JP2007256475A - Polarizing plate for liquid crystal display, and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate for liquid crystal display which is free of a vision defect due to light leak, color unevenness, coloration, etc., nearby a frame edge of a display screen, and a liquid crystal display device. <P>SOLUTION: A protection film on a side of a liquid crystal cell which has a structure of a thermoplastic acrylic resin layer, a resin composition layer, and a thermoplastic acrylic resin layer and has elastic body particles maldistributed in the thickness-directional center of the film and is of ≤100 μm in average thickness is formed by obtaining a resin composition by dispersing the elastic body particles of ≤2.0 μm in number-average particle size in thermoplastic acrylic resin and coextrusion molding the thermoplastic acrylic resin and resin composition. The polarizing plate for liquid crystal display is obtained by laminating the protection film on the side of the liquid crystal cell and another protection film one over the other across a polarizer. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a polarizing plate for liquid crystal display and a liquid crystal display device. More specifically, the present invention relates to a polarizing plate for liquid crystal display and a display device that are free from light leakage near the frame of the display screen, have poor visibility due to color shift, and have excellent viewing angle characteristics and flexibility. In particular, the polarizing plate of the present invention is suitable for a liquid crystal display device operating in the IPS mode.

  Conventionally, a cellulose triacetate film has been used as a film for protecting a polarizing film used in a liquid crystal display device such as a display such as a computer, a flat-screen TV, a clock, and a calculator. However, although good optical properties can be obtained in a normal use environment, stress is applied to the cellulose triacetate film, which is a protective film, due to the dimensional change of the polarizing film under high temperature and high humidity, resulting in an undesirable retardation. Will develop. Cellulose triacetate film is characterized by relatively small optical anisotropy in the in-plane direction of the film, but exhibits an undesired phase difference due to expansion and contraction of the protective film itself at high temperatures and high humidity. As a result, the phenomenon that the contrast and color of the liquid crystal display device change may occur, or the polarizing film may be deteriorated due to moisture absorption. In addition, since the cellulose triacetate film has a phase difference that cannot be ignored in the thickness direction of the film, the viewing angle characteristics are low, which may cause a frame failure.

  On the other hand, Patent Document 1 discloses an acrylic resin obtained by polymerizing 50 to 70 parts by weight of methyl methacrylate, 10 to 20 parts by weight of maleic anhydride and 20 to 35 parts by weight of styrene, and an impact-resistant acrylic rubber-methyl methacrylate graft. A polarizing film protective film comprising a composition containing a toughness improver composed of a copolymer, butyl-modified acetylcellulose, or the like in a mass ratio of 60 to 90/40 to 10 has been proposed.

Patent Document 2 discloses an acrylic resin film containing 60 to 90% by mass of an acrylic resin containing glutaric anhydride units and 7 to 40% by mass of acrylic elastic particles, and is an average of acrylic elastic particles. An acrylic resin film having a particle size of 70 to 300 nm, a breaking elongation of the film of 15% or more, a 1% deformation temperature under high tension of 100 ° C. or more has been proposed. However, these protective films have poor scratch resistance and cause scratches due to friction with the roll during molding, or entrain the chips generated during the cutting process, and the chips damage the film surface. There was a cause. In addition, these protective films have poor smoothness, transparency is impaired by interfacial scattering, and the polarization performance may be deteriorated by a change in optical path length.
Japanese Patent Laid-Open No. 5-119217 JP 2005-314534 A

  An object of the present invention is to provide a polarizing plate for liquid crystal display and a liquid crystal display device that are free from light leakage near the frame of the display screen, have poor visibility due to color shift, and have excellent viewing angle characteristics and flexibility. is there.

  As a result of studies to achieve the above-mentioned object, the present inventor has a thermoplastic acrylic resin as a main component, and elastic particles having a number average particle diameter of 2.0 μm or less are unevenly distributed in the central portion in the film thickness direction. In addition, a film having an average thickness of less than 100 μm is flexible, excellent in flexibility, and excellent in scratch resistance. When the film is used to protect the liquid crystal cell side of the polarizer, the film is formed near the frame of the display screen. It has been found that a polarizing plate for liquid crystal display and a liquid crystal display device can be provided that are free from visual inconvenience due to light leakage, color shift, etc., and have excellent viewing angle characteristics and flexibility. The present invention has been completed as a result of further studies based on this finding.

That is, the present invention
(1) Liquid crystal comprising a thermoplastic acrylic resin as a main component, elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the film thickness direction, and the average thickness is less than 100 μm Cell side protective film,
A polarizing plate for liquid crystal display, comprising another protective film and a polarizer disposed between the protective films.
(2) The average thickness obtained by laminating a layer composed of a thermoplastic acrylic resin and elastic particles having a number average particle diameter of 2.0 μm or less and a layer composed of a thermoplastic acrylic resin on both sides of the layer A liquid crystal cell-side protective film that is less than 100 μm,
A polarizing plate for liquid crystal display, comprising another protective film and a polarizer disposed between the protective films.
(3) The polarizing plate according to (1) or (2), wherein the liquid crystal cell-side protective film has a haze of 2% or less.
(4) The polarizing plate according to any one of (1) to (3), wherein the liquid crystal cell-side protective film has a retardation Rth in the thickness direction in the range of −3 nm to +3 nm in the wavelength range of 450 to 700 nm.
(5) The polarizing plate according to any one of (1) to (4), wherein the liquid crystal cell-side protective film has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less. .
(6) The polarizing plate according to any one of (1) to (5), wherein the liquid crystal cell-side protective film is obtained by coextrusion molding.
(7) The polarizing plate according to (6), wherein the liquid crystal cell-side protective film has a depth of linear recesses on the film surface or a height of linear protrusions of 50 nm or less and a width of 500 nm or more.
(8) The polarizing plate according to any one of (1) to (7), wherein the other protective film is a viewing side or a light source so that the liquid crystal cell side protective film of the polarizing plate faces the liquid crystal cell side. A liquid crystal display device provided to face the side.
It is.

  The polarizing plate for liquid crystal display of the present invention can provide a liquid crystal display device that is flexible and excellent in flexibility, has no visual defect due to light leakage near the frame of the display screen, color shift, etc., and has excellent viewing angle characteristics. Furthermore, since the surface hardness is high, it has excellent scratch resistance. In particular, the polarizing plate of the present invention is suitable for a liquid crystal display device operating in the IPS mode.

The polarizing plate for liquid crystal display of the present invention comprises a thermoplastic acrylic resin as a main component, elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the film thickness direction, and have an average thickness. A polarizing plate comprising a liquid crystal cell side protective film having a thickness of less than 100 μm, another protective film, and a polarizer disposed between them.
Further, the polarizing plate for liquid crystal display according to another aspect of the present invention comprises a layer comprising a thermoplastic acrylic resin and elastic particles having a number average particle size of 2.0 μm or less, and a thermoplastic acrylic resin on both sides of the layer. The layer is a polarizing plate comprising a liquid crystal cell-side protective film having an average thickness of less than 100 μm, another protective film, and a polarizer disposed between them.

[LCD cell side protective film]
The liquid crystal cell side protective film used in the polarizing plate of the present invention comprises a thermoplastic acrylic resin as a main component, and elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the film thickness direction. And an average thickness of less than 100 μm.

<Thermoplastic acrylic resin>
The thermoplastic acrylic resin, which is the main component of the protective film on the liquid crystal cell side, includes homopolymers of alkyl (meth) acrylates such as methyl acrylate, ethyl acrylate, methyl methacrylate, and ethyl methacrylate; hydrogens of alkyl groups A homopolymer of (meth) acrylic acid alkyl ester substituted with a functional group such as OH group, COOH group or NH ₂ group; or (meth) acrylic acid alkyl ester and styrene, vinyl acetate, α, β-mono Examples thereof include a copolymer with a vinyl monomer having an unsaturated bond such as ethylenically unsaturated carboxylic acid, vinyl toluene, and α-methylstyrene. As a thermoplastic acrylic resin, only 1 type may be used among these and it may use it in combination of 2 or more type. More preferably, the thermoplastic acrylic resin contains methyl methacrylate and butyl methacrylate as monomer units. The thermoplastic acrylic resin preferably has a glass transition temperature Tg in the range of 80 to 120 ° C.
Furthermore, the thermoplastic acrylic resin used in the present invention has a high surface hardness when formed into a film, specifically, pencil hardness (in accordance with JIS K5600-5-4 except that the test load is 500 g). ) Exceeding 2H is preferred.

