JP2003215335A - Polarizing plate and liquid crystal display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate and a liquid crystal display which solves problems on display on a panel by controlling the thickness of a polarizer relative to the thickness of a cell substrate and is lightweight, thin and less liable to warpage of the panel and uneven display. <P>SOLUTION: The polarizing plate is obtained by laminating a polymeric protective film on at least one surface of a polarizer consisting of a hydrophilic polymer film, wherein the thickness of the polarizer is 1 to 20 μm and the thickness d1 of the polarizer is adjusted so as to satisfy the relation of d1/d2≤0.044 to the thickness d2 of one liquid crystal cell substrate to which the polarizing plate is attached. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

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

[0002]

2. Description of the Related Art LCDs are used in personal computers and the like, and the demand for them has been rapidly increasing in recent years. However, in recent years, liquid crystal displays have been claimed to be lighter and thinner.
The liquid crystal panel is very thin. As a point of thinning, the first point is to reduce the thickness of the glass or plastic substrate serving as the cell substrate. The second is to reduce the thickness of the polarizing plate.

However, with the trend of thinning,
The disadvantage of thinner panels is occurring. As the cell substrate becomes thinner, the rigidity of the substrate also becomes weaker, and the durability under heating / humidifying conditions is affected by the dimensional behavior of the polarizing plate, causing the panel to warp or displaying on the panel surface. It causes unevenness.

As a method of thinning the polarizing plate, it is conceivable to reduce the thickness of triacetyl cellulose (TAC) attached to the polarizer as a protective layer. The behavior of the polarizing plate as a whole increases without being able to suppress the behavior, and the influence on the display unevenness of the panel increases.

[0005]

Therefore, the present invention solves the display problem of the panel by controlling the thickness of the polarizer with respect to the thickness of the cell substrate, and is lightweight, thin, and warps and displays the panel. An object of the present invention is to provide a polarizing plate and a liquid crystal display device with less unevenness.

[0006]

In order to solve the above-mentioned problems, the inventors of the present invention have solved the display problem of the panel by optimizing the ratio of the thickness of the cell substrate to the thickness of the polarizer. That is, when the thickness of the cell substrate becomes thin and the thickness of the polarizer also becomes thin at the same time, the load applied to the cell is found to be small even if the polarizer shows dimensional behavior due to heat or the like. The invention was completed.

Therefore, the present invention is a polarizing plate comprising a polarizer made of a hydrophilic polymer film and a polymer protective film attached to at least one surface thereof, wherein the thickness of the polarizer is 1 μm or more and 20 μm or less, Further, the thickness d1 of the polarizer is adjusted so as to satisfy the relationship of d1 / d2 ≦ 0.044 with respect to the thickness d2 of one liquid crystal cell substrate on which the polarizing plate is mounted. Provide a polarizing plate. The polarizing plate of the present invention meets the requirements of recent liquid crystal displays that the polarizer has a small thickness and is lightweight and thin.

In the polarizing plate, the thickness of one liquid crystal cell substrate is preferably 350 μm or more and 750 μm or less. This is because if the thickness of one cell substrate is 350 μm or more, it is possible to suppress the warp of the panel without the thickness of the polarizer, and if it is 750 μm or less, the liquid crystal display device can be made lightweight and thin.

A polarizing plate in which a reflecting plate or a semi-transmissive reflecting plate is laminated on any one of the above polarizing plates may be used.

A polarizing plate in which a retardation plate or a λ plate is laminated on any one of the above polarizing plates may be used.

Further, a polarizing plate in which a viewing angle compensation film is laminated on any one of the above polarizing plates may be used.

A polarizing plate in which a brightness enhancement film is laminated on any one of the above polarizing plates may be used.

