JP2008020890A - Polarizer protective film, polarizing plate and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizer protective film which can suppress the curling on a high level, in a simple manner, to provide a polarizing plate which can suppress the curling on a high level, is less likely to cause separation even when being stuck to a liquid crystal cell and has excellent appearance, in a simple manner, and to provide a high-quality image display device using such a polarizing plate. <P>SOLUTION: The polarizer protective film is composed mainly of a cellulosic resin and has a water content of 3.1 wt.% to 4.0 wt.%. The polarizing plate has protective layers on both surface sides of a polarizer, wherein at least one side of the protective layers is a cellulosic resin layer and the cellulosic resin layer is formed by using the polarizer protective film. <P>COPYRIGHT: (C)2008,JPO&INPIT

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.

  A polarizing plate used in an image display device is typically a polarizer obtained by dyeing a polyvinyl alcohol (PVA) film with dichroic iodine or a dichroic dye, a triacetyl cellulose (TAC) film, or the like. It is manufactured by laminating a polarizer protective film.

  The polarizer protective film is likely to curl. For this reason, it becomes easy to generate | occur | produce a curl also in the polarizing plate obtained by bonding a polarizer protective film on the both surfaces side of a polarizer.

  The occurrence of curling in the polarizing plate causes various problems. For example, there is a problem that the bonding to the liquid crystal cell cannot be performed smoothly, a problem that even if the bonding to the liquid crystal cell is easily performed, and a problem that the appearance is deteriorated. Various problems as described above become more prominent as the polarizing plate is enlarged. Therefore, several techniques for obtaining a polarizing plate that suppresses the occurrence of curling as much as possible have been proposed.

  There has been proposed a technique for suppressing the occurrence of curling in a polarizing plate by bonding a polarizer protective film having a curl direction opposite to both sides of a polarizer (see Patent Document 1). However, when manufacturing a polarizing plate, it is necessary to pay attention to the curl directions of the two polarizer protective films to be bonded to both sides of the polarizer, which may make the manufacturing process complicated.

In a polarizing plate with an adhesive provided with an adhesive layer and a separator, curling of the polarizing plate is suppressed by strictly controlling the moisture content of the polarizing plate before and after the lamination of the adhesive layer and the separator. A technique has been proposed (see Patent Document 2). However, it is necessary to strictly control the moisture content of the polarizing plate both before and after lamination of the pressure-sensitive adhesive layer and the separator, and the manufacturing process may be complicated.
Japanese Patent Laid-Open No. 2004-184809 JP 2005-326531 A

  The present invention has been made to solve the above-described conventional problems, and the object of the present invention is to (1) simply provide a polarizer protective film in which the occurrence of curling is suppressed at a high level. 2) The generation of curling is suppressed at a high level, and it is difficult to peel off even when bonded to a liquid crystal cell, and a polarizing plate having an excellent appearance is simply provided. (3) High quality using such a polarizing plate To provide an image display device.

  The polarizer protective film of the present invention has a cellulose resin as a main component, and has a moisture content of 3.1 wt% to 4.0 wt%.

  In a preferred embodiment, the cellulosic resin is triacetyl cellulose.

According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate of the present invention is a polarizing plate having protective layers on both sides of the polarizer, and at least one of the protective layers is a cellulose-based resin layer, and the cellulose-based resin layer is used for protecting the polarizer of the present invention. It is formed using a film.
In a preferred embodiment, the cellulose resin layer is a triacetyl cellulose layer.
In preferable embodiment, it has a cellulose resin layer only in the one surface side of a polarizer.
In preferable embodiment, it has a layer which contains a (meth) acrylic-type resin as a main component in the surface side opposite to the surface side which has a cellulose resin layer of a polarizer.

In a preferred embodiment, at least one of the protective layers on both sides of the polarizer is laminated with the polarizer via an adhesive layer formed from a polyvinyl alcohol-based adhesive.
In a preferred embodiment, both of the protective layers on both sides of the polarizer are laminated with the polarizer via an adhesive layer formed from a polyvinyl alcohol-based adhesive.
In a preferred embodiment, the polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin and a crosslinking agent.
In a preferred embodiment, the polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm.
In a preferred embodiment, the metal compound colloid is blended at a ratio of 200 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.

  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.

  According to the present invention, it is possible to easily provide a polarizer protective film in which the occurrence of curling is suppressed at a high level without requiring a complicated manufacturing procedure. Furthermore, the occurrence of curling is suppressed at a high level, and a polarizing plate that is difficult to peel off even when attached to a liquid crystal cell and has an excellent appearance can be provided simply. In addition, a high-quality image display device using such a 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 of the present invention contains a cellulose resin as a main component. Examples of the cellulose resin include diacetyl cellulose and triacetyl cellulose, and triacetyl cellulose is preferable in terms of transparency and adhesiveness. The polarizer protective film of this invention may contain arbitrary appropriate other components in the range which does not impair the effect of this invention. The polarizer protective film of the present invention preferably contains 90% by weight or more of a cellulose resin, more preferably 95% by weight or more, further preferably 98% by weight or more, and particularly preferably 100% by weight.

