JP5979123B2 - Polarizer with few bubble defects - Google Patents

Description

The present invention relates to a polarizer with few bubble defects and a method for manufacturing the same.

In recent years, as an optical element of a liquid crystal display device, a polarizing plate has been incorporated and widely used 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 these liquid crystal display devices, thin polarizing plates have been developed. So far, a method has been proposed in which a polyvinyl alcohol resin layer is provided on the surface of a base film using an aqueous solution of a polyvinyl alcohol resin, and then stretched and then dyed to produce a polarizer and a polarizing plate ( Patent Documents 1 and 2).

JP 2000-338329 A JP 2009-93074 A

The polarizer and the polarizing plate are produced from an aqueous solution of a polyvinyl alcohol-based resin. In the step of preparing the aqueous solution, polyvinyl alcohol is easy to bite bubbles, and is formed when a polyvinyl alcohol-based resin layer is formed. The present invention has found that voids due to circular concave defects caused by bubbles and elliptical or linear bubble defects generated in the extending direction of the resin layer after stretching are generated on the surface of the resin layer. This inventor provides the polarizer with few voids resulting from this bubble defect, the polarizing laminated film which consists of this polarizer, and its manufacturing method.

The present invention provides a polarizer comprising a polyvinyl alcohol-based resin having a length of 100 μm or more in the absorption axis direction and 10 or less m ² / m ² . The present invention also provides a polarizing laminate film in which such a polarizer is laminated on at least one surface of a substrate film, and a polarizing plate in which a transparent protective film is laminated on at least one surface of the polarizer.

A polarizing laminate in which the length in the absorption axis direction of the polarizer is 10 μm / m ² or less with a gap of 100 μm or more is typically obtained by a manufacturing method including the following steps (a) to (c): Produced.
(A) A laminate in which a polyvinyl alcohol resin aqueous solution degassed under reduced pressure is applied to at least one surface of a substrate film, and a resin layer made of a polyvinyl alcohol resin is formed on at least one surface of the substrate film A resin layer forming step of obtaining a film;
(A) a stretching step of stretching the laminated film to obtain a stretched film;
(C) A dyeing step in which a polyvinyl alcohol resin layer of a stretched film is dyed with a dichroic dye to form a polarizer layer.

The present invention includes a step of laminating a transparent protective film on the surface opposite to the base film side of the polarizer layer of the polarizing laminate film to obtain a multilayer film (bonding step),
The manufacturing method of the polarizing plate in which the transparent protective film was provided in the single side | surface of a polarizer including the process (peeling process) of peeling a base film from a multilayer film is provided.

  According to the present invention, when producing a polarizer, an aqueous solution of a polyvinyl alcohol resin is depressurized and degassed to coat the substrate film with the aqueous solution of the polyvinyl alcohol resin as a coating liquid. When forming a resin layer, the bubble in a coating liquid bursts and the production | generation of a circular concave defect can be reduced in a coating coating layer. As a result, a polarizer in which generation of elliptical or linear voids caused by bubble defects generated in the stretching direction is suppressed even when a laminate comprising a base film after coating and a polyvinyl alcohol resin layer is stretched And a polarizing laminate comprising such a polarizer.

It is a schematic sectional drawing which shows an example of the fundamental layer structure of the light-polarizing laminated film which concerns on this invention. It is a schematic sectional drawing which shows an example of the fundamental layer structure of the polarizing plate which concerns on this invention. It is a flowchart which shows one Embodiment of the manufacturing method of the light-polarizing laminated film shown in FIG. It is a flowchart which shows one Embodiment of the manufacturing method of the polarizing plate shown in FIG.

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

<Configuration of polarizing laminated film>
FIG. 1 is a schematic cross-sectional view showing an example of a basic layer configuration of a polarizing laminate film according to the present invention. The polarizing laminated 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 from a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented.

Hereinafter, each component will be described in detail.

[Base film]
As a material of the base film 11, for example, a thermoplastic resin excellent in transparency, mechanical strength, thermal stability, stretchability, and the like is used. Specific examples of such thermoplastic resins include cellulose ester resins such as cellulose triacetate, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins. , (Meth) acrylic resins, cyclic polyolefin resins (norbornene resins), polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.
The material for the base film preferably includes at least one selected from the group consisting of cellulose ester resins, polyolefin resins, cyclic polyolefin resins, and (meth) acrylic resins.

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.
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.

Examples of the polyolefin resin include polyethylene and polypropylene. When a base film made of polypropylene is used, it is preferable because it can be stably stretched at a high magnification. As the cyclic polyolefin resin, a norbornene resin is preferably used.
Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefin as a polymerization unit, and is described in, for example, 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, C1-6 alkyl poly (meth) acrylates, such as poly (meth) acrylate methyl, are mentioned. 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.

  Arbitrary appropriate additives may be added to the base film 11 in addition to the 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 base film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97%. % By weight. This is because, if the content of the thermoplastic resin in the base film is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  Although the thickness of the base film 11 can be determined as appropriate, it is generally preferably 1 to 500 μm, more preferably 1 to 300 μm, and further preferably 5 to 200 μm from the viewpoint of workability such as strength and handleability. The thickness of the base film 11 is most preferably 5 to 150 μm.

The base film preferably has a melting point of 110 ° C. or higher so that the base film can be stretched in a temperature range suitable for stretching the polyvinyl alcohol resin. Preferably, those having a melting point of 130 ° C. or higher are used. If the melting point of the base film is less than 110 ° C., the base film is likely to melt in the stretching step (S20) described later, and the stretching temperature cannot be raised sufficiently, making stretching more than 5 times difficult. It is. The melting point of the base film is a value measured at a heating rate of 10 ° C./min based on ISO3146.

