JP2000162441A - Polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate capable of preventing a polarized light separation sheet from being damaged even when the sheet is arranged adjacently to it and of effectively preventing its sticking. SOLUTION: A polarizing plate is provided with a superposing layer (s) with a surface relief structure on its one or both surfaces. The superposing layer is formed by installing a resin layer 12, having a surface hardness of 3B to HB and a thickness of 0.5 to 2 μm, on a minute irregular structure 13, having a center line average roughness of 0.2 to 0.8 μm and a surface hardness of H to 4H expressed in pencil hardness. As a result, the sticking of the polarizing plate can be prevented, and the damage to an adjacent optical sheet can be prevented, even when it consists of a soft film, to form a liquid crystal display device being excellent in luminance, display quality etc.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polarizing plate which is capable of preventing sticking while preventing adjacent optical sheets from being damaged and is suitable for forming a liquid crystal display.

[0002]

2. Description of the Related Art There has been proposed a liquid crystal display device in which a polarizing plate and a liquid crystal cell are sequentially arranged on a backlight via an optical sheet made of, for example, a diffusion sheet, a condensing sheet, or a polarization separation sheet. In such an arrangement structure, after the light emitted from the backlight is diffused by the diffusion sheet, the light path is controlled by the light-collecting sheet and introduced into the polarization separation sheet, and the emitted light is converted into polarized light and introduced into the polarizing plate. Thus, the light use efficiency is improved, and the brightness of the liquid crystal display device is improved. However, the polarizing plate and the adjacent optical sheet come into close contact with each other, causing a sticking phenomenon, and there is a problem that display quality is deteriorated.

In view of the above, the present inventors have conventionally known an anti-glare polarizing plate which is disposed on the viewing side of a display device for the purpose of preventing glare and the like, in order to prevent sticking between the polarizing plate and an adjacent optical sheet. An attempt was made to dispose an object having an uneven structure on the light source side of a liquid crystal cell.

However, although sticking was prevented by this, it was found that there was a problem that the adjacent optical sheet was damaged due to scratches or the like due to the uneven structure on the antiglare surface of the polarizing plate. In particular, when the above-mentioned polarized light separating sheet is adjacent to the polarizing plate, such a polarized light separating sheet has a smooth surface such as a linearly polarized light separating sheet having a multilayer film having a refractive index anisotropy or a circularly polarized light separating sheet having a cholesteric liquid crystal layer. On the other hand, sticking is likely to occur, but the soft film is easily scratched, and the scratch becomes a scattering point or the like, impairing the optical function and significantly deteriorating the display quality.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to develop a polarizing plate which can be prevented from being damaged even if it is disposed adjacent to a polarization separating sheet and can effectively prevent sticking.

[0006]

According to the present invention, a center line average roughness is 0.2
The surface hardness is 3B-HB in pencil hardness on the surface of the fine unevenness structure of -0.8H and the surface hardness is H-4H in pencil hardness.
The present invention provides a polarizing plate characterized by having a superimposed layer having a surface irregularity structure provided with a resin layer having a thickness of 0.5 to 2 μm on one surface or both surfaces.

[0007]

According to the present invention, sticking with an adjacent optical sheet can be effectively prevented on the basis of the above-mentioned uneven surface structure comprising a superimposed layer of two hard and soft layers, and the adjacent optical sheet is a polarized light separating sheet. A polarizing plate capable of forming a liquid crystal display device having excellent brightness, display quality, and the like can be obtained by preventing the film from being damaged even when the film is made of a soft film such as

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The polarizing plate according to the present invention has a center line average roughness of 0.2 to 0.8 μm and a surface hardness of H in pencil hardness.
One or both sides having a superimposed layer of a surface uneven structure in which a resin layer having a surface hardness of 3B to HB and a thickness of 0.5 to 2 μm is provided on a fine uneven structure surface of 4H to 4H in pencil hardness. Consists of An example is shown in FIG. 1 is a polarizing plate,
12 is a resin layer, 11 is an uneven structure surface of the surface,
Reference numeral 13 denotes a fine uneven structure surface that supports the resin layer 12.

