JP5828538B2 - Polarizing plate, manufacturing method thereof, optical film, and image display device - Google Patents

Description

  The present invention relates to a polarizing plate and a method for producing the same. The polarizing plate can form an image display device such as a liquid crystal display device, an organic EL display device, or a PDP alone or as an optical film obtained by laminating the polarizing plate.

  In a liquid crystal display device, it is indispensable to dispose polarizers on both sides of a glass substrate on which a liquid crystal panel surface is formed because of its image forming method. In general, a polarizer is obtained by dyeing with a polyvinyl alcohol film and a dichroic material such as iodine, followed by crosslinking using a crosslinking agent, and forming a film by uniaxial stretching. Since the polarizer is produced by stretching, it is easily contracted, and the dimensional change at a high temperature is particularly large. Moreover, since the mechanical strength of the film itself is weak, there is a problem that the film is torn. Therefore, a polarizing plate is used in which a transparent protective film such as triacetyl cellulose is bonded to both sides or one side of the polarizer to supplement the strength. The polarizing plate is manufactured by bonding a polarizer and a transparent protective film with an adhesive.

  In recent years, the use of liquid crystal display devices has been expanded, and a wide range of development has been progressing from portable terminals to large-sized TVs for home use, and respective standards have been provided according to each application. For example, in addition to requiring adhesion between the polarizer and the transparent protective film, the polarizing plate has heating dimensional stability that does not change in properties and shape even at high temperatures so that it can be applied in various environments. It has been demanded.

  As the adhesive used for bonding the polarizer and the transparent protective film, an aqueous adhesive such as a polyvinyl alcohol adhesive is preferably used. Moreover, when bonding a polarizer and a transparent protective film through the polyvinyl alcohol-based adhesive, as an easy adhesion treatment to improve adhesion, for example, a chemical treatment such as a saponification treatment or plasma is applied to the transparent protective film. An activation treatment such as a dry treatment such as a treatment or a corona treatment, or an easy-adhesive layer is formed by a coating treatment or the like.

  For example, when producing a polarizing plate, when a norbornene-type resin film is used as a transparent protective film, it has been proposed to perform plasma treatment as an easy adhesion treatment (Patent Document 1). When a cycloolefin-based resin film is used as the transparent protective film, a reactive gas composed of a monomer containing an unsaturated bond and a predetermined functional group is converted into plasma and brought into contact with the film, It has been proposed to perform surface treatment (Patent Document 2). By sticking the transparent protective film obtained by the method of patent document 1, 2 and a polarizer with an adhesive agent, the adhesiveness of the polarizing plate obtained can be improved. Patent Document 1 describes the use of a urethane-based adhesive or the like for laminating a plasma-treated norbornene resin film and a polarizer, and Patent Document 2 describes a plasma-treated cycloolefin resin film and a polarizer. It is described that a polyvinyl alcohol resin containing a carboxyl group or an acetoacetyl group is used for bonding.

  When a cellulose film such as a triacetyl cellulose film is used as the transparent protective film, it has been proposed to use a polyvinyl alcohol resin containing an acetoacetyl group as the polyvinyl alcohol adhesive (patent) Reference 3). When a triacetyl cellulose film is used as the transparent protective film, a saponification treatment is often used as an easy adhesion treatment to the transparent protective film. However, the saponification treatment involves complicated treatments such as washing with water and drying, and the use of alkalis is accompanied by danger. In addition, when the transparent protective film is saponified, the dimensional change under a heating environment is large. Moreover, higher adhesive strength is required for the polarizing plate.

JP 2006-178191 A JP 2009-073911 A JP-A-7-198945

  The present invention is a polarizing plate in which a transparent protective film using a cellulose-based film subjected to an easy adhesion treatment and a polarizer are bonded via an adhesive layer, and has a high degree of adhesive strength, and An object of the present invention is to provide a polarizing plate having good heating dimensional stability and a method for producing the same.

  Another object of the present invention is to provide an optical film in which the polarizing plate is laminated, and further to provide an image display device such as a liquid crystal display device using the polarizing plate or the optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the following polarizing plate, and have completed the present invention.

That is, the present invention is a polarizing plate in which a transparent protective film is bonded to at least one surface of a polarizer via an adhesive layer.
The transparent protective film is a cellulose film,
The surface to be bonded to the polarizer of the transparent protective film is subjected to a surface treatment by bringing a polymerizable monomer having a carbon-carbon double bond into plasma and contacting it, and
The adhesive layer is formed of an adhesive containing a modified polyvinyl alcohol-based resin containing a modified group containing at least one selected from a cationic group, an anionic group, and a nonionic group. The present invention relates to a polarizing plate.

  In the polarizing plate, a cationic group can be used as the modifying group of the modified polyvinyl alcohol resin. As the cationic group, for example, a quaternary ammonium base is suitable.

  In the polarizing plate, an anionic group can be used as the modifying group of the modified polyvinyl alcohol resin. As the anionic group, for example, at least one of a carboxyl group and a sulfonic acid group can be used.

  In the polarizing plate, a nonionic group can be used as a modifying group of the modified polyvinyl alcohol resin. As the nonionic group, for example, at least one of an acetoacetyl group, a silanol group, and a thiol group can be used.

  In the polarizing plate, acrylic acid is suitable as the polymerizable monomer.

