JP4849665B2 - Polarizer protective film, polarizing plate, and image display device - Google Patents

Description

  The present invention relates to a polarizer protective film, a polarizing plate, and an image display device including at least one polarizing plate, such as a liquid crystal display device, an organic EL display device, and a PDP.

  In the liquid crystal display device, it is indispensable to dispose polarizing plates on both sides of the glass substrate on which the liquid crystal panel surface is formed because of the image forming method. Polarizers are generally bonded to both sides of a polarizer made of a polyvinyl alcohol film and a dichroic material such as iodine. A polarizer protective film using a cellulose resin film such as triacetyl cellulose is bonded to the polyvinyl alcohol film. Those bonded with an agent are used.

  Cellulose-based resin film has insufficient moisture and heat resistance, and when a polarizing plate using a cellulose-based resin film as a polarizer protective film is used at high temperature or high humidity, the performance of the polarizing plate such as degree of polarization and hue is said to decrease. There are drawbacks. Moreover, a cellulose resin film produces a phase difference with respect to incident light in an oblique direction. Such a phase difference significantly affects viewing angle characteristics as the size of liquid crystal displays increases in recent years.

  As a resin material excellent in heat resistance and optical transparency, (meth) acrylic resins such as polymethyl methacrylate are well known, and use as a polarizer protective film has been reported (for example, Patent Document 1). 2). However, the (meth) acrylic resin tends to generate a fragile layer in the vicinity of the film surface when formed into a film, and when used as a polarizer protective film, the adhesiveness with the polarizer cannot be sufficiently exhibited. For this reason, there exists a problem that a polarizer protective film and a polarizer are easy to peel.

A (meth) acrylic resin having a lactone ring structure is known as a resin having higher heat resistance, higher transparency, and higher mechanical strength than conventional (meth) acrylic resins such as polymethyl methacrylate. (See Patent Document 3). However, when the (meth) acrylic resin having this lactone ring structure is formed into a film, there is a problem that a fragile layer is more likely to be formed near the film surface than in the case of a conventional (meth) acrylic resin.
JP 2000-356714 A JP 2002-258051 A JP 2001-151814 A

  The present invention has been made in order to solve the above-described conventional problems. The object of the present invention is (1) polarized light containing (meth) acrylic resin as a main component, which has excellent adhesion to a polarizer. Providing a polarizer protective film, (2) providing a polarizing plate comprising such a polarizer protective film and a polarizer, the polarizer protective film and the polarizer being difficult to peel off, and (3) such polarized light. It is to provide a high-quality image display device using a plate.

  The polarizer protective film according to the present invention is formed by applying a solvent capable of swelling or dissolving the film to one surface of a film containing a (meth) acrylic resin as a main component.

  In a preferred embodiment, the (meth) acrylic resin is a (meth) acrylic resin having a lactone ring.

  According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate which concerns on this invention has a polarizer in the surface side formed by apply | coating the solvent which can swell or melt | dissolve this film of the polarizer protective film of this invention.

  In preferable embodiment, it has an adhesive bond layer between the said polarizer protective film and polarizer.

  In a preferred embodiment, the adhesive layer is a layer formed from a polyvinyl alcohol-based adhesive.

  In preferable embodiment, it has further an adhesive layer as at least one of outermost layers.

  According to another aspect of the present invention, an image display device is provided. The image display device of the present invention includes at least one polarizing plate of the present invention.

  ADVANTAGE OF THE INVENTION According to this invention, it is a polarizer protective film which contains (meth) acrylic-type resin as a main component, Comprising: The polarizer protective film excellent in adhesiveness with a polarizer can be provided.

  In the case of a polarizer protective film containing a conventional (meth) acrylic resin such as polymethyl methacrylate as a main component, a fragile layer is likely to be formed near the film surface when formed into a film, and sufficient adhesion to the polarizer can be exhibited. There wasn't. ADVANTAGE OF THE INVENTION According to this invention, the polarizer protective film excellent in adhesiveness with a polarizer can be provided by processing one side of the film which contains (meth) acrylic-type resin as a main component with a specific solvent. I can do it now.

  According to the present invention, a polarizing plate including the polarizer protective film and the polarizer as described above can be provided, and the polarizer protective film having excellent adhesion to the polarizer is used. The film and the polarizer are very difficult to peel off. Furthermore, according to the present invention, a high-quality image display device using the polarizing plate can be provided.

  Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.

[Polarizer protective film]
The polarizer protective film according to the present invention includes a film containing a (meth) acrylic resin as a main component.

  The (meth) acrylic resin preferably has a Tg (glass transition temperature) of 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. By including a (meth) acrylic resin having a Tg (glass transition temperature) of 115 ° C. or higher as a main component, for example, when it is finally incorporated into a polarizing plate, it tends to be excellent in durability. The upper limit value of Tg of the (meth) acrylic resin is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

Although it does not specifically limit as said (meth) acrylic-type resin, For example, poly (meth) acrylic acid ester, such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meta ) Acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester- (meth) acrylic acid copolymer, (meth) methyl acrylate-styrene copolymer (MS resin, etc.), alicyclic hydrocarbon group Polymers (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth) acrylate copolymer, etc.) and the like can be mentioned. Preferably, the poly (meth) acrylate C _1-6 alkyl such as poly (meth) acrylate methyl, more preferably methyl methacrylate as the main component (50-100 wt%, preferably 70-100 wt%). And methyl methacrylate resin.

  Specific examples of the (meth) acrylic resin include (meth) acrylic resins having a ring structure in the molecule described in, for example, Acrypet VH and Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd., and JP-A-2004-70296. Examples of the resin include high Tg (meth) acrylic resins obtained by intramolecular crosslinking or intramolecular cyclization reaction.

  In the present invention, a (meth) acrylic resin having a lactone ring structure is particularly preferred as the (meth) acrylic resin in that it has high heat resistance, high transparency, and high mechanical strength.

  Examples of the (meth) acrylic resin having a lactone ring structure include (meth) having a lactone ring structure described in JP 2000-230016 A, JP 2001-151814 A, JP 2005-146084 A, and the like. An acrylic resin is mentioned.

（一般式（１）中、Ｒ^１、Ｒ^２およびＲ^３は、それぞれ独立に、水素原子または炭素数１〜２０の有機残基を表す。なお、有機残基は酸素原子を含んでいても良い。） The (meth) acrylic resin having a lactone ring structure preferably has a lactone ring structure represented by the following general formula (1).

