TW201530200A - Polarizer with less bubble deficiency - Google Patents

Abstract

Provided are a polarizer formed of a polyvinyl alcoholic resin, having 10 voids per square meter with a length in the direction of the absorption axis being equal to or larger than 100 [mu]m, a polarizing laminated film obtained by laminating the polarizer on at least one surface of a base film, a polarizing sheet obtained by laminating a transparent protecting film on at least one surface of the polarizer, and a method for producing same.

Description

Polarizer with less bubble defects

The present invention relates to a polarizer having less bubble defects and a method of manufacturing the same.

In recent years, a polarizing plate has been widely used as an optical element of a liquid crystal display device in a liquid crystal display device of a liquid crystal television, a mobile phone, or a personal computer. Recently, in order to reduce the size and weight of such liquid crystal display devices, a thin polarizing plate has been developed. A method of producing a polarizer and a polarizing plate by stretching and then dyeing a polyvinyl alcohol-based resin layer in an aqueous solution of a polyvinyl alcohol-based resin on the surface of the base film is proposed (Patent Documents 1 and 2). .

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2000-338329

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2009-93074

The inventor of the present invention discovered that in the manufacture of polarizers and polarizers In the method, when an aqueous solution of a polyvinyl alcohol-based resin is used, the polyvinyl alcohol-based resin easily absorbs bubbles in the preparation step of the aqueous solution, and forms a surface of the polyvinyl alcohol-based resin layer when the polyvinyl alcohol-based resin layer is formed. A circular concave defect may be caused by a bubble, or a void may be caused by a round or linear bubble defect generated in the extending direction of the extended resin layer. The inventors of the present invention provide a polarizing plate having a small number of voids due to a bubble defect, a polarizing laminated film formed by the polarizing film, and a method for producing the same.

The present invention provides a polarizer which is composed of a polyvinyl alcohol-based resin having a void length of 100 μm or more in the absorption axis direction of 10 pieces/m ² or less. Further, the present invention provides a polarizing plate in which at least one side of a base film is laminated, and a polarizing laminated film of the polarizing plate and at least a single-layer transparent protective film of the polarizing plate are laminated.

The length of the absorption axis of the polarizer direction is 100μm or more voids 10 pieces / m ² or less of the polarizing film laminate, to a typical manufacturing method comprising the system (a) to (c) of the steps to fabricate.

(a) Resin layer forming step: coating an aqueous solution of a polyvinyl alcohol-based resin which is defoamed under reduced pressure on at least one side of the base film to obtain a layer formed on at least one side of the base film a laminated film of a resin layer made of a vinyl alcohol-based resin; (b) an extending step: extending the laminated film to obtain a stretched film; (c) a dyeing step: forming a resin layer of a stretched film made of a polyvinyl alcohol-based resin The dichroic dye is dyed to form a polarizer layer.

The invention provides a surface on one side of a polarizer The method for producing a polarizing plate of a transparent protective film, comprising: a step of bonding a transparent protective film to a surface of the polarizing layer of the polarizing laminated film opposite to the substrate film side to obtain a multilayer film (attachment) Step); a step of peeling off the substrate film from the multilayer film (peeling step).

According to the present invention, when a polarizing plate is produced, an aqueous solution of a polyvinyl alcohol-based resin is depressurized and defoamed, and an aqueous solution of a polyvinyl alcohol-based resin is applied as a coating liquid to a base film to form a polyvinyl alcohol. In the case of the resin layer, it is possible to reduce the occurrence of cracks in the coating liquid and to generate a circular concave defect in the coating layer. As a result, even if the laminated film composed of the base film after coating and the polyvinyl alcohol-based resin layer is stretched, it is possible to provide a round or linear void due to bubble defects in the extending direction. A polarizer that suppresses generation and a polarizing laminate film including the polarizer.

10‧‧‧Polarized laminated film

11‧‧‧Base film

12‧‧‧Polarized film

13‧‧‧Polar plate

14‧‧‧Transparent protective film

Fig. 1 is a schematic cross-sectional view showing an example of a basic layer structure of a polarizing laminate film of the present invention.

Fig. 2 is a schematic cross-sectional view showing an example of a basic layer structure of a polarizing plate of the present invention.

Fig. 3 is a flow chart showing an embodiment of a method for producing a polarizing laminated film shown in Fig. 1.

Fig. 4 is a flow chart showing an embodiment of a method of manufacturing a polarizing plate shown in Fig. 2.

Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[Structure of polarizing laminated film]

Fig. 1 is a schematic cross-sectional view showing an example of a basic layer structure of a polarizing laminate film of the present invention. The polarizing laminate film 10 includes a base film 11 and a polarizer layer 12 formed on one surface of the base film 11. The polarizer layer 12 has a thickness of 10 μm or less and is formed of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented.

Each structural element will be described in detail below.

[Substrate film]

As the material of the base film 11, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, and elongation can be used. Specific examples of such a thermoplastic resin include cellulose ester resins such as cellulose triacetate, polyester resins, polyether oxime resins, polyfluorene resins, polycarbonate resins, and polyamines. Resin, polyimide resin, polyolefin resin, (meth)acrylic resin, cyclic polyolefin resin (norbornene resin), polyallylate resin, A polystyrene resin, a polyvinyl alcohol resin, a mixture of these, etc.

The material of the base film preferably contains at least one selected from the group consisting of a cellulose ester resin, a polyolefin resin, a cyclic polyolefin resin, and a (meth)acrylic resin.

In the present specification, "(meth)acrylic acid" means acrylic acid or methacrylic acid.

Cellulose ester resin, cellulose and fatty acid ester. Specific examples of such a cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Among these, cellulose triacetate is particularly preferred. Cellulose triacetate is available in a variety of commercially available products, and is also advantageous in terms of ease of availability and cost. Examples of commercially available cellulose triacetate include FUJITAC (registered trademark) TD80 (manufactured by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by FUJIFILM Co., Ltd.), and FUJITAC (registered trademark) TD80UZ ( FUJIFILM Co., Ltd., FUJITAC (registered trademark) TD40UZ (manufactured by FUJIFILM Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), KC4UY (manufactured by Konica Minolta Opto Co., Ltd.), and the like.

Examples of the polyolefin resin include polyethylene and polypropylene. When a base film made of polypropylene is used, it is preferable to extend at a high magnification because of ease of stability. As the cyclic polyolefin resin, a norbornene-based resin is preferably used. The cyclic polyolefin-based resin is a general term for a resin which is polymerized by using a cyclic olefin as a polymerization unit, and, for example, JP-A-1-240517, JP-A-3-14882, and JP-A-3-122137 The resin described in the Gazette. Specific examples thereof include 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 (representatively a random copolymer), And such graft polymers modified with unsaturated carboxylic acids or derivatives thereof, and such hydrides and the like. Specific examples of the cyclic olefin include a norbornene-based monomer.

Various products of the cyclic polyolefin resin are commercially available. Specific examples include Topas (registered trademark) (manufactured by Ticona Co., Ltd.), ARTON (registered trademark) (manufactured by JSR Co., Ltd.), ZEONOR (registered trademark) (made by Nippon Seon Co., Ltd.), ZEONEX (registered trademark) (made by Nippon Seon Co., Ltd.), APEL (registered trademark) (Mitsui Chemical Co., Ltd.).

