JP2001296426A - Method for manufacturing polarizing plate and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate without a record disc groove-like projecting and recessing shape on a surface of a protective layer caused by stretching of a polarizing film, with a clear reflection image when observed by reflection, thereby improving appearance, and a liquid crystal display device. SOLUTION: In the case a polarizer with >=35% transmissivity and >=90% polarization degree is obtained, the water content of the polarizer is kept in 5-30% range while a protective layer is stuck on one or both surfaces of the polarizer (provided that a method for measuring the water content of the polarizer is based on the equation the water content (%) of the polarizer = [(A-B)/B]×100 using the polarizer's weight before sticking (A) and the weight after keeping the polarizer in a drier under 120 deg.C for seven hours (B)).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polarizing plate used for a liquid crystal display device (hereinafter, may be abbreviated as LCD) and a liquid crystal display device provided with the polarizing plate obtained by the method. More specifically, a method of manufacturing a polarizing plate, in which no groove-like unevenness of a record due to stretching of a polarizing film is generated on a surface of a protective layer, a reflected image is clear even when viewed by reflection, and an appearance problem is improved. And a liquid crystal display device.

[0002]

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

[0003] A polarizing plate is prepared by dyeing a PVA film with dichroic iodine or a dye and then crosslinking the film with boric acid or borax. In addition, uniaxial stretching is performed in the dyeing step and the crosslinking step. This stretching may be performed during the step, or may be performed before or after the step. After the dyeing step and the cross-linking step, it is usually dried using a drier or the like, and bonded to a protective layer such as a triacetyl cellulose (TAC) film using an adhesive.

A polarizing plate used for a liquid crystal display device is
It is required to increase both the transmittance and the degree of polarization.
In order to increase both the transmittance and the degree of polarization of the polarizing plate, it is necessary to increase the stretching ratio of a PVA (polyvinyl alcohol) film that is a raw material of the polarizing plate. However, PVA
When the stretching ratio is high, groove-like irregularities of the record are likely to occur in the stretching direction on the surface of the polarizer, which is not preferable in appearance. In addition, the groove-shaped unevenness of the record also affects the film portion such as TAC or polyethylene terephthalate (PET) to be bonded as a protective layer, so that the groove-shaped unevenness of the record is generated even from above the protective layer. When viewed by reflection, the reflected image appears blurred, which is a problem in appearance.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention does not cause groove-like irregularities of a record due to stretching of a polarizing film on the surface of a protective layer, and can be viewed by reflection. It is an object of the present invention to provide a method for manufacturing a polarizing plate and a liquid crystal display device in which a reflected image is clear and an appearance problem is improved.

[0006]

In order to achieve the above object, a method of manufacturing a polarizing plate according to the present invention is a method of manufacturing a polarizer having a transmittance of 35% or more and a degree of polarization of 90% or more. The water content of the polarizer when bonded as a protective layer to one or both surfaces is 5% to 30% (however, the method of measuring the water content of the polarizer is described as follows: From the weight (A) and the weight (B) of the polarizer after placing the polarizer in a dryer at 120 ° C. for 7 hours, the water content (%) of the polarizer = [(AB) / B] × Determine with 100.). If the water content of the polarizer is less than 5%, there is a problem that the polarizer becomes hard, irregularities on the groove of the record are generated, and a crosslinking agent is more easily precipitated from the polarizer, and the appearance defect is increased. When the water content exceeds 30%, the water content becomes high, and adhesion failure is likely to occur when bonding with a protective layer such as TAC. There is a disadvantage that unevenness occurs due to the

In the above, a more preferable range of the water content of the polarizer is 9 to 27%.

[0008] In the above method, the surface roughness in the direction perpendicular to the stretching axis direction is 0.04 based on the center line average roughness.
It is preferably not more than μm. When the thickness exceeds 0.04 μm, it is easy to visually confirm unevenness. That is, unevenness is more noticeable.

In the present invention, a reflective plate or a semi-transmissive reflective plate can be bonded to the polarizer produced by the above method to form a reflective polarizer or a transflective polarizer.

An elliptical or circular polarizing plate can also be formed by laminating a retardation plate or a λ plate to the polarizing plate manufactured by the above method.

Further, a polarizing plate can be formed by laminating a viewing angle compensation film to the polarizing plate manufactured by the above method.

A polarizing plate can also be formed by bonding a brightness enhancement film to the polarizing plate manufactured by the above method using an adhesive or a pressure-sensitive adhesive.