  The thermoplastic acrylic resin constituting the protective film on the liquid crystal cell side includes colorants such as pigments and dyes, fluorescent brighteners, dispersants, thermal stabilizers, light stabilizers, infrared absorbers, ultraviolet absorbers, and antistatic agents. , Antioxidants, lubricants, solvents and the like can be used as appropriate. In addition, it is preferable that these compounding agents are unevenly distributed in the center part of the thickness direction of a film like the elastic body particle mentioned later. For example, a layer made of a thermoplastic acrylic resin containing an infrared absorber and / or an ultraviolet absorber and a layer made of a thermoplastic acrylic resin not containing an infrared absorber and / or an ultraviolet absorber sandwiching this layer are laminated. A liquid crystal cell-side protective film thus formed is a preferred embodiment.

The ultraviolet absorber can absorb ultraviolet rays and improve the durability of the film.
As the ultraviolet absorber, known ones such as a benzophenone ultraviolet absorber, a benzotriazole ultraviolet absorber, and an acrylonitrile ultraviolet absorber can be used. Among them, 2,2'-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol), 2- (2'-hydroxy-3 '-Tert-butyl-5'-methylphenyl) -5-chlorobenzotriazole, 2,4-di-tert-butyl-6- (5-chlorobenzotriazol-2-yl) phenol, 2,2'-dihydroxy- 4,4′-dimethoxybenzophenone, 2,2 ′, 4,4′-tetrahydroxybenzophenone and the like are preferably used. Among these, 2,2′-methylenebis (4- (1,1,3,3-tetramethylbutyl) -6- (2H-benzotriazol-2-yl) phenol) is particularly preferable. The concentration of the ultraviolet absorber can be selected within a range where the light transmittance at a wavelength of 370 nm or less is preferably 10% or less, more preferably 5% or less, and even more preferably 2% or less. Examples of the method of containing the ultraviolet absorber include a method of previously blending the ultraviolet absorber into the thermoplastic acrylic resin; a method of supplying it directly at the time of melt extrusion molding, and any method may be employed.

  It is preferable that the ultraviolet absorber is unevenly distributed in the center in the thickness direction of the film. When the liquid crystal cell-side protective film is composed of a laminate, the ultraviolet absorber concentration contained in the thermoplastic acrylic resin layer containing elastic particles is contained in the thermoplastic acrylic resin layer not containing elastic particles. The concentration should be higher than the UV absorber concentration. Specifically, the concentration of the ultraviolet absorber in the thermoplastic acrylic resin layer not containing elastic particles is preferably 0 to 1.0% by mass, more preferably 0 to 0.5% by mass. The concentration of the ultraviolet absorber in the thermoplastic acrylic resin layer containing the body particles is preferably 0.5 to 10% by mass, more preferably 1.0 to 5.0% by mass. When the content of the ultraviolet absorber is within the above range, it is possible to efficiently block ultraviolet rays without deteriorating the color tone of the polarizing plate, and to prevent a decrease in the degree of polarization during long-term use. If the content of the ultraviolet absorber in the thermoplastic acrylic resin layer containing the elastic particles is too small, the light transmittance at a wavelength of 370 nm or less increases, and the polarization degree of the polarizer decreases when used as a polarizing plate protective film. Become a trend. On the other hand, when the content of the ultraviolet absorber is too large, the light transmittance on the short wavelength side becomes small, and the laminate tends to be yellowish.

  Infrared absorbers include nitroso compounds, metal complexes thereof, cyanine compounds, squarylium compounds, thiol nickel complex compounds, phthalocyanine compounds, naphthalocyanine compounds, triallylmethane compounds, imonium compounds, diimonium compounds, Infrared absorption of naphthoquinone compounds, anthraquinone compounds, amino compounds, aminium salt compounds, carbon black, indium tin oxide, antimony tin oxide, metal oxides belonging to Group 4A, 5A or 6A, carbides, borides, etc. An agent etc. can be mentioned. These infrared absorbers are preferably selected so that the entire infrared ray (about 800 nm to 1100 nm) can be absorbed, and two or more kinds thereof may be used in combination. The amount of the infrared absorber can be appropriately adjusted so that, for example, the transmittance at a wavelength of 800 nm or more is 10% or less.

<Elastic particles>
The elastic particles used in the present invention are particles made of a rubber-like elastic body. Examples of the rubber-like elastic body include an acrylate-based rubber-like polymer, a rubber-like polymer containing butadiene as a main component, and an ethylene-vinyl acetate copolymer. Examples of the acrylic ester rubbery polymer include those containing butyl acrylate, 2-ethylhexyl acrylate, or the like as a main component. Of these, acrylate polymers based on butyl acrylate and rubbery polymers based on butadiene are preferred. The elastic particles may be formed by laminating two kinds of polymers. Typical examples thereof include an alkyl acrylate such as butyl acrylate, a styrene grafted rubber elastic component, and a methyl methacrylate. Examples thereof include elastic particles in which a hard resin layer made of a copolymer of a rate and / or methyl methacrylate and an alkyl acrylate forms a layer with a core-shell structure.

  The elastic particles used in the present invention have a number average particle diameter of 2.0 μm or less, preferably 0.1 to 1.0 μm, more preferably 0.1 to 0.5 μm, in a state dispersed in a thermoplastic acrylic resin. It is. Even if the primary particle size of the elastic particles is small, if the secondary particles formed by agglomeration or the like are large, the protective film has a high haze (cloudiness) and a low light transmittance. It is no longer suitable for use. Moreover, when the number average particle size becomes too small, the flexibility tends to decrease.

  In the present invention, the refractive index na (λ) of the elastic particles at a wavelength of 380 nm to 780 nm is between | na (λ) −nb () and the refractive index nb (λ) of the thermoplastic acrylic resin at a wavelength of 380 nm to 780 nm. λ) | ≦ 0.05 is preferably satisfied. In particular, a relationship of | na (λ) −nb (λ) | ≦ 0.045 is more preferable. Note that na (λ) and nb (λ) are average values of the main refractive indexes at the wavelength λ. When the value of | na (λ) −nb (λ) | exceeds the above value, the transparency of the liquid crystal cell-side protective film may be impaired due to interface reflection caused by a difference in refractive index at the interface.

  The elastic particles are unevenly distributed in the central portion in the thickness direction of a film mainly composed of a thermoplastic acrylic resin. In other words, there are few elastic particles near the surface of the film, and many elastic particles are distributed in the center in the thickness direction of the film. The distribution of the elastic particles in the film thickness direction may gradually increase from the surface toward the center or may increase on the stairs.

  As an aspect that increases stepwise, a layer composed of a thermoplastic acrylic resin and elastic particles having a number average particle diameter of 2.0 μm or less and a layer composed of a thermoplastic acrylic resin on both sides of the layer are laminated. A film having an average thickness of less than 100 μm. This laminated film is obtained by forming a base film by molding a composition comprising a thermoplastic acrylic resin and elastic particles having a number average particle size of 2.0 μm or less, and does not contain elastic particles on both sides of the base film. By applying a thermoplastic acrylic resin; or by bonding a film formed by molding a thermoplastic acrylic resin not containing elastic particles on both sides of the base film, or a number average with the thermoplastic acrylic resin It can be obtained by coextrusion molding a composition comprising elastic particles having a particle size of 2.0 μm or less and a thermoplastic acrylic resin not containing elastic particles. In the present invention, those obtained by coextrusion molding are preferred.

