JP5410770B2 - Polarizer outer surface protective film, polarizing plate, and liquid crystal display element - Google Patents

Description

  The present invention relates to a polarizer outer surface protective film, a polarizing plate including the polarizer outer surface protective film, and a liquid crystal display device including the polarizing plate.

  In recent years, liquid crystal display devices (LCDs) are widely used in place of CRTs because of their thinness and light weight and low power consumption. The field of use of liquid crystal display elements is expanding from small products such as conventional calculators and watches to large products such as automotive instruments, PC monitors, and televisions.

  As shown in FIG. 5, a general liquid crystal display element 21 arranged in a liquid crystal display device has a liquid crystal cell 27 in which a liquid crystal layer 27 is sandwiched between transparent medium layers 26 (for example, glass) on both sides, and has a polarization ability. A polarizing plate 22 having a polarizing plate protective film 23 bonded to both surfaces of the polarizer 24, and a structure in which the liquid crystal cell 25 is sandwiched from above and below by the polarizing plate 22 through an adhesive layer 28. ing. Thus, the polarizer 24 is protected by the polarizer protective film 23 from the viewpoint of improving the strength and facilitating handling.

  In general, polyvinyl alcohol (PVA), which is a hydrophilic resin, is used as a material for the polarizer, and the PVA film is uniaxially stretched and then dyed with iodine or a dichroic dye, or dyed. Is then stretched and then crosslinked with a boron compound to form a polarizer. The polarizer protective film is required to have properties such as optical transparency and low birefringence, a smooth surface, and excellent adhesion to a polarizer made of PVA. Therefore, triacetyl cellulose (TAC) is generally used. Triacetyl cellulose is saponified with an alkali (the ester group is converted to a hydroxyl group that is a hydrophilic group) and then adhered to a polarizer composed of polyvinyl alcohol that is a hydrophilic resin. As a technique for improving various required characteristics of triacetyl cellulose as described above, for example, formation of a predetermined resin layer on a triacetyl cellulose layer (Japanese Patent Laid-Open Nos. 9-113728 and 9-281333). Proposed. However, since triacetyl cellulose is expensive, development of an inexpensive alternative material having equivalent properties is required.

  The polarizer protective film disposed on the inner surface side (the side closer to the liquid crystal cell) of the liquid crystal display element is particularly required to have a small birefringence (non-orientation). There is no suitable substitute for acetylcellulose. On the other hand, as a required characteristic of the polarizer protective film disposed on the outer surface side of the liquid crystal display element (the side away from the liquid crystal cell, that is, the position of the uppermost layer and the lowermost layer 23 in FIG. 5), the presence or absence of birefringence However, since transparency becomes a more important position, development of alternative materials other than triacetylcellulose is expected.

  As general-purpose resin materials having high transparency that can be substituted for triacetyl cellulose, acrylic resins, polycarbonate resins, polypropylene resins, cycloolefin resins, polyethylene terephthalate resins, and the like are conceivable. However, since these resins do not have a hydrophilic group, there is an inconvenience that adhesiveness with polyvinyl alcohol, which is a hydrophilic resin constituting a polarizer, is inferior. Cannot be used as Therefore, in addition to having high transparency, development of a novel polarizer outer surface protective film for facilitating adhesion with a polarizer made of polyvinyl alcohol and disposed on the outer surface side of a liquid crystal display element is desired. It is rare.

Japanese Laid-Open Patent Publication No. 9-11728 JP-A-9-281333

  The present invention has been made in view of these disadvantages, and is a novel material disposed on the outer surface side of a liquid crystal display element that has high transparency and is subjected to an easy adhesion treatment for a polarizer made of polyvinyl alcohol. An object of the present invention is to provide a polarizer outer surface protective film, a polarizing plate provided with such a polarizer outer surface protective film, and a liquid crystal display element.

The invention made to solve the above problems is
A polarizer outer surface protective film disposed on the outer surface side of the liquid crystal display element,
A transparent synthetic resin base material layer;
A primer layer laminated on the inner surface side of the base material layer,
A cellulose ester layer laminated on the inner surface side of the primer layer,
The primer layer is formed from an aqueous latex,
The above aqueous latex is (meth) acrylic acid, (meth) acrylic acid derivative, (meth) acrylamide, (meth) acrylamide derivative, vinyl ester, olefin, styrene, crotonic acid ester, itaconic acid ester, fumarate A polarizer comprising a polymer obtained from a single unsaturated monomer selected from the group consisting of acid esters, vinyl ketones, heterocyclic-containing vinyl monomers, and unsaturated nitriles It is an outer surface protective film.

  According to the polarizer outer surface protective film, high transparency required as a film for protecting the polarizer located on the outer surface side of the liquid crystal display element is obtained by using a transparent synthetic resin as a constituent material of the base material layer. It is done. The polarizer outer surface protective film has a primer layer laminated on the inner surface side of the base material layer and a cellulose ester layer on the inner surface side of the primer layer so as to facilitate adhesion with a polarizer made of polyvinyl alcohol. By laminating, adhesion with a polarizer made of polyvinyl alcohol, which is a hydrophilic resin, is dramatically improved. That is, the cellulose ester layer formed by such an easy adhesion treatment is saponified with alkali to produce a hydroxyl group that is a hydrophilic group, thereby effectively improving the adhesion to polyvinyl alcohol that is a hydrophilic resin. To do. In the present specification, “inner surface” means a central liquid crystal cell side in a liquid crystal display element in which a liquid crystal cell is sandwiched between a pair of polarizing plates, and “outer surface” means the opposite side.

The primer layer of the polarizer outer surface protective film is formed from an aqueous latex. The primer layer formed from such an aqueous latex has a chemical affinity with both the transparent synthetic resin base material layer and the cellulose ester layer, so that these layers are stably bonded. Further, peeling of the cellulose ester layer is effectively prevented, so that the easy adhesion treatment of the base material layer to the polarizer can be reliably performed.