Further, according to the present invention, a liquid crystal display in which a polarizing plate made by bonding a polymer protective film to at least one surface of a polarizer made of a hydrophilic polymer film is arranged on at least one surface of a glass substrate or a plastic substrate liquid crystal cell. In the device, d1 and d2 are d when the thickness of the polarizer is d1 and the thickness of one liquid crystal cell substrate is d2.
Provided is a liquid crystal display device, which satisfies a relationship of 1 / d2 ≦ 0.044 and has a thickness of the polarizer of 1 μm or more and 20 μm or less. In this liquid crystal display device, it is preferable that the thickness of one cell substrate is 350 μm or more and 750 μm or less for the same reason as described above.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate of the present invention is a polarizing plate obtained by laminating a polymer protective film on at least one surface of a polarizer made of a hydrophilic polymer film, and the thickness of the polarizer is 1 μm or more. The thickness is 20 μm or less, and the thickness d1 of the polarizer satisfies the relationship of d1 / d2 ≦ 0.044 with respect to the thickness d2 of one liquid crystal cell substrate on which the polarizing plate is mounted. The thickness ratio of d1 / d2 is preferably in the range of 0.001 to 0.040, more preferably 0.
The range of 003 to 0.035 is preferable.

The polarizing plate of the present invention includes a polarizer made of a hydrophilic polymer film, specifically a hydrophilic polymer film containing a dichroic substance and having a polarizing function (hereinafter, referred to as a polarizing film). What is laminated with a polymer film to be a protective layer on one side or both sides of a "polarizer") via an appropriate adhesive layer is used.

The polarizer is obtained by subjecting a hydrophilic polymer film to a swelling treatment, a dyeing treatment with a dichroic substance such as iodine or a dichroic dye, and a crosslinking treatment, and uniaxially stretching at a stretching ratio of 3 to 7 times. And dried. The processing steps of dyeing, crosslinking and stretching need not be performed separately and may be performed simultaneously, and the order of each step may be arbitrary. The production conditions of the polarizer such as dyeing, crosslinking and stretching are not particularly limited, and conventionally known methods can be adopted. As the hydrophilic polymer film, a polyvinyl alcohol-based polymer film such as polyvinyl alcohol or partially formalized polyvinyl alcohol is preferably used because it is excellent in dyeability with a dichroic substance.

The above polyvinyl alcohol-based polymer is obtained by polymerizing vinyl acetate and then saponifying it, or copolymerizing vinyl acetate with a small amount of a copolymerizable monomer such as unsaturated carboxylic acid or unsaturated sulfonic acid. Is mentioned. The average degree of polymerization is 5 in terms of the solubility of the film in water.
It is preferably from 0.00 to 10,000, more preferably from 1000 to 60.
The degree of saponification is preferably 75 mol% or more, more preferably 98 mol% or more.

The thickness of the hydrophilic polymer film is 5
It is preferably 0 μm or less, and more preferably 5 to 40 μm. If it exceeds 50 μm, the warp of the panel becomes large when mounted on a liquid crystal display device.
On the other hand, when the film thickness is too thin, stretching becomes difficult.

The thickness d1 of the polarizer is 1 μm or more and 20 μm or more.
It is below, preferably 1 μm or more and 18 μm or less. When the thickness is 1 μm or more, the hydrophilic polymer film can be stretched, and when the thickness is 20 μm or less, the load applied to the cell can be reduced even if the polarizer exhibits dimensional behavior due to heat or the like. By thinning the thickness of the polarizer in this way, it is possible to reduce the weight and thickness.

The polymer film to be the protective layer is not particularly limited, and an appropriate transparent film can be used. The protective layer preferably has excellent transparency, mechanical strength, thermal stability, moisture barrier property, isotropic property, and the like. Examples thereof include cellulose resins such as triacetyl cellulose, polyester resins, polycarbonate resins, polyamide resins, polyimide resins, polyethersulfone resins, polysulfone resins, polystyrene resins, acrylic resins, acetate. Examples thereof include thermoplastic resins such as resin, polynorbornene resin, and polyolefin resin, and thermosetting or ultraviolet curing resin such as acrylic resin, urethane resin, acrylic urethane resin, epoxy resin, and silicone resin. When protective layers are provided on both sides of the polarizer, transparent protective films made of different polymers may be used on the front and back sides.

The thickness of the protective layer is arbitrary, but is generally 500 μm or less, preferably 5 to 300 μm for the purpose of thinning the polarizing plate.

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 antireflection treatment, a treatment for the purpose of preventing sticking, diffusion or antiglare, or the like may be applied. The hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film excellent in hardness and slipperiness such as a silicone-based appropriate UV curable resin is applied to the surface of the transparent protective film. It can be formed by a method of adding to.