  Thus, the elastic particles are unevenly distributed in the central portion in the thickness direction, so that the central portion in the thickness direction of the liquid crystal cell-side protective film becomes a flexible layer, and both surfaces of the liquid crystal cell-side protective film become hard layers. By setting it as such a structure, the flexibility of the said protective film can be improved, ensuring sufficient hardness of the surface of the said protective film, and thereby the handleability at the time of manufacturing a polarizing plate etc. can be improved.

  In general, when a film is formed by an extrusion molding method, irregular linear convex portions and concave portions called so-called die lines may be formed on the film surface. In the liquid crystal cell-side protective film used in the present invention, it is preferable that the linear concave portions and the linear convex portions are not substantially formed and the surface thereof is a flat surface. Specifically, the depth of the linear recesses on the film surface or the height of the linear projections is preferably 50 nm or less and the width is 500 nm or more, and the height or depth is 30 nm or less, or the width is 700 nm. More preferably. By adopting such a surface state, it is possible to prevent the occurrence of light interference and light leakage based on the light refraction at the linear concave portions or the linear convex portions, and the optical performance can be improved.

  In addition, the depth of the linear recessed part mentioned above, the height of a linear convex part, and these width | variety can be calculated | required by the method described below. Light is applied to the liquid crystal cell-side protective film, and the transmitted light is projected on the screen. The part with bright or dark stripes of light appearing on the screen (this part is the part where the depth of the concave part and the height of the convex part are large) Is cut out at 30 mm square. The surface of the cut film piece is observed using a three-dimensional surface structure analysis microscope (field region 5 mm × 7 mm), converted into a three-dimensional image, and a cross-sectional profile in the MD direction is obtained from the three-dimensional image. The cross-sectional profile is obtained at 1 mm intervals in the visual field region. An average line is drawn on the cross-sectional profile, and the length from the average line to the bottom of the concave portion is the depth of the concave portion, or the length from the average line to the top of the convex portion is the convex portion height. The distance between the intersection of the average line and the profile is the width. A maximum value is obtained from each of the measured values of the recess depth and the height of the convex portion, and the width of the concave portion or the convex portion showing the maximum value is obtained. The maximum values of the concave depth and convex height obtained from the above, the width of the concave portion and the width of the convex portion showing the maximum values, the depth of the linear concave portion of the film, the height of the linear convex portion And their width.

  The liquid crystal cell-side protective film obtained by laminating the layer composed of the thermoplastic acrylic resin and elastic particles of the present invention and the layer composed of the thermoplastic acrylic resin not containing elastic particles on both sides of the layer is adjacent to each other. The members may be in direct contact with each other or may be in contact with each other through an adhesive layer made of an adhesive (including a pressure-sensitive adhesive). The average thickness of the adhesive layer is usually 0.01 μm to 30 μm, preferably 0.1 μm to 15 μm. The adhesive layer is a layer having a tensile fracture strength according to JIS K7113 of 40 MPa or less. The adhesive constituting this adhesive layer includes acrylic adhesive, urethane adhesive, polyester adhesive, polyvinyl alcohol adhesive, polyolefin adhesive, modified polyolefin adhesive, polyvinyl alkyl ether adhesive, rubber adhesive, vinyl chloride, Vinyl acetate adhesive, styrene / butadiene / styrene copolymer (SBS copolymer) adhesive, hydrogenated product (SEBS copolymer) adhesive, ethylene / vinyl acetate copolymer, ethylene-styrene copolymer, etc. Ethylene adhesives and acrylic ester adhesives such as ethylene / methyl methacrylate copolymers, ethylene / methyl acrylate copolymers, ethylene / ethyl methacrylate copolymers, and ethylene / ethyl acrylate copolymers And so on.

The liquid crystal cell side protective film used in the present invention has a thickness (average thickness) of less than 100 μm, preferably 80 μm or less, more preferably 40 μm or more and 80 μm or less.
In the protective film for the liquid crystal cell side used in the present invention, the thickness of the layer made of a thermoplastic acrylic resin not containing one elastic particle and the thickness of the layer made of a thermoplastic acrylic resin not containing the other elastic particle The difference is preferably 20 μm or less, more preferably 10 μm or less, and further preferably closer to 0 μm.

  The liquid crystal cell-side protective film used in the present invention preferably has a residual solvent content of 0.01% by mass or less. When the residual solvent amount is in the above range, for example, it is possible to prevent the liquid crystal cell-side protective film from being deformed in a high temperature / high humidity environment and to prevent optical performance from being deteriorated. The liquid crystal cell side protective film in which the residual solvent amount falls within the above range can be obtained, for example, by co-extrusion molding a plurality of resins, and by laminating a single thermoplastic resin layer by dry lamination or thermal lamination. . What was obtained by coextrusion molding from the point of productivity is preferable. In the case of coextrusion molding, it is not necessary to go through a complicated process (for example, a drying process or a coating process). Therefore, there is little mixing of external foreign matters such as dust, and excellent optical performance can be exhibited.

The liquid crystal cell-side protective film used in the present invention preferably has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less. By adjusting the moisture permeability to the above-described preferable range, the adhesion between the layers constituting the liquid crystal cell-side protective film can be improved. The moisture permeability can be measured by the cup method described in JIS Z 0208 under the test conditions for 24 hours in an environment of 40 ° C. and 92% RH.

  The liquid crystal cell-side protective film used in the present invention preferably has a total light transmittance of 85% or more, more preferably 90% or more. Further, the protective film preferably has a haze of 2% or less, more preferably 1% or less.

The absolute value of the photoelastic coefficient of the liquid crystal cell-side protective film used in the present invention is preferably 30 × 10 ⁻¹² Pa ⁻¹ or less, more preferably 10 × 10 ⁻¹² Pa ⁻¹ or less. More preferably, it is 5 × 10 ⁻¹² Pa ⁻¹ or less. When the photoelastic coefficient is larger than the above numerical value, the protective film easily develops a phase difference due to external stress, and there is a possibility that optical performance is deteriorated.

The liquid crystal cell side protective film used in the present invention is preferably optically isotropic, specifically, values defined in the in-plane retardation Re (Re = d × (n x -n y) ; n _x is a refractive index of in-plane slow axis, n _y is a refractive index in a direction perpendicular to the slow axis in the plane; d is an average thickness of the film), the thickness direction retardation Rth (Rth = It is preferable that the absolute value of d × ([n _x + _ny ] / 2−n _z ); n _z is the refractive index in the thickness direction) is small. Specifically, the in-plane retardation Re of the protective film is preferably 5 nm or less, more preferably 3 nm or less, and particularly preferably 2 nm or less in the wavelength range of 450 to 750 nm. The thickness direction retardation Rth of the protective film is preferably in the range of -3 nm to +3 nm, particularly preferably in the range of -3 nm to +1 nm, in the wavelength range of 450 to 750 nm.

[Polarizer]
The polarizer used in the present invention is obtained by adsorbing iodine or dichroic dye on a polyvinyl alcohol film and then uniaxially stretching in a boric acid bath, or iodine or dichroic dye on a polyvinyl alcohol film. And the like obtained by adsorbing and stretching, and further modifying a part of the polyvinyl alcohol unit in the molecular chain into a polyvinylene unit. In addition, a polarizer having a function of separating polarized light into reflected light and transmitted light, such as a grid polarizer, a multilayer polarizer, and a cholesteric liquid crystal polarizer, can also be used as the polarizer. Among these, a polarizer comprising polyvinyl alcohol is preferable. The polarization degree of the polarizer is preferably 98% or more, more preferably 99% or more. The thickness (average thickness) of the polarizer is preferably 5 μm to 80 μm.

