TWI671554B - Polarizer with less bubble deficiency - Google Patents

Abstract

The present invention provides a polarizer made of a polyvinyl alcohol-based resin with a length of 100 μm or more in the absorption axis direction and a gap of 10 / m ² or less. The polarized light is laminated on at least one side of a base film. A polarizing laminated film of a sheet, a polarizing plate having a transparent protective film layered on an area of at least one side of the polarizing plate, and a method for manufacturing the same.

Description

Polarizer with few bubble defects

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 is 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, a thin polarizing plate has been developed. So far, a method has been proposed in which a polyvinyl alcohol-based resin layer is provided on the surface of a base film using an aqueous solution of a polyvinyl alcohol-based resin, followed by stretching and then dyeing to produce polarizers and polarizers (Patent Documents 1 and 2). .

[Prior technical literature] [Patent Literature]

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

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

The inventor of this case found that in manufacturing polarizers and polarizers In the method, when an aqueous solution of a polyvinyl alcohol resin is used, it is easy for the polyvinyl alcohol resin to suck air bubbles in the preparation step of the aqueous solution, and when the polyvinyl alcohol resin layer is formed, the surface of the formed polyvinyl alcohol resin layer is formed. It may cause round concave defects due to air bubbles, or voids due to round or linear air bubble defects generated in the extending direction of the stretched resin layer. The present inventors provide a polarizer having few voids caused by the aforementioned bubble defects, a polarizing laminated film formed by the polarizer, and a method for manufacturing the same.

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

A polarizing laminated film having a length of 100 μm or more in the absorption axis direction and 10 or less / m ² voids is typically produced by a manufacturing method including the following steps (a) to (c).

(a) Resin layer forming step: coating an aqueous solution of a polyvinyl alcohol-based resin that has been degassed under reduced pressure on at least one side of the base film to obtain a polymer film formed on at least one side of the base film. Laminated film of resin layer made of vinyl alcohol resin; (b) Stretching step: stretch the laminated film to obtain an stretched film; (c) Dyeing step: The resin layer of the stretched film composed of polyvinyl alcohol resin is used to The dichroic pigment is dyed to form a polarizer layer.

The invention provides a surface provided on one side of a polarizer. A method for manufacturing a polarizing plate of a transparent protective film includes the steps of laminating a transparent protective film on a surface of a polarizer layer of the polarizing laminated film opposite to the substrate film side to obtain a multilayer film (adhesion Step); and a step of peeling the base film from the multilayer film (peeling step).

According to the present invention, when manufacturing a polarizer, the polyvinyl alcohol-based resin aqueous solution is decompressed and defoamed, and the polyvinyl alcohol-based resin aqueous solution is applied as a coating liquid to a base film to form a polyvinyl alcohol-based film. In the case of the resin layer, it is possible to reduce the occurrence of bubbles in the coating liquid and cause round concave defects in the coating layer. As a result, even if a laminated film composed of a base film and a polyvinyl alcohol-based resin layer after coating is extended, it is possible to provide round or linear voids due to bubble defects generated in the extending direction. A polarizing plate in which the occurrence of ZnO is suppressed, and a polarizing laminated film including the polarizing plate.

10‧‧‧Polarized laminated film

11‧‧‧ substrate film

12‧‧‧ polarizer layer

13‧‧‧Polarizer

14‧‧‧ transparent protective film

FIG. 1 is a schematic cross-sectional view showing an example of a basic layer structure of a polarizing laminated 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 flowchart showing an embodiment of a method for manufacturing a polarizing laminated film shown in Fig. 1.

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

Hereinafter, one 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 laminated film of 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 of a polyvinyl alcohol-based resin having a dichroic dye adsorbed and oriented.

Each constituent element is explained 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 extensibility can be used. Specific examples of such thermoplastic resins include cellulose ester resins such as cellulose triacetate, polyester resins, polyether fluorene resins, polyfluorene resins, polycarbonate resins, and polyamides. Resins, polyimide resins, polyolefin resins, (meth) acrylic resins, cyclic polyolefin resins (norbornene resins), polyallylate resins, Polystyrene resins, polyvinyl alcohol resins, and mixtures thereof.

The material of the base film is preferably 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 this specification, "(meth) acrylic acid" means acrylic acid or methacrylic acid.

Cellulose ester resin 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. There are various commercially available products of cellulose triacetate, which is also advantageous from the viewpoint of easy availability and cost. Examples of commercially available products of cellulose triacetate include FUJITAC (registered trademark) TD80 (manufactured by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by FUJIFILM company), FUJITAC (registered trademark) TD80UZ ( FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD40UZ (FUJIFILM Co., Ltd.), KC8UX2M (Konica Minolta Opto Co., Ltd.), KC4UY (Konica Minolta Opto Co., Ltd.), etc.

Examples of the polyolefin-based resin include polyethylene and polypropylene. When a base film made of polypropylene is used, it is preferable because it can be easily stretched at a high rate. As the cyclic polyolefin-based resin, a norbornene-based resin can be preferably used. Cyclic polyolefin resin is a generic term for a resin polymerized by using a cyclic olefin as a polymerization unit, and examples thereof include Japanese Patent Laid-Open No. 1-240517, Japanese Patent Laid-Open No. 3-14882, and Japanese Patent Laid-Open No. 3-122137. Resin described in bulletins and the like. Specific examples include: ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (represented as random copolymers), And these graft polymers modified by unsaturated carboxylic acids or their derivatives, and these hydrides. Specific examples of the cyclic olefin include a norbornene-based monomer.

Various products of cyclic polyolefin resins are commercially available. Specific examples include: Topas (registered trademark) (manufactured by Ticona), ARTON (registered trademark) (made by JSR Co., Ltd.), ZEONOR (registered trademark) (made by Japan Ruon Co., Ltd.), ZEONEX (registered trademark) (made by Japan Ruon Co., Ltd.), APEL (registered trademark) (Mitsui Chemical Co., Ltd.).