(In the general formula (1), R ¹ , R ² and R ³ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom. good.)

  The content ratio of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, The amount is preferably 10 to 60% by weight, particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, heat resistance, solvent resistance, and surface hardness are poor. May be sufficient. If the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, the moldability may be poor.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, the effects of the present invention may not be sufficiently exhibited.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. If the total light transmittance is less than 85%, the transparency is lowered, and there is a possibility that it cannot be used for the intended purpose.

  The content of the (meth) acrylic resin in the polarizer protective film of the present invention is preferably 50 to 99% by weight, more preferably 60 to 98% by weight, and further preferably 70 to 97% by weight. When the content of the (meth) acrylic resin in the polarizer protective film is less than 50% by weight, the high heat resistance and high transparency inherent in the (meth) acrylic resin may not be sufficiently reflected, If it exceeds 99% by weight, the mechanical strength may be inferior.

  The film containing the (meth) acrylic resin as a main component in the present invention is preferably stretched by longitudinal stretching and / or lateral stretching.

  The stretching may be stretching by only longitudinal stretching (free end uniaxial stretching) or stretching by only lateral stretching (fixed end uniaxial stretching), but the longitudinal stretching ratio is 1.1 to 3.0 times, and the transverse stretching ratio. Is preferably a sequential stretching or simultaneous biaxial stretching of 1.1 to 3.0 times. In stretching only by longitudinal stretching (free-end uniaxial stretching) and stretching only by lateral stretching (fixed-end uniaxial stretching), the film strength increases only in the stretching direction, and the strength does not increase in the direction perpendicular to the stretching direction. There is a possibility that sufficient film strength as a whole cannot be obtained. The longitudinal stretching ratio is more preferably 1.2 to 2.5 times, and still more preferably 1.3 to 2.0 times. The transverse stretching ratio is more preferably 1.2 to 2.5 times, and still more preferably 1.4 to 2.5 times. When the longitudinal draw ratio and the transverse draw ratio are less than 1.1 times, the draw ratio is too low, and there is a possibility that there is almost no stretching effect. When the longitudinal stretching ratio and the lateral stretching ratio exceed 3.0 times, stretching breakage is likely to occur due to the problem of the smoothness of the film end face.

  The stretching temperature is preferably Tg to (Tg + 30 ° C.) of the film to be stretched. If the stretching temperature is lower than Tg, the film may be broken. If the stretching temperature exceeds (Tg + 30 ° C.), the film may start to melt and paper passing may be difficult.

  Since the polarizer protective film of the present invention is stretched by longitudinal stretching and / or lateral stretching, it has excellent optical properties, is excellent in mechanical strength, and improves productivity and reworkability.

  The polarizer protective film of the present invention is formed by applying a solvent capable of swelling or dissolving the film to one surface of a film containing a (meth) acrylic resin as a main component.

  Examples of the solvent include acetone, methyl ethyl ketone, methyl isobutyl ketone, methyl-n-amyl ketone, cyclohexanone, diacetone alcohol, diisobutyl ketone, methylcyclohexanone, and other ketones, methyl acetate, ethyl acetate, ethyl lactate, butyl lactate, and ethyl benzoate. Esters such as methyl acetoacetate, ethers such as dioxolane, dioxane, methyl cellosolve and methyl carbitol, polyhydric alcohol esters such as methyl cellosolve acetate and cellosolve acetate, furans such as tetrahydrofuran and furfural, glacial acetic acid, etc. Acids, halogen hydrocarbons such as methylene chloride, ethylene dichloride, tetrachloroethane, nitromethane, nitroethane, pyridine, dimethylformamide, nitrobenzene Nitrogen compounds, sulfonic acids such as dimethyl sulfoxide and the like are suitably used. In view of drying after coating, a solvent that easily volatilizes is preferable, and specifically, a solvent having a boiling point of 200 ° C. or less is preferable.

  In the polarizer protective film of the present invention, as an embodiment in which the solvent is applied to one surface of the film, the solvent may be present on the film surface, The solvent may not be present. The state where the solvent is not present on the film surface includes, for example, a case where the solvent is volatilized by natural drying or forced drying.

  In the polarizer protective film of the present invention, as an embodiment in which the solvent is applied to one surface of the film, more specifically, for example, at least a part of the applied solvent is at least part of the film surface. Examples include a state where a part is dissolved and solidified again, a state where at least a part of the applied solvent swells at least a part of the film surface, and a state where these two states coexist. In addition, at least a part of the applied solvent may react with the film surface, or at least a part of the applied solvent may penetrate into the film surface.

  In the polarizer protective film of the present invention, a solvent capable of swelling or dissolving the film is applied to one surface of a film containing a (meth) acrylic resin as a main component, thereby providing a (meth) acrylic film. The fragile layer existing in the vicinity of the surface of the film containing the resin as a main component and the solvent act (dissolve, swell, etc.), and it is possible to suppress a decrease in adhesiveness caused by the fragile layer.

  In the polarizer protective film of the present invention, the fact that a solvent capable of swelling or dissolving the film is applied to one surface of a film containing a (meth) acrylic resin as a main component is, for example, the polarizer of the present invention. It can confirm by analyzing the component of the surface vicinity of a protective film.

In the polarizer protective film of the present invention, any appropriate amount of the solvent may be employed as long as the effect of the present invention is not impaired. Preferably, it is 0.0001-1 ml with respect to 1 cm < ² > of film surfaces to apply | coat, More preferably, it is 0.001-0.1 ml.

  In the polarizer protective film of the present invention, an ultraviolet absorber, a general compounding agent, for example, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact aid, a retardation reducing agent, a matting agent, an antibacterial agent. Agents, fungicides, etc. may be included.

  The polarizer protective film of the present invention preferably has high light transmittance, low in-plane retardation Δnd and low thickness direction retardation Rth.

  The thickness of the polarizer protective film of the present invention is preferably 20 to 200 μm, more preferably 25 to 180 μm, and further preferably 30 to 140 μm. When the thickness of the polarizer protective film is 20 μm or more, it has appropriate strength and rigidity, and handling properties are good during secondary processing such as laminating and printing. Further, the phase difference caused by the stress at the time of take-up can be easily controlled, and the film can be manufactured stably and easily. When the thickness of the polarizer protective film is 200 μm or less, film winding becomes easy, and line speed, productivity, and controllability become easy.

