TW201726420A - Protecting film for polarizing plate - Google Patents

Abstract

The present invention provides a protecting film for polarizing plate. The film is capable of decreasing the damaging on the side surface opposite to the backlight unit of the polarizing plate, and suppressing the decrease in contrast at the same time. The present invention also provides a protecting film for polarizing plate that at least one surface of the protecting film has an arithmetic average roughness Ra of 0.04 [mu]m or higher, a ten-point average roughness Rz of 0.1 [mu]m or higher; the arithmetic average roughness Ra/average top and bottom interval Sm is 0.0007 or higher. The protecting film has a haze of 40% or lower. The surface is arranged to correspond with the backlight unit plate.

Description

Protective film for polarizing plate

The present invention relates to a protective film for a polarizing plate, and more particularly to a polarizing plate disposed on a backlight unit side of a liquid crystal cell (back side polarizing plate). membrane. Further, the polarizing plate having the protective film for a polarizing plate of the present invention is also used.

In the case of a polarizing plate used for various image display panels such as a liquid crystal display panel, a polarizing plate having a structure in which a dichroic dye such as iodine or a dichroic dye is adsorbed oriented is known. One or both sides of the polarizing film are laminated on the protective film such as a triacetyl cellulose film via an adhesive (for example, Patent Document 1). Such a polarizing plate is bonded to a liquid crystal cell in a form in which various optical layers such as a retardation film and an optical compensation film are further laminated as necessary, and constitutes a liquid crystal panel, and is incorporated in a liquid crystal display device together with a backlight unit.

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2010-211196

In recent years, liquid crystal display devices have been required to be thinner. Along with this thinning, it is also required that the interval between the liquid crystal panel and the backlight unit incorporated in the liquid crystal display device is smaller.

However, due to such a reduction in thickness, the polarizing plate (back side polarizing plate) attached to the backlight unit side of the liquid crystal panel is easily brought into contact with the backlight unit. When the polarizing plate is damaged by such contact, light incident from the backlight unit is scattered, and a part of the light is reduced in brightness when viewed from the front, and the damage is large and dense, and unevenness is observed due to the normal portion and the abnormal portion, and When black is displayed, there is a concern that light leakage, such as light leakage, causes problems in the image display function when viewed from an oblique direction.

In the invention described in the above Patent Document 1, a polarizing plate having a specific surface hardness and having a concave-convex structure on its surface is used, thereby suppressing damage. However, if the damage can be suppressed as in the invention described in the above Patent Document 1, and a high contrast image can be displayed, a higher quality polarizing plate can be provided.

In view of the above, it is an object of the present invention to provide a protective film for a polarizing plate which is capable of solving the above-described problem of a backlight unit side surface of a polarizing plate which is bonded to the back surface side of a liquid crystal cell, and which suppresses such a polarizing plate. Damage to the side surface of the backlight unit while suppressing a decrease in contrast.

The present invention provides the following preferred aspects [1] to [4].

[1] A protective film for a polarizing plate, which is calculated by at least one surface of the protective film The number average roughness Ra is 0.04 μm or more, the 10-point average roughness Rz is 0.1 μm or more, the arithmetic mean roughness Ra/the peak-to-valley average interval Sm is 0.0007 or more, and the haze of the protective film is 40% or less. This surface is disposed so that the backlight unit side of the back side polarizing plate faces the backlight unit.

[2] The protective film for a polarizing plate according to the above [1], wherein at least one surface has a Vickers Hardness HV of 15 to 35.

[3] A polarizing plate in which the protective film for a polarizing plate according to the above [1] or [2] is disposed at least on the side of the backlight unit.

[4] The polarizing plate according to [3] above, which is used for a liquid crystal display device having a long side of 800 mm or more.

According to the present invention, it is possible to provide a protective film for a polarizing plate which suppresses damage of the backlight unit side surface of the back side polarizing plate while suppressing a decrease in contrast.

1, 1', 2, 2' ‧ ‧ protective film

3, 3'‧‧‧ polarizing film

4, 4'‧‧‧ adhesive layer

5‧‧‧Liquid Crystal Unit

10, 10'‧‧‧ polarizing plate

100‧‧‧LCD panel

Fig. 1 is a cross-sectional view showing a configuration of a polarizing plate and a configuration of an aspect of a liquid crystal display panel.

Hereinafter, embodiments of the present invention will be described in detail.

The present invention relates to a protective film for a polarizing plate and a polarizing plate comprising the protective film for the polarizing plate, wherein an arithmetic mean roughness Ra of at least one surface of the protective film is 0.04 μm or more, and a 10-point average roughness Rz is 0.1 μm or more, the arithmetic mean roughness Ra/the peak-to-valley average interval Sm is 0.0007 or more, and the haze of the protective film is 40% or less, and the surface of the protective film is on the backlight unit side of the back side polarizing plate and the backlight unit. Relatively configured.

The arithmetic mean roughness Ra of at least one surface of the protective film of the present invention is 0.04 μm or more, preferably 0.06 μm or more, and more preferably 0.1 μm or more. When the arithmetic mean roughness Ra of at least one surface of the protective film is at least the above lower limit value, the damage of the surface of the protective film can be made inconspicuous by the uneven structure of the surface, and the image quality of the image display device can be prevented from being noticed. When the arithmetic mean roughness Ra of at least one surface of the protective film is less than 0.04 μm, damage and deterioration in image quality due to damage are easily observed. Further, the arithmetic mean roughness Ra is usually 2.0 μm or less. Here, the arithmetic mean roughness Ra is an index defined by the surface roughness defined in JIS B0601-1994. Accordingly, the arithmetic mean roughness Ra is large, that is, the surface roughness is large.

At least one surface of the protective film of the present invention has a 10-point average roughness Rz of 0.1 μm or more, preferably 0.2 μm or more, more preferably 0.3 μm or more. When the 10-point average roughness Rz of at least one surface of the protective film is at least the above lower limit value, the entire surface is not uniformly roughened, but the height of the unevenness is different, and the overall unevenness height is irregular. It can be made that the damage is not conspicuous, and the image quality of the image display device is not easily detected. If the 10-point average roughness Rz of at least one surface of the protective film is less than 0.1 μm, damage or deterioration in image quality due to damage may become easily noticeable. Further, the 10-point average roughness Rz is usually 8.0 μm or less. Here, the 10-point average roughness Rz is an index defined by the surface roughness specified in JIS B0601-1994, and is an average value of the absolute values of the elevations from the apex of the highest peak to the peak of the fifth highest peak. The value expressed as the sum of the average values of the absolute values of the elevations from the bottom of the lowest valley to the bottom of the fifth lowest valley.

The at least one surface of the protective film of the present invention has an arithmetic mean roughness Ra divided by a peak-to-valley average interval Sm, that is, Ra/Sm is 0.0007 or more, preferably 0.0011 or more, more preferably 0.0015 or more, and most preferably 0.009. Hereinafter, it is more preferably 0.005 or less. When Ra/Sm of at least one surface of the protective film is at least the above lower limit value, the light diffusibility of the protective film can be ensured, so that damage to the surface can be reduced even if the surface is damaged. When Ra/Sm of at least one surface of the protective film is at most the above upper limit value, the haze can be lowered. When the Ra/Sm of at least one surface of the protective film is less than 0.0007, the light diffusibility of the protective film is insufficient, and damage is easily recognized. Here, the average peak-to-valley interval Sm is a value defined by JIS B0601-1994, and Ra/Sm is a degree indicating the inclination of the unevenness.

Sm is usually from 10 μm to 200 μm.

The protective film of the present invention has a haze of 40% or less, preferably 35% or less, more preferably 20% or less, still more preferably 12% or less. When the haze of the protective film is at most the above upper limit value, the decrease in brightness can be suppressed, and the contrast becomes good. When the haze of the protective film is higher than 40%, the decrease in brightness is increased and the contrast is lowered. In order to reduce the haze, it is preferable to make Ra/Sm small, for example, if Ra is small and Sm is large. Further, the haze of the protective film of the present invention is usually 4% or more. Among them, the haze can be measured in accordance with JIS K7136. have The surface of the predetermined arithmetic mean roughness Ra, the 10-point average roughness Rz, the arithmetic mean roughness Ra, the peak-to-valley average interval Sm, and the haze, and the polarizing plate attached to the backlight unit side of the liquid crystal cell (back side polarization) In the board), it is preferable that it is a backlight unit side surface.

