KR102157406B1 - Polarizing layered film and method for manufacturing polarizing plate - Google Patents

Abstract

In the present invention, a resin layer forming step of forming a polyvinyl alcohol-based resin layer on a base film to obtain a laminated film; A stretching step in which a laminated film is uniaxially stretched so that the thickness of the polyvinyl alcohol-based resin layer is 10 µm or less to obtain a stretched film; A dyeing step of immersing the stretched film in a dyeing solution containing a dichroic dye to dye a polyvinyl alcohol-based resin layer to obtain a laminated film having a dyed layer; And, it provides a method for producing a polarizing laminated film having a crosslinking step of crosslinking the polyvinyl alcohol-based resin layer by immersing the laminated film having the dyed layer in a crosslinking solution containing boric acid, and forming a polarizer layer. ; The crosslinking step is a first crosslinking step using an aqueous solution having a boric acid content of 1 to 20 parts by weight per 100 parts by weight of water, but an iodide content of less than 1 part by weight, and a second crosslinking step using an aqueous solution having an iodide content of 2 parts by weight or more. It is carried out by dividing into a crosslinking process.

Description

A manufacturing method of a polarizing laminated film and a polarizing plate TECHNICAL FIELD [POLARIZING LAYERED FILM AND METHOD FOR MANUFACTURING POLARIZING PLATE}

The present invention relates to a method for producing a polarizing laminated film and a method for producing a polarizing plate.

The polarizing plate is widely used as a polarization supply element in a display device such as a liquid crystal display device and as a polarization detection element. As such a polarizing plate, conventionally, a polarizing film made of a polyvinyl alcohol-based resin (polarizer layer) and a protective film made of triacetyl cellulose have been used. Recently, mobile devices such as notebook personal computers and mobile phones of liquid crystal display devices have been used. Depending on the development of equipment, etc., thinner and lighter weight is required.

Conventionally, after stretching a film made of a polyvinyl alcohol-based resin alone, or by performing dyeing treatment or crosslinking treatment while stretching, a polarizing film was produced, and a protective film or the like was laminated thereon to prepare a polarizing plate. It could only be thinned to the limit thickness of the film alone. For this reason, after forming a polyvinyl alcohol-based resin layer serving as a polarizer layer on the surface of the base film, the polyvinyl alcohol-based resin layer is dry-stretched for each base film, dyeing treatment and crosslinking treatment are performed, and polyvinyl alcohol-based water By using the formation layer as a polarizer layer, a method has been proposed in which the total thickness of the base film and the polarizer layer is reduced to the limit, and the thickness of the polarizer layer (polarizing film) is made thinner than before.

For example, Japanese Patent Laid-Open No. 2009-98653 (Patent Document 1) discloses a stretched laminate in which a laminate in which a substrate layer and a hydrophilic polymer layer are laminated is stretched, and at least a dichroic substance is adsorbed to the hydrophilic polymer layer. The invention related to a polarizing plate containing a stretched laminate is disclosed. As a specific crosslinking method after dyeing the hydrophilic polymer layer with a dichroic material, immersed in an aqueous solution at 10 to 60°C containing 1 to 10% by weight of a crosslinking agent using boric acid as a representative example and 0.05 to 15% by weight of iodide. How to do it is described.

However, since the polyvinyl alcohol-based resin layer after dry stretching has a high degree of crystallinity, boric acid crosslinking tends to be difficult to occur, and the crosslinking reaction does not sufficiently proceed at the crosslinking temperature described in Patent Document 1, and sufficient polarization performance There was a problem that it was difficult to obtain.

In addition, Japanese Patent No. 491205 (Patent Document 2) discloses a method for producing an optical film laminate in which a polarizing film made of a polyvinyl alcohol-based resin in which a dichroic substance is oriented is formed on an amorphous ester-based thermoplastic resin substrate of a continuous web. The invention according to is disclosed. As a specific crosslinking method after dyeing the polyvinyl alcohol-based resin layer with a dichroic material, a method of stretching while immersed in an aqueous solution at 65°C containing 4 parts by weight of boric acid and 5 parts by weight of potassium iodide based on 100 parts by weight of water However, after immersing in an aqueous solution at 40°C containing 3 parts by weight of boric acid and 3 parts by weight of potassium iodide based on 100 parts by weight of water, 4 parts by weight of boric acid and potassium iodide are added to 100 parts by weight of water in the same manner as the previous method. A method of stretching while immersed in an aqueous solution of 75° C. containing 5 parts by weight of sulfide is described.

However, in the crosslinking solution containing potassium iodide, boric acid crosslinking tends to be difficult to occur, and even in the crosslinking method disclosed in Patent Document 2, the crosslinking reaction does not sufficiently proceed, and there is a problem that it is difficult to obtain sufficient polarization performance.

Japanese Patent Publication No. 2009-98653 (paragraphs [0059], [0060]) Japanese Patent No. 4691205 (paragraphs [0099], [0100], [0106] to [0109])

In view of the above-described problem, the present invention aims at producing a polarizing laminated film and a polarizing plate that are thin and have high polarization performance.

According to the present invention, there is provided a resin layer forming step of forming a polyvinyl alcohol-based resin layer on at least one surface of a base film to obtain a laminated film; A stretching process in which the obtained laminated film is uniaxially stretched so that the thickness of the polyvinyl alcohol-based resin layer is 10 µm or less to obtain a stretched film; A dyeing step of immersing the obtained stretched film in a dyeing solution containing a dichroic dye to dye the above-described polyvinyl alcohol-based resin layer to obtain a laminated film having a dyed layer; And a crosslinking step of immersing the obtained laminated film having a dyed layer in a crosslinking solution containing boric acid to crosslink the dyed polyvinyl alcohol-based resin layer to form a polarizer layer; The above-described crosslinking step includes a first crosslinking step and a second crosslinking step in this order, and a laminated film having a dyed layer obtained in the above-described dyeing step is obtained. In the first crosslinking step, the content of boric acid per 100 parts by weight of water is It is 1 to 20 parts by weight, and is immersed in an aqueous solution having an iodide content of less than 1 part by weight at a temperature of 60° C. or higher, and in the second crosslinking step, the content of boric acid per 100 parts by weight of water is 1 to 20 parts by weight, and iodide There is provided a method for producing a polarizing laminated film which is immersed in an aqueous solution having a water content of 2 parts by weight or more at a temperature of 60°C or higher.

In this method, it is preferable that the said extending|stretching process is performed by uniaxially extending|stretching the said laminated film at a draw ratio more than 5 times.

In addition, according to the present invention, the step of manufacturing a polarizing laminated film by any one of the above methods, a protective film bonding step of bonding a protective film to a surface opposite to the base film of the obtained polarizing laminated film, and protection A method for producing a polarizing plate including a base film peeling step of peeling the aforementioned base film from the polarizing laminated film after film bonding is also provided.

The present invention relates to a laminated film having a dyed layer obtained in the dyeing process, the first containing 1 to 20 parts by weight of boric acid per 100 parts by weight of water, and immersing at a temperature of 60°C or higher in an aqueous solution containing less than 1 part by weight of iodide. After performing the crosslinking step, it is characterized in that the second crosslinking step is performed at a temperature of 60°C or higher in an aqueous solution containing 1 to 20 parts by weight of boric acid and 2 parts by weight or more of iodide per 100 parts by weight of water. Thereby, the polarization performance is high, and a thin polarizing laminated film and a polarizing plate can be efficiently produced.

1 is a flowchart showing an embodiment of a method for manufacturing a polarizing laminated film according to the present invention.
2 is a flowchart showing an embodiment of a method for manufacturing a polarizing plate according to the present invention.

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

[Method of manufacturing a polarizing laminated film]

1 is a flowchart showing an embodiment of a method for manufacturing a polarizing laminated film. As shown in Fig. 1, this manufacturing method is a resin layer forming step (S10) in which a laminated film is obtained by forming a polyvinyl alcohol-based resin layer on at least one side of a base film, and the obtained laminated film is prepared with polyvinyl alcohol. Stretching step (S20) of obtaining a stretched film by uniaxial stretching so that the thickness of the based resin layer is 10 μm or less, the obtained stretched film is immersed in a dyeing solution containing a dichroic dye to dye the polyvinyl alcohol based resin layer Then, the dyeing step (S30) of obtaining a laminated film having a dyed layer, and the obtained laminated film having a dyed layer are immersed in a crosslinking solution containing boric acid to crosslink the dyed polyvinyl alcohol-based resin layer, and a polarizer It includes a crosslinking step (S40) of forming a layer.