As the (meth)acrylic resin, any suitable (meth)acrylic resin can be used. For example, poly(meth)acrylate such as polymethyl methacrylate, methyl methacrylate-(meth)acrylic acid copolymer, methyl methacrylate-(meth) acrylate copolymer, methyl group Methyl acrylate-acrylate-(meth)acrylic acid copolymer, methyl (meth)acrylate-styrene copolymer (MS resin, etc.), polymer having an alicyclic hydrocarbon group (for example: methyl methacrylate - Copolymer of cyclohexyl methacrylate, copolymer of methyl methacrylate-norphtyl (meth)acrylate, etc.). Preferably, a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate is used. The (meth)acrylic resin is more preferably a methyl methacrylate-based resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

In addition to the above thermoplastic resin, any suitable additive may be added to the base film 11. Examples of such an additive include an ultraviolet absorber, an antioxidant, a lubricant, a plasticizer, a release agent, an anti-coloring agent, a flame retardant, a nucleating agent, an antistatic agent, a pigment, and a coloring agent. The content of the above-exemplified thermoplastic resin in the substrate film is preferably from 50 to 100% by weight, more preferably from 50 to 99% by weight, still more preferably from 60 to 98% by weight, particularly preferably from 70 to 97% by weight. %. This is because when the content of the thermoplastic resin in the substrate film is less than 50% by weight, it may not be sufficient. The thermoplastic resin originally has high transparency and the like.

The thickness of the base film 11 can be appropriately determined, but it is preferably 1 to 500 μm, more preferably 1 to 300 μm, and more preferably 5 to 200 μm, in terms of workability such as strength and handleability. good. The thickness of the base film 11 is preferably from 5 to 150 μm.

In order to extend the base film to a temperature range suitable for the elongation of the polyvinyl alcohol-based resin, it is preferred to use a melting point of 110 ° C or higher. It is preferred to use a melting point system of 130 ° C or higher. When the melting point of the base film is less than 110 ° C, the elongation of the base film is likely to be melted in the stretching step (S20) to be described later, and the elongation temperature is not sufficiently increased, so that it is difficult to extend more than five times. The melting point of the substrate film is a value measured in accordance with ISO 3146 at a temperature rising rate of 10 ° C /min.

The base film 11 may be subjected to a corona treatment, a plasma treatment, a flame treatment or the like at least on the surface on the side where the polarizer layer 12 is formed in order to improve the adhesion to the polarizer layer 12. Further, in order to improve the adhesion, a thin layer such as a primer layer may be formed on the surface of the base film 11 on the side where the polarizing plate layer 12 is formed.

[Polarized film layer]

The polarizer of the present invention is a polarizer composed of a polyvinyl alcohol-based resin having a void length of 100 μm or more in the absorption axis direction of 10 pieces/m ² or less. The thickness of the polarizer is 10 μm or less, and may be thinner and 7 μm or less. A thin polarizing laminated film having a thickness of the polarizing plate layer 12 of 10 μm or less can be produced.

The polarizer layer 12 is specifically one in which a dichroic dye is adsorbed and oriented on a uniaxially stretched polyvinyl alcohol-based resin layer. As poly As the enol resin, those obtained by saponifying a polyvinyl acetate resin can be used. The polyvinyl acetate-based resin may, for example, be a copolymer of a monomer copolymerizable with vinyl acetate, or the like, in addition to a polyvinyl acetate of a homopolymer of vinyl acetate. Examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and decyl acrylates having an ammonium group.

The degree of saponification of the polyvinyl alcohol-based resin is 99.0 mol% or less. In the present invention, since the polyvinyl alcohol-based resin having a degree of saponification of 99.0 mol% or less can maintain a constant dyeing speed even when the uniaxial stretching is performed more than 5 times, it is possible to produce a thin film having high polarizing performance with good efficiency. The advantage of a polarizing laminated film. On the other hand, when a polyvinyl alcohol-based resin having a degree of saponification of more than 99.0 mol% is used, the dyeing speed is remarkably slow, and there is a case where a polarizing laminated film having sufficient polarizing properties cannot be obtained, and at the time of manufacture. There will be a bad situation in which the cost of the application is as many as the usual multiple times.

The degree of saponification of the polyvinyl alcohol-based resin is preferably 90 mol% or more, more preferably 94 mol% or more. If the degree of saponification is less than 90% by mole, the strength such as water resistance may be insufficient.

Here, the degree of saponification is defined by the ratio of the acetic acid group contained in the polyvinyl acetate-based resin of the raw material of the polyvinyl alcohol-based resin to the hydroxyl group by the saponification step, expressed as a unit ratio (% by mole). The value defined by the formula. It can be obtained by the method specified in JIS K 6726 (1994).

Degree of saponification (% by mole) = (number of hydroxyl groups) ÷ (number of hydroxyl groups + number of acetate groups) × 100

The higher the degree of saponification, the higher the proportion of the hydroxyl group, that is, the lower the proportion of the acetate group which hinders crystallization. Further, the polyvinyl alcohol-based resin used in the present invention is not particularly limited as long as the degree of saponification is 99.0 mol% or less, and may be a part of the modified modified polyvinyl alcohol. Examples of the modified polyvinyl alcohol include an olefin such as ethylene or propylene having a polyvinyl alcohol resin of about several %, an unsaturated carboxylic acid such as acrylic acid, methacrylic acid or crotonic acid, an alkyl ester of an unsaturated carboxylic acid, or acrylic acid. A modified person such as guanamine. The average degree of polymerization of the polyvinyl alcohol-based resin is also not particularly limited, but is preferably from 100 to 10,000, more preferably from 1,500 to 10,000.

Examples of the polyvinyl alcohol-based resin having such a property include PVA124 (saponification degree: 98.0 to 99.0 mol%) manufactured by Kuraray Co., Ltd., PVA117 (saponification degree: 98.0 to 99.0 mol %), and PVA624 ( Saponification degree: 95.0 to 96.0 mol%) and PVA617 (saponification degree: 94.5 to 95.5 mol%); for example, AH-26 (saponification degree: 97.0 to 98.8 mol%) manufactured by Nippon Synthetic Chemical Co., Ltd., AH -22 (saponification degree: 97.5 to 98.5 mol%), NH-18 (saponification degree: 98.0 to 99.0 mol%), and N-300 (saponification degree: 98.0 to 99.0 mol%); for example, JAPAN VAM & POVAL shares JF-17 (saponification degree: 98.0 to 99.0 mol%), JF-17L (saponification degree: 98.0 to 99.0 mol%), and JF-20 (saponification degree: 98.0 to 99.0 mol%) and the like.

The polyvinyl alcohol-based resin is applied to a substrate, and a resin layer is formed to allow the production of the polarizer layer 12 of the present invention. In the method of forming a resin layer of a polyvinyl alcohol-based resin, it is preferred to apply a polyvinyl alcohol-based resin solution insofar as it is easy to obtain a polarizing layer 12 having a desired thickness. A method of forming a resin layer by mounting on a substrate film 11. The polarizer layer 12 preferably has a stretching ratio of more than 5 times, more preferably more than 5 times and less than 8 times.

In the following description, "the polarizer layer made of a polyvinyl alcohol-based resin is formed on at least one surface of the base film, and the gap of the polarizer layer in the absorption axis direction of 100 μm or more is 10 pieces/m ^{2 .} The following method for producing a polarizing laminated film.

In the surface of at least one side of the base film, an aqueous solution of a polyvinyl alcohol-based resin which has been defoamed under reduced pressure is applied, and at least one side of the base film is formed with a polyvinyl alcohol-based resin. The resin layer forming step of the laminated film of the resin layer".