YI at a thickness of 80 μm of the polarizer protective film of the present invention is preferably 1.3 or less, more preferably 1.27 or less, further preferably 1.25 or less, further preferably 1.23 or less, and particularly preferably 1. 20 or less. If YI at a thickness of 80 μm exceeds 1.3, excellent optical transparency may not be exhibited. YI is obtained from tristimulus values (X, Y, Z) of colors obtained by measurement using, for example, a high-speed integrating sphere type spectral transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Research Laboratory). The following equation can be used.
YI = [(1.28X−1.06Z) / Y] × 100

  The b value (a measure of hue according to Hunter's color system) at a thickness of 80 μm of the polarizer protective film of the present invention is preferably less than 1.5, more preferably 1.0 or less. When b value is 1.5 or more, there is a possibility that excellent optical transparency may not be exhibited due to coloring of the film. In addition, b value measures a hue using a high-speed integrating-sphere type spectral transmittance measuring machine (trade name DOT-3C: manufactured by Murakami Color Research Laboratory), for example, by cutting a polarizer protective film sample into a 3 cm square. be able to. Moreover, a hue can be evaluated by b value according to Hunter's color system.

  In the polarizer protective film of the present invention, the in-plane retardation Δnd is preferably 3.0 nm or less, more preferably 1.0 nm or less. If the in-plane retardation Δnd exceeds 3.0 nm, the effects of the present invention, in particular, excellent optical characteristics may not be exhibited. The thickness direction retardation Rth is preferably 5.0 nm or less, more preferably 3.0 nm or less. When the thickness direction retardation Rth exceeds 5.0 nm, the effects of the present invention, in particular, excellent optical characteristics may not be exhibited.

In the polarizer protective film of the present invention, the moisture permeability is preferably 100 g / m ² · 24 hr or less, more preferably 60 g / m ² · 24 hr or less. If the moisture permeability exceeds 100 g / m ² · 24 hr, the moisture resistance may be inferior.

The polarizer protective film of the present invention preferably also has excellent mechanical strength. Tensile strength, in the MD direction, preferably 65N / mm ² or more, more preferably 70N / mm ² or more, more preferably 75N / mm ² or more, particularly preferably 80 N / mm ² or more, in the TD direction, preferably the 45N / mm ² or more, more preferably 50 N / mm ² or more, more preferably 55N / mm ² or more, and particularly preferably 60N / mm ² or more. The tensile elongation is preferably 6.5% or more, more preferably 7.0% or more, further preferably 7.5% or more, particularly preferably 8.0% or more in the MD direction, and preferably in the TD direction. Is 5.0% or more, more preferably 5.5% or more, still more preferably 6.0% or more, and particularly preferably 6.5% or more. When the tensile strength or tensile elongation is out of the above range, there is a possibility that excellent mechanical strength may not be exhibited.

  In the polarizer protective film of the present invention, the haze representing optical transparency is preferably as low as possible, preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, and particularly preferably 1. % Or less. When the haze is 5% or less, it is possible to visually give a good clear feeling to the film. When the haze is 1.5% or less, even when used as a lighting member such as a window, the visibility and the lighting performance are improved. Since both can be obtained, and even when used as a front plate of a display device, the display contents can be visually recognized well, and thus the industrial utility value is high.

  The polarizer protective film of the present invention may be produced by any method. For example, a raw material (resin composition) for forming a film containing a (meth) acrylic resin as a main component is extruded (T After producing a film by subjecting it to a melt extrusion method such as a die method or an inflation method), cast molding (melt casting method, etc.), calender molding, and preferably stretching the film as described above, A preferred example is a method in which a solvent capable of swelling or dissolving the film is applied to one surface of the obtained film.

  Any appropriate method can be adopted as a method of applying the solvent. For example, there is a method in which coating is performed by a coating method such as a wire bar method, a doctor blade method, or a dipping method, followed by drying naturally or forcibly.

  Extrusion molding does not require drying and scattering of the solvent in the adhesive used during processing, such as the organic solvent in the adhesive for dry lamination, as in the case of the dry lamination method. Excellent in productivity. Specifically, there can be exemplified a method of forming a film by supplying a resin composition as a raw material to an extruder connected to a T-die, and after melt-kneading, extruding, cooling with water and taking it out. The screw type of the extruder may be uniaxial or biaxial, and an additive such as a plasticizer or an antioxidant may be added.

  The extrusion molding temperature can be appropriately set, but when the glass transition temperature of the resin composition as a raw material is Tg (° C.), (Tg + 80) ° C. to (Tg + 180) ° C. is preferable, and (Tg + 100) ° C. to (Tg + 150) ° C. More preferred. If the extrusion molding temperature is too low, the resin does not have fluidity and may not be molded. If the extrusion molding temperature is too high, the resin viscosity will be low, and there may be a problem in production stability such as uneven thickness of the molded product.

  In the resin composition forming the polarizer protective film in the present invention, an ultraviolet absorber, a general compounding agent, for example, a stabilizer, a lubricant, a processing aid, a plasticizer, an impact resistance aid, a phase difference reducing agent. Matting agents, antibacterial agents, fungicides, etc. may be included.

  As an optical characteristic of the polarizer protective film, the magnitude of the retardation in the front and thickness directions becomes a problem. Therefore, it is preferable that the resin composition which forms the polarizer protective film in this invention contains the phase difference reducing agent. As the phase difference reducing agent, for example, a styrene-containing polymer such as acrylonitrile-styrene copolymer is preferable. The addition amount of the retardation reducing agent is preferably 30% by weight or less, more preferably 25% by weight or less, and further preferably 20% by weight or less with respect to the (meth) acrylic resin. When added exceeding this range, visible light is scattered or transparency is impaired, so that the properties as a polarizer protective film may be lacking.

  The polarizer protective film in this invention can be laminated | stacked and used for another base material. For example, it can be laminated by multilayer extrusion molding including an adhesive resin layer or multilayer inflation molding on a substrate such as glass, a polyolefin resin, an ethylene vinylidene copolymer serving as a high barrier layer, or polyester. If the heat-fusibility is high, the adhesive layer may be omitted.