By such a manufacturing method, a polarizing laminated film provided with a polarizer layer having a thickness of 10 µm or less having sufficient polarization performance can be obtained on a base film. This polarizing laminated film can also be used as an intermediate product for transferring the polarizer layer to a protective film as described later, and when the base film has a function of a protective film, this polarizing laminated film is used as a polarizing plate as it is. You can also use it.

[Polarizing plate manufacturing method]

2 is a flowchart showing an embodiment of a method for manufacturing a polarizing plate. As shown in Fig. 2, this manufacturing method is a resin layer forming step (S10) in which a laminated film is obtained by forming a polyvinyl alcohol-based resin layer on at least one side of the base film, and the obtained laminated film is prepared with polyvinyl alcohol. Stretching step (S20) of obtaining a stretched film by uniaxial stretching so that the thickness of the based resin layer is 10 μm or less, the obtained stretched film is immersed in a dyeing solution containing a dichroic dye to dye the polyvinyl alcohol based resin layer Then, the dyeing step (S30) of obtaining a laminated film having a dyed layer, and the obtained laminated film having a dyed layer are immersed in a crosslinking solution containing boric acid to crosslink the dyed polyvinyl alcohol-based resin layer, and a polarizer layer After carrying out the crosslinking step (S40) to form a protective film bonding step (S50) of bonding a protective film to the surface opposite to the base film of the obtained polarizing laminated film, and after bonding the protective film, the substrate described above It is to perform the base film peeling process (S60) which peels a film from a polarizing laminated film.

By such a manufacturing method, a polarizing plate provided with a polarizer layer having a thickness of 10 μm or less having sufficient polarization performance on the protective film can be obtained. This polarizing plate can be used, for example, by bonding it to another optical film or a liquid crystal cell through a pressure-sensitive adhesive.

Hereinafter, each step of S10 to S60 in FIGS. 1 and 2 will be described in detail. In addition, in FIG. 1 and FIG. 2, each process of S10-S40 is common in two drawings.

[Resin layer formation process (S10)]

In the resin layer forming step, a polyvinyl alcohol-based resin layer is formed on at least one surface of the base film to obtain a laminated film.

(Base film)

As the resin used for the base film, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, etc. may be mentioned, and an appropriate resin may be selected according to the glass transition temperature (Tg) or melting point (Tm). Specific examples of the thermoplastic resin include polyolefin resins such as chain polyolefin resins and cyclic polyolefin resins, polyester resins, (meth)acrylic resins, cellulose ester resins, polycarbonate resins, polyvinyl alcohol resins, Vinyl acetate resins, polyarylate resins, polystyrene resins, polyethersulfone resins, polysulfone resins, polyamide resins, polyimide resins, and mixtures and copolymers thereof. The base film may be a single layer or a multilayer composed of the above-described resin.

As the chain polyolefin-based resin, polyethylene, polypropylene, and the like are preferable since it can be stably stretched at a high magnification. Further, a propylene-ethylene copolymer obtained by copolymerizing ethylene with propylene can also be suitably used. Other types of monomers may be used for copolymerization, and examples of monomers other than ethylene that can be copolymerized with propylene include α-olefins. The α-olefin is one having 4 or more carbon atoms, and an α-olefin having 4 to 10 carbon atoms is preferable. Specific examples of the α-olefin having 4 to 10 carbon atoms include linear monoolefins such as 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene, and 1-decene; Branched monoolefins such as 3-methyl-1-butene, 3-methyl-1-pentene, and 4-methyl-1-pentene; Vinylcyclohexane and the like. The copolymer of propylene and another monomer copolymerizable thereto may be a random copolymer or a block copolymer. The content rate of the structural units derived from the other monomers in the copolymer is measured by infrared (IR) spectrum according to the method described on page 616 of the 「Polymer Analysis Handbook」 (1995, published by Kinokuniyashoten). It can be obtained by doing.

Among these, as the propylene resin constituting the propylene resin film, a homopolymer of propylene, a propylene-ethylene random copolymer, a propylene-1-butene random copolymer, and a propylene-ethylene-1-butene random copolymer are preferable. Do.

Further, it is preferable that the stereoregularity of the propylene-based resin constituting the propylene-based resin film is substantially isotactic or syndiotactic. A film made of a propylene resin having substantially isotactic or syndiotactic stereoregularity has relatively good handling properties and excellent mechanical strength in a high temperature environment.

As the cyclic polyolefin resin, a norbornene resin is preferably used. Cyclic polyolefin resin is a generic term for a resin in which a cyclic olefin is polymerized as a polymerization unit, for example, Japanese Patent Laid-Open No. Hei 1-240517, Japanese Patent Laid-Open No. Hei 3-14882, Japanese Patent Laid-Open No. Hei 3-122137, etc. The resins described can be mentioned. For example, a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, a copolymer of a cyclic olefin and an α-olefin such as ethylene or propylene (typically a random copolymer), and these are unsaturated carboxylic acids or Graft polymers modified with their derivatives, and hydrides thereof. As a specific example of a cyclic olefin, a norbornene-type monomer is mentioned.

Various products are commercially available as cyclic polyolefin resins. Specific examples of commercially available products include TOPAS (manufactured by Topas Advanced Polymers, available from Polyplastics Co., Ltd. in Japan), Aton (manufactured by JSR Corporation), and ZEONOR (Nippon Xeon Corporation). Manufacturing], ZEONEX (manufactured by Nippon Xeon Corporation), and Arpels (manufactured by Mitsui Chemical Corporation).

The polyester resin is a polymer having an ester bond in the main chain, and specifically, it is often composed of a polycondensate of a polyhydric carboxylic acid and a polyhydric alcohol. Polyhydric carboxylic acids used in the production of polyester resins are mainly divalent dicarboxylic acids or esters thereof, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylic acid. Further, polyhydric alcohols are also mainly dihydric diols, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

As a representative example of a polyester resin, polyethylene terephthalate, which is a polycondensation of terephthalic acid and ethylene glycol, is mentioned. Polyethylene terephthalate is a crystalline resin, but the one in the state before the crystallization treatment is easier to perform treatment such as stretching. If necessary, crystallization treatment can be performed by heat treatment or the like at the time of stretching or after stretching. Further, a copolymer polyester having reduced crystallinity (or made amorphous) by copolymerizing a monomer of another species to the skeleton of polyethylene terephthalate is also suitably used. Examples of such resins include those obtained by copolymerization of cyclohexanedimethanol or isophthalic acid. Since these resins are also excellent in stretchability, they can be suitably used.

Examples of specific polyester resins other than polyethylene terephthalate and its copolymer include polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, Polycyclohexanedimethylnaphthalate, etc. are mentioned. These blend resins and copolymers can also be used.

The (meth)acrylic resin is a polymer having a compound having a (meth)acryloyl group as a main constituent monomer. Specific examples include poly(meth)acrylic acid ester such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth)acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (Meth)acrylic acid copolymer, methyl methacrylate-styrene copolymer (such as those called MS resins), copolymers of methyl methacrylate and compounds having alicyclic hydrocarbon groups (e.g., methyl methacrylate-methacrylic acid Cyclohexyl copolymer, methyl methacrylate-(meth)acrylate norbornyl copolymer, etc.) are mentioned. Preferably, a polymer containing, as a main component, a C _1-6 alkyl ester of (meth)acrylic acid, such as poly(meth)acrylate, is used. As a more preferable example of a (meth)acrylic resin, a methyl methacrylate resin containing methyl methacrylate as a main component (50-100 weight%, Preferably 70-100 weight%) is mentioned.

The cellulose ester resin is a fatty acid ester of cellulose. Thus, as a specific example of a cellulose ester-type resin, a cellulose triacetate, a cellulose diacetate, a cellulose tripropionate, a cellulose dipropionate, etc. are mentioned. In addition, these copolymers and those in which some of the hydroxyl groups are modified with other groups are also mentioned. Among these, cellulose triacetate is particularly preferred. Many products are commercially available for cellulose triacetate film, and it is advantageous also in terms of availability and cost. Examples of commercially available products of cellulose triacetate film include: Fuji-Tak TD80, Fuji-Tak TD80UF, Fuji-Tak TD80UZ, Fuji-Tak TD40UZ (above, manufactured by Fujifilm Co., Ltd.), KC8UX2M, KC4UY (above, Konica Minolta Advanced Layer ( Note) Manufacturing).