  The thickness of the polarizer protective film of the present invention is preferably 20 μm to 100 μm, more preferably 30 μm to 80 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 100 μm or less, film winding is facilitated, and line speed, productivity, and controllability are facilitated.

  The polarizer protective film of the present invention has a moisture content of 3.1 wt% to 4.0 wt%. In the present invention, an effect that the occurrence of curling can be remarkably suppressed can be exhibited by the technical means of adjusting the water content of a film mainly composed of a cellulose-based resin within such a specific range. When the water content is less than 3.1% by weight or more than 4.0% by weight, curling may occur remarkably. The water content of the polarizer protective film of the present invention is preferably 3.2% by weight to 3.9% by weight, more preferably 3.3% by weight to 3.8% by weight.

  Arbitrary appropriate means may be employ | adopted as a means to adjust a moisture content rate in said specific range in the polarizer protective film of this invention. For example, the polarizer protective film is immersed in water under appropriate conditions and then dried under appropriate conditions, so that the water content is adjusted to be within the specific range described above.

  It is preferable that the polarizer protective film of the present invention is transparent and has no color. Specifically, the thickness direction retardation value Rth is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and particularly preferably −70 nm to +70 nm.

  As described above, the polarizer protective film of the present invention is mainly composed of a cellulose-based resin, and the water content is adjusted within a specific range of 3.1 wt% to 4.0 wt%. A polarizer protective film in which the occurrence of curling is suppressed at a high level is obtained.

[Polarizer]
As the polarizer that can be used in the polarizing plate of the present invention, a polarizer obtained by dyeing a polyvinyl alcohol resin film with a dichroic substance (typically iodine or a dichroic dye) and uniaxially stretching may be 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 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.

〔Polarizer〕
The polarizing plate of the present invention has protective layers on both sides of the polarizer, and at least one of the protective layers is a cellulose resin layer. That is, a cellulose resin layer may be provided on both sides of the polarizer, or a cellulose resin layer may be provided only on one side. When it has a cellulose resin layer only on one surface side, it has other protective layers other than the cellulose resin layer on the other surface side.

  One preferred embodiment of the polarizing plate of the present invention is that a cellulose-based resin layer 33 is laminated on one surface of a polarizer 31 via an adhesive layer 32 as shown in FIG. In this embodiment, a cellulose-based resin layer 33 ′ is laminated on the other surface of 31 via an adhesive layer 32 ′. Another preferred embodiment of the polarizing plate of the present invention is, as shown in FIG. 2, a cellulose resin layer 33 is laminated on one surface of a polarizer 31 via an adhesive layer 32, The other protective layer 36 is laminated on the other surface of the polarizer 31 with the adhesive layer 34 and the easy adhesion layer 35 interposed therebetween.

  The cellulose resin layer is formed using the polarizer protective film of the present invention. The cellulose-based resin layer is a resin layer containing a cellulose-based resin as a main component, and examples thereof include a resin layer mainly composed of diacetylcellulose and triacetylcellulose. Triacetylcellulose is a transparent and adhesive point. Is preferable. The said cellulose resin layer may contain arbitrary appropriate other components in the range which does not impair the effect of this invention. The cellulose resin layer preferably contains 90% by weight or more of the cellulose resin, more preferably 95% by weight or more, further preferably 98% by weight or more, and particularly preferably 100% by weight. The cellulose resin layer is particularly preferably a triacetyl cellulose layer.

  The thickness of the cellulose resin layer is preferably 20 μm to 100 μm, more preferably 30 μm to 80 μm.

  As described above, the polarizing plate of the present invention has protective layers on both sides of the polarizer, and at least one of the protective layers is a cellulose resin layer. The cellulose resin layer is formed using the polarizer protective film of the present invention having a moisture content of 3.1 wt% to 4.0 wt%. That is, the polarizing plate of the present invention is formed by bonding the polarizer protective film of the present invention to at least one of the polarizers. In the present invention, during the production of the polarizing plate, the occurrence of curling in the polarizing plate is remarkable due to the technical means of adjusting the moisture content of the polarizer protective film to be bonded to the polarizer within such a specific range. The effect of being able to be suppressed can be expressed. When the moisture content is less than 3.1% by weight or more than 4.0% by weight, curling may occur remarkably in the polarizing plate.

  As the other protective layer that can be used in the polarizing plate of the present invention, any appropriate protective layer can be adopted as long as the effects of the present invention are not impaired.

  Specific examples of the material that is the main component of such a protective layer include polyester, polyvinyl alcohol, polycarbonate, polyamide, polyimide, polyethersulfone, polysulfone, polystyrene, polynorbornene, and polyolefin. And transparent resins such as acrylics and acetates. In addition, thermosetting resins such as acrylic, urethane, acrylic urethane, epoxy, and silicone, or ultraviolet curable resins are also included. In addition to this, for example, a glassy polymer such as a siloxane polymer is also included. Moreover, the polymer film as described in Unexamined-Japanese-Patent No. 2001-343529 (WO01 / 37007) can also be used. As a material for this film, for example, a resin composition containing a thermoplastic resin having a substituted or unsubstituted imide group in the side chain and a thermoplastic resin having a substituted or unsubstituted phenyl group and nitrile group in the side chain For example, a resin composition having an alternating copolymer composed of isobutene and N-methylmaleimide and an acrylonitrile / styrene copolymer can be mentioned. The polymer film can be, for example, an extruded product of the resin composition.