On the other hand, the antireflection treatment is carried out 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 prior art. In addition, anti-sticking is performed for the purpose of preventing adhesion 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 hindering visual recognition of light transmitted through the polarizing plate. It can be formed by imparting a fine concavo-convex structure to the surface of the transparent protective film by an appropriate method such as a surface roughening method such as a sandblasting method or an embossing method or a method of blending transparent fine particles.

Examples of the transparent fine particles include silica and alumina having an average particle diameter of 0.5 to 20 μm, titania and zirconia, tin oxide and indium oxide, cadmium oxide and antimony oxide. Fine particles may be used, and organic fine particles composed of crosslinked or non-crosslinked polymer particles may be used. The amount of the transparent fine particles 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 antiglare layer containing 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 (viewing angle compensation function or the like) for diffusing light transmitted through the polarizing plate and expanding the viewing angle.
The antireflection layer, the sticking prevention layer, the diffusion layer, the antiglare layer, and the like described above can be provided as an optical layer formed of a sheet provided with these layers, separately from the transparent protective layer.

The adhesion treatment between the polarizer and the transparent protective film as the protective layer is not particularly limited, but for example, an adhesive made of a vinyl alcohol polymer, boric acid, borax or glutaraldehyde. Or an adhesive or the like made of at least a water-soluble crosslinking agent of a vinyl alcohol-based polymer such as melamine or oxalic acid. Such an adhesive layer is formed as a coating / drying layer of an aqueous solution, and other additives and a catalyst such as an acid can be blended as necessary in the preparation of the aqueous solution.

In practical use, the polarizing plate of the present invention can be used as an optical member laminated with another optical layer. Although the optical layer is not particularly limited, for example, a reflection plate, a semi-transmissive reflection plate, a retardation plate (including a λ plate such as a 1/2 wavelength plate and a 1/4 wavelength plate), a viewing angle compensation film and a brightness enhancement film. And the like, it is possible to use one layer or two or more layers of an appropriate optical layer that is sometimes used for forming a liquid crystal display device, etc., and particularly to a polarizing plate comprising the above-mentioned polarizer of the present invention and a protective layer, Further, a reflection plate or a reflection type polarizing plate or a semi-transmission reflection plate type polarizing plate in which a semi-transmissive reflection plate is laminated, and an ellipse in which a retardation plate is further laminated on the above-mentioned polarizer and a protective layer polarizing plate Polarization or circularly polarizing plate, a polarizing plate in which a viewing angle compensation film is further laminated on the polarizing plate composed of the above-mentioned polarizer and a protective layer, or a polarizing plate composed of the above-mentioned polarizer and a protective layer is further improved in brightness. Polarizing plate with laminated films Preferred.

Explaining the above-mentioned reflection plate, the reflection plate is provided on the polarizing plate to form the reflection type polarizing plate, and the reflection type polarizing plate is usually provided on the back side of the liquid crystal cell. It is possible to form a liquid crystal display device of the type that reflects incident light from the viewing side (display side) and to display, and it is possible to omit the built-in light source such as a backlight and easily reduce the thickness of the liquid crystal display device. Have.

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 attached to one surface of the polarizing plate through the above-mentioned transparent protective film or the like, if necessary. Specific examples thereof include a transparent protective film that is mat-treated if necessary, and a reflective layer formed by attaching a foil or a vapor deposition film made of a reflective metal such as aluminum to one surface of the transparent protective film.

Further, there may be mentioned a reflection type polarizing plate having a reflecting layer reflecting the fine concavo-convex structure on the transparent protective film containing fine particles and having a fine concavo-convex structure on the surface. The reflective layer having a finely textured surface has the advantage that diffused incident light is diffused to prevent directivity and glare, and uneven brightness can be suppressed. The reflective layer having a fine uneven structure reflecting the surface fine uneven structure of the transparent protective film can be formed by transparentizing a metal by an appropriate method such as a vacuum evaporation method, an ion plating method, a sputtering method or a vapor deposition method or a plating method. It can be performed by a method of directly attaching to the surface of the protective film.