As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be used. Examples include poly (meth) acrylates such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic copolymer, methyl methacrylate- (meth) acrylate copolymer, and methyl Methyl acrylate-acrylate- (meth) acrylic copolymer, methyl (meth) acrylate-styrene copolymer (MS resin, etc.), polymers with alicyclic hydrocarbon groups (for example: methyl methacrylate- Copolymers of cyclohexyl methacrylate, copolymers of methyl methacrylate-norbornyl (meth) acrylate, etc.). Preferred examples include poly (meth) acrylate C _1-6 alkyl esters such as poly (meth) acrylate. The (meth) acrylic resin is more preferably a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight).

Any appropriate additives may be added to the base film 11 in addition to the above-mentioned thermoplastic resin. Examples of such additives include ultraviolet absorbers, antioxidants, lubricants, plasticizers, release agents, anti-colorants, flame retardants, nuclear 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 when the content of the thermoplastic resin in the base film is less than 50% by weight, the surface cannot be sufficiently expressed. This is because of the high transparency of thermoplastic resins.

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

In order that the base film can be extended in a temperature range suitable for the extension of the polyvinyl alcohol-based resin, it is preferable to use a melting point of 110 ° C or higher. The melting point is preferably 130 ° C or higher. If the melting point of the base film does not reach 110 ° C, the base film will easily melt in the stretching step (S20) described later, and the stretching temperature cannot be sufficiently increased, making it difficult to stretch more than 5 times. The melting point of the base film is a value measured at a temperature rise rate of 10 ° C / min in accordance with ISO3146.

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

[Polarizer layer]

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

The polarizer layer 12 is, specifically, one in which a polyvinyl alcohol-based resin layer that is uniaxially stretched adsorbs and orients a dichroic dye. As polyethylene The enol-based resin may be obtained by saponifying a polyvinyl acetate-based resin. Examples of the polyvinyl acetate-based resin include copolymers of other monomers capable of copolymerizing with vinyl acetate in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Other monomers that can be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, ammonium acrylates, and the like.

The degree of saponification of polyvinyl alcohol resin is 99.0 mol% or less. In the present invention, since a polyvinyl alcohol-based resin having a degree of saponification of 99.0 mol% or less can maintain a constant dyeing speed even when uniaxial stretching of more than 5 times is performed, it is possible to produce thin types with high polarization performance with good efficiency. Advantages of polarizing laminated film. On the other hand, when a polyvinyl alcohol-based resin having a saponification degree of more than 99.0 mol% is used, the dyeing speed may be significantly slowed, and a polarizing laminated film having sufficient polarizing performance may not be obtained. In addition, at the time of manufacture, There are disadvantages that can take up to several times longer.

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

The so-called saponification degree is the ratio of the acetic acid group contained in the polyvinyl acetate resin of the polyvinyl alcohol resin as a raw material to the hydroxyl group after the saponification step. The value defined by the formula. It can be determined by a method specified 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 acetic acid groups that hinder crystallization. In addition, the polyvinyl alcohol-based resin used in the present invention is not particularly limited as long as the saponification degree is 99.0 mol% or less, and a part of the modified polyvinyl alcohol may be modified. Examples of modified polyvinyl alcohols include polyvinyl alcohol resins containing olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid, and crotonic acid, and alkyl esters and acrylic acids of unsaturated carboxylic acids. Modifiers such as amidine. 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%), PVA117 (degree of saponification: 98.0 to 99.0 mol%), and PVA624 (made by Kuraray Co., Ltd.). Saponification degree: 95.0 to 96.0 mole%) and PVA617 (saponification degree: 94.5 to 95.5 mole%); for example, AH-26 (Saponification degree: 97.0 to 98.8 mole%), AH, manufactured by Japan Synthetic Chemical Industry Co., Ltd. -22 (degree of saponification: 97.5 to 98.5 mol%), NH-18 (degree of saponification: 98.0 to 99.0 mol%) and N-300 (degree of saponification: 98.0 to 99.0 mol%); for example, JAPAN VAM & POVAL Co., Ltd.'s JF-17 (degree of saponification: 98.0 to 99.0 mole%), JF-17L (degree of saponification: 98.0 to 99.0 mole%) and JF-20 (degree of saponification: 98.0 to 99.0 mole%), etc.

The polyvinyl alcohol-based resin is coated on a base material, and a resin layer is formed, which can be used for production of the polarizer layer 12 of the present invention. The method for forming a resin layer of a polyvinyl alcohol-based resin is preferable in that the polyvinyl alcohol-based resin solution is applied because the polarizer layer 12 having a desired thickness is easily obtained. A method for forming a resin layer by mounting on the base film 11. The polarizer layer 12 preferably has a uniaxially-stretched stretching ratio of more than 5 times, and more preferably more than 5 times and 8 times or less.

Hereinafter, "a polarizer layer made of a polyvinyl alcohol-based resin is formed on at least one side of the base film, and the length of the polarizer layer in the direction of the absorption axis is 100 μm or more is 10 holes / m ^2. The manufacturing method of the following polarizing laminated film ".

Description "The coating of at least one side of the base film with an aqueous solution of a polyvinyl alcohol-based resin that has been degassed under reduced pressure is performed, and the surface of 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 applied to the base film is usually a solution containing 4 to 10% by weight of the polyvinyl alcohol-based resin, and preferably 6 to 9% by weight. If it is 4 wt% or less, since heat is more required during drying, there is a possibility that the line speed needs to be lowered and productivity may deteriorate. When it is 10% by weight or more, gelation tends to occur and storage stability may deteriorate. As the polyvinyl alcohol-based resin, those exemplified in the description of the polarizer can be used.

The aqueous solution of the polyvinyl alcohol resin is preferably an aqueous solution of the polyvinyl alcohol resin which has been defoamed. The defoaming method is preferably defoaming under reduced pressure in terms of a good degree of bubble removal efficiency. Since the PVA aqueous solution is very easy to foam, and the generated bubbles are not easy to break, it is more preferable to re-blend the bubbles generated by the foaming into the liquid by reducing the pressure, and reduce the pressure in a static state to maintain the reduced pressure. Wait for the bubbles to be removed from the aqueous solution

method

In the defoaming step of the present invention, a method of decompressing by suction with a vacuum pump can be used. The container for defoaming is not particularly specified, and any container that can withstand decompression can be used easily. Decompression is usually performed by reducing the pressure (gauge pressure) in the container as much as possible. The lower the pressure is, the shorter the processing time is, which is more suitable. The pressure (gauge pressure) in the container is usually set to -0.04Mpa or less, preferably -0.05Mpa or less, more preferably -0.08Mpa or less, and particularly preferably -0.09Mpa or less. The processing time is typically 30 minutes or more, preferably 60 minutes or more, and more preferably 120 minutes or more, and can also be extended within a range that does not impair productivity.

