JP6107991B2 - Manufacturing method of polarizing plate - Google Patents

Description

  The present invention relates to a method for producing a polarizing plate by laminating a protective film made of a cycloolefin resin via an adhesive on the surface of a polarizing film made of a polyvinyl alcohol resin.

  A polarizing plate is usually a transparent resin film, for example, cellulose acetate represented by triacetyl cellulose, with an adhesive on one or both sides of a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. The film is laminated. This is bonded to a liquid crystal cell with an adhesive via another optical film such as an optical compensation film or a retardation film, if necessary, and becomes a component of a liquid crystal display device.

  Applications of liquid crystal display devices are rapidly expanding as thin display screens such as liquid crystal televisions, liquid crystal monitors, and personal computers. In particular, the market for liquid crystal televisions has been remarkably expanded, and the demand for cost reduction is very strong. Conventionally, a polarizing plate for a liquid crystal television has been obtained by laminating a triacetyl cellulose film with a water-based adhesive on both sides of a polarizing film made of a polyvinyl alcohol resin, and the polarizing plate is placed on one side of the polarizing plate via an adhesive. A phase difference film was laminated. The retardation film laminated on the polarizing plate uses a stretched product of a polycarbonate resin film or a stretched product of a cycloolefin resin film. Retardation films composed of very few cycloolefin resin films are frequently used. For pasted products of polarizing plates and retardation films made of stretched cycloolefin-based resin films, improvements have been made to reduce the number of components and simplify the manufacturing process in order to improve productivity and reduce product costs. It is being advanced. For example, Japanese Patent No. 3807511 (Patent Document 1) discloses a laminated structure of a cycloolefin-based (norbornene-based) resin film / polarizing film / triacetylcellulose film having a retardation function.

  JP-A-2005-70140 (Patent Document 2), JP-A-4432487 (Patent Document 3) and JP-A-2005-208456 (Patent Document 4) disclose a polyvinyl alcohol polarizing film and a cycloolefin-based film. It is described that a resin film is bonded with a urethane-based aqueous adhesive. On the other hand, Japanese Patent No. 4306270 (Patent Document 5) discloses an active energy ray containing an epoxy compound when a protective film having a low moisture permeability such as a cycloolefin resin film is bonded to a polyvinyl alcohol polarizing film. The use of a curable adhesive is described.

  Furthermore, Korean Patent Application Publication No. 2010-92265 (Patent Document 6) includes cyclohexanone, methyl isobutyl ketone, diethyl ether, ethylene oxide, tetrahydrofuran, tetrahydropyran, n-heptane, n-hexane, cresol, toluene, xylene, Disclosed is a method for applying a surface treatment to at least one solution selected from the group consisting of dioctyl phthalate and dimethylformamide, typically an aqueous solution of a compound selected from these groups, on a cycloolefin resin film. Has been. Also disclosed is a method for producing a polarizing plate by bonding the surface-treated cycloolefin resin film to a polyvinyl alcohol polarizing film via an adhesive.

Japanese Patent No. 3807511 (JP-A-8-43812) JP-A-2005-70140 Japanese Patent No. 4432487 (Japanese Patent Laid-Open No. 2005-181817) JP-A-2005-208456 Japanese Patent No. 4306270 (Japanese Patent Laid-Open No. 2004-245925) Korean Patent Application Publication No. 2010-92265

  When a water-based adhesive is used for laminating a polyvinyl alcohol polarizing film and a cycloolefin resin film, the adhesive force between the two is not always sufficient, for example, peeling at the interface between the polarizing film and the cycloolefin resin film. There was a case. Therefore, after placing the polarizing plate on the liquid crystal cell, if it is necessary to reattach the polarizing plate due to a failure of the polarizing plate (called rework), the adhesive that bonds the polarizing plate and the liquid crystal cell Compared to the adhesive strength, the adhesive strength in the laminated structure of the polarizing plate (for example, the adhesive strength between the polarizing film and the cycloolefin-based resin film) becomes relatively small, and the cycloolefin is formed on the glass cell from which the polarizing plate is removed. There is a problem that only the resin is left and the liquid crystal cell cannot be reused.

  According to the method disclosed in Patent Document 6 (Korea Patent Application Publication No. 2010-92265), the adhesion of the cycloolefin resin film to the polyvinyl alcohol polarizing film can be increased, but the surface treatment is performed with an aqueous solution. In that case, after that, a drying furnace maintained at a temperature at which water can be evaporated is required. On the other hand, among organic compounds specifically disclosed in the same document, it may be possible to apply a liquid (organic solvent) that is liquid at room temperature directly to the cycloolefin resin film. May have eroded excessively.

  An object of the present invention is to provide a polarizing plate in which a protective film made of a cycloolefin resin is bonded to a polarizing film made of a polyvinyl alcohol resin via an adhesive, and between the polarizing film and the cycloolefin resin film. It is to improve the adhesive strength of the. Another object of the present invention is to provide a high performance as a polarizing plate by bonding to a polyvinyl alcohol polarizing film through an adhesive in a state where the cycloolefin resin film is treated without excessive erosion. It is in improving the adhesive force between a polarizing film and a cycloolefin type-resin film, maintaining this.

  As a result of research, when contacting a cycloolefin resin film, the organic solvent that changes the cycloolefin resin film, and when contacting the cycloolefin resin film, the cycloolefin resin film is not substantially changed. It has been found that it is effective to use a mixture with an organic solvent and treat the cycloolefin resin film so that the haze value does not exceed 0.5%. In addition, among organic solvents that change the cycloolefin-based resin by contact, if it is an alicyclic hydrocarbon, it is effective alone for the treatment of the cycloolefin-based resin film, and together with the alicyclic hydrocarbon, It has also been found that the use of an organic solvent that does not substantially change the cycloolefin-based resin by contact is more effective.

  That is, the present invention, from one point of view, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin is bonded with a protective film made of a cycloolefin resin via an adhesive. A protective film made of the cycloolefin resin is an organic solvent that changes the cycloolefin resin by contact with an organic solvent that does not substantially change the cycloolefin resin by contact. The mixture is contacted with a mixed organic solvent substantially free of solute, treated so that the haze value of the protective film does not exceed 0.5%, and then bonded to the polarizing film via the adhesive. The manufacturing method of the polarizing plate to be provided is provided.

  In another aspect, the present invention provides a first protective film made of a cycloolefin resin on one side of a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin, and the other side of the polarizing film. Is a method for producing a polarizing plate by bonding a second protective film made of a thermoplastic resin via an adhesive, respectively, wherein the first protective film made of the cycloolefin resin is contacted Contacting with a mixed organic solvent substantially free of solute in a mixture with an organic solvent that does not substantially change the cycloolefin resin by contact with an organic solvent that changes the cycloolefin resin; A method for producing a polarizing plate, in which the haze value of the protective film is processed so as not to exceed 0.5% and then bonded to the polarizing film via the adhesive Also it is intended to provide.

  From another standpoint, the present invention also includes a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin and a protective film made of a cycloolefin resin is bonded to the polarizing film through an adhesive. A protective film made of the above cycloolefin-based resin is contacted with an organic solvent containing an alicyclic hydrocarbon and substantially free of a solute, and the protective film has a haze value of 0.5%. After the process is performed so as not to exceed the above, a method for producing a polarizing plate to be bonded to the polarizing film via the adhesive is provided.

  In another aspect, the present invention also provides a first protective film comprising a cycloolefin resin on one side of a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin, and the other of the polarizing films. A second protective film made of a thermoplastic resin is bonded to each surface via an adhesive, and a polarizing plate is produced. The first protective film made of the cycloolefin resin is Contact with an organic solvent containing alicyclic hydrocarbons and substantially free of solutes, treating the first protective film so that the haze value does not exceed 0.5%, and then passing through the adhesive. The manufacturing method of the polarizing plate bonded to the said polarizing film is also provided.

  The alicyclic hydrocarbon used as the solvent is typically represented by the following formula (I), wherein m is an integer of 2 to 6, and R is a hydrogen atom or an alkyl having 1 to 5 carbon atoms. It can be a compound that is a group.

  In the case of using alicyclic hydrocarbon as the solvent, it is advantageous to use a mixed solvent further containing an organic solvent that does not substantially change the cycloolefin resin by contact in addition to the alicyclic hydrocarbon. In this case, the organic solvent that does not substantially change the cycloolefin resin by contact is preferably an alkyl ester of an organic acid, which is also an acetate ester, and examples thereof include ethyl acetate, isopropyl acetate, and propyl acetate. be able to.

  In each of the above production methods, the protective film made of a cycloolefin resin has an in-plane retardation value of 30 nm or more before being treated with an organic solvent, and the in-plane retardation value after the treatment is Processing is performed so as not to exceed 3 nm beyond the in-plane retardation value before the processing.

  In each of the above production methods, when the protective film made of a cycloolefin resin is treated with the organic solvent, it is preferable to simultaneously perform an operation of drying the organic solvent. The adhesive used in these production methods is preferably a water-based adhesive, and more preferably a water-based adhesive containing a polyvinyl alcohol-based resin.

  According to the present invention, in a polarizing plate in which a protective film made of a cycloolefin resin is bonded to a polarizing film made of a polyvinyl alcohol resin through an adhesive, the adhesion between the polarizing film and the cycloolefin resin film is achieved. You can increase your power. In particular, it is possible to produce a polarizing plate in which the erosion of the cycloolefin-based resin film is suppressed and the adhesive strength between the polarizing film and the cycloolefin-based resin film is improved while maintaining high performance as a polarizing plate. .

  In the present invention, a polarizing film in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin is bonded to a protective film made of a cycloolefin resin via an adhesive to obtain a polarizing plate. The cycloolefin resin film may be bonded to both sides of the polarizing film or may be bonded to one side. When a cycloolefin-based resin film is bonded to one surface of the polarizing film, it is preferable that a protective film made of another thermoplastic resin is bonded to the opposite surface via an adhesive. Hereinafter, a protective film made of a cycloolefin resin may be referred to as a “first protective film”, and a protective film made of another thermoplastic resin may be called a “second protective film”. First, each structural member of the polarizing plate manufactured by this invention is demonstrated.

[Polarized film]
Specifically, the polarizing film used in the present invention is one in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol-based resin film. By uniaxially stretching the polyvinyl alcohol-based resin film before, during or after the adsorption of the dichroic dye, the dichroic dye can be oriented in the stretching direction. The polyvinyl alcohol resin can be obtained by saponifying a polyvinyl acetate resin. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers of vinyl acetate and other monomers copolymerizable therewith, such as ethylene-vinyl acetate copolymer. Etc. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins including ethylene, vinyl ethers, and acrylamides having an ammonium group.

  The degree of saponification of the polyvinyl alcohol resin is usually 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol-based resin may be modified, for example, polyvinyl formal modified with aldehydes, polyvinyl acetal, polyvinyl butyral, and the like may be used. The degree of polymerization of the polyvinyl alcohol resin is usually in the range of 1,000 to 10,000, preferably in the range of 1,500 to 5,000.

