JP2012103595A - Method for manufacturing polarizing plate, and polarizing plate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for manufacturing a polarizing plate, which allows a base film to be used as a protection film as it is, and to provide a polarizing plate obtained by the method.SOLUTION: The method for manufacturing a polarizing plate includes: a resin layer formation step of forming a resin layer composed of a polyvinyl alcohol-based resin, directly on the surface layer side of a base film having a surface layer composed of a polyethylene resin; a uniaxial drawing step of uniaxially drawing a laminate film including the base film and the resin layer together with the base film ; and a dyeing step of dyeing the laminate film subjected to uniaxial drawing, with dichroic dye. The polarizing plate is a laminate film including an aligned base film having a surface layer composed of a polyethylene resin and an aligned resin layer laminated on the surface layer of the base film and composed of a polyvinyl alcohol-based resin, where the base film and the resin layer are of the same alignment direction and the resin layer is a polarizer layer in which a dichroic dye is adsorbed and aligned on the polyvinyl alcohol-based resin.

Description

  The present invention relates to a method for producing a polarizing plate and a polarizing plate obtained thereby.

  A polarizing plate is widely used as a polarized light supplying element and a polarized light detecting element in a liquid crystal display device. As such a polarizing plate, a polarizing film made of a polyvinyl alcohol resin and having a protective film made of triacetylcellulose bonded on one or both sides has been used. In recent years, notebook personal computers for liquid crystal display devices have been used. With the development of mobile devices such as mobile phones and mobile phones, as well as the development of large televisions, there is a demand for thinner and lighter polarizing plates.

  As a method for obtaining an ultra-thin polarizing plate having a thickness of 10 μm or less, for example, in JP-A 2000-338329 (Patent Document 1), a polyvinyl alcohol aqueous solution is applied to a thermoplastic resin film as a base material. A method is disclosed in which a resin layer is formed, and the entire thermoplastic resin film is stretched and dyed. Patent Document 1 exemplifies a case where a polyethylene film having a surface layer of an ethylene-vinyl acetate copolymer, a polypropylene film, a nylon film, or the like is used as a thermoplastic resin film serving as a base material. However, in such a method disclosed in Patent Document 1, the adhesion between the thermoplastic resin film as a base material and the polyvinyl alcohol-based resin is often insufficient, and after stretching, dyeing, crosslinking, drying and the like. Separation may occur in the process. In particular, peeling is likely to occur when stretching is performed at a high magnification in order to draw out high polarization performance.

  Moreover, in the method disclosed in Patent Document 1, when an attempt is made to directly use a thermoplastic resin film as a base material as a protective film, the adhesion is insufficient. In order to avoid this, it is possible to apply a primer layer or other undercoating treatment in a separate process, but the adhesiveness is still insufficient, and transfer to another substrate is required, making the process complicated and costly. It is not preferable because of the increase.

JP 2000-338329 A

  The present invention has been made to solve the above-described problems, and the object of the present invention is to release the above-described peeling between the base film and the resin layer made of a polyvinyl alcohol-based resin laminated thereon. An object of the present invention is to provide a method for producing a polarizing plate in which adhesiveness that can be suppressed can be obtained and the base film can be used as a protective film as it is, and to provide a polarizing plate having the adhesiveness.

  The method for producing a polarizing plate of the present invention includes a resin layer forming step of directly forming a resin layer made of a polyvinyl alcohol-based resin on the surface layer side of a base film having a surface layer made of polyethylene resin, and the base film and resin A laminate film comprising a layer and a base film and a stretching process, and a dyeing process of dyeing the uniaxially stretched film with a dichroic dye.

  In the manufacturing method of the polarizing plate of this invention, it is preferable that the said polyethylene resin is a low density polyethylene.

  The present invention is also a laminated film comprising an oriented base film having a surface layer made of a polyethylene resin, and a resin layer made of an oriented polyvinyl alcohol-based resin laminated on the surface layer of the base film. Also provided is a polarizing plate in which the orientation direction of the base film and the orientation direction of the resin layer are the same, and the resin layer is a polarizer layer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin. To do.

  In the polarizing plate of the present invention, the polyethylene resin is preferably low density polyethylene.

  According to the present invention, the base film and the resin layer made of a polyvinyl alcohol-based resin laminated on the base film can obtain the adhesion capable of suppressing the above-described peeling, and can be transferred to another base material. Without any problem, the base film can be used as it is as a protective film, and materials and processes can be rationalized.