[Another protective film]
The other protective film used in the present invention may be the same as the above-described liquid crystal cell-side protective film, or may be a protective film conventionally used for polarizing plates. The protective film is preferably formed of a material having a light transmittance in the visible region of 400 to 700 nm at a thickness of 1 mm of 80% or more, more preferably 85% or more, and still more preferably 90% or more. As a resin constituting this conventional protective film, polycarbonate resin, polyethersulfone resin, polyethylene terephthalate resin, polyimide resin, polymethyl methacrylate resin, polysulfone resin, polyarylate resin, polyethylene resin, polystyrene resin, polyvinyl chloride resin, Examples thereof include cellulose esters and alicyclic olefin polymers. Examples of the alicyclic olefin polymer include cyclic olefin random multi-component copolymers described in JP-A No. 05-310845 or US Pat. No. 5,179,171, JP-A No. 05-97978 or US Pat. No. 5,202,388. Examples thereof include the hydrogenated polymers described, thermoplastic dicyclopentadiene ring-opening polymers described in JP-A No. 11-124429 (WO 99/20676), and hydrogenated products thereof. .

<Functional layer>
Another protective film used in the present invention is used as a protective film on the viewing side or the light source side. When the other protective film used in the present invention is used as the viewer-side protective film, a functional layer may be added to the surface. Examples of the functional layer include a hard coat layer, an antireflection layer, an antistatic layer, an antiglare layer, and an antifouling layer. These functional layers may be of one type or a plurality of types.

(Hard coat layer)
A hard coat layer is a layer which has a function which raises the surface hardness of a visual recognition side protective film, and shows hardness more than "H" by the pencil hardness test (a test plate uses a glass plate) shown by JISK5600-5-4. It is preferable. The protective film provided with such a hard coat layer preferably has a pencil hardness of 4H or higher. The material for forming the hard coat layer (hard coat material) is preferably a material curable by heat or light, and organic hard coat materials such as organic silicone, melamine, epoxy, acrylic, and urethane acrylate. And inorganic hard coat materials such as silicon dioxide. Among these, urethane acrylate-based and polyfunctional acrylate-based hard coat materials are preferable from the viewpoint of good adhesive strength and excellent productivity.

  The hard coat layer contains various fillers for the purpose of adjusting the refractive index, improving the flexural modulus, stabilizing the volume shrinkage, and improving heat resistance, antistatic properties, and antiglare properties, as desired. it can. Further, the hard coat layer can contain additives such as an antioxidant, an ultraviolet absorber, a light stabilizer, an antistatic agent, a leveling agent, and an antifoaming agent.

  Fillers for adjusting the refractive index and antistatic properties of the hard coat layer include titanium oxide, zirconium oxide, zinc oxide, tin oxide, cerium oxide, antimony pentoxide, tin-doped indium oxide (ITO), and antimony. Examples thereof include doped tin oxide (IZO), aluminum-doped zinc oxide (AZO), and fluorine-doped tin oxide (FTO). As the filler, antimony pentoxide, ITO, IZO, ATO, and FTO are preferable in that transparency can be maintained. The primary particle diameter of these fillers is usually 1 nm to 100 nm, preferably 1 nm to 30 nm. In the present invention, when a filler is used for the hard coat layer, it is preferable to use a filler having a refractive index of 1.6 or more. Use of a filler having a refractive index in the above range is preferable because the hard coat layer can also function as a high refractive index layer described later, and the process is simplified.

  The filler for imparting antiglare properties preferably has an average particle size of 0.5 μm to 10 μm, more preferably 1.0 μm to 7.0 μm, and even more preferably 1.0 μm to 4.0 μm. Specific examples of fillers that impart antiglare properties include polymethyl methacrylate resins, vinylidene fluoride resins and other fluororesins, silicone resins, epoxy resins, nylon resins, polystyrene resins, phenol resins, polyurethane resins, crosslinked acrylic resins, Filler made of organic resin such as crosslinked polystyrene resin, melamine resin, benzoguanamine resin; or inorganic such as titanium oxide, aluminum oxide, indium oxide, zinc oxide, antimony oxide, tin oxide, zirconium oxide, ITO, magnesium fluoride, silicon oxide The filler which consists of a compound can be mentioned.

Hard coat layer has a refractive index _{n H} is between the refractive index _{n L} of the anti-reflection layer described later laminated thereon, _{n H} ≧ 1.53, and _n ^H 1/2 -0.2 It is preferable to have a relationship of <n _L <n _H ^1/2 +0.2 in order to develop the antireflection function.

(Antireflection layer)
The antireflection layer is a layer for preventing the transfer of external light, and is laminated directly or via another layer such as a hard coat layer on the surface (surface exposed to the outside) of the viewing side protective film. The protective film provided with the antireflection layer preferably has an incident angle of 5 °, a reflectance at a wavelength of 430 nm to 700 nm of 2.0% or less, and a reflectance at a wavelength of 550 nm of 1.0% or less. preferable.

  The thickness of the antireflection layer is preferably 0.01 μm to 1 μm, more preferably 0.02 μm to 0.5 μm. The antireflection layer has a refractive index smaller than the refractive index of a layer (such as a protective film or a hard coat layer) on which the antireflection layer is laminated, specifically a low refractive index of 1.30 to 1.45. Examples thereof include those composed of a refractive index layer; those obtained by alternately laminating a plurality of low refractive index layers of a thin film made of an inorganic compound and high refractive index layers of a thin film made of an inorganic compound.

  The material for forming the low refractive index layer (low refractive index forming material) is not particularly limited as long as it has a low refractive index. Examples thereof include a resin material such as an ultraviolet curable acrylic resin, a hybrid material in which inorganic fine particles such as colloidal silica are dispersed in the resin, and a sol-gel material using a metal alkoxide such as tetraethoxysilane. The material for forming these low refractive index layers may be a polymerized polymer, or may be a monomer or oligomer serving as a precursor. Moreover, it is preferable that each material contains the compound containing a fluorine group, in order to provide antifouling property.

As the sol-gel material, a sol-gel material containing a fluorine group is preferably used. Examples of the sol-gel material containing a fluorine group include perfluoroalkylalkoxysilane. Perfluoroalkylalkoxysilane is, for example, general formula (1): CF ₃ (CF ₂ ) _n CH ₂ CH ₂ Si (OR) ₃ (wherein R represents an alkyl group having 1 to 5 carbon atoms, n represents an integer of 0 to 12). Specifically, as perfluoroalkylalkoxysilane, trifluoropropyltrimethoxysilane, trifluoropropyltriethoxysilane, tridecafluorooctyltrimethoxysilane, tridecafluorooctyltriethoxysilane, heptadecafluorodecyltrimethoxysilane , And heptadecafluorodecyltriethoxysilane. Among these, the compound whose said n is 2-6 is preferable.

  The low refractive index layer can be made of a cured product of a thermosetting fluorine-containing compound or an ionizing radiation curable fluorine-containing compound. The cured product preferably has a dynamic friction coefficient of 0.03 to 0.15, and a contact angle with water of 90 to 120 degrees. Examples of the curable fluorine-containing compound include a perfluoroalkyl group-containing silane compound (for example, (heptadecafluoro-1,1,2,2-tetradecyl) triethoxysilane) and the like, and a fluorine-containing polymer having a crosslinkable functional group. Can be mentioned.

This fluorine-containing polymer having a crosslinkable functional group is obtained by copolymerizing a fluorine-containing monomer and a monomer having a crosslinkable functional group, or by copolymerizing a fluorine-containing monomer and a monomer having a functional group, and then polymer. It can be obtained by adding a compound having a crosslinkable functional group to the functional group therein.
Fluoroolefins such as fluoroethylene, vinylidene fluoride, tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoro-2,2-dimethyl-1,3-dioxole; biscoat 6FM (Osaka Organic) Chemical), M-2020 (manufactured by Daikin), (meth) acrylic acid partial or fully fluorinated alkyl ester derivatives, fully or partially fluorinated vinyl ethers, and the like.