As the polarizing plate to be provided with the surface uneven structure, an appropriate polarizing plate can be used, and the kind thereof is not particularly limited. By the way, for example, hydrophilic polymer films such as polyvinyl alcohol-based films, partially formalized polyvinyl alcohol-based films, ethylene-vinyl acetate copolymer-based partially saponified films, and dichroic dyes such as iodine and dichroic dyes Examples of the film include a film obtained by adsorbing a substance and stretching, and a polarizing film such as a polyene oriented film such as a polyvinyl alcohol dehydration product or a polyvinyl chloride dehydrochlorination product. The thickness of the polarizing film is 5
Generally, but is not limited to ８０80 μm.

Further, as shown in FIG.
A transparent protective layer 1 consisting of a polymer coating layer, a film laminating layer, etc. on one or both sides for the purpose of protection such as water resistance.
Also provided are those provided with 4,16. For forming the transparent protective layer, an appropriate material such as a transparent polymer can be used, but a material having excellent transparency, mechanical strength, heat stability, moisture shielding property and the like can be preferably used. In many cases, the transparent protective layer is preferably as small as possible in optical anisotropy such as retardation. The thickness of the transparent protective layer is generally from 10 to 300 μm, but is not limited thereto.

As the polymer forming the transparent protective layer, for example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as cellulose diacetate and cellulose triacetate, polycarbonate polymers and polymethyl methacrylate ( Acrylic polymers such as PMMA) and styrene polymers such as polystyrene and acrylonitrile-styrene copolymer (AS resin).

Further, olefin polymers such as polyethylene and polypropylene, polyolefins having a cyclo or norbornene structure, and ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, and the like. Sulfone polymer, polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer And a blend of the above-mentioned polymers are also examples of the polymer forming the transparent protective layer.

As shown in the drawing, the polarizing plate according to the present invention has a surface hardness of 0.2 to 0.8 μm and a surface hardness of H to 4H in pencil hardness of H to 4H. Has a resin layer 12 having a pencil hardness of 3B to HB and a thickness of 0.5 to 2 μm, and a superimposed layer having an uneven structure 11 on the surface. In the illustrated example, such a superimposed layer is provided on one side, but may be provided on both sides of the polarizing plate in the present invention.

If the average roughness of the center line of the fine uneven structure surface supporting the resin layer is less than 0.2 μm, sticking cannot be prevented when the resin layer is provided thereon,
If it exceeds, even if a resin layer is provided thereon, damage occurs. If the surface hardness of the fine uneven structure surface is less than H in pencil hardness, the uneven structure on the surface of the resin layer is apt to be scratched, and the handleability at the time of work or the like is reduced, and if it exceeds 4H, the resin layer is formed thereon. Even if provided, the adjacent optical sheet will be damaged. A fine uneven structure surface preferable in terms of the balance between scratch prevention and sticking prevention has a center line average roughness of 0.7 μm or less, particularly 0.25 to 0.65 μm, and a surface hardness based on pencil hardness of 2H or more. 3H.

The fine uneven surface of the polarizing plate may have any of the above-mentioned characteristics, and may be formed by an appropriate method. By the way, as an example, a fine unevenness structure is given to the surface by roughening treatment by an appropriate method such as sand blasting, embossing roll, chemical etching, etc., and a fine unevenness structure is given to the surface by a transfer method using a mold. And a resin layer containing fine particles dispersed therein. Therefore, the fine uneven structure surface may be a polarizing plate in which a fine uneven structure is imparted to the surface of the transparent protective layer in the above-described polarizing plate as shown in the figure.

The surface of the fine uneven structure is formed on the transparent protective layers 14 and 16 of the polarizing plate by an additional layer such as a coating layer of the resin layer or on the surface of the polymer layer applied to the transparent protective layer. , Or a layer provided with a polymer coating layer on a transparent protective layer having a fine uneven structure on the surface.
The fine concavo-convex structure may be formed as a layer in which two or more of the above-described states are combined.