Further, the present invention is a method for producing the polarizing plate, wherein a transparent protective film is bonded to at least one surface of a polarizer via an adhesive layer,
The at least one transparent protective film is a cellulose- based film;
The surface of the transparent protective film to be bonded to the polarizer is subjected to a surface treatment by bringing the polymerizable monomer having a carbon-carbon double bond into plasma and contacting it, and
An adhesive comprising a modified polyvinyl alcohol-based resin containing a modified group containing at least one selected from a cationic group, an anionic group and a nonionic group between the surface-treated surface of the transparent protective film and the polarizer. The present invention relates to a method for producing a polarizing plate, comprising a step of bonding to form an adhesive layer.

  The present invention also relates to an optical film in which at least one polarizing plate is laminated.

  Furthermore, this invention relates to the image display apparatus characterized by using the said polarizing plate or the said optical film.

  In the present invention, in the polarizing plate in which the polarizer and the transparent protective film are bonded via the adhesive layer, at least one side and the cellulose-based film are used as the transparent protective film, and the cellulose-based film is subjected to a predetermined surface treatment. High adhesive strength is obtained by combining and using a modified polyvinyl alcohol having a cationic group, an anionic group or nonionic group for forming the adhesive layer. The surface treatment of the cellulose film is carried out by bringing the polymerizable monomer having a carbon-carbon double bond into plasma and bringing it into contact with the cellulose film. By the surface treatment, a polymer film made of the polymerizable monomer is formed on the cellulose film. And the modified polyvinyl alcohol resin containing the said modified | denatured group is used as an adhesive agent with respect to the said polymer film. That is, in the present invention, a polarizing plate having a high degree of adhesive strength is obtained by a combination of a predetermined surface treatment (plasma treatment) for the cellulose film and the modified polyvinyl alcohol resin used as an adhesive.

  In particular, regarding the surface treatment (plasma treatment) for the transparent protective film, when acrylic acid containing a carboxyl group is used as the polymerizable monomer, the surface of the cellulose-based film is negatively charged with hydroxyl group or carboxyl group such as acrylic acid. The charged substance (−) is graft polymerized. It is considered that high adhesion is expressed from the reactivity of such a negatively charged substance (-) and a modified polyvinyl alcohol resin containing a modifying group. In particular, when the modified group of the modified polyvinyl alcohol resin is a cationic group (+), it is considered that a higher adhesion is expressed because of the high reactivity of selectively adsorbing the negatively charged substance (−).

  Further, in the polarizing plate of the present invention, since the surface treatment of the cellulose film is performed by plasma treatment, the dimensional change in the heating environment can be suppressed to be small compared with the case of performing the saponification treatment, and the heating dimensional stability can be suppressed. The property is also good. Moreover, since the surface treatment of the transparent protective film is performed by plasma treatment, it is possible to eliminate troubles and dangers such as washing and drying associated with the saponification treatment. Conventionally, when a cellulose-based film is used as a transparent protective film of a polarizing plate, as its surface treatment, saponification treatment has been performed from the high adhesive strength, but in the polarizing plate of the present invention, Even when a cellulose-based film is used, high adhesive strength can be obtained without performing a saponification treatment, and it can be suitably applied when a cellulose-based film is used as a transparent protective film.

  In the polarizing plate of the present invention, a transparent protective film subjected to a predetermined plasma treatment is attached to at least one surface of a polarizer through an adhesive layer formed of an adhesive containing a predetermined modified polyvinyl alcohol resin. Are combined.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a functional material and uniaxially stretched, polyvinyl alcohol dehydrated products, and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. The thickness of these polarizers is not particularly limited, but is generally about 1 to 80 μm.

  A polarizer obtained by dyeing a polyvinyl alcohol film with iodine and uniaxially stretching it can be produced, for example, by dyeing polyvinyl alcohol in an aqueous solution of iodine and stretching it 3 to 7 times the original length. If necessary, it can be immersed in an aqueous solution of boric acid or potassium iodide. Further, if necessary, the polyvinyl alcohol film may be immersed in water and washed before dyeing. In addition to washing the polyvinyl alcohol film surface with dirt and anti-blocking agents by washing the polyvinyl alcohol film with water, it also has the effect of preventing unevenness such as uneven coloring by swelling the polyvinyl alcohol film. is there. Stretching may be performed after dyeing with iodine, may be performed while dyeing, or may be dyed with iodine after stretching. The film can be stretched in an aqueous solution of boric acid or potassium iodide or in a water bath.

  As a material for forming the transparent protective film provided on one side or both sides of the polarizer, a material excellent in transparency, mechanical strength, thermal stability, moisture barrier property, isotropy and the like is preferable. For example, polyester polymers such as polyethylene terephthalate and polyethylene naphthalate, cellulose polymers such as diacetyl cellulose and triacetyl cellulose, acrylic polymers such as polymethyl methacrylate, styrene such as polystyrene and acrylonitrile / styrene copolymer (AS resin) -Based polymer, polycarbonate-based polymer and the like. In addition, polyethylene, polypropylene, polyolefins having a cyclo or norbornene structure, polyolefin polymers such as ethylene / propylene copolymers, vinyl chloride polymers, amide polymers such as nylon and aromatic polyamide, imide polymers, sulfone polymers , Polyether sulfone polymer, polyether ether ketone polymer, polyphenylene sulfide polymer, vinyl alcohol polymer, vinylidene chloride polymer, vinyl butyral polymer, arylate polymer, polyoxymethylene polymer, epoxy polymer, or the above Polymer blends and the like are also examples of polymers that form the transparent protective film. One or more kinds of arbitrary appropriate additives may be contained in the transparent protective film. Examples of the additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, a coloring inhibitor, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the thermoplastic resin in the transparent protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. . When content of the said thermoplastic resin in a transparent protective film is 50 weight% or less, there exists a possibility that the high transparency etc. which a thermoplastic resin originally has cannot fully be expressed.