Polycarbonate resin is a polymer having a carbonate bond (-O-CO-O-) in the main chain. It is a kind of engineering plastic, and is a resin with high impact resistance, heat resistance, and flame retardancy. In addition, since it has high transparency, it is suitably used for optical applications. In optical applications, resins called modified polycarbonates having modified polymer skeletons in order to lower the photoelastic coefficient, and copolymerized polycarbonates with improved wavelength dependence are also commercially available, and can be suitably used. Such polycarbonate resins are widely commercially available, for example, Panlite [manufactured by Teijin Kasei Co., Ltd.], Upiron [manufactured by Mitsubishi Engineering Plastics Co., Ltd.], SD Polycar [manufactured by Sumitomo Dow Corporation], Caliba [Manufactured by Dow Chemical Corporation] and the like.

Any suitable additive may be added to the above-described thermoplastic resin constituting the base film. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, releasing agents, coloring inhibitors, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. The proportion of the thermoplastic resin exemplified above in the base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, particularly preferably 70 to 97% by weight. %to be. This is because, when the proportion of the thermoplastic resin in the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently expressed.

The thickness of the base film can be appropriately determined, but in general, from the viewpoint of workability such as strength and handling properties, it is preferably 1 to 500 µm, and more preferably 1 to 300 µm, particularly 5 to 200 µm. Do. Further, a base film having a thickness in the range of 5 to 150 μm is still more preferable.

The base film may be subjected to corona treatment, plasma treatment, flame treatment, or the like at least on the surface on which the resin layer is formed in order to improve the adhesion to the resin layer. Further, in order to improve adhesion, a thin layer such as a primer layer or an adhesive layer may be formed on the surface of the base film on which the resin layer is formed. On the other hand, when an adhesive layer, a corona treatment layer, etc. are formed, it means that the base film is in a state which does not contain these.

(Polyvinyl alcohol resin layer)

In the polyvinyl alcohol-based resin layer, a polyvinyl alcohol-based resin powder is typically dissolved in a solvent having a high solubility such as water to prepare a polyvinyl alcohol-based resin solution, and the obtained resin solution is used at least one of the base film. It is formed by coating it on the surface of and drying by evaporating the solvent. By forming the resin layer in this way, it becomes possible to form a thin film. Coating of a polyvinyl alcohol-based resin solution onto the base film is a wire bar coating method, a roll coating method such as reverse coating or gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen coating method, It may be appropriately selected from various known methods such as fountain coating method, dipping method and spray method. The drying temperature is, for example, 50 to 200°C, preferably 60 to 150°C. The drying time is, for example, 2 to 20 minutes.

It is preferable that the thickness of the resin layer to be formed exceeds 3 µm and is 30 µm or less, and more preferably in the range of 5 to 20 µm. If the thickness of the resin layer obtained by coating is 3 μm or less, it becomes too thin after stretching, making it difficult to maintain sufficient dyeing properties. On the other hand, if the thickness exceeds 30 μm, the thickness of the finally obtained polarizer layer may exceed 10 μm. have.

In order to improve the adhesion between the base film and the polyvinyl alcohol-based resin layer, a primer layer may be formed on the surface of the base film on which the resin layer is formed. It is preferable from the viewpoint of adhesion that the primer layer is formed of a composition containing a polyvinyl alcohol-based resin and a crosslinking agent or the like.

When the resin layer is formed and the primer layer is formed, the polyvinyl alcohol-based resin used as the primer layer may be a polyvinyl acetate-based resin saponified. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and a copolymer of vinyl acetate and other monomers copolymerizable therewith. Other monomers copolymerizable with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

It is preferable that the polyvinyl alcohol-based resin used for formation of the resin layer has a degree of saponification of 80 mol% or more, further 90 mol% or more, particularly 94 mol% or more. If the degree of saponification is too low, there is a possibility that water resistance and moist heat resistance after setting as a polarizing plate may not be sufficient. In addition, a completely saponified product (one with a degree of saponification of 100 mol%) may be used, but if the degree of saponification is too high, the dyeing speed will be slow. In order to provide sufficient polarization performance, the manufacturing time may be lengthened, or in some cases, sufficient polarization performance will be provided. There are cases in which it is not possible to obtain a polarizer to have. Therefore, the degree of saponification is preferably 99.5 mol% or less, 99 mol% or less, or 99.0 mol% or less.

The saponification degree referred to herein is the ratio of the acetic acid group (acetoxy group: -OCOCH ₃ ) contained in the polyvinyl acetate resin, which is a raw material of the polyvinyl alcohol-based resin, to a hydroxyl group by saponification treatment, expressed as a unit ratio (mol%). It is defined by the following equation.

Saponification degree (mol%) = [(number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups)] × 100

The higher the degree of saponification, the greater the proportion of hydroxyl groups, and thus less the proportion of acetic acid groups that inhibit crystallization. The degree of saponification can be determined by a method prescribed in JIS K 6726-1994 "Test method for polyvinyl alcohol".

Further, the polyvinyl alcohol-based resin used in the present invention may be a modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol-based resins modified with olefins such as ethylene or propylene, modified with unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, modified with alkyl esters of unsaturated carboxylic acids And those modified with acrylamide. It is preferable that it is less than 30 mol%, and, as for the ratio of denaturation, it is more preferable that it is less than 10 mol%. In the case of modification of 30 mol% or more, it becomes difficult to adsorb the dichroic dye, which tends to cause a problem of lowering the polarization performance.

The average degree of polymerization of the polyvinyl alcohol-based resin is usually in the range of about 100 to 10,000, preferably 1,500 to 8,000, more preferably 2,000 to 5,000. The average degree of polymerization referred to herein can also be determined by the method prescribed in JIS K 6726-1994 "Polyvinyl Alcohol Test Method".

As a polyvinyl alcohol-based resin having such properties, for example, Kuraray Co., Ltd. PVA124 (soapability 98.0 to 99.1 mol%), PVA117 (soapability 98.0 to 99.0 mol%), PVA624 (soapability 95.0 to 96.0 mol%) ) And PVA617 (soapability 94.5-95.5 mol%); For example, AH-26 (saponification degree 97.0~98.8 mol%), AH-22 (saponification degree 97.5~98.5 mol%), NH-18 (saponification degree 98.0~99.0 mol%) manufactured by Nippon Kosei Chemical Industry Co., Ltd. N-300 (soapability 98.0-99.0 mol%); For example, JC-33 (saponification degree 99.0 mol% or more), JM-33 (saponification degree 93.5-95.5 mol%), JM-26 (saponification degree 95.5-97.5 mol%) manufactured by Nihon Sakubi Poval Co., Ltd., JP- 45 (saponification degree 86.5-89.5 mol%), JF-17 (saponification degree 98.0~99.0 mol%), JF-17L (saponification degree 98.0~99.0 mol%) and JF-20 (saponification degree 98.0~99.0 mol%), etc. These can be mentioned, and these can be used suitably in this invention.

[Stretching process (S20)]

In the stretching step, the laminated film is uniaxially stretched so that the thickness of the polyvinyl alcohol-based resin layer is 10 µm or less to produce a stretched film. The draw ratio of uniaxial stretching is preferably more than 5 times and not more than 17 times, more preferably more than 5 times and less than 8 times. If the draw ratio is 5 times or less, the orientation of the polyvinyl alcohol-based resin layer is insufficient, and as a result, there is a case where a problem that the polarization degree of the polarizer layer is not sufficiently increased. On the other hand, when the draw ratio exceeds 17 times, breakage of the laminated film is liable to occur at the time of stretching, and the stretched film becomes thinner than necessary, and there is a concern that workability and handling properties in a subsequent step are deteriorated. The stretching treatment in the stretching step (S20) is not limited to stretching in one step, and stretching may be performed in multiple steps. In this case, the stretching step after the second step may also be performed during the stretching step (S20), but may be performed simultaneously with the dyeing treatment or crosslinking treatment in the dyeing step (S30). In the case of performing stretching in multiple stages in this manner, it is preferable to perform the stretching treatment so that the integrated stretching ratio in which all the steps of the stretching treatment are combined is more than 5 times.