It is a flowchart which shows a preferable example of the manufacturing method of the polarizing plate of this invention.

<Production method of polarizing plate>
FIG. 1 is a flowchart showing a preferred example of the method for producing a polarizing plate of the present invention. As shown in FIG. 1, the method for producing a polarizing plate of the present invention comprises a resin layer forming step in which a resin layer made of a polyvinyl alcohol resin is directly formed on the surface layer side of a base film having a surface layer made of polyethylene resin ( S10), a stretching step (S20) for uniaxially stretching the laminated film including the base film and the resin layer together with the base film, and a dyeing step (S30) for dyeing the uniaxially stretched film with a dichroic dye. This is performed in this order. By this manufacturing method, a polarizing plate provided with a polarizer layer having a thickness of 10 μm or less on a stretched substrate film can be obtained. Hereafter, each process of S10-S30 in FIG. 1 is demonstrated in detail.

[1] Resin layer forming step (S10)
In the resin layer forming step, a resin layer made of a polyvinyl alcohol-based resin is formed on one surface of the base film.

(Base film)
The base film in the present invention has a surface layer made of a polyethylene resin. Here, the “polyethylene resin” constituting the surface layer refers to homopolyethylene and a copolymer of ethylene and α-olefin. Examples of α-olefins include propylene, 1-butene, 1-pentene, 1-hexene, 4-methyl-1-pentene and the like. In the copolymer of ethylene and α-olefin, if the amount of α-olefin is excessively increased, the adhesion is impaired. Therefore, the content of α-olefin is preferably 15% by weight or less, and preferably 10% by weight or less. Is more preferable, and most preferably 5% by weight or less.

  The density of the polyethylene resin may be high-density polyethylene or low-density polyethylene, but is preferably low-density polyethylene from the viewpoint of transparency. Examples of density polyethylene include high pressure low density polyethylene (LDPE) and linear low density polyethylene (LLDPE) as defined in JIS K 6899-1: 2000. As an example of LDPE, Sumikasen: F208-1 sold by Sumitomo Chemical Co., Ltd. and the like can be mentioned. Examples of LLDPE include Sumikasen E: FV401, Sumikacene: F411-0, and the like. Among these, LLDPE having excellent stretchability is particularly preferable.

  The thickness of the surface layer is not particularly limited as long as it is not less than a thickness that does not hinder adhesion, and is preferably 1 μm or more. There is no particular limitation on the upper limit of the thickness, and the surface layer may occupy most of the base film. Furthermore, the base film itself may be formed of a polyethylene resin.

  The support portion excluding the surface layer of the base film is not particularly limited, and may be formed from a resin that is convenient for stretching the polyvinyl alcohol-based resin. Since the stretching of the polyvinyl alcohol-based resin is usually performed in the range of 90 to 180 ° C., a resin that can be stretched at a high magnification within this range may be selected as the support. Examples of such resins include polyolefin resins, polyester resins, cyclic polyolefin resins (norbornene 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 support of the base film may be a single layer using only one kind of the above-described resin, or may be a blend of two or more kinds of resins. Of course, it may be a multilayer instead of a single layer.

  Examples of the polyolefin resin include polyethylene and polypropylene, which are preferable because they can be stably stretched at a high magnification. Moreover, an ethylene-polypropylene copolymer obtained by copolymerizing propylene with ethylene can also be used. Copolymerization can be performed with other types of monomers, and examples of other types of monomers copolymerizable with propylene include ethylene and α-olefins. As the α-olefin, an α-olefin having 4 or more carbon atoms is preferably used, and more preferably an α-olefin having 4 to 10 carbon atoms. 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; 3-methyl- Branched monoolefins such as 1-butene, 3-methyl-1-pentene and 4-methyl-1-pentene; vinylcyclohexane and the like. The copolymer of propylene and other monomers copolymerizable therewith may be a random copolymer or a block copolymer. The content of the structural unit derived from the other monomer in the copolymer is determined by infrared (IR) spectrum according to the method described on page 616 of “Polymer Analysis Handbook” (1995, published by Kinokuniya). It can be obtained by measuring.

  Among the above-mentioned, propylene-based resins constituting the propylene-based resin film include propylene homopolymer, propylene-ethylene random copolymer, propylene-1-butene random copolymer, and propylene-ethylene-1-butene random. A copolymer is preferably used.

