KR20100036956A - Polarizing plate, liquid crystal panel and liquid crystal display - Google Patents

Abstract

PURPOSE: By laminating the diffusion film in one side of the Polaroid film and laminating the optically compensatory film or the protection film in the opposite surface of the Polaroid film polarizer, and the liquid crystal panel and liquid crystal display can enhance the luminance at the front side of screen. CONSTITUTION: A polaroid film(100) is included of the axial stretching polyvinylalcohol resin film in which iodine or the dichroic dyes is absorbed and originated. The diffusion film has the optical diffusion. And it is at least laminated of the Polaroid film in one side. The transmission light(102) enters a company to the angle sloping from the normal direction of the diffusion film 40° to 60° in the diffusion film. The diffusion film is laminated in one side of the Polaroid film.

Description

POLARIZING PLATE, LIQUID CRYSTAL PANEL AND LIQUID CRYSTAL DISPLAY}

The present invention relates to a polarizing plate having a diffusing film having light diffusing property laminated on one or both surfaces of a polarizing film, and a liquid crystal panel and a liquid crystal display device using the same.

BACKGROUND ART Liquid crystal display devices are rapidly expanding in use as thin display devices such as liquid crystal televisions, liquid crystal monitors, and personal computers. In particular, the market expansion of liquid crystal television is remarkable, and the demand for cost reduction is also very high.

A normal liquid crystal display device is composed of a backlight including a cold cathode tube or LED, a light diffusion plate, one or more light diffusion sheets, a back side polarizing plate, a liquid crystal cell, and a viewing side polarizing plate. In the case of large screen liquid crystal television applications, the necessity of making it thin and using it as a wall-mounted television is presently developed. In this case, the thickness and the number of members to be used corresponding to the thinning of the liquid crystal television are required. In response to such a request, a technique of reducing the number of parts by omitting one or a plurality of light diffusion sheets by providing light diffusivity to the rear polarizer itself disposed between the liquid crystal cell and the backlight is known (for example, JP-A-11-183712 (Patent Document 1), JP-A-2000-75133 (Patent Document 2), JP-A-2000-75134 (Patent Document 3), and Japanese Patent JP-A-2000-75135 (Patent Document 4), JP-A-2000-75136 (Patent Document 5), JP-A-2000-75137 (Patent Document 6).

However, in the liquid crystal display device using the conventional back side polarizing plate, there existed a problem that the brightness in the front of a screen of a liquid crystal display device was low.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and an object thereof is to provide a polarizing plate having a high luminance at the front of a screen of a liquid crystal display device and obtaining a bright image, particularly a rear side polarizing plate disposed between a liquid crystal cell and a backlight. will be. Another object of the present invention is to provide a liquid crystal panel and a liquid crystal display device using the polarizing plate.

According to the present invention, there is provided a polarizing film made of a uniaxially stretched polyvinyl alcohol-based resin film in which an iodine or a dichroic dye is adsorbed and oriented, and a diffusing film having a light diffusing property laminated on at least one side of the polarizing film. The diffusing film has a light intensity A in a direction of 10 ° normal from the linear transmission direction and a 10 ° diffusion direction from the linear transmission direction in the transmitted light of light incident on the diffusion film at an angle inclined 40 ° to 60 ° from its normal direction. A polarizing plate having a ratio A / B of light intensity B of greater than 1 is provided.

The diffusing film used for the polarizing plate of the present invention is obtained from the light intensity A in the direction of the 10 ° normal line from the linear transmission direction and the linear transmission direction in the transmission light of light incident on the diffusion film at an angle inclined 20 ° to 60 ° from the normal direction thereof. It is preferable that ratio A / B of the light intensity B in a 10 degree diffused film direction direction is larger than 1.

In the polarizing plate of the present invention, the diffusion film is preferably laminated on one side of the polarizing film, and the optical compensation film or protective film is laminated on the other side.

The polarizing plate of this invention can be used suitably as a back side polarizing plate arrange | positioned between the liquid crystal cell with which a liquid crystal display device is equipped, and a backlight.

Moreover, according to this invention, it is a liquid crystal panel provided with the liquid crystal cell and the polarizing plate of the said invention laminated | stacked on the said liquid crystal cell, A diffusion film is laminated | stacked on one side of the polarizing film in the said polarizing plate, and it diffuses in a polarizing film There is provided a liquid crystal panel in which liquid crystal cells are laminated on a surface opposite to a surface on which a film is laminated.

Moreover, according to this invention, it is a liquid crystal display device provided with a backlight, a light-diffusion plate, and the liquid crystal panel of this invention in this order, The said liquid crystal panel is a liquid crystal display by which the diffuser film of a polarizing plate opposes a light-diffusion plate. Apparatus and a liquid crystal display device comprising a backlight, a light diffusion plate, a light diffusion sheet, and a liquid crystal panel of the present invention in this order, wherein the liquid crystal panel is a liquid crystal display in which the diffusion film of the polarizing plate is opposed to the light diffusion sheet. An apparatus is provided.

According to the polarizing plate and liquid crystal panel of this invention, the brightness in the front of the screen of the liquid crystal display device to which it is applied can be made high, and it becomes possible to provide the liquid crystal display device excellent in image quality. Moreover, according to this invention, it becomes possible to aim at thickness reduction of a liquid crystal display device, and reduction of the number of members. Such a liquid crystal display device of the present invention can be suitably applied to a liquid crystal display device for a large screen liquid crystal television, particularly a liquid crystal display device for a wall-mounted liquid crystal television.