  When the primer layer of the polarizer outer surface protective film is formed from an aqueous latex, the aqueous latex includes (meth) acrylic acid, (meth) acrylic acid derivative, (meth) acrylamide, (meth) acrylamide derivative, vinyl ester. Olefins, styrenes, crotonic acid esters, itaconic acid esters, fumaric acid esters, vinyl ketones, heterocyclic vinyl monomers and unsaturated nitriles. Those containing a polymer obtained from a saturated monomer are used. By using a primer layer formed from an aqueous latex containing these polymers, the bonding between the base material layer and the cellulose ester layer is strengthened through the primer layer, and peeling of the cellulose ester layer is reliably prevented. .

  The synthetic resin constituting the base material layer in the polarizer outer surface protective film is at least one selected from the group consisting of acrylic resins, polycarbonate resins, polypropylene resins, cycloolefin resins, and polyethylene terephthalate resins. It's okay. By using these synthetic resins, a polarizer outer surface protective film having high transparency and appropriate strength for protecting the polarizer can be obtained.

  The cellulose ester constituting the cellulose ester layer may be at least one selected from the group consisting of triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Each of these cellulose esters is saponified with an alkali to generate a hydroxyl group that is a hydrophilic group, and thus can be firmly bonded to a polarizer made of polyvinyl alcohol that is a hydrophilic resin.

  In the polarizer outer surface protective film, the total thickness of the primer layer and the cellulose ester layer may be 0.02 μm or more and 4 μm or less. By making the total thickness of the primer layer and the cellulose ester layer 0.02 μm or more, facilitation of adhesion of a polarizer made of polyvinyl alcohol is promoted. On the other hand, when the total thickness of the primer layer and the cellulose ester layer is 4 μm or less, a sufficiently thin polarizer outer surface protective film can be obtained, and an increase in the thickness of the polarizing plate can be suppressed.

  The polarizer outer surface protective film includes an antireflection layer (including, for example, an antiglare layer, an antireflection layer, or a low refractive index layer) or a hard coat layer laminated on the outer surface side of the base material layer. It may be. Furthermore, when the polarizer outer surface protective film provided with the antireflection layer is disposed on the display surface side of the liquid crystal display element, the antireflection function can be exhibited together with the protection of the polarizer. In addition, since the polarizer outer surface protective film further includes a hard coat layer, the protective function of the polarizer can be enhanced.

  A polarizing plate can be constituted by laminating the polarizer outer surface protective film on the outer surface side of a polarizer made of polyvinyl alcohol and laminating the polarizer inner surface protective film on the inner surface side of the polarizer. In such a polarizing plate, a polarizer and a polarizer outer surface protective film are obtained by using a polarizer outer surface protective film provided with a base material layer subjected to an easy adhesion treatment for polyvinyl alcohol on the outer surface side of the polarizer. The adhesion and durability of adhesion are improved, and the strength and handling of the polarizing plate are improved. In addition, when a polarizer inner surface protective film made of cellulose ester, which has been conventionally used, is used on the inner surface side of the polarizer, it has a small birefringence, so that the performance of liquid crystal molecules is not affected. A protective function can be exhibited.

  By laminating the polarizing plate on at least one surface side of the liquid crystal cell, a liquid crystal display element can be configured. In such a liquid crystal display element, since the adhesiveness between the polarizer and the polarizer outer surface protective film and the adhesive durability are high, and the strength and handling property of the polarizing plate are excellent, various characteristics of the liquid crystal display element are long. It is demonstrated stably over a period of time, improving reliability.

  As described above, the polarizer outer surface protective film of the present invention is a transparent synthetic material whose inner surface is surface-treated with a cellulose ester via a primer layer so as to facilitate adhesion with a polarizer made of polyvinyl alcohol. Since the resin-made base material layer is provided, high transparency is obtained and adhesion with a polarizer made of polyvinyl alcohol, which is a hydrophilic resin, is dramatically improved. Moreover, when a polarizing plate is provided with the said polarizer outer surface protective film, the intensity | strength and handleability of such a polarizing plate improve. Furthermore, when the liquid crystal display element includes the polarizing plate, desired characteristics are stably exhibited over a long period of time.

It is typical sectional drawing of the polarizer outer surface protection film by this invention. It is typical sectional drawing of the polarizing plate provided with the polarizer outer surface protective film by this invention of FIG. It is a schematic diagram which shows the apparatus for manufacturing the polarizing plate by this invention of FIG. It is typical sectional drawing of the liquid crystal display element provided with the polarizing plate by this invention of FIG. It is a schematic diagram which shows the structure of the general liquid crystal display element by a prior art.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings as appropriate.

  The polarizer outer surface protective film 1 in FIG. 1 has a base layer 2, a primer layer 3, and a cellulose ester layer 4 made of a transparent synthetic resin. The polarizer outer surface protective film 1 is used as a protective film for a polarizer for improving resistance to impact and handleability, and is disposed on the outer surface side (A direction side shown in the figure) of the liquid crystal display element. The

  The resin constituting the base layer 2 made of transparent resin is not particularly limited as long as it has high transparency required as a polarizer outer surface protective film of a liquid crystal display element, but typically an acrylic resin. , Selected from the group consisting of polycarbonate resins, polypropylene resins, cycloolefin resins and polyethylene terephthalate resins. Since these synthetic resins have excellent optical transparency and impact strength, they can be disposed on the outer layer side of the liquid crystal display element instead of triacetyl cellulose. The base material layer 2 may contain other optional components as long as the transparency and desired strength are not impaired, but preferably contains 90% by mass or more, more preferably 98% by mass or more of the synthetic resin as described above. . Examples of optional components here include ultraviolet absorbers, stabilizers, lubricants, processing aids, plasticizers, impact resistance aids, phase difference reducing agents, matting agents, antibacterial agents, and fungicides.

  The acrylic resin used for the base material layer 2 is a resin having a skeleton derived from acrylic acid or methacrylic acid. Examples of the acrylic resin include, but are not limited to, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer. Polymer, methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer, polymer having alicyclic hydrocarbon group (for example, methyl methacrylate-methacrylic acid) Acid cyclohexyl copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer), and the like. Among these acrylic resins, poly (meth) acrylate C1-6 alkyl such as poly (meth) methyl acrylate is preferable, and methyl methacrylate resin is more preferable.