  A film obtained by forming such a polyvinyl alcohol resin is used as a raw film of a polarizing film. The method for forming the polyvinyl alcohol-based resin is not particularly limited, and can be formed by a conventionally known appropriate method. Although the film thickness of the raw film which consists of polyvinyl alcohol-type resin is not specifically limited, For example, it is about 10-150 micrometers.

  A polarizing film usually includes a process of dyeing a polyvinyl alcohol resin film with a dichroic dye and adsorbing the dichroic dye (dyeing process), and a polyvinyl alcohol resin film on which the dichroic dye is adsorbed. It is manufactured through a step of treating with an acid aqueous solution (boric acid treatment step) and a step of washing with water after the treatment with the boric acid aqueous solution (water washing treatment step).

  In addition, in the production of the polarizing film, the polyvinyl alcohol-based resin film is uniaxially stretched, but this uniaxial stretching may be performed before the dyeing process, or may be performed during the dyeing process, or the dyeing process. It may be performed after the process. When uniaxial stretching is performed after the dyeing treatment step, this uniaxial stretching may be performed before the boric acid treatment step or during the boric acid treatment step. Of course, it is also possible to perform uniaxial stretching in these plural stages. Uniaxial stretching may be performed by passing between spaced apart rolls having different peripheral speeds, or may be performed by a method of sandwiching with hot rolls. Moreover, the dry-type extending | stretching which extends | stretches in air | atmosphere may be sufficient, and the wet extending | stretching which extends | stretches in the state swollen with the solvent may be sufficient. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film is dyed with a dichroic dye, for example, by immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. The dichroic organic dye includes dichroic direct dyes composed of disazo compounds such as C.I. DIRECT RED 39, and dichroic direct dyes composed of compounds such as trisazo and tetrakisazo. 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-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The iodine content in this aqueous solution is usually 0.01 to 1 part by weight per 100 parts by weight of water, and the potassium iodide content is usually 0.5 to 20 parts by weight per 100 parts by weight of water. . When iodine is used as the dichroic dye, 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 1,800 seconds. is there.

On the other hand, when a dichroic organic 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 organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight, more preferably 1 × 10 10 per 100 parts by weight of water. ⁻³ to 1 × 10 ⁻² parts by weight. This aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. When a dichroic organic dye is used as the dichroic dye, 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 10 ° C. 1,800 seconds.

  The boric acid treatment step is performed by immersing a polyvinyl alcohol resin film dyed with a dichroic dye in an aqueous boric acid solution. The boric acid content in the boric acid 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 in the dyeing process described above, the boric acid aqueous solution used in this process preferably contains potassium iodide. In this case, the content of potassium iodide in the boric acid 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 aqueous solution is usually 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  In the subsequent washing process, the polyvinyl alcohol resin film after the boric acid treatment described above is washed with water, for example, by immersing it 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 the water washing treatment, usually a drying treatment is performed to obtain a polarizing film. The drying process can be performed using, for example, a hot air dryer or 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.

  As described above, it is possible to produce a polarizing film in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol resin film. The thickness of the polarizing film can be about 5 to 40 μm.

[Cycloolefin resin film]
In this invention, the 1st protective film provided in at least one surface of a polarizing film is comprised with a cycloolefin type resin film, and the cycloolefin type resin film is bonded to a polarizing film through an adhesive agent.

  The cycloolefin-based resin is a thermoplastic resin having a monomer unit made of a cyclic olefin (cycloolefin) such as norbornene or a polycyclic norbornene-based monomer, and is also called a thermoplastic cycloolefin-based resin. The cycloolefin-based resin may be a hydrogenated product of the above-mentioned cycloolefin ring-opening polymer or a ring-opening copolymer using two or more kinds of cycloolefins. Cycloolefin, chain olefin, vinyl It may be an addition polymer with an aromatic compound having a polymerizable double bond such as a group. A polar group may be introduced into the cycloolefin resin.

  When the first protective film is formed using a copolymer of a cycloolefin and an aromatic compound having a chain olefin and / or vinyl group, examples of the chain olefin include ethylene and propylene. Examples of the aromatic compound having a vinyl group 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, but is preferably about 15 to 50 mol%. In particular, when the first protective film is formed using a terpolymer of cycloolefin, chain olefin, and aromatic compound having a vinyl group, the monomer unit composed of cycloolefin is compared as described above. Less amount. 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%.

  For the cycloolefin resin film, an appropriate commercial product can be used. For example, “TOPAS” produced by TOPAS ADVANCED POLYMERS GmbH in Germany and sold by Polyplastics Co., Ltd. in Japan, JSR Co., Ltd. "Arton" sold by Zeon Corporation, "ZEONOR" and "ZEONEX" sold by Nippon Zeon Co., Ltd., "Appel" sold by Mitsui Chemicals, Inc. Can also be mentioned. In order to form such a cycloolefin-based resin into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. Also, for example, “Essina” and “SCA40” sold by Sekisui Chemical Co., Ltd., “Zeonor Film” sold by Nippon Zeon Co., Ltd., “Arton Film” sold by JSR Co., Ltd. A commercial product of a pre-formed cycloolefin-based resin film such as “(all are trade names)” may be used as the first protective film.

  The cycloolefin resin film used for the first protective film has an in-plane retardation value of 30 nm or more before being treated with an organic solvent. In order to give an in-plane retardation value of 30 nm or more to the cycloolefin-based resin film before being treated with the organic solvent, uniaxial stretching or biaxial stretching may be performed. In this case, the draw ratio is usually 1.1 to 5 times, preferably 1.1 to 3 times. By this stretching, a retardation can be imparted to obtain a retardation film. The upper limit of the in-plane retardation value is not particularly limited, but for example up to about 300 nm is sufficient.

  The cycloolefin-based resin film used for the first protective film is preferably thin, but if it is too thin, the strength tends to decrease and the processability tends to be inferior. On the other hand, if it is too thick, the transparency may decrease, It tends to increase in weight. From this point of view, the thickness of the protective film made of cycloolefin resin is usually 5 to 200 μm, preferably 10 to 150 μm, more preferably 20 to 100 μm.

  The protective film made of cycloolefin-based resin is attached to the polarizing film using an adhesive as described in detail below. In adhering both, plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification are performed on the adhesive surface of the polarizing film and / or the protective film to be bonded to it in order to improve the adhesion. Surface treatment such as treatment may be appropriately performed. Hereinafter, the adhesive used for adhering the polarizing film and the cycloolefin-based resin film will be described.

[adhesive]
An adhesive is used for adhering the polarizing film and the cycloolefin-based resin film. The adhesive used for this purpose only needs to exhibit adhesive strength to both, and includes, for example, an aqueous adhesive in which an adhesive component is dissolved or dispersed in water or an active energy ray-curable compound. And a curable adhesive. Considering that the surface of the polarizing film is hydrophilic, an aqueous adhesive in which an adhesive component is dissolved or dispersed in water is preferable. The water-based adhesive is also preferable from the viewpoint of thinning the cured adhesive layer. Examples of the adhesive component that is the main component of the water-based adhesive include polyvinyl alcohol resins and urethane resins.

  When a polyvinyl alcohol resin is used as the main component of the aqueous adhesive, the polyvinyl alcohol resin 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 polyvinyl alcohol resin used for the adhesive preferably has an appropriate degree of polymerization. For example, when the aqueous solution has a concentration of 4% by weight, the viscosity is in the range of 4 to 50 mPa · sec, and further 6 More preferably, it is in the range of ˜30 mPa · sec.

  The saponification degree of the polyvinyl alcohol-based resin used for the adhesive is not particularly limited, but is generally preferably 80 mol% or more, and more preferably 90 mol% or more. If the degree of saponification of the polyvinyl alcohol resin used for the adhesive is low, the water resistance of the resulting adhesive layer tends to be insufficient.

  For the adhesive, a modified polyvinyl alcohol-based resin is preferably used. Suitable modified polyvinyl alcohol resins include acetoacetyl group-modified polyvinyl alcohol resins, anion-modified polyvinyl alcohol resins, and cation-modified polyvinyl alcohol resins. If such a modified polyvinyl alcohol resin is used, the effect of improving the water resistance of the adhesive layer can be easily obtained.

The acetoacetyl group-modified polyvinyl alcohol resin has an acetoacetyl group (CH ₃ COCH ₂ CO—) in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton, and has other groups such as an acetyl group. You may do it. This acetoacetyl group typically exists in a state in which a hydrogen atom of a hydroxyl group constituting polyvinyl alcohol is substituted. An acetoacetyl group-modified polyvinyl alcohol resin can be produced, for example, by a method of reacting polyvinyl alcohol with diketene. The acetoacetyl group-modified polyvinyl alcohol-based resin has an acetoacetyl group that is a highly reactive functional group, and thus is preferable for improving the durability of the adhesive layer.

  The content of the acetoacetyl group in the polyvinyl alcohol resin modified with acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. The content of the acetoacetyl group here is a value in which the mole fraction of the acetoacetyl group relative to the total amount of the hydroxyl group, acetoacetyl group, and other ester groups (acetyl group, etc.) in the polyvinyl alcohol resin is expressed in%. And may be referred to as “degree of acetoacetylation”. When the degree of acetoacetylation in the polyvinyl alcohol-based resin is less than 0.1 mol%, the effect of improving the water resistance of the adhesive layer is not always sufficient. The degree of acetoacetylation in the polyvinyl alcohol resin is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. When the degree of acetoacetylation exceeds 40 mol%, the effect of improving water resistance becomes small.

  An anion-modified polyvinyl alcohol-based resin contains an anionic group, typically a carboxyl group (—COOH) or a salt thereof, in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton. It may have an acetyl group or the like. An anion-modified polyvinyl alcohol resin can be produced, for example, by a method in which an unsaturated monomer having an anionic group (typically a carboxyl group) is copolymerized with vinyl acetate and then saponified. . On the other hand, a cation-modified polyvinyl alcohol-based resin contains a cationic group, typically a tertiary amino group or a quaternary ammonium group, in addition to the hydroxyl group constituting the polyvinyl alcohol skeleton. For example, it may have an acetyl group. The cation-modified polyvinyl alcohol resin is, for example, a method in which an unsaturated monomer having a cationic group (typically a tertiary amino group or a quaternary ammonium group) is copolymerized with vinyl acetate and then saponified. Can be manufactured.

  Of course, the adhesive used in the present invention may contain two or more of the above-mentioned modified polyvinyl alcohol-based resins, and may also be an unmodified polyvinyl alcohol-based resin (specifically, It may contain both a partially saponified product) and the above-described modified polyvinyl alcohol resin.