The Vickers hardness HV of at least one surface of the protective film of the present invention is preferably from 15 to 35, more preferably from 19 to 35, still more preferably from 19 to 30. When the Vickers hardness HV of at least one surface of the protective film is equal to or less than the upper limit value, when the surface is a soft surface, the damage of the backlight unit can be suppressed by the excessively protective film while Ra, Rz, Ra/Sm are Within the above range, the damage of the protective film can be made inconspicuous. Further, the protective film having the surface of the Vickers hardness HV in the above range can be produced without disposing a hard coat layer or the like, which is advantageous in terms of cost. Further, the Vickers hardness HV can be measured according to ISO 14577, and can be measured using an ultra-micro hardness tester (for example, an ultra-fine hardness tester HM2000 manufactured by FISCHER INSTRUMENTS), and is a value obtained by placing a load of 10 mN on the sample for 10 seconds. From the viewpoint of suppressing the damage of the polarizing plate and the backlight unit, it is preferable that the polarizing plate attached to the backlight unit side of the liquid crystal cell has the Vickers hardness HV on the side of the backlight unit side.

The protective film for a polarizing plate of the present invention usually contains a thermoplastic resin. The thermoplastic resin is not particularly limited. The preferred thermoplastic resin is excellent in transparency, thermal stability, moisture shielding property, isotropic property, and the like, and is, for example, a polyester-based polymer such as polyethylene terephthalate or polyethylene naphthalate; Cellulose polymers such as cellulose and triethyl fluorenyl cellulose; (meth)acrylic polymers such as polymethyl methacrylate; benzene such as polystyrene and acrylonitrile-styrene copolymer (AS) resin Vinyl polymer; polycarbonate Ester-based polymer; polyethylene, polypropylene, ring-based or polyolefin having a norbornene structure; polyolefin-based polymer such as ethylene-propylene copolymer; vinyl chloride-based polymer; nylon, aromatic polyamine, etc. Amine polymer; quinone imine polymer; fluorene polymer, polyether fluorene polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride A polymer such as a polymer, an ethylene butyral polymer, an aryl ester polymer, a polyoxymethylene polymer, an epoxy polymer, or a blend of the above polymers. The protective film may be formed of a cured layer made of a thermosetting type or an ultraviolet curing type resin such as an acrylic type, an amine ester type, an acrylamide type, an epoxy type or a polyoxymethylene type.

Among them, from the viewpoints of transparency, moisture shielding property, and isotropic property, a thermoplastic resin is preferably a (meth)acrylic polymer. Further, since the (meth)acrylic polymer is likely to cause damage, it is suitably used in the present invention. In addition, the (meth)acrylic polymer means a polymer mainly composed of (meth) acrylate, and may be a homopolymer of one type of (meth) acrylate, or may be (meth) Copolymer of acrylate with other (meth) acrylates and the like. Examples of the (meth) acrylate include alkyl (meth)acrylate such as methyl (meth)acrylate, ethyl (meth)acrylate, and butyl (meth)acrylate, and the carbon number of the alkyl group. Usually around 1 to 4.

Further, (meth)acrylic acid cycloalkyl esters such as cyclopentyl (meth)acrylate and cyclohexyl (meth)acrylate; (meth)acrylic acid aromatic esters such as phenyl (meth)acrylate; (cyclo)alkyl (meth)acrylate such as cyclohexylmethyl methacrylate; arylalkyl (meth)acrylate such as benzyl (meth)acrylate. Furthermore, the term "(meth)acrylic" means "acrylic acid" and/or "Methacrylate".

When the thermoplastic resin is a (meth)acrylic polymer, other polymers than the above (meth)acrylic polymer may be contained. The content of the other polymer is preferably from 0 to 70% by weight, more preferably from 0 to 50% by weight, still more preferably from 0 to 30% by weight, based on the total mass of the thermoplastic resin.

The thermoplastic resin may also contain particles. At this time, the refractive index difference Δn of the refractive index of the particles and the refractive index of the thermoplastic resin is preferably small. When the refractive index difference Δn is increased, the internal haze of the protective film tends to increase. Further, the particle diameter of the particles is preferably small. When the particle diameter of the particles is large, the internal haze tends to be large in the same manner. When the particles are contained, in order to make the haze within the range defined by the present invention, it is preferred to use particles having a small refractive index difference Δn and particles having a small particle diameter.

When the thermoplastic resin is a (meth)acrylic polymer, the (meth)acrylic polymer may contain rubber particles from the viewpoint of improving impact resistance and film forming properties of the protective film.

The rubber particles may be particles including a rubber elastomer layer exhibiting rubber elasticity, and may be, for example, a single-layer structure particle composed of a rubber elastic layer exhibiting rubber elasticity, or a rubber elastomer layer exhibiting rubber elasticity at the same time and the like. Multilayer construction of layers. Examples of the rubber elastomer layer include an olefin-based elastic polymer, a diene-based elastic polymer, a styrene-diene-based elastic copolymer, and an acrylic elastomer. Among them, from the viewpoint of light resistance and transparency, it is preferred to use an acrylic elastomer.

Acrylic elastomeric polymer, which can be alkyl acrylate The main body, that is, a polymer containing 50% by weight or more of a constituent unit derived from an alkyl acrylate based on the total monomer amount.

The acrylic elastomeric polymer may be a homopolymer of an alkyl acrylate, or a copolymer comprising 50% by weight or more of a constituent unit derived from an alkyl acrylate and 50% by weight or less of a constituent unit derived from another polymerizable monomer. .

As the alkyl acrylate constituting the acrylic elastomer, the number of carbon atoms of the alkyl group is usually 4 to 8, and when the other polymerizable monomer is exemplified, for example, methyl methacrylate or methacrylic acid An alkyl methacrylate; a styrenic monomer such as styrene or alkylstyrene; a monofunctional monomer such as an acrylonitrile or acrylonitrile unsaturated nitrile; and a (meth)acrylic acid Allyl ester, ethylenlate of (meth)acrylic acid, ethylenic ester of unsaturated carboxylic acid; diene ester of dibasic acid such as diallyl maleate; such as alkanediol di(methyl) a polyfunctional monomer such as an unsaturated carboxylic acid diester of an diol diol.

The rubber particles containing the acrylic elastomer as the rubber elastomer are preferably particles having a multilayer structure having an acrylic elastomer polymer layer. Specifically, a two-layer structure having an acrylic elastic polymer and a hard polymer layer mainly composed of an alkyl methacrylate on the outer side or the inner side of the acrylic elastic polymer layer, and further comprising the acrylic acid The inner side of the elastic polymer layer has a three-layer structure of a hard polymer layer mainly composed of an alkyl methacrylate.

The hard polymer layer formed on the outer side and/or the inner side of the acrylic elastic polymer layer is mainly composed of an alkyl methacrylate The example of the monomer composition of the polymer may be the same as the monomer composition of the polymer mainly composed of the alkyl methacrylate exemplified as the (meth)acrylic polymer, and particularly the methacrylic acid is used. The monomer composition in which the methyl ester is the main component is preferred. The acrylic rubber particles having such a multilayer structure can be produced by a method described in, for example, Japanese Patent Publication No. 55-27576.

The diameter (average particle diameter) of the outer side of the rubber elastic body (acrylic elastic polymer layer) contained in the rubber particles is preferably 10 nm or more, more preferably 30 nm or more, still more preferably 50 nm or more, and 350 nm or less. Preferably, it is more preferably 300 nm or less, and still more preferably 280 nm or less.