  The polycarbonate resin used for the base material layer 2 is a resin composed of a compound called poly-4,4′-isopropylidene-diphenyl carbonate. This polycarbonate resin is produced from bisphenol A and carbonyl chloride in the interfacial polycondensation method, and is produced from bisphenol A and diphenyl carbonate in the transesterification method.

  The polypropylene resin used for the base material layer 2 is a resin having a skeleton derived from propylene. Although it does not specifically limit as an example of a polypropylene resin, Copolymer of propylene homopolymer or propylene, and 1 or more types of monomers selected from the group which consists of ethylene and a C4-C12 alpha olefin. A polymer etc. are mentioned.

  The cycloolefin-based resin used for the base material layer 2 is a resin having a skeleton derived from cycloolefin. Examples of cycloolefin-based resins are not particularly limited, but resins obtained by subjecting ring-opening (co) polymers of norbornene-based monomers to polymer modification such as maleic acid addition and cyclopentadiene addition as necessary are hydrogenated Examples thereof include resins obtained by addition polymerization of norbornene monomers, resins obtained by addition polymerization of norbornene monomers and olefin monomers such as ethylene and α-olefin.

  Examples of norbornene monomers used to obtain a ring-opening (co) polymer of norbornene monomers include, for example, norbornene, 2-norbornene, 5-methyl-2-norbornene, and 5,5-dimethyl-2-norbornene. 5-ethyl-2-norbornene, 5-butyl-2-norbornene, 5-ethylidene-2-norbornene, 5-methoxycarbonyl-2-norbornene, 5-cyano-2-norbornene, 5-methyl-5-methoxycarbonyl -2-norbornene, 5-phenyl-2-norbornene, 5-phenyl-5-methyl-norbornene and the like. As the polymerization catalyst used for the ring-opening polymerization, a tungsten, molybdenum, or chromium catalyst called a metathesis polymerization catalyst is preferably used.

  The polyethylene terephthalate resin used for the base material layer 2 is a polymer obtained by the reaction of terephthalic acid and ethylene glycol. The polyethylene terephthalate resin may contain other comonomers, but those having a polyethylene terephthalate repeating unit of 80 mol% or more are preferably used. Polyethylene terephthalate is prepared by, for example, charging dimethyl terephthalate and ethylene glycol into a reactor, performing an ester exchange reaction while gradually raising the internal temperature, then transferring the reaction product to the polymerization reactor, and performing a polymerization reaction under high temperature vacuum Can be generated.

  The thickness of the base material layer 2 is preferably 10 μm or more and 200 μm or less, more preferably 20 μm or more and 100 μm or less. By setting the thickness of the base material layer 2 to 10 μm or more, moderate strength and rigidity can be obtained, and it becomes possible to produce a film stably and easily, and when the primer layer 3 and the cellulose ester layer 4 are formed. Handleability is also improved. On the other hand, when the thickness of the base material layer 2 is 200 μm or less, the line speed, productivity, and controllability at the time of manufacture are enhanced.

  As the base material layer 2, one having an arithmetic average surface roughness (Ra) of 0.02 or more and 0.06 or less can be used. Further, the base material layer 2 can be subjected to a mat treatment as necessary. The arithmetic average surface roughness (Ra) of the base material layer subjected to such a mat treatment is preferably 0.07 or more and 2 or less, more preferably 0.1 or more and 1 or less. By controlling the surface roughness of the base material layer in such a range, scratches are prevented in the processing after the film raw fabric is manufactured, and the handleability is improved. Furthermore, when the base material layer is located on the uppermost surface (display surface side) of the liquid crystal display element, high antireflection performance can be obtained, and when located on the lowermost layer, sticking with other layers is effective. To be prevented. Moreover, generally, when winding up the manufactured film original fabric, it is necessary to prevent blocking by embossing (knurling) both ends in the width direction of the film. When a knurling process is performed on a film, the processing points at both ends of the film cannot be used, so that part must be cut and discarded. In the film winding operation, masking may be performed with a protective film in order to prevent damage. However, by making the arithmetic average surface roughness of the base material layer within the predetermined range as described above, blocking can be prevented without performing a knurling treatment, so that the manufacturing process is simplified and the film width direction is reduced. Both end portions can be used, and a long winding can be performed without causing film failure. Moreover, when the base material layer has an appropriate surface roughness, scratches during winding are effectively suppressed, and masking as described above becomes unnecessary.

  The retardation value (Re) of the base material layer 2 is preferably −15 nm to 15 nm, more preferably −5 nm to 5 nm. Since the base material layer has such a small retardation, the action of converting the polarization direction of the transmitted light by the polarizer outer surface protective film provided with this base material layer is suppressed, and the polarization direction of the polarizer in the transmission axis direction of the polarizer is suppressed. The influence which a polarizer outer surface protective film exerts on optimization and controllability can be suppressed. Here, the “retardation value (Re)” means the fast axis direction and the slow axis direction orthogonal to the crystal axis direction on the plane of the base layer, and the thickness of the base layer. Is a value calculated by Re = (ny−nx) d, where d is the refractive index in the x-direction and y-direction is nx and ny (nx ≠ ny).

  Although the manufacturing method of the base material layer 2 is not particularly limited, for example, additives such as a synthetic resin flake raw material and a plasticizer are mixed by a conventionally known mixing method to obtain a thermoplastic resin composition in advance, and then an optical film. Can be manufactured. This thermoplastic resin composition can be obtained, for example, by pre-blending with a mixer such as an omni mixer and then extruding and kneading the resulting mixture. In this case, the kneader used for extrusion kneading is not particularly limited, and for example, a conventionally known kneader such as an extruder such as a single screw extruder or a twin screw extruder or a pressure kneader can be used. .

  Examples of the film forming method for the base material layer 2 include known methods such as a solution casting method (solution casting method), a melt extrusion method, a calendar method, and a compression molding method. Among these, the solution casting method (solution casting method) and the melt extrusion method are preferable. At this time, a thermoplastic resin composition extruded and kneaded in advance may be used, or another additive such as a synthetic resin and a plasticizer is separately dissolved in a solvent to obtain a uniform mixed solution, and then a solution cast. You may use for the film forming process of a method (solution casting method) and a melt extrusion method.