  The base film 11 may be subjected to corona treatment, plasma treatment, flame treatment, or the like on at least the surface on which the polarizer layer 12 is formed in order to improve the adhesion with the polarizer layer 12. Moreover, in order to improve adhesiveness, you may form thin layers, such as a primer layer, in the surface at the side in which the polarizer layer 12 of the base film 11 is formed.

[Polarizer layer]
The polarizer of the present invention is a polarizer made of a polyvinyl alcohol-based resin having a length of 100 μm or more in the absorption axis direction and 10 pores / m ² or less. The thickness of the polarizer can be 10 μm or less, and can be further reduced to 7 μm or less. A thin polarizing laminated film in which the thickness of the polarizer layer 12 is 10 μm or less can be manufactured.

Specifically, the polarizer layer 12 is obtained by adsorbing and orienting a dichroic dye on a uniaxially stretched polyvinyl alcohol-based resin layer. As the polyvinyl alcohol resin, a saponified polyvinyl acetate resin can be used. Examples of the polyvinyl acetate resin include polyvinyl acetate, which is a homopolymer of vinyl acetate, and copolymers with other monomers copolymerizable with vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol-based resin is 99.0 mol% or less. In the present invention, a polyvinyl alcohol resin having a saponification degree of 99.0 mol% or less can maintain a constant dyeing speed even when uniaxial stretching is performed more than 5 times, so that a thin polarizing laminate having high polarization performance There is an advantage that the film can be produced efficiently. On the other hand, when a polyvinyl alcohol-based resin having a saponification degree exceeding 99.0 mol% is used, the dyeing speed is remarkably slow, and a polarizing laminated film having sufficient polarization performance may not be obtained. In some cases, the production takes several times longer than usual.

  The saponification degree of the polyvinyl alcohol-based resin is preferably 90 mol% or more, and more preferably 94 mol% or more. If the saponification degree is less than 90 mol%, strength such as water resistance may not be sufficient.

  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. The polyvinyl alcohol resin used in the present invention is not particularly limited as long as the saponification degree is 99.0 mol% or less, and may be modified polyvinyl alcohol partially modified. For example, polyvinyl alcohol-based 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, etc. . The average degree of polymerization of the polyvinyl alcohol-based resin is not particularly limited, but is preferably 100 to 10,000, and more preferably 1500 to 10,000.

  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: 95.0-96.0 mol%) and PVA617 (degree of saponification: 94.5-95.5 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, JF-17 (degree of saponification: 98.0 to 99.0 mol) of Nippon Vinegar Pival Co., Ltd. %), JF-17L (degree of saponification: 98.0 to 99.0 mol%) and F-20 (saponification degree: 98.0 to 99.0 mol%), and the like.

  What coated this polyvinyl alcohol-type resin on the base material, and formed the resin layer can be used for manufacture of the polarizer layer 12 concerning this invention. The method for forming the resin layer of the polyvinyl alcohol resin is that a polarizer layer 12 having a desired thickness is easily obtained, and a resin layer is formed by applying a solution of the polyvinyl alcohol resin on the base film 11. The method is preferred. The polarizer layer 12 is preferably uniaxially stretched at a stretch ratio of more than 5 times, more preferably more than 5 times and not more than 8 times.

Polarizing property in which a polarizer layer made of a polyvinyl alcohol-based resin is formed on at least one surface of the base film, and the length of the polarizer layer in the absorption axis direction is 10 μm / m ² or less. The manufacturing method of a laminated body is demonstrated below.

An aqueous solution of polyvinyl alcohol resin depressurized under reduced pressure is applied to at least one surface of the base film to obtain a laminated film in which a resin layer made of polyvinyl alcohol resin is formed on at least one surface of the base film The resin layer forming step will be described.

The aqueous solution of the polyvinyl alcohol-based resin applied to the base film usually contains 4 wt% to 10 wt% of polyvinyl alcohol, and preferably 6 wt% to 9 wt%. If it is 4 wt% or less, the amount of heat required for drying is required, and it is necessary to reduce the line speed, which is not preferable because productivity deteriorates. If it is 10 wt% or more, gelation tends to occur and storage properties deteriorate, such being undesirable. As a polyvinyl alcohol-type resin, what was illustrated in description about a polarizer is used.

As the aqueous solution of the polyvinyl alcohol-based resin, an aqueous solution of the defoamed polyvinyl alcohol-based resin is preferable, and as the method of defoaming, defoaming by reduced pressure is preferable because of the good removal efficiency of bubbles. PVA aqueous solution is very easy to foam, and the generated foam is difficult to break, so that the foam generated by foaming is not mixed again in the liquid even under reduced pressure, and the pressure is reduced in a stationary state, and the reduced pressure state is maintained. More preferable is a method of waiting for bubbles to be removed from the aqueous solution.

In the defoaming step of the present invention, a depressurization method of sucking with a vacuum pump is used. There is no particular designation as a defoaming container, and any container that can withstand reduced pressure can be used.
In general, reducing the pressure in the container (gauge pressure) as low as possible is preferable because the processing time is shortened. The pressure (gauge 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 still more 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 longer, but may be increased as long as productivity is not impaired.

When coating a defoamed polyvinyl alcohol resin aqueous solution (also referred to as PVA aqueous solution or coating solution), the temperature of the coating solution to be fed is such that the coating solution is in contact with the substrate during coating. In order to prevent the base material from sagging and to affect the film thickness accuracy of the formed polyvinyl alcohol-based resin layer, the upper limit may be set, while the lower limit may be set so that gelation of the PVA aqueous solution does not occur. The temperature of a coating liquid is 10-80 degreeC normally, Preferably it is 15-60 degreeC, More preferably, it is 20-40 degreeC.

  In the present invention, the production and coating process of the PVA aqueous solution need not be continuous. After the polyvinyl alcohol resin is dissolved in water, the resulting PVA aqueous solution is once transferred to a transport container such as a drum can or a container. The PVA aqueous solution may be conveyed and supplied to the coating process. In this way, the equipment can be made compact by separating the equipment for dissolving the polyvinyl alcohol resin (dissolution equipment) and the equipment for applying the polyvinyl alcohol resin to the base material (coating equipment). it can.

