a soluble film, a liquid crystal polymer, and the alignment layer of a liquid crystal polymer with a film, etc. are mentioned. Moreover, as a diagonal orientation film, the thing which carried out the extending | stretching process of the polymer film, and / or the shrinkage | contraction process, the diagonal orientation of the liquid crystal polymer, etc. are mentioned, for example by adhering a heat shrinkable film to a polymer film and the action of the shrinkage force by heating.

Next, the polarizing plate in which the visual compensation film is further laminated on the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above is demonstrated.

The visual compensation film is a film for widening the vision so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly inclined direction rather than perpendicular to the screen.

As such a visual compensation film, what coated the discotic liquid crystal on a triacetyl cellulose film etc., and a retardation plate are used. Whereas a conventional retarder is a birefringent polymer film drawn in one plane in the plane direction thereof, a retarder used as a visual compensation film is a birefringent polymer film drawn in the plane direction or in the plane direction. The bidirectional stretched film like the diagonally-oriented polymer film which restrained the refractive index of the thickness direction extended | stretched to one axis and extended also in the thickness direction is used. As the diagonally oriented film, as described above, for example, a heat-shrinkable film is adhered to the polymer film, and the polymer film is stretched or / and shrunk under the action of the shrinkage force by heating, or the diagonally oriented liquid crystal polymer is mentioned. have. As the raw material polymer of the retardation plate, the same polymer as described in the above retardation plate is used.

The polarizing plate which bonded the brightness improving film to the polarizing plate which consists of a polarizer and a protective layer of this invention mentioned above is normally provided and used in the inner side of a liquid crystal cell. The luminance enhancing film reflects linearly polarized light on a predetermined polarization axis or circularly polarized light in a predetermined direction when natural light is incident due to a backlight or reflection from inside of a liquid crystal display device, and the other light transmits. The polarizing plate laminated | stacked with the polarizing plate which consists of a polarizer and a protective layer mentioned above injects light from a light source, such as a backlight, and acquires the transmitted light of a predetermined polarization state, and light other than the said predetermined polarization state is reflected without being transmitted. The light reflected from the surface of the brightness enhancing film is again inverted through a reflecting layer or the like provided on the rear side thereof, and reincident to the brightness improving plate, and part or all of the light is transmitted as light in a predetermined polarization state to transmit light of the brightness enhancing film. The luminance can be improved by increasing the amount of light and increasing the amount of light that can be used for liquid crystal display by supplying polarized light that is hardly absorbed by the polarizer. That is, when light is incident from the inside of the liquid crystal cell through the backlight without using the brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is almost absorbed by the polarizer, thereby causing the polarizer Does not penetrate That is, although it varies with the characteristic of the polarizer used, about 50% of light is absorbed by the polarizer, and the quantity of light which can be used for a liquid crystal image display etc. decreases by that amount, and an image becomes dark. The brightness enhancement film inverts the light having the polarization direction absorbed by the polarizer into the brightness enhancement film without incidence of the polarizer, and then inverts again through a reflecting layer or the like installed on the rear side and reenters the brightness enhancement plate. Since the brightness enhancement film transmits the polarization direction in which the polarization direction of the light reflected and inverted between the two passes through the polarizer, the brightness enhancement film is transmitted to the polarizer, so that light such as a backlight can be efficiently displayed on the image of the liquid crystal display device. I can use it and can brighten the screen.

As the brightness enhancing film, for example, a multilayer thin film of a dielectric material or a multilayer stack of thin film films having different refractive index anisotropy, the characteristics of transmitting linearly polarized light of a predetermined polarization axis and reflecting other light are exhibited (D-BEF manufactured by 3M Corporation). And the like, and supporting the cholesteric liquid crystal layer, in particular, the alignment film of the cholesteric liquid crystal polymer and the alignment liquid crystal layer on the film substrate ("PCF 350" manufactured by Nitto Denko Corporation, "Transmax" manufactured by Merck Corporation). Or a suitable thing, such as showing the characteristic which reflects the circularly polarized light in either of right turns, and transmits other light, can be used.