  Solvents used in the solution casting method (solution casting method) include, for example, chlorinated solvents such as chloroform and dichloromethane; aromatic solvents such as toluene, xylene, benzene, and mixed solvents thereof; methanol, ethanol, and isopropanol And alcohol solvents such as n-butanol and 2-butanol; methyl cellosolve, ethyl cellosolve, butyl cellosolve, dimethylformamide, dimethyl sulfoxide, dioxane, cyclohexanone, tetrahydrofuran, acetone, methyl ethyl ketone (MEK), ethyl acetate, diethyl ether, etc. It is done. These solvents may be used alone or in combination of two or more. Examples of the apparatus for performing the solution casting method (solution casting method) include a drum casting machine, a band casting machine, and a spin coater.

  Examples of the melt extrusion method include a T-die method and an inflation method. The molding temperature of the film during melt extrusion is preferably 150 ° C. or higher and 350 ° C. or lower, more preferably 200 ° C. or higher and 300 ° C. or lower. When film-forming by the T-die method, a T-die is attached to the tip of a known single-screw extruder or twin-screw extruder, and the film extruded into a film shape is wound to obtain a roll film. Under the present circumstances, it is also possible to set it as a uniaxial stretching process by adjusting the temperature of a winding roll suitably, and adding extending | stretching to an extrusion direction. It is also possible to add steps such as sequential biaxial stretching and simultaneous biaxial stretching by adding a step of stretching the film in a direction perpendicular to the extrusion direction.

  The base material layer 2 may be an unstretched film or a stretched film. When extending | stretching, a uniaxially stretched film may be sufficient and a biaxially stretched film may be sufficient. When a biaxially stretched film is used, it may be biaxially stretched simultaneously or sequentially biaxially stretched. In the case of biaxial stretching, the mechanical strength is improved and the film performance is improved.

  As the stretching temperature when the stretching step is performed, it is preferably performed in the vicinity of the glass transition temperature of the thermoplastic resin composition of the film raw material, specifically, (glass transition temperature-30) ° C. to (glass transition temperature + 100) ° C. It is preferable to carry out at (Glass transition temperature−20) ° C. to (Glass transition temperature + 80) ° C. When the stretching temperature is lower than (glass transition temperature-30) ° C., a sufficient stretching ratio cannot be obtained, which is not preferable. If the stretching temperature is higher than (glass transition temperature + 100) ° C., resin flow occurs, and stable stretching cannot be performed.

  The draw ratio defined by the area ratio can be preferably in the range of 1.1 to 25 times, more preferably in the range of 1.3 to 10 times. If the draw ratio is less than 1.1, it is not preferable because it does not lead to an improvement in toughness accompanying the drawing. When the draw ratio is larger than 25, the effect of increasing the draw ratio is not recognized.

  The stretching speed (one direction) is preferably in the range of 10 to 20000% / min, more preferably in the range of 100 to 10000% / min. If it is slower than 10% / min, it takes time to obtain a sufficient draw ratio, and the production cost is increased, which is not preferable. If it is faster than 20000% / min, the stretched film may be broken, which is not preferable. Furthermore, in order to stabilize the optical isotropy and mechanical properties of the base material layer 2, heat treatment (annealing) or the like can be performed after the stretching treatment.

  Although it does not specifically limit as a plasticizer, The functional group which can interact with a synthetic resin by a hydrogen bond etc. is generated so that a haze may be generated in the base material layer 2, or it may not bleed out or volatilize from the base material layer 2. It is preferable to have. Examples of such plasticizers include, but are not limited to, phosphate ester plasticizers, phthalate ester plasticizers, trimellitic acid ester plasticizers, pyromellitic acid plasticizers, polyhydric alcohol plasticizers. Glycolate plasticizers, citrate plasticizers, fatty acid ester plasticizers, carboxylic acid ester plasticizers, polyester plasticizers, and the like.

  The primer layer 3 is not particularly limited as long as it contains chemical species having chemical affinity with both the base material layer 2 and the cellulose ester layer 4, but is preferably formed from an aqueous latex. The aqueous latex is composed of a lipophilic component composed of a single unsaturated monomer polymer or a copolymer of two or more unsaturated monomers. As the aqueous latex, one synthesized by a general emulsion polymerization method may be used, or a commercially available latex may be used. Water is used as the main solvent of the aqueous latex, but a small amount of an organic solvent miscible with water may be used. You may add arbitrary components, such as an antistatic agent, surfactant, a thickener, a stabilizer, a crosslinking agent, a curing catalyst, to an aqueous latex suitably. The solid content of the aqueous latex is typically 20% or more and 50% or less. The particle diameter of the polymer particles constituting the aqueous latex is preferably 0.005 μm or more and 0.5 μm from the viewpoint of dispersion stability.

  Specific examples of the unsaturated monomer include acrylic acid, methacrylic acid, a substituent such as methyl group, ethyl group, n-propyl group, isopropyl group, n-butyl group, sec-butyl group, amyl group, hexyl group, 2-ethylhexyl group, octyl group, tert-octyl group, dodecyl group, 2-chloroethyl group, 2-bromoethyl group, 4-chlorobutyl group, cyanoethyl group, 2-acetoxyethyl group, dimethylaminoethyl group, benzyl group, methoxybenzyl Group, 2-chlorocyclohexyl group, cyclohexyl group, furfuryl group, tetrahydrofurfuryl group, phenyl group, 5-hydroxypentyl group, 2,2-dimethyl-3-hydroxypropyl group, 2-methoxyethyl group, glycidyl group, aceto Acetoxyethyl group, 3-methoxybutyl group, 2-eth Siethyl group, 2-iso-propoxy group, 2-butoxyethyl group, 2- (2-methoxyethoxy) ethyl group, 2- (2-butoxyethoxy) ethyl group, ω-methoxy oligooxyethylene group, ω-hydroxy oligo Acrylic acid derivatives and methacrylic acid derivatives having an oxyethylene group, 1-bromo-2-methoxyethyl group, or 1,1-dichloro-2-ethoxyethyl group;