[Resin Layer Forming Step (S10)]
Here, a resin layer made of a polyvinyl alcohol-based resin is formed on one surface of the base film.

  Suitable materials for the base film are as described above in the description of the constitution of the polarizing laminated film. In addition, in this embodiment, the material of the polyvinyl alcohol-type resin suitable for forming the resin layer is as described in the explanation of the configuration of the polarizing laminated film.

The resin layer of the polyvinyl alcohol resin is usually formed by applying a coating liquid composed of an aqueous solution of the polyvinyl alcohol resin on one surface of the base film, evaporating a solvent such as water and drying. The 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 comma coat method (knife coater), a die coat method and a lip coat method are preferred. A drying temperature is 50 degreeC-200 degreeC, for example, Preferably it is 60 degreeC-150 degreeC. The drying time is, for example, 2 minutes to 20 minutes.

In consideration of the dyeability after stretching, the lower limit of the thickness of the resin layer to be formed is usually more than 3 μm. When the thickness of the finally obtained polarizer layer is 10 μm or less, the thickness of the resin layer to be formed is usually 30 μm or less. The thickness of the resin layer to be formed is preferably 5 μm to 20 μm.

  Moreover, in order to improve the adhesiveness of a base film and a polyvinyl alcohol-type resin, you may provide a primer layer between a base film and a resin layer. The primer layer is preferably formed from a composition containing a crosslinking agent or the like in a polyvinyl alcohol resin from the viewpoint of adhesion.

A film obtained by laminating a polyvinyl alcohol resin layer on the base film thus obtained is stretched to obtain a stretched film, and a resin layer of the stretched film obtained is dyed with a dichroic dye to form a polarizer layer. The dyeing process will be described below. A laminated film composed of a base film and a resin layer is uniaxially stretched so as to have a draw ratio of more than 5 times the original length of the laminated 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 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 is not sufficiently high. On the other hand, if the draw ratio exceeds 8 times, the laminated film is likely to break 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 is preferable. However, when the polarization performance is not so much required, a fixed end represented by transverse uniaxial stretching by the tenter method or the like. Uniaxial stretching may be used. Examples of the longitudinal stretching method include an inter-roll stretching method, a compression stretching method, and a stretching method using a tenter. The stretching process is not limited to the longitudinal stretching process, and may be an oblique stretching process or the like. Moreover, it is preferable that it is free end uniaxial stretching.

  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.

  In this embodiment, it is preferable to perform a stretching process in the temperature range of −30 ° C. to + 5 ° C. of the melting point of the base film. More preferably, the stretching process is performed in the temperature range from −25 ° C. to the melting point of the base film. When the stretching temperature is lower than the melting point of the base film 11 of −30 ° C., it becomes difficult to stretch the film at a high magnification exceeding 5 times. When the stretching temperature exceeds + 5 ° C. of the melting point of the base film, it is not preferable because stretching becomes difficult due to melting of the base film. In addition, extending | stretching temperature is in the said range, More preferably, it is 120 degreeC or more. This is because when the stretching temperature is 120 ° C. or higher, there is no difficulty in the stretching treatment even at a high stretching ratio of more than 5 times. The temperature adjustment of the stretching process is usually performed by adjusting the temperature of the heating furnace.

[Dyeing step (S30)]
Here, the polyvinyl alcohol resin layer of the 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 above 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% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and 0.025% by weight to 5% by weight. It is particularly preferred.

  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% by weight to 20% 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 is usually preferably in the range of 15 seconds to 15 minutes, and more preferably 1 minute to 3 minutes. Moreover, it is preferable that the temperature of a dyeing | staining solution exists in the range of 10 to 60 degreeC, and it is more preferable that it exists in the range of 20 to 40 degreeC. In the dyeing step, excess dyeing solution may be washed away with pure water.

  In the dyeing process, a crosslinking treatment can be performed after 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. The concentration of the crosslinking agent in the crosslinking solution is not limited to this, but is preferably in the range of 1% by weight to 20% by weight, and more preferably 6% by weight to 15% by weight.

  Iodide may be added to the crosslinking solution. By adding 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, barium iodide, calcium iodide, tin iodide, and titanium iodide. Is mentioned. The content of iodide is usually 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 3 ° C to 50 ° C, preferably 4 ° C to 20 ° C. The immersion time is usually 2 seconds to 300 seconds, preferably 3 seconds to 240 seconds.

  In the washing step, washing treatment with an iodide solution and water washing treatment may be combined, and a solution in which liquid alcohol such as methanol, ethanol, isopropyl alcohol, butanol, propanol or the like 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 ° C. to 95 ° C., and the drying time is usually about 1 minute to 15 minutes. By the above dyeing | staining process (S30), a polyvinyl alcohol-type resin layer has a function as a polarizer. In this specification, the polyvinyl alcohol-type resin layer which has a function as a polarizer is called a polarizer layer, and the laminated body provided with the polarizer layer on the base film is called a polarizing laminated film.

  In this embodiment, an aqueous solution of polyvinyl alcohol resin having a saponification degree of 99.0 mol% or less and degassed under reduced pressure is used for the polyvinyl alcohol resin layer, and in the stretching step (S20), 5 Since uniaxial stretching is performed at a stretching ratio exceeding twice, a good dyeing speed is maintained in the dyeing step (S30). In addition, the resin layer using the polyvinyl alcohol-type resin with a high saponification degree has a low dyeing speed in the dyeing step (S30), and the dyeing tends to be insufficient.