  Moreover, as a transparent protective film, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007), for example, (A) thermoplastic resin which has a substituted and / or unsubstituted imide group in a side chain, ( B) Resin compositions containing thermoplastic resins having substituted and / or unsubstituted phenyl and nitrile groups in the side chains. A specific example is a film of a resin composition containing an alternating copolymer composed of isobutylene and N-methylmaleimide and an acrylonitrile / styrene copolymer. As the film, a film made of a mixed extruded product of the resin composition or the like can be used. Since these films have a small phase difference and a small photoelastic coefficient, problems such as unevenness due to the distortion of the polarizing plate can be eliminated, and since the moisture permeability is small, the humidification durability is excellent.

  In the polarizing plate of the present invention, a cellulose-based film using a cellulose-based polymer as a forming material is used as the transparent protective film on at least one side of the one side or both sides.

  The cellulosic polymer is specifically an ester of cellulose and a fatty acid. Specific examples of such a cellulose polymer include triacetyl cellulose, diacetyl cellulose, tripropionyl cellulose, dipropionyl cellulose and the like. Among these, triacetyl cellulose is particularly preferable. Many products of triacetylcellulose are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of triacetyl cellulose include trade names “UV-50”, “UV-80”, “SH-80”, “TD-80U”, “TD-TAC”, and “UZ” manufactured by Fujifilm Corporation. -TAC "and" KC series "manufactured by Konica. In general, these triacetyl celluloses have an in-plane retardation (Re) of almost zero, but a thickness direction retardation (Rth) of about 60 nm or less.

  In addition, the cellulose film with a small thickness direction retardation is obtained by processing the said cellulose polymer, for example. For example, a base film such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, at 80 to 150 ° C. for about 3 to 10 minutes). ) And then peeling the base film; a solution obtained by dissolving norbornene resin, (meth) acrylic resin, etc. in a solvent such as cyclopentanone, methyl ethyl ketone, etc. is applied to a general cellulose resin film and dried by heating ( For example, a method of peeling the coated film after 80 to 150 ° C. for about 3 to 10 minutes is mentioned.

  Moreover, as a cellulose film with a small thickness direction retardation, the fatty acid cellulose resin film which controlled the fat substitution degree can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8. Preferably, the Rth can be reduced by controlling the acetic acid substitution degree to 1.8 to 2.7. Rth can be controlled to be small by adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, acetyltriethyl citrate to the fatty acid-substituted cellulose resin. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid cellulose resin.

  Although the thickness of a transparent protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable.

  In addition, when providing a transparent protective film on both surfaces of a polarizer, the transparent protective film which consists of the same polymer material may be used by the front and back, and the transparent protective film which consists of a different polymer material etc. may be used.

  A functional layer such as a hard coat layer, an antireflection layer, an antisticking layer, a diffusion layer or an antiglare layer can be provided on the surface of the transparent protective film to which the polarizer is not adhered. The functional layers such as the hard coat layer, antireflection layer, antisticking layer, diffusion layer and antiglare layer can be provided on the transparent protective film itself, and are provided separately from the transparent protective film. You can also.

  As the cellulose-based film used as the transparent protective film, a film whose surface to be bonded to a polarizer is surface-treated by bringing a polymerizable monomer having a carbon-carbon double bond into plasma and contacting it is used. When a cellulose film is provided on both sides of a polarizer, the surface treatment may be applied to at least one cellulosic film, or may be applied to a cellulosic film on both sides. May be given only.

  The polymerizable monomer having a carbon-carbon double bond preferably contains a functional group, and examples of the functional group include a carboxyl group, a hydroxyl group, an acetyl group, a glycidyl group, an epoxy group, and an ester group having 1 to 10 carbon atoms. , Sulfone group, aldehyde group and the like. Among these functional groups, a carboxyl group is particularly preferable. Examples of the carbon-carbon double bond include a (meth) acryloyl group, a vinyl group, and a (meth) allyl group. The (meth) acryloyl group is an acryloyl group and / or a methacryloyl group, and “(meth)” in the present invention has the same meaning.

  Examples of the polymerizable monomer containing a carboxyl group include (meth) acrylic acid, itaconic acid, maleic acid, fumaric acid, crotonic acid, carboxyethyl (meth) acrylate, carboxypentyl (meth) acrylate, and 2- (meth) acryloylpropion. Examples include acids. Examples of the polymerizable monomer containing a hydroxyl group include ethylene glycol (meth) acrylate, (meth) allyl alcohol, hydroxyethyl (meth) acrylate, and the like. Examples of the polymerizable monomer containing an acetyl group include vinyl acetate. Examples of the polymerizable monomer containing a glycidyl group include glycidyl (meth) acrylate. Examples of the polymerizable monomer containing an ester group include methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-butyl (meth) acrylate, t-butyl (meth) acrylate, Examples thereof include 2-ethylhexyl (meth) acrylate and octyl (meth) acrylate. Examples of the polymerizable monomer containing an aldehyde group include (meth) acrylaldehyde and crotonaldehyde. The said polymerizable monomer can be used 1 type or in combination of 2 or more types.