<Polarizing plate>

(Polarizing film)

Specifically, the polarizing film used for the polarizing plate of this invention adsorbs and oriented the dichroic dye to the uniaxially stretched polyvinyl alcohol-type resin film. As polyvinyl alcohol-type resin which comprises a polyvinyl alcohol-type resin film, what saponified polyvinyl acetate type resin can be used. As polyvinyl acetate type resin, besides polyvinyl acetate which is a homopolymer of vinyl acetate, the copolymer of vinyl acetate and the other monomer copolymerizable with this, for example, ethylene-vinyl acetate copolymer, etc. are mentioned. As another monomer copolymerizable with vinyl acetate, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamide which has an ammonium group, etc. are mentioned, for example.

The saponification degree of polyvinyl alcohol-type resin is about 85-100 mol% normally, and 98 mol% or more is preferable. The polyvinyl alcohol-based resin may be modified. For example, polyvinyl formal, polyvinyl acetal, polyvinyl butyral and the like modified with aldehydes may also be used. The polymerization degree of polyvinyl alcohol-type resin is about 1000-10000 normally, and about 1500-5000 is preferable.

What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method of forming a polyvinyl alcohol-type resin into a film is not specifically limited, It can form into a film by a conventionally well-known appropriate method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 10-150 micrometers.

The polarizing film is usually a step of dyeing a master film made of the above-described polyvinyl alcohol-based resin with a dichroic dye to adsorb the dichroic dye (dyeing step), and a polyvinyl alcohol-based resin to which the dichroic dye is adsorbed. It manufactures through the process of processing a film with boric-acid aqueous solution (boric acid treatment process), and the process of washing with water after the process by this boric-acid aqueous solution (water washing process process).

In addition, at the time of manufacture of a polarizing film, although a polyvinyl alcohol-type resin film is uniaxially stretched normally, this uniaxial stretching may be performed before a dyeing process, may be performed in a dyeing process, or may be performed after a dyeing process. In the case of performing uniaxial stretching after the dyeing treatment step, this uniaxial stretching may be performed before the boric acid treatment step or may be performed during the boric acid treatment step. Of course, it is also possible to uniaxially stretch in these several steps. Uniaxial stretching may be made to extend | stretch uniaxially between the rolls with which the circumferential speed differs, and may make it extend | stretch uniaxially using a thermal roll. Moreover, it may be dry drawing which extends | stretches in air | atmosphere, or it may be wet drawing which extends in the state swelled with a solvent. The draw ratio is usually about 3 to 8 times.

Dyeing by the dichroic dye of the polyvinyl alcohol-type resin film in a dyeing process is performed by immersing a polyvinyl alcohol-type resin film in the aqueous solution containing a dichroic dye, for example. As a dichroic dye, iodine, a dichroic dye, etc. are used, for example. Dichroic dyes include dichroic direct dyes including, for example, dichroic compounds including disazo compounds such as C.I.DIRECT RED 39, tris azo, tetrakis azo compounds and the like. In addition, it is preferable that the polyvinyl alcohol-based resin film is subjected to an immersion treatment in water before the dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. When iodine is used as a dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C, and the immersion time (dyeing time) in the aqueous solution is usually 20 to 1800 seconds.

On the other hand, when using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic dye is employ | adopted normally. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight, particularly preferably 1 × 10 ^-3 per 100 parts by weight of water. To 1 × 10 ⁻² parts by weight. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. When using a dichroic dye as a dichroic dye, the temperature of the dye aqueous solution used for dyeing is 20-80 degreeC normally, and the immersion time (dyeing time) in this aqueous solution is 10 to 1800 second normally.

A boric acid treatment process is performed by immersing the polyvinyl alcohol-type resin film dyed by the dichroic dye in boric acid containing aqueous solution. The amount of boric acid in the boric acid-containing aqueous solution is usually 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye in the above-mentioned dyeing treatment step, the boric acid-containing aqueous solution used in the boric acid treatment step preferably contains potassium iodide. In this case, the amount of potassium iodide in the aqueous solution containing boric acid is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. Immersion time in boric acid containing aqueous solution is 60-1200 second normally, Preferably it is 150-600 second, More preferably, it is 200-400 second. The temperature of the boric-acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

In the subsequent water washing process, the water washing process is performed by immersing the polyvinyl alcohol-type resin film after boric acid treatment mentioned above in water, for example. The temperature of the water in a water washing process is 5-40 degreeC normally, and immersion time is 1-120 second normally. After a water washing process, a drying process is normally performed and a polarizing film is obtained. A drying process can be performed using a hot air dryer, a far-infrared heater, etc. suitably, for example. The temperature of a drying process is 30-100 degreeC normally, Preferably it is 50-80 degreeC. The time of the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, boric acid treatment and water washing treatment to obtain a polarizing film. The thickness of this polarizing film is in the range of 5-40 micrometers normally. The polarizing plate of the present invention has a structure in which a diffusion film is laminated on at least one side of such a polarizing film.

(Diffusion film)

The diffusing film which has the light diffusivity used for the polarizing plate of this invention is a film which shows the specific light diffusivity mentioned later, and is a film for giving a light diffusing function to a polarizing plate. Here, when a film has "light diffusivity", when incident light (typically, light from a backlight) is incident from one side of the film and passes through the inside of the film, a straight line at the other side of the film It means that the transmitted light is observed also in a plurality of directions different from the transmission direction (the straight direction of the incident light).