  Monomers having a crosslinkable functional group or compounds having a crosslinkable functional group include monomers having a glycidyl group such as glycidyl acrylate and glycidyl methacrylate; monomers having a carboxyl group such as acrylic acid and methacrylic acid; hydroxyalkyl acrylate and hydroxyalkyl Monomers having hydroxyl groups such as methacrylate, methylol acrylate, methylol methacrylate; monomers having vinyl groups such as allyl acrylate and allyl methacrylate; monomers having amino groups; monomers having sulfonic acid groups; etc .; hydroxyalkyl (meth) Examples include acrylate and allyl acrylate.

  As a material for forming the low refractive index layer, a material containing a sol in which fine particles such as silica, alumina, titania, zirconia, magnesium fluoride and the like are dispersed in an alcohol solvent is used because it can improve scratch resistance. Can do. From the viewpoint of antireflection properties, the fine particles preferably have a lower refractive index. Such fine particles may have voids, and silica hollow fine particles are particularly preferable. The average particle size of the hollow fine particles is preferably 5 nm to 2,000 nm, and more preferably 20 nm to 100 nm. Here, the average particle diameter is a number average particle diameter obtained by observation with a transmission electron microscope.

  In the case of a low refractive index layer made of a cured product of a fluorine-containing compound, the scratch resistance of the low refractive index layer tends to decrease when the refractive index of the cured product is lowered. By optimizing the amount of addition, it is possible to achieve both scratch resistance and a low refractive index.

  The method for forming the low refractive index layer is not particularly limited, but the wet coating method is preferable because it is a simpler method than the vacuum deposition method or the like. Examples of the wet coating method include dip coating, air knife coating, curtain coating, roller coating, wire bar coating, and gravure coating. The thickness of the low refractive index layer is preferably about 0.05 μm to 0.3 μm, particularly preferably 0.1 μm to 0.3 μm.

(Anti-fouling layer)
The antifouling layer is a layer that can impart water repellency, oil repellency, sweat resistance, antifouling properties, and the like. As a material used for forming the antifouling layer, a fluorine-containing organic compound is suitable. Examples of the fluorine-containing organic compound include fluorocarbon, perfluorosilane, and polymer compounds thereof. As a method for forming the antifouling layer, a physical vapor deposition method such as vapor deposition or sputtering, a chemical vapor deposition method, a wet coating method, or the like can be used depending on the material to be formed. The average thickness of the antifouling layer is preferably 1 nm to 50 nm, more preferably 3 nm to 35 nm.

  When the functional layer as described above is formed, it is preferable to perform a chemical surface treatment on the surface to be formed. Examples of the chemical surface treatment include corona discharge treatment, sputtering treatment, low-pressure UV irradiation treatment, and plasma treatment. In addition to the chemical surface treatment, the display screen protective film of the present invention is subjected to mechanical treatment by etching, sandblasting, embossing roll, etc. for the purpose of enhancing adhesion to the functional layer and imparting antiglare properties. May be.

  As a suitable polarizing plate for liquid crystal display of this invention, what is further provided with the film which shows birefringence is mentioned. A film exhibiting birefringence is laminated on the outer surface of the liquid crystal cell side protective film. That is, it laminates | stacks so that the film which shows birefringence may be arrange | positioned between a liquid crystal cell and a polarizing plate. By providing the film exhibiting the birefringence, optical compensation functions such as color compensation and viewing angle compensation are provided, and the visibility of the liquid crystal display device is improved. In addition, by giving the film having the birefringence two functions of a protective film for a polarizer and an optical compensation film, the total number of films can be reduced, leading to weight reduction. This leads to simplification of the process.

The film showing birefringence is a film whose birefringence is controlled in the width direction and the longitudinal direction, and examples thereof include a uniaxial film, a biaxial film, and a laminate thereof. The film showing the desired birefringence is appropriately selected according to the mode of the liquid crystal cell used. The refractive indices n _x in the slow axis direction of the film plane and having _uniaxial, the slow axis and the direction of the refractive index perpendicular in the plane n _y in the _plane, the refractive index in the thickness direction n _z One of the refractive indexes is different from the other two refractive indexes, specifically, _nx > _ny = _nz (a film showing such a relationship is called a positive A plate) _Nx = _ny > _nz (a film showing such a relationship may be referred to as a negative C plate) _ny < _nx = _nz (a film showing such a relationship is negative) It may be referred to as an A plate.), And n _x = ny _y <n _z (a film exhibiting such a relationship may be referred to as a positive C plate). Second and has an axial, say that different the three directions of the refractive index of all, for _{example, n x> n y> n} z, and _refers to showing a _{n y <n} x _{<n z} the relationship. The retardation Re in the in-plane direction of the film and the retardation Rth in the thickness direction, which express the mutual relationship between the refractive indexes _nx , _ny , and _nz as numerical values, indicate the mode of the liquid crystal cell to be used and the cell. It adjusts suitably according to Re and Rth which the protective film arrange | positioned at the cell side of the other polarizing plate which opposes on both sides has. For example, when the liquid crystal mode is a vertical alignment (VA) mode, a single birefringent film having a retardation Rth in the thickness direction of 70 to 400 nm, or a birefringence having an Rth of 50 to 250 nm. It is preferable to use two films shown.
The in-plane direction retardation Re, retardation Rth in the thickness direction, the thickness of the film upon the _{d (nm), Re = (} n x -n y) × d, Rth = ((n _x + n _y ) / 2−n _z ) × d.

  Birefringent films include those obtained by stretching a film containing a thermoplastic resin, those obtained by forming an optically anisotropic layer on an unstretched thermoplastic resin film, and optical on a film containing a thermoplastic resin. After forming the anisotropic layer, it can be further stretched. The stretched film exhibiting birefringence may be a single layer film or a laminated film.

<A stretched film containing a thermoplastic resin>
The thermoplastic resin used for obtaining a film exhibiting birefringence can be selected from those exemplified as the resin constituting the protective film. Among these, an alicyclic olefin polymer and a cellulose ester are preferable because of excellent transparency and dimensional stability.

As the cellulose ester, those having an acyl group substitution degree of 2.5 to 2.9 determined according to ASTM D-817-96 can be preferably used. Examples of the acyl group include an acetyl group, a propionyl group, and a butyryl group. In the present invention, a mixture of cellulose esters having different substituents such as cellulose acetate propionate can also be used preferably. Among them, acetyl group and propionyl group are substituted with acetyl group substitution degree A and propionyl group substitution degree. Cellulose ester containing so as to satisfy the following formula when B is B is preferred.
(1) 2.5 <(A + B) <2.9
(2) 1.5 <A <2.9

  A retardation increasing agent can be added to the resin constituting the film exhibiting birefringence, if necessary. When a retardation increasing agent is added to the resin, the retardation obtained by stretching becomes higher than that in the case of no addition. When a retardation increasing agent is added to the cellulose ester, it is preferably used in the range of 0.01 to 20 parts by mass and used in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the cellulose ester. More preferably, it is more preferably used in the range of 0.2 to 5 parts by mass, and most preferably in the range of 0.5 to 2 parts by mass. Two or more types of retardation increasing agents may be used in combination. The retardation increasing agent preferably has a maximum absorption in a wavelength region of 250 to 400 nm. The retardation increasing agent preferably has substantially no absorption in the visible region.

  As the retardation increasing agent, it is preferable to use a compound having at least two aromatic rings. In the present specification, the “aromatic ring” includes an aromatic hetero ring in addition to an aromatic hydrocarbon ring. The aromatic hydrocarbon ring is particularly preferably a 6-membered ring (that is, a benzene ring). The aromatic heterocycle is generally an unsaturated heterocycle. The aromatic heterocycle is preferably a 5-membered ring, 6-membered ring or 7-membered ring, more preferably a 5-membered ring or 6-membered ring. Aromatic heterocycles generally have the most double bonds. As the hetero atom, a nitrogen atom, an oxygen atom and a sulfur atom are preferable, and a nitrogen atom is particularly preferable. Examples of aromatic heterocycles include furan ring, thiophene ring, pyrrole ring, oxazole ring, isoxazole ring, thiazole ring, isothiazole ring, imidazole ring, pyrazole ring, furazane ring, triazole ring, pyran ring, pyridine ring , Pyridazine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring. As the aromatic ring, benzene ring, furan ring, thiophene ring, pyrrole ring, oxazole ring, thiazole ring, imidazole ring, triazole ring, pyridine ring, pyrimidine ring, pyrazine ring and 1,3,5-triazine ring are preferable.

