JP5382118B2 - Polarizing plate and liquid crystal display device - Google Patents

Description

  The present invention relates to a polarizing plate and a liquid crystal display device.

  In general, two polarizing plates are bonded to a liquid crystal cell constituting a liquid crystal display panel of a liquid crystal display device (LCD). This polarizing plate is a polarizing element in which a polyvinyl alcohol (hereinafter abbreviated as PVA) film adsorbed and dyed with iodine or a dichroic dye is stretched and oriented in a certain direction between two cellulose-based protective films ( It has a three-layer structure with a polarizing film) in between. Moreover, in order to bond a polarizing plate and the board | substrate of a liquid crystal cell, the adhesive layer is provided in the cellulose protective film single side | surface.

  The protective film on the outermost surface of the polarizing plate used in the liquid crystal cell is particularly susceptible to physical damage, and when it is damaged, the display image quality is impaired. Therefore, a hard coat layer is formed on the substrate of the cellulose-based protective film. The provided hard coat film is used.

  In recent years, a hard coat film is required to be a clear type rather than an anti-glare treatment type that blurs the outline of an image reflected on the surface from the viewpoint of higher contrast and visibility (clearness).

  On the other hand, as the use of liquid crystal display devices is further expanded, the durability of liquid crystal display panels is demanded, and the necessity to store or use in harsh environments with high temperature and humidity for a long time has arisen. It was.

  If the polarizing plate provided with the adhesive layer of the liquid crystal display panel is assumed to be transported and stored under high temperature and high humidity for a long time in a stacked state, it will be partially on the outermost surface of the polarizing plate due to blocking etc. Deformation failures are likely to occur, which is a quality problem.

  For example, Patent Document 1 discloses a technique for polarizing plates that improves durability under high temperature and high humidity conditions. This technique improves the durability of a polarizing plate by treating a polarizing film, which is a hydrophilic polymer film, with an acidic solution and providing a protective film with a layer obtained by curing a polymerizable resin composition. . However, although the above technique can improve the discoloration of the polarizing plate to some extent, it cannot prevent the deformation failure that is the subject of the present invention.

  Patent Document 2 discloses a coating film containing at least one organic component having a polymerizable functional group, inorganic ultrafine particles, and inorganic and / or organic fine particles having a primary particle size larger than the primary particle size of the inorganic ultrafine particles. A technique for preventing blocking of a hard coat film by a hard coat film formed from components is disclosed. However, if fine particles are added in order to sufficiently prevent blocking, haze is likely to increase, and there is still a problem in achieving both the prevention of deformation failure, which is the subject of the present invention, and visibility (clearness). It was.

JP 2008-70571 A JP 2001-13303 A

  The objective of this invention is providing the polarizing plate which aimed at coexistence suppression of generation | occurrence | production of the partial deformation | transformation failure under high-temperature, high-humidity conditions, and visibility (clearness), and a liquid crystal display device using the same. .

  The above object of the present invention is achieved by the following configurations.

1. In a polarizing plate in which a hard coat film having a hard coat layer on a protective film, a polarizing film and a base film is laminated in this order, the hard coat layer is a protrusion having a height of 3 nm or more from the average line of the roughness curve the has 500-200000 cells / mm ^2, the hard coat layer of the arithmetic average roughness Ra (JIS B0601: 2001) is 2 to 20 nm, and the haze value of the hard coat film (Hh) is 0.2 A polarizing plate characterized by being 0.6%.

  2. The difference (Hh−Hf) between the haze value (Hh) of the hard coat film and the haze value (Hf) of the base film of the hard coat film is 0.02% to 0.3%, 2. The polarizing plate according to 1 above.

  3. 3. The polarizing plate as described in 1 or 2 above, wherein the arithmetic average roughness Ra of the hard coat layer is 4 nm to 20 nm.

  4). The polarizing plate according to any one of 1 to 3, wherein the hard coat layer has a two-layer structure.

5. The base film of the hard coat film contains a thermoplastic acrylic resin and a cellulose ester resin having a weight average molecular weight (Mw) of 80000 to 500,000, and the mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is The polarizing plate according to any one of 1 to 4 above, wherein thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50.

  6). The protective film contains a thermoplastic acrylic resin and a cellulose ester resin, and the mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50. The polarizing plate according to any one of 1 to 5, wherein the polarizing plate is characterized in that

  7). 7. A liquid crystal display device comprising the polarizing plate according to any one of 1 to 6 in at least one of liquid crystal cells.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which aimed at coexistence suppression of generation | occurrence | production of the partial deformation | transformation failure under high temperature, high humidity conditions, and visibility (clearness), and a liquid crystal display device using the same can be provided. .

It is explanatory drawing of the protrusion concerning this invention. It is a schematic diagram of the polarizing plate which concerns on this invention. It is the schematic at the time of evaluating the durability test of a polarizing plate.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described in detail, but the present invention is not limited thereto.

  As a result of intensive studies on the above problems, the present inventor has provided a specific number of protrusions on the hard coat layer of the hard coat film to be bonded to the polarizing plate. By controlling the value, it is possible to disperse the stress applied to each polarizing plate when stored with the polarizing plates stacked, and partial deformation failure caused by the decrease in the elastic modulus of the polarizing plate due to storage under high temperature and high humidity conditions As a result, the present invention has been found. Moreover, since the hard coat film according to the present invention has a low haze value and clearness as a liquid crystal display device is not impaired, it is possible to achieve both suppression of partial deformation failure and visibility (clearness). .

  Hereinafter, each element will be described in detail.

<Number of protrusions, protrusion shape>
The hard coat layer according to the present invention is characterized by having 500 to 200,000 protrusions / mm ² , and the number of protrusions present is a value measured by the following method.

  The number of protrusions can also be measured from a hard coat layer disposed on the viewing side when used in a display device such as a liquid crystal display device.

  The number of protrusions was measured by measuring the hard coat layer with an optical interference surface roughness meter (RST / PLUS, manufactured by WYKO, magnification 50 times). Next, the number of protrusions in this measurement area (100 μm × 100 μm square) was read from the image. This series of measurements was performed 10 times, and the number of protrusions of the hard coat layer of the hard coat film was determined from the average value of 10 times.

  As the number of protrusions, protrusions having a height of 3 nm or more from the average line of the roughness curve were counted.

  The protrusion shape has a height of 1 nm to 5 μm, preferably 1 nm to 1 μm, preferably 10 nm to 0.5 μm. The width is 50 nm to 100 μm, preferably 50 nm to 50 μm.

  The width and height of the protrusion shape can be obtained from the following cross-sectional observation. FIG. 1 is an explanatory view of the protrusion.

  The cross-section of the hard coat film was cut in the film width direction at room temperature at an angle of 0 ° using a microtome (manufactured by Japan Microtome Laboratory). Next, this cross section was observed using a transmission electron microscope (TEM, magnification 2000 times). In accordance with the definition of JIS B 0601: 2001, the center line a is drawn on the image from the cross-sectional observed image, and the lines b and c forming the mountain ridge and the center line a are 2 The distance between the two intersections was defined as the protrusion size width t. Further, the distance from the summit to the center line a is obtained as the height h of the protrusion size.

  The arithmetic average roughness Ra specified in JIS B0601: 2001 of the hard coat layer according to the present invention is 2 to 20 nm, and more preferably 4 to 20 nm.

  By setting it as the said range, it is excellent in visibility (clearness), and also exhibits an excellent effect in suppressing the occurrence of partial deformation failure after the durability test.

  The arithmetic average roughness of the hard coat layer can be measured and analyzed using a commercially available surface roughness measuring instrument. In the present invention, it can be determined using a small surface roughness measuring instrument (model number; SJ-401, manufactured by Mitutoyo Corporation). Moreover, it can also measure with the optical interference type surface roughness measuring device, for example, can measure using non-contact surface fine shape measuring device WYKO NT-2000 by WYKO.

  As a method for forming the protrusion shape, a method for adding fine particles, a method for forming a protrusion on the surface by pressing a mold, and a method for forming surface irregularities by mixing resins having different SP values (solubility parameters) ( Examples thereof include the methods described in JP2007-182519 and JP2009-13384).

  As mold rolls used to form protrusions, those with fine irregularities and coarse ones can be selected and applied as appropriate, and patterns, mats, lenticular lenses, and spherical irregularities are regularly or randomly arranged. it can.

  In the present invention, although not particularly limited, a method of forming protrusions by adding fine particles is preferable from the viewpoint of productivity and reproducibility.

<Haze>
The haze value (Hh) of the hard coat film according to the present invention is 0.2 to 0.6%. When the haze value (Hh) of the hard coat film is set to 0.2 to 0.6%, the objective effect of the present invention is achieved, and when used outdoors such as an enlarged liquid crystal display device or digital signage. This is also preferable in that sufficient luminance and high contrast can be obtained. If the haze value (Hh) of the hard coat film is less than 0.2%, it is difficult to design from the viewpoint of the handleability of the hard coat film.

  Further, the effect of the present invention is that the difference (Hh−Hf) between the haze value (Hh) of the hard coat film and the haze value (Hf) of the base film is 0.02% to 0.3%. Is preferable in achieving the above.

  Controlling the haze value of the hard coat layer is achieved by adjusting the type and amount of resin, additives, etc. that make up the hard coat layer, and adjusting the type, particle size, and amount of added fine particles. Is done.

  Further, since the surface roughness also affects the haze value as the surface haze, it is effective to control the shape and number of the protrusions.

<Hard coat film>
The hard coat film according to the present invention is composed of at least a base film and a hard coat layer, and the hard coat layer contains an actinic radiation curable resin, and an actinic ray such as an ultraviolet ray or an electron beam (both active energy rays). It is preferably a layer mainly composed of a resin that cures through a crosslinking reaction upon irradiation.

  As the actinic radiation curable resin, a component containing a monomer having an ethylenically unsaturated double bond is preferably used, and an actinic radiation curable resin layer is formed by curing by irradiation with actinic radiation such as ultraviolet rays or electron beams. The

  Typical examples of the actinic radiation curable resin include an ultraviolet curable resin and an electron beam curable resin, but the resin that is cured by ultraviolet irradiation is excellent in mechanical film strength (abrasion resistance, pencil hardness). preferable.

  As the ultraviolet curable resin, for example, an ultraviolet curable urethane acrylate resin, an ultraviolet curable polyester acrylate resin, an ultraviolet curable epoxy acrylate resin, an ultraviolet curable polyol acrylate resin, or an ultraviolet curable epoxy resin is preferable. Used. Of these, ultraviolet curable acrylate resins are preferred.

  As the ultraviolet curable acrylate resin, a polyfunctional acrylate is preferable. The polyfunctional acrylate is preferably selected from the group consisting of pentaerythritol polyfunctional acrylate, dipentaerythritol polyfunctional acrylate, pentaerythritol polyfunctional methacrylate, and dipentaerythritol polyfunctional methacrylate. Here, the polyfunctional acrylate is a compound having two or more acryloyloxy groups or methacryloyloxy groups in the molecule.