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

In the present invention, the manufacturing and coating steps of the PVA aqueous solution need not be continuous. After the polyvinyl alcohol-based resin is dissolved in water, the generated PVA aqueous solution is once moved to a drum can or a container. ), Etc., and then transported and supplied the PVA aqueous solution to the coating step. The equipment for dissolving polyvinyl alcohol resin (dissolving equipment) and the equipment for coating polyvinyl alcohol resin to the substrate (painting equipment) can be separated, so that each equipment 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 base film is as described in the structure of the polarizing laminated film. In this 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 a polyvinyl alcohol-based resin is usually formed by coating an aqueous solution of a polyvinyl alcohol-based resin on one surface of a substrate film, and evaporating and drying a solvent such as water. By forming the resin layer in this way, a thinner one can be formed. The method for applying an aqueous solution of a polyvinyl alcohol resin to a substrate film may be a roll coating method such as a wire rod coating method, a reverse coating, a gravure coating, a die coat method, or a notched wheel coating. A well-known method such as a comma coat method, a lip coat method, a spin coat method, a screen coating method, a spray coat method, a dipping method, and a spray method is suitably selected. Instead. The corner wheel coating method (knife coater), die coating method, and lip coating method are preferred. The drying temperature is, for example, 50 ° C to 200 ° C, and preferably 60 ° C to 150 ° C. The drying time is, for example, 2 minutes to 20 minutes.

When the thickness of the resin layer to be formed is taken into consideration, the lower limit is usually a thickness exceeding 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 formed resin layer is preferably 5 μm to 20 μm.

In addition, in order to improve the base film and polyvinyl alcohol resin The adhesion of the layer may also be provided between the base 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.

[Extended step (S20)]

The following describes "the stretching step of obtaining a stretched film by stretching the laminated film having the polyvinyl alcohol-based resin layer laminated on the substrate film thus obtained." A laminated film made of a base film and a resin layer is uniaxially stretched so as to have an extension ratio of more than 5 times the length before the extension step of the laminated film to obtain an extended film. The uniaxial stretching is preferably performed so that the stretching ratio is more than 5 times and 8 times or less. If the stretching ratio is 5 times or less, the resin layer made of a polyvinyl alcohol-based resin is not sufficiently oriented, and as a result, the degree of polarization of the polarizer layer cannot be sufficiently increased. On the other hand, if the stretching ratio exceeds 8 times, the laminated film is likely to be cracked during stretching, and at the same time, the thickness of the stretched film becomes thinner than required, and the workability / handling property of the subsequent steps may be reduced. The stretching process of the stretching step (S20) is not limited to one-stage stretching, and may be divided into multiple stages. When it is performed in multiple stages, the stretching process is performed in such a way that the total stretching ratio of all stages of the stretching process exceeds 5 times.

In the stretching step (S20) of this embodiment, it is preferable to perform longitudinal stretching processing on the longitudinal direction of the laminated film. When such a degree of polarizing performance is not required, it is transverse uniaxial stretching by the tenter method. The uniaxial extension of the fixed end, etc., is not a problem. Examples of the longitudinal stretching method include a roll-to-roll stretching method, a compression stretching method, and a method using a tenter to stretch. The stretching process is not limited to the longitudinal stretching process, and may be Oblique extension processing, etc. Moreover, it is preferable that the free end extends uniaxially.

In addition, the stretching treatment may be performed by any of a wet stretching method and a dry stretching method. A dry stretching method is preferable in that a temperature at which the laminated film is stretched can be selected from a wide range.

In this embodiment, it is preferable to perform the extension treatment at a temperature range of -30 ° C to + 5 ° C, which is the melting point of the base film. It is more preferable to perform the extension treatment in a temperature range from the melting point of the base film to -25 ° C to the melting point. If the stretching temperature is -30 ° C lower than the melting point of the base film 11, it will be difficult to stretch at a high rate exceeding 5 times. If the elongation temperature exceeds the melting point of the base material film by + 5 ° C, it becomes difficult to extend the base material film due to melting. The elongation temperature is within the above range, and more preferably 120 ° C or higher. This is because when the stretching temperature is 120 ° C. or higher, even if the stretching ratio is higher than 5 times, the difficulty in stretching processing is not accompanied. The temperature adjustment of the stretching treatment is usually performed by adjusting the temperature of the heating furnace.

[Dyeing step (S30)]

The "dyeing step of forming a polarizer layer by dyeing the resin layer of the obtained stretched film with a dichroic dye" will be described below. Here, the polyvinyl alcohol-based resin layer of the stretched film is dyed with a dichroic dye. Examples of the dichroic dye include iodine and organic dyes. Organic dyes can be used: 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 kinds.

The dyeing step is performed, for example, by immersing the entire stretched film in a solution (dyeing solution) containing the dichroic pigment. As the dyeing solution, a solution obtained by dissolving the dichroic pigment in a solvent can be used. The solvent of the dyeing solution is generally water, and an organic solvent compatible with water can be further added. The concentration of the dichroic pigment is preferably 0.01% by weight to 10% by weight, more preferably 0.02% by weight to 7% by weight, and even more preferably 0.025% by weight to 5% by weight.

When iodine is used as a dichroic dye, the dyeing efficiency can be further improved. Therefore, it is preferable to further add iodide. 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. The addition ratio of these iodides is preferably 0.01% 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 based on weight ratio, 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 to The range of 1:70.

The time during which the stretched film is immersed 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. The temperature of the dyeing solution is preferably in the range of 10 ° C to 60 ° C, and more preferably in the range of 20 ° C to 40 ° C. In the dyeing step, the remaining dyeing solution may be washed away with pure water.