  The stereoregularity of the propylene resin constituting the propylene resin film is preferably substantially isotactic or syndiotactic. A propylene-based resin film made of a propylene-based resin having substantially isotactic or syndiotactic stereoregularity has relatively good handleability and excellent mechanical strength in a high-temperature environment.

  The polyester resin is a polymer having an ester bond and is mainly a polycondensate of a polyvalent carboxylic acid and a polyhydric alcohol. As the polyvalent carboxylic acid used, divalent dicarboxylic acid is mainly used, and examples thereof include isophthalic acid, terephthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. In addition, divalent diol is mainly used as the polyhydric alcohol used, and examples thereof include propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol. Specific examples of the resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexane dimethyl terephthalate, and polycyclohexane dimethyl naphthalate. These blend resins and copolymers can also be suitably used.

  As the cyclic polyolefin resin, a norbornene resin is preferably used. The cyclic polyolefin resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described, for example, in JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers), And graft polymers obtained by modifying them with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Various products are commercially available as cyclic polyolefin resins. As specific examples, Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (manufactured by Nippon Zeon Corporation), ZEONEX (ZEONEX) (Registered trademark) (manufactured by ZEON CORPORATION) and Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.).

Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin. For example, 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, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, as the (meth) acrylic resin, a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those obtained by modifying a part of the hydroxyl group with other types of substituents are also included. Among these, cellulose triacetate is particularly preferable. Many products of cellulose triacetate are commercially available, which is advantageous in terms of availability and cost. Examples of commercially available products of cellulose triacetate include Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UZ (Fuji Film ( Co., Ltd.), Fujitac (registered trademark) TD40UZ (Fuji Film Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), and the like.

  The polycarbonate resin is an engineering plastic made of a polymer in which monomer units are bonded via a carbonate group, and is a resin having high impact resistance, heat resistance, and flame retardancy. Moreover, since it has high transparency, it is suitably used in optical applications. For optical applications, resins called modified polycarbonates in which the polymer skeleton is modified to lower the photoelastic coefficient, copolymerized polycarbonates with improved wavelength dependency, and the like are also commercially available and can be suitably used. Such polycarbonate resins are widely commercially available. For example, Panlite (registered trademark) (Teijin Chemicals Ltd.), Iupilon (registered trademark) (Mitsubishi Engineering Plastics), SD Polyca (registered trademark) (Sumitomo) Dow Co., Ltd.), Caliber (registered trademark) (Dow Chemical Co., Ltd.) and the like.

  Any appropriate additive may be added to the support of the base film in addition to the above-described thermoplastic resin. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. . The content of the thermoplastic resin exemplified above in the support of 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. This is because when the content of the thermoplastic resin in the support of the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  The resin forming the support is preferably excellent in adhesion to the polyethylene resin, but even if the resin is inferior in adhesion to the polyethylene resin, the adhesion is achieved by interposing an adhesive layer between the surface layer and the support. Can also be increased. In this case, the support, the surface layer, the adhesive layer, and the like can be co-extruded by multilayer melt extrusion or the like to form a film at a time.

  Although the thickness of a base film can be determined suitably, generally 1-500 micrometers is preferable from the point of workability | operativity, such as intensity | strength and a handleability, 1-300 micrometers is more preferable, 5-200 micrometers is further more preferable. The thickness of the base film is most preferably 5 to 150 μm.

  In the present invention, a base film having a surface layer made of a polyethylene resin is used. In order to provide excellent adhesion between the base film and a resin layer made of a polyvinyl alcohol-based resin, the surface layer has a corona. Treatment, plasma treatment, flame treatment, or the like may be performed.

  The base film in the present invention has a retardation value represented by the following formula (1) after being stretched in the stretching step described later. If this phase difference value is large, there may be a problem that interference unevenness is seen when mounted on a liquid crystal display device. Such retardation value can be measured by, for example, stretching the base film without applying polyvinyl alcohol resin. For the measurement of the phase difference value, a phase difference measurement device (KOBRA-WPR: trade name) such as that sold by Oji Scientific Instruments Co., Ltd. can be used. Moreover, even after extending | stretching a laminated | multilayer film, only a base film can be taken out by scrubbing only a polyvinyl alcohol resin layer, immersing the film in 80-90 degreeC hot water. The base film thus taken out can be measured for a retardation value with the above-described retardation measuring device or the like.