  Examples of the polyfunctional acrylate monomer include ethylene glycol diacrylate, diethylene glycol diacrylate, 1,6-hexanediol diacrylate, neopentyl glycol diacrylate, trimethylolpropane triacrylate, trimethylolethane triacrylate, and tetramethylolmethane triacrylate. , Tetramethylolmethane tetraacrylate, pentaglycerol triacrylate, pentaerythritol diacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, glycerin triacrylate, dipentaerythritol triacrylate, dipentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, dipentaerythritol Lithol hexaacrylate, tris (acryloyloxyethyl) isocyanurate, ethylene glycol dimethacrylate, diethylene glycol dimethacrylate, 1,6-hexanediol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, trimethylolethane trimethacrylate, Tetramethylol methane trimethacrylate, tetramethylol methane tetramethacrylate, pentaglycerol trimethacrylate, pentaerythritol dimethacrylate, pentaerythritol trimethacrylate, pentaerythritol tetramethacrylate, glycerol trimethacrylate, dipentaerythritol trimethacrylate, dipentaerythritol tetramethacrylate Acrylate, dipentaerythritol penta methacrylate, dipentaerythritol hexa methacrylate, isobornyl acrylate and the like preferably. These compounds are used alone or in admixture of two or more. Moreover, oligomers, such as a dimer and a trimer of the said monomer, may be sufficient.

  The hard coat layer preferably contains a photopolymerization initiator to accelerate the curing of the actinic radiation curable resin. The amount of the photopolymerization initiator is preferably contained in a mass ratio of photopolymerization initiator: active ray curable resin = 20: 100 to 0.01: 100.

  Specific examples of the photopolymerization initiator include acetophenone, benzophenone, hydroxybenzophenone, Michler's ketone, α-amyloxime ester, thioxanthone, and derivatives thereof, but are not particularly limited thereto.

The hard coat layer according to the present invention preferably contains fine particles of an inorganic compound or an organic compound so as to have 500 to 200,000 protrusions / mm ² and an arithmetic average roughness Ra of 2 to 20 nm.

  As inorganic fine particles, silicon oxide, titanium oxide, aluminum oxide, tin oxide, indium oxide, ITO, zinc oxide, zirconium oxide, magnesium oxide, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, hydrated silicic acid Mention may be made of calcium, aluminum silicate, magnesium silicate and calcium phosphate. In particular, silicon oxide, titanium oxide, aluminum oxide, zirconium oxide, magnesium oxide and the like are preferably used.

  These inorganic fine particles are preferably coated with an organic component having a reactive functional group on a part of the surface because the scratch resistance is improved while maintaining the transparency of the hard coat film. As a method for coating an organic component having a reactive functional group on a part of the surface, for example, a compound containing an organic component such as a silane coupling agent reacts with a hydroxyl group present on the surface of the metal oxide fine particles, and the surface A mode in which an organic component is bonded to a part of the metal particle, a mode in which an organic component is attached to a hydroxyl group present on the surface of a metal oxide fine particle by an interaction such as a hydrogen bond, or one or more inorganic particles in a polymer particle The aspect containing microparticles | fine-particles etc. are mentioned.

  Organic particles include polymethacrylic acid methyl acrylate resin powder, acrylic styrene resin powder, polymethyl methacrylate resin powder, silicon resin powder, polystyrene resin powder, polycarbonate resin powder, benzoguanamine resin powder, and melamine resin. Powder, polyolefin resin powder, polyester resin powder, polyamide resin powder, polyimide resin powder, polyfluoroethylene resin powder, or the like can be added.

  Preferred fine particles include crosslinked polystyrene particles (for example, SX-130H, SX-200H, SX-350H manufactured by Soken Chemical), polymethyl methacrylate-based particles (for example, MX150, MX300 manufactured by Soken Chemical), and fluorine-containing acrylic resin fine particles. . Examples of the fluorine-containing acrylic resin fine particles include commercial products such as FS-701 manufactured by Nippon Paint. Examples of the acrylic particles include Nippon Paint: S-4000, and examples of the acrylic-styrene particles include Nippon Paint: S-1200, MG-251.

  The average particle size of these fine particle powders is not particularly limited, but is preferably 0.01 to 5 μm, and more preferably 0.01 to 1.0 μm. Moreover, you may contain 2 or more types of microparticles | fine-particles from which a particle size differs. The average particle diameter of the fine particles can be measured by, for example, a laser diffraction particle size distribution measuring device.

  The ratio of the ultraviolet curable resin composition and the fine particles is desirably 10 to 400 parts by mass, more preferably 50 to 200 parts by mass with respect to 100 parts by mass of the resin composition.

  These hard coat layers are coated using a known method such as a gravure coater, dip coater, reverse coater, wire bar coater, die coater, ink jet method, and the like. And can be formed by UV curing.

  The coating amount is suitably 0.1 to 40 μm, preferably 0.5 to 30 μm, as the wet film thickness. The dry film thickness is from 0.1 to 30 μm, preferably from 1 to 20 μm, particularly preferably from 6 to 15 μm.

  As a light source for UV curing treatment, any light source that generates ultraviolet rays can be used without limitation. For example, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultrahigh pressure mercury lamp, a carbon arc lamp, a metal halide lamp, a xenon lamp, or the like can be used.

Irradiation conditions vary depending on each lamp, but the irradiation amount of active rays is usually 5 to 500 mJ / cm ² , preferably 5 to 200 mJ / cm ² .

  Moreover, when irradiating actinic radiation, it is preferable to carry out while applying tension | tensile_strength in the conveyance direction of a film, More preferably, it is performing applying tension | tensile_strength also in the width direction. The tension to be applied is preferably 30 to 300 N / m. The method for applying tension is not particularly limited, and tension may be applied in the transport direction on the back roll, or tension may be applied in the width direction or biaxial direction by a tenter. Thereby, a film having further excellent flatness can be obtained.

  Furthermore, the hard coat layer according to the present invention may contain a conductive agent in order to impart antistatic properties, and preferred conductive agents include metal oxide particles or π-conjugated conductive polymers. An ionic liquid is also preferably used as the conductive compound.

  In addition, the hard coat layer has a nonionic surfactant such as a silicone surfactant, a fluorosurfactant or a polyoxyether, an anion, from the viewpoint of coatability and uniform dispersibility of fine particles. A surfactant or the like can also be contained. These enhance the applicability. Moreover, it is preferable to add these components in 0.01-3 mass% with respect to the solid content component in a coating liquid.

  FIG. 2 shows a schematic diagram of a hard coat film having a hard coat layer according to the present invention and a polarizing plate. In FIG. 2, two layers such as the hard coat layers 2a and 2b are laminated, but may be one layer or a plurality of layers. Provided in two or more layers in order to better demonstrate the object effects of the present invention and to make it easier to control the hard coat properties, haze, protrusion shape formed on the surface, and arithmetic surface roughness Ra of the hard coat layer. It is preferable.

  The thickness of the uppermost layer when two or more layers are provided is preferably in the range of 0.05 to 2 μm.

  Two or more layers may be formed as a simultaneous multilayer. The simultaneous multi-layer is to form a hard coat layer by applying two or more hard coat layers on a base material without going through a drying step. In order to laminate the second hard coat layer on the first hard coat layer without a drying process, the layers are stacked one after another by an extrusion coater or simultaneously by a slot die having a plurality of slits. Can be done.

  The hard coat film in the present invention has a pencil hardness, which is an index of hardness, of H or higher, more preferably 3H or higher. If it is 3H or more, it is not only difficult to be scratched in the polarizing plate forming step of the liquid crystal display device, but also used for outdoor applications, and is a surface protective film for large liquid crystal display devices and liquid crystal display devices for digital signage. When used as an excellent film strength. The pencil hardness is evaluated by pencil hardness evaluation specified by JIS K5400 using a test pencil specified by JIS S 6006 after the prepared hard coat film is conditioned at a temperature of 23 ° C. and a relative humidity of 55% for 2 hours or more. It is the value measured according to the method.

<Base film>
It is preferable that the base film is easy to manufacture, easily adheres to the hard coat layer, and is optically isotropic. Moreover, a base film can also be used as a protective film according to the present invention as it is.

  Any of these may be used, for example, cellulose ester films such as triacetyl cellulose film, cellulose acetate propionate film, cellulose diacetate film, cellulose acetate butyrate film, polyethylene terephthalate, polyethylene naphthalate Polyester film, polycarbonate film, polyarylate film, polysulfone (including polyethersulfone) film, polyethylene film, polypropylene film, cellophane, polyvinylidene chloride film, polyvinyl alcohol film, ethylene vinyl alcohol film, syndiotactic Tick polystyrene film, norbornene resin film, polymethylpentene film, Li ether ketone film, polyether ketone imide film, a polyamide film, a fluororesin film, a nylon film, cycloolefin polymer films, and polymethyl methacrylate film or an acrylic film or the like.

  Among these, cellulose ester films (for example, Konica Minoltak KC8UX, KC4UX, KC5UX, KC8UCR3, KC8UCR4, KC8UCR5, KC8UY, KC4UE, KC4UE, and KC12UR (above, Konica Minolta Opto Co., Ltd., Polycarbonate Film) Olefin polymer films and polyester films are preferred, and in the present invention, the cellulose ester film is particularly advantageous in terms of production, cost, isotropy, adhesiveness (saponification suitability), and the object effects of the present invention. preferable.

  The refractive index of the base film according to the present invention is preferably 1.30 to 1.70, and more preferably 1.40 to 1.65. The refractive index is measured by the method of JIS K7142 using an Atpe refractometer 2T.

<Cellulose ester film>
Next, a cellulose ester film preferable as a substrate film will be described.

  The cellulose ester resin (hereinafter also referred to as cellulose ester) is preferably a lower fatty acid ester of cellulose. The lower fatty acid in the lower fatty acid ester of cellulose means a fatty acid having 6 or less carbon atoms. For example, cellulose acetate, cellulose propionate, cellulose butyrate and the like, and JP-A Nos. 10-45804 and 08-231761 , Mixed fatty acid esters such as cellulose acetate propionate and cellulose acetate butyrate as described in US Pat. No. 2,319,052 can be used.

  Among the above descriptions, the lower fatty acid esters of cellulose particularly preferably used are cellulose triacetate and cellulose acetate propionate. These cellulose esters can be used alone or in combination.

  In the case of cellulose triacetate, those having an average degree of acetylation (bound acetic acid amount) of 54.0 to 62.5% are preferably used, and more preferably an average degree of acetylation of 58.0 to 62.5%. Cellulose triacetate.

  When the average degree of acetylation is small, the dimensional change is large, and the polarization degree of the polarizing plate is lowered. When the average degree of acetylation is large, the solubility in a solvent is lowered and the productivity is lowered.

  Preferred cellulose esters other than cellulose triacetate have an acyl group having 2 to 4 carbon atoms as a substituent, and when the substitution degree of acetyl group is X and the substitution degree of propionyl group or butyryl group is Y, the following formula ( It is a cellulose ester including a cellulose ester that simultaneously satisfies I) and (II).

