JP2009042384A - Polarizing plate and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate for improving adhesion and warm water resistance between a polarizing film and a protection film by improving an adhesive layer in the polarizing plate formed by laminating the protection film via the adhesive layer on at least one face of a polyvinylalcohol based polarization film. <P>SOLUTION: The polarizing plate is formed by laminating the protection film via the adhesive layer on at least one face of the polyvinylalcohol based polarization film. The adhesive layer is formed by using an adhesive composition consisting of water solution of oxyzirconium salt. The polarizing plate and its manufacturing method are provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polarizing plate in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive layer, and a method for producing the same.

  The polarizing plate usually has a configuration in which a protective film is laminated on one side or both sides of a polarizing film formed of a polyvinyl alcohol-based resin having a dichroic dye adsorbed and oriented, with an adhesive layer interposed therebetween. The polarizing plate is bonded to the liquid crystal cell with an adhesive as necessary as a component of the liquid crystal display device via another optical system film.

  Liquid crystal display devices are being used in various environments as their applications expand. Therefore, high environmental resistance is required for the components constituting the liquid crystal display device. For example, liquid crystal display devices for mobile use typified by mobile phones are required to be able to be used under wet heat, and polarizing plates used therein are also required to have high wet heat resistance. . However, the polarizing plate having a conventional configuration has a problem that the polarizing performance is likely to be deteriorated and the interface between the polarizing film and the protective film is liable to be peeled, particularly when exposed to a wet and heat environment for a long time.

  For such problems, it has been proposed to use a thermoplastic cycloolefin-based resin as a protective film for a polarizing plate. For example, in Japanese Patent Laid-Open No. 5-212828 (Patent Document 1), a thermoplastic saturated norbornene resin sheet is laminated on at least one surface of a polyvinyl alcohol sheet via an acrylic pressure-sensitive adhesive layer, and is heated and pressure-bonded for polarization. A technique for forming a plate (composite sheet) is disclosed. However, an acrylic pressure-sensitive adhesive (also referred to as a pressure-sensitive adhesive) itself has a thickness of about 10 to 50 μm, and thus the liquid crystal display device has to be thick. In addition, dry laminate adhesives, styrene butadiene rubber adhesives, epoxy two-component curable adhesives, and the like contain organic solvents, which have environmental and health problems for workers. Furthermore, when an adhesive containing such an organic solvent is to be applied to a conventional polarizing plate manufacturing facility that does not use an organic solvent, it is complicated to modify the facility, such as newly installing an explosion-proof facility.

  It is also known that a cycloolefin-based resin film is bonded to a polarizing film made of a polyvinyl alcohol-based resin via an adhesive layer, for example, Japanese Patent Laid-Open No. 2005-70140 (Patent Document 2) and Japanese Patent Application Laid-Open No. 2005-2005. JP-A-1818117 (Patent Document 3) and JP-A-2005-208456 (Patent Document 4) disclose a water-based adhesive containing a urethane resin, particularly a polyester ionomer-type urethane resin, on a polarizing film made of a polyvinyl alcohol resin. It describes that a cycloolefin resin film is laminated through an agent. Accordingly, the cycloolefin-based protective film can be directly laminated on the polarizing film formed of the polyvinyl alcohol-based resin by the roll-to-roll method.

  On the other hand, in JP-A-9-318814 (Patent Document 5), JP-A-2005-173440 (Patent Document 6) and JP-A-2005-10760 (Patent Document 7), as a protective film for a polarizing plate, Various adhesives have been proposed for bonding a protective film to a polarizing film made of a polyvinyl alcohol resin using a transparent resin film formed of a cellulose resin typified by triacetyl cellulose. Here, the adhesive applied between the films is a mixture of a polyvinyl alcohol-based resin containing an acetoacetyl group and a compound having a methylol group in a specific blending ratio, and a pH after adjusting the methylol group-containing compound. An adhesive prepared by adjusting or mixing a glyoxal resin or a metal alkoxide compound is described, whereby a highly water-resistant polarizing plate can be obtained.