In the dyeing step, the lines may be dyed and then cross-linked. The crosslinking treatment can be performed, for example, by immersing the stretched film in a solution (crosslinking solution) containing a crosslinking agent. As the crosslinking agent, conventionally known ones can be used. Examples include boron compounds such as boric acid and borax, or glyoxal and glutaraldehyde. These may be used singly 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, and may further include an organic solvent compatible with water. The concentration of the crosslinking agent in the crosslinking solution is not limited to the following, but it is preferably in the range of 1% to 20% by weight, and more preferably in the range of 6% to 15% by weight.

Iodide can also 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. The content of iodide is usually 0.05 to 15% by weight, and more preferably 0.5 to 8% by weight.

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

Preferably, the washing step and the drying step are performed at the end. The washing step may be performed with a water washing treatment. The water washing treatment is usually performed by immersing the stretched film in pure water such as ion-exchanged water or distilled water. The water washing temperature is usually 3 ° C to 50 ° C, preferably 4 ° C to 20 ° C. The dipping time is usually from 2 seconds to 300 seconds, preferably from 3 seconds to 240 seconds bell.

The washing step may be a combination of washing treatment with an iodide solution and water washing treatment, and a solution prepared with liquid alcohols such as methanol, ethanol, isopropanol, butanol, and propanol may be suitably used.

After the washing step, a drying step is preferably performed. The drying step can be performed by any appropriate method (for example, natural drying, air drying, and heating drying). For example, the drying temperature during heating and drying is usually 20 ° C to 95 ° C, and the drying time is usually about 1 minute to 15 minutes. Through the above dyeing step (S30), the polyvinyl alcohol-based resin layer can be made to function as a polarizer. In this 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 multilayer film.

In this 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 degassing under reduced pressure, and in the extension step (S20), it is more than 5 The stretching ratio is uniaxially extended, so a good dyeing speed can be maintained in the dyeing step (S30). In addition, 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 reduced, and 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 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 of a polyvinyl alcohol-based resin having a dichroic dye oriented. The degree of saponification of the polyvinyl alcohol 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, an adhesive or an adhesive layer. Each constituent element is explained in detail below.

[Transparent protective film]

The transparent protective film 14 may be a simple transparent protective film having no optical function, and it may be a transparent protective film having both an optical function and a so-called retardation film or a brightness enhancement film. The material of the transparent protective film 14 is not particularly limited, and examples thereof include, for example, a cellulose acetate resin film made of a cyclic polyolefin resin film, cellulose triacetate, and cellulose diacetate resin. Polyester resin film, polycarbonate resin film, (meth) acrylic resin film made of resins of ethylene phthalate, polyethylene naphthalate, and polybutylene terephthalate, Polypropylene-based resin films and the like have conventionally been widely used in this field.

As the cyclic polyolefin resin, suitable commercially available products can be suitably used, for example, Topas (registered trademark) (manufactured by Ticona), ARTON (registered trademark) (manufactured by JSR Corporation), ZEONOR (registered trademark) (Japan) (Made by Zeon Co., Ltd.), ZEONEX (registered trademark) (made by Japan Ruon Co., Ltd.), APEL (registered trademark) (made by Mitsui Chemicals Co., Ltd.). 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 can be suitably used. In addition, pre-made membrane rings such as Escena (registered trademark) (made by Sekisui Chemical Industry Co., Ltd.), SCA40 (made by Sekisui Chemical Industry Co., Ltd.), and Zeonor (registered trademark) FILM (made by OPTES Co., Ltd.) can also be used. A commercially available product of a film made of a polyolefin resin.

The cyclic polyolefin resin film may be uniaxially stretched or biaxially stretched. By stretching, an arbitrary retardation value can be given to the cyclic polyolefin resin film. Stretching is usually carried out continuously while rolling the film out of the reel, and in the heating furnace, it extends in the direction of the reel, in a direction perpendicular to the direction of the reel, or in both directions. The temperature of the heating furnace is usually in the range from the glass transition temperature of the cyclic polyolefin resin to the glass transition temperature + 100 ° C. The stretching magnification is usually 1.1 to 6 times in one direction, preferably 1.1 to 3.5 times.

Cyclic polyolefin resin film is generally poor in surface activity, so it is preferable to perform plasma treatment, corona discharge treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment on the surface next to the polarizing film. And other surface treatment. Among them, plasma treatment and corona discharge treatment which are relatively easy to implement are more suitable.

The cellulose acetate-based resin film can be suitably used with commercially available products, such as: FUJITAC (registered trademark) TD80 (manufactured by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD80UF (manufactured by FUJIFILM company), FUJITAC (registered trademark) ) TD80UZ (made by FUJIFILM Co., Ltd.), FUJITAC (registered trademark) TD40UZ (made by FUJIFILM Co., Ltd.), KC8UX2M (made by Konica Minolta Opto Co., Ltd.), and KC4UY (made by Konica Minolta Opto Co., Ltd.).

A liquid crystal layer or the like can be formed on the surface of the cellulose acetate resin film to improve viewing angle characteristics. In order to impart a retardation, a stretched cellulose acetate resin film may be used. In order to improve the adhesion to a polarizing film, a cellulose acetate-based resin film is usually subjected to a saponification treatment. Saponification The treatment can be performed by immersing in an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide.

An optical layer such as a hard coat layer, an anti-glare layer, or an anti-reflection layer may be formed on the surface of the transparent protective film 14 as described above. The method of forming these optical layers on the surface of a transparent protective film is not specifically limited, A well-known method can be used.

When it is desired to meet the requirements for thinness, the thickness of the transparent protective film 14 is preferably as thin as possible, more preferably 88 μm or less, and even more preferably 48 μm or less. When considering workability, it is more preferable that it is 5 micrometers or more.

[Polarizer layer]

The polarizer layer 12 may have the same structure as the polarizer layer 12 of the polarizing laminated film 10 described above.

[Adhesive layer]

Adhesives that can be used for bonding the transparent protective film 14 and the polarizer layer 12 are usually made of acrylic resin, styrene resin, silicone resin, etc. as the matrix polymer, and an isocyanate compound, a ring, etc. are added thereto. A composition made of a crosslinking agent such as an oxygen compound and an aziridine compound.

It may further contain fine particles as an adhesive layer expressing light scattering.