Formula (I) 2.6 ≦ X + Y ≦ 3.0
Formula (II) 0 ≦ X ≦ 2.5
Of these, cellulose acetate propionate is preferably used, and it is particularly preferable that 1.9 ≦ X ≦ 2.5 and 0.1 ≦ Y ≦ 0.9. The portion that is not substituted with an acyl group usually exists as a hydroxyl group. These can be synthesized by known methods. The measuring method of the substitution degree of an acyl group can be measured according to ASTM-D817-96.

  The molecular weight of the cellulose ester is preferably a number average molecular weight (Mn) of 60,000 to 300,000, more preferably 70,000 to 200,000, particularly preferably 100,000 to 200,000. The cellulose ester used in the present invention preferably has a weight average molecular weight (Mw) / number average molecular weight (Mn) ratio of 4.0 or less, more preferably 1.4 to 2.3.

  Since the average molecular weight and molecular weight distribution of the cellulose ester can be measured using high performance liquid chromatography, the number average molecular weight (Mn) and the weight average molecular weight (Mw) can be calculated using this, and the ratio can be calculated.

  The measurement conditions are as follows.

Solvent: Methylene chloride Column: Shodex K806, K805, K803G (Used by connecting three Showa Denko Co., Ltd.)
Column temperature: 25 ° C
Sample concentration: 0.1% by mass
Detector: RI Model 504 (GL Science Co., Ltd.)
Pump: L6000 (manufactured by Hitachi, Ltd.)
Flow rate: 1.0 ml / min
Calibration curve: Standard polystyrene STK standard polystyrene (manufactured by Tosoh Corporation)
A calibration curve with 13 samples from Mw = 100000 to 500 was used. The 13 samples are preferably used at approximately equal intervals.

<Cellulose ester resin / thermoplastic acrylic resin-containing film>
The base film according to the present invention contains a thermoplastic acrylic resin and a cellulose ester resin from the viewpoint of exerting the objective effects of the present invention even in a more severe durability test, and includes a thermoplastic acrylic resin and a cellulose ester resin. It is preferable to use a base film (hereinafter referred to as a cellulose ester resin / thermoplastic acrylic resin film) having a composition of a mass ratio of thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50. More preferably, it is 90: 10-60: 40.

  The thermoplastic acrylic resin includes a methacrylic resin. Although it does not restrict | limit especially as a thermoplastic acrylic resin, What consists of 50-99 mass% of methyl methacrylate units and 1-50 mass% of other monomer units copolymerizable with this is preferable. Other monomers that can be copolymerized include alkyl methacrylates having 2 to 18 carbon atoms, alkyl acrylates having 1 to 18 carbon atoms, acrylic acid, methacrylic acid, and the like. Unsaturated group-containing divalent carboxylic acids such as saturated acid, maleic acid, fumaric acid and itaconic acid, aromatic vinyl compounds such as styrene and α-methylstyrene, α, β-unsaturated nitriles such as acrylonitrile and methacrylonitrile, Maleic anhydride, maleimide, N-substituted maleimide, glutaric anhydride and the like can be mentioned, and these can be used alone or in combination of two or more monomers.

  Among these, methyl acrylate, ethyl acrylate, n-propyl acrylate, n-butyl acrylate, s-butyl acrylate, 2-ethylhexyl acrylate, and the like are preferable from the viewpoint of thermal decomposition resistance and fluidity of the copolymer. n-Butyl acrylate is particularly preferably used. Moreover, it is preferable that a weight average molecular weight (Mw) is 80000-500000, More preferably, it exists in the range of 110000-500000. The weight average molecular weight of the thermoplastic acrylic resin can be measured by the gel permeation chromatography described above, including the measurement conditions. There is no restriction | limiting in particular as a manufacturing method of a thermoplastic acrylic resin, You may use any well-known methods, such as suspension polymerization, emulsion polymerization, block polymerization, or solution polymerization. Here, as a polymerization initiator, a normal peroxide type and an azo type can be used, and a redox type can also be used. Regarding the polymerization temperature, suspension or emulsion polymerization may be performed at 30 to 100 ° C, and bulk or solution polymerization may be performed at 80 to 160 ° C. In order to control the reduced viscosity of the obtained copolymer, polymerization can be carried out using alkyl mercaptan or the like as a chain transfer agent. Commercial products can also be used. For example, Delpet 60N, 80N (Asahi Kasei Chemicals Co., Ltd.), Dianal BR52, BR80, BR83, BR85, BR88 (Mitsubishi Rayon Co., Ltd.), KT75 (Electrochemical Industry Co., Ltd.) and the like can be mentioned. . Two or more thermoplastic acrylic resins can be used in combination. As the thermoplastic acrylic resin, a graft copolymer obtained by grafting a (meth) acrylic resin to a copolymer of (meth) acrylic rubber and an aromatic vinyl compound described in JP-A-2009-84574 is used. May be. In the graft copolymer, a copolymer of (meth) acrylic rubber and an aromatic vinyl compound forms a core, and the (meth) acrylic resin forms a shell around the copolymer. -It is preferably a shell-type graft copolymer.

  The total mass of the thermoplastic acrylic resin and the cellulose ester resin in the base film is preferably 55% by mass or more of the base film, more preferably 60% by mass or more, and particularly preferably 70% by mass or more. is there.

  The base film may be configured to contain resins and additives other than thermoplastic acrylic resins and cellulose ester resins.

<Acrylic particles>
The base film preferably contains acrylic particles from the viewpoint of improving brittleness and obtaining excellent pencil hardness.

  An acrylic particle represents the acrylic component which exists in the state of particle | grains (it is also called an incompatible state) in the base film containing the said thermoplastic acrylic resin and cellulose-ester resin in a compatible state.

  The acrylic particles are not particularly limited, but are preferably acrylic particles having a layer structure of two or more layers, and particularly preferably a multilayer structure acrylic granular composite.

  Examples of commercially available acrylic granular composites that are multi-layer structured polymers include, for example, “Metablene” manufactured by Mitsubishi Rayon Co., “Kaneace” manufactured by Kaneka Chemical Co., Ltd., “Paralloid” manufactured by Kureha Chemical Co., Ltd., Rohm and “Acryloid” manufactured by Haas, “Staffyroid” manufactured by Ganz Kasei Kogyo Co., Ltd., “Parapet SA” manufactured by Kuraray Co., Ltd., and the like can be used.

  In addition, specific examples of acrylic particles that are graft copolymers suitably used as acrylic particles include unsaturated carboxylic acid ester monomers, unsaturated carboxylic acid monomers in the presence of rubbery polymers. And a graft copolymer obtained by copolymerizing a mixture of a monomer, an aromatic vinyl monomer, and, if necessary, a monomer composed of other vinyl monomers copolymerizable therewith.

  There is no particular limitation on the rubbery polymer used for the acrylic particles as the graft copolymer, but diene rubber, acrylic rubber, ethylene rubber, and the like can be used. Specific examples include polybutadiene, styrene-butadiene copolymer, block copolymer of styrene-butadiene, acrylonitrile-butadiene copolymer, butyl acrylate-butadiene copolymer, polyisoprene, butadiene-methyl methacrylate copolymer, Butyl acrylate-methyl methacrylate copolymer, butadiene-ethyl acrylate copolymer, ethylene-propylene copolymer, ethylene-propylene-diene copolymer, ethylene-isoprene copolymer, and ethylene-methyl acrylate copolymer A polymer etc. are mentioned. These rubbery polymers can be used alone or in a mixture of two or more.

  Moreover, when adding an acrylic particle to a base film, it is preferable at the point which obtains a film with high transparency that the refractive index of the mixture of a thermoplastic acrylic resin and a cellulose-ester resin and the refractive index of an acrylic particle are near. Specifically, the refractive index difference between the acrylic particles and the thermoplastic acrylic resin is preferably 0.05 or less, more preferably 0.02 or less, and particularly preferably 0.01 or less.

  The method for blending the acrylic particles with the thermoplastic acrylic resin is not particularly limited, and after blending the thermoplastic acrylic resin and other optional components in advance, usually at 200 to 350 ° C. while adding the acrylic particles, uniaxial or A method of uniformly melt-kneading with a twin-screw extruder is preferably used.

  In addition, a solution in which acrylic particles are dispersed in advance is added to and mixed with a solution (dope solution) in which a thermoplastic acrylic resin and a cellulose ester resin are dissolved, and acrylic particles and other optional additives are dissolved and mixed. A method such as in-line addition of the prepared solution can be used.

  A commercially available thing can also be used as an acrylic particle. For example, metabrene W-341 (C2) (manufactured by Mitsubishi Rayon Co., Ltd.), Chemisnow MR-2G (C3), MS-300X (C4) (manufactured by Soken Chemical Co., Ltd.) and the like can be mentioned.

  Acrylic fine particles are acrylic fine particles: thermoplastic acrylic resin and cellulose ester resin total mass = 0.5: 100 to 30: with respect to the total mass of the thermoplastic acrylic resin and cellulose ester resin constituting the film. By containing in 100 range, it is preferable from the point by which the target effect is exhibited more preferable, More preferably, the total mass of acrylic fine particles: thermoplastic acrylic resin and cellulose ester resin = 1.0: 100 to 15: 100 It is a range.

<Other additives>
In order to improve the fluidity and flexibility of the composition, a plasticizer can be used in combination with the base film. Examples of the plasticizer include phthalate ester, fatty acid ester, trimellitic ester, phosphate ester, polyester, and epoxy. Of these, polyester and phthalate plasticizers are preferably used. Polyester plasticizers are superior in non-migration and extraction resistance compared to phthalate ester plasticizers such as dioctyl phthalate, but are slightly inferior in plasticizing effect and compatibility.

  Therefore, it can be applied to a wide range of uses by selecting or using these plasticizers according to the use.

  The polyester plasticizer is a reaction product of a monovalent or tetravalent carboxylic acid and a monovalent or hexavalent alcohol, and is mainly obtained by reacting a divalent carboxylic acid with a glycol. . Representative divalent carboxylic acids include glutaric acid, itaconic acid, adipic acid, phthalic acid, azelaic acid, sebacic acid and the like.

  In particular, when adipic acid, phthalic acid or the like is used, those having excellent plasticizing properties can be obtained. Examples of the glycol include glycols such as ethylene, propylene, 1,3-butylene, 1,4-butylene, 1,6-hexamethylene, neopentylene, diethylene, triethylene, and dipropylene. These divalent carboxylic acids and glycols may be used alone or in combination.

  The ester plasticizer may be any of ester, oligoester, and polyester types, and the molecular weight is preferably in the range of 100 to 10,000, and preferably in the range of 600 to 3000, which has a large plasticizing effect.

  The viscosity of the plasticizer has a correlation with the molecular structure and molecular weight. In the case of an adipic acid plasticizer, the viscosity is preferably in the range of 200 to 5000 MPa · s (25 ° C.) in view of compatibility and plasticization efficiency. Furthermore, some polyester plasticizers may be used in combination.

  The plasticizer is preferably added in an amount of 0.5 to 30 parts by mass with respect to 100 parts by mass of the base film. If the added amount of the plasticizer exceeds 30 parts by mass, the surface becomes sticky, which is not preferable for practical use.