The stretching step (S20) in this embodiment can be performed by a longitudinal stretching treatment performed in the longitudinal direction of the laminated film, a transverse stretching treatment performed in the width direction, or the like. Examples of the vertical stretching method include an inter-roll stretching method and a compression stretching method, and examples of the horizontal stretching method include a tenter method.

In addition, although both a wet stretching method and a dry stretching method can be adopted for the stretching treatment, the dry stretching method is preferably used in that the temperature for stretching the laminated film can be selected in a wide range.

The stretching temperature is set to a temperature above the temperature at which the polyvinyl alcohol-based resin layer and the entire base film can be stretched and exhibits fluidity, and preferably, at the [phase transition temperature of the base film -30]°C, the [phase transition temperature of the base film +30] ] DegreeC, more preferably, it is a range of [phase transition temperature of a base film -25] degreeC to [phase transition temperature of a base film +30] degreeC. When the stretching temperature is lower than the [phase transition temperature of the base film -30]°C, it is difficult to achieve high-magnification stretching of more than 5 times. When the stretching temperature exceeds the [phase transition temperature of the base film +30]° C., the fluidity of the base film tends to be too large and stretching becomes difficult. Since it is easier to achieve a high draw ratio of more than 5 times, the draw temperature is within the above range, more preferably 120°C or higher. The temperature adjustment of the stretching treatment usually follows the temperature adjustment of the heating furnace.

[Dyeing process (S30)]

In the dyeing step, the stretched film obtained in the above stretching step is immersed in a dyeing solution containing a dichroic dye, and the polyvinyl alcohol-based resin layer in the stretched film is dyed, and a laminated film having a dyed layer is obtained. As the dichroic dye, for example, iodine or a dichroic organic dye can be used. As dichroic organic dyes, for example, Red BR, Red LR, Red R, Pink LB, Rubin BL, Bordeaux GS, Sky Blue LG, Lemon Yellow, Blue BR, Blue 2R, Navy RY, Green LG, Violet LB, Violet B , Black H, Black B, Black GSP, Yellow 3G, Yellow R, Orange LR, Orange 3R, Scarlet GL, Scarlet KGL, Congo Red, Brilliant Violet BK, Supra Blue G, Supra Blue GL, Supra Orange GL, Direct Sky Blue , Direct First Orange S, First Black, etc. can be used. These dichroic organic dyes can be obtained from the market. Only one type of dichroic dye may be used, or two or more types may be used in combination.

The dyeing step is performed, for example, by immersing the entire stretched film in a solution (dyeing solution) containing the dichroic dye. As the dyeing solution, a solution in which the dichroic dye is dissolved in a solvent can be used. As the solvent of the dyeing solution, water is generally used, but an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably 0.01 to 10% by weight, further preferably 0.02 to 7% by weight, particularly preferably 0.025 to 5% by weight.

When iodine is used as a dichroic dye, since dyeing efficiency can be further improved, it is preferable to further add iodide. Examples of this iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, and the like. It is preferable that the addition ratio of these iodide is 0.01-20 weight% in a dyeing solution. Among iodides, it is preferable to use potassium iodide. In the case of using potassium iodide, the ratio of iodine and potassium iodide is preferably in the range of 1:5 to 1:100 by weight ratio, furthermore in the range of 1:6 to 1:80, in particular 1:7 to 1:70 It is preferably in the range of.

The time for immersing the stretched film in the dyeing solution is usually preferably in the range of 15 seconds to 15 minutes, and more preferably in the range of 30 seconds to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 to 60°C, and more preferably in the range of 20 to 40°C.

On the other hand, it is also possible to perform the dyeing treatment before the stretching step or at the same time as the stretching step, but in order to properly orient the dichroic dye adsorbed on the polyvinyl alcohol-based resin, it is preferable to perform the dyeing treatment after the stretching treatment is performed on the unstretched film. . At this time, what has been stretched in advance at the target magnification may be simply dyed, or the thing stretched in advance at a low magnification may be stretched again during dyeing to reach the target magnification in total. In addition, when extending|stretching is further performed during the subsequent crosslinking process, it can also be made to stop extending|stretching with a low magnification here. In this case, after the crosslinking treatment, it may be appropriately adjusted so that the desired magnification is reached.

[Cross-linking process (S40)]

Following the dyeing process, a crosslinking process is performed. In the crosslinking step, a crosslinking treatment is performed by immersing the laminated film having a dyed layer obtained in the above dyeing step in a solution containing a crosslinking agent (crosslinking solution). As the crosslinking agent, boron compounds such as boric acid or borax, glyoxal, glutalaldehyde, and the like are generally known, but boric acid is used in the present invention. Of course, the presence of other crosslinking agents together with boric acid is acceptable.

In addition to boric acid, iodide is generally blended in the crosslinking solution. By the presence of iodide, the polarization characteristics in the plane of the resin layer can be made more uniform. As the iodide, for example, potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, titanium iodide, etc. are used, and potassium iodide is particularly preferred. Is used.

In the crosslinking step, better polarization performance can be obtained by using a plurality of crosslinking solutions having different types and concentrations of solutes. In the present invention, the crosslinking process is divided into two steps, and in the first step (the first crosslinking step), a crosslinking solution having a low iodide concentration or substantially not containing iodide is used, and the second step In the (2nd crosslinking step), a crosslinking solution having a higher iodide concentration than the first crosslinking step is used. Of course, the crosslinking step may be divided into three or more steps, but also in that case, the first crosslinking step is performed first, and then the second crosslinking step is performed. That is, the first crosslinking step and the second crosslinking step are performed in this order.

In the first crosslinking step, an aqueous solution having a boric acid content of 1 to 20 parts by weight per 100 parts by weight of water and an iodide content of less than 1 part by weight is used as a crosslinking solution, and there is a dyed layer obtained in the preceding dyeing step. The laminated film is immersed at a temperature of 60°C or higher. In this first crosslinking step, since the content of the iodide per 100 parts by weight of water is less than 1 part by weight, the crosslinking reaction can be promoted efficiently. As described above, in order to efficiently advance the crosslinking reaction in the first crosslinking step, the content of iodide in the crosslinking solution used therein is less than 1 part by weight per 100 parts by weight of water, but is preferably 0.6 parts by weight or less, more preferably It is 0.05 parts by weight or less. The crosslinking solution used in the first crosslinking step may not contain iodide.

Next, in the second crosslinking step, an aqueous solution containing 1 to 20 parts by weight of boric acid and 2 parts by weight or more of iodide per 100 parts by weight of water is used as a crosslinking solution, and thereafter, after passing through the first crosslinking step, The laminated film having a dyed layer is immersed at a temperature of 60°C or higher. In this second crosslinking step, since the content of iodide per 100 parts by weight of water is set to 2 parts by weight or more, different colors with poor orientation tend to remain in the polyvinyl alcohol-based resin layer (dye layer) in the preceding dyeing step and the first crosslinking step. The sex pigment becomes easier to remove. As a result, since the transmittance increases while securing polarization performance, better polarization performance can be obtained. Further, by adjusting the iodide content in the second crosslinking step, the hue of the polarizing laminated film can be adjusted. The content of iodide in the second crosslinking step is allowed up to about 15 parts by weight per 100 parts by weight of water, but is preferably 5 parts by weight or more, and preferably 8 parts by weight or less.

As the crosslinking solution, a solution obtained by dissolving a crosslinking agent (boric acid) in a solvent can be used. Although water is used in the present invention as a solvent, this crosslinking solution (aqueous solution) may further contain an organic solvent compatible with water. The concentration of boric acid in the crosslinking solution is 1 to 20 parts by weight per 100 parts by weight of water in both the first crosslinking step and the second crosslinking step, but is preferably 3 parts by weight or more, more preferably 4 parts by weight or more, even more preferably It is preferably 6 parts by weight or more, and preferably 15 parts by weight or less.

