JP2002006133A - Polarizer, polarizing plate, and liquid crystal display device using the same - Google Patents

Abstract

(57) [Problem] To provide a polarizer and a polarizing plate with small dimensional change, and a liquid crystal display device using the same that is free from color unevenness and color dropout. A polarizer has a shrinkage ratio per unit width of 4.0 N / cm or less when heated at 80 ° C. for 30 minutes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizer and a polarizing plate for use in a liquid crystal display device (hereinafter, may be abbreviated as LCD) with improved color unevenness and color loss, and a liquid crystal display device using the same. About.

[0002]

2. Description of the Related Art A polarizing plate used for an LCD is, for example, a dyeing step of dyeing a polyvinyl alcohol (hereinafter sometimes abbreviated as PVA) film with dichroic iodine or a dichroic dye. It is manufactured by drying after a cross-linking step of cross-linking with an acid, borax, or the like, and a stretching step of uniaxial stretching, and laminating with a protective layer such as a triacetyl cellulose (hereinafter sometimes abbreviated as TAC) film. . The steps of dyeing, crosslinking, and stretching do not need to be performed separately, and may be performed simultaneously, and the order of the steps may be arbitrary.

[0003] LCDs are used in personal computers and the like.
In recent years, the demand has rapidly increased. The use of LCDs is expanding, and in recent years, LCDs are also being used for monitors.

However, since the shrinking force in the absorption axis direction of the conventional polarizer is larger than 4.0 N / cm, when the polarizer or the polarizing plate using the same is left under heating, a dimensional change occurs, and the liquid crystal display When used in an apparatus, there has been a problem that defects such as color unevenness and color loss occur.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned conventional problems, the present invention reduces the dimensional change of a polarizer and a polarizing plate due to heating, and reduces color unevenness and color loss when used in a liquid crystal display device. It is an object of the present invention to provide a polarizer, a polarizing plate, and a liquid crystal display using the same, which suppress or eliminate the disadvantages described above.

[0006]

To achieve the above object, the polarizer of the present invention has a shrinkage force in the direction of the absorption axis per unit width of 4.0 N / cm or less when heated at 80 ° C. for 30 minutes. There is a feature.

The polarizer of the present invention has a thickness of 18 μm by stretching a polyvinyl alcohol film.
It is preferable to set the following.

The polarizer of the present invention is preferably produced by stretching a polyvinyl alcohol film having a thickness of 60 μm or less.

Further, the polarizing plate of the present invention has at least one selected from the group consisting of a protective film, a retardation plate, a reflecting plate, a semi-transmitting plate, a compensating plate and a brightness improving film on both surfaces or one surface of the polarizer. It is characterized in that the two are stuck together.

Further, a liquid crystal display device according to the present invention is characterized in that the polarizer or the polarizing plate is used.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The shrinkage force of the polarizer in the direction of the absorption axis is adjusted to 4.0 N / cm by adjusting the stretching method and the crosslinking method of PVA.
By doing so, a dimensional change under heating can be suppressed. The method of producing a polarizer having a shrinkage force of 4.0 N / cm or less is not particularly limited. For example, PVA is stretched at a low speed of 2 m / min or less in water, and crosslinking with a crosslinking agent is performed after stretching the PVA in water. First, the PVA is first stretched in the horizontal direction and then in the vertical direction. After the PVA is stretched, the operation of relaxing the stress is performed one or more times. The PVA having a thickness of 60 μm or less is used as a raw material. And reducing the internal stress of the polarizer by using the above methods to reduce the thickness of the polarizer to 18 μm or less.

However, the contraction force referred to here is a width of 20 m.
When a polarizer having a length of 50 mm and a length of 50 mm is heated at 80 ° C., it is a value obtained by converting the magnitude of the force of the polarizer shrinking in the absorption axis direction 30 minutes after the start of heating, per unit width. For the measurement, a polarizer having a width of 20 mm is sandwiched between two chucks having one fixed and the other having a force gauge so that the distance between the chucks is 50 mm (in the direction of the absorption axis), and continuously heated at 80 ° C. for 30 minutes. When reading, the value indicated by the force gauge was read.

The basic structure of the polarizing plate used in the present invention is as follows.
On one or both sides of a polarizer made of a dichroic substance-containing polyvinyl alcohol-based polarizing film or the like, a transparent protective film serving as a protective layer was bonded via an appropriate adhesive layer, for example, an adhesive layer made of a vinyl alcohol-based polymer or the like. Consist of things.

As a polarizer (polarizing film), for example, a dichroic substance composed of iodine, a dichroic dye or the like may be used on a film composed of a suitable vinyl alcohol-based polymer according to the related art 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 degree of polarization 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 the front and back sides.

