JP2001133629A - Polarizing member, liquid crystal panel and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing material hardly causing warpages, capable of forming a liquid crystal display device small in thickness, large in size and superior in luminance and display characteristics, even in a liquid crystal panel formed by laminating a reflection-type polarizer with a polarizer into one body and adhering the laminated body to a liquid crystal cell. SOLUTION: This polarizing member consists of a laminated body produced by adhering a cholesteric liquid crystal layer 1 firmly supported by a transparent substrate 11, a quarter wave plate 2, and a polarizing plate 3 consisting of a polarizing film 33 protected by transparent protective layers 32, 34 via adhesive layer 21, 31. Each thickness of the transparent substrate body and the transparent protective layer is <=50 μm. The liquid crystal is produced by adhering the obtained polarizing member to the light incident side of a liquid crystal cell 4 via an adhesive layer 35 and adhering a polarizer 5 consisting of a polarizing film 53 protected by transparent protective layers 52, 54, each having <=50 μm thickness on the visible side of the cell via an adhesive layer 51. The liquid crystal display device uses the liquid crystal panel. Thus, a liquid crystal display device, having superior display quality by preventing the occurrence of wrinkles caused by heat, can be produced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing member which can form a thin liquid crystal panel or a liquid crystal display device which is hardly warped and has excellent brightness.

[0002]

2. Description of the Related Art Conventionally, a side-light type light guide plate for forming a backlight is made thinner and larger for the purpose of making a liquid crystal display device thinner, larger, and higher in brightness. A method of arranging and covering a reflective polarizing plate composed of a layer and a quarter-wave plate has been known.
However, when the above-mentioned reflective polarizing plate is laminated and integrated with the polarizing plate and bonded to one side of the liquid crystal cell, and the polarizing plate is bonded to the other side to form a liquid crystal panel, a problem that large warpage occurs due to heat and humidity. There was a point. Such warpage becomes more remarkable as the cell substrate such as a glass plate is made thinner for the purpose of thinning the cell.

[0003] The above-mentioned warpage decreases with time. In the course of the reduction, it causes heat wrinkles due to expansion and contraction in other optical base materials such as a prism sheet and a light diffusing plate which are separately provided. It may cause the quality to deteriorate. In the above description, the lamination and integration of the reflective polarizing plate and the polarizing plate is intended to reduce the thickness by preventing the intervening space.

[0004]

The present invention is directed to a liquid crystal panel in which a reflection type polarizing plate is laminated and integrated with a polarizing plate to form a liquid crystal panel adhered to a liquid crystal cell. An object is to develop a polarizing member capable of forming a liquid crystal display device having excellent characteristics.

[0005]

According to the present invention, a cholesteric liquid crystal layer closely adhered to and supported by a transparent substrate, a quarter-wave plate, and a polarizing plate having a polarizing film protected by a transparent protective layer are bonded via an adhesive layer. A polarizing member comprising a laminate, wherein the thickness of the transparent substrate and the transparent protective layer is 50 μm or less, and bonding the polarizing member to the light incident side of a liquid crystal cell via an adhesive layer, A liquid crystal panel, comprising a polarizing plate whose film is protected by a transparent protective layer having a thickness of 50 μm or less and adhered to the viewing side of the cell via an adhesive layer, and a liquid crystal panel using the liquid crystal panel. To provide a liquid crystal display device.

[0006]

According to the polarizing member of the present invention, when the polarizing member and the polarizing plate are bonded to a liquid crystal cell to form a liquid crystal panel, warpage caused by heat and humidity can be suppressed. A large-area liquid crystal display device having excellent luminance and display quality can be formed.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The polarizing member according to the present invention has a thickness of 50.
A cholesteric liquid crystal layer closely adhered to a transparent base material of μm or less, a 波長 wavelength plate, and a polarizing film having a thickness of 50 μm
It is composed of a laminate in which a polarizing plate protected by the following transparent protective layer is bonded via an adhesive layer. An example is shown in FIG. 1 is a cholesteric liquid crystal layer, 11 is a transparent substrate, 2 is a quarter-wave plate, 3 is a polarizing plate composed of a polarizing film 33 and transparent protective layers 32 and 34, and 21 and 31 are adhesive layers.