Therefore, in the luminance improvement film of the type which transmits the linearly polarized light of the said predetermined polarization axis, it can transmit efficiently while suppressing the absorption loss by a polarizing plate by making the transmitted light into a polarizing plate and making it incident. On the other hand, in the luminance-enhancing film that passes circularly polarized light, such as a cholesteric liquid crystal layer, the polarizer may be applied as it is, but rather than suppressing absorption loss, the transmitted circularly polarized light is linearly polarized through the retardation plate to the polarizer. It is preferable to make it incident. In addition, circular polarization can be converted into linearly polarized light by using a quarter wave plate as the retardation plate.

A retardation plate functioning as a quarter wave plate in a wide wavelength range such as visible light is a retardation layer exhibiting retardation characteristics different from a retardation layer functioning as a quarter wave plate for monochromatic light such as light having a wavelength of 550 nm, for example. It can obtain by the method of superimposing the retardation layer which functions as a 1/2 wave plate. Therefore, the phase difference plate arrange | positioned between a polarizing plate and a brightness improving film should just consist of one or two or more phase difference layers.

In addition, also in the cholesteric liquid crystal layer, although the reflection wavelength is different, by setting the arrangement structure in which two or more layers are superimposed in combination, it is possible to obtain the reflection of the circularly polarized light in a wide wavelength range such as visible light. Based on this, transmission circularly polarized light in a wide wavelength range can be obtained.

Moreover, the polarizing plate of this invention may consist of what laminated | stacked the polarizing plate and the optical layer of 2 or 3 layers or more like the said polarization split type polarizing plate. Therefore, the reflective elliptical polarizing plate, the semi-transmissive elliptical polarizing plate, etc. which combined the said reflective polarizing plate, the transflective polarizing plate, and the retardation plate may be sufficient. Although the optical member which laminated | stacked two or three or more optical layers can be formed also in the method of laminating | stacking them separately separately in the manufacturing process of a liquid crystal display device, etc., what laminated | stacked previously was made into the optical member, It is excellent in the assembly workability and the like, there is an advantage that can improve the manufacturing efficiency of the liquid crystal display device. Moreover, suitable adhesion means, such as an adhesion layer, can be used for lamination | stacking.

The polarizing plate and the optical member according to the present invention may be provided with an adhesive layer for adhering with other members such as liquid crystal cells. This pressure-sensitive adhesive layer can be formed of a conventional pressure-sensitive adhesive such as acrylic. In particular, in view of prevention of foaming or peeling phenomenon due to moisture absorption, reduction of optical properties due to thermal expansion difference, prevention of warpage of liquid crystal cells, and furthermore, formation of a liquid crystal display device having high quality and durability, It is preferable that it is a low pressure adhesive layer excellent in heat resistance. Moreover, it can also be set as the adhesion layer etc. which contain microparticles | fine-particles and show light diffusivity. If necessary, the adhesive layer may be provided on the required surface. For example, when referring to the protective layer of the polarizing plate comprising the polarizer and the protective layer of the present invention, the adhesive layer may be provided on one or both sides of the protective layer as necessary. .

When the adhesive layer provided in a polarizing plate or an optical member is exposed to a surface, it is preferable to temporarily attach and cover a separator for the purpose of contamination prevention, etc., until the adhesive layer is practically provided. The separator can be formed in a suitable thin film according to the above-mentioned transparent protective film or the like by a method of providing a release coat with a suitable release agent such as silicon, long chain alkyl, fluorinated or molybdenum sulfide, or the like. .

Moreover, each layer, such as a polarizing film, a transparent protective film, an optical layer, and an adhesion layer which form the said polarizing plate and an optical member, is a salicylic acid ester type compound, a benzophenone type compound, a benzotriazole type compound, and a cyanoacrylate type compound, for example. And the ultraviolet absorbing ability by a suitable method such as treatment with an ultraviolet absorber such as a nickel complex salt compound or the like.