Further, the reflection plate may be used as a reflection sheet or the like in which a reflection layer is provided on an appropriate film according to the transparent protective film instead of the method of directly attaching to the transparent protective film of the polarizing plate. it can. Since the reflective layer of the reflective plate is usually made of metal, the use form in which the reflective surface is covered with a film or a polarizing plate is to prevent reduction of the reflectance due to oxidation, and thus to maintain the initial reflectance for a long time. Also, it is preferable from the viewpoint of avoiding the additional provision of the protective layer.

The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light in the reflective layer. The semi-transmissive polarizing plate is usually provided on the back side of the liquid crystal cell, and when the liquid crystal display device is used in a relatively bright atmosphere,
An image is displayed by reflecting incident light from the viewing side (display side), and in a relatively dark atmosphere, an image is displayed using a built-in light source such as a backlight built into the back side of the semi-transmissive polarizing plate. It is possible to form a liquid crystal display device of the type that displays That is, the semi-transmissive polarizing plate is useful for forming a liquid crystal display device of a type that can save energy for using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source in a relatively dark atmosphere. Is.

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 a polarizer and a protective layer will be described.

A retardation plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, or changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. A so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate for converting the light into elliptically polarized light or circularly polarized light or converting the elliptically polarized light or circularly polarized light into linearly polarized light. A half-wave plate (also called a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

The elliptically polarizing plate compensates (prevents) coloring (blue or yellow) generated by the birefringence of the liquid crystal layer of the super twisted nematic (STN) type liquid crystal display device to obtain a black and white display without the coloring. It is effectively used for. Further, the one in which the three-dimensional refractive index is controlled is preferable because it can also compensate (prevent) coloring that occurs when the screen of the liquid crystal display device is viewed in an oblique direction. The circularly polarizing plate is effectively used, for example, when adjusting the color tone of an image of a reflective liquid crystal display device in which an image is displayed in color, and also has a function of preventing reflection.

Specific examples of the retardation plate include birefringence 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. Examples thereof include a transparent film, an alignment film of a liquid crystal polymer, and a film in which an alignment layer of a liquid crystal polymer is supported. Further, as the inclined orientation film, for example, a film obtained by adhering a heat-shrinkable film to a polymer film and subjecting the polymer film to stretching treatment and / or shrinking treatment under the action of the shrinkage force by heating, or a liquid crystal polymer which is obliquely oriented. And so on.

Next, a polarizing plate in which a viewing angle compensation film is further laminated on the above-mentioned polarizing plate comprising a polarizer 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 from a slightly oblique direction, not perpendicular to the screen. As such a viewing angle compensation film, a triacetyl cellulose film coated with a discotic liquid crystal or a retardation plate is used.
In the ordinary retardation plate, while a polymer film having birefringence that is uniaxially stretched in its plane direction is used,
The retardation plate used as a viewing angle compensation film is a birefringent polymer film biaxially stretched in the plane direction, or a refractive index in the thickness direction stretched uniaxially in the plane direction and also in the thickness direction. A bidirectionally stretched film such as a tilt-oriented polymer film having a controlled temperature is used. As the tilted oriented film, as described above, for example, a polymer film is adhered to a heat-shrinkable film and stretched and / or shrunk to the polymer film under the action of the shrinkage force by heating, or a liquid crystal polymer is slanted. Examples include oriented materials. 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 in which a brightness enhancement film is attached to the above-mentioned polarizing plate comprising a polarizer and a protective layer is usually used by being provided on the back side of a liquid crystal cell. The brightness enhancement film has a property of reflecting linearly polarized light of a predetermined polarization axis or circularly polarized light of a predetermined direction when natural light enters due to reflection from the backlight of the liquid crystal display device or the back side, and transmits other light. A polarizing plate in which a brightness enhancement film and a polarizing plate composed of the above-mentioned polarizer and a protective layer are laminated, makes light from a light source such as a backlight incident to obtain transmitted light in a predetermined polarization state, and the predetermined polarization state. Other light is reflected without being transmitted. The light reflected on the surface of the brightness enhancement film is inverted through a reflection layer or the like provided on the back side of the brightness enhancement film to be re-incident on the brightness enhancement plate, and 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 improvement film and by supplying polarized light that is difficult to be 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 from the back side of a liquid crystal cell through a polarizer without using a brightness enhancement film, almost all light having a polarization direction that does not match the polarization axis of the polarizer is Will not be transmitted through the polarizer. That is, although depending on the characteristics of the polarizer used, about 50% of light is absorbed by the polarizer, and the amount of light that can be used for liquid crystal image display and the like is reduced accordingly, and the image becomes dark. The brightness enhancement film allows light having a polarization direction that is absorbed by the polarizer to be reflected once by the brightness enhancement film without being incident on the polarizer, and then inverted through a reflection layer or the like provided behind it. The light-increasing film transmits only the polarized light whose polarization direction is such that the light reflected and inverted between the two is allowed to pass through the polarizer. Since the light is supplied to the polarizer by the light, the light from the backlight or the like can be efficiently used for displaying an image on the liquid crystal display device, and the screen can be brightened.