FIG. 1 shows a liquid crystal panel, in which 5 is a polarizing film 53 and transparent protective layers 52, 54.
Is a polarizing plate on the viewing side comprising: 35, 51 are adhesive layers,
55 is an antiglare layer.

The cholesteric liquid crystal layer closely adhered to and supported by the transparent substrate separates incident natural light into reflected light and transmitted light to provide transmitted light composed of right and left circularly polarized light. Accordingly, light from a light source such as a backlight is incident to obtain transmitted light in a predetermined polarization state, and when reflected light is inverted and re-entered through a reflective layer or the like, part or all of the light is converted to light in a predetermined polarization state. It is possible to increase the amount of light that is transmitted and thereby transmitted through the cholesteric liquid crystal layer, and to increase the amount of light that can be used for a liquid crystal display or the like by supplying polarized light that is hardly absorbed by the polarizing film and improve the luminance. .

[0010] As the cholesteric liquid crystal layer, an appropriate material exhibiting the property of transmitting incident natural light to one of left and right circularly polarized light and reflecting the other can be used, and the type thereof is not particularly limited. Further, the cholesteric liquid crystal layer may have an arrangement structure in which two or three or more layers are overlapped in a combination of those having different reflection wavelengths. With such superimposition, it is possible to obtain circularly polarized light that reflects in a wide wavelength range such as the visible light range, and based on this, it is possible to obtain transmitted circularly polarized light in a wide wavelength range.

The cholesteric liquid crystal layer exhibiting the above-mentioned reflection / transmission characteristics can be obtained as a liquid crystal polymer layer or the like obtained by subjecting a transparent substrate to an alignment treatment through an alignment film such as a rubbing treatment. In the present invention, a transparent base material having a thickness of 50 μm or less is used as the transparent base material for closely supporting the cholesteric liquid crystal layer. Thereby, when a liquid crystal panel is formed, the shear stress can be reduced and the warpage can be suppressed. The preferred thickness in terms of warpage suppression and support strength is 1
0-47 μm, especially 20-45 μm, especially 30-43 μm
It is.

The material for forming the transparent substrate is not particularly limited, but generally a polymer is used. Examples of the polymer include cellulosic polymers such as cellulose diacetate and cellulose triacetate; polyester polymers such as polyethylene terephthalate and polyethylene naphthalate; acrylic polymers such as polycarbonate polymers and polymethyl methacrylate; polystyrene and acrylonitrile / styrene. Styrene polymers such as copolymers, polyethylene and polypropylene, polyolefins having a cyclo or norbornene structure, olefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, and amide polymers such as nylon and aromatic polyamides. can give.

Further, imide polymers, sulfone polymers, polyethersulfone polymers, polyetheretherketone polymers, polyphenylene sulfide polymers, vinyl alcohol polymers, vinylidene chloride polymers, vinyl butyral polymers, arylate polymers, Oxymethylene-based polymers, epoxy-based polymers and blends of the above-mentioned polymers, and polyester-based, acrylic-based, urethane-based and amide-based, silicone-based and epoxy-based polymers and the like that are cured by heat or ultraviolet irradiation, etc. are also used as the transparent substrate. Can be used to form A transparent substrate having excellent isotropy, such as a cellulosic film, is preferably used.

On the other hand, the quarter-wave plate disposed with respect to the cholesteric liquid crystal layer aims to linearly polarize circularly polarized light transmitted through the cholesteric liquid crystal layer. By arranging the linearly polarized light transmitted through the wave plate so as to coincide as much as possible with the vibration plane, absorption loss can be prevented and luminance can be further increased. 1 /
Examples of conventional four-wavelength plates include birefringent films composed of stretched films of various polymers, oriented films of liquid crystal polymers such as discotic and nematic, and those in which the oriented liquid crystal layer is supported on a transparent substrate. Appropriate suitable ones can be used.