  The base film preferably also contains an ultraviolet absorber, and examples of the ultraviolet absorber used include benzotriazole-based, 2-hydroxybenzophenone-based or salicylic acid phenyl ester-based ones. For example, 2- (5-methyl-2-hydroxyphenyl) benzotriazole, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2H-benzotriazole, 2- (3 Triazoles such as 5-di-t-butyl-2-hydroxyphenyl) benzotriazole, 2-hydroxy-4-methoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone And benzophenones. Here, among ultraviolet absorbers, ultraviolet absorbers having a molecular weight of 400 or more are less likely to volatilize at a high boiling point and are difficult to disperse even during high-temperature molding, so that the weather resistance is effectively improved with a relatively small amount of addition. be able to.

  Examples of the ultraviolet absorber having a molecular weight of 400 or more include 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole, 2,2-methylenebis [4- (1, 1,3,3-tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol], bis (2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis ( Hindered amines such as 1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and 2- (3,5-di-t-butyl-4-hydroxybenzyl) -2-n-butylmalonic acid Bis (1,2,2,6,6-pentamethyl-4-piperidyl), 1- [2- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] ethyl L] -4- [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionyloxy] -2,2,6,6-tetramethylpiperidine and the like, hindered phenol and hindered amine A hybrid system having both structures can be mentioned, and these can be used alone or in combination of two or more. Among these, 2- [2-hydroxy-3,5-bis (α, α-dimethylbenzyl) phenyl] -2-benzotriazole and 2,2-methylenebis [4- (1,1,3,3- Tetrabutyl) -6- (2H-benzotriazol-2-yl) phenol] is particularly preferred.

  Furthermore, various antioxidants can also be added to the base film in order to improve the thermal decomposability and thermal colorability during molding. It is also possible to add an antistatic agent to give the optical film antistatic performance.

  A flame retardant acrylic resin composition containing a phosphorus flame retardant may be used for the base film.

  Phosphorus flame retardants used here include red phosphorus, triaryl phosphate ester, diaryl phosphate ester, monoaryl phosphate ester, aryl phosphonate compound, aryl phosphine oxide compound, condensed aryl phosphate ester, halogenated alkyl phosphorus. Examples thereof include one or a mixture of two or more selected from acid esters, halogen-containing condensed phosphates, halogen-containing condensed phosphonates, halogen-containing phosphites, and the like.

  Specific examples include triphenyl phosphate, 9,10-dihydro-9-oxa-10-phosphaphenanthrene-10-oxide, phenylphosphonic acid, tris (β-chloroethyl) phosphate, tris (dichloropropyl). Examples thereof include phosphate and tris (tribromoneopentyl) phosphate.

  The base film according to the present invention is preferably a “film that does not cause ductile fracture”. Here, the ductile fracture is a fracture caused by applying a stress larger than the strength of a certain material, and is defined as a fracture accompanied by significant elongation or drawing of the material until the final fracture. The fracture surface is characterized by numerous indentations called dimples.

  Whether or not the film is “a film in which ductile fracture does not occur” is evaluated based on the fact that breakage such as breakage is not observed even when a large stress is applied to bend the film in two.

  In addition to the increase in the size of liquid crystal display devices and the increasing brightness of backlight light sources, the use of digital signage and other outdoor applications demands higher brightness. The base film according to the present invention is required to withstand use in a high-temperature environment, and if the tension softening point is 105 ° C to 145 ° C, it can be determined that it exhibits sufficient heat resistance. In particular, it is preferable to control at 110 to 130 ° C.

  As a specific method of measuring the tension softening point, for example, using a Tensilon tester (ORIENTEC, RTC-1225A), the optical film is cut out at 120 mm (length) × 10 mm (width) and pulled with a tension of 10 N. However, the temperature can be continuously increased at a temperature increase rate of 30 ° C./min, and the temperature at 9 N can be measured three times, and the average value can be obtained.

  From the viewpoint of heat resistance, the substrate film preferably has a glass transition temperature (Tg) of 110 ° C. or higher. More preferably, it is 120 ° C. or higher. Especially preferably, it is 150 degreeC or more.

  The glass transition temperature referred to here is an intermediate value determined according to JIS K7121 (1987) using a differential scanning calorimeter (DSC-7 model manufactured by Perkin Elmer) at a temperature rising rate of 20 ° C./min. Point glass transition temperature (Tmg).

  In addition, when a base film is used as a protective film for a polarizing plate of a liquid crystal display device, unevenness or a change in retardation value occurs due to a dimensional change due to moisture absorption, causing problems such as a decrease in contrast and uneven color. . In particular, the above problem becomes significant when the polarizing plate protective film is used in a liquid crystal display device used outdoors. For this reason, the dimensional change rate (%) is preferably less than 0.5%, and more preferably less than 0.3%.

  Moreover, it is preferable that the base film has a defect of 5 μm or more in diameter in the film plane of 1 piece / 10 cm square or less. More preferably, it is 0.5 piece / 10 cm square or less, more preferably 0.1 piece / 10 cm square or less.

  Here, the diameter of the defect indicates the diameter when the defect is circular, and when the defect is not circular, the range of the defect is determined by observing with a microscope by the following method, and the maximum diameter (diameter of circumscribed circle) is determined.

  The range of the defect is the size of the shadow when the defect is observed with the transmitted light of the differential interference microscope when the defect is a bubble or a foreign object. When the defect is a change in the surface shape, such as transfer of a roll flaw or an abrasion, the size is confirmed by observing the defect with the reflected light of a differential interference microscope.

  In addition, when observing with reflected light, if the size of the defect is unclear, aluminum or platinum is deposited on the surface for observation.

  In order to obtain a film having excellent quality expressed by such a defect frequency with high productivity, it is necessary to filter the polymer solution with high precision immediately before casting, to increase the cleanliness around the casting machine, It is effective to set drying conditions after rolling stepwise and to dry efficiently while suppressing foaming.

  When the number of defects is greater than 1/10 cm square, for example, when the film is tensioned during processing in a later process, the film may break with the defects as a starting point, and productivity may decrease. Moreover, when the diameter of a defect becomes 5 micrometers or more, it can confirm visually by polarizing plate observation etc., and when used as an optical member, a bright spot may arise.

  Moreover, even when it cannot be visually confirmed, when a hard coat layer or the like is formed on the film, the coating agent may not be formed uniformly, resulting in a defect (missing coating). Here, the defect is a void in the film (foaming defect) generated due to the rapid evaporation of the solvent in the drying process of the solution casting, a foreign matter in the film forming stock solution, or a foreign matter mixed in the film forming. This refers to the foreign matter (foreign matter defect) in the film.

  In addition, the base film preferably has a breaking elongation of at least one direction of 10% or more, more preferably 20% or more, in the measurement based on JIS-K7127-1999.

  The upper limit of the elongation at break is not particularly limited, but is practically about 250%. In order to increase the elongation at break, it is effective to suppress defects in the film caused by foreign matter and foaming.

  The thickness of the base film is preferably 20 μm or more. More preferably, it is 30 μm or more.

  The upper limit of the thickness is not particularly limited, but in the case of forming a film by a solution casting method, the upper limit is about 250 μm from the viewpoint of applicability, foaming, solvent drying, and the like. The thickness of the film can be appropriately selected depending on the application.

  The base film preferably has a total light transmittance of 90% or more, more preferably 93% or more. Moreover, as a realistic upper limit, it is about 99%. In order to achieve excellent transparency expressed by such total light transmittance, it is necessary not to introduce additives and copolymerization components that absorb visible light, or to remove foreign substances in the polymer by high-precision filtration. It is effective to reduce the diffusion and absorption of light inside the film.

  Also, reduce the surface roughness of the film surface by reducing the surface roughness of the film contact part (cooling roll, calender roll, drum, belt, coating substrate in solution casting, transport roll, etc.) during film formation. It is also effective to reduce the diffusion and reflection of light on the film surface by reducing the refractive index of the thermoplastic acrylic resin.

<Formation of base film>
Although the example of the film forming method of a base film is demonstrated, this invention is not limited to this. As a method for forming the base film, a production method such as an inflation method, a T-die method, a calendar method, a cutting method, a casting method, an emulsion method, or a hot press method can be used.

  From the viewpoint of suppressing residual solvent using a cellulose ester resin or a thermoplastic acrylic resin for dissolution, a method of producing by a melt casting film forming method is preferable. Methods formed by melt casting can be classified into melt extrusion molding methods, press molding methods, inflation methods, injection molding methods, blow molding methods, stretch molding methods, and the like. Among these, the melt extrusion method is preferable, in which a film having excellent mechanical strength and surface accuracy can be obtained. From the viewpoints of suppressing coloring, suppressing defects of foreign matters, and suppressing optical defects such as die lines, solution casting by casting is preferred.

  In the present invention, a method of extruding a film forming material onto a drum or an endless belt after the film forming material is heated to develop its fluidity is also included as a melt casting film forming method.

(Organic solvent)
The organic solvent useful for forming the dope when the base film is produced by the solution casting method is not limited as long as it can dissolve thermoplastic acrylic resin, cellulose ester resin, and other additives at the same time. I can do it.

  For example, as the chlorinated organic solvent, methylene chloride, as the non-chlorinated organic solvent, methyl acetate, ethyl acetate, amyl acetate, acetone, tetrahydrofuran, 1,3-dioxolane, 1,4-dioxane, cyclohexanone, ethyl formate, 2,2,2-trifluoroethanol, 2,2,3,3-hexafluoro-1-propanol, 1,3-difluoro-2-propanol, 1,1,1,3,3,3-hexafluoro- Examples include 2-methyl-2-propanol, 1,1,1,3,3,3-hexafluoro-2-propanol, 2,2,3,3,3-pentafluoro-1-propanol, and nitroethane. Methylene chloride, methyl acetate, ethyl acetate and acetone can be preferably used.

  In addition to the organic solvent, the dope preferably contains 1 to 40% by mass of a linear or branched aliphatic alcohol having 1 to 4 carbon atoms. When the proportion of alcohol in the dope increases, the web gels and peeling from the metal support becomes easy. When the proportion of alcohol is small, thermoplastic acrylic resins and cellulose ester resins in non-chlorine organic solvent systems There is also a role of promoting dissolution of the.

  In particular, in a solvent containing methylene chloride and a linear or branched aliphatic alcohol having 1 to 4 carbon atoms, at least 15 kinds of thermoplastic acrylic resin, cellulose ester resin, and acrylic particles are used. A dope composition in which 45% by mass is dissolved is preferable.

  Examples of the linear or branched aliphatic alcohol having 1 to 4 carbon atoms include methanol, ethanol, n-propanol, iso-propanol, n-butanol, sec-butanol, and tert-butanol. Ethanol is preferred because of the stability of these dopes, the relatively low boiling point, and good drying properties.

(Solution casting method)
Cellulose ester film and cellulose ester resin / thermoplastic acrylic resin film are prepared by solution casting, and a dope is prepared by dissolving cellulose ester or cellulose ester resin / thermoplastic acrylic resin and additives in a solvent. , A step of casting the dope on a belt-shaped or drum-shaped metal support, a step of drying the cast dope as a web, a step of peeling from the metal support, a step of stretching or maintaining the width, and a step of further drying. It is performed by a process of winding up the finished film.