  Acrylamide, methacrylamide, substituents are methyl, ethyl, n-propyl, n-butyl, tert-butyl, n-octyl, dodecyl, cyclohexyl, benzyl, hydroxymethyl, methoxyethyl Acrylamide derivatives, methacrylamide derivatives, N, N-dimethyl groups, or acrylamide derivatives having N, N-diethyl groups, which are N-monosubstituted derivatives having a group, dimethylaminopropyl group, phenyl group, acetoacetoxypropyl group or cyanoethyl group , Methacrylamide derivatives;

  Vinyl esters such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate, vinyl caprate, vinyl chloroacetate, vinyl methoxyacetate, vinyl phenylacetate, vinyl benzoate, vinyl salicylate; dicyclopentadiene, ethylene , Olefins such as propylene, 1-butene, vinyl chloride, vinylidene chloride, isoprene, chloroprene, butadiene, 2,3-dimethylbutadiene; styrene, methylstyrene, dimethylstyrene, trimethylstyrene, ethylstyrene, isopropylstyrene, chloromethylstyrene , Styrenes such as methoxystyrene, acetoxystyrene, chlorostyrene, dichlorostyrene, bromostyrene, vinyl benzoic acid methyl ester; crotonic acid Crotonic esters such as chill and hexyl crotonate; itaconic acid monomethyl ester, itaconic acid dimethyl, itaconic acid monobutyl ester, itaconic acid diethyl, itaconic acid dibutyl and other itaconic acid esters; diethyl fumarate, dimethyl fumarate, fumarate Fumaric acid esters such as dibutyl acid; vinyl ketones such as methyl vinyl ketone, phenyl vinyl ketone, methoxyethyl vinyl ketone; N-vinyl pyridine and 2- and 4-vinyl pyridine, vinyl imidazole, vinyl oxazole, vinyl triazole, N- Heterocycle-containing vinyl monomers such as vinyl-2-pyrrolidone; and unsaturated nitriles such as acrylonitrile and methacrylonitrile.

  The aqueous latex is applied to the base material layer 2 using a known dip coating method, air knife coating method, curtain coating method, roller coating method, wire bar coating method, gravure coating method, extrusion coating method (die coating method) or the like. Can be applied. Next, the primer layer 3 can be formed by drying the applied aqueous latex. The thickness of the primer layer 3 is preferably 0.01 μm or more and 1 μm or less, and more preferably 0.05 μm or more and 0.1 μm or less.

  The cellulose ester constituting the cellulose ester layer 4 is not particularly limited as long as it is saponified with an alkali to produce a hydroxyl group, but is a group consisting of triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Is preferably selected from. These cellulose esters generate a hydroxyl group which is a hydrophilic group by saponification with an alkali, thereby increasing the affinity with a polarizer made of polyvinyl alcohol which is a hydrophilic resin, and can be reliably bonded. .

  The total thickness of the primer layer 3 and the cellulose ester layer 4 is preferably 0.02 μm or more and 4 μm or less, and more preferably 0.05 μm or more and 2 μm or less. By making the total thickness of the primer layer 3 and the cellulose ester layer 4 0.02 μm or more, adhesion between the hydroxyl group generated by saponification of this cellulose ester and the polyvinyl alcohol constituting the polarizer is ensured. . Moreover, by making the total thickness of the primer layer 3 and the cellulose ester layer 4 4 μm or less, the thickness of the polarizer outer surface protective film 1 can be kept sufficiently thin, and the entire polarizing plate including the polarizer outer surface protective film 1 can be maintained. An increase in thickness can be suppressed.

  The solvent of the cellulose ester coating solution for forming the cellulose ester layer 4 is not particularly limited as long as it is an organic solvent that sufficiently dissolves the cellulose ester. For example, dioxane, acetone, methyl ethyl ketone, N, N-dimethylformamide, acetic acid Methyl, ethyl acetate, trichloroethylene, methylene chloride, ethylene chloride, tetrachloroethane, trichloroethane, chloroform and the like are used. Moreover, you may add a ultraviolet absorber, a slip agent, a mat agent, an antistatic agent, a crosslinking agent, an activator, etc. to the cellulose-ester coating liquid for forming the cellulose-ester layer 4, if desired. In particular, a crosslinking agent is preferable for promoting adhesion with polyvinyl alcohol constituting the polarizer. Examples of such crosslinking agents include polyvalent epoxy compounds, aziridine compounds, isocyanate compounds, light vanes, boron compounds and the like.

  The cellulose ester coating solution for forming the cellulose ester layer 4 can be applied to the primer layer 3 using a known technique such as a gravure coater, a dip coater, a reverse roll coater, or an extrusion coater. A method of drying after applying such a coating solution is not particularly limited, and known means can be used, but it is preferable that the amount of residual solvent after drying is 5% by mass or less. If the amount of residual solvent is large, bubbles may be formed at the adhesive interface in the drying process after laminating the polarizer outer surface protective film on the polarizer, which is not preferable.

  In the polarizer outer surface protective film 1, the surface of the base material layer 2 on the side that is not surface-treated with the cellulose ester via the primer layer 3 is arbitrarily selected from various functional layers such as an antiglare layer, an antireflection layer, You may coat | cover with antireflection layers, such as a glare layer and a low refractive index layer, an antistatic layer, a hard-coat layer (cured resin layer), an optical compensation layer. For example, when the polarizer outer surface protective film further includes an antiglare layer (antireflection layer), the antiglare function can be exhibited in addition to the protective function for the polarizer. Moreover, the protective function with respect to a polarizer is strengthened because a polarizer outer surface protective film further includes a hard coat layer.

  As such an antiglare layer, for example, a technique for forming an uneven structure on the film surface by an embossing method or a coating liquid in which particles are mixed in a binder matrix forming material is applied to the film surface, A technique for forming a concavo-convex structure by dispersing particles can be used. Moreover, as a hard-coat layer, what was formed, for example from active ray curable resin can be used. Examples of such actinic radiation curable resins include urethane acrylate resins, polyester acrylate resins, epoxy acrylate resins, polyol acrylate resins, and epoxy resins.