  The number of aromatic rings contained in the retardation increasing agent is preferably 2 to 20, more preferably 2 to 12, further preferably 2 to 8, and most preferably 2 to 6. preferable. The bonding relationship between two aromatic rings can be classified into (a) when a condensed ring is formed, (b) when directly linked by a single bond, and (c) when linked via a linking group (for aromatic rings). , Spiro bonds cannot be formed). The connection relationship may be any of (a) to (c).

  As a method of stretching the film containing the thermoplastic resin, a uniaxial stretching method such as a method of stretching uniaxially in a transverse direction using a tenter; a gap between fixed clips is opened and a guide rail spreads simultaneously with stretching in the longitudinal direction. Simultaneous biaxial stretching method that stretches in the transverse direction depending on the angle, or sequential stretching that stretches in the longitudinal direction using the difference in peripheral speed between rolls and then grips both ends of the clip and stretches in the transverse direction using a tenter. Biaxial stretching method such as axial stretching method; Tenter stretching machine that can add feed force or pulling force or pulling force at different speeds in the horizontal or vertical direction; Alternatively, using a tenter stretching machine that can add a pulling force or a pulling force so that the moving distance is the same and the stretching angle θ can be fixed, or the moving distance is different. And the like: How to fit stretching

  Stretching can usually be performed in the range of Tg to Tg + 20 ° C., where Tg is the glass transition temperature of the resin forming the film, particularly the resin having the lowest glass transition temperature. Moreover, what is necessary is just to adjust a draw ratio in order to obtain a desired optical characteristic in the range of 1.1 to 3.0 times normally.

<Those formed with an optically anisotropic layer on an unstretched thermoplastic resin film>
For the formation of the optically anisotropic layer, a polymer compound or a liquid crystal compound can be used. These may be used alone or in combination.

  As the polymer compound, polyamide, polyimide, polyester, polyether ketone and the like can be used. Specific examples include compounds described in JP-T-8-511812 (International Publication No. WO94 / 24191) and JP-T 2000-511296 (International Publication No. WO97 / 44704).

  Further, the liquid crystalline compound may be a rod-like liquid crystal or a discotic liquid crystal, and these include a polymer liquid crystal or a low-molecular liquid crystal, and those in which a low-molecular liquid crystal is cross-linked and no longer exhibits liquid crystallinity. . Preferable examples of the rod-like liquid crystal include those described in JP 2000-304932A. Preferred examples of the discotic liquid crystal include those described in JP-A-8-50206.

  The optically anisotropic layer is generally formed by applying a solution of a discotic compound and other compounds (eg, plasticizer, surfactant, polymer, etc.) dissolved in a solvent onto the alignment film, drying, and then discotic nematic. It can be obtained by heating to the phase formation temperature and then cooling while maintaining the orientation state (discotic nematic phase). Alternatively, the optically anisotropic layer may be formed by applying a solution obtained by dissolving a discotic compound and another compound (for example, a polymerizable monomer, a photopolymerization initiator) in a solvent onto the alignment film, drying, and then discotic It can be obtained by heating to a nematic phase formation temperature, followed by polymerization by irradiation with UV light, etc., and further cooling. The alignment state can be appropriately adjusted according to the mode of the liquid crystal to be used. For example, when the liquid crystal cell is in the horizontal alignment mode (IPS), it is preferable that the liquid crystal cell is substantially vertically aligned on the substrate, and when the liquid crystal cell is in the bend alignment mode (OCB) or the twist alignment mode (TN). Is preferably in a state where the optical axis is in a hybrid orientation in the film thickness direction.

  The thickness of the optically anisotropic layer is preferably 0.1 to 10 μm, more preferably 0.5 to 5 μm, and most preferably 0.7 to 5 μm. However, depending on the mode of the liquid crystal cell, it may be thickened (3 to 10 μm) in order to obtain high optical anisotropy. The method for producing the protective film including the optically anisotropic layer is not particularly limited. For example, the polymer film and / or the liquid crystalline compound is applied to a film containing a thermoplastic resin to produce a coated film. The coated film can be produced by further stretching or shrinking.

<Liquid crystal display device>
The liquid crystal display device of the present invention comprises the liquid crystal display polarizing plate. In the liquid crystal display device, a light source, an incident side polarizing plate, a liquid crystal cell, and an output side polarizing plate are usually arranged in this order. In the liquid crystal display device of the present invention, the polarizing plate of the present invention comprising a liquid crystal cell side protective film, a polarizer and a light source side protective film is disposed as the incident side polarizing plate so that the liquid crystal cell side protective film faces the liquid crystal cell. Further, in another liquid crystal display device of the present invention, the polarizing plate of the present invention comprising a liquid crystal cell side protective film, a polarizer, and a viewing side protective film is disposed as an output side polarizing plate so that the liquid crystal cell side protective film faces the liquid crystal cell. To do. Furthermore, in another liquid crystal display device of the present invention, the incident side polarizing plate and the outgoing side polarizing plate are arranged as described above.

  Examples of the light source used in the liquid crystal display device of the present invention include a light emitting diode, a cold cathode tube, a hot cathode tube, and an EL. The liquid crystal cell is not particularly limited as long as it is used in a liquid crystal display device. For example, a TN (Twisted Nematic) type liquid crystal cell, an STN (Super Twisted Nematic) type liquid crystal cell, a HAN (Hybrid Alignment Nematic) type liquid crystal cell, an IPS (In Plane Switching) type liquid crystal cell, and a VA (vertical type liquid crystal cell). Examples include a MVA (Multiple Vertical Alignment type liquid crystal cell, an OCB (Optical Compensated Bend) type liquid crystal cell, etc. The liquid crystal display device of the present invention further includes a retardation plate, a brightness enhancement film, a light guide plate, a light A diffusing plate, a light diffusing sheet, a light collecting sheet, a reflecting plate, and the like may be provided.

The present invention will be described in more detail with reference to examples and comparative examples. Parts and% are based on mass unless otherwise specified.
The protective films obtained in Examples and Comparative Examples were evaluated by the following methods.

<Refractive index of hard coat layer and low refractive index layer>
Using a high-speed spectroscopic ellipsometer (manufactured by JA Woollam, M-2000U) under the conditions of a temperature of 20 ± 2 ° C. and a humidity of 60 ± 5%, the incident angles are 55 degrees, 60 degrees, and 65 degrees, and the wavelength. The spectrum in the region of 400 to 1000 nm was measured and calculated from these measurement results.

<Refractive index of each resin layer>
A thermoplastic resin is molded into a single layer, and a prism coupler (manufactured by Metricon, model 2010) is used, and the refractive indices at wavelengths of 633 nm, 407 nm, and 532 nm are measured under conditions of a temperature of 20 ± 2 ° C. and a humidity of 60 ± 5%. From the value, the refractive index of 380 nm to 780 nm was calculated by the Caucy's dispersion formula.

<Re and Rth of protective film and wavelength dispersion>
High-speed spectroscopic ellipsometer [J. A. Using Woollam, M-2000U], Re and Rth were measured in a wavelength range of 450 to 780 nm, Re and Rth at a wavelength of 550 nm, and the difference between the maximum value and the minimum value of Re in a wavelength range of 450 to 750 nm, In addition, the difference between the maximum value and the minimum value of Rth in the wavelength range of 450 to 750 nm was defined as the respective wavelength dispersion. The same measurement was carried out at 10 points at equal intervals in the width direction of the protective film, and the average value was calculated.

<Tensile modulus>
A thermoplastic resin film is formed, a 1 cm × 25 cm test piece is cut out, and measured under a tensile speed of 25 mm / min using a tensile tester (manufactured by Toyo Baldwin, Tensilon UTM-10T-PL) based on ASTM882. did. The same measurement was performed 5 times, and the arithmetic average value was taken as the representative value of the tensile modulus.