The aqueous solution of the polyvinyl alcohol-based resin coated on the substrate film usually contains 4% by weight to 10% by weight of the polyvinyl alcohol-based resin, preferably 6% by weight to 9% by weight. If it is 4% by weight or less, there is a need to lower the line speed due to the need for heat during drying, which leads to deterioration in productivity. When it is 10% by weight or more, the gelation is likely to occur, and the storage property is deteriorated. As the polyvinyl alcohol-based resin, those exemplified for use in the description of the polarizer can be used.

The aqueous solution of the polyvinyl alcohol-based resin is preferably an aqueous solution of a defoamed polyvinyl alcohol-based resin, and a method of defoaming is preferably performed by decompression under reduced pressure in terms of the efficiency of removal of the bubbles. Since the PVA aqueous solution is very easy to foam, and the generated bubbles are not easily broken, it is more preferable that the bubbles generated by the foaming are again mixed into the liquid by the pressure reduction, and the pressure is reduced in a state of being left to maintain the reduced pressure state. Waiting for bubbles to be removed from the aqueous solution

method

In the defoaming step of the present invention, a method of inhaling by a vacuum pump can be used. The container for defoaming is not particularly specified, and it can be easily carried out as long as it can withstand a reduced pressure. The pressure is reduced, and the pressure in the container (measured pressure) is usually lowered as much as possible. The lower the pressure is, the shorter the treatment time is, so it is suitable. The pressure (counting pressure) in the container is usually set to -0.04 MPa or less, preferably -0.05 MPa or less, more preferably -0.08 MPa or less, and particularly preferably -0.09 MPa or less. The treatment time is typically 30 minutes or longer, preferably 60 minutes or longer, more preferably 120 minutes or more, and may be extended without impairing productivity.

When an aqueous solution of a defoamed polyvinyl alcohol-based resin (also referred to as a PVA aqueous solution or a coating liquid) is applied, the temperature of the coating liquid to be supplied is such that the coating liquid does not make the substrate when it contacts the substrate. The upper limit may be set such that the film thickness of the polyvinyl alcohol-based resin layer to be formed is not affected, and the lower limit may be set so that the PVA aqueous solution does not gel. The temperature of the coating liquid is usually from 10 to 80 ° C, preferably from 15 to 60 ° C, more preferably from 20 to 40 ° C.

In the present invention, the preparation and coating step of the PVA aqueous solution need not be continuous, and after the polyvinyl alcohol-based resin is dissolved in water, the generated PVA aqueous solution is once moved to a drum can or a storage container (container). In the container for transportation, the PVA aqueous solution is transported and supplied to the coating step. It is also possible to separate the apparatus (the dissolution apparatus) for dissolving the polyvinyl alcohol-based resin from the apparatus (coating apparatus) for coating the polyvinyl alcohol-based resin to the substrate, so that each device can be compacted. Implementation.

[Resin layer forming step (S10)]

Here, a resin layer (also referred to as a polyvinyl alcohol-based resin layer or a resin layer) made of a polyvinyl alcohol-based resin is formed on one surface of the base film.

The material suitable for the substrate film is as described in the description of the structure of the above polarizing laminate film. Further, in the present embodiment, the material of the polyvinyl alcohol-based resin suitable for forming the resin layer is as described in the description of the structure of the polarizing laminated film.

The resin layer of the polyvinyl alcohol-based resin is usually formed by coating an aqueous solution of a polyvinyl alcohol-based resin on one surface of a base film, and evaporating and drying a solvent such as water. In this way, a resin layer is formed, which can be formed into a thinner one. A method of coating an aqueous solution of a polyvinyl alcohol-based resin on a substrate film may be a roll coating method such as a wire bar coating method, a reverse coating method or a gravure coating method, a die coating method, or a corner coating method. A well-known method such as a comma coat method, a lip coat method, a spin coat method, a screen coating method, a fountain coat method, a dipping method, or a spray method is suitably selected. And adopted. A notch wheel coating method (knife coater), a die coating method, and a lip coating method are preferred. The drying temperature is, for example, 50 ° C to 200 ° C, preferably 60 ° C to 150 ° C. The drying time is, for example, 2 minutes to 20 minutes.

The thickness of the formed resin layer is usually in the range of more than 3 μm in consideration of the dyeability after stretching. When the thickness of the finally obtained polarizing plate layer is 10 μm or less, the thickness of the formed resin layer is usually 30 μm or less. The thickness of the formed resin layer is preferably from 5 μm to 20 μm.

Moreover, in order to improve the substrate film and the polyvinyl alcohol resin The adhesion of the layer may also provide an undercoat layer between the substrate film and the resin layer. From the viewpoint of adhesion, the undercoat layer is preferably formed of a composition containing a polyvinyl alcohol-based resin and a crosslinking agent.

[Extension step (S20)]

In the following description, the step of extending the laminated film of the polyvinyl alcohol-based resin layer in the base film thus obtained to obtain a stretched film will be described. The laminated film formed of the base film and the resin layer is uniaxially stretched so as to have a stretching ratio of more than 5 times with respect to the length before the step of extending the laminated film, thereby obtaining a stretched film. Preferably, the uniaxial stretching is performed so as to be more than 5 times and 8 times or less. When the stretching ratio is 5 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 cannot be sufficiently improved. On the other hand, when the stretching ratio is more than 8 times, the laminated film is likely to be broken at the time of stretching, and the thickness of the stretched film becomes thinner than the desired thickness, and the workability/handlerability of the subsequent step is lowered. The extension process of the extension step (S20) is not limited to a one-stage extension, and may be divided into multiple stages. When the multi-stage is carried out, the stretching treatment is performed in such a manner that the stretching ratio of all the stages of the elongation processing is more than 5 times.

In the extending step (S20) of the present embodiment, it is preferable to perform longitudinal stretching treatment for the longitudinal direction of the laminated film, and when such a degree of polarizing performance is not obtained, it is a lateral uniaxial stretching by a tenter method. It is also possible to have a fixed-end uniaxial extension represented by the same. Examples of the longitudinal stretching method include a method of extending between rolls, a method of compressing and stretching, a method of stretching using a tenter, and the like. The extension processing is not limited to the longitudinal extension processing, and may be Oblique extension processing, etc. Moreover, it is preferred that the free end is uniaxially extended.

Further, the stretching treatment may be either a wet stretching method or a dry stretching method, and a dry stretching method is preferred in that a wide range of temperatures at which the laminated film is stretched can be selected.

In the present embodiment, it is preferred to carry out the stretching treatment at a temperature ranging from -30 ° C to + 5 ° C of the base film. More preferably, the substrate film is stretched at a melting point of -25 ° C to a melting point of the substrate film. If the stretching temperature is lower than the melting point of the base film 11 by -30 ° C, it becomes difficult to extend at a high magnification of more than 5 times. When the elongation temperature exceeds the melting point of the base film by +5 ° C, it becomes difficult to extend because the base film is melted. Further, the stretching temperature is in the above range, and more preferably 120 ° C or more. This is because when the stretching temperature is 120 ° C or more, even if it is more than 5 times the stretching ratio, the elongation processing is not accompanied. The temperature adjustment of the elongation treatment is usually carried out by adjusting the temperature of the heating furnace.