The base material of the said diffusion film is not specifically limited, Various materials can be used. For example, synthetic polymers, such as polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, polyethylene naphthalate, polycarbonate, norbornene resin, polyurethane, polyacrylate, polymethyl methacrylate; Transparent polymer materials, such as natural polymers, such as a cellulose diacetate and a cellulose triacetate, can be used. Moreover, these polymer materials may contain additives, such as a ultraviolet absorber, antioxidant, and a plasticizer, as needed.

As a method of manufacturing a diffusion film based on these transparent polymer materials, For example, the method of containing a diffusing agent in a base film; A method of imparting a layer containing a diffusing agent to one or both surfaces of the base film surface; A method of roughening one or both surfaces of the base film surface (giving surface irregularities); And a method of photocuring a layer made of a photocurable resin composition containing at least two photopolymerizable monomers or oligomers having a difference in refractive index of a homopolymer obtained by homopolymerization. These methods may be used alone, or may be used in combination of two or more kinds thereof.

When employ | adopting the method of containing a diffusing agent in a base film, what is necessary is just to knead | mix a diffusing agent in the transparent polymeric material used as a base material previously, and to shape it into a film form by the casting method or the extrusion method. In the case of adopting a method of providing a layer containing a diffusing agent to one or both surfaces of the substrate film, first, the transparent polymer material is molded into a film by a casting method or an extrusion method, and then the resin liquid containing the diffusing agent is dispersed. Coating on a base film and drying or hardening this resin liquid can manufacture a diffusion film. Or by the coextrusion method using the transparent polymer material used as a base film, and the transparent polymer material knead | mixed the diffuser previously, the diffusion film which consists of a multilayered structure which laminated | stacked the layer containing a diffusing agent on the base film can be manufactured. It may be. In addition, when employ | adopting the method of roughening the surface of a base film, first, a transparent polymer material is shape | molded in the sheet form by the casting method or the extrusion method, and then to the embossing method by the embossing roll or the sand blasting method. The surface can be roughened to produce a diffusion film.

The diffusing agent is not particularly limited as long as it is colorless or white particles, and both organic particles and inorganic particles can be used. As organic particle | grains, the particle | grains which consist of high molecular compounds, such as polyolefin resin, such as polystyrene, polyethylene, and polypropylene, and an acrylic resin, are mentioned, for example, A crosslinked polymer may be sufficient. Moreover, the copolymer which copolymerizes 2 or more types of monomers chosen from ethylene, propylene, styrene, methyl methacrylate, benzoguanamine, formaldehyde, melamine, butadiene, etc. can also be used. Examples of the inorganic particles include particles made of silica, silicon, titanium oxide, and the like, and may also be glass beads.

As a resin liquid used by the method of coating the resin liquid which the said dispersing agent disperse | distributed on the base film, the resin liquid of solvent volatile form or water volatile form, and the thermosetting type or photocurable resin liquid can be used. Examples of the solvent volatile or water volatile resin liquid include polymers such as polyacrylate, polymethacrylate, polyvinyl chloride, polyvinyl acetate, cellulose and synthetic rubber, and alcohols such as methanol, ethanol, propanol and isopropanol; Cellosolves such as methyl cellosolve and ethyl cellosolve; Aromatic solvents such as toluene and xylene; Ethyl acetate and methylene chloride; What dissolved or disperse | distributed to the organic solvent, such as these, or water can be used. In the case where these solvent volatile or water volatile resin solutions are coated on a base film, the organic solvent or water is evaporated by drying to form a film. As a thermosetting resin liquid, the resin liquid etc. which mixed the liquid containing the compound which has an epoxy group, and the compound condensed with an epoxy group including an amine can be used. As a photocurable resin liquid, the resin liquid which added the well-known radical photopolymerization initiator to the compound which has an acrylate group, a methacrylate group, an aryl group, etc., and the photocationic polymerization initiator known to the compound which has a vinyl ether group or an epoxy group are used. The added resin liquid can be used. To these resin liquids, additives, such as an ultraviolet absorber and antioxidant, can be added as needed.

Here, the diffusion film used for the polarizing plate of this invention is characterized by having the specific light-diffusion characteristic with respect to the light which injects from the direction inclined from the normal line direction. That is, with reference to FIG. 1, it is 40 from the normal line 101 direction of the diffusion film 100 to the diffusion film 100 (the surface on the opposite side to the side where the polarizing film in the diffusion film 100 is laminated | stacked). Linear transmission direction (direct direction of the light 102) in the transmission light of the light 102 incident at an angle inclined in the range of ° to 60 ° (angle α = 40 ° to 60 ° in FIG. 1) The ratio A / B of the light intensity A in the 10 direction normal direction 104 from (103) and the light intensity B in the direction 105 near the 10 degree diffused film 100 from the linear transmission direction 103 is A / B> Satisfies 1 Light intensity ratio A / B becomes like this. Preferably it is 1.1 or more, More preferably, it is 1.5 or more. Incidentally, the incident angle α of the light 102 is 0 ° when parallel to the normal 101 of the diffusing film, and the light incident surface (the polarizing film in the diffusing film 100 is laminated) of the diffusing film 100 is laminated. 90 ° when parallel to the side). Further, the light intensity A and the light intensity B are measured for transmitted light on a plane including the incident light 102 and the normal 101 of the diffusing film.

If the diffusing film has such a light diffusing property, when the polarizing plate is applied to the liquid crystal display device as the back side polarizing plate, even when light of the backlight is incident in a direction inclined with respect to the polarizing plate, the normal direction of the polarizing plate, that is, Since more light is emitted toward the front of the screen, the brightness in the front of the screen becomes higher, so that a bright image can be obtained. In particular, when the angle α has the light diffusing property with respect to the incident light in the range of 40 ° to 60 °, the effect of improving the luminance in the front direction of the screen of the liquid crystal display device is large. Therefore, the diffusing film used for the polarizing plate of the present invention needs to have the light diffusivity with respect to incident light having at least the angle α of 40 ° to 60 °, and the light diffusion of incident light having a wide range of angle α. It is desirable to have sex. Specifically, in the case where the incident angle α of the incident light is within the range of 20 ° to 60 °, it is preferable to have the light diffusing property.