<Thickness of each resin layer>
After embedding the protective film in an epoxy resin, it was sliced using a microtome (RUB-2100, manufactured by Yamato Kogyo Co., Ltd.), and the cross section was observed and measured using a scanning electron microscope.

<Photoelastic coefficient of protective film>
While applying a load to the protective film in the range of 50 to 150 g, the in-plane retardation of the film is measured, and this is divided by the thickness of the film to determine the birefringence value Δn. Δn was obtained while changing the load, a load-Δn curve was created, and the slope was taken as the photoelastic coefficient.

<Haze of protective film>
Based on JIS K7361-1997, it measures using "Nippon Denshoku Industries Co., Ltd." turbidimeter NDH-300A ". In addition, the same measurement is performed 5 times and the arithmetic average value is set as the representative value of haze.

<Water permeability of protective film>
The measurement was performed by a method according to the cup method described in JIS Z 0208 under the test conditions of leaving for 24 hours in an environment of 40 ° C. and 92% RH. The unit of moisture permeability is g · m ⁻² · day ⁻¹ .

<Residual solvent content of protective film>
The residual solvent content of the protective film was determined by adding 50 mg of protective film to a glass tube sample container with an inner diameter of 4 mm from which moisture and organic substances adsorbed on the surface were completely removed, and then heating the container at a temperature of 200 ° C. for 30 minutes. And the gas which came out of the container was collected continuously. The collected gas was analyzed with a thermal desorption gas chromatography mass spectrometer (TDS-GC-MS).

<Measuring method of depth of linear concave part, height of linear convex part and their width>
By the method described above, the depth of the linear concave portion, the height of the linear convex portion, and the width thereof were measured. The maximum value of the obtained concave depth and convex height, the width of the concave portion and the width of the convex portion showing the maximum value, the depth of the linear concave portion of the film, the height of the linear convex portion and those And evaluated according to the following criteria.
A: Depth of linear recess or height of projection is less than 20 nm and width is 800 nm or more. O: Depth of linear recess or height of projection is 50 nm or less and width is less than 800 nm. Or, the depth of the linear concave portion or the height of the convex portion is 20 nm or more and the width is 500 nm or more. X: The depth of the linear concave portion or the height of the convex portion exceeds 50 nm and the width is less than 500 nm.

(Preparation of composition for forming high refractive index layer (hard coat layer))
30 parts of a hexafunctional urethane acrylate oligomer, 40 parts of butyl acrylate, 30 parts of isobornyl methacrylate and 10 parts of 2,2-diphenylethane-1-one were mixed with a homogenizer, and antimony pentoxide fine particles (average particle size 20 nm, hydroxyl group A 40% methyl isobutyl ketone solution having a mass of antimony pentoxide fine particles of 50% of the total solid content of the composition for forming a high refractive index layer. The composition H for forming a high refractive index layer was prepared by mixing at a ratio of mass%.

(Preparation of composition for forming low refractive index layer)
21 parts of tetramethoxysilane oligomer, 36 parts of methanol, 2 parts of water and 2 parts of 0.01N hydrochloric acid aqueous solution were mixed and stirred in a high-temperature bath at 25 ° C. for 2 hours to obtain a silicone resin having a weight average molecular weight of 850. Obtained. Next, an isopropanol-dispersed sol (solid content 20%, average primary particle diameter of about 35 nm, outer shell thickness of about 8 nm) of hollow silica fine particles is added to the silicone resin to obtain hollow silica fine particles / silicone resin (condensed compound equivalent). The mass ratio based on solid content was 8: 2. Finally, the composition L for forming a low refractive index layer was prepared by diluting with methanol so that the total solid content was 1%.

(Production of polarizer)
A polyvinyl alcohol film having a refractive index of 1.545 at a wavelength of 380 nm and a refractive index of 1.521 at a wavelength of 780 nm and a thickness of 75 μm is uniaxially stretched 2.5 times to obtain 0.2 g of iodine and 60 g of potassium iodide. Was immersed in an aqueous solution containing 30 g / L for 30 seconds and then immersed in an aqueous solution containing 70 g / L of boric acid and 30 g / L of potassium iodide and simultaneously uniaxially stretched 6.0 times and held for 5 minutes. Finally, it was dried at room temperature for 24 hours to obtain a polarizer P having an average thickness of 30 μm and a polarization degree of 99.95%.

Example 1
(Preparation of protective film 1)
Double flight type uniaxial extrusion with polymethylmethacrylate resin not containing elastic particles (tensile modulus 3.3 GPa; hereinafter referred to as “PMMA”) installed with a leaf disk-shaped polymer filter with an aperture of 10 μm The molten resin was fed into one of the multi-manifold dies having a die slip surface roughness Ra of 0.1 μm at an extruder outlet temperature of 260 ° C.
On the other hand, a polymethyl methacrylate resin (tensile elastic modulus 2.8 GPa; hereinafter may be referred to as “R-PMMA1”) containing elastic particles having a number average particle size of 0.4 μm is shaped as a leaf disk having an opening of 10 μm. The polymer filter was introduced into a double flight type single screw extruder, and the molten resin was supplied to the other side of the multi-manifold die having a die slip surface roughness Ra of 0.1 μm at an extruder outlet temperature of 260 ° C.

Then, the polymethyl methacrylate resin not containing the elastic particles in the molten state and the polymethyl methacrylate resin containing the elastic particles are each discharged from the multi-manifold die at 260 ° C. and cast to a cooling roll whose temperature is adjusted to 130 ° C. Then, it passes through a cooling roll whose temperature is adjusted to 50 ° C., and consists of a three-layer structure of PMMA layer (20 μm) / R-PMMA1 layer (40 μm) / PMMA layer (20 μm), protection of 600 mm width and 80 μm thickness Film 1 was obtained by coextrusion.
Table 1 shows the evaluation results of Re, Rth, photoelastic coefficient, moisture permeability, residual solvent amount, linear unevenness and haze of the protective film 1.

(Preparation of protective film 1A <Addition of antireflection layer>)
Corona discharge treatment was performed on both surfaces of the protective film 1 using a high frequency transmitter (output 0.8 kW), and the surface tension was adjusted to 0.055 N / m.
Next, the high refractive index layer forming composition H was applied to one surface of the protective film 1 using a die coater, and dried in an oven at 80 ° C. for 5 minutes to obtain a coating. This film was irradiated with ultraviolet rays (accumulated dose 300 mJ / cm ² ) to form a high refractive index layer having a thickness of 6 μm. The refractive index of the high refractive index layer was 1.62, and the pencil hardness was 4H.
On the formed high refractive index layer, the composition L for forming a low refractive index layer is applied using a wire bar coater, left to stand for 1 hour and dried, and the resulting film is kept at 120 ° C. for 10 minutes. Then, heat treatment was performed in an oxygen atmosphere to form a low-refractive index layer (refractive index 1.36) having a thickness of 100 nm to obtain a protective film 1A with an antireflection layer.

(Preparation of polarizing plate 1)
A polyvinyl alcohol-based adhesive is applied to both surfaces of the polarizer P, one surface of the protective film 1 and the surface of the protective film 1A on which the antireflection layer is not formed are layered on the polarizer P, and bonded together by a roll-to-roll method. A polarizing plate 1 was obtained.

Example 2
(Preparation of polarizing plate 2)
Except for changing the thickness of each layer to PMMA layer (10 μm) / R-PMMA1 layer (20 μm) / PMMA layer (10 μm), the same structure as in Example 1, consisting of three layers, width 600 mm, thickness 40 μm The protective film 2 was obtained by coextrusion molding. Table 1 shows the evaluation results of Re, Rth, photoelastic coefficient, moisture permeability, residual solvent amount, linear unevenness and haze of the protective film 2.
Using this protective film 2, an antireflection layer was added in the same manner as in Example 1 to obtain a protective film 2A with an antireflection layer. A polarizing plate 2 was produced in the same manner as in Example 1 except that the protective film 2 was used instead of the protective film 1 and the protective film 2A was used instead of the protective film 1A.