<Configuration of polarizing plate>
FIG. 2 is a schematic cross-sectional view showing an example of a basic layer configuration of the polarizing plate according to the present invention. The polarizing plate 13 includes a transparent protective film 14 and a polarizer layer 12 formed on one surface of the transparent protective film 14. The polarizer layer 12 has a thickness of 10 μm or less, and is formed from a polyvinyl alcohol resin in which a dichroic dye is adsorbed and oriented. The saponification degree 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 by, for example, a pressure-sensitive adhesive or an adhesive layer. Hereinafter, each component will be described in detail.

[Transparent protective film]
The transparent protective film 14 may be a simple transparent protective film having no optical function, or may be a transparent protective film having an optical function such as a retardation film or a brightness enhancement film. The material of the transparent protective film 14 is not particularly limited. For example, a cyclic polyolefin resin film, a cellulose acetate resin film made of a resin such as triacetyl cellulose or diacetyl cellulose, polyethylene terephthalate, polyethylene naphthalate. Examples thereof include films that have been widely used in the art, such as polyester resin films made of a resin such as polybutylene terephthalate, polycarbonate resin films, acrylic resin films, and polypropylene resin films.

  Examples of the cyclic polyolefin-based resin include appropriate commercial products such as Topas (registered trademark) (manufactured by Ticona), Arton (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Nippon ZEON ( ZEONEX (registered trademark) (manufactured by Nippon Zeon Co., Ltd.), Apel (registered trademark) (manufactured by Mitsui Chemicals, Inc.) can be suitably used. When such a cyclic polyolefin resin is formed into a film, a known method such as a solvent casting method or a melt extrusion method is appropriately used. In addition, pre-filmed cyclic polyolefins such as Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), SCA40 (manufactured by Sekisui Chemical Co., Ltd.), Zeonoa (registered trademark) film (manufactured by Optes Co., Ltd.), etc. A commercial product of a film made of a resin may be used.

  The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. An arbitrary retardation value can be imparted to the cyclic polyolefin-based resin film by stretching. Stretching is usually performed continuously while unwinding the film roll, and is stretched in the heating furnace in the roll traveling direction, the direction perpendicular to the traveling direction, or both. The temperature of the heating furnace is usually in the range from the vicinity of the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 ° C. The draw ratio is usually 1.1 to 6 times, preferably 1.1 to 3.5 times in one direction.

  Since the cyclic polyolefin resin film generally has poor surface activity, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment is performed on the surface to be bonded to the polarizing film. preferable. Among these, plasma treatment and corona treatment that can be performed relatively easily are preferable.

  Examples of the cellulose acetate-based resin film include commercially available products such as Fujitac (registered trademark) TD80 (manufactured by Fuji Film Co., Ltd.), Fujitac (registered trademark) TD80UF (manufactured by Fuji Film Co., Ltd.), and 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.) are preferably used. be able to.

  A liquid crystal layer or the like may be formed on the surface of the cellulose acetate-based resin film in order to improve viewing angle characteristics. Moreover, in order to provide a phase difference, what stretched the cellulose acetate type-resin film may be used. The cellulose acetate-based resin film is usually subjected to a saponification treatment in order to improve the adhesiveness with the polarizing film. As the saponification treatment, a method of immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide can be employed.

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

  The thickness of the transparent protective film 14 is preferably as thin as possible in order to satisfy the demand for thinning, preferably 88 μm or less, and more preferably 48 μm or less. In consideration of workability, it is preferably 5 μm or more.

[Polarizer layer]
The polarizer layer 12 can be configured similarly to the polarizer layer 12 of the above-described polarizing laminated film 10.

[Adhesive layer]
The pressure-sensitive adhesive used for bonding the transparent protective film 14 and the polarizer layer 12 is usually based on an acrylic resin, a styrene resin, a silicone resin, etc., and there are an isocyanate compound, an epoxy compound, and an aziridine compound. It consists of a composition to which a crosslinking agent such as
Furthermore, it can also be set as the adhesive layer which contains microparticles | fine-particles and shows light-scattering property.

  The thickness of the pressure-sensitive adhesive layer is preferably 1 μm to 40 μm in consideration of processability and durability characteristics. When the thickness of the pressure-sensitive adhesive layer is 3 μm to 25 μm, it is more preferable because the dimensional change of the polarizing film can be suppressed.

  In the method of bonding the transparent protective film 14 to the polarizer layer 12 with the pressure-sensitive adhesive, after the pressure-sensitive adhesive layer is provided on the surface of the transparent protective film 14, the film may be bonded to the polarizer layer 12. After providing an adhesive layer on the surface of 12, the transparent protective film 14 may be bonded here.

  The method for forming the pressure-sensitive adhesive layer is not particularly limited, and a solution containing each component including the above-mentioned base polymer is applied to the surface of the transparent protective film 14 or the surface of the polarizer layer 12 and dried. After forming the pressure-sensitive adhesive layer, the transparent protective film 14 and the polarizer layer 12 may be bonded together, or after forming the pressure-sensitive adhesive layer on the separator, transfer to the surface of the transparent protective film 14 or the surface of the polarizer layer 12. And may be laminated. Further, when the pressure-sensitive adhesive layer is formed on the surface of the transparent protective film 14 or the polarizer layer 12, if necessary, an adhesion treatment is performed on one or both of the surface of the transparent protective film 14 or the polarizer layer 12, or the pressure-sensitive adhesive layer. Corona treatment or the like may be performed.