  The polymerizable monomer having a carbon-carbon double bond is preferably a polymerizable monomer containing a carboxyl group, more preferably acrylic acid or methacrylic acid, and particularly preferably acrylic acid.

  Moreover, the said polymerizable monomer may be carried by the inert gas at the time of plasmatization. Examples of the inert gas include nitrogen, argon, helium and the like. For example, most of the polymerizable monomers such as acrylic acid are in a liquid phase at normal temperature and pressure, and such polymerizable monomers are vaporized by heating and bubbling, etc., and are carrierized by the inert gas to be turned into plasma. Is preferred. In view of the burden on the heater when vaporizing by heating, the polymerizable monomer preferably has a boiling point of 300 ° C. or less. The polymerizable monomer is preferably one that does not decompose (chemically change) by heating.

The surface treatment of the cellulose film is performed by bringing the polymerizable monomer into plasma (including decomposition, excitation, activation, radicalization, and ionization) and bringing it into contact. The plasmification is preferably performed under a pressure near atmospheric pressure. Specifically, the range of 1.013 × 10 ^{4 to} 50.663 × 10 ⁴ Pa is preferable, and 1.333 × 10 ^{4 to} 10.664 is considered in consideration of easy adjustment of pressure and simplification of the apparatus configuration. × 10 ⁴ Pa is more preferable, and 9.331 × 10 ^{4 to} 10.9797 × 10 ⁴ Pa is more preferable. Plasmaization is not limited to the vicinity of atmospheric pressure, but can be performed under vacuum.

  Various apparatuses can be used for the surface treatment of the cellulose-based film by the above-described plasma treatment, and for example, an atmospheric pressure plasma processing apparatus can be used. The atmospheric pressure plasma processing apparatus is provided with a pair of electrodes facing each other, and performs a surface treatment by forming a plasma by passing a cellulosic film between the electrodes. The pair of electrodes can adopt various forms such as a flat plate shape, a roll shape, and an arc shape. A solid dielectric layer is formed on the opposing surface of at least one of the pair of electrodes. Moreover, by using at least one electrode of the pair of electrodes as a roll electrode, the cellulosic film can be conveyed so as to be wound around the roll electrode. In addition, the surface treatment by plasma-izing a cellulose film arrange | positions a transparent protective film in the exterior between a pair of said electrodes, and ejects the polymerizable monomer plasmatized between electrodes toward the external transparent protective film A remote atmospheric pressure plasma surface treatment apparatus can also be used.

  In the atmospheric pressure plasma processing apparatus, a power source is connected to one electrode, and the other electrode is electrically grounded. For example, a pulsed voltage is applied to one electrode by the power source, whereby a pulsed electric field is formed between the pair of electrodes, and atmospheric pressure plasma is generated. The rise time and / or fall time of the pulse is preferably 10 μs or less. The electric field strength is preferably 10 to 1000 kV / cm, and the frequency is preferably 0.5 to 100 kHz. The supply voltage is not particularly limited, and a continuous wave shape such as a sine wave can be adopted in addition to a pulse shape.

  Usually, at least one electrode of the pair of electrodes is provided with a polymerizable monomer jet nozzle and a suction nozzle, from which the polymerizable monomer is jetted, and the suction nozzle is formed of the treated polymerizable monomer. Exhaust is performed.

  Also, vaporizing means (eg, a heater) can be incorporated in the source of polymerizable monomer. When the polymerizable monomer is acrylic acid, the heating temperature is preferably room temperature (25 ° C.) to 80 ° C. A carrier supply source can be connected to the supply source of the polymerizable monomer. An inert gas is introduced from the carrier source to the source of polymerizable monomer where it is mixed with the vaporized polymerizable monomer. Mixing can also be performed by bubbling.

  The adhesive forming the adhesive layer of the present invention contains a modified polyvinyl alcohol resin containing a modified group containing at least one selected from a cationic group, an anionic group and a nonionic group. Compared with the unmodified polyvinyl alcohol-type resin conventionally used for the adhesive, the polyvinyl alcohol-type resin containing the various modified groups is more of the polymerizable monomer (especially polymerizable monomer containing a carboxyl group). Adhesive strength can be improved in relation to the surface of a cellulose film (polymerized film) that has been surface-treated by plasmatization.

  Examples of the modifying group in the modified polyvinyl alcohol resin include at least one selected from an anionic group and a nonionic group. Among these modified groups, a modified polyvinyl alcohol resin containing a cationic group is preferable.

  The predetermined modified polyvinyl alcohol-based resin can be obtained by copolymerization of a vinyl ester monomer and a copolymerizable monomer having the above-described modifying group and copolymerizable with the vinyl ester monomer, and then saponifying. . Moreover, it can obtain by copolymerizing a vinyl ester-type monomer and a copolymerization monomer, and guide | inducing that the said copolymerization monomer contains the said modification group. Saponification is performed before or after the induction. The copolymerization monomer has a carbon-carbon double bond such as a (meth) acryloyl group, a vinyl group, or a (meth) allyl group.

  In the predetermined modified polyvinyl alcohol-based resin, the ratio of the modifying group can be controlled by the ratio of the copolymerization monomer and the induction ratio of the modifying group. Usually, the ratio of the modifying group is preferably about 0.05 to 10 mol%, more preferably 0.1 to 5 mol%, based on 100 mol% of the total number of moles of the vinyl ester monomer and the copolymerization monomer, Furthermore, 0.2-3 mol% is preferable.