  The other protective layers are preferably transparent and have no color. Specifically, the thickness direction retardation value is preferably −90 nm to +90 nm, more preferably −80 nm to +80 nm, and most preferably −70 nm to +70 nm.

  One of the preferred embodiments of the other protective layer is a layer containing a (meth) acrylic resin as a main component.

  Each of the (meth) acrylic resins may be composed of one kind of resin, or may be composed of two or more kinds of resins.

  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, (meth) acrylic acid C ₁ containing poly (meth) acrylate C _1-6 alkyl such as poly (meth) acrylate methyl as a main component (50 to 100% by weight, preferably 70 to 100% by weight). _-6 alkyl resin is mentioned, More preferably, the methyl methacrylate resin which has methyl methacrylate as a main component (50-100 weight%, Preferably 70-100 weight%) is mentioned.

  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, as the (meth) acrylic resin, (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 or a (meth) acrylic resin having a glutaric anhydride structure described in JP-A-2005-314534 may be used.

  The content of the (meth) acrylic resin in the layer containing the (meth) acrylic resin as a main component is preferably 50 to 99% by weight, more preferably 60 to 98% by weight, and still more preferably 70 to 97% by weight. %. When the content of the (meth) acrylic resin is less than 50% by weight, the high heat resistance and high transparency inherent in the (meth) acrylic resin may not be sufficiently reflected. May be inferior in mechanical strength.

  The other protective layer may contain any appropriate other component. Specifically, for example, ultraviolet absorbers, general compounding agents such as stabilizers, lubricants, processing aids, plasticizers, impact aids, phase difference reducing agents, matting agents, antibacterial agents, fungicides Etc.

  As the optical characteristics of the protective layer of the polarizer, the magnitude of the retardation in the front and thickness directions becomes a problem. Therefore, it is preferable that the other protective layer contains a retardation 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 still more preferably 20% by weight or less based on the total amount of the resin in the other resin layers. When added beyond this range, visible light is scattered and transparency is impaired, so that there is a possibility that the properties of the polarizer as a protective layer may be lacking.

  As the thickness of the other protective layer, any appropriate thickness can be adopted as long as the above preferred thickness direction retardation is obtained. Specifically, the thickness of the other protective layer is preferably 20 to 200 μm, more preferably 25 to 180 μm, and still more preferably 30 to 140 μm. When the thickness of the other protective layer is 20 μm or more, the protective layer 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 other protective layer is 200 μm or less, film winding is facilitated, and line speed, productivity, and controllability are facilitated.

  The other protective layer may be a film stretched by longitudinal stretching and / or lateral stretching. By being stretched by longitudinal stretching and / or transverse stretching, it becomes possible to impart excellent optical properties, excellent mechanical strength, and productivity and reworkability can be improved. .

  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 effect of stretching. When the longitudinal stretching ratio and the lateral stretching ratio exceed 3.0 times, stretch 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.

  The other protective layers can be produced by any appropriate method. For example, a film obtained by melt extrusion may be used as the other protective layer. As a method of forming a film by melt extrusion, specifically, a method of forming a film by supplying a resin composition as a raw material to an extruder connected to a T-die, extruding after melt-kneading, and taking it off with water cooling Can be illustrated. 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 temperature of melt extrusion can be set as appropriate, 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. Is more preferable. 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.

The other protective layer has a YI at a thickness of 80 μm, preferably 1.3 or less, more preferably 1.27 or less, still more preferably 1.25 or less, still more preferably 1.23 or less, and particularly preferably 1.20. It is as follows. 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 other protective layer has a b value (a measure of hue according to Hunter's color system) at a thickness of 80 μm, preferably less than 1.5, and 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 can measure 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 sample into 3 cm square. Moreover, a hue can be evaluated by b value according to Hunter's color system.

  The other protective layer has an in-plane retardation Δnd of preferably 3.0 nm or less, more preferably 1.0 nm or less. If the in-plane retardation Δnd exceeds 3.0 nm, there is a possibility that excellent optical characteristics may not be exhibited.

  The other protective layer has a thickness direction retardation Rth of preferably 5.0 nm or less, more preferably 3.0 nm or less. When the thickness direction retardation Rth exceeds 5.0 nm, there is a possibility that excellent optical characteristics may not be exhibited.

The other protective layer has a moisture permeability of 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 other protective layer 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.

  The other protective layer has a lower haze representing optical transparency, preferably 5% or less, more preferably 3% or less, still more preferably 1.5% or less, particularly preferably 1% or less. It is. 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 and the above-mentioned other protective layers are used for, for example, building lighting members such as windows and carport roofing materials, vehicle lighting members such as windows, greenhouses, etc. It can be used by laminating on agricultural lighting members, lighting members, display members such as front filters, etc., and it has been used for home appliances, vehicle interiors and interiors that have been conventionally coated with (meth) acrylic resin films. It can also be used by being laminated on building materials, wallpaper, decorative boards, entrance doors, window frames, baseboards, etc.