As a diffusing film which shows such specific light-diffusion property, the thing in which light incident surface (surface on the opposite side to the side where the polarizing film in a diffusion film is laminated | stacked) is near smooth is used preferably, for example. Examples of such a diffusion film include a film having a flat surface obtained by kneading a thermoplastic resin with a diffusion agent (resin bead) made of a resin having a refractive index different from that of the resin, followed by melt extrusion molding. As another example, light is applied to a photocurable resin composition containing at least two photopolymerizable monomers or oligomers each having a polymerizable carbon-carbon bond in a molecule and having a difference in refractive index of a homopolymer obtained by homopolymerization. It is possible to use a diffusion film obtained by irradiation, having a refractive index distribution therein, and having a flat surface.

It is preferable that it is 5% or more, and, as for the haze value of a diffusion film, it is more preferable that they are 15% or more and 90% or less. More preferably, they are 45% or more and 90% or less. In addition, the higher the total light transmittance of the diffusion film is, the more preferable. Specifically, the total light transmittance of the diffusion film is preferably 70% or more, more preferably 80% or more, particularly 85% or more.

Although the thickness of a diffusion film is not specifically limited, From the aspect of thin-weight reduction of a polarizing plate, it is preferable that they are 20 micrometers or more and about 200 micrometers or less, Furthermore, it is more preferable that they are 30 micrometers or more and 100 micrometers or less.

When laminating | stacking a diffuser film on both surfaces of a polarizing film, the layer of the adhesive agent or adhesive for bonding a liquid crystal cell and a polarizing plate may be formed on the one diffuser film. When laminating | stacking a diffusion film on one side of a polarizing film, the layer of the adhesive agent or adhesive for bonding a liquid crystal cell and a polarizing plate may be formed in the surface on the opposite side to the surface on which the said diffusion film in a polarizing film is bonded. . Moreover, the said diffusion film can be laminated | stacked on one side of a polarizing film, transparent films, such as a protective film and an optical compensation film, can be laminated | stacked on the other side, and a layer of an adhesive agent or an adhesive can be formed on the said transparent film. As a transparent film, polyester resin films, such as a cellulose resin film, such as a triacetyl cellulose film (TAC film), an olefin resin film, an acrylic resin film, and a polyethylene terephthalate, etc. are mentioned. Moreover, you may laminate | stack the optical functional film mentioned later on the said transparent film, and may form the layer of an adhesive agent or an adhesive on this optical functional film.

The cellulose resin constituting the cellulose resin film means a partial esterified product or a full esterified product of cellulose, and examples thereof include acetate esters of cellulose, propionic acid esters, butyric acid esters, and mixed esters thereof. More specifically, triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, cellulose acetate butyrate, etc. are mentioned. When forming such a cellulose resin into a film, well-known methods, such as the solvent casting method and the melt-extrusion method, are used suitably. A cellulose resin film can obtain a commercial item, for example, "Fuji tag TD80" (Fuji Film Co., Ltd. product), "Fuji tag TD80UF" (Fuji Film Co., Ltd. product), "Fuji tag TD80UZ" (Fuji tag) Film KK), "KC8UX2M" (made by Konica Minolta Opto Co., Ltd.), "KC8UY" (made by Konica Minolta Opto Co., Ltd.), etc. are mentioned.

Moreover, as an optical compensation film which consists of a cellulose resin film, For example, the film cellulose type which apply | coated the compound which has a phase difference adjustment function to the film cellulose resin film surface which contained the compound which has a phase difference adjustment function in the said cellulose resin film. The film etc. which are obtained by uniaxially stretching or biaxially stretching a resin film are mentioned. As an optical compensation film which consists of a cellulose resin film marketed, for example, "WV film Wide View Film" WV BZ 438 "" of Fuji Film Co., Ltd., "WV film Wide View Film" WV EA "", Konica "KC4FR-1", "KC4HR-1" by Minolta Opto Corporation, etc. are mentioned.

Although the thickness in particular of the protective film or optical compensation film which consists of cellulose resin films is not restrict | limited, It is preferable to exist in the range of 20-90 micrometers, and it is more preferable to exist in the range of 30-90 micrometers. The thinner the film, the harder the handling of the film, while the thicker the film, the poor the workability and the disadvantage of the thinner and thinner the polarizing plate obtained.

As an optical compensation film which consists of the said olefin resin film, the cycloolefin resin film uniaxially stretched or biaxially stretched is mentioned, for example. When using the polarizing plate of this invention for the liquid crystal panel for large liquid crystal televisions, especially the liquid crystal panel provided with the liquid crystal cell of a vertical alignment (VA) mode, as said optical compensation film, the extending | stretching product of a cycloolefin resin film is an optical characteristic and It is also preferable from the point of durability. Here, a cycloolefin resin film is a film which consists of thermoplastic resin which has a unit of the monomer which consists of cyclic olefins (cycloolefin), such as a norbornene and a polycyclic norbornene-type monomer, for example. The cycloolefin-based film may be a hydrogenated product of a ring-opening polymer using a single cycloolefin, or a ring-opening copolymer using two or more cycloolefins, or an addition copolymer of a cycloolefin with a chain olefin and / or an aromatic compound having a vinyl group. It may be. It is also effective that a polar group is introduced into the main chain or the side chain.