  The polarizer protective film in the present invention is not only used for protecting the polarizer, but also, for example, a building lighting member such as a window or a carport roof material, a vehicle lighting member such as a window, an agricultural lighting member such as a greenhouse, and an illumination. It can be used by being laminated on a member, a display member such as a front filter, etc., and a housing of home appliances, vehicle interior members, interior building materials, wallpaper, It can also be used by laminating on decorative panels, entrance doors, window frames, baseboards, and the like.

〔Polarizer〕
The polarizing plate of the present invention is a polarizing plate comprising the polarizer protective film of the present invention and a polarizer, and the surface of the polarizer protective film of the present invention coated with a solvent capable of swelling or dissolving the film. Has a polarizer. One of the preferred embodiments of the polarizing plate of the present invention is that, as shown in FIG. 1, the polarizer protective film 34 of the present invention has one surface of the polarizer 31 through the adhesive layer 32 and the easy-adhesion layer 33. The other surface of the polarizer 31 is bonded to the polarizer protective film 36 through the adhesive layer 35. The polarizer protective film 36 may be the polarizer protective film of the present invention, or may be any other appropriate polarizer protective film.

  As the polarizer formed from the polyvinyl alcohol-based resin, one obtained by dyeing a polyvinyl alcohol-based resin film with a dichroic substance (typically iodine, a dichroic dye) and uniaxially stretching is used. The polymerization degree of the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is preferably 100 to 5000, and more preferably 1400 to 4000. The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any suitable method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). . The thickness of the polarizer can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is typically 5 to 80 μm.

  As a method for producing a polarizer, any appropriate method can be adopted depending on the purpose, materials used, conditions, and the like. Typically, a method is employed in which the polyvinyl alcohol-based resin film is subjected to a series of production steps including swelling, dyeing, crosslinking, stretching, washing with water, and drying steps. In each processing step except the drying step, the treatment is performed by immersing the polyvinyl alcohol-based resin film in a bath containing a solution used in each step. The order, frequency, and presence / absence of each treatment of swelling, dyeing, crosslinking, stretching, washing with water, and drying can be appropriately set according to the purpose, materials used, conditions, and the like. For example, several processes may be performed simultaneously in one process, and a specific process may be omitted. More specifically, for example, the stretching process may be performed after the dyeing process, may be performed before the dyeing process, or may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process. Further, for example, it can be suitably employed to perform the crosslinking treatment before and after the stretching treatment. Further, for example, the water washing process may be performed after all the processes, or may be performed only after a specific process.

  The swelling step is typically performed by immersing the polyvinyl alcohol resin film in a treatment bath (swelling bath) filled with water. By this treatment, dirt on the surface of the polyvinyl alcohol-based resin film and an anti-blocking agent can be washed, and unevenness such as uneven dyeing can be prevented by swelling the polyvinyl alcohol-based resin film. Glycerin, potassium iodide, or the like can be appropriately added to the swelling bath. The temperature of the swelling bath is typically about 20 to 60 ° C., and the immersion time in the swelling bath is typically about 0.1 to 10 minutes.

  The dyeing step is typically performed by immersing the polyvinyl alcohol-based resin film in a treatment bath (dye bath) containing a dichroic substance such as iodine. As the solvent used for the dye bath solution, water is generally used, but an appropriate amount of an organic solvent compatible with water may be added. The dichroic substance is typically used at a ratio of 0.1 to 1.0 part by weight with respect to 100 parts by weight of the solvent. When iodine is used as the dichroic substance, the dye bath solution preferably further contains an auxiliary agent such as iodide. This is because the dyeing efficiency is improved. The auxiliary is preferably used in a proportion of 0.02 to 20 parts by weight, more preferably 2 to 10 parts by weight, with respect to 100 parts by weight of the solvent. Specific examples of iodide include potassium iodide, lithium iodide, sodium iodide, zinc iodide, aluminum iodide, lead iodide, copper iodide, barium iodide, calcium iodide, tin iodide, and iodide. Titanium is mentioned. The temperature of the dyeing bath is typically about 20 to 70 ° C., and the immersion time in the dyeing bath is typically about 1 to 20 minutes.

  The crosslinking step is typically performed by immersing the dyed polyvinyl alcohol resin film in a treatment bath (crosslinking bath) containing a crosslinking agent. Arbitrary appropriate crosslinking agents can be employ | adopted as a crosslinking agent. Specific examples of the crosslinking agent include boron compounds such as boric acid and borax, glyoxal, and glutaraldehyde. These can be used alone or in combination. As the solvent used for the solution of the crosslinking bath, water is generally used, but an appropriate amount of an organic solvent having compatibility with water may be added. The crosslinking agent is typically used at a ratio of 1 to 10 parts by weight with respect to 100 parts by weight of the solvent. When the concentration of the crosslinking agent is less than 1 part by weight, sufficient optical properties cannot often be obtained. When the concentration of the crosslinking agent exceeds 10 parts by weight, the stretching force generated in the film during stretching increases, and the resulting polarizing plate may shrink. The solution of the crosslinking bath preferably further contains an auxiliary agent such as iodide. This is because it is easy to obtain uniform characteristics in the plane. The concentration of the auxiliary agent is preferably 0.05 to 15% by weight, more preferably 0.5 to 8% by weight. Specific examples of iodide are the same as those in the dyeing process. The temperature of the crosslinking bath is typically about 20 to 70 ° C, preferably 40 to 60 ° C. The immersion time in the crosslinking bath is typically about 1 second to 15 minutes, preferably 5 seconds to 10 minutes.

  The stretching process may be performed at any stage as described above. Specifically, it may be performed after the dyeing process, may be performed before the dyeing process, may be performed simultaneously with the swelling process, the dyeing process, and the crosslinking process, or may be performed after the crosslinking process. The cumulative draw ratio of the polyvinyl alcohol-based resin film needs to be 5 times or more, preferably 5 to 7 times, and more preferably 5 to 6.5 times. When the cumulative draw ratio is less than 5 times, it may be difficult to obtain a polarizing plate with a high degree of polarization. When the cumulative draw ratio exceeds 7 times, the polyvinyl alcohol-based resin film (polarizer) may be easily broken. Arbitrary appropriate methods may be employ | adopted as a specific method of extending | stretching. For example, when the wet stretching method is adopted, the polyvinyl alcohol-based resin film is stretched at a predetermined magnification in a treatment bath (stretching bath). As the stretching bath solution, a solution in which various metal salts, iodine, boron or zinc compounds are added to a solvent such as water or an organic solvent (for example, ethanol) is preferably used.