In the polarizing plate of the present invention, it is preferable that at least one of the protective layers on both sides of the polarizer is laminated with the polarizer via an adhesive layer formed from a polyvinyl alcohol-based adhesive. Moreover, it is more preferable that both of the protective layers on both sides of the polarizer are laminated with the polarizer via an adhesive layer formed from a polyvinyl alcohol-based adhesive.
In the polarizing plate of this invention, it is preferable to have an adhesive bond layer between the said polarizer and the said cellulose resin layer. Moreover, when using the said other protective layer, it is preferable to have an adhesive bond layer between the said polarizer and said other protective layer.

  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, alkylenediamines having two alkylene groups and two amino groups such as ethylenediamine, triethyleneamine and hexamethylenediamine (hexamethylenediamine 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, maleindialdehyde And 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 preferably further contains a metal compound colloid. The metal compound colloid is one in which fine particles are dispersed in a dispersion basket, and is electrostatically stabilized due to mutual repulsion of the same kind of charge of the fine particles, and has permanent stability.

  The metal compound colloid (fine particles) has an average particle size of 1 to 100 nm, preferably 1 to 50 nm. If the average particle diameter of the metal compound colloid is within the above range, the metal compound can be dispersed substantially uniformly in the adhesive layer, the adhesion between the polarizer and the protective layer can be ensured, and the obtained polarizing plate can be obtained. Can reduce nick defects. The range of the average particle diameter is considerably smaller than the wavelength range of visible light, and even if the transmitted light is scattered by the metal compound in the formed adhesive layer, the polarization characteristics are not adversely affected.

  Any appropriate colloid can be used as the metal compound colloid. For example, colloids of metal oxides such as alumina, silica, zirconia, titania; colloids of metal salts such as aluminum silicate, magnesium silicate, calcium carbonate, zinc carbonate, barium carbonate, calcium phosphate; celite, talc, clay, kaolin, etc. Mineral colloids; and the like.

  The metal compound colloid is dispersed in a dispersion medium and exists in a state of a colloid solution. As the dispersion medium, water is preferable. In addition to water, other dispersers such as alcohols can also be used.

  Any appropriate concentration can be adopted as the solid content concentration of the metal compound colloid in the colloid solution as long as the object of the present invention can be achieved. For example, 1 to 50% by weight is preferable, and 1 to 30% by weight is more preferable.

  As the metal compound colloid, a stabilizer containing an acid such as nitric acid, hydrochloric acid, or acetic acid can be used as a stabilizer.

  The metal compound colloid is electrostatically stabilized and can be classified into those having a positive charge and those having a negative charge. The metal compound colloid is a non-conductive material. Positive charge and negative charge are distinguished by the charge state of the colloidal surface charge in the solution after the adhesive preparation. The charge of the metal compound colloid can be confirmed, for example, by measuring the zeta potential with a zeta potential measuring machine. The surface charge of a metal compound colloid generally varies with pH. Therefore, the surface charge of the metal compound colloid in the present invention is influenced by the pH of the prepared adhesive solution. The pH of the adhesive solution is preferably 2 to 6, more preferably 2.5 to 5, further preferably 3 to 5, and particularly preferably 3.5 to 4.5. In the present invention, a metal compound colloid having a positive charge has a greater effect of suppressing the occurrence of nicks than a metal compound colloid having a negative charge. Examples of positively charged metal compound colloids include alumina colloids and titania colloids. Among these, alumina colloid is particularly preferable.

  The metal compound colloid is preferably blended at a ratio of 200 parts by weight or less (converted value of solid content) with respect to 100 parts by weight of the polyvinyl alcohol resin. Moreover, by setting the blending ratio of the metal compound colloid within the above range, it is possible to suppress the occurrence of nicks while ensuring the adhesion between the polarizer and the protective layer. The compounding ratio of the metal compound colloid is more preferably 10 to 200 parts by weight, further preferably 20 to 175 parts by weight, and particularly preferably 30 to 150 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. When the blending ratio of the metal compound colloid exceeds 200 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin, the ratio of the polyvinyl alcohol resin in the adhesive is decreased, which may be undesirable from the viewpoint of adhesiveness. is there. In order to effectively suppress nicks, the mixing ratio of the metal compound colloid is preferably set to the lower limit of the above range.