  As described above, according to the polarizer outer surface protective film of the present invention, the base material whose inner surface is surface-treated with a cellulose ester via a primer layer so as to facilitate adhesion with a polarizer made of polyvinyl alcohol. When the cellulose ester is provided with a layer and a hydroxyl group is generated through a saponification treatment with an alkali described later, the affinity and adhesiveness with polyvinyl alcohol, which is a hydrophilic resin constituting the polarizer, are effectively improved.

  The polarizing plate 5 in FIG. 2 includes the polarizer outer surface protective film 1 in FIG. 1 on the outer surface side (the side in the A direction shown in the figure) of the polarizer 7 made of polyvinyl alcohol, It has the structure provided with the polarizer inner surface protective film 6 which consists of a cellulose ester used from. The polarizer 7 and the polarizer outer surface protective film 1 and the polarizer 7 and the polarizer inner surface protective film 6 are bonded by an adhesive (not shown).

  As the polarizer 7, a polyvinyl alcohol resin film dyed with a dichroic substance (for example, iodine or dichroic dye) and uniaxially stretched is used. The polymerization degree of polyvinyl alcohol constituting the polyvinyl alcohol resin film is preferably 100 or more and 5000 or less, more preferably 1400 or more and 4000 or less. The polyvinyl alcohol resin film can be formed by a known method (for example, a casting method or casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast into a film). The thickness of the polarizer 7 varies depending on the purpose and application of the LCD in which the polarizing plate 5 is used, but is typically 5 μm or more and 100 μm or less. The polarizer 7 may contain an optional component other than the polyvinyl alcohol resin and the dichroic material as long as the polarizing function and optical transparency are not impaired.

  As a typical manufacturing method of the polarizer 7, a series of manufacturing steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps are employed for the polyvinyl alcohol resin film. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol resin film in a solution bath used in each step. The order, number of times, and the presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing and drying can be appropriately set according to the purpose, materials used, conditions and the like. For example, the stretching process may be performed before the dyeing process or may be performed simultaneously with the swelling process. Moreover, it is preferable to perform the crosslinking treatment before and after the stretching treatment.

  The swelling step in the series of manufacturing steps of the polarizer 7 can be performed by immersing the polyvinyl alcohol resin film in a treatment bath filled with water. Glycerin, potassium iodide, or the like can be appropriately added to the treatment bath. Typically, the temperature of the treatment bath in the swelling process is about 20 to 60 ° C., and the immersion time in the treatment bath is about 0.1 to 10 minutes. The dyeing step can be performed by immersing the polyvinyl alcohol resin film in a treatment bath containing a dichroic substance such as iodine. As a solvent used for the solution of the treatment bath, water is generally used. The dichroic substance is used at a ratio of 0.1 to 1.0 part by mass with respect to 100 parts by mass of the solvent. Typically, the temperature of the treatment bath in the dyeing process is about 20 to 70 ° C., and the immersion time is about 1 to 20 minutes.

  The crosslinking step can be performed by immersing the dyed polyvinyl alcohol resin film in a treatment bath containing a crosslinking agent. Examples of the crosslinking agent include boron compounds such as boric acid, glyoxal, and glutaraldehyde. As a solvent used for the solution of the treatment bath, water is generally used. Typically, the temperature of the treatment bath in the crosslinking step is about 20 to 70 ° C., and the immersion time is about 1 second to 15 minutes. The stretching process may be performed at any stage. The draw ratio of the polyvinyl alcohol resin film is preferably 5 times or more. As the stretching method, for example, a wet stretching method can be employed. As the solution of the treatment bath in this case, a solution in which various metal salts, iodine, boron or zinc compounds are added to water or an organic solvent is preferable.

  The washing step can be performed by immersing the polyvinyl alcohol resin film that has been subjected to various treatments in a washing bath. By this water washing step, unnecessary residues of the polyvinyl alcohol resin film can be washed away. The washing bath may be pure water or an aqueous solution of iodide (potassium iodide, sodium iodide, etc.). The temperature of the washing bath is preferably 10 to 60 ° C. Typically, the immersion time is 1 second to 1 minute. The number of times of washing with water may be one time or multiple times. As a drying process, natural drying, ventilation drying, and heat drying are employable, for example. Typically, the drying temperature is 20-80 ° C and the drying time is 1-10 minutes. The polarizer 7 can be manufactured by performing each of the above steps.

  A conventionally used polarizer inner surface protective film 6 made of cellulose ester is prepared by dissolving a cellulose ester flake raw material and a plasticizer in methylene chloride to form a viscous liquid, and dissolving the plasticizer in this to form a dope. It is cast from a melt extruder onto a continuously rotating metal belt such as stainless steel, dried, peeled off from the belt in a dry state, dried, wound up and manufactured. As the cellulose ester, those selected from the group consisting of triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate and cellulose acetate butyrate are preferable, and triacetyl cellulose is particularly preferable.

  The polarizer outer surface protective film 1 needs to saponify the cellulose ester layer 4 with an alkali before bonding with the polarizer 7. By this saponification, the ester group of the cellulose ester is converted to a hydroxyl group which is a hydrophilic group, and thereby, the chemical reaction between the polarizer outer surface protective film 1 and the polarizer 7 formed of polyvinyl alcohol which is a hydrophilic resin. Affinity is enhanced and the mutual adhesiveness is remarkably improved.

  As the alkaline aqueous solution used for the saponification treatment, for example, an aqueous solution of sodium hydroxide, potassium hydroxide, calcium hydroxide, lithium hydroxide, or the like can be used. The concentration of these metal hydroxides is generally 5% by mass or more and 40% by mass or less. Moreover, it is preferable that the temperature of a saponification process is 10 degreeC or more and 80 degrees C or less. When the concentration of the metal hydroxide is 5% by mass or less or when the temperature of the saponification treatment is 10 ° C. or less, the time required for the saponification treatment becomes long, which is not preferable. The saponification treatment is performed by immersing the polarizer outer surface protective film 1 in an alkaline aqueous solution bath as described above for an appropriate time.