The above-mentioned brightness enhancement film is, for example, a multilayer thin film of a dielectric or a multilayer laminate of thin films having different refractive index anisotropies, transmits linearly polarized light of a predetermined polarization axis and reflects other light. Those exhibiting the characteristics of, for example, a cholesteric liquid crystal layer, particularly an oriented film of a cholesteric liquid crystal polymer or a film obtained by supporting the oriented liquid crystal layer on a film substrate, such that it reflects either left-handed or right-handed circularly polarized light and As for the light, an appropriate one such as one showing a characteristic of transmitting can be used.

Therefore, in the brightness enhancement film of the type which transmits the linearly polarized light of the above-mentioned predetermined polarization axis, the transmitted light is directly incident on the polarizing plate with the polarization axis aligned to suppress the absorption loss by the polarizing plate. It can be efficiently transmitted. On the other hand, in a brightness enhancement film of a type that transmits circularly polarized light like a cholesteric liquid crystal layer, it can be directly incident on a polarizer, but from the viewpoint of suppressing absorption loss, the transmitted circularly polarized light is linearly polarized through a retardation plate. It is preferable that the light is incident on the polarizing plate. By using a ¼ wavelength plate as the retardation plate, circularly polarized light can be converted into linearly polarized light.

The retardation plate that functions as a quarter-wave plate in a wide wavelength range such as a visible light region is a retardation layer that functions as a quarter-wave plate for monochromatic light such as light having a wavelength of 550 nm. It can be obtained by a method of superimposing a retardation layer showing the retardation characteristic of, for example, a retardation layer functioning as a half-wave plate. Therefore, the retardation plate disposed between the polarizing plate and the brightness enhancement film may be composed of one layer or two or more retardation layers.

As for the cholesteric liquid crystal layer,
By combining two or more layers having different reflection wavelengths to form an arrangement structure in which two or more layers are superposed, it is possible to obtain one that reflects circularly polarized light in a wide wavelength range such as a visible light range.
Based on this, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

Further, the polarizing plate may be formed by laminating a polarizing plate and two or three or more optical layers, like the above-mentioned polarization separation type polarizing plate. Therefore, it may be a reflective elliptical polarizing plate or a semi-transmissive elliptical polarizing plate in which the above reflective polarizing plate or semi-transmissive polarizing plate is combined with a retardation plate. Two
The optical member in which three layers or three or more optical layers are laminated can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device, etc. The product has excellent quality stability and assembling workability, and has an advantage that the manufacturing efficiency of the liquid crystal display device can be improved. In addition, an appropriate adhesion means such as an adhesive layer can be used for the lamination.

The polarizing plate and the optical member described above may be provided with an adhesive layer for adhering to other members such as a liquid crystal cell. The pressure-sensitive adhesive layer can be formed from a suitable conventional pressure-sensitive adhesive such as acrylic. In particular, in terms of prevention of foaming phenomenon and peeling phenomenon due to moisture absorption, deterioration of optical characteristics due to thermal expansion difference and the like, prevention of warpage of liquid crystal cells, and further formation of a liquid crystal display device having high quality and excellent durability, the moisture absorption rate is high. The adhesive layer is preferably low and has excellent heat resistance. It is also possible to form an adhesive layer containing fine particles and exhibiting light diffusivity. The pressure-sensitive adhesive layer may be provided on a necessary surface as necessary. For example, if a protective layer of a polarizing plate comprising a polarizer and a protective layer is mentioned, a pressure-sensitive adhesive layer may be provided on one side or both sides of the protective layer, if necessary. Should be provided.