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

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the process for producing a polarizing plate of the present invention, a PVA film, which is a raw material of the polarizing plate, is subjected to swelling, dyeing, stretching, cross-linking, drying, etc. to obtain a polarizer having a polarizing function. Thereafter, a film such as TAC or PET is attached to the polarizer using an adhesive or a pressure-sensitive adhesive as a protective layer to obtain a polarizing plate.

In the manufacturing process of the polarizer, swelling, dyeing,
In the four steps of stretching and crosslinking, the order of the steps is not particularly limited, and the four steps may be performed at the same time even when two to four steps are performed simultaneously.

In the present invention, as a method for eliminating the occurrence of groove-shaped unevenness of a record generated on a polarizer or a polarizing plate,
By setting the water content of the polarizer to 5% to 30% when the polarizer and the protective layer are bonded to each other, it was possible to solve the groove-like unevenness of the record generated on the polarizing plate.

Generally, the PVA film is swollen,
The polarizer obtained by dyeing, stretching, cross-linking, drying, etc., is once wound up in a roll shape. After that, the moisture content of the polarizer is adjusted by humidifying the polarizer, and then the TAC film is protected. It is also possible to carry out by a continuous production method of laminating the layers.

The method for producing a polarizing film generally includes a "dyeing step" in which a PVA film is dyed in a bath containing iodine or a dye having dichroic properties, and a process such as boric acid or borax. In a bath containing a PVA cross-linking agent, a "cross-linking step" in which cross-linking is performed and a "stretching step" in which PVA is drawn can be roughly classified into three steps. The “stretching step” is usually performed at the same time as the “dyeing step” and the “crosslinking step”, but may be performed in another step. Further, the dyeing step and the crosslinking step may be performed simultaneously. After the above three steps, the polarizing film
It is manufactured by drying and laminating a film such as a triacetyl cellulose (TAC) film or a polyethylene terephthalate (PET) film, which serves as a protective layer, on one side or both sides.

As the polarizer (polarizing film), for example, a dichroic substance made of iodine or a dichroic dye or the like may be used on a film made of a suitable vinyl alcohol-based polymer such as polyvinyl alcohol or partially formalized polyvinyl alcohol. , A suitable treatment such as a stretching treatment, a cross-linking treatment, or the like is performed in an appropriate order or manner, and an appropriate material that transmits linearly polarized light when natural light is incident thereon can be used. In particular, those having excellent light transmittance and polarization degree are preferable.

An appropriate transparent film can be used as a protective film material serving as a transparent protective layer provided on one side or both sides of a polarizer (polarizing film). As an example of the polymer, an acetate resin such as triacetylcellulose is generally used, but is not limited thereto.

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 different polymers or the like may be used on both sides.

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 treatment, an anti-reflection treatment, a treatment for preventing sticking, diffusion or anti-glare, or the like may be performed. The hard coat treatment is performed for the purpose of preventing the surface of the polarizing plate from being scratched. For example, a hardened film excellent in hardness and slipperiness by an appropriate ultraviolet curable resin such as a silicone resin is coated on the surface of the transparent protective film. Can be formed.

On the other hand, the anti-reflection treatment is performed for the purpose of preventing reflection of external light on the polarizing plate surface, and can be achieved by forming an anti-reflection film or the like according to the related art. In addition, sticking prevention is for the purpose of preventing adhesion with the adjacent layer,
The anti-glare treatment is performed for the purpose of preventing external light from being reflected on the surface of the polarizing plate and hindering the visibility of light transmitted through the polarizing plate, and is, for example, a roughening method using a sandblasting method or an embossing method. 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 method of mixing transparent fine particles.

Examples of the transparent fine particles include silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, and antimony oxide having an average particle size of 0.5 to 20 μm. Fine particles may be used, or organic fine particles composed of crosslinked or uncrosslinked polymer particles or the like may be used. The use amount of the transparent fine particles 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 anti-glare 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 may also serve as a diffusion layer (such as a viewing angle compensation function) for diffusing light transmitted through the polarizing plate to increase the viewing angle.
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 these layers, separately from the transparent protective layer.

In the present invention, 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 comprising a vinyl alcohol-based polymer or boric acid Or borax,
It can be carried out via an adhesive comprising at least a water-soluble cross-linking agent of a vinyl alcohol-based polymer such as glutaraldehyde, melamine, and oxalic acid. Such an adhesive layer can be formed as a coating and drying layer of an aqueous solution, but when preparing the aqueous solution, if necessary, other additives,
A catalyst such as an acid can also be blended.