The diameter (average particle diameter) of the outer side of the rubber elastic rubber (acrylic elastic polymer layer) of the rubber particles was measured as follows. That is, when such a rubber particle is mixed with a (meth)acrylic polymer and thinned, when the cross section is dyed with an aqueous cerium oxide solution, when the cross section is colored with cerium oxide, only the rubber elastic layer is colored and observed as In the almost circular shape, the (meth)acrylic resin of the mother layer is not dyed. Therefore, from the section thus dyed, a sheet was prepared using a microtome or the like and observed with an electron microscope. Then, 100 dyed rubber particles were randomly taken out, and the particle diameter (diameter to the outer side of the rubber elastic layer) of each was calculated, and the average value was used as the average particle diameter. Since the measurement is carried out in such a manner, the above average particle diameter obtained is a number average particle diameter.

When the rubber particles are a hard polymer mainly composed of methyl methacrylate as the main layer and rubber particles of the rubber elastomer layer (acrylic elastomer layer) are wrapped therein, the rubber particles are mixed with the master batch. In the case of a (meth)acrylic polymer, the outermost layer of the rubber particles is mixed with the (meth)acrylic polymer of the master batch. Therefore, when the cross section was stained with cerium oxide and observed with an electron microscope, the observed rubber particles were particles in a state in which the outermost layer was excluded. Specifically, when the inner layer is an acrylic elastic polymer and the outer layer is a rubber particle having a two-layer structure of a hard polymer mainly composed of methyl methacrylate, the inner layer of the acrylic elastic polymer is observed. Partially dyed monolayer structured particles. Further, when the innermost layer is a hard polymer mainly composed of methyl methacrylate, the intermediate layer is an acrylic elastic polymer, and the outermost layer is a rubber having a three-layer structure of a hard polymer mainly composed of methyl methacrylate. In the case of particles, it is a particle having a two-layer structure in which the central portion of the particle in which the innermost layer is observed is not dyed, and only the acrylic elastic polymer portion of the intermediate layer is dyed.

When the (meth)acrylic polymer contains rubber particles, it is based on the total mass of the (meth)acrylic polymer constituting the protective film from the viewpoint of improving the impact resistance and film forming properties of the protective film. In the case of the rubber film, the content of the rubber particles in the protective film is preferably 3% by mass or more and 60% by mass or less, more preferably 45% by mass or less, and still more preferably 35% by mass or less. When the particle diameter and content of the rubber particles in the protective film are within the above range, the increase in haze can be suppressed. Further, in the present invention, as the rubber particles, when a particle having a multilayer structure of a layer exhibiting rubber elasticity and another layer is used, the quality of a portion of the rubber elastic layer and the inner layer thereof is shown. Set to the quality of the rubber particles. For example, when the rubber particles of the above three-layer structure are used, the acrylic elastic polymer portion of the intermediate layer and the innermost layer of methyl methacrylate are mainly used. The total weight of the hard polymer portion is taken as the mass of the rubber particles. When the acrylic rubber particles having the three-layer structure are dissolved in acetone, the acrylic elastic polymer portion of the intermediate layer and the hard polymer portion mainly composed of methyl methacrylate in the innermost layer remain as insoluble components. The ratio of the total value of the intermediate layer and the innermost layer to the acrylic rubber particles having a three-layer structure is easily obtained.

When the (meth)acrylic polymer contains rubber particles, the (meth)acrylic polymer composition containing the rubber particles used for the production of the film may be composed of (meth)acrylic polymer and rubber. The particles are obtained by melt-kneading and mixing, and may be obtained by first producing rubber particles and polymerizing a monomer composition as a raw material of the (meth)acrylic resin in the presence thereof.

The thermoplastic resin may contain, in addition to the above particles, usual additives such as an ultraviolet absorber, an antioxidant, an antistatic agent, a surfactant, and the like. As a UV absorber, for example three The ultraviolet absorber is exemplified by the trade name "Kemisorb102" manufactured by Chemipro Chemical Co., Ltd., the product name "Adekastab LA46" manufactured by ADEKA Co., Ltd., "Adekastab LAF70", and the trade name "TINUVIN 460" manufactured by BASF Corporation. "TINUVIN 405", "TINUVIN 400", "TINUVIN 477", trade name "CYASORB UV-1164" manufactured by SUN CHEMICAL Co., Ltd.; benzotriazole-based ultraviolet absorber, ADEKA Co., Ltd. The trade names "Adekastab LA31" and "Adekastab LA36", the product names "SUMISORB 200", "SUMISORB 250", "SUMISORB 300", "SUMISORB 340", and "SUMISORB 350" manufactured by CHEMITEX Co., Ltd., Chemipro Chemical Co., Ltd. The company's trade names are "Kemisorb74", "Kemisorb79", "Kemisorb279", and the trade names "TINUVIN 99-2", "TINUVIN 900", "TINUVIN 928" manufactured by BASF.

The absolute value of the plane orientation coefficient ΔP of the protective film may be 2.0 × 10 ^-4 or less. The plane orientation coefficient ΔP is a physical property value of an index of the molecular chain orientation state of the polymer constituting the film, and the refractive index of the in-plane retardation axis direction of the film (the direction in which the in-plane refractive index becomes maximum) is nx, in-plane. The refractive index in the direction of the advancing axis (the direction perpendicular to the in-plane retardation axis direction) is ny, and when the refractive index in the thickness direction of the film is nz, it is defined by the following equation: plane orientation coefficient ΔP = (nx + ny) / 2-nz.

The thickness of the protective film is not particularly limited and is usually 500 μm or less, preferably 10 to 300 μm, more preferably 20 to 200 μm, still more preferably 30 to 100 μm. Further, the protective film may be composed of a transparent protective film or the like having an optical compensation function.

The method for producing the protective film having the above-described predetermined arithmetic mean roughness Ra, 10-point average roughness Rz, arithmetic mean roughness Ra, peak-to-valley average interval Sm, and haze is not particularly limited, and may be, for example, embossed ( Embossing) way of manufacturing. In the embossing processing method, a thermoplastic resin particle or a particle containing the thermoplastic resin and the above-mentioned particles is sandwiched between a forming mold having a surface roughened surface and a forming mold having a smooth surface, and is subjected to pressure treatment under heating. Further, by thinning, a protective film having a desired arithmetic mean roughness Ra, a 10-point average roughness Rz, an arithmetic mean roughness Ra, and an average peak-to-valley interval Sm can be obtained. And borrow By using two sheets of roughened surface, it is also possible to obtain protective films of Ra, Rz, Ra/Sm which are desired for both masks. Here, the heating temperature is not particularly limited as long as it is equal to or higher than the melting temperature of the thermoplastic resin. Further, in the embossing processing method, the protective film of the present invention can be produced by melt-extruding a thermoplastic resin and sandwiching the extruded resin with a pair of rolls to form a film. One pair of rolls may be one of which is an embossing roll having irregularities on the surface, and the other roll may be an embossing roll or a mirror roll having a smooth surface, or may be a rubber elastic roll. In the embossing method, a film having a desired Ra, Rz, Sm, and haze can be obtained by appropriately selecting the surface shape of the embossing roll. Further, the film to which the unevenness is given in advance may be stretched. By extending, Ra/Sm can be made smaller. Moreover, Ra and Rz can also be made small.

The film of the surface roughening treatment and the unevenness of the embossing roll are transferred to the film to obtain the protective film of the present invention. The irregularities of the molding die and the embossing roll may be formed into shapes corresponding to Ra, Rz, and Sm of the intended protective film. The irregularities of the molding die and the embossing roll can be formed, for example, by a sandblasting method in which fine irregular particles are blown and fine irregularities are provided on the surface. For example, when the particle diameter is large, Ra becomes large, and when the number of particles per unit area is large, Sm becomes small. Further, when the hardness of the particles is high, Ra and Rz become large.

