KR100866005B1 - Polarization plate, method for manufacturing the same and liquid crystal display device - Google Patents

Abstract

Provided is a polarizing plate for use in LCDs with improved display unevenness due to staining unevenness.

When dyeing a polyvinyl alcohol (PVA) film, in a dye bath having a dichroic dye or iodine concentration of 0.02 wt% or more, the temperature of the dye bath is 15 ° C. or more and 50 ° C. or less, and the draw ratio in the bath is It is 5 times or less, and it dyes, stirring the bath liquid.

Description

Polarizing plate, method for manufacturing the same and liquid crystal display device

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate and a liquid crystal display device for use in a liquid crystal display device (hereinafter sometimes abbreviated as LCD) in which display spots, in particular, stains are improved.

LCDs are used in PCs and the like and are rapidly increasing in recent years. The use of LCDs is expanding, and recently, they are also used for monitors.

However, compared to PC applications, monitor LCDs have larger screen sizes and larger panel brightness. In addition to personal use, such as a PC, many people have more opportunities to see, because the view from a diagonal direction as well as from the front is required a high viewing angle display. In addition, since a bright screen is required for a monitor, a backlight is often used for a high brightness one. Therefore, when the display is made into black display or viewed in an oblique direction, unevenness of the dyed state of the polarizing plate is easily seen, and in particular, striped unevenness is seen in the stretching axis direction of the polarizing plate, which is a display problem. Therefore, there is a need for a polarizing plate which does not show staining even when used in an LCD having improved panel brightness.                         

The polarizing plate which does not show the dyeing stain here does not show the dyeing stain which can be confirmed by one polarizing plate (single body), but the dyeing staining is not seen by one polarizing plate (single body), and the two polarizing plates overlapped so that extending direction may be orthogonal. (Orthogonal state) refers to a polarizer that does not see stains even when. The dye stain of the polarizing plate is not a dye stain seen by a single body, which occurs when dyeing other general papers or sheets with a dye, but refers to a stain seen when two sheets are orthogonal although they are not seen by a single body.

An object of this invention is to provide the manufacturing method of a polarizing plate used for the LCD which the display unevenness | dye resulting from dyeing unevenness improved, and a polarizing plate and a liquid crystal display device in order to solve the said conventional problem.

In order to achieve the above object, the method for producing a polarizing plate of the present invention, the polyvinyl alcohol (PVA) film is dyed with a dye or iodine having a dichroic nature, crosslinked with a crosslinking agent, during or before or after these steps In the method of manufacturing a polarizing plate by extending | stretching and drying, a protective layer is bonded to both surfaces or single side | surface, WHEREIN: The dyeing bath temperature is 15 degreeC in the dyeing bath whose density | concentration of the said dichroic dye or iodine is 0.02 wt% or more. The stretching ratio in the bath is 50 ° C. or lower and 5 times or less, and the bath solution in the bath is dyed with stirring. When the concentration of the dye or iodine having the dichroic property is less than 0.02 wt%, the dyeing concentration is not sufficient. When the temperature of the dyeing bath is less than 15 ° C, the swelling of the PVA is insufficient and it is easy to become stained. When the temperature of the dyeing bath exceeds 50 ° C, the PVA film of the base material partially dissolves and swelling is generated, resulting in dyeing. It is not desirable to obtain. Moreover, when the draw ratio in a dye bath exceeds 5 times, orientation will advance too much and it is unpreferable. In addition, when the bath solution in the bath is dyed while stirring, staining is eliminated, whereby the display stain can be improved.

In the said method, you may contain 0.01-15 wt% of iodide represented by potassium iodide in a dyeing bath.

Moreover, in the said method, you may contain 2-10 weight% of crosslinking agents represented by boric acid in a dyeing bath.

Moreover, in the said method, stirring is reversed from stirring by a rotary blade, stirring by water flow, stirring by ultrasonic waves, stirring by air blowing in a bath, stirring by the water flow of a perpendicular | vertical direction with respect to an extending | stretching direction, and opposite. It is preferable that it is at least 1 stirring selected from stirring by the water flow in a direction.

In addition, before the dyeing step, as a pretreatment, water may be swollen with a swelling bath, a humidity control treatment, or stretching under dry conditions.