  Although the average degree of polymerization of the modified polyvinyl alcohol resin is not particularly limited, the average degree of polymerization is about 100 to 5000, preferably 1000 to 4000 from the viewpoint of adhesiveness. The average saponification degree of the modified polyvinyl alcohol-based resin is not particularly limited, but is about 85 to 100 mol%, preferably 90 to 100 mol%, on average.

  Examples of the vinyl ester monomers include vinyl formate, vinyl acetate, vinyl propionate, vinyl valerate, vinyl butyrate, vinyl isobutyrate, vinyl pivalate, vinyl caprate, vinyl laurate, vinyl stearate, vinyl benzoate, versatic. Although vinyl acid acid etc. are mention | raise | lifted, vinyl acetate is used preferably.

  The polyvinyl alcohol-based resin containing a cationic group can be obtained by using, for example, a copolymerizable monomer containing an amino group as the copolymerizable monomer. Examples of the copolymerizable monomer containing an amino group include N, N-dimethylaminoethyl (meth) acrylamide, N, N-dimethylaminopropyl (meth) acrylamide, N, N-diethylaminoethyl (meth) acrylamide, N N, N-dialkylaminoalkyl (meth) acrylamide such as N, N-diethylaminopropyl (meth) acrylamide; N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylaminopropyl (meth) acrylate, N, N -Tertiary amino group-containing monomers such as diethylaminoethyl (meth) acrylate, N, N-diethylaminopropyl (meth) acrylamide N, N-dialkylaminoalkyl (meth) acrylate; and (meth) acrylic acid t-butylaminoethyl Secondary amino group Monomer or the like having the like. As the copolymerizable monomer containing an amino group, allylamine, diallylamine and the like can be used. The tertiary amino group-containing monomer or diallylamine is used as a quaternary ammonium salt-containing monomer by quaternary ammonium salification of the tertiary amino group to trimethylammonium chloride or the like with various quaternizing agents such as methyl chloride. In addition, it can be quaternized with a quaternizing agent after copolymerization.

  Moreover, as a copolymerization monomer which can be used for introduction | transduction of a cationic group, (meth) acrylamide, N-methyl (meth) acrylamide, N-ethyl (meth) acrylamide, N-isopropyl (meth) acrylamide, N, N- Dimethyl (meth) acrylamide, diacetone (meth) acrylamide, N-methoxymethyl (meth) acrylamide, N-butoxymethyl (meth) acrylamide, N-methylol (meth) acrylamide, N-vinylacetamide, N, N′-methylenebis ( Amide monomers such as (meth) acrylamide; heterocyclic monomers containing N-acryloylmorpholine, N-acryloylpiperidine, N-methacryloylpiperidine and N-acryloylpyrrolidine.

  In addition, the polyvinyl alcohol-based resin containing a cationic group is a method in which N-vinyl succinimide or N-vinyl phthalimide is copolymerized as a copolymerization monomer, and then an amino group is introduced by decomposing the imide group with an alkali or hydrazine; It can be obtained by, for example, a method of Michael addition of acrylamide to an alcohol-based resin and then Hofmann decomposition of an acrylamide unit.

  Specific examples of the polyvinyl alcohol-based resin containing a cationic group include trade name CM-318 manufactured by Kuraray Co., Ltd. Specific examples of the polyvinyl alcohol-based resin containing a quaternary ammonium base as a cationic group include, for example, trade name K-210 manufactured by Nippon Synthetic Chemical Co., Ltd.

  Examples of the anionic group related to the modifying group include a carboxyl group and a sulfonic acid group. Among these, a sulfonic acid group is preferable.

  The polyvinyl alcohol-based resin containing a carboxyl group can be obtained by using, for example, a copolymerizable monomer containing a carboxyl group as the copolymerizable monomer. As the copolymerizable monomer containing a carboxyl group, those exemplified for the polymerizable monomer can be used. Specific examples of the polyvinyl alcohol-based resin containing a carboxyl group include, for example, trade name KL-118 manufactured by Kuraray Co., Ltd.

  The polyvinyl alcohol-based resin containing a sulfonic acid group can be obtained by using, for example, a copolymerizable monomer containing a sulfonic acid group as the copolymerizable monomer. Examples of the sulfonic acid group-containing monomer include olefin sulfonic acids such as ethylene sulfonic acid, allyl sulfonic acid, and methallyl sulfonic acid, or salts thereof; propyl 2-ethylhexyl malate, propyl tridecyl malate, propyl sulfonate Sulfonic acid (monoalkyl malate) such as eicosyl malate, alkyl sulfonate dimalate or salt thereof; alkyl (meth) acrylamide sulfonate such as sodium N-sulfoisobutylene acrylamide or salt thereof; 2-sulfonic acid ethyl acrylate or the like Examples thereof include alkyl (meth) acrylates of sulfonic acid or salts thereof. Examples of the salt include alkali metal salts such as sodium salt. Specific examples of the polyvinyl alcohol resin having a sulfonic acid include, for example, trade name L-3266 manufactured by Nippon Synthetic Chemical Co., Ltd.

  Examples of the nonionic group related to the modifying group include a modifying group based on alkylene oxide, an acetoacetyl group, a silanol group, a thiol group, an aldehyde group, an epoxy group, a urethane group, and a phosphate group. Among these, a modified group based on alkylene oxide, an acetoacetyl group, a silanol group, and a thiol group are preferable.