As a commercially available thermoplastic cycloolefin resin, "Topas" sold by Ticona, Germany, "Aton" sold by JSR Co., Ltd., are sold from Nihon Xeon Co., Ltd. "ZEONOR" and "ZEONEX", "Apel" (all brand names) sold by Mitsui Chemical Industries, Ltd., etc. are mentioned, These can be used preferably. A cycloolefin resin film can be obtained by forming such a cycloolefin resin into a film. As a film forming method, well-known methods, such as a solvent casting method and a melt extrusion method, are used suitably. In addition, for example, "Esshina" and "SCA40" sold by Sekisui Kagaku Kogyo Co., Ltd., "Zeonor Film" sold by Optes, "" sold by JSR Co., Ltd. The cycloolefin resin film formed into a film, such as "Aton film" (all product name), is also marketed, These can also be used preferably.

When the thickness of the optical compensation film which consists of an extended cycloolefin resin film is too thick, it will be inferior to workability, and also transparency will fall or it is about 20-80 micrometers from the point which is disadvantageous in thinning and thinning of a polarizing plate. It is preferable.

An adhesive agent is used normally for the bonding of the said polarizing film and a diffusion film, and the bonding of the protective film or optical compensation film laminated | stacked as needed, and a polarizing film. When the protective film or the optical compensation film is bonded to the polarizing film, the adhesive used for bonding the diffusion film and the adhesive film used for bonding the protective film or the optical compensation film may be the same kind of adhesive or different kinds of adhesives. As an adhesive agent used for the bonding of these films, the thing of the water system, ie, the thing which melt | dissolved the adhesive component in water, or the thing disperse | distributed to water is mentioned. For example, the resin composition using polyvinyl alcohol-type resin or urethane resin as an adhesive component is mentioned as a preferable adhesive agent.

In the case of using a polyvinyl alcohol-based resin as an adhesive component, the polyvinyl alcohol-based resin may be partially saponified polyvinyl alcohol, fully saponified polyvinyl alcohol, carboxyl group-modified polyvinyl alcohol, acetoacetyl group-modified polyvinyl alcohol, and methylol group-modified polyvinyl alcohol. Modified polyvinyl alcohol-based resins such as vinyl alcohol and amino group-modified polyvinyl alcohol may be used. Usually, the adhesive agent which uses polyvinyl alcohol-type resin as an adhesive component is manufactured as an aqueous solution of polyvinyl alcohol-type resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually 1 to 10 parts by weight, preferably 1 to 5 parts by weight with respect to 100 parts by weight of water.

In order to improve adhesiveness, it is preferable to add curable components, such as glyoxal and a water-soluble epoxy resin, and a crosslinking agent to the adhesive agent which uses polyvinyl alcohol-type resin as an adhesive component. As water-soluble epoxy resin, epichlorohydrin is made to react with the polyamide amine obtained by reaction of polyalkylene polyamines, such as diethylene triamine and triethylene tetramine, and dicarboxylic acids, such as adipic acid, for example. The polyamide polyamine epoxy resin obtained can be used preferably. As a commercial item of such a polyamide polyamine epoxy resin, "Smilles resin 650" (made by Sumika Chemtex), "Smiles resin 675" (made by Sumika Chemtex), "WS-525" (Nippon PMC Co., Ltd. product) etc. are mentioned. The addition amount (total amount when adding together) of these curable components and a crosslinking agent is 1-100 weight part normally with respect to 100 weight part of polyvinyl alcohol-type resins, Preferably it is 1-50 weight part. When there is little addition amount of the said curable component and crosslinking agent, the effect of adhesive improvement tends to become small, and when there is much addition amount of the said curable component and crosslinking agent, there exists a tendency for an adhesive bond layer to become weak.

Moreover, when using urethane resin as an adhesive component, the mixture of the polyester-type ionomer type urethane resin and the compound which has glycidyloxy group is mentioned as an example of a suitable adhesive composition. Here, polyester ionomer type urethane resin is a urethane resin which has a polyester frame | skeleton, and a small amount of ionic component (hydrophilic component) is introduce | transduced into this frame | skeleton. Such ionomer-type urethane resins are preferable as water-based adhesives because they are emulsified directly in water without using an emulsifier. The polyester ionomer-type urethane resin itself is well-known, for example, Unexamined-Japanese-Patent No. 7-97504 describes as an example of the polymer dispersing agent for disperse | distributing a phenolic resin in an aqueous medium, and also Japan Japanese Patent Laid-Open No. 2005-70140 and Japanese Patent Laid-Open No. 2005-208456 disclose a polyvinyl alcohol-based resin comprising a mixture of a polyester ionomer-type urethane resin and a compound having a glycidyloxy group as an adhesive. The aspect which bonds a cycloolefin resin film to a polarizing film is described.

As a method of apply | coating an adhesive agent to a polarizing film and / or the film bonded to this (diffusion film, a protective film, or an optical compensation film), what is necessary is just a generally known method, For example, the casting method, the Meyer bar coating method, the gravure coating A method, a Kanma coater method, a doctor blade method, a die coating method, an immersion coating method, a spraying method, and the like. The casting method is a method in which a film, which is a coated object, is moved in an approximately vertical direction, an approximately horizontal direction, or in an inclined direction between them, while flowing an adhesive agent on the surface thereof and widely applied. After apply | coating an adhesive agent, the polarizing film and the film bonded to this are superimposed, it is pinched by a nip roll etc., and the film is bonded. Bonding of the film using a nip roll, for example, after applying the adhesive, pressurized with a roll or the like and uniformly pressed, and spreading between the roll and the roll after applying the adhesive, pressurized by pressing and widened, etc. It can be adopted. In the former case, it is possible to use a metal, rubber | gum, etc. as a material of a roll. In the latter case, the plurality of rolls may be the same material or may be different materials.