  The water washing step is typically performed by immersing the polyvinyl alcohol-based resin film subjected to the above-described various treatments in a treatment bath (water washing bath). An unnecessary residue of the polyvinyl alcohol-based resin film can be washed away by the water washing step. The washing bath may be pure water or an aqueous solution of iodide (for example, potassium iodide or sodium iodide). The concentration of the iodide aqueous solution is preferably 0.1 to 10% by mass. An auxiliary agent such as zinc sulfate or zinc chloride may be added to the aqueous iodide solution. The temperature of the washing bath is preferably 10 to 60 ° C, more preferably 30 to 40 ° C. The immersion time is typically 1 second to 1 minute. The water washing step may be performed only once, or may be performed a plurality of times as necessary. When implemented several times, the kind and density | concentration of the additive contained in the washing bath used for each process can be adjusted suitably. For example, the water washing step includes a step of immersing the polymer film in an aqueous potassium iodide solution (0.1 to 10% by mass, 10 to 60 ° C.) for 1 second to 1 minute, and a step of rinsing with pure water.

  Any appropriate drying method (for example, natural drying, air drying, heat drying) may be employed as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., and the drying time is typically 1 to 10 minutes. A polarizer is obtained as described above.

  In the polarizing plate of this invention, although the said polarizer and the polarizer protective film of this invention are included, it is preferable to have an adhesive bond layer between a polarizer protective film and a polarizer.

  The adhesive layer is preferably a layer formed from a polyvinyl alcohol-based adhesive. The polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin and a crosslinking agent.

  The polyvinyl alcohol-based resin is not particularly limited. For example, polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; and a saponified product of a copolymer with a monomer having copolymerizability with vinyl acetate. Modified polyvinyl alcohol obtained by acetalization, urethanization, etherification, grafting, phosphoric esterification, etc. of polyvinyl alcohol. Examples of the monomer include unsaturated carboxylic acids such as (anhydrous) maleic acid, fumaric acid, crotonic acid, itaconic acid, (meth) acrylic acid, and esters thereof; α-olefins such as ethylene and propylene, (meth) Examples include allyl sulfonic acid (soda), sulfonic acid soda (monoalkyl malate), disulfonic acid soda alkyl maleate, N-methylol acrylamide, acrylamide alkyl sulfonic acid alkali salt, N-vinyl pyrrolidone, N-vinyl pyrrolidone derivatives, and the like. . These polyvinyl alcohol resins may be used alone or in combination of two or more.

  From the viewpoint of adhesiveness, the polyvinyl alcohol-based resin preferably has an average degree of polymerization of 100 to 3000, more preferably 500 to 3000, and an average degree of saponification of preferably 85 to 100 mol%, more preferably 90. ˜100 mol%.

  As the polyvinyl alcohol resin, a polyvinyl alcohol resin having an acetoacetyl group can be used. A polyvinyl alcohol-based resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable in terms of improving the durability of the polarizing plate.

  A polyvinyl alcohol-based resin containing an acetoacetyl group is obtained by reacting a polyvinyl alcohol-based resin with diketene by a known method. For example, a method in which a polyvinyl alcohol resin is dispersed in a solvent such as acetic acid and diketene is added thereto, and a polyvinyl alcohol resin is previously dissolved in a solvent such as dimethylformamide or dioxane, and diketene is added thereto. And the like. Moreover, the method of making diketene gas or liquid diketene contact directly to polyvinyl alcohol is mentioned.

  The degree of acetoacetyl group modification of the polyvinyl alcohol resin having an acetoacetyl group is not particularly limited as long as it is 0.1 mol% or more. If it is less than 0.1 mol%, the water resistance of the adhesive layer is insufficient, which is inappropriate. The degree of acetoacetyl modification is preferably 0.1 to 40 mol%, more preferably 1 to 20 mol%. When the degree of acetoacetyl modification exceeds 40 mol%, the number of reaction points with the cross-linking agent decreases, and the effect of improving water resistance is small. The degree of acetoacetyl modification is a value measured by NMR.

  As said crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. As the crosslinking agent, a compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylene diamine, triethylene amine, hexamethylene diamine (hexamethylene diamine is preferred); tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylene propane tolylene Isocyanate adduct, triphenylmethane triisocyanate, methylene bis (4-phenylmethane triisocyanate, isophorone diisocyanate and isocyanates such as ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di Or triglycidyl ether, 1,6-hexanediol diglycidyl ether, trimethylo Epoxys such as rupropane triglycidyl ether, diglycidyl aniline, diglycidyl amine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, butyraldehyde; glyoxal, malondialdehyde, succindialdehyde, glutardialdehyde, maleidialdehyde , Dialdehydes such as phthaldialdehyde; amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensates of benzoguanamine and formaldehyde; sodium, potassium, magnesium Divalent metals such as calcium, aluminum, iron and nickel, or salts of trivalent metals and oxides thereof. Is to, melamine-based crosslinking agent is preferably, suitable in particular melamine.

  The amount of the crosslinking agent is preferably 0.1 to 35 parts by weight, more preferably 10 to 25 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. On the other hand, in order to further improve the durability, the crosslinking agent can be blended in a range of more than 30 parts by weight and 46 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin. In particular, when a polyvinyl alcohol-based resin containing an acetoacetyl group is used, it is preferable to use the crosslinking agent in an amount exceeding 30 parts by weight. Water resistance improves by mix | blending a crosslinking agent in the range of more than 30 weight part and 46 weight part or less.

  The polyvinyl alcohol-based adhesive further includes coupling agents such as silane coupling agents and titanium coupling agents, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, hydrolysis stabilizers, and the like. A stabilizer or the like can also be blended.

  The polarizer protective film of the present invention can be subjected to an easy adhesion treatment for improving adhesion to the surface in contact with the polarizer. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment.

  In the polarizer protective film of the present invention, it is preferable to form an easy adhesion layer (anchor layer) on the surface in contact with the polarizer in order to improve adhesion.