The polarizing plate by this invention can be used suitably for formation of various apparatuses, such as a liquid crystal display device. The liquid crystal display device can be formed by having a suitable structure according to the prior art, such as a transmission type, a reflection type, or a transmission / reflection combined use type, which is formed by arranging the polarizing plate according to the present invention on one side or both sides of a liquid crystal cell. Therefore, the liquid crystal cell which forms a liquid crystal display device is arbitrary, for example, an active matrix drive type | mold represented by a thin-film transistor type, a simple matrix drive type | mold represented by a twisted nematic type or a super twisted nematic type etc. What used the liquid crystal cell may be sufficient.

Moreover, when providing a polarizing plate and an optical member in both sides of a liquid crystal cell, these may be the same and may differ. In the formation of the liquid crystal display device, for example, a suitable component such as a prism array sheet, a lens array sheet, a light diffusion plate, a backlight, or the like can be arranged at a suitable position in one or two or more layers.

(Example)                     

Hereinafter, the present invention will be described in more detail using examples.

(Comparative Example 1)

Roll extending | stretching was performed using Curase PVA (9X75R). In the first bath (iodine, aqueous solution of KI at 35 ° C.), the film was drawn to a total draw ratio of 3 times, followed by stretching in a second bath (boric acid, KI aqueous solution at 53 ° C.) by 6.0 times, followed by a 50 ° C. dryer. It dried with and produced the polarizer, and bonded together using the TAC (triacetyl cellulose) film and PVA-type adhesive agent after that, and produced the polarizing plate. The transmittance / polarization degree of the obtained polarizing plate was 43.7% / 99.80%.

(Comparative Example 2)

Roll extending | stretching was performed using Curase PVA (9X75R). In the first bath (iodine, aqueous solution of KI at 35 ° C.), stretching to a total draw ratio of 3 times, followed by 1.8 times stretching in the second bath (boric acid, KI solution at 40 ° C.) (total magnification of 5.4 times), and the third It extended | stretched 1.11 times (total magnification 6 times) in the bath (boric acid, 60 degreeC KI aqueous solution), and dried with the 50 degreeC dryer after that, and produced the polarizer. Then, it bonded together using the TAC (triacetyl cellulose) film and PVA-type adhesive agent, and produced the polarizing plate. The transmittance / polarization degree of the obtained polarizing plate was 43.8% / 99.80%.

(Example 1)

Roll extending | stretching was performed using Curase PVA (9X75R). In the first bath (iodine, aqueous solution of KI at 35 ° C.), stretching up to a total draw ratio of 3 times, followed by 1.3 times stretching in a second bath (boric acid, KI aqueous solution at 40 ° C.) (total ratio of 3.9 times), and It extended | stretched 1.54 times (total magnification 6 times) in the bath (boric acid, 60 degreeC of KI aqueous solution), and dried with the 50 degreeC dryer after that, and produced the polarizer. Then, it bonded together using the TAC (triacetyl cellulose) film and PVA-type adhesive agent, and produced the polarizing plate. The transmittance / polarization degree of the obtained polarizing plate was 44.1% / 99.95%.

(Example 2)

Roll extending | stretching was performed using Curase PVA (9X75R). In the first bath (iodine, aqueous solution of KI at 35 ° C.), stretching to a total draw ratio of 3 times, followed by 1.2 times stretching (total magnification of 3.6 times) in the second bath (boric acid, KI solution at 40 ° C.), and the third It extended | stretched 1.67 times (total magnification 6 times) in bath (boric acid, 60 degreeC aqueous solution of KI aqueous solution), and dried with the 50 degreeC dryer after that, and produced the polarizer. Then, it bonded together using the TAC (triacetyl cellulose) film and PVA-type adhesive agent, and produced the polarizing plate. The transmittance / polarization degree of the obtained polarizing plate was 44.1% / 99.95%.

The results are shown in Table 1.

Table 1

   Single penetration amount (%)      % Polarization    Parallel transmission / orthogonal transmission    Comparative Example 1       43.7       99.80       510    Comparative Example 2       43.8       99.80       508    Example 1       44.1       99.95      1965    Example 2       44.1       99.95      2183

As can be seen from Table 1, the difference between the single transmittance and the degree of polarization of Comparative Examples 1 and 2 and Examples 1 and 2 seems to be small below the decimal point, but this difference is a large difference. As a numerical value which can confirm the difference, if the ratio of "parallel transmittance" and "orthogonal transmittance" used when calculating polarization degree is taken, as shown in a table, it can confirm with a big difference in a comparative example and an Example. The ratio of "parallel transmittance" and "orthogonal transmittance" may be viewed as the contrast of the polarizing plate.