In addition, the surface of an adhesive bond layer may be suitably subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment or the like for improving the adhesion. As a saponification process, the method of immersing in aqueous solution of alkalis, such as sodium hydroxide and potassium hydroxide, is mentioned.

After the said bonding, a polarizing plate can be obtained by drying and hardening an adhesive bond layer. This drying process is performed by spraying hot air, for example, and the temperature is normally in the range of 40-100 degreeC, Preferably it exists in the range of 60-100 degreeC. Moreover, drying time is 20 to 1200 second normally.

The thickness of the adhesive bond layer after drying is 0.001-5 micrometers normally, Preferably it is 0.01-2 micrometers, More preferably, it is 0.01-1 micrometer. When the thickness of an adhesive bond layer is thin, there exists a possibility that adhesiveness may be inadequate, and when the thickness of an adhesive bond layer is thick, there exists a possibility that the appearance defect of a polarizing plate may arise.

In addition, after the drying, curing at least half a day, preferably several days or more, at a temperature of room temperature or more may be obtained to obtain sufficient adhesive strength. Preferable curing temperature is the range of 30-50 degreeC, More preferably, it is 35-45 degreeC. When curing temperature is high, what is called a "winding-up" tends to occur in a roll winding state. In addition, the humidity at the time of curing is not specifically limited, The relative humidity should just be in the range of 0 to 70% RH. The curing time is usually 1 to 10 days, preferably 2 to 7 days.

Moreover, a photocurable adhesive agent can also be used as said adhesive agent. As a photocurable adhesive agent, the mixture of a photocurable epoxy resin, a photocationic polymerization initiator, etc. are mentioned, for example. When using a photocurable adhesive agent, a photocurable adhesive agent is hardened by irradiating an active energy ray. The light source of the active energy ray is not particularly limited, but an active energy ray having a luminescence distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave A mercury lamp, a metal halide lamp, etc. are preferable here.

Light irradiation intensity to a photocurable adhesive agent is suitably determined by the composition of this photocurable adhesive agent, Although it does not specifically limit, It is preferable that irradiation intensity of the wavelength range effective for activation of a polymerization initiator is 0.1-6000 mW / cm <^2> . Do. When the irradiation intensity is 0.1 mW / cm ² or more, the reaction time does not become too long, and the yellowing of the epoxy resin or the polarization film of the epoxy resin due to the heat generated when curing the photocurable adhesive and the heat radiated from the light source at 6000 mW / cm ² or less There is little possibility of causing deterioration. Although light irradiation time to a photocurable adhesive agent is controlled for every photocurable adhesive agent to harden, it does not restrict | limit, It is set so that accumulated light quantity expressed as a product of said irradiation intensity and irradiation time may be set to 10-10000 mJ / m <^2>. desirable. When the amount of accumulated light to the photocurable adhesive agent is 10 mJ / m ² or more, a sufficient amount of active species derived from the polymerization initiator is generated to reliably advance the curing reaction, and the irradiation time is too long at 10000 mJ / m ² or less. And good productivity can be maintained.

In addition, when curing a photocurable adhesive agent by irradiation of active energy rays, on the condition that the various functions of a polarizing plate, such as the polarization degree, the transmittance | permeability, and the color of a polarizing film, and the transparency of a diffusion film, a protective film, and an optical compensation film, do not fall, It is preferable to perform hardening.

In the polarizing plate of this invention, when laminating | stacking a diffusion film on both surfaces of a polarizing film, it is preferable to have an adhesive layer on one diffusion film. In the polarizing plate of this invention, when laminating | stacking a diffusion film on one side of a polarizing film, it is an adhesive layer on the other surface (on the film, when a protective film or an optical compensation film is laminated | stacked on the surface). It is preferable to have. As an adhesive used for such an adhesive layer, a conventionally well-known suitable adhesive can be used without a restriction | limiting especially, For example, an acrylic adhesive, a urethane type adhesive, a silicone type adhesive etc. are mentioned. Especially, an acrylic adhesive is used preferably from a viewpoint of transparency, adhesive force, reliability, rework property, etc. The pressure-sensitive adhesive layer may be provided by a method of making such pressure-sensitive adhesive, for example, an organic solvent solution, applying it to a base film (for example, a polarizing film, etc.) with a die coater, a gravure coater, or the like and drying it. It can also be provided by the method of transferring the sheet-like adhesive formed on the processed plastic film (called independent film) to a base film. Although there is no restriction | limiting in particular also about the thickness of an adhesive layer, Generally, it is preferable to exist in the range of 2-40 micrometers.