In consideration of processability and durability characteristics, the thickness of the adhesive layer is preferably 1 μm to 40 μm. When the thickness of the adhesive layer is 3 μm to 35 μm, it is more preferable because the dimensional change of the polarizing film can also be suppressed.

In the method of bonding the transparent protective film 14 to the polarizer layer 12 by using an adhesive, an adhesive layer may be provided on the surface of the transparent protective film 14 and then bonded to the polarizer layer 12. After an adhesive layer is provided on the surface, the transparent protective film 14 is stuck thereon.

The method for forming the adhesive layer is not particularly limited, and the surface of the transparent protective film 14 or the surface of the polarizer layer 12 may be coated with a solution containing the above-mentioned matrix polymer as the main component and dried to form the adhesive layer. The transparent protective film 14 and the polarizer layer 12 are bonded together, or an adhesive layer is 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. In addition, when the adhesive layer is formed on the surface of the transparent protective film 14 or the surface of the polarizer layer 12, if necessary, it may be on the surface of the transparent protective film 14 or the surface of the polarizer layer 12, or on the surface of the adhesive layer. Adhesive treatment is performed on one or both sides, such as corona discharge treatment.

[Adhesive layer]

An adhesive that can be used for bonding the transparent protective film 14 and the polarizer layer 12 includes, for example, an aqueous adhesive such as a polyvinyl alcohol-based resin aqueous solution and an aqueous two-liquid amine ester emulsion-based adhesive. When a cellulose acetate-based film that has been subjected to a hydrophilization treatment such as saponification treatment is used as the transparent protective film 14, a polyvinyl alcohol-based resin aqueous solution can be suitably used as an aqueous adhesive for bonding the polarizer layer 12. In the case of using a polyvinyl alcohol-based resin as an adhesive, in addition to a vinyl alcohol homopolymer obtained by saponifying a polyvinyl acetate which is a vinyl acetate homopolymer, there are also vinyl acetate and A vinyl alcohol-based copolymer obtained by saponifying a copolymer of other monomers that can be copolymerized therewith, and a modified polyvinyl alcohol-based copolymer further modified by partially modifying these groups. Polymer, etc. Polyvalent aldehydes, water-soluble epoxy compounds, melamine-based compounds, zirconia compounds, zinc compounds, and the like may be added to the water-based adhesive as additives. When such an aqueous adhesive is used, the adhesive layer obtained by this method is usually 1 μm or less, and even if the cross section is observed with a general optical microscope, the adhesive layer is not actually observed.

The method of bonding the polarizer layer 12 and the transparent protective film 14 with an aqueous adhesive is not particularly limited, and examples thereof include uniformly coating the adhesive on the surface of the polarizer layer 12 and / or the transparent protective film 14 and applying The other film is laminated on the surface, and the film is bonded and dried by a roller or the like. Usually, the adhesive is applied at a temperature of 15 to 40 ° C after the preparation thereof, and the bonding temperature is usually in a range of 15 to 30 ° C.

When the water-based adhesive is used, it is dried after removing the water contained in the water-based adhesive after bonding the polarizer layer 12 and the transparent protective film 14 together. The temperature of the drying furnace is preferably 30 ° C to 90 ° C. If it does not reach 30 degreeC, the adhesive surface of the polarizer layer 12 and the transparent protective film 14 will tend to peel easily. If it is 90 ° C or higher, 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, preferably 60 seconds to 750 seconds, and more preferably 150 seconds to 600 seconds.

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

In addition, as a polarizer sheet 12 and a transparent protective film At 14 o'clock, a photocurable adhesive can also be used. Examples of the photocurable adhesive include a mixture of a photocurable epoxy resin and a photocationic polymerization initiator.

Examples of a method for bonding the polarizer layer 12 and the transparent protective film 14 with a photocurable adhesive include, for example, a flow method, a Meyer bar coating method, a gravure coating method, and a corner wheel coating method. A method in which an adhesive is applied to the adhering surface of the polarizer layer 12 and / or the transparent protective film 14 by a mechanical method, a doctor blade method, a die coating method, a dip coating method, a spray method, or the like, and the two are superposed. . The streamer method involves moving the polarizer layer 12 or the transparent protective film 14 of the object to be coated in a substantially vertical direction, a horizontal direction, or an inclined direction therebetween, while flowing down the surface and spreading it.剂 的 方法。 Agent method.

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 sandwiched and bonded by a nip roll or the like through the adhesive application surface, and then bonded. . Moreover, it can also be suitably used in a state where the polarizer layer 12 and the transparent protective film 14 are superimposed, and after the adhesive is dropped between the polarizer layer 12 and the transparent protective film 14, the laminate is pressurized with a roller or the like and uniformly applied. Rolling method. In this case, the material of the roller may be metal, rubber, or the like. In addition, it is also suitable to use a method in which after the adhesive is dropped between the polarizer layer 12 and the transparent protective film 14, the laminate is passed between the rollers and pressurized to be stretched. At this time, the rollers may be the same material or different materials. The thickness of the adhesive layer after lamination using the nip roller or the like before drying or curing is preferably 0.01 μm to 5 μm.

On the adhering surface of the polarizer layer 12 and / or the transparent protective film 14, in order to improve adhesion, plasma treatment and corona discharge may be suitably performed. Surface treatments such as electric treatment, ultraviolet irradiation treatment, flame treatment, saponification treatment, and the like. Examples of the saponification treatment include a method of immersion 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 bonding the polarizer layer 12 and the transparent protective film 14 and then irradiating active energy rays. The source of the active energy ray is not particularly limited, but an active energy ray having a light emission distribution of a wavelength of 400 nm or less is preferred, and specifically, a low-pressure mercury lamp, a medium-pressure mercury lamp, a high-pressure mercury lamp, and an ultrahigh voltage Mercury lamps, chemical lamps, black-light lamps, microwave-excited 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. The irradiation intensity in the wavelength range effective for the activation of the polymerization initiator is preferably 0.1 to 6000 mW / cm ² . When the irradiation intensity of 0.1mW / cm ² or more, the reaction time does not become excessively long, is 6000mW / cm ² or less, occurrence of heat radiated by a light source and a light-curing and then heat-induced hardening of the epoxy resin when There is less concern about yellowing or deterioration of the polarizing film. The light time of the light-curing adhesive is not particularly limited as long as it is applicable depending on the light-curing adhesive of the object to be cured, but the cumulative light amount expressed as the product of the above-mentioned irradiation intensity and irradiation time is preferably It is set to be 10 to 10000 mJ / cm ² . When the total light amount of the photocurable adhesive is 10 mJ / cm ² or more, a sufficient amount of active species derived from the polymerization initiator can be generated, and the curing reaction proceeds more reliably. When the light curing time is 10,000 mJ / cm ² or less, the irradiation time Does not become too long, and maintains good productivity. The thickness of the adhesive layer after active energy ray irradiation is usually about 0.001 μm to 5 μm, preferably 0.01 μm to 2 μm, and more preferably 0.01 μm to 1 μm.