The polarizing plate according to 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 reflector, a transflector, a retardation plate (including a λ plate such as a 波長 wavelength plate and a 板 wavelength plate), a viewing angle compensation film, and a brightness enhancement film One or two or more appropriate optical layers that may be used for forming a liquid crystal display device or the like can be used. In particular, a polarizing plate including the polarizer of the present invention and the protective layer described above includes: Further, a reflection plate or a reflection type polarizing plate or a semi-transmission reflection type polarizing plate in which a transflective reflection plate is laminated, a retardation plate is further laminated on the above-mentioned polarizing plate comprising the polarizer of the present invention and a protective layer. An elliptical or circular polarizer, a polarizer comprising the polarizer and the protective layer of the present invention described above, and a polarizing plate further laminated with a viewing angle compensation film, or the polarizer and the protective layer of the present invention described above. Brightness enhancement film on the polarizing plate Polarizing plates are preferred.

The reflection plate will be described. The reflection plate is provided on a polarizing plate to form a reflection-type polarizing plate. The reflection-type polarizing plate is usually provided on the back side of a liquid crystal cell, and is visible. It is possible to form a liquid crystal display device of the type that reflects and reflects incident light from the side (display side), and has the advantage that the built-in light source such as a backlight can be omitted and the thickness of the liquid crystal display device can be easily reduced. .

The reflection type polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one side of the polarizing plate via the transparent protective film or the like as necessary. Incidentally, a specific example thereof includes a transparent protective film which has been subjected to a mat treatment as required, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum on one surface.

Further, there is a reflection type polarizing plate having a reflective layer reflecting the fine unevenness on the transparent protective film having a fine unevenness on the surface by containing fine particles. The reflective layer with a fine surface irregularity structure diffuses the incident light by irregular reflection to prevent directivity and glare,
It has an advantage that light and dark unevenness can be suppressed. The formation of the reflective layer of the fine uneven structure reflecting the fine uneven structure on the surface of the transparent protective film is performed 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 performed by a method of directly attaching to the surface of the protective film.

The reflecting plate can be used as a reflecting sheet in which a reflecting layer is provided on an appropriate film conforming to the transparent protective film, instead of directly attaching the reflective plate to the transparent protective film. . Since the reflection layer of the reflection plate is usually made of a metal, the use form in which the reflection surface is covered with a film, a polarizing plate, or the like is intended to prevent a decrease in the reflectance due to oxidation and to maintain the initial reflectance for a long time. It is preferable from the viewpoint of avoiding separately providing a protective layer.

The transflective polarizing plate can be obtained by forming the reflective layer as a transflective reflective layer such as a half mirror that reflects and transmits light. A transflective polarizing plate is usually provided on the back side of a liquid crystal cell. When a liquid crystal display device or the like is used in a relatively bright atmosphere, an image is displayed by reflecting incident light from the viewing side (display side). In a relatively dark atmosphere, it is possible to form a liquid crystal display device that displays an image using a built-in light source such as a backlight built in the back side of a transflective polarizing plate. That is, the transflective polarizing plate can save energy for use of a light source such as a backlight in a bright atmosphere, and can be used for forming a liquid crystal display device or the like that can be used with a built-in light source even in a relatively dark atmosphere. Useful.

Next, an elliptic or circular polarizing plate in which a retardation plate is further laminated on the above-mentioned polarizing plate comprising the polarizer of the present invention and a protective layer will be described.

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

The elliptically polarizing plate is effectively used for compensating for coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of the STN type liquid crystal display device to provide a monochrome display without the coloring. Further, the one in which the three-dimensional refractive index is controlled can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed from an oblique direction, and is preferable. 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.

Incidentally, as a specific example of the retardation plate,
Birefringent film, liquid crystal polymer alignment film, liquid crystal polymer alignment film obtained by stretching a film made of a suitable polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene and other polyolefins, polyarylate and polyamide. One in which the layer is supported by a film is exemplified. Examples of the obliquely oriented film include, for example, 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 shrinking treatment under the action of the shrinkage force caused by heating, or a film obtained by obliquely aligning a liquid crystal polymer. Is raised.

Next, a polarizing plate in which a viewing angle compensation film is further laminated on the above-described polarizing plate comprising the polarizer of the present invention and a protective layer will be described.