  Among these, Patent Document 4 discloses a water-based first adhesive containing a polyester ionomer-type urethane resin and a compound having a glycidyloxy group on one surface of a polarizing film formed of a polyvinyl alcohol resin. A cycloolefin-based resin film is laminated on the other surface, and the other surface has an acetic acid via an aqueous second adhesive having a composition different from that of the first adhesive, for example, an aqueous solution of a polyvinyl alcohol-based resin. It is disclosed that a cellulose film is laminated to form a polarizing plate. Moreover, in each Example 2 of patent documents 2 and 3, a film of a norbornene resin which is a kind of cycloolefin resin is provided on one surface of a polarizing film formed of a polyvinyl alcohol resin on the other surface. Describes that a triacetyl cellulose film was bonded to each other via a urethane adhesive to form a polarizing plate.

Japanese Patent Laying-Open No. 2005-352011 (Patent Document 8) also discloses a polarizing plate in which a cycloolefin resin film is laminated on one side of a polarizing film and a cellulose acetate film is laminated on the opposite side.
Japanese Patent Laid-Open No. 5-212828 JP-A-2005-70140 JP 2005-181817 A JP-A-2005-208456 JP 9-318814 A JP-A-2005-173440 Japanese Patent Laying-Open No. 2005-10760 JP 2005-352011 A

  An object of the present invention is to provide a polarizing film and a protective film by improving the adhesive layer in a polarizing plate in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive layer. It is to provide a polarizing plate having improved adhesion and hot water resistance.

  The present invention also provides a method for producing a polarizing plate capable of firmly bonding a polarizing film formed of a polyvinyl alcohol resin and a protective film using a water-based adhesive that does not substantially contain an organic solvent. For that purpose.

  As a result of diligent research under such a purpose, the present inventors have obtained polarization by using a water-based adhesive composition containing a specific component as an adhesive for bonding a polarizing film and a protective film. It has been found that a polarizing plate excellent in adhesiveness and water resistance after bonding can be obtained by increasing the bonding speed between the film and the protective film, and has reached the present invention. That is, the present invention is as follows.

  The polarizing plate of the present invention is an adhesive composition in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive layer, and the adhesive layer is composed of an aqueous solution of an oxyzirconium salt. It is formed using.

  In the polarizing plate of the present invention, the weight ratio of the oxyzirconium salt and water in the adhesive composition is preferably 0.1 to 10: 100.

  In the polarizing plate of the present invention, the protective film is preferably composed of a cellulose acetate-based resin or a cycloolefin-based resin, and the protective film is composed of a cellulose acetate-based resin on one side of the polarizing film. More preferably, a film is laminated, and a protective film made of a cycloolefin-based resin is laminated on one side of the polarizing film.

  The present invention also provides a method for producing a polarizing plate in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive composition comprising an aqueous solution of an oxyzirconium salt.

  According to the present invention, it is possible to produce a polarizing plate which is excellent in adhesiveness between the polarizing film and the protective film and has far superior warm water resistance compared to conventional products. In addition, according to the present invention, since it is not necessary to use an organic solvent in the production of the polarizing plate, it is excellent in terms of environment and safety and hygiene, and is produced with the same equipment as a polarizing plate made of a conventional protective film / polarizing film. And there is no need to make a large capital investment.

  The polarizing plate of the present invention basically has a configuration in which a protective film is laminated on at least one surface of a polarizing film made of a polyvinyl alcohol resin via an adhesive layer. Hereinafter, each structure of the polarizing plate of this invention is demonstrated in detail.

<Polarizing film>
The polyvinyl alcohol resin constituting the polarizing film can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate, copolymers of vinyl acetate and other monomers copolymerizable therewith. Examples of other monomers copolymerized with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, and acrylamides having an ammonium group. The saponification degree of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. This polyvinyl alcohol-based resin may be further modified, and for example, polyvinyl polymers modified with aldehydes, polyvinyl acetal, and the like may be used. Moreover, the average polymerization degree of the polyvinyl alcohol-type resin which comprises a polarizing film is 1000-10000 normally, Preferably it is 1500-5000.

  A film obtained by forming such a polyvinyl alcohol-based resin into a film (polyvinyl alcohol-based resin film) is used as an original film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. Although the film thickness of a polyvinyl alcohol-type resin film is not specifically limited, For example, it is 10-150 micrometers.