  A polyvinyl alcohol-based resin containing a modifying group based on alkylene oxide can be obtained by using, for example, a copolymerizable monomer having polyalkylene oxide as the copolymerizable monomer. The alkylene oxide is preferably an alkylene oxide having 2 to 4 carbon atoms, and is preferably an alkylene oxide ethylene oxide and / or propylene oxide. Examples of the copolymerizable monomer containing a modifying group based on polyalkylene oxide include polyoxyethylene (meth) acrylate, polyoxypropylene (meth) acrylate; polyoxyethylene (meth) acrylic acid amide, polyoxypropylene (meta ) Acrylic acid amide, polyoxyethylene (1- (meth) acrylamide-1,1-dimethylpropyl) ester; polyoxyethylene (meth) allyl ether, polyoxypropylene (meth) allyl ether; polyoxyethylene vinyl ether, polyoxy And propylene vinyl ether.

  Further, polyoxyalkylene allylamines such as polyoxyethylene allylamine and polyoxypropylene allylamine, polyoxyalkylene vinylamines such as polyoxyethylene vinylamine and polyoxypropylene vinylamine, and the like can also be used. In this case, a cationic group can be introduced simultaneously.

  Specific examples of the polyvinyl alcohol resin having polyalkylene oxide include, for example, trade name LW-320 manufactured by Nippon Synthetic Chemical Co., Ltd.

  A polyvinyl alcohol-based resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto, and a polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. And the like. Another example is a method in which diketene gas or liquid diketene is brought into direct contact with polyvinyl alcohol. Specific examples of the polyvinyl alcohol resin having an acetoacetyl group include trade name Z-200 manufactured by Nippon Synthetic Chemical Co., Ltd.

  A polyvinyl alcohol-based resin containing a silanol group can be obtained by hydrolyzing and condensing a hydroxyl group of a polyvinyl alcohol-based resin with a chlorosilane compound and / or an alkoxysilane compound. In addition, a polyvinyl alcohol-based resin containing a silanol group is obtained by addition-reacting a vinyl acetate copolymer having a carbon-carbon double bond and a hydrosilane compound containing a SiH group, and then acid or sodium hydroxide, sodium It can be obtained by saponification using an alkali such as methylate. Examples of the hydrosilane compound include halogenated silanes such as methyldichlorosilane, trichlorosilane, and phenyldichlorosilane; alkoxysilanes such as methyldiethoxysilane, methyldimethoxysilane, phenyldimethoxysilane, trimethoxysilane, and triethoxysilane. Acyloxysilanes such as methyldiacetoxysilane, phenyldiacetoxysilane, and triacetoxysilane; and aminosilanes such as methyldiaminoxysilane, triaminoxysilane, dimethylaminoxysilane, and triaminosilane. Specific examples of the polyvinyl alcohol-based resin containing a silanol group include, for example, trade names R-1130, R-2105, R-2130 manufactured by Kuraray Co., Ltd.

  A polyvinyl alcohol-based resin containing a thiol group can be obtained, for example, by modifying a terminal of polyvinyl alcohol-based resin or partially saponified polyvinyl acetate with a thiol group. Examples of the modification method include terminals obtained by polymerizing vinyl acetate in the presence of thiolic acid such as mercaptoacetic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid and 2-mercaptostearic acid as a chain transfer agent. The thiol group-containing polyvinyl acetate can be produced by saponification by a conventional method. Specific examples of the polyvinyl alcohol resin containing a thiol group include M-115 manufactured by Kuraray Co., Ltd.

  The polyvinyl alcohol resin containing an aldehyde group can be obtained by using, for example, a copolymerizable monomer containing an aldehyde group as the copolymerizable monomer. Examples of the aldehyde group-containing monomer include acrolein.

  The adhesive may contain a cross-linking agent in addition to the modified polyvinyl alcohol resin. As a crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. A compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene diamine and hexamethylene diamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (Isocyanates such as 4-phenylmethane triisocyanate, isophorone diisocyanate and ketoxime block product or phenol block product thereof; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexane Diol diglycidyl ether, trimethylolpropane triglycidyl ether, jig Epoxys such as sidylaniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; Aldehydes: amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; further sodium, potassium, magnesium, calcium, aluminum, iron And salts of divalent metals such as nickel or trivalent metals and oxides thereof, among which amino-formaldehyde resins and dia Dehydrates are preferred, amino-formaldehyde resins are preferably compounds containing methylol groups, and dialdehydes are preferably glyoxal, particularly methylol melamine, which is a compound containing methylol groups. Moreover, as a crosslinking agent, coupling agents, such as a silane coupling agent and a titanium coupling agent, can be used.

  The amount of the crosslinking agent can be appropriately designed according to the type of polyvinyl alcohol resin, etc., but is usually 60 parts by weight or less, preferably about 1 to 60 parts by weight, preferably 100 parts by weight of the modified polyvinyl alcohol resin. Is about 10 to 55 parts by weight, more preferably 20 to 50 parts by weight. In such a range, good pot life and durability can be obtained.

  When the amount of the crosslinking agent is too large, the reaction of the crosslinking agent proceeds in a short time and the adhesive tends to gel. As a result, the pot life as an adhesive is extremely shortened, making industrial use difficult.