In the above, it is preferable to use a resin layer containing fine particles, which also serves as a transparent protective layer of the polarizing plate or is formed as a layer replacing the transparent protective layer, from the viewpoint of the above-described formability of the unevenness characteristics. The resin layer may be, for example, a method in which fine particles are dispersed and contained in a resin solution and coated on a polarizing plate by an appropriate method such as a doctor blade method or a gravure roll coater method to form a coating film, or a method containing fine particles. Can be formed by an appropriate method such as a method of forming a resin film in advance and bonding it to a polarizing plate.

As the resin forming the resin layer, any of the polymers exemplified for the transparent protective layer described above can be appropriately used depending on its hardness and the like. An ultraviolet-curable resin is preferably used. According to this, a layer composed of an ultraviolet-curable resin layer containing fine particles can be efficiently formed by a simple processing operation as required in the curing treatment of the coating layer by ultraviolet irradiation. It is also easy to form an ultraviolet-curable resin layer on the surface of the roughened transparent protective layer and reflect the surface irregularities of the transparent protective layer on the surface.

Examples of the UV-curable resin include polyester-based, acrylic-based, urethane-based and amide-based resins.
An appropriate compound such as a compound obtained by compounding an ultraviolet polymerization initiator with a monomer, oligomer, or polymer capable of forming a resin such as a silicone-based or epoxy-based resin and forming a resin layer by a curing treatment by ultraviolet irradiation is used. sell.

The UV-curable resin which can be preferably used is, for example, an acrylic monomer or oligomer having an ultraviolet-polymerizable functional group, especially having 2 or more, especially 3 to 6, acrylic monomers or oligomers. It is excellent in adhesion to the polarizing plate surface, transparency and hard coat properties, and when fine particles are contained, its dispersibility and satisfactory hardness of the cured film.

Examples of the fine particles include inorganic particles which may be conductive, such as silica, alumina, titania, zirconia, calcium oxide, tin oxide, indium oxide, cadmium oxide, and antimony oxide, PMMA, polyurethane, and polystyrene. Suitable particles such as crosslinked or uncrosslinked organic particles made of various polymers such as melamine resin and the like, especially organic particles that do not dissolve in the resin before curing can be used.

The fine particles to be used may be those having an appropriate shape such as spherical particles or pulverized particles. However, the average particle diameter is preferably 0.1 to prevent a good balance between scratch prevention and sticking prevention. ~ 15μm, especially 0.5 ~
Those having a thickness of 10 μm, particularly 1 to 8 μm are preferred.

The resin layer provided on the fine uneven structure surface has a pencil hardness of 3B to HB and a thickness of 0.5 to 2 μm.
m is formed. If the hardness is less than 3B, the uneven structure on the surface is apt to be scratched, and the handleability at the time of work or the like is reduced. If the hardness exceeds HB, the adjacent optical sheet is scratched. On the other hand, if the thickness is less than 0.5 μm, the adjacent optical sheet will be damaged, and if it exceeds 2 μm, the uneven structure on the fine uneven structure on the lower surface will be buried, and a surface uneven structure that can prevent sticking will not be formed.

From the viewpoint of the balance between the prevention of scratches and the prevention of sticking, a preferred resin layer has a surface hardness of 2B to B by pencil hardness and a thickness of 0.7 to 1.8 μm.
Further, the preferable uneven structure in which the uneven structure of the fine uneven structure on the lower surface is reflected on the surface of the resin layer is 0.02 μm or more based on the center line average roughness, preferably 0.05 to 0.8 μm, particularly 0.1 to 0.8 μm. 1 to 0.6 μm.

The resin layer can be formed by a method of forming a resin layer containing no fine particles according to the method of forming the fine uneven structure surface described above. When an ultraviolet-curable resin is used, a resin having one or two ultraviolet-polymerizable functional groups can be preferably used from the viewpoint of achieving the hardness.