  A polarizing film usually has a step of uniaxially stretching such a polyvinyl alcohol resin film, a step of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye, and a dichroic dye adsorbed. It is manufactured through a step of treating the polyvinyl alcohol-based resin film with a boric acid aqueous solution and a step of washing with water after the treatment with the boric acid aqueous solution.

  Uniaxial stretching may be performed before dyeing, simultaneously with dyeing, or after dyeing. When uniaxial stretching is performed after dyeing, this uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, uniaxial stretching can be performed in these plural stages. In uniaxial stretching, it may be uniaxially stretched between rolls having different peripheral speeds, or may be uniaxially stretched using a hot roll. Further, it may be dry stretching such as stretching in the air, or may be wet stretching in which stretching is performed in a state swollen with a solvent. The draw ratio is usually 3 to 8 times.

  In order to dye a polyvinyl alcohol resin film with a dichroic dye, for example, the polyvinyl alcohol resin film may be immersed in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic dye is used as the dichroic dye. In addition, it is preferable that the polyvinyl alcohol-type resin film performs the immersion process to water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol resin film by dipping it in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually 20 to 40 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 20 to 1800 seconds.

On the other hand, when a dichroic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic dye is usually employed. The content of the dichroic dye in this aqueous solution is usually 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dye solution used for dyeing is usually 20 to 80 ° C., and the immersion time (dyeing time) in this aqueous solution is usually 10 to 1800 seconds.

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

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment is performed, for example, by immersing a boric acid-treated polyvinyl alcohol resin film in water. The water temperature in the water washing treatment is usually 5 to 40 ° C., and the immersion time is usually 1 to 120 seconds. After washing with water, a drying process is performed to obtain a polarizing film. A drying process is normally performed using a hot air dryer and a far-infrared heater. The temperature of a drying process is 30-100 degreeC normally, Preferably it is 50-80 degreeC. The time for the drying treatment is usually 60 to 600 seconds, preferably 120 to 600 seconds.

  In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizing film. The thickness of this polarizing film is usually in the range of 5 to 40 μm, preferably in the range of 10 to 35 μm.

<Adhesive layer>
The polarizing plate of the present invention uses an adhesive composition in which an adhesive layer interposed between the polarizing film described above and a protective film laminated on at least one surface of the polarizing film is an aqueous solution of an oxyzirconium salt. It is characterized by being formed. Such an adhesive layer in the present invention is an adhesive layer formed of a water-based adhesive composition that does not substantially cause organic health problems and does not cause a health hazard for workers. However, the polarizing film formed of polyvinyl alcohol and the protective film can be firmly bonded.

The adhesive composition used in the present invention comprises an aqueous solution of an oxyzirconium salt. Here, the “oxyzirconium salt” refers to a salt containing a positive divalent group represented by ZrO (called zirconyl), such as zirconium oxynitrate (ZrO (NO ₃ ) ₂ ), zirconium oxyacetate ( ZrO (C ₂ H ₃ O ₂ ) ₂ ), zirconium oxychloride (ZrOCl ₂ ), zirconium oxysulfate (ZrOSO ₄ ), zirconium oxycarbonate (ZrOCO ₃ ), zirconium ammonium oxycarbonate ((NH ₄ ) ₂ ZrO (CO ₃ ) ) _2), oxy zirconium octylate _{(ZrO (C 8 H 15 O} 2) 2), hydroxide oxyzirconium (ZrO (OH) _2), hydroxide zirconium oxychloride (ZrO (OH) Cl), potassium zirconium oxycarbonate (K ₂ [ZrO (CO ₃ ) ₂ ]) and the like. Among the above, zirconium oxynitrate or zirconium oxyacetate is preferable from the viewpoint of adhesion, adhesion speed, and water resistance.