It is good also as a reflective polarizing plate or a semi-transmissive reflecting plate type polarizing plate which bonded the reflecting plate or the transflective reflecting plate to the polarizing plate manufactured by any one of said methods.

Moreover, it is good also as an ellipse or circular polarizing plate which bonded the retardation plate or (lambda) plate to the polarizing plate manufactured by any one of said methods.                     

Moreover, it is good also as a polarizing plate which bonded the visual compensation film to the polarizing plate manufactured by any one of said methods.

Moreover, it is good also as a polarizing plate which bonded the brightness improving film to the polarizing plate manufactured by any one of said methods using an adhesive agent or an adhesive.

Moreover, it is good also as a liquid crystal display device which has any one of said polarizing plates on at least one side of a liquid crystal cell.

Embodiment of the Invention

The manufacturing method of a polarizing film generally carries out the "dyeing process" which dyes a PVA film in the bath containing iodine or dye which has a dichroic characteristic, and the "crosslinking process" which crosslinks in the bath containing the crosslinking agent of PVA, such as boric acid and borax. And three steps of the "stretching process" which extends | stretches 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, you may perform a dyeing process and a crosslinking process simultaneously. The polarizing film is a triacetyl cellulose (TAC) film which is dried after the above three steps and serves as a protective layer, a film such as polyethylene resin or polyethylene terephthalate (PET) film, polystyrene resin, polycarbonate resin, polynor It is produced by bonding a transparent film to one side or both sides from a film of bornenic resin or acrylic resin.

In the present invention, as a result of examining a polarizing plate in which dyeing stains are not seen even when used in a high-brightness LCD such as a monitor, the concentration of a dye or iodine having a dichroic property in the manufacturing process of the polarizing plate is 0.02 wt% or more in a dyeing bath. In the process, when the concentration of the dyeing bath is 15 ° C. or more and 50 ° C. or less, the draw ratio in the stretching bath is 1 or more and 5 times or less, and when the solution in the bath is dyed while stirring, streaked dye spots in the stretching direction are generated. I did not find it.

 Here, when the dye or iodine concentration is too high, the transmittance of the polarizing plate generally tends to decrease, so it is preferable to set it to 0.02 wt% or more and 1.0 wt% or less. Among them, dyeing with iodine is preferably used because of its high transmittance and high polarization, i.e., high dichroism. Moreover, when the draw ratio in dyeing is too low, since running of a stable PVA film becomes difficult, it is preferable to make draw ratio about 1.5 to 5 times in order to mass-produce the polarizing film which is excellent in an optical characteristic.

The dyeing bath may contain, in addition to the dye or iodine, an iodide such as potassium iodide or a crosslinking agent such as boric acid. The iodide may be used in an amount of 0.01 to 15 wt% and 2 to 10 wt%. In addition to potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like may be used. , Dyeing efficiency can be increased. Moreover, borax etc. can also be used besides boric acid as a crosslinking agent, It is preferable at the point which can extend | stretch a PVA film stably by adding a crosslinking agent in a dyeing bath, and obtains the polarizing film excellent in in-plane uniformity. These iodide and boric acid can be used individually or in combination, respectively.                     

The stirring method of a dyeing bath is not prescribed | regulated, You may use what kind of method. However, when the water flows directly on the PVA film, it is preferable that the water flow does not directly contact the film because traces of the water tend to remain as stains. It goes without saying that it is preferable to make the temperature in the bath uniform. Moreover, it is preferable to extend | stretch a film so that a film in a bath may not be drooped, and a drooping part becomes easy to produce a dyeing stain. Therefore, you may dye, removing wrinkles by weakly pulling in the horizontal direction at the time of dyeing. Moreover, what is necessary is just to dye according to a roll and to prevent a wrinkle from entering.

If the speed of the water flow at the time of stirring is too slow, the stain stain suppression effect is insufficient. On the other hand, if the speed is too fast, the PVA film needs to be stretched in the bath or the tension of the PVA film is more than necessary to eliminate the sagging. Thereby, in order to prevent an abnormality generate | occur | producing in the orientation of PVA, it is preferable to set it as about 0.3 m / sec-10 m / sec.