The time to immerse the laminated film having the dyed layer in the crosslinking solution is the sum of the entire crosslinking step including the first crosslinking step and the second crosslinking step, and is usually preferably 15 seconds to 20 minutes, and furthermore 30 seconds or more. Also, it is more preferable to make it 15 minutes or less. Although the temperature of the crosslinking solution is 60°C or higher, the upper limit is preferably 82°C or lower. If the temperature is less than 60°C, it becomes difficult to obtain sufficient polarization performance even if the immersion time is prolonged to some extent. On the other hand, when the temperature exceeds 82°C, the polyvinyl alcohol-based resin is partially eluted and uneven dyeing is likely to occur.

In addition, the crosslinking treatment can also be performed simultaneously with the dyeing treatment by mixing a crosslinking agent in the dyeing solution. In the present invention, a crosslinking agent may be mixed in the dyeing solution and partially undergo a crosslinking reaction in the dyeing step, but even in that case, crosslinking including the first crosslinking step and the second crosslinking step described above after the dyeing step By performing the process, it is made possible to obtain a polarizing laminated film or a polarizing plate exhibiting excellent polarization performance. Further, what has been stretched in advance at a target magnification may be simply crosslinked, or crosslinking treatment and stretching may be performed simultaneously. In this case, the stretched film previously stretched at a low magnification in the stretching step may be stretched again during the crosslinking treatment to reach the target magnification in total.

[Process performed arbitrarily after the crosslinking process]

After passing through the crosslinking process, it is preferable to perform washing treatment and drying treatment. Washing treatment is usually performed by washing the film which has passed through the crosslinking process with water. Pure water such as ion-exchanged water or distilled water is usually used for the washing treatment. Washing treatment can be performed by immersing the film after passing through a crosslinking process there. The temperature of water used for washing is usually 3 to 50°C, preferably in the range of 4 to 20°C. The immersion time is usually 2 to 300 seconds, preferably 3 to 240 seconds.

In the washing treatment, washing with an aqueous iodide solution and washing with water may be combined. Further, as appropriate, an aqueous solution containing liquid alcohol such as methanol, ethanol, isopropanol, propanol, and butanol may be used.

After washing treatment, it is preferable to further perform drying treatment. As the drying treatment, any suitable method (eg, natural drying, air drying, heat drying) may be employed. For example, in the case of heat drying, the drying temperature is usually 20 to 95°C, and the drying time is usually about 1 to 15 minutes. By the above dyeing process (S30) and crosslinking process (S40), the resin layer has a function as a polarizer. In this specification, a resin layer having a function as a polarizer is referred to as a polarizer layer, and a laminate provided with a polarizer layer on a base film is referred to as a polarizing laminated film.

[Protective film bonding process (S50)]

Here, the protective film is bonded to the surface of the polarizer layer opposite to the base film side of the polarizing laminated film obtained through each step described above. The bonding of the polarizer layer and the protective film can be performed by, for example, a method of bonding both through an adhesive layer or an adhesive layer.

(Protective film)

The protective film may be a simple protective film that does not have an optical function, or may be a film having an optical function such as a retardation film or a brightness improving film.

The material of the protective film can be used without particular limitation, which is generally used in the field of a polarizing plate. For example, a cyclic polyolefin resin film, a cellulose ester resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, a polyester resin film made of a resin such as polyethylene terephthalate, polyethylene naphthalate, or polybutylene terephthalate, And polycarbonate resin films, acrylic resin films, and polypropylene resin films.

Cyclic polyolefin resin is a cyclic olefin such as norbornene as its main constituent monomer, and suitable commercially available products, such as TOPAS [manufactured by Topas Advanced Polymers, available from Polyplastics Co., Ltd. in Japan], Aton [ JSR Co., Ltd.], ZEONOR (Nippon Xeon Co., Ltd.), Zeonex (Nippon Xeon Co., Ltd.), and Arpel (Mitsui Chemical Co., Ltd.), etc. are suitably used. I can. When forming a film by forming such a cyclic polyolefin resin into a film, known methods such as a solvent casting method and a melt extrusion method are suitably used.

The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary phase difference value can be provided to the cyclic polyolefin resin film. Stretching is usually carried out continuously while unwinding the film roll, and in a heating furnace, it is stretched in a direction of advancing of the roll, a direction orthogonal to the advancing direction, and both, or in an oblique direction that is neither parallel nor orthogonal to the advancing direction. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature +100°C. The draw ratio is usually 1.1 to 6 times, and preferably 1.1 to 3.5 times in one direction. Commercially available cyclic polyolefin resin films, such as Esshina retardation film [manufactured by Sekisui Chemicals Co., Ltd.] and Zeonoa film [manufactured by Nippon Xeon Corporation], and in some cases further provided with a retardation. You may use

Since cyclic polyolefin resin films generally have poor surface activity, it is preferable to perform surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, and saponification treatment on the surface to be bonded to the polarizer layer. Do. Among them, plasma treatment and corona treatment that can be carried out relatively easily are suitable.

The cellulose ester resin is a fatty acid ester of cellulose, and a typical one is cellulose triacetate. As a cellulose ester-based resin film, suitable commercially available products, such as Fuji Tak TD80, Fuji Tak TD80UF, Fuji Tak TD80UZ, Fuji Tak TD40UZ (above, manufactured by Fujifilm Co., Ltd.), KC8UX2M, KC4UY (above, Konica Minolta Advanced Vanslayer) Co., Ltd.) etc. can be used suitably.

On the surface of the cellulose ester resin film, a liquid crystal layer or the like may be formed in order to improve the viewing angle characteristic. Further, it may be stretched to give a phase difference. The cellulose ester-based resin film is usually subjected to a saponification treatment in order to increase the adhesiveness with the polarizing film. The saponification treatment can be performed by a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

On the surface of the protective film, an optical layer such as a hard coat layer, an anti-glare layer, and an anti-reflection layer may be formed. The method of forming these optical layers on the surface of the protective film is not particularly limited, and a known method can be used.

The thickness of the protective film is preferably as thin as possible, preferably 90 µm or less, and more preferably 50 µm or less, from the demand for thinning. However, if it is too thin, since the strength decreases and a difficulty in workability occurs, it is usually preferably 5 μm or more.

(Other optical layers)

The polarizing plate can also be used as a composite polarizing plate in which other optical layers are laminated in practical use. The above protective film may have the function of such another optical layer.

Examples of other optical layers include a reflective polarizing film that transmits some kind of polarized light and reflects polarized light that exhibits opposite properties, a film with an anti-glare function having an uneven shape on the surface, and a film with an anti-glare function. A film, a reflective film having a reflective function on the surface, a semi-transmissive reflective film having a reflective function and a transmission function, and a viewing angle compensation film.

As a commercially available product equivalent to a reflective polarizing film that transmits a certain kind of polarized light and reflects polarized light showing the opposite property, for example, DBEF (manufactured by 3M, and in Japan, available from Sumitomo 3M Co., Ltd.) Available), and APF (manufactured by 3M, and also available from Sumitomo 3M Co., Ltd. in Japan). Examples of the viewing angle compensation film include an optical compensation film in which a liquid crystal compound is applied and oriented on the surface of a substrate, a retardation film made of a polycarbonate resin, a retardation film made of a cyclic polyolefin resin, and the like. As examples of commercially available products corresponding to an optical compensation film in which a liquid crystal compound is applied and aligned on the surface of a substrate, WV film (manufactured by Fujifilm Co., Ltd.), NH film (manufactured by JX Nikko Nisseki Energi Co., Ltd.), NV film [manufactured by JX Nikko Nissei Energy Co., Ltd.] and the like. In addition, as examples of commercially available products corresponding to retardation films made of cyclic polyolefin resins, Aton film (manufactured by JSR Corporation), Esshina retardation film (manufactured by Sekisui Chemical Co., Ltd.), and Zeonoa film (Nippon Xeon Co., Ltd. production], etc. are mentioned.

(Adhesive layer)

When bonding the polarizer layer and the protective film through the pressure-sensitive adhesive layer, the pressure-sensitive adhesive constituting the pressure-sensitive adhesive layer is usually an acrylic resin, a styrene resin, a silicone resin, etc. as a base polymer, and thereto, an isocyanate compound, an epoxy compound And a composition to which a crosslinking agent such as an aziridine compound is added. Further, fine particles may be blended in the pressure-sensitive adhesive to form a pressure-sensitive adhesive layer exhibiting light scattering properties.