[Adhesive layer]
Examples of the adhesive used for bonding the transparent protective film 14 and the polarizer layer 12 include a water-based adhesive using a polyvinyl alcohol-based resin aqueous solution, a water-based two-component urethane-based emulsion adhesive, and the like. When using the cellulose acetate type film hydrophilized by the saponification process etc. as the transparent protective film 14, a polyvinyl alcohol-type resin aqueous solution is used suitably as a water-based adhesive for bonding with the polarizer layer 12. FIG. Polyvinyl alcohol resins used as adhesives include vinyl alcohol homopolymers obtained by saponifying polyvinyl acetate, which is a homopolymer of vinyl acetate, as well as other single quantities copolymerizable with vinyl acetate. And vinyl alcohol copolymers obtained by saponifying the copolymer with the polymer, and modified polyvinyl alcohol polymers obtained by partially modifying the hydroxyl groups. A polyhydric aldehyde, a water-soluble epoxy compound, a melamine compound, a zirconia compound, a zinc compound, or the like may be added as an additive to the water-based adhesive. When such an aqueous adhesive is used, the adhesive layer obtained therefrom is usually 1 μm or less, and even when the cross section is observed with a normal optical microscope, the adhesive layer is practically not observed.

  The method of bonding the polarizer layer 12 and the transparent protective film 14 using an aqueous adhesive is not particularly limited. For example, the adhesive is uniformly applied to the surface of the polarizer layer 12 and / or the transparent protective film 14. The method of apply | coating, laminating | stacking another film on an application | coating surface, bonding with a roll etc., and drying is mentioned. Usually, an adhesive agent is apply | coated at the temperature of 15-40 degreeC after the preparation, and the bonding temperature is the range of 15 degreeC-30 degreeC normally.

  When using an aqueous adhesive, after bonding the polarizer layer 12 and the transparent protective film 14, it is dried in order to remove the water contained in the aqueous adhesive. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. When the temperature is lower than 30 ° C., the adhesive surface between the polarizer layer 12 and the transparent protective film 14 tends to be easily peeled off. If it is 90 ° C. or higher, the optical performance may be deteriorated by heat. The drying time can be 10 seconds to 1000 seconds, and particularly from the viewpoint of productivity, it is preferably 60 seconds to 750 seconds, and more preferably 150 seconds to 600 seconds.

  After drying, the film may be further cured at room temperature or slightly higher 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 lower than the temperature adopted at the time of drying.

  Moreover, a photocurable adhesive can also be used as an adhesive at the time of bonding the polarizer layer 12 and the transparent protective film 14. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

  Examples of the method of laminating the polarizer layer 12 and the transparent protective film 14 with a photocurable adhesive include, for example, a casting method, a Mayer bar coating method, a gravure coating method, a comma coater method, a doctor plate method, a die coating method, Examples include a method in which an adhesive is applied to the adhesive surface of the polarizer layer 12 and / or the transparent protective film 14 by a dip coating method, a spraying method, etc., and the both are overlapped. In the casting method, the polarizer layer 12 or the transparent protective film 14 which is an object to be coated is moved in a substantially vertical direction, a substantially horizontal direction, or an oblique direction between the two, and the adhesive is allowed to flow onto the surface. It is a method of spreading.

  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 together by being sandwiched by a nip roll or the like through the adhesive application surface. In addition, an adhesive is dropped between the polarizer layer 12 and the transparent protective film 14 in a state where the polarizer layer 12 and the transparent protective film 14 are overlapped, and then the laminate is uniformly pressed by a roll or the like. A method of spreading out can also be suitably used. In this case, a metal, rubber, or the like can be used as the material of the roll. Furthermore, after dropping an adhesive agent between the polarizer layer 12 and the transparent protective film 14, the method of passing this laminated body between rolls and pressurizing and spreading is also preferably employed. In this case, these rolls may be made of the same material or different materials. The thickness of the adhesive layer after being bonded using the nip roll or the like before drying or curing is preferably 0.01 μm to 5 μm.

  In order to improve the adhesion, the surface of the polarizer layer 12 and / or the transparent protective film 14 is appropriately subjected to surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment, saponification treatment, etc. You may give it. Examples of the saponification treatment include a method of immersing in an aqueous alkali solution such as sodium hydroxide or potassium hydroxide.

  When a photocurable resin is used as the adhesive, the photocurable adhesive is cured by irradiating active energy rays after joining 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 emission distribution at a wavelength of 400 nm or less is preferable. A microwave excitation mercury lamp, a metal halide lamp and the like are preferably used.

The light irradiation intensity to the photocurable adhesive is appropriately determined depending on the composition of the photocurable adhesive and is not particularly limited, but the irradiation intensity in the wavelength region effective for activating the polymerization initiator is 0.1 to 6000 mW / it is preferable that the 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 epoxy is generated by the heat radiated from the light source and the heat generated when the photo-curable adhesive is cured. There is little risk of yellowing of the resin or deterioration of the polarizing film. The light irradiation time to the photocurable adhesive is not particularly limited and is applied according to the photocurable adhesive to be cured, but the integrated light amount expressed as the product of the irradiation intensity and the irradiation time. Is preferably set to be 10 to 10,000 mJ / cm ² . When the cumulative amount of light to the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated to allow the curing reaction to proceed more reliably, and at 10,000 mJ / cm ² or less. In some cases, irradiation time does not become too long and good productivity can be maintained. The thickness of the adhesive layer after irradiation with active energy rays is usually about 0.001 to 5 μm, preferably 0.01 to 2 μm, more preferably 0.01 to 1 μm.

  When the photocurable adhesive is cured by irradiation with active energy rays, the curing is performed under conditions that do not deteriorate 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. It is preferable to carry out.

[Other optical layers]
The polarizing plate of the present invention produced as described above can be used as a polarizing plate in which other optical layers are laminated in practical use. Moreover, the said transparent protective film 14 may have a function of these optical layers. Examples of other optical layers include a reflective polarizing film that transmits certain types of polarized light and reflects polarized light that exhibits the opposite properties, a film with an antiglare function having an uneven shape on the surface, and a surface antireflection function. Examples thereof include an attached film, a reflective film having a reflective function on the surface, a transflective film having both a reflective function and a transmissive function, and a viewing angle compensation film.