The polarizing plate may be provided with an adhesive layer 17 as required as shown in FIG. The purpose of this adhesive layer is to adhere the polarizing plate to another member such as a liquid crystal cell. The adhesive layer can be formed of a suitable adhesive such as an acrylic-based, rubber-based, or silicone-based adhesive or a hot-melt-based adhesive, and preferably has excellent transparency and weather resistance.

The polarizing plate according to the present invention can be used as an elliptically polarizing plate bonded to a retardation plate, if necessary, for various uses according to the prior art such as a display device. In particular, when an optical sheet is arranged adjacent to a polarizing plate as in a liquid crystal display device, it is necessary to prevent the optical sheet from being damaged and to prevent sticking with an adjacent optical sheet. It can be preferably used. In that case, the polarizing plate is arranged so that its resin layer surface is located between adjacent optical sheets.

FIG. 2 illustrates a liquid crystal display device in which the polarizing plate 1 according to the present invention is arranged. The light diffusing sheet 7, the light condensing sheet 6, and the polarization separating sheet 5 are sequentially placed on the light emitting surface of the backlight 8, and the polarizing plate 1 is disposed thereon, and the liquid crystal cell 4 is disposed via the adhesive layer 3. The liquid crystal cell is adhered, and the polarizing plate 2 is adhered to the liquid crystal cell via the adhesive layer 3.

In the above description, the light diffusion sheet, the light condensing sheet and the polarized light separating sheet are optical sheets. In the illustrated example, the polarized light separating sheet 5 is an optical sheet adjacent to the polarizing plate 1. Therefore, the polarizing plate 1 is arranged such that the surface 11 on which the resin layer is provided is on the side of the polarized light separating sheet. As described above, in a liquid crystal display device, a structure for preventing sticking and scratching by disposing the polarizing plate according to the present invention between an optical sheet and a liquid crystal cell mounted without an adhesive layer is generally used. Further, a method of arranging the polarizing plate according to the present invention on the viewing back side of the liquid crystal cell as shown in the figure is generally used, but it is not limited to the arrangement on the viewing side of the liquid crystal cell.

The above-mentioned liquid crystal cell has a structure in which a liquid crystal layer 43 is sealed between cell substrates 42 each having a transparent electrode inside, and a color filter 41 is provided on the viewing side. Further, the backlight 8 is provided on a bottom surface of a light guide plate 81 having a light source 82 surrounded by a holder 83 disposed on a side surface thereof.
The light-collecting sheet 6 above the light-collecting sheet 6 includes prism sheets 6a and 6b arranged so that their ridge lines intersect. Further, the polarizing plate 2 on the viewing side has an anti-glare layer 21 on its surface.

According to the liquid crystal display device described above, the light emitted from the backlight 8 is diffused by the light diffusion sheet 7 and enters the condensing sheet 6, whereupon the optical path is controlled and then reflected by the polarization separation sheet 5. The light is separated into light and transmitted light and is converted into polarized light. The transmitted polarized light passes through the polarizing plate 1 with little absorption loss, passes through the liquid crystal layer, and the display light is emitted through the polarizing plate 2 on the viewing side. Is done. In that case, the absorption loss by the polarizing plate 1 is small, and the reflected polarized light by the polarized light separating sheet is reflected and inverted by the reflective layer 84 of the light guide plate, re-enters the polarized light separating sheet, and is transmitted. The luminance of the liquid crystal display device can be improved by improving the use efficiency of the liquid crystal display device.

In the above-described example, the polarization separating sheet is an optical sheet adjacent to the polarizing plate. However, the present invention is not limited to this. The optical sheet adjacent to the polarizing plate may be a liquid crystal display device to be formed. It may be an appropriate one according to the form such as.