  As said easily bonding layer, the silicone layer which has a reactive functional group is mentioned, for example. The material of the silicone layer having a reactive functional group is not particularly limited. For example, an isocyanate group-containing alkoxysilanol, an amino group-containing alkoxysilanol, a mercapto group-containing alkoxysilanol, a carboxy-containing alkoxysilanol, an epoxy group-containing Examples thereof include alkoxysilanols, vinyl-type unsaturated group-containing alkoxysilanols, halogen group-containing alkoxylanols, and isocyanate group-containing alkoxysilanols, and amino silanols are preferred. Furthermore, the adhesive force can be strengthened by adding a titanium-based catalyst or a tin-based catalyst for efficiently reacting the silanol. Moreover, you may add another additive to the silicone which has the said reactive functional group. Specifically, terpene resins, phenol resins, terpene-phenol resins, rosin resins, xylene resins and other tackifiers, UV absorbers, antioxidants, heat stabilizers and other stabilizers may be used.

  The silicone layer having the reactive functional group is formed by coating and drying by a known technique. The thickness of the silicone layer is preferably 1 to 100 nm, more preferably 10 to 80 nm after drying. During coating, silicone having a reactive functional group may be diluted with a solvent. The dilution solvent is not particularly limited, and examples thereof include alcohols. The dilution concentration is not particularly limited, but is preferably 1 to 5% by weight, more preferably 1 to 3% by weight.

  The adhesive layer is formed by applying the adhesive to either side or both sides of the polarizer protective film and to either side or both sides of the polarizer. After bonding a polarizer protective film and a polarizer, a drying process is given and the adhesive bond layer which consists of an application | coating drying layer is formed. This can also be bonded after forming the adhesive layer. Bonding of a polarizer and a polarizer protective film can be performed with a roll laminator or the like. The heating and drying temperature and drying time are appropriately determined according to the type of adhesive.

  The thickness of the adhesive layer is preferably 0.01 to 10 μm, and more preferably 0.03 to 5 μm, because it is not preferable in terms of adhesiveness of the polarizer protective film if the thickness after drying becomes too thick. .

  Bonding of the polarizer protective film to the polarizer can be bonded to both sides of the polarizer on one side of the polarizer protective film.

  In addition, the polarizer protective film of the polarizer can be bonded by adhering to one side of the polarizer on one side of the polarizer protective film and bonding the cellulosic resin film to the other side.

  The cellulose resin film is not particularly limited, but triacetyl cellulose is preferable in terms of transparency and adhesiveness. The thickness of the cellulose resin film is preferably 30 to 100 μm, more preferably 40 to 80 μm. If the thickness is less than 30 μm, the film strength is lowered and workability is inferior.

  The polarizing plate according to the present invention may have an adhesive layer as at least one of the outermost layers (such a polarizing plate may be referred to as an adhesive polarizing plate). As a particularly preferred embodiment, a pressure-sensitive adhesive layer for adhering to another member such as another optical film or a liquid crystal cell can be provided on the side of the polarizer protective film where the polarizer is not adhered.

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is used as a base polymer. It can select suitably and can be used. In particular, those having excellent optical transparency such as an acrylic pressure-sensitive adhesive, exhibiting appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and being excellent in weather resistance and heat resistance can be preferably used. In particular, an acrylic pressure-sensitive adhesive made of an acrylic polymer having 4 to 12 carbon atoms is preferable.

  In addition to the above, in terms of prevention of foaming and peeling phenomena due to moisture absorption, deterioration of optical properties and liquid crystal cell warpage due to differences in thermal expansion, etc., as well as formability of liquid crystal display devices with high quality and excellent durability An adhesive layer having a low moisture absorption rate and excellent heat resistance is preferred.

  The pressure-sensitive adhesive layer is, for example, a natural or synthetic resin, in particular, a tackifier resin, a filler or pigment made of glass fiber, glass beads, metal powder, other inorganic powders, a colorant, an antioxidant. An additive to be added to the pressure-sensitive adhesive layer such as an agent may be contained.

  Moreover, the adhesive layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  The attachment of the pressure-sensitive adhesive layer can be performed by an appropriate method. For example, a pressure sensitive adhesive solution of about 10 to 40% by weight in which a base polymer or a composition thereof is dissolved or dispersed in a solvent composed of a suitable solvent alone or a mixture such as toluene and ethyl acetate is prepared. A method in which it is directly attached on a polarizing plate or an optical film by an appropriate development method such as a casting method or a coating method, or a pressure-sensitive adhesive layer is formed on a separator according to the above, and the surface is applied to a polarizer protective film. The method of transferring to is included.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of the polarizing plate as a superposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as adhesive layers with a different composition, a kind, thickness, etc. in the front and back of a polarizing plate.

  The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is preferably 1 to 40 μm, more preferably 5 to 30 μm, and particularly preferably 10 to 25 μm. When the thickness is less than 1 μm, the durability is deteriorated. When the thickness is more than 40 μm, floating or peeling due to foaming or the like is liable to occur, resulting in poor appearance.

  In order to improve the adhesion between the polarizer protective film and the pressure-sensitive adhesive layer, an anchor layer may be provided between the layers.

  As the anchor layer, an anchor layer selected from polyurethane, polyester and polymers containing an amino group in the molecule is preferably used, and polymers containing an amino group in the molecule are particularly preferably used. Polymers containing amino groups in the molecule are good because the amino groups in the molecule exhibit interactions such as reaction or ionic interaction with carboxyl groups in the adhesive and polar groups in the conductive polymer. Adhesion is ensured.

  Examples of the polymer containing an amino group in the molecule include, for example, polyethyleneimine, polyallylamine, polyvinylamine, polyvinylpyridine, polyvinylpyrrolidine, and amino-containing groups such as dimethylaminoethyl acrylate shown as a copolymerization monomer of the above-mentioned acrylic adhesive. Examples thereof include polymers of contained monomers.

  In order to impart antistatic properties to the anchor layer, an antistatic agent may be added. Antistatic agents for imparting antistatic properties include ionic surfactant systems, conductive polymer systems such as polyaniline, polythiophene, polypyrrole, and polyquinoxaline, and metal oxide systems such as tin oxide, antimony oxide, and indium oxide. In particular, a conductive polymer system is preferably used from the viewpoint of optical characteristics, appearance, antistatic effect, and stability of the antistatic effect when heated and humidified. Among these, water-soluble conductive polymers such as polyaniline and polythiophene or water-dispersible conductive polymers are particularly preferably used. This is because, when a water-soluble conductive polymer or a water-dispersible conductive polymer is used as a material for forming the antistatic layer, it is possible to suppress deterioration of the optical film substrate due to an organic solvent during the coating process.