  The above-mentioned oxyzirconium salts are commercially available as appropriate, for example, zircozole ZN, zircozol AC-7, zirconium oxychloride, zircozole ZC, zircozol ZC-2, zirconyl sulfate, zircozol ZA, zircozol ZA-30, zircozol ZA-20, Zircozole ZK-10, zirconyl octylate, zirconyl carbonate, zirconium hydroxide, R zirconium hydroxide, NN zirconium hydroxide (all of which are manufactured by Daiichi Rare Element Chemical Co., Ltd.) and the like can be preferably used.

  The adhesive composition used in the present invention has a weight ratio of oxyzirconium salt to water of 0.1 to 10: 100. When the oxyzirconium salt is less than 0.1 by weight with respect to the water 100, the water resistance tends to be insufficient, and when the oxyzirconium salt exceeds 10 by weight with respect to the water 100 Tends to deteriorate the optical properties of the obtained polarizing plate. The weight ratio of oxyzirconium salt to water in the adhesive composition is preferably 0.2 to 5: 100. The water used in the adhesive composition in the present invention is not particularly limited, such as pure water, ultrapure water, and tap water. However, from the viewpoint of maintaining the uniformity and transparency of the formed adhesive layer, pure water is used. Or ultrapure water is preferable.

  The adhesive composition used in the present invention can exhibit strong adhesiveness regardless of pH, and the pH is not particularly limited. The pH of the adhesive composition is, for example, a pH meter (D-51 type, manufactured by HORIBA) and a pH electrode (9621-10D type, manufactured by HORIBA). ) Can be measured by soaking.

  Although the thickness in particular of the adhesive bond layer in this invention is not restrict | limited, It is preferable that it is 0.01-5 micrometers, and it is more preferable that it is 0.01-2 micrometers. When the thickness of the adhesive layer is less than 0.01 μm, sufficient adhesion tends to be difficult to obtain, and when the thickness of the adhesive layer exceeds 5 μm, the appearance of the polarizing plate tends to be poor. It is because it is in a tendency.

  The adhesive layer in the present invention is not limited to the above-mentioned adhesive composition as long as it does not impair the effects of the present invention. For example, a crosslinking agent, a plasticizer, a silane coupling agent, an antistatic agent, fine particles, etc. It may be formed using a material to which the additive is added.

<Protective film>
The polarizing plate of the present invention is formed by laminating a protective film on at least one surface of the polarizing film described above via the adhesive layer described above. As a protective film in the polarizing plate of the present invention, for example, cellulose acetate resin, cycloolefin resin, polyolefin resin, acrylic resin, polyimide resin, polycarbonate resin, polyester resin, etc. A protective film composed of an appropriate material widely used as a forming material can be used without particular limitation. Among these, from the viewpoint of mass productivity and adhesiveness, it is preferable to include a protective film composed of a cellulose acetate-based resin or a cycloolefin-based resin. In addition, from the viewpoint of ease of providing a surface treatment layer and optical properties, the polarizing plate of the present invention has a protective film composed of a cellulose acetate-based resin laminated on one side of the polarizing film, It can also be set as the structure where the protective film comprised from the cycloolefin type resin was laminated | stacked on the one side of the other side.

  The cycloolefin resin that can be suitably used for the protective film in the present invention is a thermoplastic resin having a unit of a monomer composed of a cyclic olefin (cycloolefin) such as norbornene and a polycyclic norbornene monomer. Also called thermoplastic cycloolefin resin). This cycloolefin-based resin may be a hydrogenated product of a ring-opening polymer of the above-mentioned cycloolefin, a ring-opening copolymer using two or more kinds of cycloolefin, cycloolefin and chain olefin, vinyl group, etc. It may be an addition polymer with an aromatic compound having Those having a polar group introduced are also effective.

  When a protective film is formed using a copolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group, examples of the chain olefin include ethylene and propylene, and an aromatic group having a vinyl group. Examples of the compound include styrene, α-methylstyrene, and nuclear alkyl-substituted styrene. In such a copolymer, the monomer unit composed of cycloolefin may be 50 mol% or less (preferably 15 to 50 mol%). In particular, when a protective film is formed using a terpolymer of a cycloolefin, a chain olefin, and an aromatic compound having a vinyl group, the monomer unit composed of cycloolefin has a relatively small amount as described above. It can be. In such a terpolymer, the monomer unit composed of a chain olefin is usually 5 to 80 mol%, and the monomer unit composed of an aromatic compound having a vinyl group is usually 5 to 80 mol%.