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 not in a direction perpendicular to the screen but in a slightly oblique direction.

As such a viewing angle compensation film, a film obtained by coating a discotic liquid crystal on a triacetyl cellulose film or the like, or a retardation plate is used. Whereas a polymer film having a birefringence in which a normal retardation plate is uniaxially stretched in the plane direction is used, a retardation plate used as a viewing angle compensation film is a birefringent film which is biaxially stretched in the plane direction. Or a bidirectionally stretched film such as an obliquely oriented polymer film which is uniaxially stretched in the plane direction and stretched in the thickness direction and has a controlled refractive index in the thickness direction. As described above, for example, as described above, the heat-shrinkable film is adhered to the polymer film, and the polymer film is stretched or / and shrunk under the action of the heat-induced shrinkage force. And the like. As the raw material polymer for the retardation plate, the same polymer as the polymer described for the retardation plate is used.

A polarizing plate obtained by laminating a brightness enhancement film on the above-described polarizing plate comprising the polarizer of the present invention and a protective layer is as follows:
Usually, it is provided and used on the back side of the 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 via a reflection layer or the like provided on the rear side thereof and re-incident on the brightness enhancement plate, and a part or all of the light is transmitted as light of a predetermined polarization state to achieve brightness. The brightness can be improved by increasing the amount of light transmitted through the enhancement film and 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 and the like. In other words, when light is incident through a polarizer from the back side of a liquid crystal cell with a backlight or the like without using a brightness enhancement film, light having a polarization direction that does not coincide with the polarization axis of the polarizer is hardly generated. Is absorbed by
Does not pass through the polarizer. That is, although it differs depending on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer, and accordingly, the amount of light available for liquid crystal image display and the like decreases, 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. Repeatedly re-entering the brightness enhancement plate, the brightness enhancement film transmits the polarized light whose polarization direction has been changed so that the polarization direction of the light reflected and inverted between the two can pass through the polarizer. Since the light is supplied to the child, 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. The cholesteric liquid crystal layer, especially the cholesteric liquid crystal polymer oriented film or the one that supports the oriented liquid crystal layer on a film substrate, reflects either left-handed or right-handed circularly polarized light. Other appropriate light, such as one exhibiting a characteristic of transmitting other light, may be used.

Therefore, in the brightness enhancement film of the type that transmits linearly polarized light having the predetermined polarization axis, the transmitted light is incident on the polarization plate with the polarization axis aligned as it is, so that the absorption loss by the polarization plate can be suppressed and efficiently. Can be transmitted. On the other hand, a brightness enhancement film that transmits circularly polarized light, such as a cholesteric liquid crystal layer, can be directly incident on a polarizer.However, rather than suppressing absorption loss, the transmitted circularly polarized light is converted to linearly polarized light through a retardation plate. It is preferable to make the light incident on the polarizing plate. Incidentally, by using a quarter-wave plate as the retardation plate, circularly polarized light can be converted into 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 such as light having a wavelength of 550 nm. , For example, a method of superimposing a retardation layer functioning as a half-wave plate with the retardation layer exhibiting the above retardation characteristic. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one or more retardation layers.

The cholesteric liquid crystal layer also has a structure in which two or three or more cholesteric liquid crystal layers are overlapped with each other to reflect circularly polarized light in a wide wavelength range such as a visible light region. Thus, it is possible to obtain circularly polarized light transmitted in a wide wavelength range.

The polarizing plate of the present invention may be formed by laminating a polarizing plate and two or three or more optical layers like 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, semi-transmissive 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 layers sequentially in the manufacturing process of a liquid crystal display device or the like, those which are preliminarily laminated as an optical member are excellent in stability of quality and workability of assembly, etc. There is an advantage that the manufacturing efficiency of the device or the like can be improved. For the lamination, an appropriate adhesive means such as an adhesive layer can be used.

The polarizing plate or the optical member according to the present invention may be provided with an adhesive layer for bonding to another member such as a liquid crystal cell. The pressure-sensitive adhesive layer can be formed with an appropriate pressure-sensitive adhesive, such as an acrylic resin, according to the related art. Above all, from the viewpoint of preventing foaming and peeling phenomena due to moisture absorption, deterioration of optical characteristics due to difference in thermal expansion, prevention of liquid crystal cell warpage, and formation of a high quality and durable liquid crystal display device, the moisture absorption rate It is preferable that the pressure-sensitive adhesive layer has low heat resistance and excellent heat resistance. In addition, an adhesive layer or the like which contains fine particles and exhibits light diffusibility can be used. The adhesive layer may be provided on a necessary surface if necessary.For example, if mention is made of the protective layer of the polarizing plate comprising the polarizer and the protective layer of the present invention, if necessary, one or both surfaces of the protective layer May be provided with an adhesive layer.