[Staining step (S30)]

Hereinafter, a "dyeing step of forming a polarizer layer by dyeing a resin layer of the obtained stretched film with a dichroic dye" will be described. Here, the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye. Examples of the dichroic dye include iodine, an organic dye, and the like. Organic dyes can be used, 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 Fast Orange S, Fast Black, etc. These dichroic substances may be used singly or in combination of two or more.

The dyeing step is carried out, for example, by immersing the entire stretched film in a solution (staining solution) containing the above-mentioned dichroic dye. As the dyeing solution, a solution in which the above dichroic dye is dissolved in a solvent can be used. The solvent of the dyeing solution is generally water, and an organic solvent compatible with water may be further added. The concentration of the dichroic dye is preferably from 0.01% by weight to 10% by weight, more preferably from 0.02% by weight to 7% by weight, still more preferably from 0.025% by weight to 5% by weight.

When iodine is used as the dichroic dye, the dyeing efficiency can be further improved. Therefore, it is preferred to further add the iodide. Examples of the iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The proportion of the iodide added is preferably from 0.01% by weight to 20% by weight in the dyeing solution. Among the iodides, potassium iodide is preferably added. 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, and particularly preferably in the range of 1:7. The range of 1:70.

The time during which the stretched film is immersed in the dyeing solution is not particularly limited, and is usually preferably in the range of 15 seconds to 15 minutes, more preferably in the range of 1 minute to 3 minutes. Further, the temperature of the dyeing solution is preferably in the range of 10 ° C to 60 ° C, more preferably in the range of 20 ° C to 40 ° C. In the dyeing step, the remaining amount of the dyeing solution can also be washed away with pure water.

In the dyeing step, dyeing may be followed by cross-linking treatment. The crosslinking treatment can be carried out, for example, by immersing the stretched film in a solution (crosslinking solution) containing a crosslinking agent. A conventionally known substance can be used for the crosslinking agent. For example, a boron compound such as boric acid or borax, or glyoxal or glutaraldehyde can be mentioned. These may be used in a single type or in combination of two or more.

As the crosslinking solution, a solution in which a crosslinking agent is dissolved in a solvent can be used. The solvent may be, for example, water, or may further contain an organic solvent compatible with water. The concentration of the crosslinking agent of the crosslinking solution is not limited to the following, but is preferably in the range of 1% by weight to 20% by weight, more preferably 6% by weight to 15% by weight.

Iodide may also be added to the crosslinking solution. By adding an iodide, the in-plane polarization characteristics of the polyvinyl alcohol-based 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, cesium iodide, calcium iodide, tin iodide, and titanium iodide. The content of the iodide is usually from 0.05% by weight to 15% by weight, more preferably from 0.5% by weight to 8% by weight.

The time during which the stretched film is immersed in the crosslinking solution is usually from 15 seconds to 20 minutes, more preferably from 30 seconds to 15 minutes. Further, the temperature of the crosslinking solution is preferably in the range of 10 to 80 °C.

It is preferred to carry out the washing step and the drying step at the end. The washing step can be performed by washing with water. The water washing treatment can be usually carried out by immersing the stretched film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually from 3 ° C to 50 ° C, preferably from 4 ° C to 20 ° C. The immersion time is usually from 2 seconds to 300 seconds, preferably from 3 seconds to 240 seconds. bell.

In the washing step, a washing treatment by an iodide solution may be combined with a water washing treatment, or a solution in which a liquid alcohol such as methanol, ethanol, isopropanol, butanol or propanol is appropriately formulated may be used.

After the washing step, it is preferred to carry out the drying step. The drying step may be carried out by any suitable method (for example, natural drying, air drying, and heat drying). For example, the drying temperature at the time of heat drying is usually from 20 ° C to 95 ° C, and the drying time is usually from about 1 minute to 15 minutes. By the above dyeing step (S30), the polyvinyl alcohol-based resin layer can function as a polarizer. In the present specification, a polyvinyl alcohol-based resin layer having a function as a polarizer is referred to as a polarizer layer, and a laminate having a polarizer layer on a base film is referred to as a polarizing laminate film.

In the present embodiment, the polyvinyl alcohol-based resin layer is an aqueous solution of a polyvinyl alcohol-based resin having a degree of saponification of 99.0 mol% or less and defoamed under reduced pressure, and in the extending step (S20), it is more than 5 Since the stretching ratio is uniaxially stretched, a good dyeing speed can be maintained in the dyeing step (S30). Further, when a resin layer of a polyvinyl alcohol-based resin having a high degree of saponification is used, the dyeing speed in the dyeing step (S30) is lowered, and the dyeing tends to be insufficient.

[Structure of polarizing plate]

Fig. 2 is a schematic cross-sectional view showing an example of a basic layer structure of a polarizing plate of the present invention. The polarizing plate 13 is provided with a transparent protective film 14 and a polarizer layer 12 formed on the side of the transparent protective film 14. The polarizer layer 12 has a thickness of 10 μm or less and is formed of a polyvinyl alcohol-based resin in which a dichroic dye is adsorbed and oriented. The degree of saponification of the polyvinyl alcohol-based resin is 99.0 mol% or less.

In the polarizing plate 13, the transparent protective film 14 and the polarizer layer 12 are bonded together by, for example, an adhesive or an adhesive layer. Each structural element will be described in detail below.

[Transparent protective film]

The transparent protective film 14 may be a simple transparent protective film having no optical function, and may be a transparent protective film having an optical function while being a retardation film or a brightness enhancement film. The material of the transparent protective film 14 is not particularly limited, and examples thereof include a cellulose acetate-based resin film made of a cyclic polyolefin-based resin film, a cellulose triacetate, and a cellulose diacetate resin. a polyester resin film made of a resin of ethylene phthalate, polyethylene naphthalate or polybutylene terephthalate, a polycarbonate resin film, or a (meth)acrylic resin film. A polypropylene resin film or the like has been widely used in the field in the past.

As a cyclic polyolefin-based resin, a commercially available product can be suitably used, for example, Topas (registered trademark) (manufactured by Ticona Co., Ltd.), ARTON (registered trademark) (manufactured by JSR Co., Ltd.), and ZEONOR (registered trademark) (Japan) ZEONEX (registered trademark) (manufactured by Nippon Seon Co., Ltd.) and APEL (registered trademark) (manufactured by Mitsui Chemicals, Inc.). When such a cyclic polyolefin-based resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method can be suitably used. Furthermore, it is also possible to use a preformed film ring such as Escena (registered trademark) (made by Sekisui Chemical Co., Ltd.), SCA40 (made by Sekisui Chemical Co., Ltd.), ZEONOR (registered trademark) FILM (made by OPTES Co., Ltd.), etc. A commercially available product of a film made of a polyolefin resin.

The cyclic polyolefin resin film may also be uniaxially stretched or biaxially stretched. By extending, it is possible to impart an arbitrary retardation value to the cyclic polyolefin resin film. The stretching is generally performed while the film is unwound from the reel, and is extended in the heating furnace toward the direction in which the reel travels, in a direction perpendicular to the direction in which it travels, or in both directions. 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 magnification of the extension is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

Since the cyclic polyolefin resin film generally has a poor surface activity, it is preferably subjected to plasma treatment, corona discharge treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment on the surface adjacent to the polarizing film. Wait for surface treatment. Among them, it is more suitable to perform plasma treatment and corona discharge treatment which are easier to implement.