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

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 amount of the transparent fine particles to be used is generally 2 to 70 parts by mass, particularly 5 to 50 parts by mass per 100 parts by mass 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 such a layer, 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 or oxalic acid. Such an adhesive layer can be formed as a coating and drying layer of an aqueous solution or the like. When the aqueous solution is prepared, other additives or a catalyst such as an acid can be blended as necessary.

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. Elliptically polarizing plate or circularly polarizing plate, the polarizing plate comprising the polarizer of the present invention and the protective layer described above, and a polarizing plate further laminated with a viewing angle compensation film, or the polarizer of the present invention and the protective layer described above And a brightness enhancement film Polarizing plates are stacked is preferable.

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 can be visually recognized. It is possible to form a liquid crystal display device of a type that reflects and reflects incident light from the side (display side), and has an advantage that a built-in light source such as a backlight can be omitted and the liquid crystal display device can be easily made thin. .

The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is provided on one side of the polarizing plate via the transparent protective film or the like as necessary. Specific examples thereof include a transparent protective film that has been matted as necessary, and a reflective layer formed by attaching a foil or a vapor-deposited film made of a reflective metal such as aluminum on one surface.

Further, a reflective polarizing plate having a reflective layer reflecting the fine uneven structure on the above-mentioned transparent protective film containing fine particles and having a fine uneven structure on the surface may also be used. The reflection layer having the fine surface irregularity structure has the advantage of diffusing incident light by irregular reflection, preventing directivity and glaring appearance, and suppressing unevenness in brightness and darkness. 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 carried out by a method of directly attaching to the surface of the protective film.

The reflecting plate may 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 the method in which the reflecting plate is directly attached to the transparent protective film of the polarizing plate. it can. 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 a transflective reflective layer such as a half mirror that reflects and transmits light on the reflective layer. The transflective polarizing plate is usually provided on the back side of the liquid crystal cell, and when a liquid crystal display device or the like is used in a relatively bright atmosphere,
An image is displayed by reflecting the incident light from the viewing side (display side). In a relatively dark atmosphere, the image is displayed using a built-in light source such as a backlight built in the back side of the transflective polarizing plate. A liquid crystal display device or the like of a type that displays the same can be formed. That is, the transflective polarizing plate can save energy for 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 elliptically polarizing plate or a circularly 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 elliptically or circularly polarized light, or changing elliptically or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light, a retardation plate or the like is used. A so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes into elliptically polarized light or circularly polarized light, or changes elliptically polarized light or circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used to change the polarization direction of linearly polarized light.

The elliptically polarizing plate is effective for compensating for coloring (blue or yellow) caused by the birefringence of the liquid crystal layer of a super twisted nematic (STN) type liquid crystal display device to make a black and white display without the coloring. Used for Further, the one in which the three-dimensional refractive index is controlled is preferable because coloring which occurs when the screen of the liquid crystal display device is viewed from an oblique direction can be compensated (prevented). 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.

Specific examples of the retardation plate include birefringence obtained by stretching a film made of an appropriate polymer such as polycarbonate, polyvinyl alcohol, polystyrene, polymethyl methacrylate, polypropylene, other polyolefin, polyarylate, or polyamide. And an alignment film of a liquid crystal polymer and a film in which an alignment layer of a liquid crystal polymer is supported by a film. 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 liquid crystal polymer obliquely oriented. And the like.

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

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

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. For a normal retardation plate, a polymer film having birefringence uniaxially stretched in the plane direction is used, whereas a retardation plate used as a viewing angle compensation film is biaxially stretched in the plane direction. Such as a polymer film having birefringence,
A bidirectionally stretched film such as an obliquely oriented polymer film having a controlled refractive index in the thickness direction, which is uniaxially stretched in the plane direction and also stretched in the thickness direction, is used. 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. Oriented ones are exemplified. 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,
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. That is, 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 polarized light. Is absorbed by
Does not pass through the polarizer. That is, although it depends on the characteristics of the polarizer used, about 50% of the light is absorbed by the polarizer, and accordingly, the amount of light that can be used for liquid crystal image display and the like decreases, and the image becomes darker. The brightness enhancement film is once reflected by the brightness enhancement film without causing the light having the polarization direction to be absorbed by the polarizer to enter the polarizer,
Further, reversing the light through the reflection layer or the like provided on the rear side and re-injecting the light to the brightness enhancement plate is repeated, so that the polarization direction of the light reflected and inverted between the two can pass through the polarizer. Since only the polarized light having the proper polarization direction is transmitted through the brightness enhancement film and supplied to the polarizer, light from a backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened. You can.

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

Therefore, in the brightness enhancement film of the type that transmits the linearly polarized light having the predetermined polarization axis, the transmitted light is directly incident on the polarization plate with the polarization axis aligned, thereby suppressing the absorption loss by the polarization plate and improving the efficiency. It can transmit well. 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. By using a quarter-wave plate as the retardation plate, circularly polarized light can be converted to linearly polarized light.

A retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is, for example, a retardation layer that functions as a quarter-wave plate for monochromatic light 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 is also
By combining two or more layers having different reflection wavelengths and having an arrangement structure in which two or more layers are overlapped, it is possible to obtain one that reflects circularly polarized light in a wide wavelength range such as a visible light region,
Based on this, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate of the present invention may be formed by laminating a polarizing plate and two or three or more optical layers as in the above-mentioned polarized light separating type polarizing plate. Therefore, a reflective elliptically polarizing plate or a transflective elliptically polarizing plate obtained by combining the above-mentioned reflective polarizing plate, semi-transmissive polarizing plate and retardation plate may be used. The optical member in which two or three or more optical layers are laminated can also be formed by a method in which the optical members are sequentially laminated separately in a manufacturing process of a liquid crystal display device or the like, but an optical member in which the optical members are laminated in advance. Is advantageous in that it is superior in quality stability, assembling workability, and the like, and can improve the manufacturing efficiency of a liquid crystal display device and the like. Note that an appropriate bonding means such as an adhesive layer can be used for lamination.

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. In particular, from the viewpoint of preventing foaming and peeling phenomena due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of liquid crystal cell warpage, and, in view of the formability of a liquid crystal display device having high quality and excellent durability, the moisture absorption rate is high. It is preferable that the pressure-sensitive adhesive layer is low and has excellent heat resistance. Further, 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 forming the polarizing plate and the optical member are made of, for example, salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds and cyanoacrylate compounds. Compounds having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorbent such as a compound or 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 optional, and for example, an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a twisted nematic type or a super twisted nematic type, etc. A liquid crystal cell of any type may be used.

When polarizing plates and 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.

[0046]

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

Example 1 PVA having an average degree of polymerization of 1700
An aqueous solution prepared by dissolving the powder in pure water so as to have a concentration of 10% by mass was applied on a polyester film.
After drying for 2 hours, drying was further performed at 130 ° C. for 30 minutes to obtain a PVA film having a thickness of 40 μm. The obtained film was swollen with warm water at 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched twice. Next, in a 4% by mass aqueous boric acid solution at 50 ° C., the film is stretched so that the total stretching ratio becomes 3 times,
It was immersed in a water bath at 30 ° C., washed with water, and dried at 50 ° C. for 4 minutes to obtain a 13 μm-thick polarizer. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to be 0.35% by mass so that the transmittance of the polarizer would be 44%.

Example 2 PVA having an average degree of polymerization of 1700
An aqueous solution prepared by dissolving the powder in pure water so as to have a concentration of 10% by mass was applied on a polyester film.
After drying for 2 hours, drying was further performed at 130 ° C. for 30 minutes to obtain a 55 μm thick PVA film. The obtained film was swollen with warm water at 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched twice. Next, in a 4% by mass aqueous boric acid solution at 50 ° C., the film is stretched so that the total stretching ratio becomes 3 times,
It was immersed in a water bath at 30 ° C., washed with water, and dried at 50 ° C. for 4 minutes to obtain a polarizer having a thickness of 18 μm. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to 0.33% by mass of iodine so that the transmittance of the polarizer became 44%.

(Embodiment 3) The thickness of 40 μm obtained in Embodiment 1
Swelled with warm water of 30 ° C. for 1 minute,
It was immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 0 ° C. and stretched three times. Then, in a 4% by mass aqueous solution of boric acid at 50 ° C., the film is stretched so that the total stretching ratio becomes 5.5 times, immersed in a water bath at 30 ° C., and washed with water.
After drying for 4 minutes, a polarizer having a thickness of 9 μm was obtained. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to be 0.37% by mass so that the transmittance of the polarizer would be 44%.

Comparative Example 1 PVA having an average degree of polymerization of 1700
An aqueous solution prepared by dissolving the powder in pure water so as to have a concentration of 10% by mass was applied on a polyester film.
After drying for 2 hours, drying was further performed at 130 ° C. for 30 minutes to obtain a PVA film having a thickness of 75 μm. The obtained film was swollen with warm water at 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched twice. Next, the film is stretched in a 4% by mass aqueous solution of boric acid at 50 ° C. so that the total stretching ratio becomes 3 times.
Immerse in a water bath at 0 ° C, wash with water, dry at 50 ° C for 4 minutes,
A polarizer having a thickness of 31 μm was obtained. The concentration of the aqueous solution of potassium iodide / iodine (mass ratio 10: 1) was set to 0.27% by mass of iodine so that the transmittance of the polarizer became 44%.