Example 3
(Preparation of polarizing plate 3)
Polymethylmethacrylate resin containing elastic particles (tensile modulus 2.8 GPa; R-PMMA1), polymethylmethacrylate resin containing elastic particles having a number average particle size of 0.2 μm (tensile modulus 2.5 GPa; below) In the same manner as in Example 1, except that it is changed to “R-PMMA2”), a PMMA layer (20 μm) / R-PMMA2 layer (40 μm) / PMMA layer (20 μm) three-layer structure is used. A protective film 3 having a width of 600 mm and a thickness of 80 μm was obtained by coextrusion molding. Table 1 shows the evaluation results of Re, Rth, photoelastic coefficient, moisture permeability, residual solvent amount, linear unevenness and haze of the protective film 3.
Using this protective film 3, an antireflection layer was added in the same manner as in Example 1 to obtain a protective film 3A with an antireflection layer. A polarizing plate 3 was produced in the same manner as in Example 1 except that the protective film 3 was used instead of the protective film 1 and the protective film 3A was used instead of the protective film 1A.

(Preparation of protective film 0)
25 mL / m ² of a 1.5 mol / L isopropyl alcohol solution of potassium hydroxide was applied to one side of a 80 μm thick triacetylcellulose film and dried at 25 ° C. for 5 seconds. Next, the film was washed with running water for 10 seconds, and finally the surface of the film was dried by blowing air at 25 ° C. to obtain a protective film 0 in which only one surface of the triacetylcellulose film was saponified.

Example 4
(Preparation of polarizing plate 4)
A polyvinyl alcohol adhesive is applied to both sides of the polarizer P, the surface of the protective film 0 that has been subjected to saponification treatment and one surface of the protective film 1 are overlapped toward the polarizer P, and are bonded together by a roll-to-roll method. A plate 4 was obtained.

Comparative Example 1
(Preparation of polarizing plate 5)
A polymethyl methacrylate resin (tensile modulus 3.3 GPa; PMMA) not containing elastic particles was extruded to obtain a single-layer film (protective film 4) having a thickness of 80 μm. Table 1 shows the evaluation results of Re, Rth, photoelastic coefficient, moisture permeability, residual solvent amount, linear unevenness and haze of the protective film 4. Using this protective film 4, an antireflection layer was added in the same manner as in Example 1 to obtain a protective film 4A with an antireflection layer.
A polarizing plate 5 was produced in the same manner as in Example 1 except that the protective film 4 was used instead of the protective film 1 and the protective film 4A was used instead of the protective film 1A.

Comparative Example 2
(Preparation of polarizing plate 6)
Triacetylcellulose (tensile modulus 3.8 GPa; TAC) was solution cast molded to obtain a single-layer film (protective film 5) having a thickness of 80 μm. Table 1 shows the evaluation results of Re, Rth, photoelastic coefficient, moisture permeability, residual solvent amount, linear unevenness and haze of the protective film 5. Using this protective film 5, an antireflection layer was added in the same manner as in Example 1 to obtain a protective film 5A with an antireflection layer.
A polarizing plate 6 was produced in the same manner as in Example 1 except that the protective film 5 was used instead of the protective film 1 and the protective film 5A was used instead of the protective film 1A.

The polarizing plates obtained in Examples and Comparative Examples were evaluated by the following methods. The results are shown in Table 2.
<Flexibility test>
A polarizing plate was punched into 1 cm × 5 cm to obtain a test film. The obtained test film was wound around a steel rod having a diameter of 3 mmφ, and whether or not the wound film was broken at the rod was tested. The test was conducted a total of 10 times, and the flexibility was expressed by the following index according to the number of times the test was not broken.
○: One or less pieces of broken film ×: Two or more pieces of broken film

<Light leakage>
Two test polarizing plates are placed in crossed Nicols with the protective films facing each other, the light transmittances at the nine locations shown in FIG. 1 are measured, and the measured values are substituted into the following formula to calculate the light leakage degree. Calculated.
Light leakage = ((T2 + T4 + T6 + T8) / 4) / ((T1 + T3 + T5 + T7 + T9) / 5)
Tx represents the light transmittance at the measurement point (x), and (1), (2), (3), (4), (6), (7), (8), and (9) are A position 10 mm from the end was taken as a measurement point. In (5), the diagonal intersection of the test polarizing plate was used as the measurement point.
○: Light leakage is 2 or less ×: Light leakage is greater than 2

<Color shift>
The degree of change in color tone within a polar angle range of 0 to 60 degrees was visually observed and evaluated according to the following criteria.
○: Not concerned at all ×: Change in color is observed Further, with respect to the polarizing plates obtained in Example 1 and Comparative Example 2, polar angles 0 to 60 degrees and azimuth angles 0 to 360 degrees (each 10 FIG. 2 and FIG. 3 show the plots of the color shift in degrees) on the chromaticity diagram.

<Viewing angle characteristics>
The liquid crystal display device was displayed in black, and the display characteristics from the front direction and an oblique direction within a polar angle of 80 degrees were visually observed and evaluated according to the following criteria.
○: Contrast is not observed ×: Contrast is observed at polar angle and azimuth angle In addition, with respect to the polarizing plates obtained in Example 1 and Comparative Example 2, luminance diagrams are shown in FIGS. 4 and 5 by simulation. . In the figure,% is a luminance ratio (= transmitted light luminance / incident light luminance).

The figure which shows the measuring point of a polarization degree change and light leakage. The figure which plotted the color shift of the polar angle 0-60 degree | times of the polarizing plate obtained in Example 1, and the azimuth | direction angle 0-360 degree | times (each 10 degree | times) on a chromaticity diagram. The figure which plotted on the chromaticity diagram the color shift of the polar angle 0-60 degree | times of the polarizing plate obtained in the comparative example 2, and the azimuth | direction angle 0-360 degree | times (each 10 degree | times). FIG. 3 is a luminance diagram of the polarizing plate obtained in Example 1. FIG. 11 is a luminance diagram of the polarizing plate obtained in Comparative Example 2.

Explanation of symbols

(1) to (9): Measurement points

Claims (8)

Liquid crystal cell side protection comprising a thermoplastic acrylic resin as a main component, elastic particles having a number average particle size of 2.0 μm or less are unevenly distributed in the central portion in the film thickness direction, and the average thickness is less than 100 μm the film,
A polarizing plate for liquid crystal display, comprising another protective film and a polarizer disposed between the protective films. The average thickness formed by laminating a layer composed of a thermoplastic acrylic resin and elastic particles having a number average particle size of 2.0 μm or less and a layer composed of a thermoplastic acrylic resin on both sides of the layer is less than 100 μm A liquid crystal cell side protective film,
A polarizing plate for liquid crystal display, comprising another protective film and a polarizer disposed between the protective films.   The polarizing plate according to claim 1, wherein the liquid crystal cell side protective film has a haze of 2% or less.   The polarizing plate according to claim 1, wherein the liquid crystal cell-side protective film has a retardation Rth in the thickness direction in a range of −3 nm to +3 nm in a wavelength range of 450 to 750 nm. The polarizing plate according to claim 1, wherein the liquid crystal cell-side protective film has a moisture permeability of 10 g · m ⁻² day ⁻¹ or more and 200 g · m ⁻² day ⁻¹ or less.   The polarizing plate according to claim 1, wherein the liquid crystal cell-side protective film is obtained by coextrusion molding.   The polarizing plate according to claim 6, wherein the liquid crystal cell-side protective film has a depth of linear recesses on the film surface or a height of linear protrusions of 50 nm or less and a width of 500 nm or more. The polarizing plate according to any one of claims 1 to 7 is provided so that the protective film on the liquid crystal cell side of the polarizing plate faces the liquid crystal cell side, and the other protective film faces the viewing side or the light source side. Liquid crystal display device.

Images