  Cycloolefin-based resins may be commercial products such as Topas (manufactured by Ticona), Arton (manufactured by JSR Corporation), ZEONOR (manufactured by Nippon Zeon Co., Ltd.), ZEONEX (manufactured by Nippon Zeon Corporation). ) And Apel (Mitsui Chemicals) can be preferably used. When such a cycloolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, for example, commercially available cycloolefin resin films such as Essina (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa Film (manufactured by Optes Co., Ltd.), etc. The product may be used as a protective film.

  The protective film composed of the cycloolefin resin may be uniaxially stretched or biaxially stretched. In this case, the draw ratio is usually 1.1 to 5 times, preferably 1.1 to 3 times.

  Moreover, the cellulose acetate type resin which can be used suitably for the protective film in this invention is a cellulose part or a complete acetate ester, for example, a triacetyl cellulose film, a diacetyl cellulose film, etc. are mentioned.

  Examples of such cellulose acetate-based resins include commercially available products such as Fujitac TD80 (manufactured by Fuji Photo Film Co., Ltd.), Fujitac TD80UF (manufactured by Fuji Photo Film Co., Ltd.), and Fujitac TD80UZ (manufactured by Fuji Photo Film Co., Ltd.). ), KC8UX2M (manufactured by Konica Minolta Opto), and KC8UY (manufactured by Konica Minolta Opto) can be suitably used.

  The protective film used in the polarizing plate of the present invention preferably has a small thickness, but if it is too thin, the strength tends to be low, and the processability tends to be poor. There exists a tendency for the weight of a polarizing plate to become large. From such a viewpoint, the thickness of the protective film in the polarizing plate of the present invention is usually 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm in the case of a protective film composed of a cycloolefin resin. In the case of a protective film composed of a cellulose acetate resin, it is usually 20 to 200 μm, preferably 30 to 150 μm, more preferably 40 to 100 μm.

  The protective film in the polarizing plate of the present invention is one in which the surface opposite to the surface to be attached to the polarizing film is subjected to surface treatment such as antiglare treatment, hard coat treatment, antistatic treatment, antireflection treatment and the like. May be. Moreover, the coating layer which consists of a liquid crystalline compound, its high molecular weight compound, etc. may be formed in the surface on the opposite side to the surface stuck to the polarizing film of a protective film.

  Moreover, the protective film in the polarizing plate of this invention may have the optical functional film stuck on the surface on the opposite side to the surface stuck on a polarizing film through the adhesive layer. An adhesive is a viscoelastic material that can be removed with almost no trace if it adheres to the surface of another substance simply by pressing it, and if it is peeled off from the surface of the adherence, it only has strength. Also called pressure sensitive adhesive. As an optical functional film, for example, a liquid crystal compound is applied to the surface of a base material, an oriented optical compensation film, a reflection type polarization separation that transmits a certain kind of polarized light and reflects a polarized light having the opposite property. Film, retardation film made of polycarbonate resin, retardation film made of cyclic polyolefin resin, film with anti-glare function having a concavo-convex shape on the surface, film with anti-reflection treatment on the surface, reflection film having a reflection function on the surface, reflection Examples thereof include a transflective film having both a function and a transmission function.

  Examples of commercially available products corresponding to an optical compensation film in which a liquid crystal compound is applied to the substrate surface and oriented include, for example, WV film (manufactured by Fuji Photo Film Co., Ltd.), NH film (manufactured by Nippon Oil Corporation). NR film (manufactured by Nippon Oil Corporation). Moreover, DBEF (made by Sumitomo 3M Co., Ltd.) etc. are mentioned as a commercial item corresponding to the reflective polarization separation film which permeate | transmits a certain kind of polarized light and reflects the polarized light which shows the reverse property. Moreover, Arton (manufactured by JSR Co., Ltd.), Essina (manufactured by Sekisui Chemical Co., Ltd.), Zeonore film (manufactured by Optes Co., Ltd.) and the like are listed as commercial products corresponding to retardation films made of cyclic polyolefin resin. .