The protective film of the present invention may have a surface treatment layer without being attached to the surface of the protective film of the polarizing film, and may have, for example, an optical layer such as an antireflection layer, an antistatic layer, an antifouling layer or the like. Moreover, the protective film of the present invention may also have a hard coat layer, but it is preferred that it has no hard coat layer from the cost side. When a hard coat layer is used, in order to achieve a haze of 40% or less, the hard coat layer does not contain particles. Preferably.

The protective film for a polarizing plate of the present invention is disposed on the backlight unit side of the back side polarizing plate. Here, the backlight unit side of the back side polarizing plate refers to the side of the polarizing plate that faces the backlight unit in the liquid crystal display device when the back side polarizing plate is disposed on the liquid crystal display device. The backlight unit side of the back side polarizing plate is the side opposite to the identification side. The identification side refers to the side opposite to the liquid crystal cell in the both sides of the back side polarizing plate. Further, the protective film for a polarizing plate of the present invention is disposed on the outermost layer of the polarizing plate. The protective film for a polarizing plate of the present invention has the predetermined arithmetic mean roughness Ra, the 10-point average roughness Rz, the arithmetic mean roughness Ra, the average peak interval Sm, and the haze on at least one surface, from the suppression of damage and From the viewpoint of visibility, it is preferable that at least the backlight unit side surface of the back side polarizing plate has the predetermined arithmetic mean roughness Ra, the 10-point average roughness Rz, the arithmetic mean roughness Ra, the peak-to-valley average interval Sm, and Haze. The protective film for a polarizing plate of the present invention can be disposed on the side of the rear side polarizing plate, and is preferably disposed on the backlight side of the back side polarizing plate from the viewpoint of suppressing the decrease in contrast.

The polarizing plate (hereinafter also referred to as the polarizing plate of the present invention) of the protective film for a polarizing plate of the present invention is configured such that the protective film for a polarizing plate of the present invention is disposed at least on the backlight unit side of the back side polarizing plate, that is, Special restrictions. In an embodiment of the present invention, the polarizing plate of the present invention is composed of a protective film, a polarizing film, and an adhesive layer. The protective film for a polarizing plate of the present invention is disposed on the surface of the polarizing film so as to face the backlight unit in the liquid crystal display device. Polarizing plate of the present invention (especially the back side) The polarizing plate is disposed on one side of the liquid crystal cell via an adhesive layer, in particular, on the side of the backlight unit, and the present invention or other polarizing plate is also disposed on the other surface of the liquid crystal cell to constitute a liquid crystal display panel. . The liquid crystal display panel can be manufactured, for example, by assembling the liquid crystal display panel together with the backlight unit.

According to Fig. 1, a configuration of a polarizing plate having a protective film for a polarizing plate of the present invention and a liquid crystal display panel having the polarizing plate will be described. The polarizing plate (10) of the present invention is composed of the protective film (1), the polarizing film (3), the protective film (2), and the adhesive layer (4) of the present invention in this order. Further, usually, the polarizing film (3) and the protective film (1) or the protective film (2) are laminated via an adhesive. The protective film (2) may be the same as or different from the protective film (1).

The liquid crystal display panel (100), in one embodiment of the present invention, is a liquid crystal cell (5) and a polarizing plate (10) of the present invention and a polarizing film which are respectively bonded to the liquid crystal cell (5) via an adhesive layer (4). The plate (10') is composed of. In one embodiment of the present invention, the polarizing plate (10') is sequentially provided with a protective film (1'), a polarizing film (3'), a protective film (2'), and an adhesive layer in the same manner as the polarizing plate (10). (4') is composed. The configuration of the polarizing plate (10') may be the same as or different from that of the polarizing plate (10).

The polarizing film and the protective film are usually followed by an adhesive layer. The adhesive agent constituting the adhesive layer is not particularly limited, but from the viewpoint of thinning the adhesive layer, for example, a water-based one, that is, an adhesive component is dissolved in water, or an adhesive component is dispersed in water. . For example, an adhesive containing a polyvinyl alcohol-based resin or an amine ester resin as an adhesive component can be used. When the protective film is provided on both sides of the polarizing film, the adhesives to be used may be the same or different.

Containing a polyvinyl alcohol resin as an adhesive component In addition, the polyvinyl alcohol-based resin may be a partially modified saponified polyvinyl alcohol or a fully saponified polyvinyl alcohol, or may be a carboxyl-modified polyvinyl alcohol or an ethyl acetylated group-modified polyvinyl alcohol. A modified polyvinyl alcohol-based resin such as a methylol-modified polyvinyl alcohol or an amine-modified polyvinyl alcohol. Usually, an adhesive agent using a polyvinyl alcohol-based resin as an adhesive component is prepared as an aqueous solution of a polyvinyl alcohol-based resin. The concentration of the polyvinyl alcohol-based resin in the adhesive is usually from 1 to 10 parts by mass, preferably from 1 to 5 parts by mass, per 100 parts by mass of the water.

From the viewpoint of improving the adhesion, it is preferred to add a curable component such as glyoxal or a water-soluble epoxy resin and/or a crosslinking agent to the adhesive of the polyvinyl alcohol-based resin as the adhesive component. As the water-soluble epoxy resin, for example, a polyamidamine polyamine epoxy resin obtained by reacting epichlorohydrin with polyamidoamine such as diethylenetriamine and tri-extension can be suitably used. A polyalkyleneamine such as ethyltetramine is reacted with a dicarboxylic acid such as adipic acid. For example, "SUMIREZ RESIN 650" (manufactured by Sumitomo CHEMITEX Co., Ltd.) and "SUMIREZ RESIN 675" (manufactured by Sumitomo CHEMTEX Co., Ltd.), "" WS-525" (made by Japan PMC Co., Ltd.). The amount of the curable component and/or the crosslinking agent added (the total mass thereof when added) is usually from 1 to 100 parts by mass, preferably from 1 to 50, per 100 parts by mass of the polyvinyl alcohol-based resin. Parts by mass. When the amount of the curable component and/or the crosslinking agent added is within the above range, the adhesiveness can be improved, and an adhesive layer exhibiting good adhesion can be formed.

Moreover, the inclusion of an amine ester resin as an adhesive component It is preferred to use a mixture of a polyester-based ionic polymer type amine ester resin and a compound having a glycidoxy group. Here, the polyester-based ionic polymer-type amine ester resin refers to an amine ester resin having a polyester skeleton, and a small amount of an ionic component (hydrophilic component) is introduced into the skeleton. Such an ionic polymer type amine ester resin is suitable as a water-based adhesive because it is directly emulsified in water to form an emulsion without using an emulsifier. A polyester-based ionic polymer-type urethane resin is known per se, and an example of a polymer dispersant which disperses a phenol-based resin in an aqueous medium is described in Japanese Patent Laid-Open Publication No. Hei 7-97504, and Japanese Laid-Open Patent Publication No. 2005-208456 discloses a mixture of a polyester-based ionic polymer type amine ester resin and a compound having a glycidoxy group as a binder, and a cycloolefin resin film is attached. It is in the form of a polarizing film containing a polyvinyl alcohol-based resin.

The application of the protective film and/or the adhesive to be applied to the polarizing film of the protective film can be carried out by a known method, and for example, a casting method, a Meyer bar coating method, or a gravure coating method can be used. , comma coater method, doctor blade method, die coating method, dip coating method, spray method, and the like. The casting method refers to a method in which the film of the object to be coated is moved in an oblique direction about the vertical direction, about the horizontal direction, or between the vertical and the horizontal, and the adhesive is allowed to flow to the surface and spread. After the application of the adhesive, the protective film and the polarizing film bonded to the protective film were laminated, and the film was bonded by being sandwiched by a nip roll. For the bonding of the film using the nip roll, for example, a method of uniformly pressing and pressing with a roll or the like after applying the adhesive; after applying the adhesive, passing it between the roll and the roll, and performing a method of pressurizing and dispersing, and the like. In this In the case, the material of the roller to be used may be metal, rubber or the like. Moreover, when the film is dispersed by a plurality of rolls, the plurality of rolls may be of the same material or different materials.