  The polarizer outer surface protective film 1 subjected to the saponification treatment and the polarizer 7 made of polyvinyl alcohol are bonded together by an apparatus 8 schematically shown in FIG. An apparatus 8 for laminating a plurality of films shown in FIG. 3 includes a nip 9 for supplying a polarizer 7, a nip 10 for supplying a polarizer outer surface protective film 1, and an adhesive. And a nip 12 for pressing and joining the polarizer 7 and the polarizer outer surface protective film 1 through an adhesive.

  Examples of the adhesive used for bonding the cellulose ester layer 4 and the polarizer 7 of the polarizer outer surface protective film 1 by the device 8 include polyvinyl alcohol adhesives such as polyvinyl alcohol and polyvinyl butyral, and butyl acrylate. Examples include vinyl latex. Usually, these adhesives are used as an aqueous solution. The solid content concentration in the resin solution of the adhesive is preferably from 0.1 to 15% by mass in consideration of coating property and storage stability. Moreover, as a viscosity of the resin solution of an adhesive agent, the range of 1-50 mPa * s is preferable, for example.

  In the apparatus 8, the film-like polarizer 7 supplied from the nip 9 and the saponified polarizer outer surface protective film 1 supplied from the nip 10 are sent in a direction toward the nip 12, and the film is interposed between these films. An appropriate amount of adhesive is supplied so as to be sandwiched, and then pressed by the nip 12, whereby the polarizer 7 and the cellulose ester layer 4 of the polarizer outer surface protective film 1 are bonded, and the polarizer 7 is attached to one side of the polarizer 7. A structure in which the outer surface protective film 1 is laminated is obtained. Subsequently, the polarizing plate 5 is obtained by laminating | stacking the polarizer inner surface protective film 6 also on the surface of the polarizer 7 in which the polarizer outer surface protective film 1 is not laminated | stacked using the same means. The thickness of the polarizing plate 5 is typically 10 μm or more and 100 μm or less.

  As described above, according to the polarizing plate having the polarizer outer surface protective film according to the present invention, the base layer made of synthetic resin disposed on the outer surface side of the polarizer made of polyvinyl alcohol is subjected to an easy adhesion treatment. Therefore, the adhesiveness and peeling durability between the polarizer made of polyvinyl alcohol and the polarizer outer surface protective film are enhanced, thereby improving the strength and handleability of the polarizing plate. Further, by using a polarizer inner surface protective film made of cellulose ester having a small birefringence (that is, non-orientated) on the inner surface side of the polarizer, the polarizer can be obtained without affecting the performance of the liquid crystal molecules. The protective function can be provided.

  The liquid crystal display element 13 of FIG. 4 includes the polarizing plate 5 of FIG. 2 according to the present invention via an adhesive layer 17 on both surfaces of a liquid crystal cell 14 in which a liquid crystal layer 16 is sandwiched between transparent medium layers 15 (for example, glass). It is comprised by bonding together (it consists of the base material layer 2, the primer layer 3, the cellulose-ester layer 4, the polarizer inner surface protective film 6, and the polarizer 7). The polarizer outer surface protective film (base material layer 2, primer layer 3 and cellulose ester layer 4) according to the present invention is disposed exclusively on the outer surface side of the polarizer 7, and is a polarizer inner surface protective film made of cellulose ester which has been conventionally used. 6 is disposed on the inner surface side of the polarizer 7 (the side in the A direction shown is the outer surface side). The materials constituting the liquid crystal layer 16, the transparent medium layer 15, and the adhesive layer 17 of the liquid crystal cell 14 are not particularly limited, and known materials can be used. In the liquid crystal display element, the polarizing plate 5 of FIG. 2 (the polarizing plate according to the present invention) is used on one side of the liquid crystal cell, and another polarizing plate according to the prior art is used on the other side of the liquid crystal cell. Good.

  Since the liquid crystal display element provided with the polarizing plate in which the polarizer outer surface protective film according to the present invention is disposed, the polarizer outer surface protective film has been subjected to an easy adhesion treatment, and therefore, the adhesion between the polarizer and the polarizer outer surface protective film, The durability against peeling is high, and the strength and handling of the polarizing plate are excellent. Therefore, various characteristics of the liquid crystal display element are continuously and stably exhibited over a long period of time, and the reliability of the entire device is improved.

  EXAMPLES Hereinafter, although this invention is explained in full detail based on an Example, this invention is not interpreted limitedly based on description of this Example.

[Formation of transparent synthetic resin base material layer]
An ethylene glycol slurry to which beaded silica was added was prepared, and this ethylene glycol slurry was heat-treated at 190 ° C. for 2 hours. Subsequently, this was subjected to a transesterification reaction with dimethyl terephthalate, followed by polycondensation to obtain ethylene terephthalate pellets. Produced. Next, the resin obtained from the pellets was vacuum-dried at 180 ° C. for 3 hours, and then supplied to an extruder and melted by heating at 310 ° C. Subsequently, the resin melted from the extruder was extruded into a sheet and cooled and solidified on a casting drum having a surface temperature of 30 ° C., thereby producing an unstretched film. Next, the above-mentioned unstretched film was stretched 4 times in the longitudinal direction at 100 ° C. by roll stretching, and further stretched 4 times in the width direction at 110 ° C. using a tenter. Subsequently, this biaxially stretched film was crystallized by heat treatment at 235 ° C. (crystallization temperature) for 5 seconds to produce a polyethylene terephthalate resin film having a thickness of 40 μm. This polyethylene terephthalate resin film is designated as sample A.

[Formation of primer layer and cellulose ester layer]
As an aqueous latex, an aqueous dispersion latex (mass ratio 30/20/25/25) of a butyl acrylate / t-butyl acrylate / styrene / 2-hydroxyethyl acrylate copolymer with a solid content of 30% by mass was used. The primer layer was coated on the surface of the polyethylene terephthalate resin film of Sample A and dried to form a primer layer having a thickness of 0.5 μm. Next, using a dip coater, a triethyl cellulose solution (20% by mass) was applied to the primer layer, and the methyl ethyl ketone was dried to form a triacetyl cellulose layer. The primer layer and the triacetyl cellulose layer A polarizer protective film having a total thickness of 2.0 μm was obtained. Furthermore, the saponification process was performed with respect to the triacetyl cellulose layer at 40 degreeC using sodium hydroxide aqueous solution (concentration 20 mass%). This saponified polarizer protective film is designated as Sample B.