  Specifically, this is a defect in which a rainbow pattern due to a phase difference value existing between polarized light and a polarizer generated when light enters the base film from the backlight is observed. Such a rainbow pattern is particularly noticeable when a brightness enhancement film or the like is sandwiched between the base film and the backlight, resulting in poor display.

  The retardation value of the base film after stretching increases depending on the stretching ratio, and has a retardation value of 10 nm or more even in a region where the magnification is low. When this retardation value becomes 4000 nm or more by using a resin that easily expresses a retardation value for the support, increasing the draw ratio, or increasing the thickness of the substrate, it is mounted on a liquid crystal display device. A rainbow pattern becomes noticeable. In order to avoid this, the retardation value of the base film is preferably 3000 nm or less, more preferably 2000 nm or less, and most preferably 1000 nm or less.

  Moreover, about the NZ coefficient defined by following formula (2), since the lower one has a small phase difference value at the time of a perspective view, the lower one is preferable. The NZ coefficient is preferably 2.5 or less, more preferably 1.8 or less, and most preferably 1.6 or less.

_{R = (n x -n y)} × d ......... (1)
_{NZ = (n x -n z)} / (n x -n y) ......... (2)
Here, R represents the retardation value, d represents the thickness of the base film, and NZ represents the NZ coefficient. Further, _nx is the refractive index in the direction in which the refractive index is maximum in the film plane, and usually corresponds to the refractive index in the stretching direction. n _y in the film plane, the refractive index in the direction orthogonal to the n _x. n _z is a refractive index in the direction orthogonal to the n _x and n _y, corresponding to the thickness direction of the refractive index of the substrate film.

(Resin layer)
The polyvinyl alcohol resin constituting the resin layer laminated on the surface layer side of the base film is preferably a completely saponified product. The range of the saponification degree is preferably 80.0 to 100.0 mol%, more preferably 90.0 to 99.5 mol%, and more preferably 94.0 to 99.0 mol%. % Is most preferred. When the degree of saponification is less than 80.0 mol%, the obtained polarizing plate has a problem that the water resistance and heat and moisture resistance are remarkably inferior. In addition, when a polyvinyl alcohol-based resin having a saponification degree exceeding 99.5 mol% is used, the dyeing speed is remarkably slow, and a polarizing plate having sufficient polarization performance may not be obtained. There may be a problem that takes several times longer than usual.

  The saponification degree as used herein is a unit ratio (mol%) representing the ratio of the acetate group contained in the polyvinyl acetate resin, which is a raw material for the polyvinyl alcohol resin, to a hydroxyl group by the saponification step. Is a numerical value defined by the following formula. It can be determined by the method defined in JIS K 6726 (1994).

Saponification degree (mol%) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100
The higher the degree of saponification, the higher the proportion of hydroxyl groups, that is, the lower the proportion of acetate groups that inhibit crystallization.

  Further, the polyvinyl alcohol resin used in the present invention may be a modified polyvinyl alcohol partially modified. Examples include polyvinyl alcohol resins modified with olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, alkyl esters of unsaturated carboxylic acids, acrylamide, and the like. The proportion of modification is preferably less than 30 mol%, and more preferably less than 10 mol%. When modification exceeding 30 mol% is performed, it becomes difficult to adsorb the dichroic dye, resulting in a problem that the polarization performance is lowered.

  The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, more preferably 1500 to 8000, and most preferably 2000 to 5000. The average degree of polymerization here is also a numerical value determined by a method defined by JIS K 6726 (1994).

  Examples of the polyvinyl alcohol resin having such characteristics include PVA124 (degree of saponification: 98.0 to 99.0 mol%) and PVA117 (degree of saponification: 98.0 to 99.0) manufactured by Kuraray Co., Ltd. Mol%), PVA624 (degree of saponification: 95.0 to 96.0 mol%) and PVA617 (degree of saponification: 94.5 to 95.5 mol%); for example, AH- manufactured by Nippon Synthetic Chemical Industry Co., Ltd. 26 (degree of saponification: 97.0-98.8 mol%), AH-22 (degree of saponification: 97.5-98.5 mol%), NH-18 (degree of saponification: 98.0-99. 0 mol%), and N-300 (degree of saponification: 98.0 to 99.0 mol%); for example, JC-33 (degree of saponification: 99.0 mol% or more) of Nippon Vinegar Pival Co., Ltd. , JM-33 (degree of saponification: 93.5 to 95.5 mol%), JM 26 (degree of saponification: 95.5-97.5 mol%), JP-45 (degree of saponification: 86.5-89.5 mol%), JF-17 (degree of saponification: 98.0-99. 0 mol%), JF-17L (degree of saponification: 98.0 to 99.0 mol%), JF-20 (degree of saponification: 98.0 to 99.0 mol%), and the like. Can be suitably used.