  The polyvinyl alcohol-based resin constituting the adhesive can be used by appropriately selecting from commercially available products. Specifically, for example, polyvinyl alcohol having a high degree of saponification, such as “PVA-117H” sold by Kuraray Co., Ltd. and “Gosenol NH” sold by Nippon Synthetic Chemical Industry Co., Ltd. -20 ", polyvinyl alcohol modified with acetoacetyl group," Gosefimer Z "series sold by Nippon Synthetic Chemical Industry Co., Ltd., anion-modified polyvinyl alcohol, Kuraray Co., Ltd. "KL-318" and "KM-118" sold by KK, "Gosenal T-330" sold by Nippon Synthetic Chemical Industry Co., Ltd., cation-modified polyvinyl alcohol, Examples include “CM-318” sold by Kuraray and “Gosefimer K-210” sold by Nippon Synthetic Chemical Industry.

  The concentration of the polyvinyl alcohol resin in the adhesive is not particularly limited, but since it is used in the form of an aqueous solution, the polyvinyl alcohol resin should be in the range of 1 to 20 parts by weight with respect to 100 parts by weight of water. Among these, 1 to 15 parts by weight, more preferably 1 to 10 parts by weight, and particularly 2 to 10 parts by weight are more preferable. If the concentration of the polyvinyl alcohol-based resin in the aqueous solution is too small, the adhesiveness tends to decrease. On the other hand, if the concentration is too large, the optical properties of the resulting polarizing plate tend to decrease. The water used for the adhesive can be pure water, ultrapure water, tap water, etc., and is not particularly limited. However, from the viewpoint of maintaining the uniformity and transparency of the formed adhesive layer, Water or ultrapure water is preferred. Alcohols such as methanol and ethanol can also be added to the adhesive aqueous solution.

  A water-based adhesive mainly composed of a polyvinyl alcohol resin can contain a crosslinking agent. The cross-linking agent may be a compound having a functional group having reactivity with a polyvinyl alcohol resin, and those conventionally used in polyvinyl alcohol adhesives can be used without particular limitation. When compounds capable of forming a crosslinking agent are listed by functional group, an isocyanate compound having at least two isocyanato groups (—NCO) in the molecule; an epoxy compound having at least two epoxy groups (crosslinked —O—) in the molecule; Mono- or di-aldehydes; organic titanium compounds; inorganic salts of divalent or trivalent metals such as magnesium, calcium, iron, nickel, zinc, and aluminum; metal salts of glyoxylic acid; methylol melamine;

  Specific examples of the isocyanate compound used as the crosslinking agent include tolylene diisocyanate, hydrogenated tolylene diisocyanate, adducts of trimethylolpropane and tolylene diisocyanate, diphenylmethane diisocyanate, triphenylmethane triisocyanate, isophorone diisocyanate, and ketoximes thereof. A block thing or a phenol block thing etc. are mentioned.

  Specific examples of the epoxy compound serving as a crosslinking agent include ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, di- or tri-glycidyl ether of glycerin, 1,6-hexanediol diglycidyl ether, trimethylolpropane triglycidyl ether. , Diglycidyl aniline, diglycidyl amine, water-soluble polyamide epoxy resin obtained by reacting epichlorohydrin with polyamide polyamine which is a reaction product of polyalkylene polyamine and dicarboxylic acid.

  Specific examples of monoaldehydes that serve as crosslinking agents include formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde, and specific examples of dialdehydes include glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, Maleic dialdehyde, phthaldialdehyde and the like can be mentioned.

  Various organic titanium compounds that serve as crosslinking agents are sold by Matsumoto Fine Chemical Co., Ltd. It is suitable for the present invention from the company's home page related to organic titanium compounds (Internet <URL: http://www.m-chem.co.jp/products/products1.html>, retrieved on November 18, 2010) The water-soluble organotitanium compounds used are listed below in the order of their formula, chemical name, and product name.

[(CH ₃ ) ₂ CHO] ₂ Ti [OCH ₂ CH ₂ N (CH ₂ CH ₂ OH) ₂ ] ₂ : Chemical name "Titanium diisopropoxybis (triethanolaminate)", the company's product name “Orgachicks TC-400”,
(HO) ₂ Ti [OCH (CH ₃ ) COO ⁻ ] ₂ (NH ₄ ⁺ ) ₂ : Chemical name “Titanium lactate ammonium salt”, the company's product name “OrgaTix TC-300”,
(HO) ₂ Ti [OCH (CH ₃ ) COOH] ₂ : Chemical name “titanium lactate”, the company name “Orgachix TC-310” and “Orgachix TC-315”.

  The metal salt of glyoxylic acid is preferably an alkali metal salt or an alkaline earth metal salt, and examples thereof include sodium glyoxylate, potassium glyoxylate, magnesium glyoxylate, and calcium glyoxylate.

  Among these crosslinking agents, epoxy compounds including the above-mentioned water-soluble polyamide epoxy resins, aldehydes, methylol melamine, alkali metal or alkaline earth metal salts of glyoxylic acid, and the like are preferably used.

  The crosslinking agent is preferably dissolved in water together with the polyvinyl alcohol resin to form an adhesive. However, since the amount of the crosslinking agent in the aqueous solution may be small as described below, any crosslinking agent having a solubility of at least about 0.1% by weight in water can be used. Of course, a compound having a solubility in water of a level generally called water solubility is more suitable as a crosslinking agent used in the present invention.

  The amount of the crosslinking agent is appropriately designed according to the type of the polyvinyl alcohol resin and the like, but is usually about 5 to 60 parts by weight, preferably 10 to 50 parts per 100 parts by weight of the polyvinyl alcohol resin. Parts by weight. When the crosslinking agent is blended within this range, good adhesiveness can be obtained. As described above, in order to improve the durability of the adhesive layer, an acetoacetyl group-modified polyvinyl alcohol-based resin is preferably used. In this case as well, crosslinking is performed with respect to 100 parts by weight of the polyvinyl alcohol-based resin. It is preferable to blend the agent in a proportion of 5 to 60 parts by weight, more preferably 10 to 50 parts by weight. If the amount of the cross-linking agent is too large, the reaction of the cross-linking agent proceeds in a short time and the adhesive tends to gel early, resulting in extremely short pot life and industrial use. It becomes difficult.

  The adhesive may be blended with conventionally known appropriate additives such as a silane coupling agent, a plasticizer, an antistatic agent, and fine particles as long as the effects of the present invention are not impaired.

  When a urethane resin is used as the main component of the water-based adhesive, an example of a suitable adhesive is a mixture of a polyester ionomer type urethane resin and a compound having a glycidyloxy group. The polyester ionomer type urethane resin here is a urethane resin having a polyester skeleton, into which a small amount of ionic component (hydrophilic component) is introduced. Such an ionomer type urethane resin is suitably used for an aqueous adhesive because it is emulsified directly in water without using an emulsifier to form an emulsion. The use of a polyester ionomer type urethane resin as an adhesive for a polarizing film and a protective film is, for example, disclosed in Patent Document 2 (Japanese Patent Laid-Open No. 2005-070140), Patent Document 3 (Japanese Patent No. 4432487), and Patent Document 4 (Japanese Patent Laid-Open No. 2005-208456).

  A curable adhesive containing an active energy ray-curable compound can also be used for adhering the polarizing film and the cycloolefin-based resin film. The “active energy ray-curable compound” means a compound that can be cured by irradiation with active energy rays. The active energy ray-curable compound may be cationically polymerizable or radically polymerizable. Examples of the cationic polymerizable compound include an epoxy compound having at least one epoxy group in the molecule, an oxetane compound having at least one oxetane ring in the molecule, and the like. Examples of the radical polymerizable compound include (meth) acrylic compounds having at least one (meth) acryloyloxy group in the molecule. The “(meth) acryloyloxy group” means a methacryloyloxy group or an acryloyloxy group.

  The active energy ray-curable compound used for this sticking preferably contains at least an epoxy compound, and thereby exhibits good adhesion between the polarizing film and the cycloolefin-based resin film.

  From the viewpoint of weather resistance, refractive index, cationic polymerizability, and the like, the epoxy compound preferably contains an epoxy compound containing no aromatic ring in the molecule as a main component. Examples of the epoxy compound that does not contain an aromatic ring in the molecule include glycidyl ether of a polyol having an alicyclic ring, an aliphatic epoxy compound, and an alicyclic epoxy compound. The epoxy compound suitably used for such a curable adhesive is described in detail in, for example, the above-mentioned Patent Document 5 (Patent No. 4306270), but the outline is also described here.

  The glycidyl ether of a polyol having an alicyclic ring is a glycidyl etherification of a nuclear hydrogenated polyhydroxy compound obtained by selectively hydrogenating an aromatic polyol under pressure in the presence of a catalyst. Can be. Examples of the aromatic polyol include bisphenol type compounds such as bisphenol A, bispheel F, and bisphenol S; novolac type resins such as phenol novolac resin, cresol novolac resin, and hydroxybenzaldehyde phenol novolac resin; Examples thereof include tetrahydroxybenzophenone and polyfunctional compounds such as polyvinylphenol. Glycidyl ether can be obtained by reacting an alicyclic polyol obtained by hydrogenating the aromatic ring of these aromatic polyols with epichlorohydrin. Among these glycidyl ethers of polyols having an alicyclic ring, hydrogenated bisphenol A diglycidyl ether is preferable.

  The aliphatic epoxy compound can be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, 1,4-butanediol diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerin triglycidyl ether; trimethylolpropane triglycidyl ether; polyethylene glycol diglycidyl ether; propylene Diglycidyl ether of glycol; Polyether polyol obtained by adding one or more alkylene oxides (ethylene oxide or propylene oxide) to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol or glycerin Examples thereof include glycidyl ether.

  An alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in the molecule. Here, the “epoxy group bonded to the alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula (II), wherein n is an integer of 2 to 5. is there.

A compound in which a group in a form in which one or a plurality of hydrogen atoms in (CH ₂ ) _n in formula (II) are removed is bonded to another chemical structure can be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _n forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group.

  Among the epoxy compounds as described above, an alicyclic epoxy compound, that is, a compound in which at least one of the epoxy groups is bonded to the alicyclic ring is preferable, and in particular, an oxabicyclohexane ring [the above formula (II) In which n = 3] and an oxabicycloheptane ring [n = 4 in the above formula (II)] have a high elastic modulus of the cured product and good adhesion between the polarizing film and the protective film. From the viewpoint of imparting sex, it is more preferably used. Specific examples of the alicyclic epoxy compound are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.2.5.2] henicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide,
K: Limonene dioxide
L: bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxide and the like.

  In the curable adhesive, the epoxy compound may be used alone or in combination of two or more.

  The curable adhesive may contain an oxetane compound in addition to the epoxy compound. By adding an oxetane compound, the viscosity of the curable adhesive can be lowered and the curing speed can be increased.