Further, in order to improve the adhesion on the adhesion surface of the protective film and the polarizing film, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame treatment, or saponification treatment may be appropriately performed. The saponification treatment may, for example, be a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

After the above-mentioned bonding, drying is performed to harden the adhesive, whereby a polarizing plate can be obtained. The drying treatment is carried out, for example, by blowing hot air, and the temperature is usually in the range of 40 to 100 ° C, preferably 60 to 100 ° C. Moreover, the drying time is usually from 20 to 1200 seconds.

The thickness of the adhesive layer formed of the dried adhesive is usually 0.001 to 5 μm, preferably 0.01 to 2 μm, more preferably 0.01 to 1 μm. When the thickness of the subsequent layer is within the above range, sufficient adhesion can be ensured, and the appearance is also preferable.

After the drying, a sufficient bonding strength can be obtained by performing the aging at a temperature of at least room temperature for at least half a day, preferably several days or more. The ripening temperature is preferably in the range of 30 to 50 ° C, more preferably in the range of 35 to 45 ° C. When the ripening temperature is within the above range, the so-called "winding" which is wound into a reel shape is less likely to occur. Further, the humidity at the time of ripening is not particularly limited as long as the relative humidity is in the range of 0 to 70% RH. The ripening time is usually from 1 to 10 days, preferably from 2 to 7 days.

Further, as the above-mentioned adhesive, photohardening can also be used. Sexual adhesive. The photocurable adhesive agent may, for example, be a mixture of a photocurable epoxy resin, a photocationic polymerization initiator, a photocurable acrylic resin, and a photoradical polymerization initiator. When a photocurable adhesive is used, the photocurable adhesive is cured by irradiation with an active energy ray. The light source of the active energy ray is not particularly limited, and is preferably an active energy ray having a light-emitting distribution of a wavelength of 400 nm or less, specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, an ultra-high pressure mercury lamp, a fluorescent lamp, and a black light. A lamp, a microwave-excited mercury lamp, a metal halide lamp or the like is preferred.

The light irradiation intensity of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited, but is effective in the irradiation intensity of the wavelength region effective for activation of the polymerization initiator. It is preferably from 0.1 to 6000 mW/cm ² , more preferably from 10 to 1000 mW/cm ² , still more preferably from 20 to 500 mW/cm ² . When the irradiation intensity is within the above range, an appropriate reaction time can be secured, and yellowing of the resin and deterioration of the polarizing film due to heat radiated from the light source and heat generation at the time of curing of the photocurable adhesive can be suppressed. The time for irradiating the photocurable adhesive with light is not particularly limited as long as it is appropriately selected according to the cured photocurable adhesive, and the cumulative light amount indicating the product of the irradiation intensity and the irradiation time is preferably set to It is 10 to 10000 mJ/m ² , more preferably 50 to 1000 mJ/m ² , still more preferably 80 to 500 mJ/m ² . When the amount of accumulated light of the photocurable adhesive is within the above range, a sufficient amount of the active material derived from the polymerization initiator is generated, and the curing reaction can be performed more surely, and the irradiation time does not become too long and can be maintained well. Productive.

Furthermore, the light is hardened by irradiating the active energy ray When the adhesive is cured, the functions of the polarizing plate are hardened under various conditions such as the degree of polarization of the polarizing film, the transmittance, the hue, and the transparency of various films constituting the protective film. Preferably.

The polarizing film constituting the polarizing plate is a film having a function of taking out linear polarized light from incident natural light. For example, a polarizing film can be used as a polarizing film in which a polyvinyl alcohol-based resin film is adsorbed and oriented with a dichroic dye. As the polyvinyl alcohol-based resin constituting the polyvinyl alcohol-based resin film, a polyvinyl acetate-based resin can be used for saponification. As the polyvinyl acetate-based resin, in addition to the polyvinyl acetate of the homopolymer of vinyl acetate, for example, a copolymer of vinyl acetate and other monomers copolymerizable with vinyl acetate (for example, ethylene-vinyl acetate) may be mentioned. Ester copolymers, etc.). Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is usually from 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, and for example, an aldehyde-modified polyvinyl formal or a polyvinyl acetal, a polyvinyl butyral or the like may be used. The degree of polymerization of the polyvinyl alcohol-based resin is usually from 1,000 to 10,000, preferably from 1,500 to 5,000.

As a film formed of such a polyvinyl alcohol-based resin, a raw material film as a polarizing film can be used. The method for forming a film of a polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a conventionally known method. The film thickness of the raw material film composed of the polyvinyl alcohol-based resin is not particularly limited, but is, for example, 10 to 150 μm, preferably 15 to 100 μm, more preferably 20 to 80 μm, in view of easiness of stretching.

The polarizing film is usually produced by a step of stretching a polyvinyl alcohol-based resin film in one axis, and a step of adsorbing a polyvinyl alcohol-based resin film by a dichroic dye to adsorb a dichroic dye; a step of treating a polyvinyl alcohol-based resin film having a dichroic dye adsorbed with an aqueous solution of boric acid; and a water washing step after treatment with an aqueous solution of boric acid.

The one-axis extension of the polyvinyl alcohol-based resin film may be carried out before the dyeing of the dichroic dye, or simultaneously with the dyeing, or after the dyeing. When one-axis extension is performed after dyeing, the one-axis extension may be performed before boric acid treatment or boric acid treatment. One-axis extension can also be performed at a plurality of stages in the class. When the shaft is extended, one shaft extension may be performed between the rollers having different rotation speeds, or one roller extension may be performed using the heat roller. Further, the one-axis extension may be a dry stretching in which the film is stretched in the air, or may be a wet stretching in which the polyvinyl alcohol-based resin film is expanded by using a solvent. From the viewpoint of suppressing deformation of the polarizing film, the stretching ratio is preferably 8 times, more preferably 7.5 times, still more preferably 7 times or less. Further, the stretching ratio is usually 4.5 times or more from the viewpoint of the function as a polarizing film.

The method of dyeing the polyvinyl alcohol-based resin film with a dichroic dye is, for example, a method of immersing a polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, for example, iodine or a dichroic dye can be used. The dichroic dye includes, for example, a dichroic direct dye containing a disazo compound such as C.I. Direct Red 39; a dichroic direct dye containing trisazo, tetrazo compound or the like. Further, the polyvinyl alcohol-based resin film is subjected to immersion in water before the dyeing treatment. It is better.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide is usually used for dyeing. In the aqueous solution, the content of iodine 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 the dichroic dye, the temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C, and the time (dyeing time) of immersing in the aqueous solution is usually 20 to 1800 seconds.

When a dichroic dye is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing a water-soluble dichroic dye to perform dyeing is usually employed. In the aqueous solution, the content of the dichroic dye is usually from 1 × 10 ^-4 to 10 parts by weight, preferably from 1 × 10 ^-3 to 1 part by weight, more preferably 1 × 10 parts, per 100 parts by weight of water ^{. 3} to 1 × 10 ^-2 parts by weight. The aqueous solution may also contain an inorganic salt such as sodium sulfate as a dyeing auxiliary. When a dichroic dye is used as the dichroic dye, the temperature of the aqueous solution used for dyeing is usually from 20 to 80 °C. Moreover, the time (dyeing time) of immersion in the aqueous solution is usually from 10 to 1800 seconds.

The boric acid treatment after dyeing with the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous boric acid solution. The amount of the aqueous boric acid solution is usually from 2 to 15 parts by weight, preferably from 5 to 12 parts by weight, per 100 parts by weight of the water. When iodine is used as the dichroic dye, the aqueous boric acid solution preferably contains potassium iodide. The amount of potassium iodide in an aqueous boric acid solution is usually from 0.1 to 15 parts by weight per 100 parts by weight of water. It is preferably 5 to 12 parts by weight. The time of immersion in the aqueous boric acid solution is usually 60 to 1200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds. The temperature of the aqueous boric acid solution is usually 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. The temperature of the water to be washed is usually 5 to 40 ° C, and the immersion time is usually 1 to 120 seconds. After washing with water, drying treatment was carried out to obtain a polarizing film. The drying treatment can be carried out using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually from 30 to 100 ° C, preferably from 40 to 95 ° C, more preferably from 50 to 90 ° C. The drying treatment time is usually from 60 to 600 seconds, preferably from 120 to 600 seconds.