When the photo-curable adhesive is hardened by irradiating active energy rays, it is preferable that the polarizer, the transmittance and the hue of the polarizer layer 12 and the various functions of the polarizer such as the transparency of the transparent protective film 14 are not reduced. Harden under the conditions.

[Other optical layers]

The polarizing plate of the present invention manufactured in the above manner can be used as a polarizing plate with other optical layers laminated in actual use. Moreover, the above-mentioned transparent protective film 14 may also function as these optical layers. Examples of other optical layers include reflective polarizing films that can penetrate a certain type of polarized light and reflect and display polarized light having properties opposite to that of the polarized light, a film having an uneven shape on the surface, and an anti-glare function. Film with surface anti-reflection function, reflection film with reflection function on the surface, semi-transmission reflection film with both reflection function and transmission function, and viewing angle compensation film.

A commercially available reflective polarizing film that is equivalent to polarized light that can penetrate a certain type of polarized light and reflect and display properties opposite to this type of polarized light. For example, DBEF (manufactured by 3M Corporation, available from Sumitomo 3M Co., Ltd.) APF (3M company system, can be obtained from Sumitomo 3M Co., Ltd.). 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. . Examples of commercially available products that are equivalent to an oriented optical compensation film coated with a liquid crystal compound on the substrate surface include a WV film (manufactured by FUJIFILM Co., Ltd.) and an NH film (new Japan (Produced by Petroleum Corporation), NR membrane (produced by New Japan Petroleum Corporation), etc. In addition, commercially available products equivalent to a retardation film made of a cyclic polyolefin resin include: ARTON (registered trademark) film (manufactured by JSR Corporation), Escena (registered trademark) (Sekisui Chemical Industry Co., Ltd. Company), ZEONOR (registered trademark) FILM (manufactured by OPTES Co., Ltd.), etc.

[Manufacturing method of polarizing laminated film]

Fig. 3 is a flowchart showing an embodiment of a method for manufacturing the polarizing laminated film 10 shown in Fig. 1. According to this, the method for manufacturing the polarizing laminated film 10 sequentially performs 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 11 and The polyvinyl alcohol-based resin layer that is degassed under reduced pressure becomes a laminated film; the stretching step (S20) is a uniaxial stretching treatment of the laminated film at an extension ratio of more than 5 times, and becomes a stretched film; a dyeing step (S30) It is obtained by dyeing the resin layer with a dichroic dye to obtain a polarizing laminated film 10 as a polarizer layer 12.

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

The luminous factor modified monomer transmittance (Ty) of the obtained polarizer is usually 40% or more, and the luminous factor modified polarization (Py) is usually 99.9% or more. Preferably, Ty is 41.0% or more, and Py is 99.9% or more. Still more preferably, Ty is 42.5% or more, and Py is 99.9% or more.

The luminous factor-corrected monomer transmittance (Ty) and the luminous factor-corrected polarization (Py) of the polarizer were measured using a spectrophotometer with an integrating sphere (manufactured by JASCO Corporation, V7100). Calculate the MD transmittance and TD transmittance in the range of 380nm to 780nm, and calculate the individual transmittance and polarization of each wavelength according to formula (1) and formula (2), and further apply JIS Z 8701-2 Luminance factor correction is performed in a field of view (° C light source), and the luminous factor correction unit transmittance (Ty) and luminous factor correction polarization (Py) are obtained. Among them, "MD transmittance" is the transmittance when the direction of polarized light emitted from Glan-Thompson prism is parallel to the transmission axis of the polarizer sample. In the formula (2), "MD" is used. Moreover, the "TD transmittance" is the transmittance when the direction of the polarized light emitted by Glan-Thomson 稜鏡 perpendicularly intersects the transmission axis of the polarizer sample, and is expressed in equations (1) and (2). It is indicated by "TD".

Cell Transmittance (%) = (MD + TD) / 2 Formula (1)

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

[Manufacturing method of polarizing plate]

Fig. 4 is a flowchart showing an embodiment of a method of manufacturing the polarizing plate 13 shown in Fig. 2. According to this, the manufacturing method of the polarizing plate 13 sequentially performs 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 base film, and defoams under reduced pressure. The resin layer made of polyvinyl alcohol resin becomes a laminated film; the stretching step (S20), which is a uniaxial stretching treatment of the laminated film at an extension ratio of more than 5 times to become a stretched film; the dyeing step (S30 ), Which is dyed with dichroic pigments A polarizing laminated film as the polarizer layer 12 is obtained; thereafter, the following steps are sequentially provided: a laminating step (S40), which is on the side of the base film 11 of the polarizing layer 12 of the polarizing laminated film as follows: The transparent protective film 14 is bonded to the opposite surface to obtain a multilayer film. In the peeling step (S50), the base film 11 is peeled from the multilayer film.

The polarizing plate 13 obtained by such a manufacturing method is a polarizing plate 13 provided with a polarizer 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.

Each step of S40 to S50 in FIG. 4 will be described in detail below. The steps S10 to S30 in FIG. 4 are the same steps as the steps S10 to S30 in FIG. 3.

[Laminating step (S40)]

Here, a multilayer protective film is obtained by laminating a transparent protective film on a surface opposite to the surface on the base film side of the polarizer layer. 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 structure of the above-mentioned polarizing plate. Suitable adhesives, adhesive materials, and the preferred methods of using these to adhere the polarizer layer 12 and the transparent protective film 14 are as described in the structure of the polarizing plate described above.