As described above, the method for producing a polarizing plate of the present invention dyes a polyvinyl alcohol (PVA) film with a dye solution containing iodine having a dichroic property, crosslinks it with a crosslinking agent, and at least one pair in the above step. In the method of extending | stretching using a roll and manufacturing the polarizing plate, the bath containing the said crosslinking agent is installed 2 times or more, The draw ratio of the 1st bath is 1 times or more and 4 times or less, The draw ratio after the 2nd bath is the said By extending | stretching at elongation higher than the draw ratio of a 1st bath, the polarizing plate which has high transmittance | permeability and the characteristic of high polarization can be provided. Moreover, the liquid crystal display device provided with the polarizing plate obtained by this method similarly has a high transmittance and high polarization characteristic.

Claims (13)

In the method of manufacturing a polarizing plate by dyeing a polyvinyl alcohol (PVA) film with a dye solution containing iodine having a dichroic property, crosslinking with a crosslinking agent, and stretching using at least one pair of rolls in the above step. , The bath containing the said crosslinking agent is installed in 2 or more baths, The draw ratio of the 1st bath of the bath which put the said crosslinking agent is 1 times or more and 4 times or less, The draw ratio after the 2nd bath of the bath containing the said crosslinking agent extends | stretches by elongation higher than the draw ratio of the 1st bath of the bath containing the said crosslinking agent, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method of claim 1, A method for producing a polarizing plate, wherein at least one bath temperature after the second bath is higher than the temperature of the first bath containing the crosslinking agent at least 5 ° C. or higher than the temperature of the first bath. The method of claim 2, The bath temperature of the 2nd bath | bath than the temperature of the 1st bath containing a crosslinking agent is 5 degreeC or more higher than the crosslinking bath temperature of the 1st bath, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method of claim 2, The temperature of the 1st bath containing a crosslinking agent is 10 degreeC or more and 90 degrees C or less, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method of claim 1, The bath containing the said dyeing liquid does not contain a crosslinking agent, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method of claim 1, Crosslinking in the said crosslinking agent is performed after dyeing in the said dyeing liquid, Extending | stretching in the bath containing the said dyeing liquid, Two baths containing the crosslinking agent were installed, Extending | stretching each in the bath containing the said 2 bath crosslinking agent, The draw ratio of the 2nd bath of a bath containing a crosslinking agent extends | stretches by elongation higher than the draw ratio of the 1st bath of a bath containing a crosslinking agent, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method according to any one of claims 1 to 6, The draw ratio of the PVA film in the dye bath containing the dyeing solution is 5 times or less, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method according to any one of claims 1 to 6, The manufacturing method of the polarizing plate which is the temperature of the dyeing bath which put the dyeing solution in 15 degreeC or more and 50 degrees C or less. The manufacturing method of the polarizing plate characterized by bonding a reflecting plate or a semi-transmissive reflecting plate to the polarizing plate manufactured by the method in any one of Claims 1-6, and forming a reflective polarizing plate or a semi-transmissive reflecting plate type polarizing plate. The manufacturing method of the polarizing plate characterized by bonding a retardation plate or a (lambda) plate to the polarizing plate manufactured by the method in any one of Claims 1-6, and forming an ellipse or a circular polarizing plate. The polarizing plate is bonded to the polarizing plate manufactured by the method in any one of Claims 1-6, and a polarizing plate is formed, The manufacturing method of the polarizing plate characterized by the above-mentioned. The manufacturing method of the polarizing plate characterized by bonding a viscosity improving film to the polarizing plate manufactured by the method in any one of Claims 1-6 using an adhesive agent or an adhesive, and forming a polarizing plate. The polarizing plate manufactured by the method of Claim 1 thru | or 6 was provided in at least one of the liquid crystal cells, The liquid crystal display device characterized by the above-mentioned.