In such a polyvinyl alcohol-based resin film, a polarizing film can be obtained by performing one-axis stretching, dyeing with a dichroic dye, and boric acid treatment. The thickness of the polarizing film may be, for example, 5 to 40 μm.

The coating type film polarizing film has a small dimensional change ratio as compared with a conventional polarizing film formed by stretching a polyvinyl alcohol resin film. Therefore, by using the coating type film polarizing film, even if it is used for a long period of time and/or in a high temperature environment, the dimensional change of the polarizing plate can be suppressed, and the polarizing plate and the backlight unit accompanying the dimensional change of the polarizing plate can be further suppressed. s contact. As the coating type film polarizing film, for example, those described in JP-A-2012-58381, JP-A-2013-37115, International Publication No. 2012/147633, and International Publication No. 2014/091921 can be used.

Adhesive layer included in the polarizing plate of the present invention, laminated layer It is a polarizing film, or a surface treatment layer laminated on a protective film or laminated on a polarizing film or a protective film according to circumstances.

As the adhesive constituting the adhesive layer, a conventionally known adhesive can be used without particular limitation, and for example, it can be used: a matrix polymer such as an acrylic, a rubber, an amine ester, a polyoxyxene or a polyvinyl ether. Adhesive. Further, it may be an energy ray hardening type adhesive or a thermosetting type adhesive. Among these, an adhesive having an acrylic resin excellent in transparency, adhesion, reworkability, weather resistance, heat resistance, or the like as a matrix polymer is preferred.

The acrylic adhesive is not particularly limited, and can be suitably used: butyl (meth)acrylate, ethyl (meth)acrylate, isooctyl (meth)acrylate, 2-ethylhexyl (meth)acrylate A (meth) acrylate matrix polymer; a copolymerization matrix polymer comprising two or more of such (meth) acrylates. Further, in the matrix polymers, the polar single system is copolymerized. Examples of the polar monomer include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, and (meth)acrylic acid. A monomer having a carboxyl group, a hydroxyl group, a decylamino group, an amine group, an epoxy group or the like, such as 2-N,N-dimethylaminoethyl ester or glycidyl (meth)acrylate.

These acrylic adhesives can be used singly, but usually in combination with a crosslinking agent. The crosslinking agent may, for example, be a divalent or polyvalent metal ion and form a metal carboxylate with a carboxyl group; be a polyamine compound and form a guanamine bond with a carboxyl group; a compound, a polyalcohol, and an ester bond with a carboxyl group; a polyisocyanate compound, and a carboxy group The group forms a guanamine bond between the groups. Among them, polyisocyanate compounds are widely used.

The energy ray-curable adhesive refers to a property of being cured by irradiation with an energy ray such as an ultraviolet ray or an electron ray, and is also adhesive before being irradiated with an energy ray, and can be adhered to an adherend such as a film by energy. An adhesive that is hardened by irradiation of radiation and has a property of adjusting adhesion. As the energy ray-curable adhesive, it is particularly preferable to use an ultraviolet curable adhesive. The energy ray-curable adhesive generally contains an acrylic adhesive and an energy ray polymerizable compound as a main component. The crosslinking agent is usually further formulated, and a photopolymerization initiator, a photosensitizer, and the like may be formulated as needed.

The adhesive layer may include, for example, a natural substance, in addition to the matrix polymer and the crosslinking agent, in order to adjust the adhesive force, the aggregation force, the viscosity, the elastic modulus, the glass transition temperature, and the like of the adhesive as needed. Resin of the composition; additives such as tackifying resin, antioxidant, antistatic agent, ultraviolet absorber, dye, pigment, antifoaming agent, corrosive agent, photopolymerization initiator. Further, it may be an adhesive layer containing fine particles and exhibiting light scattering properties. The ultraviolet absorber is a salicylate-based compound, a diphenylketone-based compound, a benzotriazole-based compound, a cyanoacrylate-based compound, or a nickel-salted salt-based compound.

In the present invention, the adhesive constituting the adhesive layer is preferably a decane-based compound, and particularly preferably a decane-based compound is contained in the acrylic resin before the crosslinking agent is formulated. Since the decane-based compound can improve the adhesion to the glass, the inclusion of the decane-based compound can be improved. The adhesion between the liquid crystal cell of the glass substrate and the adhesive layer ensures high adhesion to the display panel.

The adhesive layer can be applied to a film (for example, a polarizing film or the like) to be laminated, and dried by, for example, using the above-mentioned adhesive as an organic solvent solution by a die coater, a gravure coater or the like. Method to set. Further, it may be provided by a method of transferring a sheet-like adhesive formed on a plastic film (also referred to as a release film) subjected to release treatment to a film or layer to be laminated. The thickness of the adhesive is not particularly limited, but is preferably in the range of 2 to 40 μm, more preferably in the range of 5 to 35 μm, and still more preferably in the range of 10 to 30 μm.

In a preferred aspect, the adhesive layer is an acrylic resin, a decane compound, and a copolymer of butyl acrylate, methyl acrylate, 2-phenoxyethyl acrylate, 2-hydroxyethyl acrylate, and acrylic acid. It is composed of an isocyanate compound of a crosslinking agent.

In the polarizing plate of the present invention, an optical layer such as a re-layered retardation film and a viewing angle compensation film may be used.

Examples of the retardation film include a birefringent film obtained by subjecting a polymer material to one-axis or two-axis stretching treatment, an alignment film of a liquid crystal polymer, and an oriented layer supporting a liquid crystal polymer by a film. The stretching treatment can be carried out, for example, by a roll stretching method, a long interval stretching method, a tenter stretching method, a tubular stretching method, or the like. The stretching ratio is generally 1.1 to 3 times when extending on one axis. The thickness of the retardation film is not particularly limited, but is generally 10 to 200 μm, preferably 20 to 100 μm.

Examples of the polymer material include polyvinyl alcohol. Polyvinyl butyral, polymethyl vinyl ether, polyhydroxyethyl acrylate, hydroxyethyl cellulose, hydroxypropyl cellulose, methyl cellulose, polycarbonate, polyarylate, polyfluorene, poly-p-phenylene Ethylene formate, polyethylene naphthalate, polyether oxime, polyphenylene sulfide, polyphenylene ether, polyallyl fluorene, polyvinyl alcohol, polyamine, polyimine, polyolefin, Polyolefin, polyvinyl chloride, cellulose-based polymer having a norbornene structure, or various binary, ternary, copolymers, graft copolymers, mixed products, and the like. These polymer materials may be oriented (stretched film) by stretching or the like.

The liquid crystal polymer is, for example, a main chain type or a side chain type polymer in which a conjugated linear atomic group (mesogen) which imparts liquid crystal orientation to a main chain or a side chain of a polymer is introduced. Specific examples of the main chain type liquid crystal polymer include a structure in which a liquid crystal cell group is bonded by a spacer which imparts flexibility, for example, a nematically oriented polyester liquid crystal polymer, a disk polymer, and cholesterol. Polymers, etc. Specific examples of the side chain type liquid crystal polymer include, for example, a polysiloxane, a polyacrylate, a polymethacrylate or a polymalonate as a main chain skeleton, and a conjugate as a side chain. The spacer of the atomic group includes a liquid crystal cell of a para-substitution-substituted cyclic compound unit. These liquid crystal polymers are, for example, those which are subjected to rubbing treatment on a surface of a film such as polyimide or polyvinyl alcohol formed on a glass plate, and an oxidized surface such as cerium oxide is obliquely vapor-deposited to develop a liquid crystal polymer. The solution is carried out by heat treatment.