When the adhesive layer provided on the polarizing plate or the optical member is exposed on the surface, it is preferable to temporarily cover the adhesive layer with a separator until practical use of the adhesive layer for the purpose of preventing contamination and the like. The separator is formed by a method of providing a release coat with a suitable release agent such as a silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide as necessary, on a suitable thin leaf according to the transparent protective film or the like. be able to.

The layers such as the polarizing film and the transparent protective film, the optical layer and the adhesive layer which form the polarizing plate and the optical member are made of, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound or a cyanoacrylate compound. Alternatively, a material having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorbing agent such as a nickel complex compound may be used.

The polarizing plate according to the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device is a transmission type or reflection type in which the polarizing plate according to the present invention is disposed on one side or both sides of a liquid crystal cell, or a transmission type or a reflection type.
It can be formed as a device having an appropriate structure according to the related art such as a dual-purpose type. Therefore, the liquid crystal cell forming the liquid crystal display device is arbitrary, and may be an appropriate type such as an active matrix driving type represented by a thin film transistor type, a simple matrix driving type represented by a twisted nematic type or a super twisted nematic type, and the like. A liquid crystal cell of a type may be used.

When polarizing plates or optical members are provided on both sides of the liquid crystal cell, they may be the same or different. Further, in forming the liquid crystal display device, one or more layers of appropriate components such as a prism array sheet, a lens array sheet, a light diffusing plate, and a backlight can be arranged at appropriate positions.

[0051]

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

Example 1 Kuraray PVA (9 × 75R)
S) using the first bath (an aqueous solution 30 of iodine and KI).
After stretching 3 times in the second bath (boric acid, KI aqueous solution 5)
(5 ° C.) to give a polarizer by stretching up to 6 times in total stretching ratio. Then, using a dryer and a humidifier, the temperature,
After adjusting the humidity, the air volume, and the time to adjust the moisture content of the polarizer to 6%, the TAC (triacetylcellulose) film and a PVA-based adhesive were used to produce a polarizing plate.

Example 2 Kuraray-made PVA (9 × 75R)
S) using the first bath (an aqueous solution 30 of iodine and KI).
After stretching 3 times in the second bath (boric acid, KI aqueous solution 5)
(5 ° C.) to give a polarizer by stretching up to 6 times in total stretching ratio. Then, using a dryer and a humidifier, the temperature,
After adjusting the humidity, the air volume, and the time to adjust the water content of the polarizer to 15%, the TAC (triacetylcellulose) film and a PVA-based adhesive were used to produce a polarizing plate.

Example 3 Kuraray-made PVA (9 × 75R)
S) using the first bath (an aqueous solution 30 of iodine and K1).
After stretching 3 times in the second bath (boric acid, KI aqueous solution 5)
(5 ° C.) to give a polarizer by stretching up to 6 times in total stretching ratio. Then, using a dryer and a humidifier, the temperature,
After adjusting the humidity, the air volume, and the time to adjust the moisture content of the polarizer to 26%, the polarizing plate was manufactured by laminating a TAC (triacetyl cellulose) film with a PVA-based adhesive.

Comparative Example 1 PVA manufactured by Kuraray (9 × 75R)
S) using the first bath (an aqueous solution 30 of iodine and KI).
C.), and stretched up to 6 times in a second bath (boric acid, KI aqueous solution at 55 ° C.) at a total stretching ratio of 6 times to obtain a polarizer. Then, using a dryer and a humidifier, adjust the temperature, humidity, air volume, and time to reduce the moisture content of the polarizer to 4%.
Then, a TAC (triacetyl cellulose) film and a PVA-based adhesive were used to produce a polarizing plate.

Comparative Example 2 PVA made by Kuraray (9 × 75R)
S) using the first bath (an aqueous solution 30 of iodine and KI).
C.), and stretched up to 6 times in a second bath (boric acid, KI aqueous solution at 55 ° C.) at a total stretching ratio of 6 times to obtain a polarizer. Then, using a dryer and a humidifier, adjust the temperature, humidity, air volume, and time to reduce the water content of the polarizer to 35%.
Then, a TAC (triacetyl cellulose) film and a PVA-based adhesive were used to produce a polarizing plate. However, when the moisture content is 35%, TAC
Due to the drying treatment at the time of laminating, unevenness occurred in the plane of the polarizing plate.