The thickness of the pressure-sensitive adhesive layer is preferably 1 to 40 µm, but it is preferable to make it thin within a range that does not impair properties including workability and durability, and more preferably 3 to 25 µm. The thickness of 3 to 25 µm is suitable for suppressing dimensional change of the polarizer layer while having good workability. If the thickness of the pressure-sensitive adhesive layer is less than 1 μm, the adhesiveness decreases, whereas if the thickness of the pressure-sensitive adhesive layer exceeds 40 μm, the pressure-sensitive adhesive is likely to protrude.

Formation of the pressure-sensitive adhesive layer on the protective film or polarizer layer may be performed by applying a pressure-sensitive adhesive solution containing each component including the above-described base polymer to the protective film or polarizer layer, and drying the pressure-sensitive adhesive layer formed on the separator. , You may perform by a method of transferring to a protective film surface or a polarizer layer surface. When a pressure-sensitive adhesive layer is directly formed on the former protective film or polarizer layer, it is customary to attach a separator to the pressure-sensitive adhesive layer and temporarily attach and protect the surface until it is bonded to the other film. It is also possible to omit bonding of the other film to the pressure-sensitive adhesive layer. In addition, when the pressure-sensitive adhesive layer formed on the latter separator is transferred, the separator is peeled when bonding to the other film. When the pressure-sensitive adhesive layer is formed by directly applying the pressure-sensitive adhesive solution to the protective film or polarizer layer, the pressure-sensitive adhesive layer formed on the protective film or polarizer layer and the pressure-sensitive adhesive layer formed on the separator is transferred to the protective film or polarizer layer The adhesive layer formation surface of the protective film or the polarizer layer, and/or the bonding surface of the adhesive layer may be subjected to adhesion treatment, for example, a corona treatment, if necessary. Also when bonding the pressure-sensitive adhesive layer formed on one film to the other film, the bonding surface of the other film and/or the bonding surface of the pressure-sensitive adhesive layer can be similarly subjected to adhesion treatment as necessary.

(Adhesive layer)

When bonding the polarizer layer and the protective film through an adhesive layer, the adhesive constituting the adhesive layer may be, for example, a polyvinyl alcohol-based resin aqueous solution, an aqueous two-component urethane emulsion adhesive, or the like. Among them, an aqueous polyvinyl alcohol-based resin solution is suitably used. In the polyvinyl alcohol resin used as an adhesive, in addition to a vinyl alcohol homopolymer obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, a vinyl alcohol obtained by saponifying a copolymer of vinyl acetate and other monomers copolymerizable therewith. And modified polyvinyl alcohol-based polymers in which these hydroxyl groups are partially modified. To the water-based adhesive, a polyhydric aldehyde, a water-soluble epoxy compound, a melamine-based compound, a zirconia compound, a zinc compound, or the like may be added as an additive. In the case of using such a water-based adhesive, the adhesive layer obtained next is usually much thinner than 1 µm, and the adhesive layer is virtually not observed even when the cross section is observed with an ordinary optical microscope.

Bonding of a film using a water-based adhesive can be performed by a method of bonding both films through the adhesive and pressing with a roll or the like to dry. For example, after uniformly applying an adhesive to the surface of one film, a method of superimposing the other film thereon, or a method of introducing an adhesive between both films are employed. The adhesive is usually applied at a temperature of 15 to 40°C after its preparation, and the bonding temperature is usually in the range of 15 to 30°C.

In the case of using a water-based adhesive, after bonding the film, it is dried to remove water contained in the adhesive. The temperature of the drying furnace is preferably 30 to 90°C. If the drying temperature is less than 30°C, there is a tendency that the adhesive surface is easily peeled off. On the other hand, when the temperature exceeds 90°C, there is a concern that the optical performance of the polarizer layer or the like may be deteriorated by heat. Drying time can be 10 to 1,000 seconds.

After drying, it may also be cured for about 12 to 600 hours at room temperature or at a temperature slightly higher than that, for example, about 20 to 45°C. The temperature at the time of curing is generally set lower than the temperature employed at the time of drying.

In addition, a photocurable adhesive may be used as the non-aqueous adhesive. As a photocurable adhesive, a mixture of a photocurable epoxy compound and a photocationic polymerization initiator, etc. are mentioned, for example.

A photocurable adhesive is an adhesive that cures by irradiating an active energy ray such as ultraviolet rays, and includes, for example, a polymerizable compound and a photopolymerization initiator, a photoreactive resin, a binder resin and a photoreactive crosslinking agent. And the like. Examples of the polymerizable compound include photopolymerizable monomers such as photocurable epoxy monomers, photocurable acrylic monomers, and photocurable urethane monomers, and oligomers derived from these monomers. Further, examples of the photopolymerization initiator include those containing substances that generate active species such as neutral radicals, anionic radicals, and cationic radicals when irradiated with active energy rays such as ultraviolet rays. As a photocurable adhesive containing a polymerizable compound and a photoinitiator, it is preferable to contain a photocurable epoxy monomer and a photocationic polymerization initiator.

Bonding of the film using a photocurable adhesive is performed by, for example, casting, Mayer bar coat method, gravure coat method, comma coater method, doctor blade method, die coat method, dip coat method, spray method, etc. to the adhesive surface of the film. It can be performed by a method of applying and overlapping two films. The casting method is a method in which an adhesive is poured on the surface of the two films to be coated while moving in an approximately vertical direction, an approximately horizontal direction, or an oblique direction between the two films to be spread.

After applying the adhesive to the surface of the film, it is bonded by sandwiching the film with a nip roll or the like. Further, a method of uniformly spreading the laminate by pressing it with a roll or the like can also be suitably used. In this case, the material of the roll may be metal or rubber. Further, a method of making this laminated body pass between a roll and a roll, and pressing and widening it is also preferably employed. In this case, the two rolls may be of the same material or different materials. It is preferable that the thickness of the adhesive layer after bonding using a nip roll or the like before drying or curing is 5 µm or less and 0.01 µm or more.

The adhesion surface of the film may be appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, frame (flame) treatment, and saponification treatment in order to improve the adhesion. The saponification treatment can be performed by a method of immersing in an aqueous solution of an alkali such as sodium hydroxide or potassium hydroxide.

When a photocurable adhesive is used as the adhesive, the photocurable adhesive is cured by irradiating an active energy ray after laminating the film. The light source of the active energy ray is not particularly limited, but an ultraviolet ray having a light emission distribution at a wavelength of 400 nm or less is preferable, and specifically, a low pressure mercury lamp, a medium pressure mercury lamp, a high pressure mercury lamp, an ultra high pressure mercury lamp, a chemical lamp, a black light lamp, a microwave excitation mercury lamp. And metal halide lamps are preferably used.

The intensity of irradiation of light to the photocurable adhesive is appropriately determined by the composition of the photocurable adhesive, and is not particularly limited, but the irradiation intensity in the wavelength region effective for activation of the polymerization initiator is 0.1 to 6,000 mW/cm ² It is desirable. When the irradiation intensity is in this range, the reaction time does not become too long, and there is little possibility of causing yellowing of the curable compound or deterioration of the polarizer layer due to heat radiated from the light source and heat generated during curing of the photocurable adhesive. The time for irradiating light to the photocurable adhesive is applied depending on the adhesive to be cured, and is also not particularly limited, but the cumulative amount of light represented by the product of the above-described irradiation intensity and irradiation time is 10 to 10,000 mJ/cm ² It is preferable to be set as possible. When the accumulated light amount to the photocurable adhesive is in this range, a sufficient amount of active species derived from the polymerization initiator is generated, the curing reaction can be more reliably advanced, and the irradiation time is not too long, and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 µm, preferably 0.01 µm or more, 2 µm or less, more preferably 0.01 µm or more, and 1 µm or less.

In the case of curing the photocurable adhesive of a film including a polarizer layer or a protective film by irradiation with active energy rays, the polarization degree, transmittance and color of the polarizer layer, and the transparency of the protective film, etc., are not deteriorated in all functions of the polarizing plate It is preferable to perform curing with

[Substrate film peeling process (S60)]

In the manufacturing method of a polarizing plate of this embodiment, as shown in FIG. 2, after the protective film bonding process (S50) which bonds a protective film to a polarizer layer, a base film peeling process (S60) is performed. The base film used in the resin layer formation process is peeled from the polarizing laminated film here. The peeling method of the base film is not particularly limited, and a method similar to that of the separator peeling step performed on a polarizing plate having an ordinary pressure-sensitive adhesive can be adopted. After the protective film bonding step (S50), the base film may be immediately peeled off as it is, or after winding up in a roll shape once, a separate peeling step may be provided to peel the base film.