The retardation film can be used for the purpose of, for example, compensating for coloring and viewing angles caused by birefringence of various wavelength plates and liquid crystal layers. If there is a phase difference, it is also possible to laminate two or more types of retardation films to adjust optical characteristics such as phase difference.

The viewing angle compensation film is a film for expanding the viewing angle of a clear image even when the screen of the liquid crystal display device is viewed in a direction oblique to the screen.

As such a viewing angle compensation film, for example, a retardation film, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer is supported on a transparent substrate. A polymer film having a birefringence extending in a plane direction through a plane is used for a conventional retardation film, and a retardation film used as a viewing angle compensation film is a birefringence film having birefringence in the plane direction. A polymer film; a biaxially stretched film such as a polymer having a birefringence in a plane direction and extending in a thickness direction and having a refractive index in a thickness direction, and a biaxially oriented film such as a tilt oriented film. As the oblique alignment film, for example, a heat shrink film is attached to the polymer film, and the polymer film is subjected to elongation treatment and/or shrinkage treatment under the action of shrinkage force due to heating; Tilt the director and so on. As the material raw material polymer of the retardation film, the same as the polymer of the retardation film described above can be used, and it is possible to prevent the coloration or the like due to the change in the viewing angle due to the phase difference of the liquid crystal cell, and to obtain a well-recognized viewing angle. For the purpose of expansion or the like, it is appropriately selected for use.

Further, from the viewpoint of achieving a wide viewing angle of good recognition, it is suitable to use an alignment layer of a liquid crystal polymer, and in particular, it is suitable to use an optically anisotropic layer containing an oblique alignment layer containing a discotic liquid crystal polymer. A viewing angle compensation film supported by a cellulose film.

The polarizing plate of the present invention can be, for example, by: a protective film It is produced by bonding an adhesive to a polarizing film and forming an adhesive on the surface of the protective film on the side where the liquid crystal cell is bonded. When the polarizing plate of the present invention further includes an optical layer, for example, various films constituting the optical layer are bonded to the protective film by an adhesive or an adhesive, and an adhesive layer is formed on the surface opposite to the surface adjacent to the protective film. Just fine. Thereby, a liquid crystal display panel including the liquid crystal cell and the polarizing plate of the present invention can be obtained.

Further, the polarizing plate of the present invention can be suitably used for a liquid crystal display panel having various screen sizes. When the screen size is larger, the size of each constituent member is also increased, so that the amount of deformation such as expansion and contraction becomes large, and as a result, it is easy to cause damage to the polarizing plate. Further, it has been found that in the image display panel having a rectangular aspect ratio of a rectangular aspect ratio of 9:16 or 9:21, it is particularly easy to cause damage to the backlight unit side surface of the back side backlight. The polarizing plate of the present invention can effectively suppress damage caused by contact with the backlight unit, and can effectively suppress the decrease in contrast, and can suppress damage of the polarizing plate even if the screen size is large. When the backlight unit of the liquid crystal display device has a long side of preferably 800 mm or more, more preferably 1000 mm or more, and usually 2000 mm or less, it is particularly advantageous to use a polarizing plate comprising the protective film of the present invention. For the screen size of the LCD panel, for example, the screen size is 5吋 (long side: 100 to 150mm), 10吋 (long side: 200 to 250mm), 17吋 (long side: 320 to 400mm), 32吋 ( Long side: 680 to 720mm), 40吋 (long side: 860 to 910mm), 46吋 (long side: 980 to 1030mm), 55吋 (long side: 1180 to 1230mm), 65吋 (long side: 1400 to 1450mm) ), 75吋 (long side: 1600 to 1700mm), 85吋 (long side: 1800 to 1900mm) liquid crystal display panel, especially beneficial Use a liquid crystal display panel with a screen size of 40 inches or more.

The liquid crystal display panel including the polarizing plate of the present invention preferably has a thickness of 5 mm or less, more preferably 3 mm or less, still more preferably 2 mm or less, more preferably 0.1 mm or more, still more preferably 0.2 mm or more, and still more Good for 0.3mm or more. When the thickness of the liquid crystal display panel is less than or equal to the above-described upper limit, the thickness of the liquid crystal display device including the liquid crystal display panel is reduced. When the thickness of the liquid crystal display panel is equal to or greater than the lower limit value, the liquid crystal display panel is less likely to be deformed. The contact between the liquid crystal cell constituting the liquid crystal display panel and the polarizing plate is suppressed, so that damage of the polarizing plate can be suppressed. Further, the thickness of the liquid crystal display panel is usually 0.01 mm or more.

In the liquid crystal display device including the polarizing plate of the present invention, since the backlight unit side surface of the polarizing plate is less likely to be damaged, the image display function is less likely to occur, and the reduction in contrast can be suppressed.

[Examples]

The following examples and comparative examples will be used to more specifically describe the present invention.

(Example 1)

70% by mass of the methacrylic resin and 30% by mass of the rubber particles were mixed by a super mixer, and melt-kneaded into pellets by a two-axis extruder. The particles were sandwiched between a SUS plate having a surface smoothed by sand blasting and an aluminum plate having a smooth surface so as to have an Ra of 0.05 μm, an Rz of 0.21 μm, and a Ra/Sm of 0.0015, and then sandwiched between the SUS plate and the aluminum plate having a smooth surface. The iron plate is subjected to pressure treatment in this state. For pressurization treatment, a pressurizing machine of 200 ° C is used (manufacturer: Shenteng Metal Industry Co., Ltd., model: NSF-100 type single-action compression forming) Machine), the clearance of the press machine is 1 cm. First, it was heated for 2 minutes as a preheating, and then held at a pressure of about 2 MPa for 1 minute. Then, the formed film was taken out from the presser while being sandwiched by an iron plate, and cooled on a cooling plate for 6 minutes to obtain a protective film (1). The thickness of the protective film (1) was 270 μm. Further, the haze measured according to JIS K7105 was 4.8%.

Further, as the methacrylic resin, a copolymer of methyl methacrylate/methyl acrylate = 96% / 4% (mass ratio) was used. Further, as the rubber particles, the innermost layer is composed of a hard polymer in which a methacrylic resin is polymerized using a small amount of allyl methacrylate; the intermediate layer contains butyl acrylate as a main component and styrene and a small amount of nails are used. a soft elastomer polymerized with allyl acrylate; the outermost layer is composed of an elastomeric particle of a three-layer structure of a hard polymer polymerized with a small amount of ethyl acrylate in a methacrylic resin, and an average of the elastomer to the intermediate layer The particle size is 240 nm. Further, in the rubber particles, the total mass of the innermost layer and the intermediate layer was 70% of the entire particle.

(Example 2)

The pellets were placed in a single-axis extruder having a diameter of 65 mm, and extruded through a T-die at a set temperature of 275 ° C, and the extruded resin was used to have Ra of 2.7 μm, Rz of 16 μm, and Ra/Sm of 0.015. The roughened embossing roll and the rubber-made elastic roll are sandwiched to obtain a protective film (2). The thickness of the protective film (2) was 80 μm. Further, the haze measured according to JIS K7105 was 21.4%.

(Example 3)

In addition to Ra as a roughened SUS plate, Ra is 0.06 μm, Rz A protective film (3) was obtained in the same manner as in Example 1 except that it was 0.29 μm and Ra/Sm was 0.0019. The thickness of the protective film (3) was 270 μm. Further, the haze measured according to JIS K7105 was 6.2%.

(Example 4)

A protective film (4) was obtained in the same manner as in Example 1 except that Ra was 0.28 μm, Rz was 1.51 μm, and Ra/Sm was 0.0042 as the roughened SUS plate. The thickness of the protective film (4) was 170 μm. Further, the haze measured according to JIS K7105 was 12.4%.

(Example 5)

A protective film (5) was obtained in the same manner as in Example 1 except that Ra was 0.37 μm, Rz was 1.91 μm, and Ra/Sm was 0.0047 as the roughened SUS plate. The thickness of the protective film (5) was 170 μm. Further, the haze measured according to JIS K7105 was 17.4%.