In addition, the bath line of the film in a bath is not prescribed | regulated, It is preferable to set it as the bath line which does not directly contact a film with water flow.

In addition, before the dyeing step, as a pretreatment, it is possible to swell in a swelling bath containing water as a main component, to perform a humidity control treatment, or to perform stretching under dry conditions, and there is no particular limitation on methods such as these treatments and stretching. Can be used as appropriate.

As a polarizer (polarizing film), the film which consists of iodine, a dichroic dye, etc. in the film which consists of conventionally suitable vinyl alcohol type polymers, such as a polyvinyl alcohol and a partially formalized polyvinyl alcohol, is used, for example using the method of this invention. Appropriate treatment such as dyeing treatment, stretching treatment or crosslinking treatment with a dichroic substance is carried out in an appropriate order or manner. An appropriate one that transmits linearly polarized light can be used when natural light is incident. In particular, it is preferable that it is excellent in light transmittance and polarization degree.

As a protective film material used as the transparent protective layer formed in the one side or both sides of a polarizer (polarizing film), an appropriate 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 suitably from a point of polarization characteristic, durability, etc. is the triacetyl cellulose film which saponified the surface with alkali. In addition, when forming a transparent protective film on both sides of a polarizing film, you may use the transparent protective film which consists of a polymer etc. which are different from the inside.

As long as the objective of this invention is not impaired, the transparent protective film used for a protective layer may perform hard coat treatment, an anti-reflective treatment, the treatment for the prevention of sticking, the spreading | diffusion, antiglare, etc., and the like. The hard coat treatment is carried out for the purpose of preventing scratches on the surface of the polarizing plate, or the like, for example, by adding a cured film having excellent hardness and slipperiness by a suitable ultraviolet curable resin such as silicone to the surface of the transparent protective film. Can be formed.

On the other hand, the anti-reflection treatment is carried out for the purpose of preventing the 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 prior art. In addition, sticking prevention is for the purpose of preventing close contact with 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 impairing the visibility of the polarizing plate transmitted light, for example, sand blasting. It can form by providing a fine uneven | corrugated structure to the surface of a transparent protective film by a suitable method, such as a roughening method by a system, an embossing system, etc., and the compounding method of a transparent fine particle.

Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide, having an average particle diameter of 0.5 to 20 µm. Moreover, you may use organic microparticles | fine-particles etc. which consist of a crosslinked or uncrosslinked polymer particulate matter, etc. The amount of 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 formed as the transparent protective layer itself or as a coating layer on the surface of the 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 formed as a separate body from the transparent protective layer as an optical side made of a sheet or the like on which these layers are formed.

In the present invention, the adhesion treatment between the polarizer (polarizing film) and the transparent protective film as the protective layer is not particularly limited, but for example, an adhesive made of a vinyl alcohol polymer, or boric acid, borax, glutaraldehyde, melamine, oxalic acid, or the like. It can be performed through the adhesive etc. which consist of at least the water-soluble crosslinking agent of the vinyl alcohol polymer of the above. Such an adhesive layer can be formed as a coating dry layer of an aqueous solution, but in the preparation of the aqueous solution, other additives, catalysts such as an acid, and the like can also be blended if necessary.

The polarizing plate by this invention can be used as an optical member laminated | stacked with the other optical layer in practical use. The optical layer is not particularly limited, but for example, a reflecting plate, a transflective reflecting plate, a retardation plate (including λ plates such as a 1/2 wave plate and a quarter wave plate), an optical compensation film, a brightness enhancement film, and the like. One or two or more layers of a suitable optical layer that can be used for forming a liquid crystal display device can be used, and in particular, a reflecting plate or a semi-transmissive reflecting plate is laminated on a polarizing plate comprising the polarizer and the protective layer of the present invention described above. In a polarizing plate comprising a reflective polarizing plate or a semi-transmissive reflecting plate polarizing plate, the polarizing plate made of the polarizer and the protective layer of the present invention described above, and a retardation plate is laminated, or a polarizing plate made of the circular polarizing plate and the polarizing plate and the protective layer of the present invention described above, Furthermore, to the polarizing plate which the visual compensation film is laminated | stacked, or the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above, Furthermore, The polarizing plate, which is also improving the film is laminated is preferred.