After peeling the base film, the polarizer layer or the primer layer formed thinly on the surface thereof is exposed, but can be used as a polarizing plate as it is. In this case, it is a common practice to form a pressure-sensitive adhesive layer for bonding to a display element such as a liquid crystal cell or another optical film on the surface of the polarizer layer or the primer layer. In addition, a separate protective film may be bonded to the surface of the polarizer layer or primer layer exposed by the peeling of the base film using an adhesive to obtain a polarizing plate having a structure in which the polarizer layer is sandwiched by two protective films. In this case, it is a common practice to form a pressure-sensitive adhesive layer for bonding to a display element such as a liquid crystal cell or another optical film on one protective film surface.

Example

Hereinafter, the present invention will be described in more detail by showing examples and comparative examples, but the present invention is not limited by these examples. In the examples,% and parts indicating content or amount of use are based on weight unless otherwise specified.

[Example 1]

(Base film)

As the base film, an unstretched polypropylene film (melting point 163°C) having a thickness of 110 μm was used.

(Primer layer formation process)

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Kosei Chemical Industry Co., Ltd.) having an average polymerization degree of 1,100 and a saponification degree of 99.5 mol% was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution having a concentration of 3%. . To the obtained aqueous solution, a crosslinking agent ("Sumirez Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.), which is a 30% aqueous solution of a water-soluble epoxy resin, was mixed in a ratio of 5 parts to 6 parts of the solid content of polyvinyl alcohol. The obtained mixed aqueous solution was coated on the corona-treated substrate film using a microgravure coater, and dried at 80° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm.

(Polyvinyl alcohol-based resin layer formation process)

Polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd.) having an average polymerization degree of 2,400 and a saponification degree of 98.0 to 99.1 mol% was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution having a concentration of 8%. The obtained aqueous solution was coated on the primer layer using a lip coater, and dried at 80° C. for 20 minutes to prepare a laminated film comprising three layers of a base film, a primer layer, and a polyvinyl alcohol-based resin layer. The thickness of the polyvinyl alcohol-based resin layer was 10 µm.

(Stretching process)

About the laminated film obtained above, the free end uniaxial stretching of 5.8 times was performed at 160 degreeC, and the stretched film was obtained. The thickness of the polyvinyl alcohol-based resin layer after stretching was 5.0 µm.

(Dyeing process)

The stretched film obtained above was dyed by immersing it for a predetermined time set for 60 to 180 seconds in a dyeing solution maintained at 26 to 30°C with the composition shown below, and then washed away excess iodine solution with pure water at 10°C. The time to be immersed in the dyeing solution and the iodine concentration were finely adjusted so that the luminous sensitivity corrected monolithic transmittance (Ty) obtained by the method described later of the finally obtained polarizing plate was around 42.0%.

<Dyeing solution>

100 parts of water

0.25-0.6 parts of iodine

10 parts potassium iodide

(Crosslinking process)

Subsequently, immersed in the first crosslinking solution having the composition shown below and maintained at 76°C for 240 seconds (first crosslinking step), and then, in the second crosslinking solution having the composition shown below and also maintained at 76°C. It was immersed for 60 seconds (2nd crosslinking process). Subsequently, it was washed with pure water at 10°C for 10 seconds, and finally dried at 80°C for 200 seconds. By the above operation, a polarizer layer was formed with a resin layer, and a polarizing laminated film was obtained.

<1st crosslinking solution>

100 parts of water

9.5 parts boric acid

<2nd crosslinking solution>

100 parts of water

9.5 parts boric acid

10 parts potassium iodide

(Protective film bonding process)

Polyvinyl alcohol powder ["KL-318" manufactured by Kuraray Co., Ltd.) having an average polymerization degree of 1,800 was dissolved in hot water at 95°C to prepare an aqueous polyvinyl alcohol solution having a concentration of 3%. To the obtained aqueous solution, the same crosslinking agent "Sumirez Resin 650" used in the above primer layer formation step was mixed in a ratio of 1 part to 2 parts of the solid content of polyvinyl alcohol to obtain an adhesive solution. After applying this polyvinyl alcohol-based adhesive to the polarizer layer of the polarizing laminated film, a protective film made of triacetyl cellulose ("KC4UY" manufactured by Konica Minolta Advanced Layer Co., Ltd.) was bonded thereto, and the protective film/ A multilayer film composed of an adhesive layer/polarizer layer/primer layer/base film was obtained.

(Base film peeling process)

The base film was peeled from the multilayer film obtained above, and a polarizing plate composed of a protective film/adhesive layer/polarizer layer/primer layer was produced. The base film can be easily peeled from the multilayer film above.

The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere ("V7100" manufactured by Nippon Bunko Co., Ltd.), Py=99.997%, single body a=-0.83, single body b=4.44, parallel a=- 1.32, parallel b=7.78, orthogonal a=0.60, orthogonal b=-0.05.

[Example 2]

A polarizing plate was produced in the same manner as in Example 1, except that the composition of the first crosslinking solution in the crosslinking step was 9.5 parts of boric acid and 0.5 parts of potassium iodide with respect to 100 parts of water. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.997%, monolith a=-0.81, monolith b=4.36, parallel a=-1.28, parallel b=7.62, orthogonal a=0.23, Orthogonal b=0.01.

[Example 3]

A polarizing plate was produced in the same manner as in Example 1, except that the composition of the first crosslinking solution in the crosslinking step was set to 9.5 parts of boric acid and 0.9 parts of potassium iodide with respect to 100 parts of water. Optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.995%, monolith a=-0.82, monolith b=4.44, parallel a=-1.29, parallel b=7.73, orthogonal a=0.33, Orthogonal b=-0.11.

[Example 4]

A polarizing plate was produced in the same manner as in Example 1, except that the amount of potassium iodide in the second crosslinking solution in the crosslinking step was changed to 7 parts per 100 parts of water. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere. Py=99.995%, monolith a=-0.92, monolith b=3.78, parallel a=-1.52, parallel b=6.65, orthogonal a=0.00, Orthogonal b=0.09.

[Example 5]

A polarizing plate was produced in the same manner as in Example 1, except that the amount of potassium iodide in the second crosslinking solution in the crosslinking step was changed to 5 parts per 100 parts of water. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.995%, monolith a=-1.09, monolith b=3.74, parallel a=-1.84, parallel b=6.56, orthogonal a=0.24, Orthogonal b=-0.38.

[Example 6]

A polarizing plate was produced in the same manner as in Example 1, except that the temperature of the first crosslinking solution in the crosslinking step was set to 78°C, the time to be immersed therein was set to 120 seconds, and the temperature of the second crosslinking solution was set to 78°C. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.995%, monolith a=-0.57, monolith b=3.90, parallel a=-0.92, parallel b=6.87, orthogonal a=1.05, Orthogonal b=0.18.

[Example 7]

The temperature of the first crosslinking solution in the crosslinking step was 78°C, the time to immerse therein was 120 seconds, the composition of the second crosslinking solution was 9.5 parts of boric acid and 6.8 parts of potassium iodide with respect to 100 parts of water, and the temperature was 70°C. Except for having done, a polarizing plate was produced in the same manner as in Example 1. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.995%, monolith a=-0.82, monolith b=3.25, parallel a=-1.41, parallel b=5.78, orthogonal a=0.79, Orthogonal b=-0.40.

[Example 8]

The temperature of the first crosslinking solution in the crosslinking step was 78°C, the time to immerse therein was 120 seconds, the composition of the second crosslinking solution was 9.5 parts of boric acid and 4.9 parts of potassium iodide per 100 parts of water, and the temperature was 70°C. Except for having done, a polarizing plate was produced in the same manner as in Example 1. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.995%, monolith a=-0.89, monolith b=2.99, parallel a=-1.55, parallel b=5.33, orthogonal a=0.66, Orthogonal b=-0.91.