(Example 6)

A protective film (6) was obtained in the same manner as in Example 1 except that Ra was 1.01 μm, Rz was 4.33 μm, and Ra/Sm was 0.0083 as the roughened SUS plate. The thickness of the protective film (6) was 170 μm. Further, the haze measured according to JIS K7105 was 32.4%.

(Example 7)

A protective film (7) was obtained in the same manner as in Example 2 except that the set thickness was changed from 80 μm to 60 μm. The thickness of the protective film (7) was 60 μm. Further, the haze measured according to JIS K7105 was 34.1%.

(Comparative Example 1)

Except that the extruded resin was clamped with two mirrored rolls, The protective film (8) was obtained in the same manner as in Example 2. The thickness of the protective film (8) was 80 μm. Further, the haze measured according to JIS K7105 was 1.1%.

(Comparative Example 2)

A protective film (9) was obtained in the same manner as in Example 1 except that Ra was 0.03 μm, Rz was 0.14 μm, and Ra/Sm was 0.0003 as the roughened SUS plate. The thickness of the protective film (9) was 270 μm. Further, the haze measured according to JIS K7105 was 2.3%.

(Comparative Example 3)

A protective film (10) was obtained in the same manner as in Example 1 except that Ra was 0.04 μm, Rz was 0.19 μm, and Ra/Sm was 0.0009 as the roughened SUS plate. The thickness of the protective film (10) was 270 μm. Further, the haze measured according to JIS K7105 was 4.3%.

(Comparative Example 4)

A protective film (11) was obtained in the same manner as in Example 1 except that Ra was 1.38 μm, Rz was 5.90 μm, and Ra/Sm was 0.01 as a roughened SUS plate. The thickness of the protective film (11) was 170 μm. Further, the haze measured according to JIS K7105 was 41.8%.

(Comparative Example 5)

A protective film (12) was obtained in the same manner as in Example 1 except that Ra was 0.65 μm, Rz was 3.42 μm, and Ra/Sm was 0.0091 as the roughened SUS plate. The thickness of the protective film (12) was 170 μm. Further, the haze measured according to JIS K7105 was 50.6%.

Then, with respect to the protective films (1) to (12) obtained in the above examples and comparative examples, the total light transmittance, haze, and the like were measured in the following manner. The arithmetic mean roughness Ra, the 10-point average roughness Rz, the peak-to-valley average interval Sm, and the Vickers hardness HV were evaluated for the damage difficulty and the comparison. The results are shown in Table 1.

(Measurement of total light transmittance and haze)

According to JIS K7361, the total light transmittance of the protective films (1) to (12) was measured using the Murakami Color Technology Research Institute's limited haze meter HM-150. Further, according to JIS K7361, the haze of the protective films (1) to (12) was measured using a haze meter HM-150 with a limited amount of the Murakami Color Technology Research Institute.

(Measurement of arithmetic mean roughness Ra, 10-point average roughness Rz, and peak-to-valley average interval Sm)

According to JIS B0601-1994, the arithmetic mean roughness Ra of the protective films (1) to (12), the average roughness Rz of 10 points, and the surface roughness measuring machine HANDYSURF E-35A (Tokyo Precision Co., Ltd.) were used. The peaks and valleys are spaced at an average interval of Sm.

(Measurement of Vickers hardness HV)

The measurement was carried out according to ISO 14577 using an ultra-fine hardness tester HM2000 manufactured by FISCHER INSTRUMENTS, and the value of the load of 10 mN on the protective films (1) to (12) for 10 seconds, respectively, was Vickers hardness HV.

(Evaluation of damage difficulty)

According to K5600-5-4, the No. 553-M1 electric pencil scratch hardness tester manufactured by Yasuda Seiki Co., Ltd. was used for measurement. First, the protective films (1) to (12) were each attached to a glass plate with a tape, and the pencil was set to be 45 degrees, and a load of 500 g was applied to scratch the surface of the sample. Use phase A pencil of the same hardness was tested 5 times. Moreover, the hardness of the pencil was changed from 3H to 5B, and the same scratch test was performed.

The film scratched by the surface was placed on a blackboard, and the surface of the film was observed to be damaged by a fluorescent lamp. The pencil hardness of the film was taken as the maximum pencil hardness which occurred without damage at all times. When a pencil of 3H to 5B was used, damage was observed on the film, and it was evaluated as "6B" or less. Here, the pencil hardness is preferably 5B or more from the viewpoint of the ease of surface damage.

(comparative assessment)

A spectroradiometer (manufactured by Topcon Techno House Co., Ltd., SR-UL1) was placed at a distance of 1 m from the measurement surface of a liquid crystal display device (BRAVIA KDL-32EX550, manufactured by SONY Co., Ltd.) at a measurement angle of 2°. In the state, a digital video signal generator (manufactured by ASTRODESIGN Co., Ltd.) was connected, and the black luminance and white luminance of the black display/white display television were measured.

The measurement was performed five times after 40 minutes of black display, and the average value was black brightness. Then, after 5 minutes of white display, the measurement was performed 5 times, and the average value was white brightness. The value is divided by the white luminance divided by the black luminance value (7326), and the value is set as the reference value.

After the reference value is measured, the liquid crystal display device is decomposed, and the protective films (1) to (12) are placed on the polarizing plates on the side opposite to the backlight unit, and the liquid crystal display device is assembled again. Then, the black luminance and the white luminance were measured under the same conditions as when the reference value was measured, and the comparison was calculated. Based on the calculated comparison and the reference value, the contrast reduction rate was calculated according to the following equation.

Contrast reduction rate (%) = {(reference value - contrast) / reference value} × 100

Further, it is preferable here that the contrast reduction rate is 20% or less.

In the protective films (1) to (7) obtained in Examples 1 to 7, it is understood that the haze, Ra, Rz, and Ra/Sm are in a predetermined range. In this case, the obtained protective film has a pencil hardness of 5 B or more. When the contrast reduction rate is 20% or less, the surface damage is suppressed, and at the same time, the decrease in contrast is suppressed. On the other hand, it was found that the protective films (8) to (10) obtained in Comparative Examples 1 to 3 had low pencil hardness, and the damage of the surface could not be sufficiently suppressed. Further, the protective films (11) and (12) obtained in Comparative Examples 4 and 5 had a high contrast reduction rate. Therefore, it has been found that the protective films (8) to (12) cannot solve the problems of the present invention.

(Reference example)

A protective film (6) is disposed on the recognition-side polarizing plate of the liquid crystal display device to be disassembled, and the liquid crystal display device is assembled again in a state where the polarizing plate on the side opposite to the backlight unit side is originally. Then, black luminance and white luminance were measured under the same conditions as in the measurement standard, and the contrast was calculated. Based on the calculated comparison and the reference value, the contrast reduction rate was calculated. The result was 5660 and the contrast reduction was 23%.

1, 1', 2, 2' ‧ ‧ protective film

3, 3'‧‧‧ polarizing film

4, 4'‧‧‧ adhesive layer

5‧‧‧Liquid Crystal Unit

10, 10'‧‧‧ polarizing plate

100‧‧‧LCD panel

Claims (6)

A protective film for a polarizing plate having an arithmetic mean roughness Ra of at least one surface of the protective film of 0.04 μm or more, a 10-point average roughness Rz of 0.1 μm or more, and an arithmetic mean roughness Ra/average interval Sm of 0.0007 or more. The protective film has a haze of 40% or less, and the surface is disposed so that the backlight unit side of the back side polarizing plate faces the backlight unit. The protective film for a polarizing plate according to claim 1, wherein the Vickers hardness HV of at least one surface is 15 to 35. A polarizing plate in which a protective film for a polarizing plate according to claim 1 or 2 is disposed at least on a side of a backlight unit. The polarizing plate described in claim 3 is used for a liquid crystal display device having a long side of 800 mm or more. A liquid crystal display panel comprising: the polarizing plate and the liquid crystal cell according to claim 3 of the patent application. A liquid crystal display device comprising: the liquid crystal display panel and the backlight unit of claim 5;