Comparative Example 2 PVA having an average degree of polymerization of 1700
An aqueous solution prepared by dissolving the powder in pure water so as to have a concentration of 10% by mass was applied on a polyester film.
After drying for 2 hours, drying was further performed at 130 ° C. for 30 minutes to obtain a PVA film having a thickness of 75 μm. The obtained film was swollen with warm water of 30 ° C. for 1 minute, immersed in an aqueous solution of potassium iodide / iodine (mass ratio 10: 1) at 30 ° C., and stretched three times. Then, the film is stretched in a 4% by mass aqueous solution of boric acid at 50 ° C. so that the total stretching ratio becomes 5.5 times, immersed in a 30 ° C. water bath, washed with water, dried at 50 ° C. for 4 minutes, and dried. A polarizer having a thickness of 26 μm was obtained. Potassium iodide /
The concentration of the aqueous solution of iodine (mass ratio 10: 1) was set to 0.3% by mass of iodine so that the transmittance of the polarizer became 44%.

(Evaluation) First, the shrinkage of the polarizers of Examples 1 to 3 and Comparative Examples 1 and 2 in the absorption axis direction per unit width when heated at 80 ° C. for 30 minutes was measured. That is,
The polarizer was cut into a length of 70 mm and a width of 20 mm so that the direction in which the polarizer was stretched became longer, and one was fixed, and the other was fixed with two force gauges so that the distance between the chucks was 50 mm. Scissors, 30 at 80 ° C
By reading the value indicated by the force gauge when heating was performed continuously for one minute, the contraction force per unit width was measured.

Next, an elastic modulus of 3.4 was set on both sides of the polarizer.
A 3GPa triacetylcellulose film was bonded using a PVA-based adhesive to prepare a polarizing plate. The dimensional change after heating this polarizing plate at 70 ° C. for 48 hours was measured, and the dimensional change rate (%) in the stretching axis direction was calculated.

For evaluation of color unevenness and color loss, the polarizing plate prepared above was vertically oriented so that the absorption axis direction was 45 °.
mm and 200 mm wide. This polarizing plate is attached to both sides of the glass plate so that the polarizing directions are orthogonal to each other using a 25 μm-thick acrylic adhesive composed of 95 parts by mass of butyl acrylate and 5 parts by mass of acrylic acid, and the polarizing plate is placed at 70 ° C. for 48 hours. The state of color unevenness after heating was visually confirmed. In the evaluation, a color having less color unevenness was ranked as “○”, a color with more color unevenness was rated as “×”, and an intermediate color was rated as “△”.

Table 1 shows the above results.

[0056]

[Table 1]

As is evident from Table 1, Examples 1 to 3 of the present invention, in which the shrinkage force of the polarizer is 4.0 N / cm or less, have a dimensional change rate, color unevenness, and color in comparison with Comparative Examples 1 and 2. It turns out that there are few dropouts. Further, it can be seen that Examples 1 to 3 of the present invention in which the thickness of the PVA film before stretching was 60 μm or less and the thickness of the polarizer was 18 μm or less had the same effect.

[0058]

As described above, the polarizer of the present invention is
By setting the shrinkage force per unit width when heated at 80 ° C. for 30 minutes to 4.0 N / cm or less, a polarizing plate with little dimensional change can be provided, and a liquid crystal display free from color unevenness and color loss The device can be provided and its industrial value is great.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G09F 9/00 313 G09F 9/00 313 324 324 // C08L 29:04 C08L 29:04 (72) Inventor Seiichi Kusumoto 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Yoichiro Sugino 1-2-1, Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Naofumi Mihara 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation (72) Inventor Kazuki Tsuchimoto 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H049 BA02 BA06 BA27 BB13 BB33 BB43 BB63 BB65 BC03 BC22 2H091 FA08X FA08Z FA11X FA11Z FA15Z FB02 LA15 LA30 4F071 AA29 AF61 AH19 BA02 BB02 BB07 BB08 BC01 BC12 5G435 AA04 BB12 FF0 3 FF05 KK07

Claims (6)

[Claims] 1. A polarizer having a shrinkage force in the direction of an absorption axis per unit width of 4.0 N / cm or less when heated at 80 ° C. for 30 minutes. 2. The polarizer according to claim 1, wherein the thickness is reduced to 18 μm or less by stretching the polyvinyl alcohol film. 3. The polarizer according to claim 1, which is produced by stretching a polyvinyl alcohol film having a thickness of 60 μm or less. 4. A protective film, a retardation plate, a reflection plate, a protective film, on both surfaces or one surface of the polarizer according to claim 1.
A polarizing plate to which at least one selected from the group consisting of a semi-transmissive plate, a compensating plate, and a brightness enhancement film is attached. 5. A liquid crystal display device using the polarizer according to claim 1. 6. A liquid crystal display device using the polarizing plate according to claim 4.