  The oxetane compound is a compound having at least one oxetane ring (four-membered ether) in the molecule, such as 3-ethyl-3-hydroxymethyloxetane, 1,4-bis [(3-ethyl-3 -Oxetanyl) methoxymethyl] benzene, 3-ethyl-3- (phenoxymethyl) oxetane, di [(3-ethyl-3-oxetanyl) methyl] ether, 3-ethyl-3- (2-ethylhexyloxymethyl) oxetane And phenol novolac oxetane. These oxetane compounds can be easily obtained as commercial products. For example, “Aron Oxetane OXT-101” and “Aron Oxetane OXT-” are trade names sold by Toagosei Co., Ltd. 121 ”,“ Aron Oxetane OXT-211 ”,“ Aron Oxetane OXT-221 ”,“ Aron Oxetane OXT-212 ”and the like. Although the compounding quantity of an oxetane compound is not specifically limited, It is 50 weight% or less normally based on the whole active energy ray hardening compound, Preferably it is 10 to 40 weight%.

  When the curable adhesive contains a cationically polymerizable compound such as an epoxy compound or an oxetane compound, a photocationic polymerization initiator is usually added to the curable adhesive. When a cationic photopolymerization initiator is used, it is possible to form an adhesive layer at room temperature, reducing the need to consider the heat resistance of the polarizing film and distortion due to expansion, and sticking the polarizing film and the protective film with good adhesion. Yes. Moreover, since a photocationic polymerization initiator acts catalytically with light, even if it is mixed with a curable adhesive, the curable adhesive is excellent in storage stability and workability.

  The cationic photopolymerization initiator generates a cationic species or a Lewis acid by irradiation with active energy rays such as visible light, ultraviolet rays, X-rays, or electron beams, and initiates a polymerization reaction of the cationically polymerizable compound. The photocationic polymerization initiator may be of any type, but specific examples include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts; iron-arene complexes, etc. There is.

Examples of the aromatic diazonium salt include the following compounds.
Benzenediazonium hexafluoroantimonate,
Benzenediazonium hexafluorophosphate,
Benzenediazonium hexafluoroborate, etc.

Examples of the aromatic iodonium salt include the following compounds.
Diphenyliodonium tetrakis (pentafluorophenyl) borate,
Diphenyliodonium hexafluorophosphate,
Diphenyliodonium hexafluoroantimonate,
Di (4-nonylphenyl) iodonium hexafluorophosphate and the like.

Examples of the aromatic sulfonium salt include the following compounds.
Triphenylsulfonium hexafluorophosphate,
Triphenylsulfonium hexafluoroantimonate,
Triphenylsulfonium tetrakis (pentafluorophenyl) borate,
4,4'-bis [diphenylsulfonio] diphenyl sulfide bishexafluorophosphate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluoroantimonate,
4,4′-bis [di (β-hydroxyethoxy) phenylsulfonio] diphenyl sulfide bishexafluorophosphate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone hexafluoroantimonate,
7- [di (p-toluyl) sulfonio] -2-isopropylthioxanthone tetrakis (pentafluorophenyl) borate,
4-phenylcarbonyl-4'-diphenylsulfonio-diphenyl sulfide hexafluorophosphate,
4- (p-tert-butylphenylcarbonyl) -4'-diphenylsulfonio-diphenyl sulfide hexafluoroantimonate,
4- (p-tert-butylphenylcarbonyl) -4'-di (p-toluyl) sulfonio-diphenyl sulfide tetrakis (pentafluorophenyl) borate and the like.

Moreover, as an iron-arene complex, the following compounds are mentioned, for example.
Xylene-cyclopentadienyl iron (II) hexafluoroantimonate,
Cumene-cyclopentadienyl iron (II) hexafluorophosphate,
Xylene-cyclopentadienyl iron (II) tris (trifluoromethylsulfonyl) methanide.

  These photocationic polymerization initiators can be easily obtained as commercial products. For example, “Kayarad PCI-220” and “Kayarad PCI-620” sold by Nippon Kayaku Co., Ltd. under the trade names, respectively. "UVI-6990" sold by Union Carbide, "UVACURE 1590" sold by Daicel Cytec, "Adekaoptomer SP-150" sold by ADEKA, and “Adekaoptomer SP-170”, “CI-5102”, “CIT-1370”, “CIT-1682”, “CIP-1866S”, “CIP-2048S” and “Sold by Nippon Soda Co., Ltd.” "CIP-2064S", "DPI-101", "DPI-102", "DPI-103", "DPI-105", "MPI-103", "MPI-105" sold by Midori Chemical Co., Ltd. , “BBI-101”, “BBI-102”, “BBI-103”, “BBI-105”, “TPS-101”, “TPS-102”, “TPS-103”, “TPS-105”, “ MDS-103 ”, MDS-105 "," DTS-102 "and" DTS-103, and the like PI-2074 "", sold by Rhodia ".

  These photocationic polymerization initiators may be used alone or in combination of two or more. Among these, in particular, the aromatic sulfonium salt has an ultraviolet absorption property even in a wavelength region of 300 nm or more, so it has excellent curability, gives good mechanical strength, and is good between the polarizing film and the protective film. Since it can give the hardened | cured material which has adhesiveness, it is used preferably.

  The compounding amount of the cationic photopolymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 to 6 parts by weight, based on 100 parts by weight of the total of the cationic polymerizable compounds including the epoxy compound and the oxetane compound. is there. If the amount of the cationic photopolymerization initiator is small, the curing becomes insufficient, and the mechanical strength and the adhesion between the polarizing film and the protective film tend to be lowered. On the other hand, if the amount of the cationic photopolymerization initiator is too large, the amount of ionic substances in the cured product will increase, resulting in an increase in the hygroscopicity of the cured product, which may reduce the durability of the resulting adhesive layer. is there.

  Moreover, the curable adhesive may contain a radically polymerizable (meth) acrylic compound together with the epoxy compound or together with the epoxy compound and the oxetane compound. By using a (meth) acrylic compound in combination, the effect of increasing the hardness and mechanical strength of the adhesive layer can be expected, and furthermore the adjustment of the viscosity and curing speed of the curable adhesive can be performed more easily. Become.

  The (meth) acrylic compound is obtained by reacting at least one (meth) acrylate monomer having at least one (meth) acryloyloxy group in the molecule or a compound having a functional group, and at least in the molecule. Examples include (meth) acrylate oligomers having two (meth) acryloyloxy groups. These may be used alone or in combination of two or more. When two or more types are used in combination, two or more types of (meth) acrylate monomers may be used, or two or more types of (meth) acrylate oligomers may be used. Of course, one or more types of (meth) acrylate monomers may be used. And one or more (meth) acrylate oligomers may be used in combination. “(Meth) acrylate” means acrylate or methacrylate.

  The above (meth) acrylate monomer includes a monofunctional (meth) acrylate monomer having one (meth) acryloyloxy group in the molecule, and a bifunctional (meth) acrylate having two (meth) acryloyloxy groups in the molecule. ) Acrylate monomers and polyfunctional (meth) acrylate monomers having three or more (meth) acryloyloxy groups in the molecule.

  Specific examples of monofunctional (meth) acrylate monomers include tetrahydrofurfuryl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2- or 3-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate. 2-hydroxy-3-phenoxypropyl (meth) acrylate, isobutyl (meth) acrylate, tert-butyl (meth) acrylate, 2-ethylhexyl (meth) acrylate, cyclohexyl (meth) acrylate, dicyclopentenyl (meth) acrylate, Benzyl (meth) acrylate, isobornyl (meth) acrylate, phenoxyethyl (meth) acrylate, dicyclopentenyloxyethyl (meth) acrylate, dimethylaminoethyl (meth) acrylate , Ethyl carbitol (meth) acrylate, trimethylolpropane mono (meth) acrylate, pentaerythritol mono (meth) acrylate, phenoxypolyethylene glycol (meth) acrylate, and the like.

  As the monofunctional (meth) acrylate monomer, a carboxyl group-containing (meth) acrylate monomer may be used. Examples of the carboxyl group-containing monofunctional (meth) acrylate monomer include 2- (meth) acryloyloxyethyl phthalic acid, 2- (meth) acryloyloxyethyl hexahydrophthalic acid, carboxyethyl (meth) acrylate, and 2- (meth). Examples include acryloyloxyethyl succinic acid, N- (meth) acryloyloxy-N ′, N′-dicarboxymethyl-p-phenylenediamine, and 4- (meth) acryloyloxyethyl trimellitic acid.

  Bifunctional (meth) acrylate monomers include alkylene glycol di (meth) acrylates, polyoxyalkylene glycol di (meth) acrylates, halogen-substituted alkylene glycol di (meth) acrylates, aliphatic polyol di (meth) acrylates Di (meth) acrylates of hydrogenated dicyclopentadiene or tricyclodecane dialkanol, di (meth) acrylates of dioxane glycol or dioxane dialkanol, di (meth) of alkylene oxide adducts of bisphenol A or bisphenol F Representative examples include acrylates, epoxy di (meth) acrylates of bisphenol A or bisphenol F, and the like.

  More specific examples of the bifunctional (meth) acrylate monomer include ethylene glycol di (meth) acrylate, 1,3-butanediol di (meth) acrylate, 1,4-butanediol di (meth) acrylate, 1 , 6-hexanediol di (meth) acrylate, 1,9-nonanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol di (meth) acrylate, ditri Methylolpropane di (meth) acrylate, diethylene glycol di (meth) acrylate, triethylene glycol di (meth) acrylate, dipropylene glycol di (meth) acrylate, tripropylene glycol di (meth) acrylate, polyethylene Glycol di (meth) acrylate, polypropylene glycol di (meth) acrylate, polytetramethylene glycol di (meth) acrylate, silicone di (meth) acrylate, di (meth) acrylate of hydroxypivalic acid neopentyl glycol ester, 2,2 -Bis [4- (meth) acryloyloxyethoxyethoxyphenyl] propane, 2,2-bis [4- (meth) acryloyloxyethoxyethoxycyclohexyl] propane, hydrogenated dicyclopentadienyl di (meth) acrylate, tricyclo Decanedimethanol di (meth) acrylate, 1,3-dioxane-2,5-diyldi (meth) acrylate [also known as dioxane glycol di (meth) acrylate], hydroxypivalaldehyde and trimethylo Acetal compound with propane [chemical name: 2- (2-hydroxy-1,1-dimethylethyl) -5-ethyl-5-hydroxymethyl-1,3-dioxane], di (meth) acrylate, tris (hydroxyethyl) ) Isocyanurate di (meth) acrylate.

  The trifunctional or higher polyfunctional (meth) acrylate monomers include glycerin tri (meth) acrylate, trimethylolpropane tri (meth) acrylate, ditrimethylolpropane tri (meth) acrylate, ditrimethylolpropane tetra (meth) acrylate, pentaerythritol. Of tri- or higher functional aliphatic polyols such as tri (meth) acrylate, pentaerythritol tetra (meth) acrylate, dipentaerythritol tetra (meth) acrylate, dipentaerythritol penta (meth) acrylate, dipentaerythritol hexa (meth) acrylate, etc. Poly (meth) acrylate is typical, and other poly (meth) acrylates of tri- or higher functional halogen-substituted polyols, with alkylene oxide of glycerin Tri (meth) acrylate, trimethylolpropane alkylene oxide adduct tri (meth) acrylate, 1,1,1-tris [(meth) acryloyloxyethoxyethoxy] propane, tris (hydroxyethyl) isocyanurate tri ( And (meth) acrylates.