  The thickness of the resin layer to be formed is preferably more than 3 μm and not more than 30 μm, more preferably 5 to 20 μm. If it is 3 μm or less, it becomes too thin after stretching and the dyeability is remarkably deteriorated. If it exceeds 30 μm, the thickness of the finally obtained polarizer layer may exceed 10 μm, which is not preferable.

  The resin layer is preferably formed by applying a polyvinyl alcohol resin solution obtained by dissolving polyvinyl alcohol resin powder in a good solvent onto one surface of the base film, and evaporating the solvent to dry the resin layer. It is formed. By forming the resin layer in this way, it can be formed thin. As a method of applying a polyvinyl alcohol resin solution to a base film, a wire bar coating method, a reverse coating, a roll coating method such as gravure coating, a die coating method, a comma coating method, a lip coating method, a spin coating method, a screen coating method. A method, a fountain coating method, a dipping method, a spray method, and the like can be appropriately selected from known methods and employed. A drying temperature is 50-200 degreeC, for example, Preferably it is 60-150 degreeC. The drying time is, for example, 2 to 20 minutes.

[2] Stretching step (S20)
In the subsequent stretching step, the laminated film including the base film and the resin layer is uniaxially stretched together with the base film to obtain a stretched film. Preferably, uniaxial stretching is performed so that the stretching ratio is more than 5 times and not more than 17 times. More preferably, it is uniaxially stretched so that the stretch ratio is more than 5 times and not more than 8 times. When the draw ratio is 5 times or less, the resin layer made of the polyvinyl alcohol-based resin is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer may not be sufficiently high. On the other hand, when the draw ratio exceeds 17 times, the laminated film is easily broken during stretching, and at the same time, the thickness of the stretched film becomes unnecessarily thin, and the workability and handling properties in the subsequent steps may be reduced. The stretching process in the stretching step (S20) is not limited to one-stage stretching, and can be performed in multiple stages. In the case of performing in multiple stages, the stretching process is performed so that the stretching ratio is more than 5 times by combining all stages of the stretching process.

  In the stretching step (S20) in the present embodiment, a longitudinal stretching process performed in the longitudinal direction of the laminated film, a lateral stretching process stretching in the width direction, and the like can be performed. Examples of the longitudinal stretching method include an inter-roll stretching method and a compression stretching method, and examples of the transverse stretching method include a tenter method.

  In addition, as the stretching treatment, either a wet stretching method or a dry stretching method can be adopted, but the use of the dry stretching method is preferable because the temperature at which the laminated film is stretched can be selected from a wide range.

[3] Dyeing process (S30)
In the dyeing step, the uniaxially stretched film (stretched film) is dyed with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Examples of organic dyes include 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, Spura Blue G, Spura Blue GL, Spura Orange GL, Direct Sky Blue, Direct First Orange S, First Black, etc. can be used. One kind of these dichroic substances may be used, or two or more kinds may be used in combination.

  A dyeing process is performed by immersing the whole stretched film in the solution (dyeing solution) containing the said dichroic dye, for example. As the staining solution, a solution in which the dichroic dye is dissolved in a solvent can be used. As a solvent for 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, more preferably 0.02 to 7% by weight, and particularly preferably 0.025 to 5% by weight.

  When iodine is used as the dichroic dye, it is preferable to further add an iodide because the dyeing efficiency can be further improved. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Examples include titanium. The addition ratio of these iodides is preferably 0.01 to 10% by weight in the dyeing solution. Of the iodides, it is preferable to add potassium iodide. When potassium iodide is added, the ratio of iodine to potassium iodide is preferably in the range of 1: 5 to 1: 100, more preferably in the range of 1: 6 to 1:80 by weight. , Particularly preferably in the range of 1: 7 to 1:70.