  The concentration of the cellulose ester in the dope, and the concentration of the cellulose ester resin / thermoplastic acrylic resin is preferably higher because the drying load after casting on the metal support can be reduced, but the concentration of the cellulose ester is too high. The load at the time of filtration increases, resulting in poor filtration accuracy. As a density | concentration which makes these compatible, 10-35 mass% is preferable, More preferably, it is 15-25 mass%.

  The metal support in the casting (casting) step preferably has a mirror-finished surface, and a stainless steel belt or a drum whose surface is plated with a casting is preferably used as the metal support.

  The cast width can be 1 to 4 m. The surface temperature of the metal support in the casting step is set to −50 ° C. to a temperature at which the solvent boils and does not foam. A higher temperature is preferred because the web can be dried faster, but if it is too high, the web may foam or the flatness may deteriorate.

  The preferable support temperature is appropriately determined at 0 to 100 ° C, and more preferably 5 to 30 ° C. Alternatively, it is also a preferable method that the web is gelled by cooling and peeled from the drum in a state containing a large amount of residual solvent.

  The method for controlling the temperature of the metal support is not particularly limited, and there are a method of blowing hot air or cold air, and a method of contacting hot water with the back side of the metal support. It is preferable to use warm water because heat transfer is performed efficiently, so that the time until the temperature of the metal support becomes constant is short.

  When using warm air, considering the temperature drop of the web due to the latent heat of vaporization of the solvent, while using warm air above the boiling point of the solvent, there may be cases where wind at a temperature higher than the target temperature is used while preventing foaming. .

  In particular, it is preferable to perform drying efficiently by changing the temperature of the support and the temperature of the drying air during the period from casting to peeling.

  In order for the cellulose ester film to exhibit good flatness, the residual solvent amount when peeling the web from the metal support is preferably 10 to 150% by mass, more preferably 20 to 40% by mass or 60 to 130% by mass. Especially preferably, it is 20-30 mass% or 70-120 mass%.

  The amount of residual solvent is defined by the following formula.

Residual solvent amount (% by mass) = {(MN) / N} × 100
Note that M is the mass of a sample collected during or after the production of the web or film, and N is the mass after heating M at 115 ° C. for 1 hour.

  In the drying step of the cellulose ester film or the cellulose ester resin / thermoplastic acrylic resin film, the web is preferably peeled off from the metal support and further dried to make the residual solvent amount 1% by mass or less. Is 0.1% by mass or less, particularly preferably 0 to 0.01% by mass.

  In the film drying process, generally, a roll drying method (a method in which a plurality of rolls arranged on the upper and lower sides are alternately passed through and dried) or a method of drying while transporting the web by a tenter method is adopted.

(Melting method)
The cellulose ester film and the cellulose ester resin / thermoplastic acrylic resin film are also preferably formed by a melt film forming method. In the melt film forming method, a composition containing cellulose ester and an additive such as a cellulose ester resin / thermoplastic acrylic resin and a plasticizer is heated and melted to a temperature showing fluidity, and then contains a fluid cellulose ester. It refers to casting a melt.

  More specifically, the heat melting molding method can be classified into a melt extrusion molding method, a press molding method, an inflation method, an injection molding method, a blow molding method, a stretch molding method, and the like.

  Among these, in order to obtain a cellulose ester film excellent in mechanical strength and surface accuracy, and a cellulose ester resin / thermoplastic acrylic resin film, the melt extrusion method is excellent.

  It is preferable that a plurality of raw materials used for melt extrusion are usually kneaded in advance and pelletized.

  Pelletization may be performed by a known method. For example, dry cellulose ester, plasticizer, and other additives are fed to an extruder with a feeder and kneaded using a single-screw or twin-screw extruder, and formed into a strand from a die. It can be done by extrusion, water cooling or air cooling and cutting.

  The additives may be mixed before being supplied to the extruder, or may be supplied by individual feeders.

  A small amount of additives such as particles and antioxidants are preferably mixed in advance in order to mix uniformly.

  The extruder is preferably processed at as low a temperature as possible so as to be able to be pelletized so that the shear force is suppressed and the resin does not deteriorate (decrease in molecular weight, coloring, gel formation, etc.). For example, in the case of a twin screw extruder, it is preferable to rotate in the same direction using a deep groove type screw. From the uniformity of kneading, the meshing type is preferable.

  A film is formed using the pellets obtained as described above. Of course, the raw material powder can be directly fed to the extruder by a feeder without being pelletized to form a film as it is.

  Using a single or twin screw extruder, the pellets are melted at a temperature of about 200 to 300 ° C., filtered through a leaf disk filter, etc. to remove foreign matter, and then formed into a film from a T die. The film is nipped by a cooling roll and an elastic touch roll, and solidified on the cooling roll.

  When introducing from the supply hopper to the extruder, it is preferable to prevent oxidative decomposition or the like under vacuum, reduced pressure, or inert gas atmosphere.

  The extrusion flow rate is preferably performed stably by introducing a gear pump or the like. Further, a stainless fiber sintered filter is preferably used as a filter used for removing foreign substances.

  Additives such as plasticizers and particles may be mixed with the resin in advance, or may be kneaded in the middle of the extruder. In order to add uniformly, it is preferable to use a mixing apparatus such as a static mixer.

  The film temperature on the touch roll side when the film is nipped between the cooling roll and the elastic touch roll is preferably Tg or more and Tg + 110 ° C. or less of the film. A well-known roll can be used for the roll which has the elastic body surface used for such a purpose.

  The elastic touch roll is also called a pinching rotator. As the elastic touch roll, a touch roll disclosed in registered patent 3194904, registered patent 3422798, Japanese Patent Laid-Open No. 2002-36332, Japanese Patent Laid-Open No. 2002-36333, or the like can be preferably used. These can also use what is marketed.

  When peeling the film from the cooling roll, it is preferable to control the tension to prevent deformation of the film.

  Moreover, it is preferable that the film obtained as described above is stretched by the stretching operation after passing through the step of contacting the cooling roll.

  As a method of stretching, a known roll stretching machine or tenter can be preferably used. The stretching temperature is usually preferably performed in the temperature range of Tg to Tg + 60 ° C. of the resin constituting the film.

  Prior to winding, the ends may be slit and cut to the width of the product, and knurling (embossing) may be applied to both ends to prevent sticking or scratching during winding. The knurling method can process a metal ring having an uneven pattern on its side surface by heating or pressing. In addition, since the film has deform | transformed and cannot use as a product normally, the holding | grip part of the clip of both ends of a film is cut out and reused.

<Functional layer>
The hard coat film according to the present invention may be provided with functional layers such as an antistatic layer, a backcoat layer, an antireflection layer, a slippery layer, an adhesive layer, an antiglare layer, and a barrier layer.

<Back coat layer>
In the hard coat film according to the present invention, a back coat layer may be provided on the surface of the base film opposite to the side on which the hard coat layer is provided to prevent curling and sticking.

  As particles added to the back coat layer, examples of inorganic compounds include silicon dioxide, titanium dioxide, aluminum oxide, zirconium oxide, calcium carbonate, calcium carbonate, talc, clay, calcined kaolin, calcined calcium silicate, tin oxide, and oxidation. Mention may be made of indium, zinc oxide, ITO, hydrated calcium silicate, aluminum silicate, magnesium silicate and calcium phosphate.

  The particles contained in the backcoat layer are preferably 0.1 to 50% by mass with respect to the binder. When the back coat layer is provided, the increase in haze is preferably 1.5% or less, more preferably 0.5% or less, and particularly preferably 0.1% or less.

  As the binder, a cellulose ester resin such as diacetylcellulose is preferable.

<Antireflection layer>
The hard coat film according to the present invention can be used as an antireflection film having an external light antireflection function by coating an antireflection layer on the hard coat layer.

  The antireflection layer is preferably laminated in consideration of the refractive index, the film thickness, the number of layers, the layer order, and the like so that the reflectance is reduced by optical interference. The antireflection layer is preferably composed of a low refractive index layer having a refractive index lower than that of the support, or a combination of a high refractive index layer having a refractive index higher than that of the support and a low refractive index layer. Particularly preferably, it is an antireflection layer composed of three or more refractive index layers, and three layers having different refractive indexes from the support side are divided into medium refractive index layers (high refractive index layers having a higher refractive index than the support). Are preferably laminated in the order of a layer having a lower refractive index) / a high refractive index layer / a low refractive index layer. Alternatively, an antireflection layer having a layer structure of four or more layers in which two or more high refractive index layers and two or more low refractive index layers are alternately laminated is also preferably used.

  As the layer structure of the antireflection film, the following structure is conceivable, but is not limited thereto.

Base film / hard coat layer / low refractive index layer Base film / hard coat layer / medium refractive index layer / low refractive index layer Base film / hard coat layer / medium refractive index layer / high refractive index layer / low refractive index Layer Base film / hard coat layer / high refractive index layer (conductive layer) / low refractive index layer Base film / hard coat layer / antiglare layer / low refractive index layer Low refraction essential for antireflection film The refractive index layer preferably contains silica-based fine particles, and the refractive index thereof is lower than the refractive index of the substrate film as the support, and is in the range of 1.30 to 1.45 at 23 ° C. and a wavelength of 550 nm. Preferably there is.

  The film thickness of the low refractive index layer is preferably 5 nm to 0.5 μm, more preferably 10 nm to 0.3 μm, and most preferably 30 nm to 0.2 μm.

  The composition for forming a low refractive index layer preferably contains at least one kind of particles having an outer shell layer and porous or hollow inside as silica-based fine particles. In particular, the particles having the outer shell layer and having a porous or hollow interior are preferably hollow silica-based fine particles.

  The composition for forming a low refractive index layer may contain an organosilicon compound represented by the following general formula (OSi-1) or a hydrolyzate thereof, or a polycondensate thereof.

General formula (OSi-1): Si (OR) ₄
In the organic silicon compound represented by the general formula, R represents an alkyl group having 1 to 4 carbon atoms. Specifically, tetramethoxysilane, tetraethoxysilane, tetraisopropoxysilane and the like are preferably used.

  In addition, a silane coupling agent, a curing agent, a surfactant and the like may be added as necessary.

<Polarizing plate>
The polarizing plate of the present invention using the hard coat film according to the present invention will be described. The polarizing plate can be produced by a general method. The back surface side of the hard coat film according to the present invention is subjected to alkali saponification treatment, and a completely saponified polyvinyl alcohol aqueous solution is used on at least one surface of a polarizing film prepared by immersing and stretching the treated hard coat film in an iodine solution. It is preferable to stick them together.

  The hard coat film may be used on the other surface, or another polarizing plate protective film may be used. The polarizing plate protective film used on the other surface of the hard coat film according to the present invention contains a thermoplastic acrylic resin and a cellulose ester resin, similarly to the base film of the hard coat film. It is preferable to use a protective film in which the mass ratio of the plastic acrylic resin and the cellulose ester resin is thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50. Details of the configuration are as described above, and specific examples include a non-oriented film having a retardation Ro of 590 nm of 0 to 5 nm and an Rt of -20 to +20 nm described in JP-A-2003-12859.