[0033]

EXAMPLE 1 100 parts (parts by weight, hereinafter the same) of a urethane acrylate-based UV-curable resin having 3 to 6 unsaturated bonds in the molecule, 20 parts of silica particles having an average particle size of 5 μm, and UV polymerization initiation 50 parts by weight of solid content obtained by mixing 3 parts of the agent via a solvent
Is coated with a bar coater on one side of a polarizing plate having a 50 μm-thick triacetylcellulose film adhered to both sides of an iodine-based polyvinyl alcohol-type polarizing film via a polyvinyl alcohol-based adhesive layer, dried, and cured via ultraviolet rays. Urethane acrylate ultraviolet rays having a center line average roughness of 0.3 μm, a surface hardness of 2H by pencil hardness, and a fine uneven structure surface having 1 to 2 unsaturated bonds in the molecule thereon A solution having a solid content of 50% by weight, in which 100 parts of the curable resin and 3 parts of an ultraviolet polymerization initiator are mixed via a solvent, is applied by a bar coater, dried, and then cured through ultraviolet rays. To form a resin layer having a thickness of 1.5 μm to obtain a polarizing plate. The uneven structure on the surface of the resin layer is 0.2 μm based on the center line average roughness.
Met.

Next, a polarizing plate is adhered to a liquid crystal cell via an acrylic pressure-sensitive adhesive layer so that the resin layer surface faces outward,
Forming a color liquid crystal display device according to FIG. 2 mounted on a linearly polarized light separating sheet having a refractive index anisotropic multilayer film or a circularly polarized light separating sheet having a cholesteric liquid crystal polymer layer via the resin layer surface. As a result, no sticking occurred and the display quality was excellent. Further, when the apparatus was disassembled and confirmed, no damage was found on any of the polarized light separating sheets.

Comparative Example 1 The surface hardness was 2H in pencil hardness according to Example 1, except that the resin layer was formed using a urethane acrylate UV curable resin having 3 to 6 unsaturated bonds in the molecule. When a polarizing plate having a concave-convex structure having a center line average roughness of 0.2 μm on the surface thereof was obtained and a color liquid crystal display device was formed using the polarizing plate, sticking did not occur, but the display was difficult to see. When decomposed, any of the polarized light separating sheets was damaged.

Comparative Example 2 A fine uneven surface having a center line average roughness of 1.1 μm and a surface hardness of 2H in pencil hardness was prepared in the same manner as in Example 1 except that silica particles having an average particle diameter of 20 μm were used. When a polarizing plate was obtained by providing a resin layer thereon and forming a color liquid crystal display using the same, sticking did not occur, but the display was difficult to see, and when the device was disassembled, Of the polarized light separating sheet was also damaged. The uneven structure on the surface of the resin layer was 1.0 μm based on the center line average roughness.

Comparative Example 3 The thickness of the resin layer was adjusted to 5 μm using a dispersion having a solid content of 70% by weight.
A polarizing plate was obtained in the same manner as in Example 1 except that m was used, and a color liquid crystal display device was formed using the polarizing plate. The device was disassembled, but none of the polarized light separating sheets was damaged. The uneven structure on the surface of the resin layer was 0.01 μm or less based on the center line average roughness.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment.

FIG. 2 is a sectional view of an application example.

[Explanation of symbols]

 1: Polarizing plate 12: Resin layer (11: uneven surface of surface) 14, 16: Transparent protective layer (13: surface of fine uneven structure) 15: Polarizing film 17: Adhesive layer 4: Liquid crystal cell 5, 6, 7: Optical sheet

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masamori Masada 1-1-2 Shimohozumi, Ibaraki-shi, Osaka Nitto Denko Corporation F-term (reference) 2H049 BA02 BB23 BB43 BB51 BB63 BB63 BC22 2H091 FA08X FA08Z FA32Z FA41Z FB02 FB04 FC23 FC25 FC26 FD06 GA16

Claims (2)

[Claims] 1. A fine unevenness surface having a center line average roughness of 0.2 to 0.8 μm and a surface hardness of H to 4H in pencil hardness and a surface hardness of 3B to HB in pencil hardness. 0.5
A polarizing plate comprising a superimposed layer having a surface irregularity structure provided with a resin layer of about 2 μm on one or both sides. 2. The polarizing plate according to claim 1, wherein the polarizing plate is disposed between the liquid crystal cell and the optical sheet on the viewing back side of the liquid crystal cell.