When the pressure-sensitive adhesive layer provided on the polarizing plate or the optical member is exposed on the surface, it is preferable to temporarily cover the pressure-sensitive adhesive layer with a separator for the purpose of preventing contamination until the pressure-sensitive adhesive layer is put into practical use. The separator is formed by a method in which a suitable thin sheet conforming to the above-mentioned transparent protective film or the like is provided with a release coat using a suitable release agent such as silicone-based or long-chain alkyl-based, fluorine-based or molybdenum sulfide as necessary. be able to.

Each layer such as the polarizer and the transparent protective film forming the polarizing plate or the optical member, the optical layer or the adhesive layer is, for example, a salicylate compound, a benzophenone compound, a benzotriazole compound or a cyanoacrylate compound. It may be one having an ultraviolet absorbing ability by an appropriate method such as a method of treating with an ultraviolet absorber such as a compound or a nickel complex salt compound.

The polarizing plate of the present invention can be preferably used for forming various devices such as liquid crystal display devices.
It can be used for a liquid crystal display device of a reflective type or a semi-transmissive type, or a transmissive / reflective type, in which a polarizing plate is arranged on one side or both sides of a liquid crystal cell. The liquid crystal cell substrate may be either a plastic substrate or a glass substrate. The liquid crystal cell forming the liquid crystal display device is arbitrary, for example, an active matrix drive type represented by a thin film transistor type,
A liquid crystal cell of an appropriate type such as a simple matrix drive type represented by a twist nematic type or a super twist nematic type may be used.

The above liquid crystal cell substrate has a thickness of d2.
However, a polarizer having a thickness ratio (d1 / d2) to the thickness d1 of the polarizer of 0.044 or less is used. The thickness of the cell substrate is preferably 350 μm or more and 750 μm or less in terms of thinning, lightness, strength, deformation prevention, and the like. By setting the thickness of the cell substrate to be 350 μm or more, durability under heating / humidifying conditions is good, warpage of the panel can be suppressed, and display unevenness on the panel surface can be reduced. Further, when the thickness is 750 μm or less, it is possible to reduce the thickness and weight.

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

[0051]

EXAMPLES The present invention will be described below with reference to examples, but these examples do not limit the present invention in any way.

Example 1 A polyvinyl alcohol (hereinafter abbreviated as “PVA”) film having a thickness of 45 μm was swollen in pure water and dyed with a mixed aqueous solution of iodine and potassium iodide. Then, cross-linking with boric acid and 5.5
The film was stretched twice and dried at 50 ° C. to prepare a polarizer. The thickness of this polarizer was 17 μm. A 80 μm-thick triacetyl cellulose film was attached to both surfaces of the produced polarizer and then dried to prepare a polarizing plate.

The obtained polarizing plate was a sheet having a thickness of 700 μm.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

Example 2 A PVA film having a thickness of 30 μm was swollen in pure water and dyed with a mixed aqueous solution of iodine and potassium iodide. After that, cross-linking with boric acid and stretching at 6.0 times were performed, and drying was performed at 50 ° C. to prepare a polarizer. The thickness of this polarizer was 11 μm. An 80 μm thick triacetyl cellulose film was attached to both sides of the produced polarizer, and then dried to produce a polarizing plate.

The obtained polarizing plate was 630 μm thick.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

Example 3 A PVA film having a thickness of 40 μm was stretched 5 times by dry stretching, and the stretched PVA film was dyed with a mixed aqueous solution of iodine and potassium iodide, cross-linked with boric acid and 1.2 times. Stretched, 50 ℃
And dried to prepare a polarizer. The thickness of this polarizer was 8 μm. An 80 μm thick triacetyl cellulose film was attached to both sides of the produced polarizer, and then dried to produce a polarizing plate.

The obtained polarizing plate was used as one sheet having a thickness of 400 μm.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

Comparative Example 1 A PVA film having a thickness of 75 μm was swollen in pure water and dyed with a mixed aqueous solution of iodine and potassium iodide. After that, cross-linking with boric acid and 5.0-fold stretching were performed, followed by drying at 50 ° C. to prepare a polarizer. The thickness of this polarizer was 28 μm. An 80 μm thick triacetyl cellulose film was attached to both sides of the produced polarizer, and then dried to produce a polarizing plate.