In the above description of the reflecting plate, the reflecting plate is used to form a reflecting polarizing plate by installing it on the polarizing plate, and the reflecting polarizing plate is usually provided on the rear side of the liquid crystal cell, and reflects and displays incident light from the viewing side (display side). Type liquid crystal display device, etc. can be formed, and it is possible to omit the incorporation of a light source such as a backlight, and thus it is easy to reduce the thickness of the liquid crystal display device.

Formation of a reflection type polarizing plate can be performed by a suitable method, such as the method of laying a reflective layer which consists of metal etc. on the single side | surface of a polarizing plate through said transparent protective film etc. as needed. In addition, as a specific example, what provided the reflective layer by laying the foil and vapor deposition film which consist of reflective metals, such as aluminum, on the single side | 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 reflected the micro-concave-convex structure on the said transparent protective film which contained microparticles | fine-particles and made into the surface micro-concave-convex structure are also mentioned. The reflective layer of the surface fine uneven structure has the advantage of being able to diffuse incident light by diffuse reflection to prevent directivity and glare, and to suppress light and dark unevenness. Formation of the reflective layer of the finely uneven structure reflecting the surface finely uneven structure of the transparent protective film, for example, transparent protection of the metal by an appropriate method such as deposition method or plating method such as vacuum deposition method, ion plating method, sputtering method or the like. It can carry out by the method of directly laying on the surface of a film.

Moreover, the reflecting plate can also be used as a reflecting sheet etc. which form a reflecting layer in the suitable film according to the transparent protective film instead of the method of directly attaching to the transparent protective film of the said polarizing plate. Since the reflecting layer of the reflecting plate is usually made of metal, the use form in which the reflecting surface is covered with a film, a polarizing plate or the like prevents the reduction of the reflectance due to oxidation, and furthermore, the long-term duration of the initial reflectance or the additional laying of the protective layer. It is preferable in the avoidance of such.                     

In addition, a semi-transmissive polarizing plate can be obtained by making the reflective layer into the semi-transmissive reflective layer, such as a half mirror which reflects light and permeate | transmits above. The transflective polarizing plate is usually provided on the rear side of 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, and in a relatively dark atmosphere, A liquid crystal display device of a type for displaying an image and the like can be formed by using a built-in light source such as a backlight built into the back side of the transmissive polarizing plate. That is, the transflective polarizing plate can save energy of using light sources 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 further laminated | stacked on the polarizing plate which consists of the polarizer and protective layer of this invention mentioned above is demonstrated.

In case of changing linearly polarized light into elliptic or circularly polarized light, or changing elliptic or circularly polarized light into linearly polarized light, or changing the polarization direction of linearly polarized light, a retardation plate or the like is used, in particular, linearly polarized light into elliptic or circularly polarized light, As a phase difference plate which changes ellipse or circularly polarized light into linearly polarized light, what is called a 1/4 wavelength plate (it is also called (lambda) / 4 plate) is used. A half wave plate (also called a lambda / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

An elliptically 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 it can compensate (prevent) coloration generated when the screen of the liquid crystal display device is viewed from the diagonal direction. The circular polarizing plate is effectively used, for example, when maintaining 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 said retardation plate, birefringence formed by extending | stretching the film which consists of suitable polymers, such as a polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, another polyolefin, polyarylate, and 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 an inclination oriented film, the thing which carried out the extending | stretching process and / or the shrinkage | contraction processing of the polymer film, or the diagonal alignment 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. Can be.

Next, the polarizing plate in which the visual compensation film is further laminated | stacked 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 the image looks relatively clear even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen.

As such a visual compensation film, what coated the disk coating liquid crystal etc. with a triacetyl cellulose film, and a retardation plate are used. The retardation plate used as the visual compensation film is a polymer film having birefringence stretched biaxially in the plane direction, or a planar retardation film, compared to a polymer film having birefringence stretched uniaxially in the plane direction thereof. Two-side stretched films, such as the diagonally-oriented polymer film which extended | stretched uniaxially and controlled also the refractive index of the thickness direction extended also in the thickness direction, are used. As the diagonally oriented film, as described above, for example, a heat shrinkable film is adhered to a polymer film, and the polymer film is stretched and / or shrunk under the action of the shrinkage force by heating, or the liquid crystal polymer is diagonally aligned, or the like. Can be mentioned. The raw material polymer of the retardation plate is the same as the polymer described in the above retardation plate.