  In addition, an optical compensation film (retardation film) having a retardation of in-plane retardation Ro of 590 nm, 20 to 70 nm, and Rt of 70 to 400 nm may be used as a polarizing plate capable of widening the viewing angle. it can. These can be produced, for example, by the method of JP-A-2002-71957. Alternatively, it is preferable to use an optical compensation film having an optical anisotropic layer formed by aligning a liquid crystal compound such as a discotic liquid crystal. For example, the optically anisotropic layer can be formed by the method described in JP-A-2003-98348.

  Moreover, as a commercially available polarizing plate protective film preferably used, KC8UX2MW, KC4UX, KC5UX, KC4UY, KC8UY, KC12UR, KC4UEW, KC8UCR-3, KC8UCR-4, KC8UCR-5, KC4FR-1, KC4FR-2, KC4FR-2, KC8FR-2 KC4UE (Konica Minolta Opto Co., Ltd.) etc. are mentioned.

  The polarizing film, which is the main component of the polarizing plate, is an element that transmits only light having a polarization plane in a certain direction. A typical polarizing film known at present is a polyvinyl alcohol polarizing film, which is a polyvinyl alcohol film. There are ones in which iodine is dyed on a system film and ones in which a dichroic dye is dyed, but it is not limited to this.

  As the polarizing film, a polyvinyl alcohol aqueous solution is formed and dyed by uniaxially stretching or dyed, or uniaxially stretched after dyeing, and then preferably subjected to a durability treatment with a boron compound. A polarizing film having a thickness of 5 to 30 μm, preferably 8 to 15 μm, is preferably used.

  On the surface of the polarizing film, one side of the hard coat film according to the present invention is bonded to form a polarizing plate. It is preferably bonded with an aqueous adhesive mainly composed of completely saponified polyvinyl alcohol or the like.

<Adhesive layer>
The pressure-sensitive adhesive layer used on one side of the protective film to be bonded to the substrate of the liquid crystal cell is preferably optically transparent and exhibits moderate viscoelasticity and adhesive properties.

  Specific examples of the adhesive layer include adhesives or adhesives such as acrylic copolymers, epoxy resins, polyurethane, silicone polymers, polyethers, butyral resins, polyamide resins, polyvinyl alcohol resins, and synthetic rubbers. A film such as a drying method, a chemical curing method, a thermal curing method, a thermal melting method, a photocuring method, or the like can be formed and cured using a polymer such as the above. Among them, the acrylic copolymer can be preferably used because it is most easy to control the physical properties of the adhesive and is excellent in transparency, weather resistance, durability and the like.

<Liquid crystal display device>
By incorporating the polarizing plate of the present invention produced using the hard coat film according to the present invention into a display device, various image display devices with excellent visibility can be produced.

  The hard coat film according to the present invention is incorporated in a polarizing plate, and is a reflective type, transmissive type, transflective liquid crystal display device or TN type, STN type, OCB type, HAN type, VA type (PVA type, MVA type), IPS. It is preferably used in liquid crystal display devices of various drive systems such as a type and an OCB type.

  EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples.

Example 1
<Preparation of base film 1>
(Preparation of dope solution)
The following materials were sequentially put into a sealed container, the temperature in the container was raised from 20 ° C. to 80 ° C., and the mixture was stirred for 3 hours while maintaining the temperature at 80 ° C. to completely dissolve the cellulose ester. . The silicon oxide fine particles were added dispersed in a solution of a solvent to be added in advance and a small amount of cellulose ester. This dope was filtered using a filter paper (Azumi filter paper No. 244, manufactured by Azumi Filter Paper Co., Ltd.) to obtain a dope solution A.

(Preparation of dope solution A)
Cellulose triacetate (acetyl group substitution degree 2.9) 100 parts by mass Trimethylolpropane tribenzoate 5 parts by mass Ethylphthalylethyl glycolate 5 parts by mass Fine particles of silicon oxide 0.1 parts by mass (Aerosil R972V, manufactured by Nippon Aerosil Co., Ltd.)
Tinuvin 109 (manufactured by Ciba Japan) 1 part by weight Tinuvin 171 (manufactured by Ciba Japan) 1 part by weight Methylene chloride 400 parts by weight Ethanol 40 parts by weight Butanol 5 parts by weight The above materials are mixed to prepare a dope solution A The obtained dope liquid A was cast through a casting die kept at a temperature of 35 ° C. onto a support at a temperature of 35 ° C. made of a stainless steel endless belt to form a web.

  Next, the web was dried on the support, and the web was peeled from the support with a peeling roll when the residual solvent amount of the web reached 80% by mass.

  Next, the web is transported while being dried with a drying air of 90 ° C. in a transport and drying process using a plurality of rolls arranged on the top and bottom, subsequently gripping both end portions of the web with a tenter, and then before stretching in the width direction at 130 ° C. The film was stretched so as to be 1 time. After stretching with a tenter, the web was dried with a drying air of 130 ° C. in a transport drying process using a plurality of rolls arranged vertically. After heat treatment for 15 minutes in an atmosphere with an atmosphere substitution rate of 15 (times / hour) in the drying step, the film was subjected to a knurling process with a width of 10 mm and a height of 10 μm at both ends of the film, cooled to room temperature, and wound on a core. A base film 1 having a thickness of 0.5 m, a thickness of 40 μm, and a length of 4000 m was produced.

<Preparation of hard coat film 1>
On the base film 1 produced above, the following hard coat layer coating composition 1-1 is filtered through a polypropylene filter having a pore size of 0.4 μm to prepare a hard coat layer coating solution, which is coated using a micro gravure coater. and, after drying at 80 ° C., using an ultraviolet lamp, irradiance 80 mW / cm ² irradiation unit to cure the coating layer the amount of irradiation as 80 mJ / cm ^2, forming a hard coat layer 1 dry film thickness 8μm did. Continuously, the hard coat layer coating composition 1-2 is applied onto the hard coat layer 1 by an extrusion coater, dried at 80 ° C., and nitrogen so that the oxygen concentration becomes 1.0 vol% or less. while purging, the illuminance of the irradiation unit using a UV lamp 150 mW / cm ^2, thereby curing the coated layer irradiation amount as 250 mJ / cm ^2, to form a hard coat layer 2 of a dry film thickness of 0.6 .mu.m. Further, after forming the hard coat layer 2, the following back coat layer coating composition 1 was applied to the surface opposite to the surface on which the hard coat layer was applied with a coater so as to have a wet film thickness of 10 μm. Then, a back coat layer 1 was provided, wound up, and a roll-shaped hard coat film 1 was produced.

(Hard Coat Layer Coating Composition 1-1)
The following materials were stirred and mixed to obtain hard coat layer coating composition 1.

Pentaerythritol triacrylate 20 parts by mass Pentaerythritol tetraacrylate 50 parts by mass Dipentaerythritol hexaacrylate 30 parts by mass Dipentaerythritol pentaacrylate 30 parts by mass Irgacure 184 (manufactured by Ciba Japan) 5.0 parts by mass Polyether-modified silicone (KF354L) Manufactured by Shin-Etsu Chemical)
2.0 parts by mass Propylene glycol monomethyl ether 10 parts by mass Methyl acetate 45 parts by mass Methyl ethyl ketone 65 parts by mass Cyclohexanone 10 parts by mass (hard coat layer coating composition 1-2)
(Preparation of silica particle dispersion)
After adding 50 parts by mass of methyl ethyl ketone to 25 parts by mass of silica particles having an average particle size of 0.5 μm (KE-P50, manufactured by Nippon Shokubai Co., Ltd.), the mixture was treated with an ultrasonic homogenizer for 15 minutes to prepare a silica particle dispersion.

  Next, the following materials were stirred and mixed to obtain a hard coat layer coating composition 1-2.

Urethane acrylate purple light UV1700B (manufactured by Nippon Synthetic Chemical)
60 parts by mass Irgacure 184 (manufactured by Ciba Japan) 3.0 parts by mass Silica particle dispersion 90 parts by mass Polyether-modified polydimethylsiloxane (BYK-UV3510, manufactured by Big Chemie Japan) 2.0 parts by mass Propylene glycol monomethyl ether 200 parts by mass Methyl ethyl ketone 100 parts by mass (Backcoat layer coating composition 1)
Methyl acetate 80 parts by mass Methanol 30 parts by mass <Preparation of hard coat film 2>
In the production of the hard coat film 1, the silica particles of the hard coat layer coating composition 1-2 were changed to silica particles having an average particle size of 0.3 μm (KE-P30, manufactured by Nippon Shokubai Co., Ltd.). A hard coat film 2 was produced in the same manner except that the film thickness was changed to 0.35 μm.

<Preparation of hard coat film 3>
In the production of the hard coat film 1, the hard coat film 3 was produced in the same manner except that the hard coat layer 2 was not provided and the hard coat layer coating composition 1-1 was changed to the hard coat layer coating composition 3-1. did.

(Hardcoat layer coating composition 3-1)
<Preparation of reactive silica particles (Xa)>
(Preparation of organic compound (X) having a polymerizable unsaturated group)
To a solution consisting of 23 parts of mercaptopropyltrimethoxysilane and 0.5 parts of dibutyltin dilaurate, 60 parts of isophorone diisocyanate was added dropwise at 50 ° C. over 1 hour, followed by stirring at 80 ° C. for 3 hours. To this, 202 parts of NK ester A-TMM-3LM-N (a solution comprising 60% by mass of pentaerythritol triacrylate and 40% by mass of pentaerythritol tetraacrylate) made by Shin-Nakamura Chemical Co., Ltd. was added dropwise at 30 ° C. over 1 hour. The specific organic compound (S1) was obtained by heating and stirring at 3 ° C. for 3 hours. In the infrared absorption spectrum of the product, the absorption peak at 2550 cm −1 characteristic for the mercapto group in the raw material and the absorption peak at 2260 cm −1 characteristic for the isocyanate group disappeared, and [−O—C (= O) —NH—] and [—S—C (═O) —NH—] groups, a peak at 1660 cm −1 characteristic for the carbonyl and a peak at 1720 cm −1 characteristic for the acryloyl group are observed, A specific organic compound having both an acryloyl group as a polymerizable unsaturated group, a [—S—C (═O) —NH—] group, and a [—O—C (═O) —NH—] group has been generated. Showed that. 9.5 parts of the composition produced (including 7.3 parts of organic compound (X) having a polymerizable unsaturated group), silica particle dispersion (silica concentration 35%, MEK sol manufactured by Nissan Chemical Industries) 98 parts, ion A mixture of 0.13 parts of exchange water and 0.01 parts of p-hydroxyphenyl monomethyl ether was stirred at 60 ° C. for 5 hours, and then 1.45 parts of orthoformate methyl ester was added, followed by heating at the same temperature for 1 hour. A dispersion of reactive silica particles (Xa) was obtained by stirring. 2 g of this dispersion was weighed on an aluminum dish, dried on a hot plate at 175 ° C. for 1 hour, and weighed to determine the solid content, which was 36%. The average particle size of the silica particles was 35 nm. Here, the average particle diameter was measured with a transmission electron microscope. Next, the following materials were stirred and mixed to obtain a hard coat layer coating composition 3-1.