The polymer forming the birefringent film may be an appropriate polymer such as those exemplified for the transparent substrate described above. Above all, a polymer having excellent crystallinity, such as a polyester-based polymer or polyetheretherketone, can be preferably used. The stretched film may be processed by an appropriate method such as uniaxial or biaxial. Further, a birefringent film in which the refractive index in the thickness direction of the film is controlled by a method of applying a contraction force and / or a stretching force while adhering to the heat-shrinkable film may be used.

The quarter-wave plate may be formed by laminating two or more retardation layers for the purpose of controlling optical characteristics such as retardation. Incidentally, a phase difference layer functioning as a 波長 wavelength plate and a phase difference layer exhibiting other phase difference characteristics, for example, a phase difference layer functioning as a 板 wavelength plate are superimposed on monochromatic light such as light having a wavelength of 550 nm. According to such a method, a plate functioning as a quarter-wave plate in a wide wavelength range such as a visible light region can be obtained.

The polarizing plate is provided on the side of the cholesteric liquid crystal layer 1 via the quarter-wave plate 2 as shown in the drawing, for the purpose of obtaining linearly polarized light for achieving liquid crystal display. As the polarizing plate, one having one or both sides of a polarizing film 33 protected by transparent protective layers 32 and 34 and having a thickness of 50 μm or less as shown in FIG. 1 is used. Thereby, when a liquid crystal panel is formed, the shear stress can be reduced and the warpage can be suppressed.
The thickness of the transparent protective layer is preferably 10 to 47 μm, more preferably 20 to 45 μm, especially 30 to
43 μm.

As the polarizing film, an appropriate film that transmits linearly polarized light having a predetermined polarization axis and absorbs other light can be used, and the type thereof is not particularly limited. Incidentally, as an example, stretching is performed by adsorbing iodine and / or a dichroic dye on a hydrophilic polymer film such as a polyvinyl alcohol-based film, a partially formalized polyvinyl alcohol-based film, and an ethylene / vinyl acetate copolymer-based partially saponified film. Examples of the treated film include films having a polyene orientation such as a dehydrated product of polyvinyl alcohol and a dehydrochlorinated product of polyvinyl chloride.

The transparent protective layer provided on one side or both sides of the polarizing film can be formed of the polymer exemplified for the above transparent substrate. Above all, a transparent protective layer made of a polymer having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like is preferable. The transparent protective layer can be formed by an appropriate method such as a method of applying a polymer liquid or an adhesive lamination method of a film.

The polarizing member is made of a transparent base material 11 as shown in FIG.
The cholesteric liquid crystal layer 1, the quarter-wave plate 2, and the polarizing plate 3 which are in close contact with each other are adhered via the adhesive layers 21 and 31 to be laminated and integrated. The purpose of such lamination and integration is to stabilize the quality and prevent the optical axis from being displaced, reduce the thickness, and improve the efficiency of assembling the liquid crystal panel. For forming the adhesive layer, an appropriate adhesive substance such as an adhesive having a suitable polymer as a base polymer such as an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or synthetic rubber can be used.

Among them, those which are excellent in optical transparency, weather resistance, heat resistance and the like and hardly cause floating or peeling under the influence of heat or humidity, such as acrylic adhesives, can be preferably used. Examples of the acrylic pressure-sensitive adhesive include an alkyl ester of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as a methyl group, an ethyl group, and a butyl group, a (meth) acrylic acid and a (meth) acrylic acid. An acrylic monomer comprising an improving component such as hydroxyethyl acid is used to prepare a glass transition temperature of 0.
Examples thereof include, but are not limited to, an acrylic polymer having a weight-average molecular weight of 100,000 or more, which is obtained by copolymerization in a combination at a temperature of not more than 100 ° C. or less.