The obtained polarizing plate was 630 μm thick.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

Comparative Example 2 A PVA film having a thickness of 75 μm was stretched 5 times by dry stretching, and the stretched PVA film was dyed with a mixed aqueous solution of iodine and potassium iodide, crosslinked with boric acid and 1.2 times. Stretched, 50 ℃
And dried to prepare a polarizer. The thickness of this polarizer was 25 μm. 80 μm on both sides of the produced polarizer
A thick triacetyl cellulose film was attached and then dried to prepare a polarizing plate.

The obtained polarizing plate was a sheet of 400 μm thick.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

Comparative Example 3 A polyvinyl alcohol (hereinafter referred to as “PVA”) film having a thickness of 45 μm was swollen in pure water and dyed with an aqueous mixed solution of iodine and potassium iodide. Then, cross-linking with boric acid and 5.0
The film was stretched twice and dried at 50 ° C. to prepare a polarizer. The thickness of this polarizer was 18 μm. A 80 μm-thick triacetyl cellulose film was attached to both surfaces of the produced polarizer and then dried to produce a polarizing plate.

The obtained polarizing plate was 400 μm thick.
The liquid crystal cell substrate was bonded to both sides at an absorption axis angle of 45 °.

In Example 1, the thickness ratio of polarizer (17 μm) to one liquid crystal cell substrate (700 μm) (thickness of polarizer / one liquid crystal cell substrate) was 0.024, and the thickness ratio was 0.0.
44 or less, and a polarizer thickness of 1 μm or more and 20 μ
m or less is satisfied.

In Example 2, the thickness ratio of the polarizer (11 μm) and one liquid crystal cell substrate (630 μm) (polarizer / thickness of one liquid crystal cell substrate) was 0.017, and the thickness ratio was 0.0.
44 or less, and a polarizer thickness of 1 μm or more and 20 μ
m or less is satisfied.

In Example 3, the thickness ratio of the polarizer (8 μm) to one liquid crystal cell substrate (400 μm) (polarizer / thickness of one liquid crystal cell substrate) was 0.020, and the thickness ratio was 0.04.
4 or less, and the polarizer thickness is 1 μm or more and 20 μm or more.
Meets the following:

In Comparative Example 1, the thickness ratio of the polarizer (28 μm) and one liquid crystal cell substrate (630 μm) (polarizer / thickness of one liquid crystal cell substrate) was 0.044, and the thickness ratio was 0.0.
Although the thickness is 44 or less, the thickness of the polarizer is 20 μm or more, and the thickness of the polarizer is not 1 μm or more and 20 μm or less.

In Comparative Example 2, the thickness ratio of the polarizer (25 μm) to one liquid crystal cell substrate (400 μm) (polarizer / thickness of one liquid crystal cell substrate) was 0.063, and the thickness ratio was 0.0.
44 or less is not satisfied. The thickness of the polarizer is 20 μm
The above is not satisfied, and the polarizer thickness of 1 μm or more and 20 μm or less cannot be satisfied.

In Comparative Example 3, the thickness ratio of the polarizer (18 μm) to one liquid crystal cell substrate (400 μm) (polarizer / thickness of one liquid crystal cell substrate) was 0.045, and the polarizer thickness 1
The thickness ratio is 0.0
44 or less is not satisfied.

(Evaluation) A laminate of a polarizing plate and a liquid crystal cell substrate was heated (80 ° C. × 6 hours) and humidified (60 ° C. /
After being left under the condition of 90% RH × 6 hours), the in-plane transmittance at 9 points (FIG. 1) was measured, and the in-plane transmittance variation degree was calculated by the following formula. The smaller the value of the variation, the smaller the load due to the heating and humidifying stress, and the less the display unevenness of the panel. In-plane transmittance variation degree = (+++) / 4-(+
+++) / 5

The display unevenness level was visually evaluated according to the following criteria. Evaluation criteria: ◎ There is no color loss at the panel edges or variations in the hue on the panel surface. ○ There is almost no color loss at the panel edges or variations in the hue on the panel surface. △ Color loss at the panel edges or in the panel surface. There is some variation in hue × There is color loss at the edge of the panel or variation in hue within the panel

The transmittance was measured using a spectrophotometer (Murakami Color Research Laboratory, DOT-3), and was measured by JLS Z 87.
The Y value is shown with the luminosity factor corrected by the 01 degree 2 degree visual field (C light source).