  In the present invention, the polarizer, polarizer protective film, and the like that form the polarizing plate described above, and the pressure-sensitive adhesive layer, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, and cyanoacrylate compounds. A compound or a compound having ultraviolet absorbing ability by a method such as a method of treating with a UV absorber such as a nickel complex salt compound may be used.

  The polarizing plate of the present invention may be provided on either the viewing side or the backlight side of the liquid crystal cell or on both sides, and is not limited.

  Next, the image display apparatus of the present invention will be described. The image display device of the present invention includes at least one polarizing plate of the present invention. Here, a liquid crystal display device will be described as an example, but it goes without saying that the present invention can be applied to any display device that requires a polarizing plate. Specific examples of the image display device to which the polarizing plate of the present invention can be applied include a self-luminous display device such as an electroluminescence (EL) display, a plasma display (PD), and a field emission display (FED: Field Emission Display). Can be mentioned. FIG. 2 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. In the illustrated example, a transmissive liquid crystal display device will be described, but it goes without saying that the present invention is also applied to a reflective liquid crystal display device and the like.

  The liquid crystal display device 100 includes a liquid crystal cell 10, retardation films 20 and 20 ′ disposed across the liquid crystal cell 10, and polarizing plates 30 and 30 ′ disposed outside the retardation films 20 and 20 ′. A light guide plate 40, a light source 50, and a reflector 60 are provided. The polarizing plates 30 and 30 'are arranged so that their polarization axes are orthogonal to each other. The liquid crystal cell 10 includes a pair of glass substrates 11 and 11 ′ and a liquid crystal layer 12 as a display medium disposed between the substrates. One substrate 11 is provided with a switching element (typically a TFT) for controlling the electro-optical characteristics of the liquid crystal, a scanning line for supplying a gate signal to the switching element, and a signal line for supplying a source signal ( Neither is shown). The other glass substrate 11 ′ is provided with a color layer constituting a color filter and a light shielding layer (black matrix layer) (both not shown). The distance (cell gap) between the substrates 11 and 11 ′ is controlled by the spacer 13. In the liquid crystal display device of the present invention, the polarizing plate of the present invention described above is employed as at least one of the polarizing plates 30 and 30 '.

  For example, in the case of the TN mode, in such a liquid crystal display device 100, when no voltage is applied, the liquid crystal molecules of the liquid crystal layer 12 are arranged in a state where the polarization axis is shifted by 90 degrees. In such a state, incident light that is transmitted through only light in one direction by the polarizing plate is twisted 90 degrees by liquid crystal molecules. As described above, since the polarizing plates are arranged so that the polarization axes thereof are orthogonal to each other, the light (polarized light) reaching the other polarizing plate is transmitted through the polarizing plate. Therefore, when no voltage is applied, the liquid crystal display device 100 performs white display (normally white method). On the other hand, when a voltage is applied to such a liquid crystal display device 100, the arrangement of liquid crystal molecules in the liquid crystal layer 12 changes. As a result, the light (polarized light) that has reached the other polarizing plate cannot be transmitted through the polarizing plate, resulting in black display. An image is formed by switching such display for each pixel using an active element.

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Unless otherwise indicated, parts and percentages in the examples are based on weight.

<Mass average molecular weight>
Measurement was made in terms of polystyrene using Shodex GPC system-21H manufactured by Showa Denko K.K.

<Tg (Glass transition temperature, sometimes referred to as TG)>
The polymer is once dissolved in tetrahydrofuran, re-precipitated by adding it to excess hexane or toluene, and the precipitate taken out by filtration is dried under reduced pressure (1 mmHg (1.33 hPa), 3 hours or more). The resin obtained was measured using a DSC apparatus (DSC8230, manufactured by Rigaku Corporation).

<Dealcoholization reaction rate (lactone cyclization rate)>
The dealcoholization reaction rate was determined based on the weight loss that occurred when all hydroxyl groups were dealcoholated as methanol from the polymer composition obtained by polymerization. From the 150 ° C. before the weight reduction began in dynamic TG measurement, It calculated | required from the weight reduction by the dealcoholization reaction to 300 degreeC before decomposition | disassembly started.
That is, in the dynamic TG measurement of the polymer having a lactone ring structure, the weight reduction rate between 150 ° C. and 300 ° C. is measured, and the obtained actual weight reduction rate is defined as (X). On the other hand, from the composition of the polymer, all the hydroxyl groups contained in the polymer composition are involved in the formation of the lactone ring, so that it becomes an alcohol and is dealcoholized. (Y) is the weight loss rate calculated on the assumption that the% dealcoholization reaction has occurred. The theoretical weight reduction rate (Y) is more specifically the molar ratio of raw material monomers having a structure (hydroxyl group) involved in the dealcoholization reaction in the polymer, that is, the raw material unit in the polymer composition. It can be calculated from the content of the monomer. These values (X, Y) are calculated from the dealcoholization formula:
1- (actual weight reduction rate (X) / theoretical weight reduction rate (Y))
Substituting into, the value is obtained and expressed in%, the dealcoholization reaction rate (lactone cyclization rate) is obtained.

<Melt flow rate>
The melt flow rate was measured at a test temperature of 240 ° C. and a load of 10 kg based on JIS-K6874.

<Rework test>
Adhesive processing was performed on one side of the polarizing plate, and a test sample was applied to a glass plate. Peeling was performed in a 90 degree direction at a speed of 1 mm / sec in a diagonal direction from one corner, and the peeling position was confirmed. The determination was performed as follows.
○: Peeling at the interface between the adhesive and the glass plate ×: Peeling at the interface between the polarizer protective film and the polarizer

<Bending test>
The obtained polarizing plate was bent up and down with a bending diameter of 3 mm, and the presence or absence of peeling was confirmed. The determination was performed as follows.
○: No peeling at the interface between the polarizer protective film and the polarizer ×: There is peeling at the interface between the polarizer protective film and the polarizer

[Production Example 1: Production of polarizer]
A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, after immersing in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide and further stretching to 6.0 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. It was immersed in a 5% by weight aqueous potassium iodide solution. Then, it dried for 3 minutes in 40 degreeC oven, and obtained the 30-micrometer-thick polarizer.