  The adhesive is a resin solution containing the modified polyvinyl alcohol resin and is usually used as an aqueous solution. The method for preparing the resin solution that is an adhesive is not particularly limited. Usually, a crosslinking agent is appropriately mixed with the modified polyvinyl alcohol resin, and the concentration is adjusted appropriately. The resin solution concentration is not particularly limited, but is usually adjusted to about 0.1 to 5% by weight.

  The adhesive may contain various leveling agents, tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and other stabilizers. The adhesive of the present application can contain a metal compound filler.

  The polarizing plate of the present invention is produced by bonding a surface-treated transparent protective film and a polarizer on at least one surface using the adhesive. In the obtained polarizing plate, a transparent protective film is provided on one or both sides of the polarizer via an adhesive layer formed of the polarizing plate adhesive.

  Application | coating of the said adhesive agent may be performed to any of a transparent protective film and a polarizer, and may be performed to both. The application of the adhesive is preferably performed so that the thickness of the adhesive layer after drying is about 10 to 300 nm. The thickness of the adhesive layer is more preferably 10 to 250 nm, and still more preferably 20 to 200 nm, from the viewpoint of obtaining a uniform in-plane thickness and obtaining a sufficient adhesive force.

  The method of adjusting the thickness of the adhesive layer is not particularly limited, and examples thereof include a method of adjusting the solid content concentration of the adhesive solution and an adhesive application device. The method for measuring the thickness of the adhesive layer is not particularly limited, but cross-sectional observation measurement using SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) is preferably used. The application operation of the adhesive is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed.

  The production of the polarizing plate of the present invention is, for example, a method in which an adhesive is applied on a transparent protective film, a drying step is performed, and a dried adhesive layer is formed, and then the pressure-sensitive adhesive layer is bonded to a polarizer. Can be used. Moreover, after apply | coating the said adhesive agent to a polarizer and / or a transparent protective film in the state of the said adhesive agent, and bonding a polarizer and a transparent protective film after that, a drying process is given, A polarizing plate can be obtained by forming an adhesive layer. The lamination of the transparent protective film can be performed by a roll laminator or the like. The drying temperature of a drying process is about 5-150 degreeC, Preferably it is 30-120 degreeC, 120 seconds or more, Furthermore, it is 300 seconds or more.

  The polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. Can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance, heat resistance and the like can be preferably used.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 1 to 200 μm, and particularly preferably 1 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  The polarizing plate or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply conventionally. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Examples and the like specifically showing the configuration and effects of the present invention will be described below. In each example, parts and% are based on weight unless otherwise specified.

Example 1
(Polarizer)
A polyvinyl alcohol film having an average polymerization degree of 2400 and a saponification degree of 99.9 mol% and a thickness of 75 μm was immersed in warm water at 30 ° C. for 60 seconds to swell. Next, the film was dyed while being immersed in an aqueous solution of 0.3% concentration of iodine / potassium iodide (weight ratio = 0.5 / 8) and stretched to 3.5 times. Then, it extended | stretched so that the total draw ratio might be 6 times in 65 degreeC borate ester aqueous solution. After extending | stretching, it dried for 3 minutes in 40 degreeC oven, and obtained the polarizer.

(Surface treatment of transparent protective film)
As the transparent protective film, a triacetyl cellulose film having a thickness of 80 μm was used. The triacetyl cellulose film was subjected to a surface treatment in which acrylic acid was converted into plasma and contacted using an atmospheric pressure plasma polymerization processing apparatus (plasma polymerization apparatus manufactured by Sekisui Chemical Co., Ltd.). The processing conditions are as follows. Acrylic acid was applied as a processing gas using nitrogen, which is an inert gas, as a carrier.
Output pulse frequency from power supply: 5 to 30 kHz
Pulse voltage between electrodes: 13-18kV
Flow rate of processing gas (acrylic acid + nitrogen): 10 L / min
Acrylic acid concentration in the processing gas: 0.1 to 10% by volume
Transport speed of transparent protective film: 10m / min

(Preparation of adhesive)
Polyvinyl alcohol resin containing a cationic group (trade name CM-318, manufactured by Kuraray Co., Ltd., degree of saponification: 86.0 to 91.0 mol%, viscosity (concentration 4%, 20 ° C.) 17.0 to 27 0.03 mPa · s) was dissolved in 100 parts of pure water under a temperature condition of 30 ° C. to prepare an aqueous solution adjusted to a solid content concentration of 3%. This aqueous solution was used as an adhesive.

(Preparation of polarizing plate)
The adhesive was applied to the surface-treated surface of the transparent protective film so that the thickness of the adhesive layer after drying was 100 nm. Next, the transparent protective film coated with the adhesive was dried at 70 ° C. for 5 minutes to obtain two transparent protective films with an adhesive layer. These two transparent protective films with an adhesive layer were bonded to both sides of the polarizer with a roll machine to produce a polarizing plate.

Examples 2-8, Comparative Examples 1-9
A polarizing plate was produced in the same manner as in Example 1 except that the surface treatment of the transparent protective film and the type of polyvinyl alcohol resin used for the adhesive were changed as shown in Table 1.

  The following evaluation was performed about the polarizing plate obtained by the Example and the comparative example. The results are shown in Table 1.