  The adhesive that can be used in the present invention is, for example, a resin solution containing a polyvinyl alcohol resin, and is usually used as an aqueous solution. Any appropriate concentration can be adopted as the solid concentration in the resin solution. Considering coating property and storage stability, it is preferably 0.1 to 15% by weight, more preferably 0.5 to 10% by weight. Any appropriate viscosity may be adopted as the viscosity of the resin solution. For example, the range of 1-50 mPa * s is preferable. The nick generated in the production of the polarizing plate tends to increase the generation of nicks as the viscosity of the resin solution decreases, but according to the adhesive containing the polyvinyl alcohol resin, the cross-linking agent, and the metal compound colloid, Even at a low viscosity in the range of 1 to 20 mPa · s, the occurrence of nicks can be suppressed, and the occurrence of nicks can be suppressed regardless of the viscosity of the resin solution. Polyvinyl alcohol-based resins containing acetoacetyl groups cannot be increased in polymerization degree compared to general polyvinyl alcohol-based resins, and have been used with low viscosity as described above. By containing, the generation | occurrence | production of the nick caused by the low viscosity of the resin solution can be suppressed.

  Any appropriate method can be adopted as a method for preparing the resin solution. In the case of the adhesive containing the polyvinyl alcohol resin, the cross-linking agent, and the metal compound colloid, usually, the metal compound colloid is mixed with the polyvinyl alcohol resin and the cross-linking agent mixed and appropriately adjusted in concentration. By doing so, a resin solution is prepared. In addition, when a polyvinyl alcohol resin containing an acetoacetyl group is used as the polyvinyl alcohol resin or when the amount of the crosslinking agent is large, the polyvinyl alcohol resin and the metal are considered in consideration of the stability of the solution. After mixing the compound colloid, the cross-linking agent can be mixed in consideration of the use time of the resulting resin solution. The density | concentration of the resin solution which is an adhesive agent can also be adjusted suitably after preparing a resin solution.

  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.

  In the polarizer protective film of the present invention, the side provided with the polarizer and the side provided with the polarizer of the protective layer when the other protective layer is used are subjected to an easy adhesion treatment for improving the adhesiveness. Can be applied. Examples of the easy adhesion treatment include surface treatment such as corona treatment, plasma treatment, low-pressure UV treatment, and saponification treatment.

  The side of the polarizer protective film of the present invention on which the polarizer is provided and the side of the protective layer provided with the polarizer when the other protective layer is used, the polarizer protective film and the adhesive It is preferable to form an easy-adhesion layer between the layers or between the protective layer and the adhesive layer 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 formation of the adhesive layer is preferably performed by applying the adhesive. The adhesive may be applied to the polarizer protective film and the polarizer either on the polarizer protective film or on the polarizer, or on both, and the other protective layer may be bonded to the polarizer. In doing so, it may be performed on either one of the other protective layer and the polarizer or both. After laminating the polarizer protective film or other protective layer and the polarizer, a drying step is performed to form an adhesive layer composed of a coating dry layer. 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, more preferably 0.03 to 5 μm. When the adhesive contains a metal compound colloid, the thickness of the adhesive layer is designed to be larger than the average particle diameter of the metal compound colloid.

  The polarizing plate of 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 form, other optical elements are provided on the side of the polarizer protective film of the present invention where the polarizer is not bonded, or when the other protective layer is used, on the side of the protective layer where the polarizer is not bonded. An adhesive layer for adhering to other members such as a film and a liquid crystal cell can be provided.

  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 or other protective layer 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 copolymer monomer of the acrylic pressure-sensitive 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.

  In the polarizing plate of the present invention, a cellulose resin layer is provided on at least one surface side of a polarizer, and the water content of the cellulose resin layer is adjusted within a range of 3.1 wt% to 4.0 wt%. By doing so, the occurrence of curling is suppressed at a high level, and even when bonded to a liquid crystal cell, it is difficult to peel off, and the polarizing plate has an excellent appearance.

  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.

(Image display device)
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 image display devices to which the polarizing plate of the present invention can be applied include self-luminous display devices such as electroluminescence (EL) displays, plasma displays (PD), and field emission displays (FEDs). Can be mentioned. FIG. 3 is a schematic cross-sectional view of a liquid crystal display device according to a preferred embodiment of the present invention. Although the transmissive liquid crystal display device will be described in the illustrated example, it goes without saying that the present invention is 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.

<Measurement of moisture content of polarizer protective film>
The moisture content of the film was determined by loss on drying. That is, the weights of the films (10 cm × 10 cm) obtained in Examples and Comparative Examples were measured, and then the weight after drying for 2 hours in an oven at 120 ° C. was measured. did.

<Measurement of curling amount of polarizing plate>
The obtained polarizing plate was cut out to a size of 10 cm × 10 cm, placed on the plane so that the convex side was on the lower side, and the distance of the portion farthest from the plane of the polarizing plate was defined as the curl amount.

<Measurement of the number of knick defects>
The polarizing plate was cut out so that it might become 1000 mm x 1000 mm, and the sample was produced. Under the fluorescent lamp, another polarizing plate (confirmed that there is no defect in advance) was provided on the black light, and the polarizing plate of the sample was placed thereon. The two polarizing plates were installed so that the respective absorption axes were orthogonal to each other, and in this state, the number of spots (knic defects) through which light was lost was counted.