  The immersion time of the stretched film in the dyeing solution is not particularly limited, but it is usually preferably in the range of 15 seconds to 15 minutes, more preferably 1 minute to 3 minutes. Moreover, it is preferable that it is in the range of 10-60 degreeC, and, as for the temperature of a dyeing | staining solution, it is more preferable that it exists in the range of 20-40 degreeC.

  In the dyeing step, a crosslinking treatment can be performed after the dyeing. The crosslinking treatment can be performed, for example, by immersing the stretched film in a solution containing a crosslinking agent (crosslinking solution). Conventionally known substances can be used as the crosslinking agent. Examples thereof include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. One kind of these may be used, or two or more kinds may be used in combination.

  As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. As the solvent, for example, water can be used, but an organic solvent compatible with water may be further included. Although the density | concentration of the crosslinking agent in a crosslinking solution is not limited to this, It is preferable to exist in the range of 1-20 weight%, and it is more preferable that it is 6-15 weight%.

  Iodide may be added to the crosslinking solution. By adding iodide, the in-plane polarization characteristics of the resin layer can be made more uniform. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The iodide content is 0.05 to 15% by weight, more preferably 0.5 to 8% by weight.

  The immersion time of the stretched film in the crosslinking solution is usually preferably from 15 seconds to 20 minutes, and more preferably from 30 seconds to 15 minutes. Moreover, it is preferable that the temperature of a crosslinking solution exists in the range of 10-80 degreeC.

  Finally, it is preferable to perform a washing step and a drying step. As the washing step, a water washing treatment can be performed. The water washing treatment can usually be performed by immersing the stretched film in pure water such as ion exchange water or distilled water. The water washing temperature is usually in the range of 3 to 50 ° C, preferably 4 to 20 ° C. The immersion time is usually 2 seconds to 300 seconds, preferably 3 seconds to 240 seconds.

  The washing step may be a combination of a washing treatment with an iodide solution and a water washing treatment, and a solution in which a liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, or propanol is appropriately blended may be used.

  It is preferable to perform a drying process after the washing process. Any appropriate method (for example, natural drying, ventilation drying, heat drying) can be adopted as the drying step. For example, the drying temperature in the case of heat drying is usually 20 to 95 ° C., and the drying time is usually about 1 to 15 minutes. Through the above dyeing step (S30), the resin layer has a function as a polarizer. In the present specification, a resin layer having a function as a polarizer is referred to as a “polarizer layer”.

  According to the method for producing a polarizing plate of the present invention as described above, good adhesion can be obtained between the base film and the resin layer made of the polyvinyl alcohol-based resin laminated thereon. Accordingly, the base film can be used as a protective film as it is without being transferred to another base material, and materials and processes can be rationalized.

<Polarizing plate>
The present invention is a laminated film comprising an oriented base film having a surface layer made of polyethylene resin and a resin layer made of an oriented polyvinyl alcohol-based resin laminated on the surface layer of the base film, There is also provided a polarizing plate in which the orientation direction of the base film is the same as the orientation direction of the resin layer, and the resin layer is a polarizer layer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin. . Such a polarizing plate of the present invention can be preferably produced by the above-described method for producing a polarizing plate of the present invention. In the polarizing plate of the present invention, as described above, since the base film and the resin layer made of the polyvinyl alcohol resin laminated thereon have good adhesion, it may be transferred to another base material. The base film is used as it is as a protective film. Also in the polarizing plate of this invention, it is preferable that the polyethylene resin which comprises the surface layer of a base film is a low density polyethylene.

  EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to these examples. In the examples, “%” and “part” representing the content or amount used are based on weight unless otherwise specified.

<Example 1>
[Method for creating base film]
A base material film in which a surface layer made of a polyethylene resin (“Sumitomo Sumikasen F411-0” manufactured by Sumitomo Chemical Co., Ltd.) is arranged on a support made of a polypropylene resin (“Sumitomo Noblen FLX80E4” manufactured by Sumitomo Chemical Co., Ltd.) It was produced by coextrusion molding using an extruder. The total thickness of the obtained base film was 90 μm, and the thickness ratio of each layer was the ratio of support / surface layer = 4/1. Corona discharge treatment was performed on the surface layer side of the substrate film.