  On the other hand, (meth) acrylate oligomers include urethane (meth) acrylate oligomers, polyester (meth) acrylate oligomers, and epoxy (meth) acrylate oligomers.

  The urethane (meth) acrylate oligomer is a compound having a urethane bond (—NHCOO—) and at least two (meth) acryloyloxy groups in the molecule. Specifically, a urethanization reaction product of a hydroxyl group-containing (meth) acrylate monomer and a polyisocyanate each having at least one (meth) acryloyloxy group and at least one hydroxyl group in the molecule, and a polyol Urethane reaction product of terminal isocyanate group-containing urethane compound obtained by reaction with isocyanate and (meth) acrylate monomer each having at least one (meth) acryloyloxy group and at least one hydroxyl group in the molecule, etc. It can be.

  Examples of the hydroxyl group-containing (meth) acrylate monomer used in the urethanization reaction include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, and 2-hydroxy-3- Examples include phenoxypropyl (meth) acrylate, glycerin di (meth) acrylate, trimethylolpropane di (meth) acrylate, pentaerythritol tri (meth) acrylate, and dipentaerythritol penta (meth) acrylate.

  Examples of the polyisocyanate used for the urethanization reaction with the hydroxyl group-containing (meth) acrylate monomer include hexamethylene diisocyanate, lysine diisocyanate, isophorone diisocyanate, dicyclohexylmethane diisocyanate, tolylene diisocyanate, xylylene diisocyanate, and aromatic of these diisocyanates. Diisocyanates obtained by hydrogenating isocyanates (for example, hydrogenated tolylene diisocyanate, hydrogenated xylylene diisocyanate, etc.), di- or tri-isocyanates such as triphenylmethane triisocyanate, dibenzylbenzene triisocyanate, and Examples thereof include polyisocyanates obtained by multiplying the above diisocyanates.

  In addition, as polyols used to obtain terminal isocyanate group-containing urethane compounds by reaction with polyisocyanates, polyester polyols, polyether polyols, etc., as well as aromatic, aliphatic and alicyclic polyols should be used. Can do. Aliphatic and alicyclic polyols include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylol ethane, trimethylol propane, ditriol. Examples include methylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

  The polyester polyol is obtained by a dehydration condensation reaction between the above polyols and a polybasic carboxylic acid or an anhydride thereof. Examples of polybasic carboxylic acids or anhydrides thereof can be represented by adding “(anhydrous)” to those that may be anhydrides, and are represented by (anhydrous) succinic acid, adipic acid, (anhydrous) maleic acid, (anhydrous) Itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, hexahydro (anhydrous) phthalic acid, etc.

  The polyether polyol may be a polyoxyalkylene-modified polyol obtained by a reaction of the above-described polyols or dihydroxybenzenes with an alkylene oxide, in addition to the polyalkylene glycol.

  The polyester (meth) acrylate oligomer is a compound having an ester bond and at least two (meth) acryloyloxy groups in the molecule. Specifically, it can be obtained by a dehydration condensation reaction using (meth) acrylic acid, polybasic carboxylic acid or anhydride thereof, and polyol. Examples of polybasic carboxylic acids or anhydrides thereof used in the dehydration condensation reaction can be represented by adding “(anhydrous)” to those that can be anhydrides. (Anhydrous) succinic acid, adipic acid, (anhydrous) There are maleic acid, (anhydrous) itaconic acid, (anhydrous) trimellitic acid, (anhydrous) pyromellitic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, etc. Examples of the polyol used for the dehydration condensation reaction include 1,4-butanediol, 1,6-hexanediol, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, neopentyl glycol, trimethylolethane, trimethylolpropane, Examples include ditrimethylolpropane, pentaerythritol, dipentaerythritol, dimethylolheptane, dimethylolpropionic acid, dimethylolbutanoic acid, glycerin, and hydrogenated bisphenol A.

  The epoxy (meth) acrylate oligomer can be obtained by addition reaction of polyglycidyl ether and (meth) acrylic acid, and has at least two (meth) acryloyloxy groups in the molecule. Examples of the polyglycidyl ether used for the addition reaction include ethylene glycol diglycidyl ether, propylene glycol diglycidyl ether, tripropylene glycol diglycidyl ether, 1,6-hexanediol diglycidyl ether, and bisphenol A diglycidyl ether.

  When a (meth) acrylic compound is added to the curable adhesive, the amount is preferably 20% by weight or less, more preferably 10% by weight or less, based on the amount of the entire active energy ray-curable compound. When the amount of the (meth) acrylic compound is increased, the adhesion between the polarizing film and the protective film tends to be lowered.

  When the curable adhesive contains a radical polymerizable compound such as the (meth) acrylic compound as described above, a photo radical polymerization initiator is preferably added. Any radical photopolymerization initiator may be used as long as it can initiate polymerization of a radical polymerizable compound such as a (meth) acrylic compound by irradiation with active energy rays, and a conventionally known one can be used. Specific examples of the photoradical polymerization initiator include acetophenone, 3-methylacetophenone, benzyldimethyl ketal, 1- (4-isopropylphenyl) -2-hydroxy-2-methylpropan-1-one, 2-methyl-1 -[4- (methylthio) phenyl-2-morpholinopropan-1-one, acetophenone-based initiators such as 2-hydroxy-2-methyl-1-phenylpropan-1-one; benzophenone, 4-chlorobenzophenone, 4, Benzophenone initiators such as 4'-diaminobenzophenone; benzoin ether initiators such as benzoin propyl ether and benzoin ethyl ether; thioxanthone initiators such as 4-isopropylthioxanthone; other xanthone, fluorenone, camphorquinone, benzaldehyde Anthraquinone, and the like.

  The compounding quantity of radical photopolymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of radically polymerizable compounds, such as a (meth) acrylic-type compound, Preferably it is 1-6 weight part. When there is little quantity of radical photopolymerization initiator, hardening will become inadequate and it exists in the tendency for mechanical strength and the adhesiveness of a polarizing film and a protective film to fall. Moreover, when there is too much quantity of radical photopolymerization initiator, radical-polymerizability, such as an active energy ray hardening compound (a cation polymerizable curable compound containing an epoxy compound, and a (meth) acrylic compound) in a curable adhesive. The compound) is relatively reduced, and the durability performance of the resulting adhesive layer may be reduced.

  The curable adhesive can further contain a photosensitizer as necessary. By blending the photosensitizer, the reactivity of cationic polymerization and / or radical polymerization is increased, and the mechanical strength of the adhesive layer and the adhesiveness between the polarizing film and the protective film can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo and diazo compounds, halogen compounds, and photoreductive dyes. More specific examples of photosensitizers include benzoin derivatives such as benzoin methyl ether, benzoin isopropyl ether, and α, α-dimethoxy-α-phenylacetophenone; benzophenone, 2,4-dichlorobenzophenone, o- Benzophenone derivatives such as methyl benzoylbenzoate, 4,4'-bis (dimethylamino) benzophenone, and 4,4'-bis (diethylamino) benzophenone; thioxanthone derivatives such as 2-chlorothioxanthone and 2-isopropylthioxanthone; 2 -Anthraquinone derivatives such as chloroanthraquinone and 2-methylanthraquinone; Acridone derivatives such as N-methylacridone and N-butylacridone; Others, α, α-diethoxyacetophenone, benzyl, fluore Non-, xanthone, uranyl compounds, halogen compounds, etc. These photosensitizers may be used alone or in combination of two or more. The photosensitizer is preferably blended at a ratio of 0.1 to 20 parts by weight based on 100 parts by weight of the entire active energy ray-curable compound.

  The curable adhesive may be added with known polymer additives usually used for polymers. For example, primary antioxidants such as phenols and amines, sulfur secondary antioxidants, hindered amine light stabilizers (HALS), UV absorbers such as benzophenone, benzotriazole, or benzoate Is mentioned.

  Further, the curable adhesive may contain a solvent as necessary. The solvent is appropriately selected in consideration of the solubility of the components constituting the curable adhesive. Examples of common solvents include aliphatic hydrocarbons such as n-hexane and cyclohexane; aromatic hydrocarbons such as toluene and xylene; such as methanol, ethanol, propanol, isopropanol, and n-butanol. Alcohols; ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, and butyl acetate; cellosolves such as methyl cellosolve, ethyl cellosolve, and butyl cellosolve; Halogenated hydrocarbons such as methylene and chloroform. The mixing ratio of the solvent is appropriately determined from the viewpoint of adjusting the viscosity depending on the processing purpose such as film formability.

[Second protective film]
As described above, when a cycloolefin-based resin film is bonded to one surface of the polarizing film, a second protective film made of another thermoplastic resin may be bonded to the opposite surface of the polarizing film. it can. The second protective film made of a thermoplastic resin is also bonded to the polarizing film via an adhesive. The second protective film has been widely used as a protective film forming material in the art, such as cellulose acetate resin, polyolefin resin, acrylic resin, polyimide resin, polycarbonate resin, polyester resin, and the like. It can be composed of an appropriate material. Among these, it is preferable to use a cellulose acetate-based resin film as the second protective film from the viewpoint of mass productivity and adhesiveness. A cellulose acetate-based resin film is also preferably used as the second protective film from the viewpoint of ease of providing the surface treatment layer and optical properties.

  The cellulose acetate-based resin film is a film made of a cellulose portion or a complete acetate ester, and examples thereof include a triacetyl cellulose film and a diacetyl cellulose film. Examples of such cellulose acetate-based resin films include commercially available products such as “Fujitack TD80”, “Fujitack TD80UF” and “Fujitack TD80UZ” sold by Fuji Film Co., Ltd., Konica Minolta Opto Co., Ltd. Commercially available “KC8UX2M”, “KC8UY”, “KC4UEW”, etc. (all are trade names) can be used.

  The adhesive used for laminating the second protective film and the polarizing film is not particularly limited, and various kinds of adhesives previously mentioned as the adhesive used for laminating the polarizing film and the cycloolefin-based resin film are similarly used. However, it is preferable to use the same adhesive as that used for the cycloolefin-based resin film. In adhering these films using an adhesive, in order to improve the adhesiveness, the adhesive surface of the second protective film and / or the polarizing film bonded to the second protective film is used to improve the adhesiveness described above. A surface treatment may be applied as appropriate. When the second protective film is composed of a cellulose acetate-based resin film and is attached to a polarizing film using an aqueous adhesive, as one of the preferred surface treatments applied to the cellulose acetate-based resin film, a saponification treatment Can be mentioned. The saponification treatment is performed by immersing the film in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

  The second protective film is preferably thin, but if it is too thin, the strength tends to be low and the processability tends to be poor. On the other hand, if it is too thick, the transparency may be reduced or the weight of the polarizing plate may increase. There is a tendency. From this point of view, the thickness of the second protective film is usually 10 to 200 μm, preferably 20 to 150 μm, more preferably 30 to 100 μm, when it is composed of cellulose acetate resin.