[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 being immersed in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide and further stretched to 5.5 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 (meth) acrylic resin film]
Charge 20 parts by weight of methyl methacrylate, 80 parts by weight of acrylamide, 0.3 part by weight of potassium persulfate and 1500 parts by weight of ion-exchanged water into the reactor, and replace the reactor with nitrogen gas. The reaction was allowed to proceed at 70 ° C. until converted to a polymer. The obtained aqueous solution was used as a methyl methacrylate / acrylamide copolymer suspension. Furthermore, a solution in which 0.05 part of the above suspending agent was dissolved in 165 parts of ion-exchanged water was supplied to a stainless steel autoclave having a capacity of 5 liters and equipped with a baffle and a fiddle-type stirring blade, and the system was filled with nitrogen gas. It stirred at 400 rpm, replacing.
Next, a mixed material containing 27 parts by weight of methacrylic acid, 73 parts by weight of methyl methacrylate, 1.2 parts by weight of t-dodecyl mercaptan and 0.4 parts by weight of 2,2′-azobisisobutyronitrile was prepared. The reaction system was added with stirring. After the addition, the temperature was raised to 70 ° C., and the time when the internal temperature reached 70 ° C. was set as the polymerization start time, and the polymerization was continued for 180 minutes.
Thereafter, the reaction system was cooled, the polymer was separated, washed and dried in accordance with a normal method to obtain a bead-shaped copolymer. The polymerization rate of this copolymer was 97%, and the weight average molecular weight was 130,000. The obtained copolymer was blended with 0.2% by weight of additive (NaOCH ₃ ), and nitrogen was added from the hopper part using a twin screw extruder (TEX30 (manufactured by Nippon Steel Co., Ltd., L / D = 44.5)). Was purged at a rate of 10 L / min, and an intramolecular cyclization reaction was performed at a screw speed of 100 rpm, a raw material supply rate of 5 kg / h, and a cylinder temperature of 290 ° C. to obtain a pellet-like acrylic resin (A).
In a glass container with a condenser (capacity 5 liters), as an initial adjustment solution, 120 parts by weight of deionized water, 0.5 parts by weight of potassium carbonate, 0.5 parts by weight of dioctyl sulfosuccinate, 0.005 parts by weight of potassium persulfate After stirring in a nitrogen atmosphere, 53 parts by weight of butyl acrylate, 17 parts by weight of styrene, and 1 part by weight of allyl methacrylate (crosslinking agent) were added. These mixtures were reacted at 70 ° C. for 30 minutes to obtain a rubbery polymer. Next, a mixture of 21 parts by weight of methyl methacrylate, 9 parts by weight of methacrylic acid, and 0.005 parts by weight of potassium persulfate was continuously added at 70 ° C. over 90 minutes, and further maintained for 90 minutes. Polymerized. This polymer latex was coagulated with sulfuric acid, neutralized with caustic soda, washed, filtered and dried to obtain core-shell type acrylic elastic particles (B). The average particle size of the rubbery polymer portion of the acrylic elastic particles measured with an electron microscope was 140 nm.
80 parts by weight of acrylic resin (A) and 20 parts by weight of acrylic elastic particles (B) are blended, and using a twin screw extruder (Tex30 manufactured by Nippon Steel Co., Ltd., L / D = 44.5), screw rotation speed The mixture was kneaded at 150 rpm and a cylinder temperature of 280 ° C. to obtain a pellet-shaped acrylic resin composition (C).
The obtained acrylic resin composition (C) was vacuum-dried at 80 ° C. for 8 hours, dissolved in methyl ethyl ketone so as to have a solid content of 30% by weight, and filtered using a 1 μm cut filter. This solution was cast on a PET film through a T-die having a lip gap of 0.5 mm using a gear pump, and heat-treated in three stages of 60 ° C., 120 ° C., and 170 ° C. for 30 minutes in a hot air oven, and a thickness of 100 μm ( A (meth) acrylic resin film was obtained.

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

[Production Example 4: Preparation of polyvinyl alcohol adhesive aqueous solution (B)]
An acetoacetyl group-modified polyvinyl alcohol resin 100 parts by weight (average polymerization degree 1200, saponification degree 98.5 mol%, acetoacetylation degree 5 mol%) 50 parts by weight of methylol melamine at 30 ° C. Under temperature conditions, an aqueous solution dissolved in pure water and adjusted to a solid content concentration of 3.7% by weight was prepared. An aqueous adhesive solution (B) was prepared by adding 18 parts by weight of an aqueous colloidal alumina solution (average particle size: 15 nm, solid content concentration: 10% by weight, positive charge) to 100 parts by weight of the aqueous solution. The viscosity of the aqueous adhesive solution (B) was 9.6 mPa · s. The pH of the adhesive aqueous solution (B) was in the range of 4 to 4.5.

[Production Example 5: Preparation of aqueous solution of polyvinyl alcohol adhesive (C)]
In Production Example 4, an adhesive aqueous solution (C) was prepared in the same manner as in Production Example 4 except that the alumina colloidal aqueous solution was not used.

[Example 1]
A saponified 40 μm-thick triacetyl cellulose film (manufactured by Konica Minolta Opto Co., Ltd., trade name: KC4UY) was prepared and immersed in a water bath at 60 ° C. for 30 seconds and washed with water. Thereafter, drying was performed at a drying temperature of 30 ° C. for 10 seconds to obtain a triacetyl cellulose film (1) having a moisture content of 3.3% by weight.