[Stripping step (S50)]

As shown in FIG. 4, the method for manufacturing a polarizing plate in this embodiment is after the step (S40) of bonding a transparent protective film to the polarizer layer 12. Then, the base film peeling step (S50) is performed. The substrate film peeling step (S50) is to peel the substrate film from the multilayer film. The peeling method of the base film is not particularly limited, and it can be peeled in the same manner as the peeling step of a peeling film usually performed on a polarizing plate with an adhesive. It can be peeled off immediately after the step (S40) of laminating the transparent protective film, or it can be peeled off by setting a peeling step after being rolled up into a reel shape once.

Examples and comparative examples are shown below to further specifically describe the present invention, but the present invention is not limited to these examples.

(Example)

[Example 1]

(1) Production of substrate film

A base film is produced by co-extrusion molding using a multi-layer extrusion molding machine, which is a random copolymer of propylene / ethylene containing about 5 wt% of ethylene units (manufactured by Sumitomo Chemical Co., Ltd.) "Sumitomo NOBLEN W151", melting point Tm = 138 ° C) The resin layer formed from both sides is a homopolymer of propylene ("Sumitomo NOBLENFLX80E4" manufactured by Sumitomo Chemical Co., Ltd., melting point Tm = 163 ° C) A three-layer long base film with a resin layer formed. The total thickness of the base film is 100 μm, and the thickness ratio (FLX80E4 / W151 / FLX80E4) of each layer is 3/4/3.

(2) Preparation of coating liquid

Polyvinyl alcohol powder ("Z-200" manufactured by Nippon Synthetic Chemical Industry Co., Ltd., with an average degree of polymerization of 1100 and an average degree of saponification of 99.5 mole%) was dissolved in hot water at 95 ° C to prepare polyethylene having a concentration of 3% by weight. Alcohol solution. In the obtained aqueous solution, 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder was used. A cross-linking agent ("Sumirez Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) was mixed in a proportion by weight to obtain a coating liquid for forming an undercoat layer.

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

Also, polyvinyl alcohol powder ("PVA124" manufactured by Kuraray Co., Ltd., average degree of polymerization of 2400, average degree of saponification 98.0 to 99.0 mole%) was dissolved in hot water at 95 ° C to prepare a polyvinyl alcohol having a concentration of 8% by weight An aqueous solution was 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) Decompression defoaming

The coating liquid for forming a polyvinyl alcohol-based resin layer prepared in (2) was put into a processing container and treated at -0.04 MPa (gauge pressure) for 120 minutes. The container is continuously inhaling. The temperature of the liquid after the defoaming treatment is increased to about 26.0 ° C, and it is used for painting without cooling.

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

While continuously carrying the base film produced in the above (1), a corona discharge treatment is performed on one side of the base film, and the corona discharge-treated surface is continuously coated with the micro gravure coater. (2) The prepared coating liquid for forming an undercoat layer was dried at 60 ° C. for 3 minutes, thereby forming an undercoat layer having a thickness of 0.2 μm. Next, while the film is being transported, the coating wheel is filled with a coating liquid for forming a polyvinyl alcohol-based resin layer, and the above-mentioned notch wheel coater is used to continuously coat the coating liquid on the undercoat layer. Dry at 90 ° C for 1 minute, at 70 ° C for 3 minutes, and then at 60 ° C for 4 minutes. 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 substrate film surface opposite to the surface on which the polyvinyl alcohol-based resin layer is formed, and an undercoat layer and a polyvinyl alcohol-based resin layer are sequentially formed, and formed on both surfaces of the substrate 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 are obtained from a layer structure of a polyvinyl alcohol-based resin layer / undercoat layer / substrate film / undercoat layer / polyvinyl alcohol-based resin layer. Into a laminated film.

(5) Extension of laminated film

While continuously conveying the laminated film obtained in the above (4), while extending between the nip rolls, the free-end uniaxial extension was performed at a stretching temperature of 160 ° C in the longitudinal direction (film conveying direction) at a factor of 5.5 times, thereby becoming Stretch film. The thickness of the polyvinyl alcohol-based resin layer of the stretched film is 5.5 μm in one and 5.9 μm in the other.

(6) Fabrication of polarizing laminated film

While continuously conveying the stretched film prepared in (5) above, immersed in a warm water bath at 60 ° C so that the retention time is 60 seconds, and then immersed in a solution containing iodine and potassium iodide so that the retention time is about 150 seconds In the dyeing solution at 30 ° C, the polyvinyl alcohol-based resin layer was dyed, and then the remaining dyeing solution was washed with pure water at 10 ° C. Then, it was immersed in a cross-linking solution at 76 ° C. containing boric acid and potassium iodide so that the retention time was 600 seconds, and subjected to a cross-linking treatment. Thereafter, it 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 sides of the substrate were 5.8 μm and 6.0 μm, respectively.

(7) Observation of voids with a length of 100 μm or more

Among the obtained polarizing laminated films, a polarizer layer having a thickness of 6.0 μm was used to form a single-area layer film composed of 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 on a flat light source using a magnifying glass with a scale of 10 times and a scale. A total of 20 laminated films (1.2 m ² ) were confirmed. There were 8 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 single-area layer film (single-area layer film made of a base film and a polarizer layer with a thickness of 5.8 μm) measured by a spectrophotometer with a integrating sphere (manufactured by JASCO Corporation, V7100) has a wavelength of The MD transmittance and TD transmittance in the range of 780nm are calculated according to the aforementioned formulas (1) and (2) for the individual transmittance and polarization of each wavelength, and further according to JIS Z 8701's 2-degree field of view (° C light source ) The luminous factor correction is performed, and the luminous factor corrected monomer transmittance (Ty) and the luminous factor corrected polarization (Py) are obtained, which 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 3% by weight polyvinyl alcohol aqueous solution. A cross-linking agent ("Sumirez Resin 650" manufactured by Taoka Chemical Industry Co., Ltd.) was mixed in the obtained aqueous solution in a proportion of 1 part by weight based on 2 parts by weight of the polyvinyl alcohol powder as an adhesive solution.