For the cellulose acetate-based resin film, a commercially available product can be suitably used, for example, FUJITAC (registered trademark) TD80 (manufactured by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by FUJIFILM Co., Ltd.), and FUJITAC (registered trademark) TD80UZ (manufactured by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD40UZ (manufactured by FUJIFILM Co., Ltd.), KC8UX2M (manufactured by Konica Minolta Opto Co., Ltd.), and KC4UY (manufactured by Konica Minolta Opto Co., Ltd.).

A liquid crystal layer or the like for improving the viewing angle characteristics may be formed on the surface of the cellulose acetate resin film. Further, in order to impart a phase difference, it may be an extended cellulose acetate resin film. The cellulose acetate resin film is usually subjected to a saponification treatment in order to improve the adhesion to the polarizing film. Saponification The treatment may be carried out by immersing in an aqueous alkaline solution such as sodium hydroxide or potassium hydroxide.

An optical layer such as a hard coat layer, an antiglare layer, or an antireflection layer may be formed on the surface of the transparent protective film 14 as described above. The method of forming the optical layers on the surface of the transparent protective film is not particularly limited, and a known method can be used.

When it is desired to satisfy the requirements for thinning, the thickness of the transparent protective film 14 is preferably as small as possible, preferably 88 μm or less, more preferably 48 μm or less. When the workability is considered, it is preferably 5 μm or more.

[Polarized film layer]

The polarizer layer 12 may have the same structure as the polarizer layer 12 of the polarizing laminate film 10.

[Adhesive layer]

The adhesive which can be used for bonding the transparent protective film 14 and the polarizer layer 12 is usually an isocyanate compound or a ring thereof by using an acrylic resin, a styrene resin, a polyoxymethylene resin or the like as a matrix polymer. A composition of a crosslinking agent such as an oxygen compound or an aziridine compound.

Further, fine particles may be contained as an adhesive layer for exhibiting light scattering.

The thickness of the adhesive layer is preferably from 1 μm to 40 μm in consideration of the properties of workability and durability. When the thickness of the adhesive layer is from 3 μm to 35 μm, it is more preferable because the dimensional change of the polarizing film can also be suppressed.

The method of bonding the transparent protective film 14 to the polarizer layer 12 by an adhesive may be applied to the polarizer layer 12 after the adhesive layer is provided on the surface of the transparent protective film 14, or may be on the polarizer layer 12. After the surface of the adhesive layer is provided, the transparent protective film 14 is bonded thereto.

The method of forming the pressure-sensitive adhesive layer is not particularly limited, and a solution containing each component mainly composed of the above-mentioned matrix polymer may be applied to the surface of the transparent protective film 14 or the surface of the polarizing plate layer 12, and dried to form an adhesive layer. The transparent protective film 14 and the polarizer layer 12 may be bonded to each other, and an adhesive layer may be formed on a separator, and then transferred and laminated on the surface of the transparent protective film 14 or the surface of the polarizer layer 12. Further, when the adhesive layer is formed on the surface of the transparent protective film 14 or the surface of the polarizer layer 12, it may be on the surface of the transparent protective film 14 or the surface of the polarizer layer 12 or the adhesive layer as needed. A close treatment is performed on one side or both sides, for example, performing a corona discharge treatment.

[adhesive layer]

The adhesive agent which can be used for bonding the transparent protective film 14 and the polarizer layer 12 is, for example, a water-based adhesive such as a polyvinyl alcohol resin aqueous solution or an aqueous two-liquid amine ester emulsion type adhesive. When a cellulose acetate film which is hydrophilized by a saponification treatment or the like is used as the transparent protective film 14, a water-based adhesive for bonding the polarizing plate layer 12 can be suitably used as a polyvinyl alcohol-based resin aqueous solution. In the case of using a polyvinyl alcohol-based resin as an adhesive, in addition to a vinyl alcohol homopolymer obtained by subjecting a polyvinyl acetate of a vinyl acetate homopolymer to saponification, vinyl acetate and A modified polyvinyl alcohol-based copolymer obtained by saponifying a copolymer of another monomer copolymerizable therewith, and further modifying the partial base group Polymers, etc. A polyvalent 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 to the aqueous binder. When such a water-based adhesive is used, the adhesive layer obtained by this method is usually 1 μm or less, and the adhesive layer is not actually observed even when the cross section is observed by a general optical microscope.

The method of bonding the polarizing plate layer 12 and the transparent protective film 14 with a water-based adhesive is not particularly limited, and for example, a coating agent is uniformly applied to the surface of the polarizing plate layer 12 and/or the transparent protective film 14 to be coated. A method in which another film is superposed on the surface and bonded and dried by a roller or the like. Usually, the adhesive is applied at a temperature of 15 to 40 ° C after its preparation, and the bonding temperature is usually in the range of 15 ° C to 30 ° C.

When the water-based adhesive is used, after the polarizer layer 12 and the transparent protective film 14 are bonded, the water contained in the water-based adhesive is dried. The temperature of the drying oven is preferably from 30 ° C to 90 ° C. If it is less than 30 ° C, the polarizing layer 12 and the adhesion surface of the transparent protective film 14 tend to be easily peeled off. If it is 90 ° C or more, there is a possibility that the optical performance is deteriorated due to heat. The drying time may be from 10 seconds to 1000 seconds, and particularly from the viewpoint of productivity, it is preferably from 60 seconds to 750 seconds, more preferably from 150 seconds to 600 seconds.

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

Moreover, as the laminated polarizer layer 12 and the transparent protective film For the 14 o'clock adhesive, a photocurable adhesive can also be used. The photocurable adhesive agent may, for example, be a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

The method of bonding the polarizing plate layer 12 and the transparent protective film 14 with a photocurable adhesive agent may, for example, be a flow cloth method, a Meyer bar coating method, a gravure coating method, or a notch wheel coating. Method for applying a bonding agent to the bonding surface of the polarizing plate layer 12 and/or the transparent protective film 14 by a doctor method, a doctor blade method, a die coating method, a dip coating method, a spray method, or the like, and superposing the two . In the flow distribution method, the polarizer layer 12 or the transparent protective film 14 of the object to be coated is moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction therebetween, and flows down and spreads over the surface. Method of the agent.

After the adhesive is applied to the surface of the polarizer layer 12 or the transparent protective film 14, the polarizer layer 12 and the transparent protective film 14 are bonded by a nip roll or the like via the adhesive application surface. . Further, it is also suitable for use in a state in which the polarizer layer 12 and the transparent protective film 14 are overlapped, and after the adhesive is dropped between the polarizer layer 12 and the transparent protective film 14, the laminate is uniformly pressed by a roller or the like to be uniformly added. The method of rolling exhibition. At this time, the material of the roller can be metal or rubber. Further, it is also preferred to use a method in which an adhesive is dropped between the polarizer layer 12 and the transparent protective film 14, and the laminate is passed between a roll and a roll to be pressed and stretched. At this time, the rollers may be of the same material or different materials. The thickness of the adhesive layer after lamination using the above nip rolls or the like is preferably from 0.01 μm to 5 μm.

In the adhesion surface of the polarizer layer 12 and/or the transparent protective film 14, in order to improve the adhesion, plasma treatment and corona discharge may be suitably performed. Surface treatment such as electric treatment, ultraviolet irradiation treatment, flame treatment, and saponification treatment. The saponification treatment may, for example, be a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

When a photocurable resin is used as the adhesive, the photocurable adhesive is cured by irradiating the active energy ray after bonding the polarizer layer 12 and the transparent protective film 14. The light source of the active energy ray is not particularly limited, but an active energy ray having a light-emitting distribution of a wavelength of 400 nm or less is preferable. Specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and an ultrahigh pressure can be preferably used. Mercury lamps, chemical lamps, black-light lamps, microwave-activated mercury lamps, metal halide lamps, and the like.