Pentaerythritol triacrylate 2.5 parts by mass Pentaerythritol tetraacrylate 6.5 parts by mass Dipentaerythritol hexaacrylate 3.8 parts by mass Dipentaerythritol pentaacrylate 3.8 parts by mass Irgacure 184 (manufactured by Ciba Japan) 0.85 Mass parts Reactive silica particle dispersion (Reactive silica particles (Xa) 36%)
100 parts by mass Polyether-modified polydimethylsiloxane (BYK-UV3510, manufactured by Big Chemie Japan) 1.0 part by mass Propylene glycol monomethyl ether 5 parts by mass <Preparation of hard coat film 4>
In preparation of the hard coat film 1, the thickness of the hard coat layer 2 was changed to 0.08 μm, and the silica particles of the coating composition were changed to acrylic crosslinked fine particles / average particle diameter of 14 nm (MG-153, manufactured by Nippon Paint). In the same manner, a hard coat film 4 was produced.

<Preparation of hard coat film 5>
In the production of the hard coat film 1, the silica particles of the hard coat layer coating composition 1-2 are changed to silica particles having an average particle diameter of 1 μm (KE-P100, manufactured by Nippon Shokubai Co., Ltd.), and the addition amount of the silica particle dispersion is 110. A hard coat film 5 was produced in the same manner except that the mass part was changed and the film thickness of the hard coat layer 2 was changed to 1.1 μm.

<Preparation of hard coat film 6>
In the production of the hard coat film 1, a hard coat film 6 was produced in the same manner except that the hard coat layer 2 was not provided.

<Preparation of hard coat film 7>
In the production of the hard coat film 1, the hard coat film 7 was produced in the same manner except that the hard coat layer 2 was not provided and the hard coat layer coating composition 1-1 was changed to the hard coat layer coating composition 7-1. did.

  The following materials were stirred and mixed to obtain a hard coat layer coating composition 7-1.

(Hard Coat Layer Coating Composition 7-1)
Pentaerythritol triacrylate 5.0 parts by mass Pentaerythritol tetraacrylate 13 parts by mass Dipentaerythritol hexaacrylate 7.0 parts by mass Dipentaerythritol pentaacrylate 7.0 parts by mass Irgacure 184 (manufactured by Ciba Japan) 1.6 parts by mass Reactive silica particle dispersion (Reactive silica particles (Xa) 36%)
15 parts by mass Polyether-modified polydimethylsiloxane (BYK-UV3510, manufactured by Big Chemie Japan) 1.0 part by mass Propylene glycol monomethyl ether 5 parts by mass Methyl ethyl ketone 33 parts by mass <Preparation of hard coat film 8>
In the production of the hard coat film 1, the hard coat film 8 was produced in the same manner except that the hard coat layer 2 was not provided and the hard coat layer coating composition 1-1 was changed to the hard coat layer coating composition 8-1. did.

(Hard Coat Layer Coating Composition 8-1)
The following materials were stirred and mixed to obtain a hard coat layer coating composition 8-1.

Pentaerythritol triacrylate 5.0 parts by mass Pentaerythritol tetraacrylate 13 parts by mass Dipentaerythritol hexaacrylate 7.0 parts by mass Dipentaerythritol pentaacrylate 7.0 parts by mass Irgacure 184 (manufactured by Ciba Japan) 1.6 parts by mass Reactive silica particle dispersion (Reactive silica particles (Xa) 36%)
58 parts by mass Polyether-modified polydimethylsiloxane (BYK-UV3510, manufactured by Big Chemie Japan) 1.0 part by mass Propylene glycol monomethyl ether 5 parts by mass Methyl ethyl ketone 25 parts by mass <Preparation of hard coat film 9>
In the production of the hard coat film 5, the hard coat film 9 was produced in the same manner except that the addition amount of the silica particle dispersion was 125 parts by mass and the film thickness of the hard coat layer 2 was changed to 0.95 μm.

<Preparation of hard coat film 10>
In the production of the hard coat film 5, the hard coat layer 2 is irradiated with ultraviolet rays without purging with nitrogen, and further, the hard coat layer coating composition 1-1 is applied onto the hard coat layer 2 by an extrusion coater at 80 ° C. The coating layer is cured by drying and purging with nitrogen so that the atmosphere has an oxygen concentration of 1.0% by volume or less, using an ultraviolet lamp and setting the illuminance of the irradiated part to 150 mW / cm ² and the irradiation amount to 250 mJ / cm ^2. A hard coat film 10 was produced in the same manner except that the hard coat layer 3 having a dry film thickness of 0.1 μm was formed to have a three-layer structure.

<Preparation of hard coat film 11>
In the production of the hard coat film 1, the silica particles of the hard coat layer coating composition 1-2 were changed to silica particles having an average particle diameter of 1 μm (KE-P100, manufactured by Nippon Shokubai Co., Ltd.), and the addition amount of the silica particle dispersion was 10 A hard coat film 11 was produced in the same manner except that the mass part was changed and the film thickness of the hard coat layer 2 was changed to 1.15 μm.

<Preparation of hard coat film 12>
In the production of the hard coat film 1, the hard coat film 12 was produced in the same manner except that the hard coat layer 2 was not provided and the hard coat layer coating composition 1-1 was changed to the hard coat layer coating composition 12-1. did.

(Hard Coat Layer Coating Composition 12-1)
<Preparation of reactive silica particles (Xb)>
Reactive silica particles (Xb) were produced in the same manner as in the production of reactive silica particles (Xa) except that the silica particle dispersion was changed to particles having different particle diameters. The particle diameter of the reactive silica particles (Xb) was 15 nm, and the solid content was 36%.

  The following materials were stirred and mixed to obtain a hard coat layer coating composition 12-1.

Pentaerythritol triacrylate 2.5 parts by mass Pentaerythritol tetraacrylate 6.5 parts by mass Dipentaerythritol hexaacrylate 3.8 parts by mass Dipentaerythritol pentaacrylate 3.8 parts by mass Irgacure 184 (manufactured by Ciba Japan) 0.85 Mass parts Reactive silica particle dispersion (Reactive silica particles (Xb) 36%)
115 parts by mass Polyether-modified polydimethylsiloxane (BYK-UV3510, manufactured by BYK Japan) 1.0 part by mass Propylene glycol monomethyl ether 5 parts by mass <Preparation of hard coat film 13>
In the production of the hard coat film 1, the hard coat layer 2 was not provided, the hard coat layer coating composition 1-1 was applied, dried, and then a mold roll produced with reference to the example of JP-A-2008-276198. After stamping (here, the mold roll used was an array of the molds regularly), and the irradiance of the irradiated part using an ultraviolet lamp while purging with nitrogen so that the oxygen concentration was 1.0% by volume or less. The hard coat film 13 was produced in the same manner except that the coating layer was cured at 150 mW / cm ² and the irradiation amount was 250 mJ / cm ² to form the hard coat layer 1 having a dry film thickness of 10 μm.

<Preparation of hard coat film 14>
In the production of the hard coat film 13, a hard coat film 14 was produced in the same manner except that the shape of the mold roll was changed.

<Preparation of hard coat film 15>
In the production of the hard coat film 13, a hard coat film 15 was produced in the same manner except that the shape of the mold roll was changed.

<Preparation of Polarizing Plate 101>
(Alkaline saponification treatment)
A polarizing plate 101 was prepared using one each of the hard coat film 1 and the base film 1 as a protective film for the polarizing plate.

(A) Production of Polarizing Film What was impregnated with 10 parts by mass of glycerin and 170 parts by mass of water in 100 parts by mass of polyvinyl alcohol (hereinafter abbreviated as PVA) having a saponification degree of 99.95 mol% and a polymerization degree of 2400. After melt-kneading and defoaming, it was melt extruded from a T die onto a metal roll to form a film. Then, it dried and heat-processed and obtained the PVA film.

  The obtained PVA film had an average thickness of 25 μm, a moisture content of 4.4%, and a film width of 3 m.

  Next, the obtained PVA film was continuously processed in the order of preliminary swelling, dyeing, uniaxial stretching by a wet method, fixing treatment, drying, and heat treatment to prepare a polarizing film. That is, the PVA film was preliminarily swollen in water at a temperature of 30 ° C. for 30 seconds, and immersed in an aqueous solution having an iodine concentration of 0.4 g / liter and a potassium iodide concentration of 40 g / liter at a temperature of 35 ° C. for 3 minutes. Subsequently, the film was uniaxially stretched 6 times in a 50% aqueous solution with a boric acid concentration of 4% under the condition that the tension applied to the film was 700 N / m, and the potassium iodide concentration was 40 g / liter and the boric acid concentration was 40 g / liter. Then, it was immersed in an aqueous solution having a zinc chloride concentration of 10 g / liter and a temperature of 30 ° C. for 5 minutes for fixing. Thereafter, the PVA film was taken out, dried with hot air at a temperature of 40 ° C., and further heat-treated at a temperature of 100 ° C. for 5 minutes. The obtained polarizing film had an average thickness of 13 μm, a polarizing performance of 43.0% transmittance, a polarization degree of 99.5%, and a dichroic ratio of 40.1.

(B) Production of Polarizing Plate A polarizing plate 101 was produced by bonding the polarizing film, the substrate film 1 and the hard coat film 1 according to the following steps 1 to 4.

  Process 1: The above-mentioned polarizing film was immersed for 1 to 2 seconds in the storage tank of the polyvinyl alcohol adhesive agent solution of 2 mass% of solid content.

  Process 2: The alkali saponification process was implemented on the hard coat film 1 which affixed the peelable protective film (product made from PET) on the base film 1 and the hard coat layer on the following conditions. Next, the excess adhesive adhered to the polarizing film immersed in the polyvinyl alcohol adhesive solution in Step 1 is lightly removed, and the base film 1 and the hard coat film 1 are sandwiched between the polarizing films as shown in FIG. Laminated.

(Alkaline saponification treatment)
Saponification step 2.5M-KOH 50 ° C. 120 seconds Water washing step Water 30 ° C. 60 seconds Neutralization step 10 parts by mass HCl 30 ° C. 45 seconds Water washing step Water 30 ° C. 60 seconds After saponification treatment, water washing, neutralization, water washing in this order And then dried at 100 ° C.

Step 3: The laminate was bonded at a speed of about 2 m / min at a pressure of ^{20 to} 30 N / cm ² with two rotating rollers. At this time, it was carried out with care to prevent bubbles from entering.

  Step 4: The sample prepared in Step 3 was dried in a dryer at a temperature of 100 ° C. for 5 minutes to prepare a polarizing plate.

  Step 5: A commercially available acrylic adhesive is applied to the base film 1 of the polarizing plate prepared in Step 4 so that the thickness after drying is 25 μm, and dried in an oven at 110 ° C. for 5 minutes to form an adhesive layer. Then, a peelable protective film was attached to the adhesive layer. This polarized light was cut (punched) into a size of 576 × 324 mm, and the polarizing plate 101 was produced.