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 in the back side of a liquid crystal cell, and is used. The brightness enhancement film reflects direct polarization of a predetermined polarization axis or circular polarization in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the rear side, and exhibits a property of transmitting other light. The polarizing plate which laminated | stacked the film and the polarizing plate which consists of a polarizer and a protective layer which were mentioned above is made to let light from a light source, such as a backlight, and to transmit the light of a predetermined polarization state, and to reflect, without transmitting the light other than the said predetermined polarization state. do. The light reflected from the surface of the brightness enhancing film is further inverted through a reflecting layer or the like provided on the rear side thereof, and re-entered into the brightness improving plate, and a part or all of the light is transmitted as light in a predetermined polarization state to increase the amount of light passing through the brightness enhancing film. In addition, the luminance can be improved by supplying polarized light that is hardly absorbed by the polarizer to increase the amount of light that can be used for liquid crystal image display. That is, when light is made to enter through a polarizer from the back side of a liquid crystal cell with a backlight etc. without using a brightness improving film, the light which has a polarization direction which does not correspond to the polarization axis of a polarizer is absorbed by a polarizer, Does not transmit polarizer. That is, although it depends also on the characteristic of the polarizer used, almost 50% of light is absorbed by the polarizer, and the quantity of light which can be used for a liquid crystal display device etc. reduces by that much, and an image becomes dark. The brightness enhancement film repeatedly reflects light having a polarization direction absorbed by the polarizer into the brightness enhancement film without being incident on the polarizer, and is then inverted through a reflection layer or the like provided on the rear side and reincident to 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 becomes the polarization direction that can pass through the polarizer, the brightness enhancement film is transmitted to the polarizer, so that light such as backlight can be efficiently transferred to the image of the liquid crystal display device. We can use for display and can make screen bright.

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 light transmits linearly polarized light of a predetermined polarization axis and reflects other light. -BEF] and the like, and a cholesteric liquid crystal layer, in particular, an oriented film of the cholesteric liquid crystal polymer and an oriented liquid crystal layer supported on the film substrate ("PCF350" manufactured by Nitto Denkosha, "Transmax" manufactured by Merck), Suitable ones, such as those which reflect the circularly polarized light of either the left turn or the right turn and transmit other light, can be used.

Therefore, in the brightness improvement film of the type which permeate | transmits linearly polarized light of the said predetermined polarization axis, it can transmit efficiently, suppressing the loss of absorption by a polarizing plate by making the transmitted light into a polarizing plate as it is, and making it incident. On the other hand, in the luminance-enhancing film of the type which transmits circularly polarized light like a cholesteric liquid crystal layer, although it may be incident on a polarizer as it is, in view of suppressing absorption loss, the transmitted circularly polarized light is linearly polarized through a retardation plate to a polarizing plate. 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.

The retardation layer which functions as a quarter wave plate in a wide wavelength range of a visible range etc., for example, is a phase difference layer which shows retardation characteristics different from the retardation layer which functions as a quarter wave plate with respect to monochromatic light, such as light of wavelength 550nm. 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 may consist of one layer or two or more phase difference layers.

In addition, also in the cholesteric liquid crystal layer, when the arrangement structure in which two or three or more layers are superposed with respect to the combination of the different reflection wavelengths, it is possible to obtain the reflection of the circularly polarized light in a wide wavelength range in the visible region and the like. 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 funnel plate and two or three or more optical layers 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. An optical member in which two or three or more optical layers are laminated may be formed by a method of separately stacking the optical members in a manufacturing process such as a liquid crystal display, or the like. It is excellent in assembly workability, and there exists an advantage which can improve manufacturing efficiency, such as a liquid crystal display device. In addition, suitable bonding means, such as an adhesion layer, can be used for lamination.