The adhesive lamination consists of a cholesteric liquid crystal layer, 1 /
It can be performed by attaching an adhesive layer to a necessary portion of the adhesive surface of the four-wavelength plate or / and the polarizing plate, for example, by applying an adhesive liquid by an appropriate development method such as a casting method or a coating method. An appropriate method such as a method of directly attaching, or a method of forming an adhesive layer on a separator and transferring the same according to the above method can be employed.

The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the adhesive strength and the like, and is generally from 1 to 500 μm, especially from 10 to 50 μm. The pressure-sensitive adhesive layer can be formed as a superimposed layer of different types of pressure-sensitive adhesives, or can be a light-diffusion type by mixing fine particles. As shown in FIG. 1, an adhesive layer 35 may be provided on the outer surface of the polarizing member for adhesion to another member such as the liquid crystal cell 4, if necessary. Until practical use, the surface can be temporarily covered with a separator or the like for protection such as contamination prevention.

The polarizing member according to the present invention can be used for various applications according to the related art. In particular, it can be preferably used for forming a liquid crystal panel for the purpose of improving luminance, thinning, and increasing the area. FIG. 1 shows an example of the liquid crystal panel. In this method, a polarizing member is bonded to the light incident side of the liquid crystal cell 4 via an adhesive layer 35 provided on the outer surface of the polarizing plate 3, and a polarizing plate 5 is provided on the outer surface of the liquid crystal cell 4 on the viewing side. It is formed by bonding via an adhesive layer 51.

The polarizing plate 5 on the viewing side is obtained by protecting one or both surfaces of a polarizing film 53 with transparent protective layers 52 and 54 having a thickness of 50 μm or less according to the polarizing plate 3 used for forming the polarizing member. Is used. Thereby, warpage of the liquid crystal panel due to heat and humidity can be suppressed. The polarizing plate on the viewing side may be provided with an antiglare layer 55, an anti-reflection layer, etc. on the surface on the viewing side, if necessary, as shown in the figure.

The anti-glare layer scatters external light reflected on the surface, and the anti-reflection layer suppresses surface reflection of the external light, and the surface reflected light is glare and impairs the visibility of the light transmitted through the panel. This is done for the purpose of preventing things from happening.
Therefore, both the anti-glare layer and the anti-reflection layer can be provided to further improve the prevention of visual impairment due to surface reflected light.

The antiglare layer and the antireflection layer are not particularly limited, and can be formed as appropriate having the above functions. By the way, the anti-glare layer is provided with a light scattering / reflective fine uneven structure on the surface of the transparent substrate by an appropriate method such as a roughening method such as a sand blast method or an embossing method, or a resin coating method containing transparent particles. Can be formed. In addition, the antireflection layer is formed by a vapor deposition method such as a vacuum deposition method, an ion plating method, or a sputtering method, a plating method, or a suitable coating method such as a sol-gel method. It can be formed by an interference film made of a coating film of a low refractive material such as.

In the above, the transparent particles forming the antiglare layer include, for example, silica or alumina having an average particle diameter of 0.5 to 20 μm, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide, or the like. One type or two or more types of inorganic particles that may be conductive, organic particles made of a crosslinked or uncrosslinked polymer, or the like are used. The amount of the transparent particles used is generally 2 to 50 parts by weight, preferably 5 to 25 parts by weight, per 100 parts by weight of the transparent resin.

As the transparent resin for forming the coat film by blending the transparent particles, an appropriate resin can be used. Above all, a resin or the like that is cured by heat, ultraviolet light, or the like exemplified for the transparent substrate is preferably used. Such a curable resin is
It is also effective for hard coat treatment for the purpose of preventing scratches. In addition, those having both the anti-glare layer and the anti-reflection layer,
For example, it can be formed by providing an antireflection layer reflecting the surface fine unevenness structure on the antiglare layer by the above-described method or the like.