<Preparation of polarizing plates 102 to 115>
Polarizers 102 to 115 were produced in the same manner except that the hard coat film 1 was changed to the hard coat films 2 to 15 in the production of the polarizer 101.

<Production of Liquid Crystal Display Device 401>
Remove the polarizing plate of NEC notebook PC LaVie G type liquid crystal panel, and make the above-prepared polarizing plate 101 (see FIG. 2 for the configuration) as the polarizing plate on the viewing side so that the hard coat layer is on the viewing side, Layer 5 and liquid crystal cell glass were bonded together. Further, on the backlight side, an acrylic adhesive having a thickness of 25 μm is used for the polarizing plate 201 that is laminated and bonded so as to sandwich the polarizing film with the base film 1 that has been subjected to alkali saponification treatment in the same manner as described above. A liquid crystal panel 301 was prepared by pasting the liquid crystal cell glass. Next, the liquid crystal panel 301 was set on a liquid crystal television, and a liquid crystal display device 401 was manufactured.

<Production of Liquid Crystal Display Devices 402 to 415>
Liquid crystal display devices 402 to 415 were similarly manufactured except that the polarizing plate 101 was changed to the polarizing plates 102 to 115 in the preparation of the liquid crystal display device 401.

<Evaluation>
The following evaluation was performed about the produced said hard coat films 1-15, the polarizing plates 101-115, and the image display apparatuses 401-415.

(Hard coat film)
a. Surface Roughness (Ra) Measurement The hard coat layers of the hard coat films 1 to 15 prepared above were measured 10 times using an optical interference type surface roughness meter (RST / PLUS, manufactured by WYKO), and the measurement results From the average, the surface roughness (Ra) of each hard coat film was determined. The obtained results are shown in Table 1.

b. Measurement of the number of protrusions When measuring the surface roughness (Ra), the number of protrusions was counted (number per measurement area of 0.01 mm ² ). Next, the number of projections of the hard coat layer of each hard coat film was determined by averaging the counted 10 results.

  As the number of protrusions, protrusions having a height of 3 nm or more from the average line of the roughness curve were counted.

  The obtained results are shown in Table 1.

c. Haze measurement The haze (Hf) of the base film was measured using a haze meter (NDH2000; manufactured by Nippon Denshoku Industries Co., Ltd.) according to JIS-K7136. Next, the haze of each prepared hard coat film (Hh) was measured in the same manner as the base film.

  The difference in haze value (Hf) of the base film was subtracted from the haze value (Hh) of each hard coat film, and the haze change (Δhaze) before and after the application of the hard coat layer was measured. Table 1 shows the results of the haze value (Hh) and haze change (Δhaze) of the hard coat film.

  In addition, the haze value (Hf) of the base film was 0.26%.

(Polarizer)
a. Durability test After peeling off the peelable protective film of the hard coat layer of the polarizing plates 101 to 115, 50 polarizing plates were stacked on each other as shown in FIG. The film was bonded to the top and stored at 85 ° C. and 95% for 168 hours.

b. Observation of deformation failure The polarizing plate subjected to the above durability test was observed from the hard coat layer side, and the state of deformation failure was observed according to the following criteria.

A: Deformation failure is not observed at all. O: Deformation failure is observed in a small part, but there is no problem in actuality. Δ: Deformation failure is partially observed. There is a problem in terms of actual damage ×: It can be seen that partial deformation failure is clearly seen even from a distance.

(Liquid crystal display device)
a. Visibility (Clearness) Evaluation The liquid crystal display devices 401 to 415 produced above were placed on a desk 80 cm high from the floor, and a daylight direct fluorescent lamp (FLR40S · D / M-X (Panasonic Corporation) 40W × 2 were used as one set, and 10 sets were arranged at 1.5 m intervals. In this case, when the evaluator is in front of the display surface of the liquid crystal display panel, the fluorescent lamp is arranged so that the fluorescent lamp comes to the ceiling portion from the evaluator's overhead to the rear. Next, the visibility of the liquid crystal display devices 401 to 415 was evaluated according to the following criteria. The obtained results are shown in Table 1.

○: Fluorescent light is clearly visible △: Fluorescent light is slightly whitish ×: Fluorescent light is blurred and appears whitish

As can be seen from the results in Table 1, the number of protrusions of the hard coat layer of the hard coat film is 500 to 200,000 pieces / mm ² , and the arithmetic average roughness Ra of the hard coat layer is 2 nm to 20 nm, and the haze value of the hard coat film The polarizing plate of the present invention having (Hh) of 0.2 to 0.6% prevents deformation failure when stored under high temperature and high humidity, and visibility (clearness) when used in a liquid crystal display device. Excellent performance in both.

  Among the present inventions, the polarizing plate of the present invention in which the arithmetic average roughness Ra of the hard coat layer is 4 nm to 20 nm or the hard coat layer has a two-layer structure exhibits a particularly excellent deformation failure prevention effect. In addition, about the hard coat film and polarizing plate concerning this invention, after adjusting humidity at 23 degreeC55% RH for 24 hours, according to the pencil hardness evaluation method which JIS-K5400 prescribes | regulates using the test pencil which prescribes | regulates JIS-S6006. The pencil hardness was tested using a 500 g weight. The pencil hardness of the hard coat film and the polarizing plate according to the present invention was 3H or more.

Example 2
In producing the hard coat film 1, hard coat films 16 to 20 were produced in the same manner except that the substrate film 1 was changed to the following substrate films 2 to 6. Polarizers 116 to 120 and liquid crystal display devices 416 to 420 were produced using these produced hard coat films 16 to 20.

<Preparation of hard coat film 16>
(Preparation of base film 2)
(Adjustment of dope solution B)
Commercially available thermoplastic acrylic resin (Dyanal BR85 (manufactured by Mitsubishi Rayon Co., Ltd.) Mw 280000) 70 parts by weight Cellulose ester (cellulose acetate propionate acyl group total substitution degree: 2.75, acetyl group substitution degree 0.19, propionyl) Group substitution degree 2.56, Mw = 200000) 30 parts by mass Methylene chloride 300 parts by mass Ethanol 40 parts by mass The above composition was sufficiently dissolved while heating to prepare a dope solution.

(Film formation)
The produced dope solution B was uniformly cast on a stainless steel band support at a temperature of 22 ° C. and a width of 2 m using a belt casting apparatus. With the stainless steel band support, the solvent was evaporated until the amount of residual solvent reached 100%, and then peeled off from the stainless steel band support. The peeled thermoplastic acrylic resin / cellulose ester resin web was evaporated at 35 ° C., slit to 1.6 m width, and then stretched 1.1 times in the width direction with a tenter, followed by a drying temperature of 130 ° C. And dried. At this time, the residual solvent amount when starting stretching with a tenter was 10%. After stretching with a tenter, relaxation was performed at 130 ° C. for 5 minutes, and then drying was completed while transporting a drying zone at 120 ° C. and 140 ° C. with many rolls, slitting to a width of 1.5 m, and a width of 10 mm at both ends of the film Then, a knurling process having a height of 10 μm was performed and wound around a core to obtain a base film 2. The film thickness was 40 μm and the winding length was 4000 m.

(Preparation of base film 3-6)
In preparation of the base film 2, the types and content ratios of the thermoplastic acrylic resin and the cellulose ester resin were changed as shown in Table 2 to prepare base films 3 to 6.

<Preparation of polarizing plates 116-120>
Polarizers 116 to 120 were produced in the same manner except that the hard coat film 1 was changed to the hard coat films 16 to 20 in the production of the polarizer 101.

<Production of Liquid Crystal Display Devices 416 to 420>
Liquid crystal display devices 416 to 420 were similarly manufactured except that the polarizing plate 101 was changed to the polarizing plates 116 to 120 in the preparation of the liquid crystal display device 401.

<Evaluation>
In the durability test of the polarizing plate of Example 1, the polarizing plate 101 and the liquid crystal display device 401 produced in Example 1 and the hard coat films 16 to 16 produced in the same manner except that the storage time was changed to 336 hours. 20, polarizing plates 116-120 and liquid crystal display devices 416-420 were evaluated. The obtained results are shown in Table 2.

  As can be seen from the results in Table 2, in a more severe test, the base film contains a thermoplastic acrylic resin and a cellulose ester resin, and the contained mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is determined as follows: By using a film in the range of cellulose ester resin = 95: 5 to 50:50, the effect of preventing deformation failure is particularly excellent, and the visibility (clearness) when used in a liquid crystal display device is also good. .

Example 3
In preparation of the polarizing plate 101 of Example 1, the polarizing plates 121-125 were produced except having changed the protective film into the base film 2-6. Liquid crystal display devices 421 to 425 were produced using these produced polarizing plates.

<Evaluation>
In the same manner as in Example 2, the polarizing plate 101 and the liquid crystal display device 401 produced in Example 1 and the produced polarizing plates 121 to 125 and the liquid crystal display devices 421 to 425 were evaluated. The obtained results are shown in Table 3.

  As can be seen from the results in Table 3, in a more severe test, the protective film contains a thermoplastic acrylic resin and a cellulose ester resin, and the contained mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is determined as follows: thermoplastic acrylic resin: cellulose By using a film in the range of ester resin = 95: 5 to 50:50, the effect of preventing deformation failure is particularly excellent, and the visibility (clearness) when used in a liquid crystal display device is also good.

DESCRIPTION OF SYMBOLS 1 Base film 2a, 2b Hard coat layer 3 Polarizing film 4 Protective film 5 Adhesive layer 6 Hard coat film 7 Polarizing plate 8 Glass plate

Claims (7)

In a polarizing plate in which a hard coat film having a hard coat layer on a protective film, a polarizing film and a base film is laminated in this order, the hard coat layer is a protrusion having a height of 3 nm or more from the average line of the roughness curve the has 500-200000 cells / mm ^2, the hard coat layer of the arithmetic average roughness Ra (JIS B0601: 2001) is 2 to 20 nm, and the haze value of the hard coat film (Hh) is 0.2 A polarizing plate characterized by being 0.6%.   The difference (Hh−Hf) between the haze value (Hh) of the hard coat film and the haze value (Hf) of the base film of the hard coat film is 0.02% to 0.3%, The polarizing plate according to claim 1.   3. The polarizing plate according to claim 1, wherein the arithmetic average roughness Ra of the hard coat layer is 4 nm to 20 nm.   The polarizing plate according to claim 1, wherein the hard coat layer has a two-layer structure.   The base film of the hard coat film contains a thermoplastic acrylic resin and a cellulose ester resin having a weight average molecular weight (Mw) of 80000 to 500,000, and the mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is It is thermoplastic acrylic resin: cellulose-ester resin = 95: 5-50: 50, The polarizing plate of any one of Claims 1-4 characterized by the above-mentioned.   The protective film contains a thermoplastic acrylic resin and a cellulose ester resin, and the mass ratio of the thermoplastic acrylic resin and the cellulose ester resin is thermoplastic acrylic resin: cellulose ester resin = 95: 5 to 50:50. The polarizing plate of any one of Claims 1-5 characterized by the above-mentioned.   A liquid crystal display device comprising the polarizing plate according to any one of claims 1 to 6 in at least one of the liquid crystal cells.