<Production method of polarizing plate>
The present invention also provides a method for producing a polarizing plate in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive composition comprising an aqueous solution of an oxyzirconium salt. The manufacturing method of the polarizing plate of the present invention described above is not particularly limited, and the polarizing plate of the present invention is not limited to that manufactured by such a manufacturing method of the polarizing plate of the present invention. It can manufacture suitably with the manufacturing method of a board.

  In the method for producing a polarizing plate of the present invention, first, an adhesive composition is prepared by blending the above-described oxyzirconium salt into water. Also in the method for producing a polarizing plate of the present invention, as described above, the oxyzirconium salt contained in the adhesive composition is preferably zirconium oxynitrate or zirconium oxyacetate.

  Bonding of the polarizing film and the protective film using such an adhesive composition can be performed by a conventionally known appropriate method, for example, casting method, Mayer bar coating method, gravure coating method, die coating method, dip coating. Examples include a method in which an adhesive composition is applied to an adhesive surface of a polarizing film and / or a protective film by a coating method, a spraying method, and the like, and the both are overlapped. The casting method is a method in which a polarizing film or a protective film, which is an object to be coated, is moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two, and the adhesive composition is allowed to flow down and spread on the surface. It is a method to make it. After apply | coating an adhesive composition, a polarizing film and a protective film are pinched | interposed and bonded together by a nip roll.

  In order to improve the adhesion, the surface of the polarizing film and / or the protective film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, and saponification treatment. Examples of the saponification treatment include a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

  After laminating the polarizing film and the protective film, a drying process is performed. The drying process is performed, for example, by blowing hot air, and the temperature at that time is appropriately selected from the range of 40 to 100 ° C., preferably 60 to 100 ° C. The drying time is usually 20 to 1200 seconds.

  Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited to these Examples.

<Example 1>
A 75 μm-thick polyvinyl alcohol-based resin film (average polymerization degree: 1700, saponification degree: 99.9 mol% or more) was subjected to uniaxial stretching (stretching ratio: 5 times), and while being kept in tension, iodine and iodine It was immersed in an aqueous solution containing potassium iodide (iodine: potassium iodide: water = 0.05: 5: 100 (weight ratio)) for 60 seconds. Next, it was immersed in a 65 ° C. aqueous solution containing potassium iodide and boric acid (potassium iodide: boric acid: water = 2.5: 7.5: 100 (weight ratio)) for 300 seconds. After washing with pure water at 25 ° C. for 20 seconds, the film was dried at 50 ° C. to obtain a polarizing film formed of a polyvinyl alcohol resin.

  1 part by weight of zirconium oxynitrate (Zircosol ZN, manufactured by Daiichi Rare Element Chemical Co., Ltd.) was dissolved in 100 parts by weight of water in a dissolution tank to prepare an adhesive composition. About the prepared adhesive composition, use a pH meter (D-51 type, manufactured by HORIBA) and a pH electrode (9621-10D type, manufactured by HORIBA) and immerse the pH electrode in the liquid (23 ° C.) of the adhesive composition. When pH was measured, it was 1.6. In a room temperature (23 ° C.) atmosphere, an adhesive composition is applied to both sides of the polarizing film, and a protective film A composed of triacetyl cellulose having a thickness of 80 μm and subjected to surface saponification treatment is already applied. On one side, a protective film B having a thickness of 70 μm obtained by stretching a cyclic polyolefin-based resin was bonded. This was dried at 80 ° C. for 30 seconds to produce a polarizing plate.

<Example 2>
Example 1 except that an adhesive composition prepared by dissolving 1 part by weight of zirconium oxycarbonate (Zircosol AC-7, manufactured by Daiichi Rare Element Chemical Co., Ltd.) with respect to 100 parts by weight of water was used. A polarizing plate was produced in the same manner as described above. The pH of the adhesive composition measured in the same manner as in Example 1 was 8.9.

<Example 3>
Except for using an adhesive composition prepared by dissolving 1 part by weight of zirconium oxychloride (Zircosol ZC-2, manufactured by Daiichi Rare Element Chemical Co., Ltd.) with respect to 100 parts by weight of water. In the same manner as in Example 1, a polarizing plate was produced. The pH of the adhesive composition measured in the same manner as in Example 1 was 1.9.