[Formation of polyvinyl alcohol-based resin layer]
Polyvinyl alcohol powder (“PVA124” manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree 98.0-99.0 mol%) was dissolved in hot water at 95 ° C., and a polyvinyl alcohol aqueous solution having a concentration of 8% by weight. Was prepared. By applying the obtained aqueous solution onto the surface layer of the base film using a lip coater, and drying it at 80 ° C. for 2 minutes, at 70 ° C. for 2 minutes, and then at 60 ° C. for 4 minutes. A laminated film consisting of a base film / polyvinyl alcohol resin layer was prepared. The thickness of the dried polyvinyl alcohol resin layer was 10.3 μm.

[Creation of stretched film]
The laminated film was uniaxially stretched 5.8 times at a stretching temperature of 160 ° C. to obtain a stretched film. The obtained stretched film had a thickness of 29 μm, and the polyvinyl alcohol resin layer had a thickness of 4.8 μm. Peeling between the base film and the polyvinyl alcohol resin layer in the stretching process did not occur, and a good adhesion state was maintained. The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 331 nm when the phase difference value of this base film was measured by Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Dyeing / crosslinking]
(Dyeing process)
Thereafter, the stretched film is immersed in a 60 ° C. hot bath for 60 seconds, dyed by immersion for about 150 seconds in a dyeing solution that is a mixed aqueous solution of iodine and potassium iodide at 30 ° C., and then excess iodine is added with pure water at 10 ° C. The liquid was washed away. Next, it was immersed in a mixed aqueous solution of boric acid and potassium iodide at 76 ° C. for 600 seconds. Thereafter, it was washed with pure water at 10 ° C. for 4 seconds, and finally dried at 50 ° C. for 300 seconds. Through the above steps, a polarizer layer was formed from the resin layer to obtain a polarizing plate. Peeling between the base film and the polyvinyl alcohol resin layer did not occur in the dyeing / crosslinking step, and a good adhesion state was maintained.

[Check adhesion]
The obtained polarizing plate is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross hatch test based on JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) is performed. The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid which remained without peeling was 82/100.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The cellular phone was reassembled and visually evaluated in various display states such as white display, black display, and gray display, but no rainbow pattern was observed when the display device was observed from any angle.

<Example 2>
A polarizing plate was obtained in the same manner as in Example 1 except that the surface layer was changed to a polyethylene resin (“Sumitomo Sumikasen E FV401” manufactured by Sumitomo Chemical Co., Ltd.). The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 322 nm when the phase difference value of this base film was measured by Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Check adhesion]
The obtained polarizing plate is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross hatch test based on JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) is performed. The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid pattern remaining without peeling was 79/100.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The cellular phone was reassembled and visually evaluated in various display states such as white display, black display, and gray display, but no rainbow pattern was observed when the display device was observed from any angle.

<Example 3>
A polarizing plate was obtained in the same manner as in Example 1 except that the surface layer was changed to a polyethylene resin (“Sumitomo Sumikasen F208-1” manufactured by Sumitomo Chemical Co., Ltd.). The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 297 nm when the phase difference value of this base film was measured with Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Check adhesion]
The obtained polarizing plate is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross hatch test based on JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) is performed. The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid which remained without peeling was 98/100.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The cellular phone was reassembled and visually evaluated in various display states such as white display, black display, and gray display, but no rainbow pattern was observed when the display device was observed from any angle.

<Example 4>
Regarding the thickness of the base film, a polarizing plate was obtained in the same manner as in Example 3, except that the total thickness was 110 μm and the thickness ratio of each layer was the ratio of support / surface layer = 5/1. The same surface layer and support resin as in Example 3 were used. The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 889 nm when the phase difference value of this base film was measured with Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Check adhesion]
The obtained polarizing plate is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross hatch test based on JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) is performed. The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid which remained without peeling was 99/100.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The cellular phone was reassembled and visually evaluated in various display states such as white display, black display, and gray display, but no rainbow pattern was observed when the display device was observed from any angle.

<Comparative Example 1>
A polarizing laminated film was produced in the same manner as in Example 1 except that a single-layer film of a 90 μm-thick polypropylene resin (“Sumitomo Nobrene FLX80E4” manufactured by Sumitomo Chemical Co., Ltd.) was used as the base film. Although there was no problem in the stretching process, the polyvinyl alcohol resin layer was peeled off in the crosslinking process, and a stable and uniform polarizing plate could not be obtained. The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 924 nm when the phase difference value of this base film was measured with Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Check adhesion]
The obtained polarizing laminated film is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross-hatch test according to JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid which remained without peeling was 0/100.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The cellular phone was reassembled and visually evaluated in various display states such as white display, black display, and gray display, but no rainbow pattern was observed when the display device was observed from any angle.