The optical functional film may be affixed on the surface in which the adhesive layer of the polarizing plate was formed through the said adhesive layer. As an optical functional film, For example, the liquid crystal compound is apply | coated to the surface of a base material, and the optical compensation film which is orientated; A reflection type polarizing film that transmits any kind of polarized light and reflects polarized light exhibiting its inverse properties; Retardation film made of polycarbonate resin; Retardation film which consists of cyclic polyolefin type resin, The film which has an anti-glare function which has an uneven shape on the surface; Films with surface antireflection; A reflective film having a reflective function on a surface thereof; And a semi-transmissive reflective film having both a reflection function and a transmission function. As a commercial item corresponded to the optical compensation film in which the liquid crystalline compound is apply | coated to the base material surface, and is oriented, "WV film" (Fuji Film Co., Ltd. product), "NH film" (New Nippon Sekiyu Co., Ltd. product), "NR film" (made by New Nippon Seki Oil Co., Ltd.), etc. are mentioned. As a commercial item which corresponds to the reflective polarizing film which permeate | transmits some kind of polarized light and reflects the polarized light which shows the opposite property, it is "DBEF" (3M company make, Sumitomo 3M Co., Ltd. in Japan), for example. And "APF" (produced by 3M, available from Sumitomo 3M Co., Ltd. in Japan). Moreover, as a commercial item corresponded to the retardation film which consists of cyclic polyolefin type resin, "Aton film" (made by JSR Corporation), "Esshina" (made by Sekisui Kagaku Kogyo Co., Ltd.), "Zeonor" Film "(manufactured by Optes Co., Ltd.) and the like.

The polarizing plate of this invention can be used suitably as a back side polarizing plate arrange | positioned between the liquid crystal cell with which a liquid crystal display device is equipped, and a backlight.

<Liquid crystal panel and liquid crystal display device>

The liquid crystal panel of this invention is equipped with a liquid crystal cell and the polarizing plate of the said invention, The diffuser film is laminated | stacked on one side of the polarizing film in a polarizing plate, and the surface on the opposite side to the surface on which the diffuser film is laminated | stacked in a polarizing film is laminated | stacked. Liquid crystal cells are stacked. A polarizing plate and a liquid crystal cell are normally bonded through the said adhesive layer. Such a liquid crystal panel of the present invention is usually applied to a liquid crystal display device such that its diffusion film is on the backlight side (so that the polarizing plate of the present invention is disposed between the liquid crystal cell and the backlight). In the liquid crystal panel of the present invention, a polarizing plate is also provided on the front side of the liquid crystal cell (a side of viewing when applied to the liquid crystal display device and opposite to the side on which the polarizing plate of the present invention is laminated). There is no restriction | limiting in particular about the polarizing plate provided in this, The conventionally well-known suitable polarizing plate can be used. For example, the polarizing plate etc. to which the anti-glare process, the hard-coating process, and the anti-reflective process were performed are mentioned. Moreover, the polarizing plate in which the polyethylene terephthalate film, the acryl film, and the polypropylene film were laminated | stacked on one side of a polarizing film may be sufficient.

The liquid crystal display device of this invention is equipped with the liquid crystal panel arrange | positioned so that a diffusion film may become a backlight side. Such a liquid crystal display device of the present invention includes a liquid crystal panel in which the polarizing plate of the present invention is laminated on the rear side of a liquid crystal cell, so that the luminance at the front of the screen is high, the image quality is excellent, and the mechanical strength is sufficient while corresponding to the thinning. Furthermore, by arrange | positioning the diffusing film of the polarizing plate of this invention on the back side of a liquid crystal panel, the adhesiveness of a liquid crystal panel and a backlight system can be prevented, and visibility is improved.

In the liquid crystal display device of the present invention, a configuration other than the above-mentioned liquid crystal panel can be adopted with a suitable configuration of a conventionally known liquid crystal display device. The structure provided in order, and the structure provided with the backlight, the light-diffusion plate, the light-diffusion sheet, and the liquid crystal panel of this invention in this order are mentioned. In the former case, the liquid crystal panel is arranged so that the diffusing film of the polarizing plate faces the light diffusing plate, and in the latter case, the liquid crystal panel is arranged so that the diffusing film of the polarizing plate faces the light diffusing sheet. In the liquid crystal display device of the present invention, since light diffusivity is imparted to the polarizing plate itself of the present invention used as the back side polarizing plate, it is possible to omit a part or all of the light diffusing sheet conventionally provided on the light diffusing plate. This makes it possible to reduce the weight and weight of the liquid crystal display device.

Although an Example is given to the following and this invention is demonstrated in more detail, this invention is not limited to these Examples. In addition, unless otherwise indicated,% and the part which show content-usage-amount are the basis of weight in an example.

In the following examples, the light intensity of the transmitted light of a diffusion film points out the value measured using the variable photometer GC5000L (made by Nippon Denshoku Kogyo Co., Ltd.). In addition, the haze of a diffusion film points out the value measured using the haze meter HM-150 type (made by Murakami Shiki-Shiki Genjushi Co., Ltd.) based on JISK7136.

(Production Example: Production of Polarizing Film)

After immersing a polyvinyl alcohol film having a thickness of about 2400 μm and a polyvinyl alcohol having a saponification degree of 99.9 mol% or more in a polyvinyl alcohol film of 30 ° C. in pure water at 30 ° C., an aqueous solution having a weight ratio of iodide / potassium iodide / water of 0.02 / 2/100 was used. It was immersed at 30 degreeC. Then, it was immersed at 56.5 degreeC in the aqueous solution whose weight ratio of potassium iodide / boric acid / water is 12/5/100. Subsequently, after wash | cleaning with the pure water of 8 degreeC, it dried at 65 degreeC and obtained the polarizing film in which iodine adsorption-orientated to the polyvinyl alcohol film. Stretching was mainly performed in the step of iodine dyeing and boric acid treatment, and the total draw ratio was 5.3 times.