The above results are summarized in Table 1.

[0074]

Table 1 80 ° C. heating test 60 ° C./90% RH humidification test Experiment No. Plane transmittance display unevenness plane transmittance display unevenness variation level variation degree level Example 1 0.022 ○ 0.026 ○ Example 2 0.015 ○ 0.012 ◎ Example 3 0.010 ◎ 0.011 ◎ Comparative Example 1 0.071 △ 0.119 × Comparative Example 2 0.096 × 0.131 XX Comparative Example 3 0.065 △ 0.105 ×

As is clear from the results shown in Table 1, the polarizing plate and the liquid crystal display device of the present invention have a small in-plane transmittance variation even after the heating / humidification test, and even if the unevenness in the display is visually confirmed. It turned out to be a level without problems.

[0076]

As described above, in the polarizing plate of the present invention, the thickness ratio of the polarizer to the liquid crystal cell substrate to be bonded is 0.044 or less and the thickness of the polarizer is 1 μm or more 2
Since it is 0 μm or less, it is lightweight and thin, but its dimensional change due to heating and humidification is small, and it has excellent durability.

Further, the liquid crystal display device formed from the polarizing plate and the liquid crystal cell substrate of the present invention displays a panel warp and a variation in transmittance within the panel surface even after long-term use at room temperature or under heating / humidification. There is almost no unevenness, and stable quality can be maintained over a long period of time. Therefore, its industrial value is great.

[Brief description of drawings]

FIG. 1 is a diagram showing a measurement position of an in-plane transmittance variation degree in a liquid crystal panel.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Kazuhiro Higashi             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. (72) Inventor Seiichi Kusumoto             1-2 1-2 Shimohozumi, Ibaraki City, Osaka Prefecture Nitto             Electric Works Co., Ltd. F-term (reference) 2H042 BA03 BA12 BA14 BA20 DA02                       DA11 DA21 DB01 DC02 DE00                 2H049 BA02 BA06 BA26 BA27 BB13                       BB33 BB43 BB63 BC22                 2H091 FA08 FB02 FC08 FC21 FC29                       FC30 FD07 GA16 GA17 LA03                       LA07 LA11 LA12 LA13 LA16

Claims (8)

[Claims] 1. A polarizing plate comprising a polarizer made of a hydrophilic polymer film and a polymer protective film bonded to at least one surface of the polarizer, wherein the thickness of the polarizer is 1 μm or more and 20 μm or less, and Thickness d1 of the liquid crystal cell substrate on which the polarizing plate is mounted is d1 / d2 ≦ 0.
A polarizing plate which is adjusted to satisfy the relationship of 044. 2. The thickness of one liquid crystal cell substrate is 350.
The polarizing plate according to claim 1, wherein the polarizing plate has a thickness of not less than μm and not more than 750 μm. 3. A polarizing plate comprising a polarizing plate according to claim 1 or 2 and a reflecting plate or a semi-transmissive reflecting plate laminated on the polarizing plate. 4. A polarizing plate comprising a retardation plate or a λ plate laminated on the polarizing plate according to claim 1. 5. A polarizing plate comprising a polarizing film according to claim 1 or 2 and a viewing angle compensation film laminated on the polarizing plate. 6. A polarizing plate comprising a polarizing plate according to claim 1 and a brightness enhancement film laminated on the polarizing plate. 7. A liquid crystal display device comprising a polarizer made of a hydrophilic polymer film and a polymer protective film bonded to at least one surface of the polarizer, and a polarizing plate disposed on at least one surface of a liquid crystal cell of a glass substrate or a plastic substrate. When the thickness of the polarizer is d1 and the thickness of one liquid crystal cell substrate is d2, d1 and d2 are d1 / d2 ≦ 0.0.
44 is satisfied, and the thickness of the polarizer is 1 μm.
A liquid crystal display device having a thickness of 20 μm or less. 8. The liquid crystal cell substrate has a thickness of 350.
The liquid crystal display device according to claim 7, wherein the liquid crystal display device has a thickness of not less than μm and not more than 750 μm.