  For example, DBEF (available from 3M, Sumitomo 3M Co., Ltd.), a commercially available product corresponding to a reflective polarizing film that transmits certain types of polarized light and reflects polarized light exhibiting the opposite properties, for example, APF (manufactured by 3M, available from Sumitomo 3M Limited). Examples of the viewing angle compensation film include an optical compensation film coated with a liquid crystal compound on the surface of the substrate and oriented, a retardation film made of a polycarbonate resin, and a retardation film made of a cyclic polyolefin resin. Commercially available products corresponding to an optical compensation film coated with a liquid crystal compound on the substrate surface and oriented are WV film (Fuji Film Co., Ltd.), NH film (Shin Nippon Oil Co., Ltd.), NR Examples include films (manufactured by Nippon Oil Corporation). Commercial products corresponding to retardation films made of cyclic polyolefin resins include Arton (registered trademark) film (manufactured by JSR Corporation), Essina (registered trademark) (manufactured by Sekisui Chemical Co., Ltd.), Zeonor ( Registered trademark) film (manufactured by Optes Co., Ltd.).

<Method for producing polarizing laminated film>
FIG. 3 is a flowchart showing an embodiment of a method for producing the polarizing laminated film 10 shown in FIG. According to this, the manufacturing method of the light-polarizing laminated film 10 forms a polyvinyl alcohol-based resin layer having a saponification degree of 99.0 mol% or less and degassed under reduced pressure on one surface of the base film 11. A resin layer forming step (S10) to obtain a laminated film, a stretching step (S20) in which the laminated film is subjected to a uniaxial stretching treatment at a draw ratio of more than 5 times to obtain a stretched film, and the resin layer is dyed with a dichroic dye. Thus, the dyeing step (S30) for obtaining the polarizing laminated film 10 as the polarizer layer 12 is performed in this order.

  The polarizing laminated film 10 obtained by this manufacturing method becomes the polarizing laminated film 10 provided with the polarizer layer 12 having a thickness of 10 μm or less on the stretched base film 11. This can be used as a polarizing plate as it is, or as an intermediate product for transferring the polarizer layer 12 to a transparent protective film, as will be described later.

The obtained polarizer has a visibility corrected single transmittance (Ty) of usually 40% or more, and a visibility correction polarization degree (Py) of usually 99.9% or more. Preferably, Ty is 41.0% or more and Py is 99.9% or more. More preferably, Ty is 42.5% or more and Py is 99.9% or more.

The visibility corrected single transmittance (Ty) and the visibility corrected polarization degree (Py) of the polarizer were measured with a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, V7100). MD transmittance and TD transmittance are obtained in the wavelength range of 380 nm to 780 nm, the single transmittance and the degree of polarization at each wavelength are calculated based on the formulas (1) and (2), and the 2 degree field of view of JIS Z 8701 Visibility correction was performed using (C light source), and the visibility correction single transmittance (Ty) and the visibility correction polarization degree (Py) were obtained. Here, the “MD transmittance” is the transmittance when the direction of polarized light emitted from the Glan-Thompson prism is parallel to the transmission axis of the polarizing plate sample. In the formulas (1) and (2), “MD” ". The “TD transmittance” is a transmittance when the direction of polarized light emitted from the Glan-Thompson prism and the transmission axis of the polarizing plate sample are orthogonal to each other. In the formulas (1) and (2), “TD”. It expresses.

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

<Production method of polarizing plate>
FIG. 4 is a flowchart showing an embodiment of a method for manufacturing the polarizing plate 13 shown in FIG.
According to this, the polarizing plate 13 is manufactured by forming a resin layer made of a polyvinyl alcohol resin defoamed under reduced pressure and having a saponification degree of 99.0 mol% or less on one surface of a base film. Resin layer forming step for forming a film (S10), Stretching step for forming a stretched film by subjecting the laminated film to a uniaxial stretching treatment at a stretch ratio of more than 5 times (S20), and dyeing with a dichroic dye as the polarizer layer 12 After performing the dyeing process (S30) which obtains a polarizing laminated film in this order, the transparent protective film 14 is stuck on the surface on the opposite side to the base film 11 side of the polarizer layer 12 of the polarizing laminated film. The lamination process (S40) which combines and obtains a multilayer film and the peeling process (S50) which peels the base film 11 from the said multilayer film are provided in this order.

  The polarizing plate 13 obtained by this manufacturing method becomes the polarizing plate 13 provided with the polarizer layer 12 having a thickness of 10 μm or less on the transparent protective film 14. The polarizing plate 13 can be used, for example, by being bonded to another optical film or a liquid crystal cell via a pressure-sensitive adhesive.

  Hereafter, each process of S10-S50 in FIG. 3 and FIG. 4 is demonstrated in detail. In addition, each process of S10-S30 of FIG. 3 and FIG. 4 is the same process.

[Bonding process (S40)]
Here, a transparent protective film is bonded to the surface of the polarizer layer opposite to the surface on the base film side to obtain a multilayer film. As a method of bonding a transparent protective film, the method of bonding the polarizer layer 12 and the transparent protective film 14 with an adhesive, and the method of bonding the polarizer layer 12 surface and the transparent protective film 14 with an adhesive are mentioned. . Suitable materials for the transparent protective film are as described in the description of the configuration of the polarizing plate. Moreover, the preferable method of bonding the polarizer layer 12 and the transparent protective film 14 using the adhesive suitable for use, the material of an adhesive, and these is as having demonstrated by description of the structure of the above-mentioned polarizing plate. .

[Peeling step (S50)]
In the manufacturing method of the polarizing plate of this embodiment, as shown in FIG. 4, after the bonding process (S40) which bonds a transparent protective film to the polarizer layer 12, the peeling process (S50) of a base film is performed. . In the base film peeling step (S50), the base film is peeled from the multilayer film. The peeling method of a base film is not specifically limited, It can peel by the method similar to the peeling process of the peeling film performed with a normal polarizing plate with an adhesive. After the transparent protective film laminating step (S40), it may be peeled off as it is, or once wound up in a roll shape, a separate peeling step may be provided and peeled off.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated further more concretely, this invention is not limited by these examples.