[Comparative Example 1]

In the crosslinking step, in the same manner as in Example 1, except that the second crosslinking step was not performed, and the composition of the crosslinking solution was set to 9.5 parts of boric acid and 10 parts of potassium iodide per 100 parts of water, and the immersion time was set to 300 seconds. A polarizing plate was produced. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.993%, monolith a=-0.74, monolith b=3.86, parallel a=-1.20, parallel b=6.77, orthogonal a=0.19, Orthogonal b=-0.10.

[Comparative Example 2]

In the crosslinking step, in the same manner as in Example 1, except that the second crosslinking step was not performed, and the composition of the crosslinking solution was set to 9.5 parts of boric acid and 5 parts of potassium iodide per 100 parts of water, and the immersion time was set to 300 seconds. A polarizing plate was produced. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.994%, monolith a=-0.87, monolith b=3.06, parallel a=-1.49, parallel b=5.44, orthogonal a=0.14, Orthogonal b=-0.25.

[Comparative Example 3]

In the crosslinking step, the second crosslinking step was not carried out, except that the composition of the crosslinking solution was set to 9.5 parts of boric acid and 5 parts of potassium iodide per 100 parts of water, and the temperature was 78°C and the time to immerse in there was set to 300 seconds. A polarizing plate was produced in the same manner as in 1. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.991%, monolith a=-0.79, monolith b=2.31, parallel a=-1.41, parallel b=4.20, orthogonal a=1.12, Orthogonal b=-2.54.

[Comparative Example 4]

In the crosslinking step, the second crosslinking step was not carried out, except that the composition of the crosslinking solution was set to 9.5 parts of boric acid and 5 parts of potassium iodide per 100 parts of water, and the temperature was 78°C and the time to immerse in there was set to 300 seconds. A polarizing plate was produced in the same manner as in 1. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.979%, monolith a=-0.62, monolith b=1.77, parallel a=-1.15, parallel b=3.30, orthogonal a=2.15, Orthogonal b=-5.26.

[Comparative Example 5]

In the crosslinking step, in the same manner as in Example 1, except that the second crosslinking step was not performed, and the composition of the crosslinking solution was set to 9.5 parts of boric acid and 0 parts of potassium iodide per 100 parts of water, and the immersion time was set to 300 seconds. A polarizing plate was produced. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.800%, monolith a=0.00, monolith b=-0.69, parallel a=-0.91, parallel b=0.54, orthogonal a=20.63, Orthogonal b=-41.13.

[Comparative Example 6]

A polarizing plate was produced in the same manner as in Example 1, except that the temperature of the second crosslinking solution in the crosslinking step was set to 50°C. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.991%, monolith a=-1.00, monolith b=3.55, parallel a=-1.71, parallel b=6.30, orthogonal a=0.25, Orthogonal b=-0.54.

[Comparative Example 7]

A polarizing plate was produced in the same manner as in Example 1, except that the temperature of the first crosslinking solution in the crosslinking step was 50°C and the temperature of the second crosslinking solution was 50°C. The optical properties of the obtained polarizing plate were measured with a spectrophotometer having an integrating sphere, Py=99.930%, monolith a=-1.19, monolith b=5.03, parallel a=-1.78, parallel b=8.38, orthogonal a=0.22, Orthogonal b=-0.41.

[Measurement of polarization performance]

The optical properties of the polarizing plate were measured with a spectrophotometer having an integrating sphere ["V7100" manufactured by Nippon Bunko Co., Ltd.). In the measurement, the polarizing plate was set in the spectrophotometer so that the protective film side was the detector side, and light was incident from the primer layer side. When describing a specific measurement method, the MD transmittance and the TD transmittance are calculated in the wavelength range of 380 to 780 nm, and the monolithic transmittance and polarization at each wavelength are calculated based on the following equations (1) and (2). In addition, by correcting the luminous intensity according to the 2-degree field of view (C light source) of JIS Z 8701: 1 999 ``color display method-XYZ color system and X ₁₀ Y ₁₀ Z ₁₀ color system'' The corrected polarization degree (Py) was calculated. As described above, the time to be immersed in the dyeing solution in the dyeing step is adjusted so that the luminous sensitivity corrected monolithic transmittance (Ty) obtained in this way is around 42.0%. In addition, the obtained luminous intensity corrected polarization degree (Py) is shown in Table 1 together with the main conditions in the crosslinking process.

Here, ``MD transmittance'' is a transmittance when the direction of polarization emitted from the Glen-Thompson prism and the transmission axis of the polarizing plate sample are parallel, and ``TD transmittance'' is the transmittance of polarized light emitted from the Glen-Thompson prism. This is the transmittance when the direction and the transmission axis of the polarizing plate sample are orthogonal to each other, and in the following equations (1) and (2), they are described as "MD" and "TD", respectively.

Monolith transmittance (%) = (MD + TD) ÷ 2... … Equation (1)

Polarization degree (%) = [(MD-TD)÷(MD+TD)]×100... … Equation (2)

[Measurement of color]

The monolithic color (unit a, monolith b), parallel color (parallel a, parallel b), and orthogonal color (orthogonal a, orthogonal b) of the polarizing plate, a spectrophotometer having an integrating sphere ["V7100 manufactured by Nippon Bunko Co., Ltd. "]. Here, the orthogonal color refers to the color of the transmitted light when light is incident on two polarizing plates whose transmission axes are orthogonal, and the parallel color is the color of the transmittance when light is incident on two polarizing plates with parallel transmission axes. Means. In addition, the monolithic color means the color of transmitted light when light is incident on one polarizing plate. Values a and b are values of colors expressed in the Hunter Lab color system, and are calculated in accordance with JIS-Z8729J. A high color a value represents red, and a low color a represents green. On the other hand, a high color b value indicates yellow, and a low color indicates blue. In addition, the closer to 0, the closer to achromatic color.

As shown in Table 1, by performing the crosslinking process in two steps according to the present invention and setting the respective iodide concentration and temperature to predetermined conditions, the obtained polarizing plate can be further increased in visibility correction polarization degree Py.

From the use of a polarizing plate, for example, in a polarizing plate for LCD applications, since black display depends on the orthogonal color of the polarizing plate, it is sometimes required that the orthogonal color is neutral gray so that the original color can be clearly displayed (orthogonal color). a, orthogonal b is near zero). On the other hand, in order to prevent the short life of the light-emitting element by increasing the light emission intensity of the polarizing plate for OLED antireflection use, it is sometimes preferable that the single body transmittance is particularly high in the blue light wavelength region with a short lifetime (the single body b is small). According to the method of the present invention, it is possible to manufacture a polarizing plate having a color according to the above-described use and has excellent visibility correction polarization.

Claims (3)

A resin layer forming step of forming a polyvinyl alcohol-based resin layer on at least one side of a base film to obtain a laminated film,
A stretching step of uniaxially stretching the obtained laminated film so that the thickness of the polyvinyl alcohol-based resin layer is 10 µm or less to obtain a stretched film,
A dyeing step of immersing the obtained stretched film in a dyeing solution containing a dichroic dye to dye the polyvinyl alcohol-based resin layer to obtain a laminated film having a dyed layer, and
The obtained laminated film having a dyed layer was immersed in a crosslinking solution containing boric acid to crosslink the dyed polyvinyl alcohol-based resin layer, and a crosslinking step of forming a polarizer layer was provided,
The crosslinking step includes a first crosslinking step and a second crosslinking step in this order, and a laminated film having a dyed layer obtained in the dyeing step is prepared. In the first crosslinking step, the content of boric acid per 100 parts by weight of water is 1 to It is 20 parts by weight and is immersed in an aqueous solution having an iodide content of less than 1 part by weight at a temperature of 60°C or higher, and in the second crosslinking step, the content of boric acid per 100 parts by weight of water is 1 to 20 parts by weight, and the content of iodide A method for producing a polarizing laminated film that is immersed in an aqueous solution of 2 parts by weight or more at a temperature of 60°C or higher. The method for producing a polarizing laminated film according to claim 1, wherein the stretching step is performed by uniaxially stretching the laminated film at a draw ratio of more than 5 times. A process of producing a polarizing laminated film by the method according to claim 1 or 2, a protective film bonding process of bonding a protective film to a surface of the obtained polarizing laminated film opposite to the base film, and
A method for producing a polarizing plate, comprising: a base film peeling step of peeling the base film from the polarizing laminated film after bonding the protective film.

Images