In the polarizing plate and the optical member according to the present invention, an adhesive layer for adhering with other members such as a liquid crystal cell may be formed. The pressure-sensitive adhesive layer can be formed of a conventional pressure-sensitive adhesive such as alkali. In particular, the moisture absorption rate is low in terms of prevention of foaming or peeling phenomenon due to moisture absorption, reduction of optical characteristics due to thermal expansion difference, prevention of warpage of liquid crystal cells, and further, formation of a high quality and durable liquid crystal display device. It is preferable that it is an adhesion 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. What is necessary is just to form an adhesion layer in a required surface as needed, for example, if mentioning the protective layer of the polarizing plate which consists of a polarizer and a protective layer of this invention, what is necessary is just to form an adhesion layer in the single side | surface or both surfaces of a protective layer as needed. .

When the adhesion layer formed in a polarizing plate or an optical member is exposed to the surface, it is preferable to cover temporarily with a separator for the purpose of contamination prevention etc. until the adhesion layer is put into practical use. The separator can be formed on a suitable thin film according to the above-mentioned transparent protective film or the like by a method of forming a release coat with a suitable release agent such as silicone-based, long-chain alkyl-based, fluorine-based, 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 sarytylic acid ester type compound, a benzophenone type compound, a benzotriazole type compound, and a cyano acryl, for example. The thing which gave ultraviolet absorbing ability by the appropriate system, such as a process with ultraviolet absorbers, such as a late type compound and a nickel complex salt type compound, may be sufficient.

The polarizing plate by this invention can be used suitably for formation of various apparatuses, such as a liquid crystal display device. A liquid crystal display device can be formed as having a suitable structure according to the prior art, such as a transmission type, a reflection type, or a transmission / reflective use type formed by disposing 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 appropriate type liquid crystal cell, such as an active matrix drive type | mold represented by a thin-film transistor type, the simple matrix drive type represented by a twisted nematic type, or a super twisted nematic type. May be used.

Moreover, when providing a polarizing plate and an optical member in both sides of a liquid crystal cell, they may be the same or 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 disposed at an appropriate position in one or two or more layers.

As for the polarizing plate of this invention, the stain | dye resulting from dyeing is no longer seen also in LCD, such as for high brightness monitors.

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

(Comparative Example 1)

Using a Gurereze PVA (9P75R) film (75 μm thick), dyeing at twice the draw ratio without dye stirring in a dye bath (35 ° C.) containing 0.3 wt% iodine and 3 wt% KI (concentration 3 wt%) Then, it extended | stretched 2.5 times in the crosslinking bath (50 degreeC) containing boric acid (concentration 6wt%), and extended | stretched with the total draw ratio 5 times (thickness 28 micrometers). It is a conventional method to dye a solution without stirring.

Then, it dried in the dryer of 60 degreeC, produced the polarizer, and after that, the TAC (triacetylcellulose) film was bonded together using the adhesive agent, and the polarizing plate was produced. The transmittance / polarization degree of the obtained polarizing plate was 41.5% / 99.95%.

(Example 1)

A polarizing plate was produced in the same manner as in Comparative Example 1 except that the bath solution of the dyeing bath was stirred using water flow (2 m / sec). At this time, the water flow did not directly contact the PVA film. The transmittance / polarization degree of the obtained polarizing plate was 41.6% / 99.94%.

(Evaluation method 1 of stain of polarizing plate)

In the dark room, on the backlight of illuminance 33000 lux, the two polarizing plates to be evaluated were placed so that the polarization axis was orthogonal and checked from the front and oblique directions to see whether streaky spots were visible with the polarization axis in the vertical direction (stretching direction).

(Evaluation method 2 of stain of polarizing plate)

After peeling the upper and lower polarizing plates bonded to the liquid crystal cell of a commercially available LCD monitor (300 candela), and bonding the polarizing plates to be evaluated up and down using a pressure-sensitive adhesive, the display of the monitor is displayed in black, and the viewing angle of the monitor is in the front and diagonal directions. Then, it confirmed whether the stripe-shaped unevenness was seen in the perpendicular direction (stretching direction) with the polarizing axis of a polarizing plate.                     

(Evaluation method 3 of stain of polarizing plate)

In the dark room, one polarizing plate to be evaluated was placed on a backlight having an illuminance of 33000 lux, and from the front and oblique directions, it was checked whether streaks-shaped stains were visible to the naked eye in the direction perpendicular to the polarization axis (stretching direction).