<Example 1>

After melt-kneading a polycarbonate resin pellet with a diffusion agent made of polymethyl methacrylate-styrene resin particles, extrusion molding was carried out to obtain a diffusion film I having a thickness of 80 µm and a flat surface having a haze of 15%. Next, one side of the diffusion film I was subjected to corona treatment. Next, the diffusing film I is bonded to one surface of the polarizing film obtained in the above production example using a photocurable adhesive such that the corona treated surface is a bonding surface, and the triacetyl cellulose film ( 80 µm in thickness and manufactured by Konica Minolta Opto Co., Ltd. were bonded using the same photocurable adhesive, and the adhesive was cured by irradiation of ultraviolet rays to obtain a polarizing plate. The 25-micrometer-thick acrylic adhesive layer was provided in the outer surface of the triacetyl cellulose film of this polarizing plate.

The polarizing plate is bonded to the back of the liquid crystal cell through the pressure-sensitive adhesive layer, and a commercially available polarizing plate is bonded to the front of the liquid crystal cell to assemble the liquid crystal panel, and this is combined with a commercially available light diffuser plate and a backlight to form a liquid crystal display device. Produced. When the display of the liquid crystal display device was visually observed, a bright image was obtained when viewed from the front, and visibility was good.

<Example 2>

A polarizing plate for back side was obtained in the same manner as in Example 1 except that Diffusion Film II ("Lumisty LCZ-2070" manufactured by Sumitomo Chemical Industries, Ltd.) was used instead of Diffusion Film I, and Example 1 was used. In the same manner as in the above, a liquid crystal display device was manufactured. When the display of the liquid crystal display device was visually observed, a bright image was obtained when viewed from the front, and visibility was good.

Comparative Example 1

Same as Example 1 except for using diffusion film I having a thickness of 100 µm and a haze of 83% instead of diffusion film I (coating cured resin liquid containing silica particles on one side of polyethylene terephthalate film). The back side polarizing plate was obtained, and it carried out similarly to Example 1 using this, and produced the liquid crystal display device. When the display of the liquid crystal display device was visually observed, only a dark image was obtained from the front, and the visibility was poor.

Table 1 shows the light intensity of the transmitted light of the diffusion films I to III used in Examples 1 and 2 and Comparative Example 1. In addition, the light intensity A, the light intensity B, and the incident angle (alpha) in Table 1 were as above-mentioned, and the light intensity A in Table 1 is shown by the relative value when each light intensity B is set to one. In addition, "-" in Table 1 means that light diffusivity is not shown with respect to the light of the incidence angle (light intensity A and B are zero).

The embodiments and examples disclosed herein are to be considered in all respects as illustrative and not restrictive. The scope of the present invention is shown by above-described not description but claim, and it is intended that the meaning of a claim and equality and all the changes within a range are included.

According to the polarizing plate and liquid crystal panel of this invention, the brightness in the front of the screen of the liquid crystal display device to which it is applied can be made high, and it becomes possible to provide the liquid crystal display device excellent in image quality. Moreover, according to this invention, it becomes possible to aim at thickness reduction of a liquid crystal display device, and reduction of the number of members. Such a liquid crystal display device of the present invention can be suitably applied to a liquid crystal display device for a large screen liquid crystal television, particularly a liquid crystal display device for a wall-mounted liquid crystal television.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram for demonstrating the light diffusivity of the diffusing film used for the polarizing plate of this invention.

<Explanation of symbols for the main parts of the drawings>

100: diffusion film

101: normal of diffusion film

102: light incident at an angle inclined α ° from the normal direction of the diffusion film

103: straight line transmission direction

104: 10 ° normal direction from the straight line transmission direction

105: 10 degree diffused film direction direction from a straight line transmission direction

Claims (7)

A polarizing film made of a uniaxially stretched polyvinyl alcohol-based resin film in which iodine or dichroic dye is adsorbed and oriented, and a diffusing film having light diffusing property laminated on at least one side of the polarizing film, The diffusing film is a light intensity A in a direction of 10 ° normal from a linear transmission direction and 10 ° from a linear transmission direction in the transmitted light of light incident on the diffusion film at an angle inclined 40 ° to 60 ° from its normal direction. Polarizing plate whose ratio A / B of light intensity B of a direction is larger than 1. The diffused film according to claim 1, wherein the diffusing film has a light intensity A and a linear transmission in the direction of a 10 ° normal line from the linear transmission direction in the transmitted light of the light incident on the diffusion film at an angle inclined from 20 ° to 60 ° from its normal direction. The polarizing plate whose ratio A / B of the light intensity B of a 10 degree diffused film side direction is larger than 1 from a direction. The polarizing plate according to claim 1 or 2, wherein the diffusion film is laminated on one side of the polarizing film, and an optical compensation film or a protective film is laminated on the other side. The polarizing plate of any one of Claims 1-3 which is a back side polarizing plate arrange | positioned between the liquid crystal cell with which a liquid crystal display device is equipped, and a backlight. It is a liquid crystal panel provided with a liquid crystal cell and the polarizing plate of any one of Claims 1-4, The diffusion film is laminated on one side of the polarizing film in the polarizing plate, The liquid crystal panel in which the said liquid crystal cell is laminated | stacked on the surface on the opposite side to the surface where the said diffused film in the said polarizing film is laminated | stacked. It is a liquid crystal display device provided with the backlight, the light-diffusion plate, and the liquid crystal panel of Claim 5 in this order, The liquid crystal panel is a liquid crystal display device disposed so that the diffusion film of the polarizing plate is opposed to the light diffusion plate. It is a liquid crystal display device provided with the backlight, the light-diffusion plate, the light-diffusion sheet, and the liquid crystal panel of Claim 5 in this order, The liquid crystal panel is a liquid crystal display device disposed so that the diffusion film of the polarizing plate is opposed to the light diffusion sheet.

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