<Example 4>
Example 1 was used except that an adhesive composition prepared by dissolving 1 part by weight of zirconium oxychloride (Zircosol ZC, manufactured by Daiichi Rare Element Chemical Co., Ltd.) with respect to 100 parts by weight of water was used. A polarizing plate was produced. The pH of the adhesive composition measured in the same manner as in Example 1 was 1.7.

<Example 5>
Example 1 with the exception of using an adhesive composition prepared by dissolving 1 part by weight of zirconium oxyacetate (Zircosol ZA-20, manufactured by Daiichi Rare Element Chemical Co., Ltd.) with respect to 100 parts by weight of water. A polarizing plate was produced in the same manner. The pH of the adhesive composition measured in the same manner as in Example 1 was 3.7.

<Example 6>
Example 1 except that an adhesive composition prepared by dissolving 1 part by weight of potassium zirconium oxycarbonate (Zircosol ZK-10, manufactured by Daiichi Rare Element Chemical Co., Ltd.) with respect to 100 parts by weight of water was used. A polarizing plate was produced in the same manner as described above. The pH of the adhesive composition measured in the same manner as in Example 1 was 9.2.

<Comparative Example 1>
In accordance with the description in Example 2 of JP-A-9-318814 (Patent Document 5), first, a polyvinyl alcohol resin (Gosenol AH17, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., degree of saponification: 97 to 98.5 mol%) 100 parts were dissolved in 1900 parts of water to prepare an aqueous solution of a polyvinyl alcohol resin. Next, when zirconium tetra-n-propoxide: acetylacetone = 1: 2 (molar ratio) was added to acetylacetone, zirconium tetra-n-propoxide was precipitated. The part was added dropwise to the aqueous solution of the polyvinyl alcohol resin described above while stirring, and mixed at room temperature (23 ° C.) for 1 hour to prepare an adhesive composition. A polarizing plate was produced in the same manner as in Example 1 except that the adhesive composition thus prepared was used.

<Comparative example 2>
Example 1 was used except that an adhesive composition prepared by dissolving 1 part by weight of copper nitrate hydrate (Cu (NO ₃ ) ₂ .3H ₂ O) per 100 parts by weight of water was used. A polarizing plate was produced. The pH of the adhesive composition measured in the same manner as in Example 1 was 4.3.

<Comparative Example 3>
A polarizing plate was produced in the same manner as in Example 1 except that an adhesive composition prepared by dissolving 0.1 part by weight of potassium permanganate (KMnO ₄ ) with respect to 100 parts by weight of water was used. The pH of the adhesive composition measured in the same manner as in Example 1 was 6.5.

<Comparative example 4>
Example 1 was used except that an adhesive composition prepared by dissolving 1 part by weight of aluminum nitrate hydrate (Al (NO ₃ ) ₃ · 9H ₂ O) with respect to 100 parts by weight of water was used. A polarizing plate was produced. The pH of the adhesive composition measured in the same manner as in Example 1 was 3.4.

<Comparative Example 5>
A polarizing plate was produced in the same manner as in Example 1 except that an adhesive composition prepared by dissolving 1 part by weight of cobalt chloride hydrate (CoCl ₂ .6H ₂ O) per 100 parts by weight of water was used. did. The pH of the adhesive composition measured in the same manner as in Example 1 was 5.5.

<Evaluation test>
The following evaluation test was done about the polarizing plate produced in Examples 1-6 and Comparative Examples 1-5. The results are shown in Table 1.

[1] Appearance evaluation (foaming / discoloration)
The appearance of the adhesive layer in each polarizing plate was visually evaluated, and those having no foaming or discoloration were evaluated as “None”, and those having them were evaluated as “Yes”.

[2] Adhesiveness (cutter evaluation)
After each polarizing plate was allowed to stand at room temperature for 1 hour, a cutter blade was inserted between each film of the polarizing plate (between the polarizing film and the protective film A and between the polarizing film and the protective film B), and the blade was pushed forward. The way of entering the blade was evaluated according to the following criteria.