In the second protective film, a surface treatment such as an antiglare treatment, a hard coat treatment, an antistatic treatment, and an antireflection treatment may be applied to the surface opposite to the surface to be attached to the polarizing film.

[Production method of polarizing plate]
Next, the manufacturing method of the polarizing plate which concerns on this invention is demonstrated. As described above, in the present invention, a polarizing plate is produced by bonding a protective film made of a cycloolefin-based resin to a polarizing film via an adhesive. If desired, a first protective film made of a cycloolefin resin is bonded to one side of the polarizing film as described above, and a second protective film made of another thermoplastic resin is also attached to the other side of the polarizing film. It can be bonded via an adhesive. And the protective film which consists of cycloolefin resin is an organic solvent which does not contain a solute substantially in the range whose haze value of the cycloolefin resin film does not exceed 0.5% prior to pasting to a polarizing film. Process in contact with. The treatment that is brought into contact with the organic solvent may be referred to as “solvent treatment” in the present specification.

  From one standpoint, the organic solvent used in the above solvent treatment is an organic that changes the cycloolefin resin when it is in contact with the cycloolefin resin constituting the first protective film described above. A solvent (hereinafter sometimes referred to as “good solvent”) and an organic solvent that does not substantially change the cycloolefin resin when contacted with the cycloolefin resin alone (hereinafter referred to as “poor solvent”). It is sometimes referred to as a “solvent”).

  Whether a certain organic solvent corresponds to a good solvent or a poor solvent for the cycloolefin-based resin film can be determined by the following test. First, a cycloolefin-based resin film serving as a protective film is cut, and about 1.0 g is taken and weighed accurately to the third decimal place in grams, and its mass is defined as Fg. In addition, about 99.0 g of organic solvent is also accurately weighed to the third decimal place in grams and the mass is taken as Sg. The resin film accurately weighed above is completely immersed in the organic solvent and left for 24 hours. After 24 hours, the resin film soaked is observed for changes in shape and appearance. In addition, about 10.0 g of the supernatant of the organic solvent in which the resin film has been immersed is taken, and accurately weighed to the third decimal place in grams, and the mass is Lg. From there, the organic solvent is removed by drying, and the remaining solid content is weighed, and its mass is defined as Rg. From these values, the dissolution amount of the resin film is determined. If the resin film is completely dissolved, it becomes a solution of [F (= about 1 g) / {F + S (= about 100 g)} × 100 wt%] (= about 1 wt%). Should remain [L (= about 10 g) × F (= about 1 g) / {F + S (= about 100 g)} g] (= about 0.1 g). Therefore, the solubility of the resin film is calculated from the following formula (III).

  Thus, if the resin film after being immersed in an organic solvent for 24 hours has not changed in shape or appearance and the solubility is less than 1% by weight, the organic solvent is regarded as a poor solvent. In other cases, that is, when the shape or appearance is changed or the solubility is 1% by weight or more, the organic solvent is a good solvent. Of course, even when the shape and appearance are changed and the solubility is 1% by weight or more, the organic solvent is a good solvent. According to the experiment, although the film was not dissolved, there were a state in which the shape and appearance of the film changed, and there were a state in which the film swelled and stopped its original shape, and a state in which the film was whitened.

  Samples of stretched cycloolefin-based resin films (trade name “ZEONOR FILM”, manufactured by Nippon Zeon Co., Ltd.) used in Examples described later are used as samples, and representative data are as follows. The results are summarized in Table 1. “%” Representing solubility in the table is based on weight as understood from the above description. In addition, when the column of “solubility” is “−”, it means that only the immersion experiment was performed and the appearance after immersion for 24 hours was observed, but the solubility was not measured. In any case, the solubility is estimated to be almost zero from the result of appearance observation after 24 hours.

  From these results and our previous experience, cycloaliphatic hydrocarbons such as cyclohexane, methylcyclohexane and ethylcyclohexane are classified as good solvents because the solubility of cycloolefin resins is close to 100%. Is done. In addition, aromatic hydrocarbons such as toluene and xylene, halogenated hydrocarbons such as dichloromethane and chloroform, aliphatic ethers such as diethyl ether and tetrahydrofuran, and aliphatics such as pentane, hexane and heptane Hydrocarbons include those with a cycloolefin resin solubility of 1% or more and those with a solubility of less than 1%, both of which change the shape and appearance, and are therefore classified as good solvents here. .

  On the other hand, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, aliphatic alcohols such as isopropanol and butanol, and aliphatic esters such as ethyl acetate, propyl acetate, isopropyl acetate and butyl acetate are cycloolefins. Since the solubility of the system resin is less than 1% and does not change the shape and appearance of the film, it is classified as a poor solvent.

  Among the organic solvents listed above, cycloaliphatic hydrocarbons that dissolve cycloolefin resins and are classified as good solvents can be used without being excessively eroded by cycloolefin resins. It was found to be effective in increasing the adhesion with the film. Therefore, from another standpoint in the present invention, the organic solvent used for the solvent treatment includes an alicyclic hydrocarbon. The alicyclic hydrocarbon can typically be a compound of formula (I) listed above. Also when using an alicyclic hydrocarbon, it is advantageous to use a mixed solvent containing a poor solvent in addition to the alicyclic hydrocarbon. The poor solvent mixed with the alicyclic hydrocarbon is preferably an alkyl ester of an organic acid, or an acetate ester as exemplified above.

  In the present invention, it is important to perform the solvent treatment so that the cycloolefin-based resin film is not excessively eroded, and the haze value of the cycloolefin-based resin film after the solvent treatment is adopted as an indicator that the cycloolefin-based resin film is not excessively eroded. If the erosion of the cycloolefin resin film surface proceeds, the adhesion to the polarizing film is improved, but the optical performance of the cycloolefin resin film is impaired. Therefore, the cycloolefin resin film after treatment is treated with a solvent so that the haze value does not exceed 0.5%. It is more preferable that the haze value at this time does not exceed 0.3%, and further does not exceed 0.2%. The haze value is defined in JIS K 7136: 2000 “Plastics—How to determine haze of transparent material”, and is a value defined by (diffuse transmittance / total light transmittance) × 100 (%).

  Moreover, when erosion progresses by solvent treatment, the retardation of the film is canceled and the in-plane retardation value tends to decrease. Therefore, when the in-plane retardation value is given by stretching the cycloolefin-based resin film, the amount of change in the in-plane retardation value of the cycloolefin-based resin film by the solvent treatment is not excessively eroded. It is also effective to use it as an indicator. Specifically, when the cycloolefin resin film has an in-plane retardation value of 30 nm or more before the solvent treatment, the in-plane retardation value after the solvent treatment is more than the in-plane retardation value before the solvent treatment. In other words, the amount of decrease in the in-plane retardation value after the solvent treatment relative to the in-plane retardation value before the solvent treatment (in-plane retardation value before the solvent treatment-after the solvent treatment) The solvent treatment is carried out so that the in-plane retardation value of the film becomes 3 nm or less. It is more preferable that the amount of decrease in the in-plane retardation value after the solvent treatment with respect to the in-plane retardation value before the solvent treatment is 2.5 nm or less, particularly 2 nm or less. When the amount of decrease is large, there is a possibility of affecting display characteristics when the obtained polarizing plate is applied to a liquid crystal display device. When the alicyclic hydrocarbon is used alone for the solvent treatment, the amount of decrease in the in-plane retardation value tends to be slightly increased. From this aspect, the poor solvent is mixed with the alicyclic hydrocarbon. Are preferably used.

Plane retardation value Re of the film, the refractive index n _y in the refractive index in the in-plane slow axis direction n _x of the film, in-plane fast axis direction (direction orthogonal with the slow axis and the plane) The thickness is a value defined by the following formula (IV), where d is a thickness, and can be measured using various commercially available phase difference meters.
_{Re = (n x -n y)} × d (IV)

  In the case of using a mixed organic solvent, the mixing ratio may be determined in consideration of the haze value and in-plane retardation value of the cycloolefin resin film after the solvent treatment.

  In the present invention, a polarizing plate can be produced through the following steps (i) to (iii). When the first protective film made of cycloolefin resin is bonded to one side of the polarizing film and the second protective film made of another thermoplastic resin is bonded to the other side of the polarizing film, The step (iv) is adopted.

(I) a solvent treatment step of treating the surface of the cycloolefin-based resin film with the organic solvent substantially free of solute described above,
(Ii) a drying step of drying the organic solvent;
(Iii) The 1st bonding process which bonds the cycloolefin type-resin film processed and dried with the organic solvent to a polarizing film through an adhesive so that the said processing surface may become a bonding surface,
(Iv) The 2nd bonding process of bonding the 2nd protective film which consists of a thermoplastic resin film to the surface on the opposite side to the surface where the cycloolefin type resin film of the said polarizing film was bonded. .

  In said solvent processing process (i), a cycloolefin type-resin film is made to contact the organic solvent demonstrated previously. Specifically, a method of applying the organic solvent to the surface of the cycloolefin resin film is preferably used. As a coating method used for this purpose, a known method such as a casting method, a Mayer bar coating method, a gravure coating method, a comma coating method, a doctor blade method, a die coating method, a dip coating method, or a spraying method can be adopted. The surface to be treated may be one side or both sides of the cycloolefin-based resin film, but the surface to be bonded to the polarizing film is subjected to this treatment.

  Next, in said drying process (ii), the organic solvent used for processing the surface of a cycloolefin type-resin film is dried. Natural drying may be used, but when drying is performed by heating, drying is preferably performed at a temperature not higher than the glass transition point of the cycloolefin-based resin film from the viewpoint of preventing deformation of the film. This drying step (ii) can also be performed in parallel with the solvent treatment step (i), and when performed in parallel, that is, when the cycloolefin resin film is treated with an organic solvent, It is preferable to simultaneously perform the operation of drying the solvent. Specifically, a method of applying an organic solvent while applying air to the application surface can be employed.

  In said 1st bonding process (iii), the cycloolefin type resin film processed with the organic solvent is bonded to a polarizing film through an adhesive agent so that the processing surface may become a bonding surface. The bonding method here may be generally known, for example, casting method, Meyer bar coating method, gravure coating method, comma coater method, doctor blade method, die coating method, dip coating method, spraying method The method of apply | coating an adhesive agent to the adhesive surface of a polarizing film and / or the cycloolefin type-resin film bonded by it, etc. by these etc. can be employ | adopted. Here, the casting method is a method of spreading and spreading the adhesive on the surface of the film to be coated while moving it in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two. . After applying the adhesive, the polarizing film and the cycloolefin-based resin film are sandwiched and bonded together by a nip roll or the like. In addition, when a method in which an adhesive is dropped between films and then pressed with a roll or the like and spreads uniformly is adopted, the material of the roll to be used can be a metal or rubber, and the gap between the two rolls. The rolls used for passing may be made of the same material or different materials.