As described above, in forming the liquid crystal panel, the polarizing member is disposed on the side of the liquid crystal cell on which illumination light such as a surface light source is incident, and the liquid crystal panel uses the polarizing member or the polarizing plate according to the present invention. There is no particular limitation except for the point, and it can be formed according to a conventional method.

Therefore, any liquid crystal cell can be used to form a liquid crystal panel. For example, an active matrix drive type represented by a thin film transistor type, a simple matrix drive type represented by a TN type or an STN type, and the like. Various liquid crystal panels can be formed using an appropriate type of liquid crystal cell such as one provided with a color filter.

The liquid crystal display device can be formed by, for example, a method of disposing the liquid crystal panel on a surface light source. An example is shown in FIG. Reference numeral 8 denotes a surface light source (backlight). As shown in the figure, the polarizing member is arranged such that the cholesteric liquid crystal layer 1 is on the side of the surface light source 8 when the liquid crystal display device is formed. In the illustrated example, a liquid crystal panel is arranged on a surface light source 8 via a light diffusion sheet 7 and a light collection sheet 6.

The surface light source 8 of the above example is of a sidelight type in which a reflection layer 9 is provided on the bottom surface of a light guide plate 81 on the side of which a light source 82 surrounded by a holder 83 is arranged. The sheet 6 is formed by arranging prism sheets 6a and 6b such that their prism ridges intersect.

According to the liquid crystal display device described above, the light emitted from the surface light source 8 is diffused by the light diffusion sheet 7 and the optical path is controlled by the light collection sheet 6 so as to be incident on the cholesteric liquid crystal layer 1 of the polarizing member and to be reflected and transmitted. Is separated into light and its transmitted circularly polarized light is 1
The light is linearly polarized through the 波長 wavelength plate 2, passes through the polarizing plate 3 with little absorption loss, enters the liquid crystal cell 4, and emits display light through the polarizing plate 5 on the viewing side.

In the above, the absorption loss by the polarizing plate 3 is small, and the reflected light by the cholesteric liquid crystal layer 1 is inverted by the reflecting layer 9 on the lower surface side of the light guide plate, re-enters the cholesteric liquid crystal layer and is transmitted, and the reflected light The brightness of the liquid crystal display device can be improved, for example, by improving the light use efficiency by using the light emitting device.

When forming the liquid crystal display device as in the example of FIG. 2, suitable components used for forming the liquid crystal display device, such as a light diffusion sheet, a condensing sheet such as a prism sheet and a lens sheet, and a backlight, are used. One or two or more kinds can be arranged at an appropriate position, and another optical sheet such as a compensating retardation plate can be arranged.

The above-mentioned compensating retardation plate is used as necessary for the purpose of, for example, improving the viewing characteristics by compensating the phase difference by the liquid crystal cell. Usually, the polarizing plate on the light incident side or / and the viewing side is connected to the liquid crystal cell. Placed between. At the time of the disposition, it may be used by being previously laminated and integrated with a polarizing member or a polarizing plate. As the compensating retardation plate, a birefringent film or an oriented liquid crystal layer according to the above-mentioned 波長 wavelength plate having an appropriate retardation can be used, and for the purpose of controlling optical characteristics such as retardation. Two or more retardation layers may be laminated.

[0038]

Example 1 A cholesteric liquid crystal polymer was superposed on a cellulose triacetate film (UZ40, manufactured by FUJIFILM Corporation) having a thickness of 40 μm via a rubbing alignment film, and the reflection center wavelengths obtained by the alignment treatment were 760 nm and 650 nm. 550 nm or 430
When the main refractive indices in the plane and in the thickness direction are nx, ny, and nz, respectively, via an acrylic adhesive layer on the cholesteric liquid crystal layer having a four-layer structure of nm, the formula is (nx-nz) /
A quarter wave plate having an Nz of -1.5 defined by (nx-ny) is adhered, and a polarizing plate is bonded and laminated on the quarter wave plate via an acrylic adhesive layer to form a polarizing member. I got