<Example 1>
(1) Production of base film Both surfaces of a resin layer comprising a random copolymer of propylene / ethylene containing about 5% by weight of ethylene units (“Sumitomo Noblen W151” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 138 ° C.) A long base film having a three-layer structure in which a resin layer made of a propylene homopolymer (“Sumitomo Noblen FLX80E4” manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 ° C.) is disposed on a multilayer extruder It was produced by the coextrusion molding used. The total thickness of the base film was 100 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer was 3/4/3.

(2) Preparation of coating solution Polyvinyl alcohol powder (“Z-200” manufactured by Nippon Synthetic Chemical Industry Co., Ltd., average polymerization degree 1100, average saponification degree 99.5 mol%) was dissolved in 95 ° C. hot water. An aqueous polyvinyl alcohol solution having a concentration of 3% by weight was prepared. The resulting aqueous solution was mixed with a crosslinking agent (“Smiles Resin 650” manufactured by Taoka Chemical Industry Co., Ltd.) at a ratio of 1 part by weight with respect to 2 parts by weight of the polyvinyl alcohol powder to form a primer layer forming coating solution. Got.

  The obtained primer layer forming coating solution was transferred to a 30 L (liter) stainless steel container and transferred to a coating facility.

  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 the concentration was 8% by weight. A polyvinyl alcohol aqueous solution was prepared and 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 30 L stainless steel container and transferred to a coating facility.

(3) Implementation of vacuum degassing The polyvinyl alcohol-based resin layer-forming coating solution prepared in (2) was placed in a processing container and treated with -0.04 MPa (gauge pressure) for 120 minutes. At this time, the container kept inhaling. The liquid temperature after the defoaming treatment was 26.0 ° C., and it was used for coating without any particular heating or cooling.

(4) Formation of primer layer and polyvinyl alcohol-based resin layer While continuously transporting the substrate film prepared in (1) above, one side is subjected to corona treatment, and a microgravure coater is applied to the corona-treated surface. The primer layer-forming coating solution prepared in the above (2) was continuously applied and dried at 60 ° C. for 3 minutes to form a primer layer having a thickness of 0.2 μm. Subsequently, while transporting the film, the coating liquid was continuously applied onto the primer layer using the comma coater filled with the coating liquid for forming the polyvinyl alcohol-based resin layer up to the coating head, and 90 A polyvinyl alcohol resin layer having a thickness of 11.0 μm was formed on the primer layer by drying at 70 ° C. for 1 minute, at 70 ° C. for 3 minutes, and then at 60 ° C. for 4 minutes.

  Furthermore, the base film surface opposite to the surface on which the polyvinyl alcohol-based resin layer is formed is treated in the same manner as described above, and a primer layer and a polyvinyl alcohol-based resin layer are sequentially formed on both surfaces of the base film. A laminated film comprising a primer layer having a thickness of 0.2 μm and a polyvinyl alcohol resin layer having a thickness of 11.0 μm and comprising a layer structure of polyvinyl alcohol resin layer / primer layer / base film / primer layer / polyvinyl alcohol resin layer. Got.

(5) Stretching of laminated film While continuously transporting the laminated film obtained in (4) above, it is 5.5 times in the longitudinal direction (film conveying direction) at a stretching temperature of 160 ° C. by a stretching method between nip rolls. A free film was uniaxially stretched at a magnification to obtain a stretched film. As for the thickness of the polyvinyl alcohol-type resin layer in a stretched film, one side was 5.5 micrometers and the other was 5.9 micrometers.

(6) Production of Polarizing Laminating Film After continuously immersing the stretched film produced in (5) above in a 60 ° C. hot water bath so that the residence time is 60 seconds, iodine and potassium iodide The polyvinyl alcohol-based resin layer was dyed by being immersed in a dyeing solution at 30 ° C. containing about 150 seconds, and then the excess dyeing solution was washed away with pure water at 10 ° C. Subsequently, a crosslinking treatment was performed by dipping in a crosslinking solution at 76 ° C. containing boric acid and potassium iodide so that the residence time was 600 seconds. 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 laminated film, the thicknesses of the polarizers laminated on both surfaces of the substrate were 5.8 μm and 6.0 μm, respectively.

(7) Observation of voids having a length of 100 μm or more In the obtained polarizing laminated film, the surface having a thickness of 6.0 μm was peeled off to prepare a single-area layer film comprising a base film and a polarizer 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 using a magnifier with a scale of 10 times on a flat light source. When a total of 20 sheets (1.2 m ² ) were confirmed, there were 8 voids with a length of 100 μm or more in the absorption axis direction, and the number per unit area was 6.7 / m ² .

The MD transmittance and TD transmittance in the wavelength range of 380 nm to 780 nm of the obtained single area layer film (single area layer film consisting of a base film and a polarizer layer having a thickness of 5.8 μm) were measured with a spectrophotometer with an integrating sphere (JASCO) V7100), and calculated the single transmittance and polarization degree at each wavelength based on the above formulas (1) and (2), and further according to the 2 degree field of view (C light source) of JIS Z 8701. When the visibility correction was performed and the visibility correction single transmittance (Ty) and the visibility correction polarization degree (Py) were determined, they were 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 an aqueous polyvinyl alcohol solution having a concentration of 3% by weight. The resulting aqueous solution was mixed with a crosslinking agent (“Smile Resin 650” manufactured by Taoka Chemical Co., Ltd.) at a ratio of 1 part by weight to 2 parts by weight of the polyvinyl alcohol powder to obtain an aqueous adhesive solution.