The above Examples 1-3 and Comparative Examples 1-2 were evaluated. As optical characteristics, the transmittance of a single substance and the degree of polarization were measured. The surface shape of the polarizing plate in the polarization axis direction (perpendicular to the stretching axis direction) was measured using a surface roughness profile measuring instrument (manufactured by Tokyo Seimitsu Co., Ltd.) using a center line average roughness (Ra) and an average interval of unevenness (Sm). Was examined. The presence or absence of streaks was confirmed by visual observation. The results are shown in Table 1 below.

[0058]

【table 1】

As is clear from Table 1, in Examples 2 to 3 of the present invention, the center line average roughness (Ra) of the surface roughness was small, the average interval (Sm) of unevenness was not measurable, and visual observation was performed. There was no streak as judged by. In Example 1, a thin streak could be slightly confirmed visually, but there was no problem in practical use.

On the other hand, in Comparative Example 1, since the humidity condition was outside the range of the present invention, the center line average roughness (R
a) was rough, the average interval of unevenness (Sm) was large, and there was a streak when judged by visual observation. In Comparative Example 2, the center line average roughness (Ra) of the surface roughness and the average interval of irregularities (S
m) was good, but the degree of polarization of the optical properties was poor, and further in-plane unevenness was observed, which was not preferable in appearance.

[0061]

As described above, the method for producing a polarizing plate of the present invention is a method for producing a polarizer having a transmittance of 35% or more and a degree of polarization of 90% or more.
The water content of the polarizer when bonding as a protective layer is 5%
By being about 30%, groove-like irregularities of the record due to stretching of the polarizing film do not occur on the surface of the protective layer,
It is possible to provide a method for manufacturing a polarizing plate and a liquid crystal display device in which a reflected image is clear even when viewed in reflection and the problem of appearance is improved.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Kazuki Tsuchimoto 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Senri Yoshikawa 1-1-1, Shimohozumi, Ibaraki-shi, Osaka No. 2 Nitto Denko Corporation (72) Inventor Seiichi Kusumoto 1-2-1 Shimohozumi, Ibaraki-shi, Osaka F-term (reference) 2H049 BA02 BA03 BA04 BA27 BA43 BB02 BB23 BB33 BB43 BB45 BB48 BB51 BB63 BB65 BC03 BC14 BC22 2H091 FA08X FA08Z FA11X FA14Z FA15Z FB02 FC02 FC03 GA13 HA07 HA10 HA11 LA30

Claims (7)

[Claims] 1. A method for producing a polarizer having a transmittance of 35% or more and a degree of polarization of 90% or more, wherein the water content of the polarizer when bonded as a protective layer to one or both surfaces of the polarizer is as follows:
A method for producing a polarizing plate, comprising 5% to 30%. (However, the method of measuring the water content of the polarizer is based on the weight of the polarizer before bonding (A) and the weight of the polarizer after placing the polarizer in a dryer at 120 ° C. for 7 hours (B). (Calculated as water content (%) of polarizer = [(AB) / B] × 100) 2. The method according to claim 1, wherein the surface roughness in the direction perpendicular to the stretching axis direction is 0.04 μm or less based on the center line average roughness. 3. A polarizing plate, wherein a polarizing plate or a semi-transmissive reflecting plate is bonded to the polarizing plate manufactured by the method according to claim 1 to form a reflective polarizing plate or a transflective polarizing plate. Manufacturing method. 4. A method for manufacturing a polarizing plate, comprising: attaching a retardation plate or a λ plate to the polarizing plate manufactured by the method according to claim 1 to form an elliptically or circularly polarizing plate. 5. A method for manufacturing a polarizing plate, comprising: attaching a viewing angle compensation film to the polarizing plate manufactured by the method according to claim 1; and forming a polarizing plate. 6. A method for manufacturing a polarizing plate, comprising: bonding a brightness enhancement film to the polarizing plate manufactured by the method according to claim 1 using an adhesive or a pressure-sensitive adhesive to form a polarizing plate. 7. A liquid crystal display device comprising a polarizing plate manufactured by the method according to claim 1 on at least one side of a liquid crystal cell.