A: The cutter blade hardly enters between the films.
B: When the blade of the cutter is pushed forward, it stops when the blade enters 4 to 5 mm between the films.

C: When the cutter blade is pushed forward, the blade enters the film without difficulty.
[3] Water resistance Each polarizing plate left for 24 hours in an environment of 23 ° C. and relative humidity 55% was subjected to the following warm water resistance test (warm water immersion test) to evaluate the water resistance. First, a sample was prepared by cutting the polarizing plate into a strip of 5 cm × 2 cm with the absorption axis (stretching direction) of the polarizing plate as the long side, and the dimension in the long side direction was accurately measured. Here, the sample exhibits a unique color uniformly over the entire surface due to iodine adsorbed on the polarizing film. Here, FIG. 1 is a diagram schematically showing a water resistance evaluation test method. FIG. 1 (A) shows sample 1 before hot water immersion, and FIG. 1 (B) shows sample 1 after hot water immersion. Yes. As shown in FIG. 1 (A), one short side of the sample was gripped by the gripping part 5, and about 80% of the longitudinal direction was immersed in a water bath at 60 ° C. and held for 4 hours. Then, the sample 1 was taken out from the water tank, and the water | moisture content was wiped off.

  Due to the warm water immersion, the polarizing film 4 of the polarizing plate contracts. The degree of contraction of the polarizing film 4 was evaluated by measuring the distance from the end 1a of the sample 1 (the end of the protective film) to the end of the contracted polarizing film 4 at the center of the short side of the sample 1 to obtain the contraction length. . As shown in FIG. 1 (B), the polarizing film 4 located in the middle of the polarizing plate is shrunk by hot water immersion, whereby a region 2 where the polarizing film 4 does not exist is formed between the protective films. Moreover, iodine is eluted from the peripheral portion of the polarizing film 4 in contact with the hot water by hot water immersion, and a portion 3 in which the color is lost is generated at the peripheral portion of the sample 1. The degree of color loss was evaluated by measuring the distance from the end of the contracted polarizing film 4 at the center of the short side of the sample 1 to the region where the color peculiar to the polarizing plate remains, and was defined as the iodine loss length. The total of the contraction length and the iodine loss length was defined as the total erosion length X. That is, the total erosion length X is the distance from the end 1a (the end of the protective film) of the sample 1 to the region where the color peculiar to the polarizing plate remains at the center of the short side of the sample 1. It can be determined that the smaller the shrinkage length, the iodine loss length, and the total erosion length X, the higher the adhesion (water resistance) in the presence of water.

  In Table 1, PVA represents a polyvinyl alcohol resin. From Table 1, it can be seen that the polarizing plate of the present invention exhibits sufficient adhesiveness even when the drying time is shortened, and that the erosion from the end portion is small even in the hot water immersion test.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a figure which shows typically the water-resistant evaluation test method, FIG. 1 (A) has shown the sample 1 before warm water immersion, FIG. 1 (B) has shown the sample 1 after warm water immersion.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 The area | region in which the polarizing film between 2 samples and a protective film does not exist, 3 The part from which the color of the polarizing plate peripheral part lost | missed, 4 The contracted polarizing film, 5 Grasp part.

Claims (5)

A polarizing plate in which a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive layer,
The adhesive layer is a polarizing plate formed using an adhesive composition comprising an aqueous solution of an oxyzirconium salt.   The polarizing plate according to claim 1, wherein the weight ratio of the oxyzirconium salt and water in the adhesive composition is 0.1 to 10: 100.   The polarizing plate according to claim 1 or 2, wherein the protective film is composed of a cellulose acetate-based resin or a cycloolefin-based resin.   The protective film comprised from the cellulose acetate type resin was laminated | stacked on the single side | surface of the polarizing film, and the protective film comprised from the cycloolefin resin was laminated | stacked on the single side | surface of the polarizing film. Polarizing plate.   A method for producing a polarizing plate, wherein a protective film is laminated on at least one surface of a polarizing film formed of a polyvinyl alcohol resin via an adhesive composition comprising an aqueous solution of an oxyzirconium salt.

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