The light intensity of the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive, and is not particularly limited, and the irradiation intensity in the wavelength range effective for activation of the polymerization initiator is preferably from 0.1 to 6000 mW/cm. ² . When the irradiation intensity is 0.1 mW/cm ² or more, the reaction time does not become too long, and when it is 6000 mW/cm ² or less, the heat generated by the light source and the heat generated by curing of the photocurable adhesive are generated. There are fewer doubts about the yellowing or deterioration of the polarizing film. The light-time of the photocurable adhesive is not particularly limited as long as it is suitable for the photocurable adhesive to be cured, but the integrated light amount expressed by the product of the irradiation intensity and the irradiation time is preferably It is set to be 10 to 10000 mJ/cm ² . When the integrated light amount of the photocurable adhesive is 10 mJ/cm ² or more, a sufficient amount of the active species derived from the polymerization initiator can be generated, and the curing reaction can be more reliably performed, and when the amount is 10000 mJ/cm ² or less, the irradiation time is It will not become too long and will maintain good productivity. Further, the thickness of the adhesive layer after the active energy ray irradiation is usually about 0.001 μm to 5 μm, preferably 0.01 μm to 2 μm, more preferably 0.01 μm to 1 μm.

When the photocurable adhesive is cured by irradiation with an active energy ray, the functions of the polarizing plate such as the degree of polarization, the transmittance and the hue of the polarizer layer 12, and the transparency of the transparent protective film 14 are preferably not lowered. Hardening under the conditions.

[other optical layers]

The polarizing plate of the present invention produced in the above manner can be used as a polarizing plate in which other optical layers are laminated in actual use. Moreover, the transparent protective film 14 may also have the function of the optical layers. Examples of other optical layers include a reflective polarizing film that can penetrate certain polarized light and reflect polarized light having a property opposite to the polarized light, and an anti-glare film having an uneven shape on the surface, and A film having a surface anti-reflection function, a reflective film having a reflective function on the surface, a transflective film having a reflection function and a penetrating function, and a viewing angle compensation film.

A commercially available product of a reflective polarizing film that is capable of penetrating a certain kind of polarized light and reflecting a polarized light having a property opposite to the polarized light, for example, DBEF (manufactured by Sumitomo 3M Co., Ltd., manufactured by 3M Company) , APF (made by 3M company, available from Sumitomo 3M Co., Ltd.). The viewing angle compensation film may be an optical compensation film coated with a liquid crystal compound on the surface of the substrate, a retardation film made of a polycarbonate resin, or a retardation film made of a cyclic polyolefin resin. . A commercially available product of an optical compensation film which is coated with a liquid crystal compound and which is coated with a liquid crystal compound is exemplified by a WV film (manufactured by FUJIFILM Co., Ltd.) and an NH film (New Japan). NR film (manufactured by Nippon Oil Co., Ltd.), etc. In addition, commercially available products of a retardation film made of a cyclic polyolefin resin include ARTON (registered trademark) film (manufactured by JSR Co., Ltd.) and Escena (registered trademark) (Suizu Chemical Industry Co., Ltd.) Company system), ZEONOR (registered trademark) FILM (made by OPTES Co., Ltd.), etc.

[Method of Manufacturing Polarized Laminated Film]

Fig. 3 is a flow chart showing an embodiment of a method of manufacturing the polarizing laminated film 10 shown in Fig. 1. According to this, the manufacturing method of the polarizing laminated film 10 is a resin layer forming step (S10) which forms a saponification degree of 99.0 mol% or less on one surface of the base film 11 by the following steps. a polyvinyl alcohol-based resin layer which is defoamed under reduced pressure to form a laminated film; and an extending step (S20) of performing a uniaxial stretching treatment on the laminated film at a stretching ratio of more than 5 times to form a stretching film; and a dyeing step (S30) The resin layer is dyed with a dichroic dye to obtain a polarizing laminate film 10 as the polarizer layer 12.

The polarizing laminated film 10 obtained by the above-described production method is a polarizing laminated film 10 having a polarizing plate layer 12 having a thickness of 10 μm or less on the stretched base film 11. The polarizing laminate film 10 can be used as a polarizing plate as it is, or can be used as an intermediate product for transferring the polarizing plate layer 12 to a transparent protective film as will be described later.

The illuminance factor of the obtained polarizer corrects the monomer transmittance (Ty), which is usually 40% or more, and the luminescence factor corrected polarization (Py) is usually 99.9% or more. Preferably, Ty is 41.0% or more, and Py is 99.9% or more. More preferably, the Ty is 42.5% or more, and the Py is 99.9% or more.

The illuminance factor correction monomer transmittance (Ty) of the polarizer and the luminescence factor correction degree of polarization (Py) were measured by a spectrophotometer (V7100, manufactured by JASCO Corporation) equipped with an integrating sphere. The MD transmittance and the TD transmittance are obtained in the range of 380 nm to 780 nm, and the monomer transmittance and the polarization degree of each wavelength are calculated according to the formulas (1) and (2), and further by JIS Z 8701-2 The illuminance factor is corrected by the degree of view (°C light source), and the illuminance factor corrected monomer transmittance (Ty) and the luminescence factor corrected polarization (Py) are obtained. The "MD penetration rate" is the transmittance when the direction of the polarized light emitted by the Glan-Thompson prism is parallel to the transmission axis of the polarizing plate sample, in the formula (1), In the formula (2), it is represented by "MD". Moreover, the "TD penetration rate" is the transmittance when the direction of the polarized light emitted by the Glan-Thomson(R) perpendicularly intersects the transmission axis of the polarizing plate sample, in the equations (1) and (2). It is expressed as "TD".

Monomer penetration rate (%) = (MD + TD) / 2 (1)

Polarization (%) = {(MD-TD) / (MD + TD)} 1/2 × 100 (2)

[Method of Manufacturing Polarizing Plate]

Fig. 4 is a flow chart showing an embodiment of a method of manufacturing the polarizing plate 13 shown in Fig. 2. Accordingly, the manufacturing method of the polarizing plate 13 is carried out in the following steps: a resin layer forming step (S10) which forms a saponification degree of 99.0 mol% or less on one surface of the substrate film, and defoaming under reduced pressure. a resin layer made of a polyvinyl alcohol-based resin to form a laminated film; and an extending step (S20) of performing a uniaxial stretching treatment on the laminated film at a stretching ratio of more than 5 times to form a stretching film; and a dyeing step (S30) ), which is dyed with dichroic pigment The polarizing laminated film as the polarizing plate layer 12 is obtained. Thereafter, the bonding step (S40) is applied to the surface of the polarizing layer 12 of the polarizing laminated film on the side of the base film 11 The transparent protective film 14 is bonded to the surface on the opposite side to obtain a multilayer film. In the peeling step (S50), the substrate film 11 is peeled off from the multilayer film.

The polarizing plate 13 obtained by the above-described manufacturing method is a polarizing plate 13 having a polarizing plate layer 12 having a thickness of 10 μm or less on the transparent protective film 14. Such a polarizing plate 13 can be used, for example, by bonding it to another optical film, a liquid crystal cell, etc. via a pressure-sensitive adhesive.