<Comparative example 2>
A polarizing laminated film was produced in the same manner as in Comparative Example 1 except that a primer layer was applied to the surface of the base film used in Comparative Example 1. Creation of the primer layer is as follows. Polyvinyl alcohol powder (manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, saponification degree 99.5 mol%, trade name: Z-200) is dissolved in 95 ° C. hot water to give an aqueous solution having a concentration of 3% by weight. Prepared. The resulting aqueous solution was mixed with 5 parts by weight of a crosslinking agent (manufactured by Sumitomo Chemical Co., Ltd., trade name: Sumirez (registered trademark) Resin 650) with respect to 6 parts by weight of polyvinyl alcohol powder. The obtained mixed aqueous solution was coated on a base film of Comparative Example 1 subjected to corona treatment using a micro gravure coater and dried at 80 ° C. for 10 minutes to form a primer layer having a thickness of 0.2 μm. In this method, no peeling occurred in the stretching process, the dyeing process, and the peeling process.

[Check adhesion]
The obtained polarizing laminated film is bonded to a soda glass plate using a pressure-sensitive adhesive, and a cross-hatch test according to JIS D0202-1988 (what is described as “cross-cut adhesion test” in JIS) The adhesion was evaluated by the number of grids remaining without peeling per 100 grids. As a result, the grid which remained without peeling was 0/100.

<Comparative Example 3>
A polarizing laminate film was produced in the same manner as in Comparative Example 1 except that a single-layer film of a polyethylene terephthalate (PET) resin film having a thickness of 70 μm was used as the base film. Although no trouble occurred in the stretching process, the polyvinyl alcohol resin layer was peeled off in the crosslinking process, and a stable and uniform polarizing plate could not be obtained. The stretched substrate film was taken out by immersing the stretched film (stretched laminated film) in hot water at 80 ° C. to scrape off the resin layer. It was 4840 nm when the phase difference value of this base film was measured by Oji Scientific Instruments Co., Ltd. product: KOBRA-WPR.

[Implementation evaluation]
A λ / 4 phase difference plate was bonded to the polarizer layer side of the obtained polarizing plate using a pressure-sensitive adhesive layer. At this time, it was bonded so that the slow axis of the λ / 4 retardation value and the absorption axis of the polarizer were 45 degrees to obtain a circularly polarizing plate. A cell phone (P-01A) commercially available from NTT Docomo was disassembled and the liquid crystal cell was taken out. After peeling the polarizing plate on the backlight side to expose the surface of the liquid crystal cell, the above circular polarizing plate was bonded to the surface of the cell using a pressure-sensitive adhesive. At this time, the relationship between the prepared circularly polarizing plate and the circularly polarizing plate on the viewing side (originally attached to the commercial product) is that the slow axis of the retardation plate is orthogonal and the absorption axis of the polarizer is also The arrangement was orthogonal. As a result, the liquid crystal display device is in a normally black state. The mobile phone was reassembled and visually evaluated with various displays such as white display, black display, and gray display, but a rainbow pattern was observed and the display was unclear. This rainbow pattern was particularly noticeable when observed from an oblique angle in a white display state.

Claims (4)

A resin layer forming step of directly forming a resin layer made of a polyvinyl alcohol-based resin on the surface layer side of the base film having a surface layer made of polyethylene resin;
A stretching step of uniaxially stretching the laminated film including the base film and the resin layer together with the base film,
The manufacturing method of a polarizing plate including the dyeing process of dye | staining the film after the said uniaxial stretching with a dichroic dye.   The method for producing a polarizing plate according to claim 1, wherein the polyethylene resin is low-density polyethylene.   A laminated film comprising an oriented base film having a surface layer made of polyethylene resin, and a resin layer made of an oriented polyvinyl alcohol-based resin laminated on the surface layer of the base film, wherein the base film The orientation direction of the resin layer and the orientation direction of the resin layer are the same, and the resin layer is a polarizer layer in which a dichroic dye is adsorbed and oriented on a polyvinyl alcohol resin.   The polarizing plate according to claim 3, wherein the polyethylene resin is low-density polyethylene.

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