[Formation of polarizer]
A polyvinyl alcohol film having a thickness of 200 μm was uniaxially stretched (temperature 110 ° C., stretch ratio 5 times) to obtain a film having a thickness of 40 μm. This film was immersed in an aqueous solution containing 0.15 g of iodine and 10 g of potassium iodide for 60 seconds, and then immersed in an aqueous solution at 68 ° C. containing 12 g of potassium iodide and 7.5 g of boric acid. This was washed with water and dried to obtain a polarizer.

[Example]
The saponified polarizer protective film of Sample B and the above polarizer are cut into a size of 18 cm × 5 cm, and these are overlapped via an adhesive that is a polyvinyl alcohol aqueous solution having a solid content concentration of 2% by mass. It was bonded together while removing excess adhesive and air bubbles. This was inserted into a laminator pressurized to 2 kg / cm ² and further dried at 80 ° C. to obtain a laminate 1. In this bonding, the triacetylcellulose layer of Sample B and the polarizer were adhered.

[Comparative example]
The polyethylene terephthalate resin film of Sample A and the above polarizer were bonded together by the same means as in the above Example to obtain a laminate 2.

  The laminated bodies 1 and 2 obtained above were evaluated for the characteristics regarding the initial adhesiveness and durability by the following methods.

(1) Initial adhesion The two layers of the laminate were peeled off by hand, and evaluated according to the following three stages according to the degree of occurrence of material destruction.
Good: Material destruction occurs.
Slightly poor: Some material destruction occurs, but the peeling area between the sample and the polarizer is large.
Poor: The sample and the polarizer are completely peeled off.

(2) Durability The laminate was allowed to stand at 75 ° C. under a condition of 90% RH for 500 hours, the appearance change was observed, and the width of peeling from the end portion was measured. The evaluation criteria were as follows.
Good: Within 0.5 mm Slightly poor: 0.5 mm or more and 1.5 mm or less Bad: 1.5 mm or more

  When an initial adhesion test was performed on the laminate 1 of the example, it was found that material destruction occurred and the initial adhesion was good. Moreover, when the durability test was done with respect to the laminated body 1 of an Example, peeling was 0.3 mm and the peeling durability under severe conditions was also excellent. On the other hand, when an initial adhesion test was performed on the laminate 2 of the comparative example, it was found that the sample B peeled off from the polarizer without applying a large force, and the initial adhesion was poor. Moreover, when the durability test was done with respect to the laminated body 2 of the comparative example, peeling was 2.0 mm and the peeling durability was inferior. Thus, the protective film for the outer surface of the polarizer according to the present invention includes a base material layer on which one surface is surface-treated with a cellulose ester, and thus the base material layer that has not been subjected to such surface treatment. Compared with the film which consists of, the adhesive force with respect to polyvinyl alcohol and peeling durability are improved significantly.

  Since the liquid crystal display element using the polarizing plate provided with the polarizer outer surface protective film according to the present invention is securely bonded between the polarizer outer surface protective film and the polarizer, the liquid crystal display element and the liquid crystal display element are provided. Reliability of the entire electronic equipment is increased. Therefore, such a liquid crystal display element can be used in various fields ranging from small products such as calculators and watches to large products such as automobile meters, PC monitors, and televisions.

DESCRIPTION OF SYMBOLS 1 Polarizer outer surface protective film 2 according to the present invention Transparent base material layer 3 made of synthetic resin Primer layer 4 Cellulose ester layer 5 Polarizing plate 6 Polarizer inner surface protective film 7 made of cellulose ester Polarizer 8 For producing a polarizing plate Device 9 Nip 10 Nip 11 Adhesive supply means 12 Nip 13 Liquid crystal display element 14 Liquid crystal cell 15 Transparent medium layer 16 Liquid crystal layer 17 Adhesive layer 21 Liquid crystal display element 22 Polarizing plate 23 Polarizer protective film 24 Polarizer 25 Liquid crystal cell 26 Transparent Media layer 27 Liquid crystal layer 28 Adhesive layer

Claims (7)

A polarizer outer surface protective film disposed on the outer surface side of the liquid crystal display element,
A transparent synthetic resin base material layer;
A primer layer laminated on the inner surface side of the base material layer,
A cellulose ester layer laminated on the inner surface side of the primer layer,
The primer layer is formed from an aqueous latex,
The above aqueous latex is (meth) acrylic acid, (meth) acrylic acid derivative, (meth) acrylamide, (meth) acrylamide derivative, vinyl ester, olefin, styrene, crotonic acid ester, itaconic acid ester, fumarate esters, vinyl ketones, polarizer comprising a heterocycle-containing vinyl monomers and unsaturated one from the group consisting of nitriles Ru is selected single unsaturated monomers obtained from the polymer External protective film.   The synthetic resin constituting the base material layer is at least one selected from the group consisting of acrylic resins, polycarbonate resins, polypropylene resins, cycloolefin resins, and polyethylene terephthalate resins. Polarizer outer surface protective film.   The cellulose ester constituting the cellulose ester layer is at least one selected from the group consisting of triacetyl cellulose, diacetyl cellulose, cellulose acetate propionate, and cellulose acetate butyrate. Polarizer outer surface protective film.   The polarizer outer surface protective film according to claim 1, wherein the total thickness of the primer layer and the cellulose ester layer is 0.02 μm or more and 4 μm or less.   The polarizer outer surface protective film according to any one of claims 1 to 4, further comprising an antireflection layer or a hard coat layer laminated on the outer surface side of the base material layer. A polarizer made of polyvinyl alcohol;
The polarizer outer surface protective film according to any one of claims 1 to 5, which is laminated on an outer surface of the polarizer,
A polarizer comprising: a polarizer inner surface protective film laminated on an inner surface of the polarizer. A liquid crystal cell;
A liquid crystal display device comprising: the polarizing plate according to claim 6, which is laminated on at least one surface side of the liquid crystal cell.

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