[Example 2]
A triacetyl cellulose film (2) having a water content of 3.8% by weight was obtained in the same manner as in Example 1 except that air drying was performed for 30 seconds.

[Comparative Example 1]
A triacetyl cellulose film (C1) having a water content of 3.0% by weight was obtained in the same manner as in Example 1 except that drying was performed at a drying temperature of 30 ° C. for 30 seconds.

[Comparative Example 2]
A triacetylcellulose film (C2) having a water content of 2.8% by weight was obtained when the same procedure as in Example 1 was performed except that drying was performed at a drying temperature of 40 ° C. for 10 seconds.

[Comparative Example 3]
A triacetyl cellulose film (C3) having a moisture content of 2.4% by weight was obtained in the same manner as in Example 1 except that drying was performed at a drying temperature of 40 ° C. for 30 seconds.

[Comparative Example 4]
A triacetyl cellulose film (C4) having a water content of 1.9% by weight was obtained in the same manner as in Example 1 except that drying was performed at 60 ° C. for 10 seconds.

[Comparative Example 5]
A triacetylcellulose film (C5) having a water content of 1.5% by weight was obtained when the same procedure as in Example 1 was performed except that drying was performed at a drying temperature of 60 ° C. for 30 seconds.

[Comparative Example 6]
A triacetylcellulose film (C6) having a water content of 1.3% by weight was obtained when it was carried out in the same manner as in Example 1 except that drying was carried out at a drying temperature of 80 ° C. for 10 seconds.

[Comparative Example 7]
A triacetylcellulose film (C7) having a water content of 1.4% by weight was obtained when the same procedure as in Example 1 was performed except that drying was performed at a drying temperature of 80 ° C. for 30 seconds.

[Comparative Example 8]
When it carried out like Example 1 except not having dried, the triacetyl-cellulose film (C8) with a moisture content of 4.5 weight% was obtained.

Example 3
A polarizing plate (1A) having a configuration of triacetyl cellulose film (1) / polarizer / (meth) acrylic resin film was produced. Specifically, a triacetyl cellulose film (1) is obtained on one side of the polarizer obtained in Production Example 1 and a (meth) acrylic resin film is obtained on the other side of the polarizer in Production Example 3. The obtained polyvinyl alcohol-based adhesive aqueous solution (A) was used for bonding to obtain a polarizing plate (1A). The polyvinyl alcohol adhesive aqueous solution (A) was applied to a triacetyl cellulose film (1) and a (meth) acrylic resin film, respectively, and dried at 70 ° C. for 10 minutes to obtain a polarizing plate (1A). It was -1 mm when the curl amount of the obtained polarizing plate (1A) was measured. The results are shown in Table 1.

Example 4
A polarizing plate (2A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (2) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (2A) was measured and found to be 3 mm. The results are shown in Table 1.

[Comparative Example 9]
A polarizing plate (C1A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C1) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C1A) was measured and found to be -8 mm. The results are shown in Table 1.

[Comparative Example 10]
A polarizing plate (C2A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C2) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C2A) was measured, it was -10 mm. The results are shown in Table 1.

[Comparative Example 11]
A polarizing plate (C3A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C3) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C3A) was measured, it was -18 mm. The results are shown in Table 1.

[Comparative Example 12]
A polarizing plate (C4A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C4) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C4A) was measured and found to be -15 mm. The results are shown in Table 1.

[Comparative Example 13]
A polarizing plate (C5A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C5) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C5A) was measured and found to be -15 mm. The results are shown in Table 1.

[Comparative Example 14]
A polarizing plate (C6A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C6) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C6A) was measured, it was -16 mm. The results are shown in Table 1.

[Comparative Example 15]
A polarizing plate (C7A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C7) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C7A) was measured and found to be -14 mm. The results are shown in Table 1.

[Comparative Example 16]
A polarizing plate (C8A) was produced in the same manner as in Example 3 except that the triacetylcellulose film (C8) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C8A) was measured and found to be 10 mm. The results are shown in Table 1.

  Referring to Table 1, Example 3 in which the water content of the triacetyl cellulose film was adjusted within a specific range of 3.1 wt% to 4.0 wt% (the water content of the triacetyl cellulose film = 3.3 wt%). %) And Example 4 (water content of triacetyl cellulose film = 3.8% by weight), it can be seen that the occurrence of curling can be remarkably suppressed. On the other hand, when the water content of the triacetyl cellulose film is less than 3.1% by weight or more than 4.0% by weight (Comparative Examples 9 to 16), it can be seen that the curl is remarkably generated.