(Adhesive strength)
The obtained polarizing plate was cut into a size of 15 mm × 150 mm to obtain a sample. The sample was affixed on the glass plate with a double-sided adhesive tape (Nitto Denko Corporation, NO.500). The sample (polarizing plate) was previously provided with a peeling peel between the transparent protective film and the polarizer, and the peel was chucked on a variable angle peel tester (Asahi Seiko Co., Ltd.) to peel strength (N / 15 mm). The measurement conditions were normal temperature (23 ° C.), peel angle: 90 degrees, and peel speed: 3000 mm / min. Table 1 shows values obtained by averaging data between 50 mm and 100 mm of the obtained measurement data.

(Heating dimensional stability)
A sample obtained by cutting a polarizing plate into a square (10 cm × 10 cm) so that one side is parallel to the absorption axis direction was used as a sample. When you draw a line connecting the marks, mark them with a cutter (2 places) in the center of the two opposite edges of the sample so that the lines are parallel to the absorption axis direction of the sample (polarizing plate) And the distance (A) between the marks (two places) was measured using a caliper. Thereafter, the sample was put into a drier (temperature: 80 ° C.) for 24 hours, and then the incision interval (B) was measured again using a caliper.
From the values of (A) and (B), the dimensional change rate (%) was determined by the following formula.
Dimensional change rate (%) = [− {(A) − (B)} / (A)}] × 100

(Film appearance)
The appearance of the obtained polarizing plate was evaluated according to the following criteria.
○: Nothing is confirmed on the polarizing plate surface.
(Triangle | delta): A micro white spot-like or stripe-like fault is confirmed on the polarizing plate surface.

In addition, about the surface treatment in Table 1, Examples 2-8 and the comparative example 1 are the same as Example 1. FIG. The saponification of Comparative Examples 2 and 3 was performed by immersing the triacetyl cellulose film in a 10 wt% sodium hydroxide aqueous solution at 65 ° C for 23 seconds. The corona treatment of Comparative Examples 6 and 7 was performed in the air with a corona irradiator (Kasuga Denki Co., Ltd., CT-0212) under a discharge amount of 40 W / m ² / min. In Comparative Examples 8 and 9, plasma discharge was performed by applying an AC pulse voltage with a pulse width of 100 μs, a frequency of 30 kHz, and a voltage of ± 5 kV using a plasma processing machine (Sekisui Chemical Co., Ltd., AT series), 5 m / min. The plasma treatment was performed under normal pressure using nitrogen as the treatment gas at the treatment speed.

Moreover, each polyvinyl alcohol-type resin * 1 thru | or 9 used as an adhesive agent shows the following.
* 1: Product name CM-318 manufactured by Kuraray Co., Ltd., which is a polyvinyl alcohol resin containing a cationic group.
* 2: Product name K-210 manufactured by Nippon Synthetic Chemical Co., Ltd., which is a polyvinyl alcohol resin containing a quaternary ammonium base.
* 3: Product name L-3266 manufactured by Nippon Synthetic Chemical Co., Ltd., which is a polyvinyl alcohol resin having a sulfonic acid group.
* 4: Product name KL-118 manufactured by Kuraray Co., Ltd., which is a polyvinyl alcohol-based resin containing a carboxyl group.
* 5: Product name LW-320 manufactured by Nippon Synthetic Chemical Co., Ltd., which is a polyvinyl alcohol-based resin having polyethylene oxide.
* 6: Product name Z-200 manufactured by Nippon Synthetic Chemical Co., Ltd., which is a polyvinyl alcohol resin having an acetoacetyl group.
* 7: Product name R-1130 manufactured by Kuraray Co., Ltd., which is a polyvinyl alcohol-based resin containing a silanol group.
* 8: M-115 manufactured by Kuraray Co., Ltd., which is a polyvinyl alcohol resin containing a thiol group.
* 9: Product name NH-18 manufactured by Nippon Synthetic Chemical Co., Ltd., which is a polyvinyl alcohol resin not containing a modifying group.

  As shown in Table 1, the polarizing plate of the present invention has high adhesive strength, a small dimensional change rate, and good heating dimensional stability. On the other hand, in Comparative Example 1, the same surface treatment as that of the present invention was applied to the transparent protective film, but sufficient adhesive strength was not obtained because the polyvinyl alcohol resin did not have a modifying group. In Comparative Examples 2 and 3, the triacetyl cellulose film is subjected to surface treatment by saponification, and the dimensional change rate is large and the heat dimensional stability cannot be satisfied. In Comparative Examples 4 and 5, since the surface treatment is not performed on the transparent protective film, the adhesive containing the modified polyvinyl alcohol similar to the present invention is used, but the adhesive strength is insufficient. In Comparative Examples 6-9, since the transparent protective film has been subjected to a surface treatment different from that of the present invention, an adhesive containing a modified polyvinyl alcohol similar to the present invention is used, but the adhesive strength is insufficient. Yes. In Comparative Examples 4 to 9, the heating dimensional stability was not evaluated due to insufficient adhesive strength.

Claims (2)

On at least one surface of a polarizer, a method of manufacturing a polarizing plate transparent protective film that are bonded together with an adhesive layer,
The transparent protective film is a cellulose film,
The surface of the transparent protective film to be bonded to the polarizer is subjected to surface treatment by bringing acrylic acid into plasma and contacting it, and
Polarized light characterized by having a step of forming an adhesive layer by bonding a surface-treated surface of the transparent protective film and a polarizer with an adhesive containing a modified polyvinyl alcohol resin containing a cationic group A manufacturing method of a board. The method for producing a polarizing plate according to claim 1, wherein the cationic group is a quaternary ammonium base.