  After pasting the cycloolefin resin film to the polarizing film via an adhesive, by using a water-based adhesive, by drying, or when using a curable adhesive, by irradiating active energy rays. The adhesive layer is cured. The drying process can be performed, for example, by blowing hot air. The temperature is usually in the range of 40 to 100 ° C, preferably in the range of 60 to 100 ° C. The drying time is usually 20 to 1,200 seconds. On the other hand, active energy rays used for active energy ray irradiation can be ultraviolet rays, electron beams, X-rays, visible rays, etc., but in general, ultraviolet rays are preferably used. The active energy ray may be irradiated with the intensity and amount necessary to cure the adhesive layer.

  When the second protective film made of another thermoplastic resin is bonded to the polarizing film surface opposite to the surface to which the cycloolefin-based resin film is bonded, the second bonding step (iv ) Is performed. In this step, the same method as in the first bonding step (iii) described above can be employed. It is preferable that a 2nd bonding process (iv) is performed simultaneously with said 1st bonding process (iii).

  The thickness of the adhesive layer obtained after drying or curing is usually about 0.01 to 5 μm, but can be 1 μm or less when an aqueous adhesive is used. On the other hand, even when a curable adhesive is used, the thickness is preferably 2 μm or less. If the adhesive layer is too thin, the adhesion may be insufficient. On the other hand, if the adhesive layer is too thick, the appearance of the polarizing plate may be poor.

[Polarizer]
The polarizing plate thus obtained has an enhanced adhesive force between the polarizing film and the cycloolefin-based resin film. That is, a protective film made of a cycloolefin resin is bonded to a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol resin through an adhesive, and the protective film made of the cycloolefin resin. Is bonded to the polarizing film through the adhesive in a state where the haze value does not exceed 0.5% and is treated with the organic solvent described above, and through the adhesive. A polarizing plate having an adhesive strength to the polarizing film of 0.5 N / 25 mm or more is obtained. Furthermore, a first protective film made of a cycloolefin resin is provided on one side of a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol resin, and a second film made of a thermoplastic resin on the other side of the polarizing film. The first protective film made of the cycloolefin-based resin is bonded to each other through an adhesive, and the above-described organic film has a haze value of not more than 0.5%. A polarizing plate which is bonded to the polarizing film through the adhesive in a state treated with a solvent and has an adhesive force to the polarizing film through the adhesive of 0.5 N / 25 mm or more is also obtained. In any polarizing plate, the adhesive force of the first protective film made of cycloolefin resin to the polarizing film through the adhesive is 0.7 N / 25 mm or more, and further 0.8 N / 25 mm or more. Even more preferred.

  Here, the adhesive force of the cycloolefin resin film to the polarizing film is a value measured as follows. That is, as explained so far, the first protective film made of cycloolefin resin is provided on one side of the polarizing film, and the other surface of the polarizing film is made of another thermoplastic resin. Each of the second protective films having a higher adhesive force to the polarizing film is bonded via an adhesive, and if necessary, the adhesive is dried or cured to produce a polarizing plate. An adhesive layer is provided on the cycloolefin resin film side. A test piece having a width of 25 mm and a length of about 200 mm was cut from the polarizing plate with the pressure-sensitive adhesive thus obtained, and the pressure-sensitive adhesive surface was bonded to a glass plate to sufficiently enhance the adhesive strength of the pressure-sensitive adhesive to the glass plate. Then, using a tensile tester, hold the second protective film at one end in the length direction (one side of 25 mm in width) and the polarizing film, and at a temperature of 23 ° C. and a relative humidity of 60%, crosshead speed (Grasping movement speed) At 90 mm / min, a 90 ° peel test in accordance with JIS K 6854-1: 1999 “Adhesive—Peeling adhesion strength test method—Part 1: 90 degree peeling” is performed. The average peel strength (unit: N / 25 mm) at this time is defined as the adhesive strength of the cycloolefin resin film to the polarizing film.

  If this adhesive strength is too small, the film peels off at the interface between the polarizing film and the cycloolefin resin film, and when the polarizing plate is pasted on the liquid crystal cell as described above, the rework needs to occur. Only the film may remain on the liquid crystal cell. On the other hand, the higher the adhesive strength, the better, but if you try to increase it, the processing (erosion) of the cycloolefin resin film with an organic solvent becomes excessive and the haze value of the cycloolefin resin film is increased. Will be damaged. Therefore, it is important to carry out solvent treatment while maintaining the optical properties including the haze value of the cycloolefin resin film to increase the adhesion of the cycloolefin resin film to the polarizing film.

  The polarizing plate obtained by this invention can provide an adhesive layer in the surface on the opposite side to the polarizing film of the cycloolefin type resin film bonded by the polarizing film. This pressure-sensitive adhesive layer can be used for bonding the polarizing plate to a liquid crystal cell, bonding to another functional film such as a retardation film, and bonding to another layer. As the pressure-sensitive adhesive, an acrylic polymer, a silicone polymer, polyester, polyurethane, polyether or the like as a base polymer can be used. Among them, like acrylic adhesives, it has excellent optical transparency, retains appropriate wettability and cohesion, has excellent adhesion, and has weather resistance, heat resistance, etc. It is preferable to select and use a material that does not cause peeling problems such as floating and peeling under humidification conditions. In acrylic adhesives, alkyl esters of (meth) acrylic acid having an alkyl group having 20 or less carbon atoms such as methyl, ethyl and butyl groups, and (meth) acrylic acid and hydroxyethyl (meth) acrylate An acrylic copolymer having a weight average molecular weight of 100,000 or more, in which a glass transition temperature is preferably 25 ° C. or less, more preferably 0 ° C. or less, and a functional group-containing acrylic monomer comprising Useful as a base polymer.

  The pressure-sensitive adhesive layer is formed, for example, by dissolving or dispersing the pressure-sensitive adhesive composition including the above-mentioned base polymer in an organic solvent such as toluene or ethyl acetate to prepare a 10 to 40% by weight solution, and protecting film It can be carried out by a method of forming a pressure-sensitive adhesive layer by forming a pressure-sensitive adhesive layer thereon and transferring it onto a polarizing plate. In addition to the base polymer described above, a crosslinking agent is generally added to the adhesive. Furthermore, when bonding to a liquid crystal cell is intended, it is also preferable to mix a silane coupling agent. The thickness of the pressure-sensitive adhesive layer is determined according to the adhesive force and the like, but is usually in the range of 1 to 50 μm.

  The pressure-sensitive adhesive may be blended with fillers made of glass fiber, glass beads, resin beads, inorganic powders such as metal powder, pigments, colorants, antioxidants, ultraviolet absorbers, and the like as necessary. . Examples of ultraviolet absorbers include salicylic acid ester compounds, benzophenone compounds, benzotriazole compounds, cyanoacrylate compounds, nickel complex compounds, and the like.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, parts and% indicating the amount used or content are based on weight unless otherwise specified. The in-plane retardation value and thickness direction retardation value of the film were measured by a rotating analyzer method using monochromatic light with a wavelength of 559 nm using a retardation measuring device “KOBRA-21ADH” manufactured by Oji Scientific Instruments. Value.

[Production Example 1] Production of polarizing film A polyvinyl alcohol film having an average polymerization degree of about 2,400 and a saponification degree of 99.9 mol% or more and a thickness of 75 µm was immersed in pure water at 30 ° C, and then iodine / iodination. Dyeing was carried out by immersing in an aqueous solution having a potassium / water weight ratio of 0.02 / 100 at 30 ° C. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 12/5/100 at 56.5 ° C. to perform boric acid treatment. Subsequently, after washing with pure water at 8 ° C., it was dried at 65 ° C. to obtain a polarizing film having a thickness of about 30 μm in which iodine was adsorbed and oriented on polyvinyl alcohol. Stretching was mainly performed in the iodine staining and boric acid treatment steps, and the total stretching ratio was 5.3 times.

[Production Example 2] Preparation of Adhesive Composition Acetoacetyl group-modified polyvinyl alcohol [trade name “Gosephimer Z-200”, manufactured by Nippon Synthetic Chemical Industry Co., Ltd., viscosity of 4% aqueous solution = 12.4 mPa · sec, The degree of saponification = 99.1 mol%] was dissolved in pure water to prepare a 10% strength aqueous solution. This aqueous solution of acetoacetyl group-modified polyvinyl alcohol and sodium glyoxylate as a cross-linking agent are mixed so that the weight ratio of the former: latter solids is 1: 0.1, and acetoacetyl is added to 100 parts of water. The adhesive composition was prepared by diluting with pure water so that the group-modified polyvinyl alcohol was 2.5 parts.

[Control example]
(A) Protective film A 25 μm thick stretched cycloolefin-based resin film [trade name “ZEONOR FILM”, manufactured by Nippon Zeon Co., Ltd., in-plane retardation value = 90 nm, thickness direction retardation value = 79 nm] It processed and it was set as one protective film. The haze value of this film was determined by using a haze transmittance meter according to JIS K 7361-1: 1997 “Plastics-Test method for total light transmittance of transparent materials-Part 1: Single beam method” [Murakami Color Technology Co., Ltd. The results are shown in Table 2. Table 2 shows the results. One side of a 40 μm thick cellulose acetate resin film [trade name “KC4UEW”, manufactured by Konica Minolta Opto Co., Ltd.] was subjected to corona treatment to obtain another protective film.

(B) Production of Polarizing Plate The adhesive composition prepared in Production Example 2 was applied to both surfaces of the polarizing film produced in Production Example 1 in an atmosphere at 23 ° C., and the above corona was applied to one adhesive application surface. The treated stretched cycloolefin-based resin film, the other adhesive-coated surface, the corona-treated cellulose acetate-based resin film, so that each corona-treated surface becomes a bonding surface with a polarizing film, Bonding was performed using a sticking apparatus [“LPA3301” manufactured by Fuji Plastics Co., Ltd.]. This was dried at 80 ° C. for 5 minutes to produce a polarizing plate.

(C) Evaluation of adhesive force After the corona treatment was performed on the surface of the cycloolefin resin film of the polarizing plate produced above, an acrylic pressure-sensitive adhesive sheet was bonded to the corona-treated surface. The obtained polarizing plate with pressure-sensitive adhesive was cut into a test piece having a width of 25 mm and a length of about 200 mm, and the pressure-sensitive adhesive surface was bonded to soda glass. Then, the pressure was 5 kgf / cm ^{2 at} a temperature of 50 ° C. in an autoclave. The pressurization process was performed for 1 minute, and the mixture was further left for 1 day in an atmosphere of a temperature of 23 ° C. and a relative humidity of 60%. In this state, using a universal tensile tester [“AG-1” manufactured by Shimadzu Corporation], grasp the cellulose acetate resin film and polarizing film at one end in the length direction (one side of 25 mm in width) of the test piece. , 90 ° peel test (JIS K 6854-1: 1999 “Adhesive-Peeling peel strength test method-No. 1) at an ambient temperature of 23 ° C. and a relative humidity of 60% at a crosshead speed of 200 mm / min. 1 part: 90 degree peeling ”), and the adhesive force between the cycloolefin-based resin film and the polarizing film was evaluated. The results are shown in Table 2.