Next, while continuously transporting the polarizing laminated film produced in the above (6), coating the above-mentioned adhesive aqueous solution on the polarizer layers on both sides, and then bonding the polarizer layer to the bonding surface and performing the saponification treatment. Transparent protective film [transparent protective film made of cellulose triacetate (TAC) ("KC4UY" manufactured by Konica Minolta Opto Co., Ltd., thickness 40 [mu] m]) is pressed between a pair of laminating rollers, An adhesive film made of a layer structure of TAC / polarizer layer / undercoat layer / base film / undercoat layer / polarizer layer / TAC is produced.

Then, the separation and lamination film was peeled off at the interface between the base film and the undercoat layer to obtain a film made of TAC / polarizer layer (5.8 μm) / undercoat layer / base film and an undercoat layer / polarizer layer After the polarizing plate made of (6.0 μm) / TAC, the base film was further removed from the former film to obtain another polarizing plate. In the step of peeling the base film, no defects such as cracking of the film occurred.

(8) Laminating step of adhesive

A corona discharge treatment was performed on the surface of the undercoat layer side of the obtained polarizer with a thickness of 5.8 μm, and a laminated film with a thickness of 25 μm was attached to the PET film (separation film) subjected to the release treatment. The sheet-like adhesive of the adhesive is made of a polarizing plate with an adhesive made of "separating film / adhesive / undercoat layer / polarizer layer / TAC".

(9) Preparation of evaluation samples

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, the separation film was peeled off, and the adhesive surface was bonded to the glass. This was used as an evaluation sample.

(10) Thermal shock test (HS test)

Put 24 evaluation samples in the test tank, and repeat at -40 ℃ for 30 minutes A cycle of 400 cycles of 30 minutes at 85 ° C for 30 minutes produced cracks in the direction of the absorption axis of the polarizer.

(11) Observe voids in cracks

An optical microscope (VHX-500 manufactured by KEYENCE Corporation) was used to observe the generated cracks in a penetrating manner. Among the generated cracks, there was a microbubble (microbubble) that looked like one of the cracks. This results in minute voids up to 100 μm in the absorption axis direction. The minute voids, whose length in the thickness direction is smaller than the thickness of the polarizer, are very small, and are different from the voids caused by bubbles, and are embedded in the polarizer layer. Therefore, it is difficult to find and observe such tiny bubbles by ordinary visual inspection or a microscope, but it can be observed in the fissures as described above, and can be regarded as the discoverer due to the fissures.

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

[Example 2]

A sample was produced and evaluated in the same manner as in Example 1 except that the gauge pressure of the reduced-pressure treatment of Example 1 (3) was set to -0.09 MPa. The liquid temperature after the treatment was 24.7 ° C. The obtained liquid system after the defoaming treatment is 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. For a sample made of a single-area layer film, it was confirmed that the length of the absorption axis direction was 100 μm or more, the number of voids was one, and the number of voids per unit area was 0.83 per m ² .

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

The luminous factor modified monomer transmittance (Ty) and luminous factor modified polarization (Py) of this single-area layer film were Ty: 42.5% and Py: 99.93%.

[Comparative Example 1]

When the reduced pressure defoaming treatment of (1) of Example 1 was not performed, and the polarizing laminated film was made in the same manner, the thickness of the polarizer layer on one side was 5.8 μm, and the thickness of the polarizer layer on the other side was 5.1 μm.

At this time, there were 44 voids / m ² in a plane having a thickness of 5.8 μm in a longitudinal direction with a length of 100 μm or more.

An evaluation sample was prepared and evaluated for a surface having a thickness of 5.8 μm in the same manner as in Example 1. Among the cracks generated by the thermal shock test (HS test), the observed causes were considered to be the main causes of cracks in the system cracks. There are 14 tiny gaps.

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

Thermal shock test: The number of cracks (tracks) in the micro-voids in the observed cracks that do not reach 100 μm in the direction of the absorption axis

(Industrial availability)

According to the manufacturing method of the present invention, it is possible to manufacture a polarizer having fewer bubble defects and reducing the risk of cracks, and a polarizing laminate and a polarizing plate including the polarizer. The polarizing plate including the polarizer, even when subjected to a thermal shock test that takes into consideration the temperature change when used in a liquid crystal display device, generates little bubbles thought to originate from the polyvinyl alcohol-based resin layer. (Microbubbles) caused by voids.

Claims (6)

A polarizer formed by dyeing a stretched polyvinyl alcohol-based resin layer with a dichroic pigment. The length of the polarizer in the direction of the absorption axis is 100 μm or more, and the number of voids is 0.83 / m ² or more. / m ² or less, and the thickness of the polarizer is 10 μm or less. A polarizing laminated film is provided with a polarizer described in item 1 of the scope of patent application on at least one side of a base film. A polarizing plate is formed by laminating a transparent protective film on at least one side of the polarizer described in item 1 of the scope of patent application. A method of manufacturing a polarizing laminated film, the polarizing laminated film is formed on at least one side of a base film with a polarizer layer made of a polyvinyl alcohol resin, and the polarizer layer is formed in a direction of an absorption axis. The gap having a length of 100 μm or more is 10 / m ² or less, and the thickness of the polarizer layer is 10 μm or less; the aforementioned manufacturing method includes the following steps: coating on at least one side of the base film and defoaming under reduced pressure An aqueous solution of a polyvinyl alcohol-based resin to obtain a laminated film having a resin layer composed of a polyvinyl alcohol-based resin formed on at least one side of the base film; a step of extending the laminated film to obtain an extended film; A step of forming a polarizer layer by dyeing the resin layer of the stretched film with a dichroic dye. The method for producing a polarizing laminated film according to item 4 of the scope of the patent application, wherein the aqueous solution of the polyvinyl alcohol-based resin that has been degassed under reduced pressure is degassed by reducing the gauge pressure to -0.04 MPa or less An aqueous solution of the obtained polyvinyl alcohol-based resin. A method for manufacturing a polarizing plate, comprising the steps of: and a base of a polarizer layer in a polarizing laminated film obtained by the method for manufacturing a polarizing laminated film described in item 4 or 5 of the scope of patent application. A transparent protective film is laminated on the opposite side of the material film side to obtain a laminating step of a multilayer film; and a peeling step of peeling the base film from the multilayer film.