The respective steps of S40 to S50 of Fig. 4 will be described in detail below. Further, the steps S10 to S30 in Fig. 4 are the same as the steps in steps S10 to S30 in Fig. 3.

[Finishing step (S40)]

Here, the transparent protective film is bonded to the surface on the opposite side to the surface on the base film side of the polarizer layer to obtain a multilayer film. The method of bonding the transparent protective film includes a method of bonding the polarizer layer 12 and the transparent protective film 14 with an adhesive, and a method of bonding the surface of the polarizer layer 12 and the transparent protective film 14 with an adhesive. A material suitable as a transparent protective film is as described in the description of the structure of the above polarizing plate. The adhesive to be used, the material of the adhesive, and the preferred method of bonding the polarizer layer 12 and the transparent protective film 14 are as described in the structure of the above polarizing plate.

[Peeling step (S50)]

As shown in FIG. 4, the method for producing a polarizing plate of the present embodiment is after the bonding step (S40) of bonding the transparent protective film to the polarizing plate layer 12, The substrate film peeling step (S50) is further performed. In the peeling step (S50) of the base film, the base film is peeled off from the multilayer film. The peeling method of the base film is not particularly limited, and it can be peeled off in the same manner as the peeling step of the release film which is usually performed on the polarizing plate with the adhesive. After the bonding step (S40) of the transparent protective film, the film may be peeled off immediately, or may be separately wound into a roll shape, and then separately provided with a peeling step to be peeled off.

The present invention will be further illustrated by the following examples and comparative examples, but the invention is not limited to the examples.

(Example)

[Example 1]

(1) Fabrication of substrate film

A base film is produced by co-extrusion molding using a multilayer extrusion molding machine: a random copolymer of propylene/ethylene containing about 5 wt% of ethylene units (manufactured by Sumitomo Chemical Co., Ltd.) The "People's NOBLEN FLX80E4" made by Sumitomo Chemical Co., Ltd., "Minister NOBLENFLX80E4" made by Sumitomo Chemical Co., Ltd., has a fusion point of Tm = 163 °C. A long-length base film having a three-layer structure of a resin layer formed. The total thickness of the base film was 100 μm, and the thickness ratio of each layer (FLX80E4/W151/FLX80E4) was 3/4/3.

(2) Modulation of coating liquid

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in hot water at 95 ° C to prepare a polyethylene having a concentration of 3% by weight. An aqueous alcohol solution. In the obtained aqueous solution, 1 part by weight relative to the polyvinyl alcohol powder A cross-linking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was mixed in a ratio of parts by weight to obtain a coating liquid for forming an undercoat layer.

The obtained undercoat layer forming coating liquid was transferred to a 30 L (liter) stainless steel container and transferred to a coating apparatus.

Further, polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average polymerization degree 2400, average saponification degree: 98.0 to 99.0 mol%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 8 wt%. This aqueous solution is used as a coating liquid for forming a polyvinyl alcohol-based resin layer.

The obtained coating liquid for forming a polyvinyl alcohol-based resin layer was transferred to a stainless steel container of 30 L, and transferred to a coating apparatus.

(3) Implementing vacuum degassing

The coating liquid for forming a polyvinyl alcohol-based resin layer prepared in (2) was placed in a treatment container, and treated at -0.04 MPa (measured pressure) for 120 minutes. At this point the container is continuously inhaled. The liquid temperature after the defoaming treatment was heated at about 26.0 ° C, and was applied for coating without cooling.

(4) Formation of undercoat layer and polyvinyl alcohol-based resin layer

While continuously transporting the base film produced in the above (1), a corona discharge treatment is performed on one surface of the base film, and the corona discharge treated surface is continuously coated on the surface using the micro gravure coater. (2) A coating liquid for forming an undercoat layer was formed and dried at 60 ° C for 3 minutes, thereby forming an undercoat layer having a thickness of 0.2 μm. Then, while the film is being conveyed, the coating liquid is continuously applied to the undercoat layer by using the notch wheel coater in which the coating liquid for forming a polyvinyl alcohol-based resin layer is applied to the coating head. Drying at 90 ° C for 1 minute, drying at 70 ° C for 3 minutes, followed by drying at 60 ° C for 4 minutes, thereby applying to the primer A polyvinyl alcohol-based resin layer having a thickness of 11.0 μm was formed on the layer.

Further, the same treatment as described above is performed on the surface of the base film opposite to the surface on which the polyvinyl alcohol-based resin layer is formed, and the undercoat layer and the polyvinyl alcohol-based resin layer are sequentially formed to form on both surfaces of the base film. An undercoat layer having a thickness of 0.2 μm and a polyvinyl alcohol-based resin layer having a thickness of 11.0 μm were used to obtain a layer structure of a polyvinyl alcohol-based resin layer/primer coat layer/base film/undercoat layer/polyvinyl alcohol-based resin layer. A laminated film.

(5) Extension of laminated film

The laminated film obtained in the above (4) was continuously conveyed, and the free end uniaxially stretched at a magnification of 5.5 times in the longitudinal direction (film transport direction) at an elongation temperature of 160 ° C while extending between the nip rolls. Stretch film. The thickness of the polyvinyl alcohol-based resin layer of the stretched film was 5.5 μm and the other was 5.9 μm.

(6) Production of polarizing laminated film

While continuously transporting the stretched film produced in the above (5), it was immersed in a warm water bath at 60 ° C for a residence time of 60 seconds, and then immersed in iodine and potassium iodide so as to have a residence time of about 150 seconds. In the dyeing solution at 30 ° C, the polyvinyl alcohol-based resin layer was subjected to a dyeing treatment, and then the remaining amount of the dyeing solution was washed away with pure water at 10 ° C. Then, the mixture was immersed in a crosslinking solution containing boric acid and potassium iodide at 76 ° C for a residence time of 600 seconds to carry out a crosslinking treatment. Thereafter, the film was washed with pure water at 10 ° C for 4 seconds and dried at 80 ° C for 300 seconds to prepare a polarizing laminated film.

In the obtained polarizing laminate film, the thickness of the polarizer laminated on both surfaces of the substrate was 5.8 μm and 6.0 μm, respectively.

(7) Observing the gap of 100 μm or more in length

A polarizing plate layer having a thickness of 6.0 μm in the obtained polarizing laminate film was peeled off to form a single-layer film formed of a base film and a polarizing plate layer having a thickness of 5.8 μm.

The obtained single-area layer film was cut into a size of 300 mm in the absorption axis direction and 200 mm in the direction perpendicular to the absorption axis, and visually observed on a planar light source using a magnifying glass having a magnification of 10 times. In total, 20 sheets (1.2 m ² ) of the laminated film were confirmed, and there were eight voids having a length in the absorption axis direction of 100 μm or more, and the number per unit area was 6.7 pieces/m ² .

The obtained single-area layer film (single-area film formed of a base film and a polarizing plate layer having a thickness of 5.8 μm) was measured at a wavelength of 380 nm by a spectrophotometer (V7100, manufactured by JASCO Corporation). The MD transmittance and the TD transmittance in the range of 780 nm, the monomer transmittance and the polarization degree of each wavelength are calculated according to the above formulas (1) and (2), and further according to the 2 degree field of view of JIS Z 8701 (°C light source) The illuminance factor correction is performed, and the illuminance factor correction monomer transmittance (Ty) and the luminescence factor correction polarization degree (Py) are obtained, and are Ty: 42.9% and Py: 99.92%.