The results are shown in Table 1.

 Evaluation method 1 presence or absence of stain  Evaluation method 2 presence or absence of stain  Evaluation method 3 presence or absence of stain  Comparative Example 1  There is dirt  There is dirt  No stain  Example 1  No stain  No stain  No stain

As can be seen from Table 1, in the polarizing plate alone, there were no stains in both the polarizing plate (Comparative Example 1) dyed without stirring the dye solution and the dyed plate polarizing plate (Example 1) while stirring. However, in the orthogonal state, since Example 1 stirred the dyeing solution, neither the dyeing stain nor the display stain was not seen, but since the comparative example 1 did not stir the dyeing solution, neither the dyeing stain nor the display stain were seen.

As described above, in the method for producing a polarizing plate of the present invention, when the polyvinyl alcohol (PVA) film is dyed, the dye bath temperature is 0.02 wt% or more in a dye bath having a dichroic nature. The polarizing plate used for LCD which improved the display unevenness | dye resulting from dyeing stain can be manufactured by dyeing with 15 to 50 degreeC or less, the draw ratio in a bath being 5 times or less, and stirring the bath liquid in a bath.

Claims (15)

The polyvinyl alcohol (PVA) film is dyed with a dichroic dye or iodine, crosslinked with a crosslinking agent, stretched during or before these processes, and after drying, the TAC (triacetyl cellulose) film serving as a protective layer is double-sided. Or in the method of bonding to one side and manufacturing a polarizing plate, In a dyeing bath having a dichroic dye or iodine concentration of 0.02 wt% or more and 1.0 wt% or less and an iodide concentration of 0.01 to 15 wt%, the temperature of the dye bath is 15 ° C. or more and 50 ° C. or less, and the dye bath The stretching ratio in this is 1 times or more and 5 times or less, and it dyes, stirring the bath liquid in a dyeing bath, and makes it stir so that water stream may not directly contact a PVA film, It is characterized by the above-mentioned. delete The method for producing a polarizing plate according to claim 1, wherein the dyeing bath contains 2 to 10 wt% of a crosslinking agent. 2. The stirring according to claim 1, wherein the stirring is performed by stirring with a rotary blade, stirring by water flow, stirring by ultrasonic waves, stirring by air blowing into the bath, stirring by water flow perpendicular to the stretching direction, and opposite to the stretching direction. It is at least one stirring selected from stirring by the water flow to the polarizing plate, The manufacturing method of the polarizing plate characterized by the above-mentioned. The method for producing a polarizing plate according to claim 1, wherein before the dyeing step, swelling in a swelling bath containing water, a humidity control treatment, or stretching under dry conditions are performed. delete The method of manufacturing a polarizing plate according to claim 1, wherein the draw ratio in said dyeing bath is 2 to 5 times. The reflection type polarizing plate which bonded the reflecting plate to the polarizing plate manufactured by the method in any one of Claims 1, 3-5, and 7. The semi-transmissive reflecting plate type polarizing plate which bonded the transflective reflecting plate to the polarizing plate manufactured by the method in any one of Claims 1, 3-5, and 7. The elliptic polarizing plate which bonded the retardation plate to the polarizing plate manufactured by the method in any one of Claims 1, 3-5, and 7. The circular polarizing plate which bonded the (lambda) plate to the polarizing plate manufactured by the method in any one of Claims 1, 3-5, and 7. The polarizing plate which bonded the visual compensation film to the polarizing plate manufactured by the method of any one of Claims 1, 3-5, and 7. The polarizing plate which bonded together the brightness improving film using the adhesive agent or the adhesive to the polarizing plate manufactured by the method in any one of Claims 1, 3-5, and 7. A liquid crystal display device having a liquid crystal cell and a polarizing plate disposed on at least one side of the liquid crystal cell, wherein the polarizing plate is a reflective polarizing plate according to claim 8. A liquid crystal display device having a liquid crystal cell and a polarizing plate disposed on at least one side of the liquid crystal cell, wherein the polarizing plate is a transflective plate type polarizing plate according to claim 9.