  Next, while continuously transporting the polarizing laminated film prepared in (6) above, the adhesive aqueous solution was coated on the polarizer layers on both sides, and then the saponification treatment was performed on the bonding surface. A protective film [transparent protective film made of triacetyl cellulose (TAC) (“KC4UY” manufactured by Konica Minolta Opto Co., Ltd.), thickness 40 μm] is bonded onto the polarizer layer and passed between a pair of bonding rolls. The laminated film which consists of layer structure of TAC / polarizer layer / primer layer / base film / primer layer / polarizer layer / TAC was produced.

  Next, the bonded film is peeled and divided at the interface between the base film and the primer layer, and a film composed of TAC / polarizer layer (5.8 μm) / primer layer / base film, primer layer / polarizer layer ( After obtaining a polarizing plate composed of 6.0 μm) / TAC, the base film was further peeled off from the former film to obtain another polarizing plate. In the process of peeling the base film, no troubles such as film breakage occurred.

(8) Adhesive layer laminating step The surface of the obtained polarizer having a thickness of 5.8 μm is subjected to corona treatment on the surface of the primer layer, and a PET film (separator film) having a release treatment having a thickness of 25 μm. A sheet-like pressure-sensitive adhesive on which an acrylic pressure-sensitive adhesive was laminated was attached to prepare a pressure-sensitive adhesive polarizing plate composed of “separate film / pressure-sensitive adhesive / primer layer / polarizing film / adhesive layer / transparent protective film”.

(9) Preparation of sample for evaluation The obtained pressure-sensitive adhesive polarizing plate was cut into a size of 60 mm × 60 mm so that the absorption axis was 0 ° with respect to the side, the separator film was peeled off, and the pressure-sensitive adhesive surface was made into glass. Pasted. This was used as an evaluation sample.

(10) Thermal shock test (HS test)
When 24 evaluation samples were placed in a test tank and a cycle of -40 ° C for 30 minutes and 85 ° C for 30 minutes was repeated 400 times, cracks occurred in the absorption axis direction of the polarizer.

(11) Observation of voids in cracks When a crack generated by transmission was observed using an optical microscope (Keyence VHX-500), one of the generated cracks was caused by a minute bubble (microbubble) in the crack. Those having minute voids of less than 100 μm were observed in the direction of the absorption axis, which seemed to be. The minute gap has a length in the thickness direction that is less than or equal to the thickness of the polarizer, and is very small. Unlike the void caused by bubbles, the minute gap is buried in the polarizer film. For this reason, it is usually difficult to find and observe by visual observation or a microscope, but as described above, it may be observed in a crack, which is considered to be a trigger for the crack.

  The size of the minute gap was less than 100 μm in the absorption axis direction. Separately, the center of the minute gap was cut perpendicularly to the absorption axis direction and the cross section was observed, and the length in the thickness direction was about 3 μm.

<Example 2>
Samples were prepared and evaluated in the same manner as in Example 1 except that the gauge pressure in the decompression process (3) in Example 1 was set to -0.09 MPa. The liquid temperature after the treatment was 24.7 ° C. The liquid obtained after the defoaming treatment was used for coating without particularly performing operations such as heating and cooling.

The thickness of the polarizer evaluated at this time was 5.2 μm, and a single-area layer film with a length of 100 μm or more in the absorption axis direction was confirmed. As a result, it was 1, and the number of voids per unit area was 0.83 / m. ² .

  Among the cracks generated in the HS test, only one crack was observed in the crack.

This single-area layer film had a visibility corrected single transmittance (Ty) and a visibility corrected polarization degree (Py) of Ty: 42.5% and Py: 99.93%, respectively.

<Comparative Example 1>
A polarizing laminate film was prepared in the same manner without carrying out the vacuum degassing treatment of (3) in Example 1, and the polarizer on one side was 5.8 μm and the other side was 5.1 μm. It was.

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

  An evaluation sample was prepared and evaluated for the surface having a thickness of 5.8 μm in the same manner as in Example 1. Of the cracks generated by the thermal shock test (HS test), there were minute voids that seemed to cause cracks in the cracks. 14 were observed

Voids: Number of voids with a length of 100 μm or more in the absorption axis direction (pieces / m ² )
Thermal shock test: Number of cracks in which fine voids of less than 100 μm were observed in the direction of the absorption axis in the crack (number)

According to the production method of the present invention, it is possible to produce a polarizer having few bubble defects and a reduced risk of cracking, a polarizing laminate comprising the polarizer, and a polarizing plate.
A polarizing plate made of such a polarizer can be formed in the voids derived from microbubbles remaining in the polyvinyl alcohol-based resin layer even when subjected to a thermal shock test in consideration of a temperature change when incorporated in a liquid crystal display device. There are few occurrences of cracks that seem to be caused.

DESCRIPTION OF SYMBOLS 10 Polarizing laminated film, 11 Substrate film, 12 Polarizer layer, 13 Polarizing plate, 14 Transparent protective film

Claims (2)

A polarizer layer made of a polyvinyl alcohol-based resin having a thickness of 10 μm or less is formed on at least one surface of the base film, and the number of voids having a length in the absorption axis direction of the polarizer layer of 100 μm or more is 10 / m ^2. It is a manufacturing method of the polarizing lamination film which is the following,
An aqueous solution of 4 to 9 wt% polyvinyl alcohol resin degassed under a gauge pressure of −0.04 MPa or less is applied to at least one surface of the substrate film, and polyvinyl is applied to at least one surface of the substrate film. Obtaining a laminated film in which a resin layer made of an alcohol-based resin is formed;
Stretching the laminated film to obtain a stretched film;
A step of dyeing the resin layer of the stretched film with a dichroic dye to form a polarizer layer,
Manufacturing method of polarizing laminated film. A laminating step of laminating a transparent protective film on the surface opposite to the base film side of the polarizer layer of the polarizing laminated film obtained by the production method according to claim 1 to obtain a multilayer film;
The manufacturing method of a polarizing plate including the peeling process which peels the said base film from a multilayer film.

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