[Example 1]
On one side of the stretched cycloolefin-based resin film used as one of the protective films in the above control example, using a coating machine [bar coater manufactured by Daiichi Rika Co., Ltd.], toluene: methyl ethyl ketone = 1: 9 (volume ratio) The organic solvent mixed in step 1) was applied. This coating was performed while applying air to the coated surface with a blower. The haze value of the treated cycloolefin-based resin film was measured by the method shown in the control example (A), and the results are shown in Table 2.

  Further, when the surface unevenness of the cycloolefin-based resin film after the solvent treatment was visually observed, it was not clearly visible, but when observed well, the unevenness could be confirmed. Similarly, the in-plane retardation value of the cycloolefin-based resin film after the solvent treatment is measured, and the change from the value before the treatment (90 nm) (when the retardation value is lower than that before the treatment is negative) As a result, the difference was -0.3 nm. Also in the following examples and comparative examples, for the cycloolefin-based resin film after solvent treatment, the haze value is measured, the surface unevenness is observed, and the in-plane retardation value is measured in the same manner as this example. In the "Haze value" column of Table 2, the surface unevenness is evaluated in the following three stages, and the result is shown in the "Unevenness" column of Table 2, and the change in in-plane retardation value from the film before processing is shown in Table 2. This is shown in the column of “Re change” in FIG.

(Evaluation criteria for surface unevenness of film after solvent treatment)
None: Unevenness cannot be confirmed at all.
Weak: Although it is not clearly visible, unevenness can be confirmed when observed closely (state of Example 1).
Strong: Unevenness can be confirmed clearly.

  The solvent-treated surface of the stretched cycloolefin-based resin film thus solvent-treated is subjected to corona treatment and then applied to one side of the polarizing film, and the other side of the polarizing film is subjected to the same corona-treated acetic acid as in the control example. A cellulose-based resin film was bonded, and the other was made in the same manner as in the control example to prepare a polarizing plate. The adhesive force between the cycloolefin-based resin film and the polarizing film of the obtained polarizing plate was evaluated by the same method as in Control Example (C), and the results are shown in Table 2.

[Example 2]
A polarizing plate was prepared and evaluated in the same manner as in Example 1 except that the mixed solvent was changed to toluene: methyl ethyl ketone = 2: 8 (volume ratio). Table 2 shows the haze value of the cycloolefin-based resin film after the solvent treatment, the observation results of the surface unevenness, the change in the in-plane retardation value, and the adhesive force between the cycloolefin-based resin film and the polarizing film of the polarizing plate. Summarized.

[Comparative Example 1]
A polarizing plate was prepared and evaluated in the same manner as in Example 1 except that the mixed solvent was changed to toluene: methyl ethyl ketone = 3: 7 (volume ratio). Table 2 shows the haze value of the cycloolefin-based resin film after the solvent treatment, the observation results of the surface unevenness, the change in the in-plane retardation value, and the adhesive force between the cycloolefin-based resin film and the polarizing film of the polarizing plate. Summarized.

[Example 3]
On one side of the same stretched cycloolefin-based resin film used as one protective film in Example 1, cyclohexane was applied using the same coating machine as in Example 1, and a solvent treatment was performed. Here, since cyclohexane had already evaporated and dried after the coating was completed, no air was blown with a blower. Table 2 summarizes the haze value of the cycloolefin-based resin film after the solvent treatment, the observation results of the surface unevenness, and the change in the in-plane retardation value. In addition, after applying the corona treatment to the solvent-treated surface of the stretched cycloolefin-based resin film treated with cyclohexane in this way, it was used for bonding to one side of the polarizing film, and a polarizing plate was produced in the same manner as in Example 1. . The adhesive force between the cycloolefin-based resin film and the polarizing film of the obtained polarizing plate was evaluated by the same method as in Example 1, and the results are shown in Table 2.

[Example 4]
On one side of the same stretched cycloolefin-based resin film used as one protective film in Example 1, methylcyclohexane was applied using the same coating machine as in Example 1, and a solvent treatment was performed. In this example, coating was performed while applying air to the coated surface with a blower. Table 2 summarizes the haze value of the cycloolefin-based resin film after the solvent treatment, the observation results of the surface unevenness, and the change in the in-plane retardation value. In addition, after applying the corona treatment to the solvent-treated surface of the stretched cycloolefin-based resin film thus treated with methylcyclohexane, it was used for bonding to one side of the polarizing film. Otherwise, a polarizing plate was produced in the same manner as in Example 1. did. The adhesive force between the cycloolefin-based resin film and the polarizing film of the obtained polarizing plate was evaluated by the same method as in Example 1, and the results are shown in Table 2.

[Example 5]
The experiment was carried out in the same manner as in Example 4 except that the organic solvent was changed to ethylcyclohexane, and the results are summarized in Table 2.

[Examples 6 to 13]
The organic solvent is a mixed solvent of methylcyclohexane or ethylcyclohexane which is a good solvent and ethyl acetate, isopropyl acetate or propyl acetate which is a poor solvent. The same experiment as in No. 4 was performed and the results are summarized in Table 2.

[Examples 14 and 15]
The organic solvent is a mixed solvent of heptane, which is a good solvent, and methyl ethyl ketone, which is a poor solvent, and the volume ratio of the two is as shown in Table 2. The other experiments are the same as in Example 4, and the results are summarized in Table 2. It was.

[Comparative Example 2]
The experiment was conducted in the same manner as in Example 4 except that the organic solvent was changed to heptane, and the results are summarized in Table 2.

  As shown in Table 2, in the control example using the cycloolefin resin film not subjected to the solvent treatment, the adhesive force between the polarizing film and the cycloolefin resin film is low. On the other hand, in Comparative Example 1 in which the ratio of toluene in the toluene / methyl ethyl ketone mixed solvent used for the solvent treatment was increased and the cycloolefin resin film was easily eroded, the adhesion between the polarizing film and the cycloolefin resin film was increased. The haze value of the cycloolefin-based resin film increases to 0.6%, and the optical properties when formed into a polarizing plate cannot be satisfied. On the other hand, in Examples 1 and 2 in which the proportion of toluene in the toluene / methyl ethyl ketone mixed solvent used for solvent treatment was 10% by volume or 20% by volume, the haze value of the cycloolefin resin film was as low as 0.1%. The adhesive force between the polarizing film and the cycloolefin-based resin film can be increased while maintaining the thickness.

  Similarly, in Examples 3 to 5 where cyclohexane, methylcyclohexane or ethylcyclohexane was used for the solvent treatment, while maintaining the haze value of the cycloolefin resin film at a low value of 0.1%, The adhesive force between the cycloolefin resin films can be increased. However, in these examples, particularly in Example 4 using methylcyclohexane for solvent treatment and Example 5 using ethylcyclohexane, the decrease in the in-plane retardation value of the cycloolefin-based resin film tends to be slightly increased by the solvent treatment. It is in. On the other hand, in Examples 6 to 13 in which these alicyclic hydrocarbons, which are good solvents, are mixed with acetate, which is a poor solvent, the decrease in the in-plane retardation value of the cycloolefin-based resin film is 3 nm or less. The adhesive force between the polarizing film and the cycloolefin-based resin film can be increased while suppressing the thickness of the film. In Examples 3 to 13 using alicyclic hydrocarbons, the occurrence of unevenness after the solvent treatment was suppressed as compared with Examples 1 and 2 using toluene, and the cycloolefin resin film was good. Adhesive strength to the polarizing film can be increased while maintaining a good appearance and visibility.

  In Comparative Example 2 where the solvent treatment was performed using heptane, which is a good solvent, the adhesive strength between the polarizing film and the cycloolefin resin film was increased, but the haze value of the cycloolefin resin film was increased to 0.5%, Further, since surface unevenness is also observed after the treatment, the optical properties when formed into a polarizing plate cannot be satisfied. On the other hand, in Examples 14 and 15 in which methyl ethyl ketone, which is a poor solvent, was mixed with heptane, the surface unevenness was improved, and an increase in the haze value of the cycloolefin resin film and a decrease in the in-plane retardation value were suppressed. In this state, the adhesive force between the polarizing film and the cycloolefin resin film can be increased.

Claims (8)

A polarizing film in which a dichroic dye is adsorbed and oriented to a polyvinyl alcohol-based resin, a protective film made of a cycloolefin-based resin is bonded via an adhesive, and a polarizing plate is produced,
By uniaxially stretching a film made of a cycloolefin resin, a protective film made of the cycloolefin resin is prepared,
The protective film made of the cycloolefin-based resin is contacted with an organic solvent containing alicyclic hydrocarbon and substantially free of solute, and treated so that the haze value of the protective film does not exceed 0.5%. Then, a manufacturing method of a polarizing plate to be bonded to the polarizing film through the adhesive,
The manufacturing method of the polarizing plate characterized by processing so that the adhesive force of the protective film which consists of said cycloolefin type resin with respect to the said polarizing film through the said adhesive agent may be set to 0.5 N / 25mm or more. A first protective film made of a cycloolefin resin is provided on one side of a polarizing film having a dichroic dye adsorbed and oriented on a polyvinyl alcohol resin, and a second protection made of a thermoplastic resin on the other side of the polarizing film. A method for producing a polarizing plate by laminating a film via an adhesive,
By uniaxially stretching a film made of a cycloolefin resin, a first protective film made of the cycloolefin resin is prepared,
The first protective film made of the cycloolefin-based resin is brought into contact with an organic solvent containing an alicyclic hydrocarbon and substantially free of a solute, and the haze value of the first protective film is 0.5%. It is a manufacturing method of a polarizing plate which is bonded to the polarizing film through the adhesive after being processed so as not to exceed.
The manufacturing method of the polarizing plate characterized by processing so that the adhesive force of the 1st protective film which consists of said cycloolefin type resin with respect to the said polarizing film through the said adhesive agent may be set to 0.5 N / 25mm or more. In addition to at least one selected from the group consisting of cyclohexane, methylcyclohexane and ethylcyclohexane, the organic solvent is subjected to a contact test in which a film sample made of the cycloolefin resin is immersed for 24 hours. not cause any change in the shape or appearance, and solubility at that time is less than 1 wt%, contacted by a mixed solvent containing further an organic solvent which does not have a substantial change in the cycloolefin resin according to claim 1 or 2. The production method according to 2 . The manufacturing method according to claim 3 , wherein the organic solvent that does not substantially change the cycloolefin-based resin is an alkyl ester of an organic acid. The production method according to claim 4 , wherein the alkyl ester of the organic acid is an acetate ester. Wherein when the protective film made of a cycloolefin resin is treated with the organic solvent, the production method according to any one of claims 1 to 5, performing an operation of drying the organic solvent simultaneously. The adhesive method according to any one of claims 1 to 6, which is a water-based adhesive. The manufacturing method according to claim 7 , wherein the adhesive contains a polyvinyl alcohol-based resin.