Next, the above-mentioned polarizing member was adhered to the light incident side of a 14 inch TFT liquid crystal cell using a 0.7 mm thick glass plate as a cell substrate with an acrylic adhesive layer through the polarizing plate side. Then, a polarizing plate on the viewing side was bonded to the other surface of the cell via an acrylic adhesive layer to obtain a liquid crystal panel. As the polarizing plate on the light incident side and the viewing side, a transparent protective layer made of UZ40 was bonded to both surfaces of a polyvinyl alcohol-based polarizing film via a polyvinyl alcohol-based adhesive layer.

COMPARATIVE EXAMPLE 1 A transparent substrate supporting a cholesteric liquid crystal layer had a thickness of 80 μm.
m cellulose triacetate film (Fujifilm Corp., U
A polarizing member and a liquid crystal panel were obtained according to Example 1 except that Z80) was used.

Comparative Example 2 As a polarizing plate on the light incident side and on the viewing side, a transparent protective layer made of the aforementioned UZ80 was bonded to both surfaces of a polyvinyl alcohol-based polarizing film via a polyvinyl alcohol-based adhesive layer (manufactured by Nitto Denko Corporation). , SEG1425DU) according to Example 1 except that a polarizing member and a liquid crystal panel were obtained.

Comparative Example 3 UZ80 was used as a transparent base material for supporting a cholesteric liquid crystal layer, and the above-mentioned SE was used as a polarizing plate on the light incident side and the viewing side.
A polarizing member and a liquid crystal panel were obtained according to Example 1, except that G1425DU was used.

Evaluation Test The liquid crystal panels obtained in the examples and comparative examples were left in a heating atmosphere of 70 ° C. or a humidified atmosphere of 60 ° C. and 90% RH for 500 hours, taken out, and the amount of warpage was measured. The results are shown in the following table.

Transparent substrate thickness Transparent protective layer thickness Warpage during heating Warpage during humidification Example 1 40 μm 40 μm 0.09 mm 0.05 mm Comparative Example 1 80 μm 40 μm 0.21 mm 0.12 mm Comparative Example 2 40 μm 80 μm 0.32 mm 0 .18 mm Comparative Example 3 80 μm 80 μm 0.45 mm 0.25 mm

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of an example of a liquid crystal panel (polarizing member).

FIG. 2 is a cross-sectional view of an example of a liquid crystal display device.

[Explanation of symbols]

 1: Cholesteric liquid crystal layer 11: Transparent substrate 2: 1/4 wavelength plate 3, 5: Polarizing plate 33, 53: Polarizing film 32, 34, 52, 54: Transparent protective layer 21, 31, 35, 51: Adhesive layer 4: Liquid crystal cell 8: Surface light source

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2H049 BA02 BA07 BA25 BA46 BB03 BB33 BB43 BB49 BB63 BB65 2H088 EA45 FA16 FA18 FA24 GA03 HA21 JA15 MA16 2H091 FA08Y FA11Y FA37X FB02 FB12 FD06 FD16 GA16 GA17 LA18 LA04

Claims (4)

[Claims] 1. A laminate comprising a cholesteric liquid crystal layer adhered and supported on a transparent substrate, a quarter-wave plate, and a polarizing plate having a polarizing film protected by a transparent protective layer adhered via an adhesive layer, The thickness of the transparent substrate and the transparent protective layer is 50 μ
m or less. 2. The polarizing member according to claim 1, which is bonded to a light incident side of a liquid crystal cell via an adhesive layer, and the polarizing film has a thickness of 5 mm.
A liquid crystal panel comprising a polarizing plate protected by a transparent protective layer having a thickness of 0 μm or less and adhered to the visible side of the cell via an adhesive layer. 3. The liquid crystal panel according to claim 2, wherein the polarizing plate on the viewing side has an antiglare layer or an antireflection layer on the surface. 4. A liquid crystal display device comprising the liquid crystal panel according to claim 2.