(8) Production of polarizing plate

Polyvinyl alcohol powder ("KL-318" manufactured by Kuraray Co., Ltd., average polymerization degree: 1800) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol aqueous solution having a concentration of 3 wt%. A crosslinking agent ("Sumirez Resin 650" manufactured by Tajika Chemical Industry Co., Ltd.) was added as a binder aqueous solution in an amount of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder.

Then, the polarizing laminated film produced in the above (6) is continuously conveyed, and the aqueous solution of the adhesive is applied onto the polarizing plate layers on both surfaces, and then bonded to the polarizing plate layer and saponified on the bonding surface. Transparent protective film [transparent protective film made of cellulose triacetate (TAC) ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd.), thickness 40 μm], pressed by a pair of bonding rolls, A bonded film made of a layer structure of TAC/polarized sheet/primer/base film/undercoat/polarizer layer/TAC was produced.

Then, the split film is peeled off at the interface between the base film and the undercoat layer to obtain a film formed of a TAC/polarized sheet layer (5.8 μm)/primer coat layer/base film and an undercoat layer/polarized sheet layer. After the polarizing plate (6.0 μm)/TAC was formed, the substrate film was further removed by the film peeling of the former to obtain another polarizing plate. In the step of peeling off the substrate film, defects such as cracking of the film did not occur.

(8) Adhesive layering step

The surface of the undercoat layer side of the polarizing plate having a thickness of 5.8 μm of the obtained polarizing plate layer was subjected to corona discharge treatment, and a PET film (separating film) subjected to release treatment was attached with an acrylic adhesive having a thickness of 25 μm. A sheet-like adhesive of the agent is formed into a polarizing plate with an adhesive formed by "separating film/adhesive/undercoat/polarizing sheet/TAC".

(9) Preparation of the evaluation sample

The obtained polarizing plate with an adhesive was cut into a size of 60 mm × 60 mm so that the absorption axis was 0° with respect to the side, and the separation film was peeled off, and the adhesive surface was bonded to the glass. This was used as an evaluation sample.

(10) Thermal flushing test (HS test)

Place 24 evaluation samples in the test cell and repeat at -40 ° C for 30 minutes The clock was cycled 400 times at 85 ° C for 30 minutes to cause cracks in the absorption axis direction of the polarizer.

(11) Observing the voids in the fracture

An optical microscope (VHX-500 manufactured by KEYENCE Co., Ltd.) was used to observe the generated cracks in a penetrating manner, and it was observed that among the generated cracks, there appeared to be microbubbles (microbubbles) in one crack. This is caused by a small gap of less than 100 μm in the direction of the absorption axis. The minute voids are extremely small in the thickness direction below the thickness of the polarizer, and are embedded in the polarizer layer unlike the voids caused by the bubbles. Therefore, such minute bubbles are difficult to find and observe by ordinary visual observation or microscope, but can be observed in the crack as described above, and can be regarded as being found by cracks.

The size of such a minute gap is less than 100 μm in the direction of the absorption axis, and a cross section in which the minute gap portion is cut perpendicularly from the center in the absorption axis direction is observed, and the length in the thickness direction is about 3 μm.

[Embodiment 2]

An evaluation was carried out in the same manner as in Example 1 except that the measurement pressure of the reduced pressure treatment in (3) of Example 1 was set to -0.09 MPa. The liquid temperature after the treatment was 24.7 °C. The obtained liquid system after the defoaming treatment was used for coating without performing operations such as heating and cooling.

The thickness of the polarizer layer evaluated at this time was 5.2 μm. The sample prepared from the single-area layer film was confirmed to have a length of 100 μm or more in the absorption axis direction, and the number of voids was one, and the number of voids per unit area was 0.83 / m ² .

Among the cracks generated in the HS test, one of the aforementioned minute voids was observed in the crack.

The luminescence factor correction monomer transmittance (Ty) and luminescence factor correction polarization (Py) of the single-area film were Ty: 42.5%, Py: 99.93%.

[Comparative Example 1]

When the vacuum degassing treatment of (3) of Example 1 was not carried out, when the polarizing laminated film was formed in the same manner, the thickness of the polarizing layer on one side was 5.8 μm, and the thickness of the polarizing layer on the other side was 5.1 μm.

At this time, the surface of the surface having a thickness of 5.8 μm having a length in the longitudinal direction of 100 μm or more was 44 pieces/m ² .

For the surface having a thickness of 5.8 μm, an evaluation sample was prepared and evaluated in the same manner as in Example 1, and among the cracks generated by the thermal flushing test (HS test), the observed main cause of the crack was observed in the crack. The tiny gaps are 14.

Void: the number of voids having a length in the absorption axis direction of 100 μm or more (pieces/m ² )

Thermal rush test: the number of cracks in the observed cracks in the direction of the absorption axis that are less than 100 μm.

(industrial availability)

According to the production method of the present invention, it is possible to produce a polarizer having a small number of bubble defects and reducing the risk of occurrence of cracks, and a polarizing laminate including the polarizer and a polarizing plate. The polarizing plate including the polarizer is less likely to be derived from microbubbles remaining in the polyvinyl alcohol-based resin layer even if it is subjected to a thermal flushing test in consideration of a temperature change when it is used in a liquid crystal display device. A crack caused by a void (microbubble).

The first item of the patent application scope of the present application is a polarizer. However, the pattern of the present invention is a polarizing laminated film containing the polarizer of the present invention, a sectional view of the basic layer structure of the polarizing plate, and a manufacturing flow chart, which are not sufficient to represent the technical features of the present invention.

Claims (8)

A polarizing plate comprising a polyvinyl alcohol-based resin, and having a length of 100 μm or more in the absorption axis direction is 10 pieces/m ² or less. The polarizer according to claim 1, wherein the polarizer has a thickness of 10 μm or less. A polarizing laminate film comprising the polarizer described in claim 1 or 2 on at least one side of a substrate film. A polarizing plate which is laminated on at least one side of a polarizer according to claim 1 or 2, and a transparent protective film. A method for producing a polarizing laminate film in which a polarizer layer made of a polyvinyl alcohol-based resin is formed on at least one surface of a base film, and a length of the polarizer layer in the absorption axis direction is formed. The method for producing a polarizing laminated film having a void of 100 μm or more of 10 pieces/m ² or less, wherein the production method includes the step of coating the surface of at least one side of the base film with polyvinyl alcohol which has been defoamed under reduced pressure. The aqueous solution of the resin obtains a step of forming a laminated film of a resin layer composed of a polyvinyl alcohol-based resin on at least one side of the base film; a step of extending the laminated film to obtain a stretched film; and a dichroic dye The step of dyeing the aforementioned resin layer of the stretched film to form a polarizer layer. The method for producing a polarizing laminate film according to the fifth aspect of the invention, wherein the thickness of the polarizer layer composed of a polyvinyl alcohol-based resin It is 10 μm or less. The method for producing a polarizing laminated film according to the fifth or sixth aspect of the invention, wherein the aqueous solution of the polyvinyl alcohol-based resin defoamed under reduced pressure is reduced to -0.04 MPa (measured by a pressure) The following is an aqueous solution of the polyvinyl alcohol-based resin obtained by defoaming. A method of producing a polarizing plate, comprising the step of: a polarizer layer of the polarizing laminate film according to any one of claims 5 to 7 on the opposite side of the substrate film side; The transparent protective film is bonded to the surface to obtain a lamination step of the multilayer film; and the peeling step of peeling off the substrate film from the multilayer film.