[Production Example 2: Production of lactone ring-containing acrylic resin]
A 30 L reaction kettle equipped with a stirrer, a temperature sensor, a cooling pipe, and a nitrogen introduction pipe was charged with 8000 g of methyl methacrylate (MMA), 2000 g of methyl 2- (hydroxymethyl) methyl acrylate (MHMA), and 10,000 g of toluene. When the temperature was raised to 105 ° C. while refluxing nitrogen and refluxed, 10.0 g of tertiary amyl peroxyisononanoate (manufactured by Atofina Yoshitomi, trade name: Lupazole 570) was added as an initiator, and at the same time 20.0 g While a solution consisting of the above initiator and 100 g of toluene was added dropwise over 4 hours, solution polymerization was performed under reflux (about 105 to 110 ° C.), followed by further aging over 4 hours.
To the obtained polymer solution, 10 g of stearyl phosphate / distearyl phosphate mixture (manufactured by Sakai Chemicals, trade name: Phoslex A-18) was added and cyclized under reflux (about 90 to 110 ° C.) for 5 hours. A condensation reaction was performed. Subsequently, the polymer solution obtained by the cyclization condensation reaction was subjected to a vent having a barrel temperature of 260 ° C., a rotation speed of 100 rpm, a degree of vacuum of 13.3 to 400 hPa (10 to 300 mmHg), a rear vent number of 1, and a forevent number of 4 It is introduced into a type screw twin screw extruder (Φ = 29.75 mm, L / D = 30) at a processing rate of 2.0 kg / hour in terms of resin amount, and cyclization condensation reaction and devolatilization are carried out in the extruder. By extrusion, transparent lactone ring-containing acrylic resin pellets were obtained.
The lactone ring-containing acrylic resin pellet had a lactone cyclization rate of 97.0%, a mass average molecular weight of 147700, a melt flow rate of 11.0 g / 10 min, and a Tg (glass transition temperature) of 130 ° C.

[Production Example 3: Preparation of aqueous polyvinyl alcohol adhesive solution]
A polyvinyl alcohol adhesive aqueous solution prepared by adjusting an aqueous solution containing 20 parts by weight of methylolmelamine to 100 parts by weight of an acetoacetyl-modified polyvinyl alcohol resin (degree of acetylation 13%) to a concentration of 0.5% by weight Prepared.

[Example 1]
Supply the lactone ring-containing acrylic resin obtained above (with a lactone cyclization rate of 20%) to the extruder, melt and knead at 250 ° C., extrude from a T-die, and take water-cooled with a cooling roll. A film having a thickness of 100 μm was obtained. Thereafter, the film was successively stretched 1.8 times (heating temperature 140 ° C.) with a sequential biaxial extruder, followed by 2.4 times transverse stretching (heating temperature 140 ° C.) to obtain a biaxially stretched film having a thickness of 30 μm.
One side of the obtained biaxially stretched film was coated with methylene chloride using a wire bar and allowed to air dry at room temperature.
Subsequently, a solution prepared by adding 66.7 parts of isopropyl alcohol to 100 parts of a silane coupling agent (manufactured by Toray Dow Co., Ltd., trade name: APZ-6661) was applied with wire bar # 5, and 90 ° C. And dried for 2 minutes. The thickness of the anchor layer after evaporation was 50 nm.
The polyvinyl alcohol-based adhesive aqueous solution obtained above was pressure-bonded while being poured between the anchor layer side of the film and the polarizer, and dried at 70 ° C. for 10 minutes to produce a polarizing plate (1).
Table 1 shows the results of the rework test and the bending test of the polarizing plate (1).

[Example 2]
A polarizing plate (2) was produced in the same manner as in Example 1 except that ethyl acetate was used instead of methylene chloride.
Table 1 shows the results of the rework test and the bending test of the polarizing plate (2).

Example 3
A polarizing plate (3) was produced in the same manner as in Example 1 except that methyl ethyl ketone was used instead of methylene chloride.
Table 1 shows the results of the rework test and bending test of the polarizing plate (3).

Example 4
A polarizing plate (4) was produced in the same manner as in Example 1 except that methyl isobutyl ketone was used instead of methylene chloride.
Table 1 shows the results of the rework test and bending test of the polarizing plate (4).

[Comparative Example 1]
A polarizing plate (C1) was produced in the same manner as in Example 1 except that the obtained biaxially stretched film was subjected to corona treatment at a discharge amount of 133 w · min / m ² instead of coating methylene chloride.
Table 1 shows the results of the rework test and bending test of the polarizing plate (C1).

  As shown in the results of Examples 1 to 4, polarizer protection with excellent adhesion to a polarizer is achieved by treating one surface of a film containing a (meth) acrylic resin as a main component with a specific solvent. A film can be provided, and in such a polarizer protective film and a polarizing plate including the polarizer, it can be seen that the polarizer protective film and the polarizer are excellent in adhesiveness and are hardly peeled off.

It is sectional drawing which shows an example of the polarizing plate of this invention. 1 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Liquid crystal cell 11, 11 'Glass substrate 12 Liquid crystal layer 13 Spacer 20, 20' Retardation film 30, 30 'Polarizing plate 31 Polarizer 32 Adhesive layer 33 Easy adhesion layer 34 Polarizer protective film 35 Adhesive layer 36 Polarizer Protective film 40 Light guide plate 50 Light source 60 Reflector 100 Liquid crystal display device

Claims (6)

A solvent capable of swelling or dissolving the film is applied to one surface of a film containing a (meth) acrylic resin having a lactone ring structure represented by the general formula (1) as a main component. The polarizer protective film whose content rate of this lactone ring structure in the structure of the (meth) acrylic-type resin which has a structure is 5-90 weight%.

(In general formula (1), R ¹ represents a hydrogen atom, R ² represents a methyl group, and R ³ represents a methyl group. )   The polarizing plate which has a polarizer in the surface side formed by apply | coating the solvent which can swell or melt | dissolve this film of the polarizer protective film of Claim 1.   The polarizing plate of Claim 2 which has an adhesive bond layer between the said polarizer protective film and a polarizer.   The polarizing plate according to claim 3, wherein the adhesive layer is a layer formed from a polyvinyl alcohol-based adhesive.   The polarizing plate according to claim 2, further comprising a pressure-sensitive adhesive layer as at least one of the outermost layers.   An image display device comprising at least one polarizing plate according to claim 2.

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