Example 5
A polarizing plate (1A) having a configuration of triacetyl cellulose film (1) / polarizer / (meth) acrylic resin film was produced. Specifically, a triacetyl cellulose film (1) is obtained on one side of the polarizer obtained in Production Example 1 and a (meth) acrylic resin film is obtained on the other side of the polarizer in Production Example 4. The obtained polyvinyl alcohol-based adhesive aqueous solution (B) was used for bonding to obtain a polarizing plate (1B). The polyvinyl alcohol adhesive aqueous solution (B) was applied to the triacetyl cellulose film (1) and the (meth) acrylic resin film, respectively, and dried at 70 ° C. for 10 minutes to obtain a polarizing plate (1B). The curl amount of the obtained polarizing plate (1B) was measured and found to be -1 mm. It was 0 when the number of knick defects of the obtained polarizing plate (1B) was measured. The results are shown in Table 2.

Example 6
A polarizing plate (2B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (2) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (2B) was measured and found to be 3 mm. It was 0 when the number of knic defects of the obtained polarizing plate (2B) was measured. The results are shown in Table 2.

Example 7
In Example 5, it replaced with the polyvinyl-alcohol-type adhesive aqueous solution (B) obtained by manufacture example 4, and was using the polyvinyl-alcohol-type adhesive aqueous solution (C) obtained by manufacture example 5 similarly to Example 5. To make a polarizing plate (3B). The curl amount of the obtained polarizing plate (3B) was measured and found to be 3 mm. It was 32 when the number of knick defects of the obtained polarizing plate (3B) was measured. The results are shown in Table 2.

Example 8
In Example 6, it replaced with the polyvinyl-alcohol-type adhesive aqueous solution (B) obtained by manufacture example 4, and used the polyvinyl-alcohol-type adhesive aqueous solution (C) obtained by manufacture example 5 similarly to Example 6 except having used it. To make a polarizing plate (4B). The curl amount of the obtained polarizing plate (4B) was measured and found to be 0 mm. It was 29 when the number of knick defects of the obtained polarizing plate (4B) was measured. The results are shown in Table 2.

[Comparative Example 17]
A polarizing plate (C1B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C1) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C1B) was measured and found to be -8 mm. It was 0 when the number of knick defects of the obtained polarizing plate (C1B) was measured. The results are shown in Table 2.

[Comparative Example 18]
A polarizing plate (C2B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C2) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C2B) was measured and found to be -10 mm. It was 0 when the number of knick defects of the obtained polarizing plate (C2B) was measured. The results are shown in Table 2.

[Comparative Example 19]
A polarizing plate (C3B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C3) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C3B) was measured, it was -18 mm. It was 0 when the number of knick defects of the obtained polarizing plate (C3B) was measured. The results are shown in Table 2.

[Comparative Example 20]
A triacetyl cellulose film (C4) is used instead of the triacetyl cellulose film (1), and the polyvinyl alcohol adhesive aqueous solution (C) obtained in Production Example 5 is used instead of the polyvinyl alcohol adhesive aqueous solution (B). A polarizing plate (C4B) was produced in the same manner as in Example 5 except for that. When the curl amount of the obtained polarizing plate (C4B) was measured, it was -15 mm. It was 28 when the number of nick defects of the obtained polarizing plate (C4B) was measured. The results are shown in Table 2.

[Comparative Example 21]
A polarizing plate (C5B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C5) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C5B) was measured, it was -15 mm. It was 0 when the number of nick defects of the obtained polarizing plate (C5B) was measured. The results are shown in Table 2.

[Comparative Example 22]
A polarizing plate (C6B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C6) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C6B) was measured and found to be -16 mm. It was 2 when the number of nick defects of the obtained polarizing plate (C6B) was measured. The results are shown in Table 2.

[Comparative Example 23]
A polarizing plate (C7B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C7) was used instead of the triacetylcellulose film (1). The curl amount of the obtained polarizing plate (C7B) was measured and found to be -14 mm. It was 1 when the number of knick defects of the obtained polarizing plate (C7B) was measured. The results are shown in Table 2.

[Comparative Example 24]
A polarizing plate (C8B) was produced in the same manner as in Example 5 except that the triacetylcellulose film (C8) was used instead of the triacetylcellulose film (1). When the curl amount of the obtained polarizing plate (C8B) was measured, it was 10 mm. It was 1 when the number of knick defects of the obtained polarizing plate (C8B) was measured. The results are shown in Table 2.

[Comparative Example 25]
Comparative Example 20 was the same as Comparative Example 20 except that the polyvinyl alcohol-based adhesive aqueous solution (B) obtained in Production Example 4 was used instead of the polyvinyl alcohol-based adhesive aqueous solution (C) obtained in Production Example 5. Then, a polarizing plate (C9B) was produced. The curl amount of the obtained polarizing plate (C9B) was measured and found to be -15 mm. It was 0 when the number of knic defects of the obtained polarizing plate (C9B) was measured. The results are shown in Table 2.

  The polarizer protective film and polarizing plate of the present invention can be suitably used for various image display devices (liquid crystal display devices, organic EL display devices, PDPs, etc.).

It is sectional drawing which shows an example of the polarizing plate of this invention. 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, 32' Adhesive layer 33, 33 'Cellulose resin layer 34 Adhesive layer 35 Easy adhesion layer 36 Other protective layer 40 Light guide plate 50 Light source 60 Reflector 100 Liquid crystal display device

Claims (13)

  A polarizer protective film comprising a cellulose resin as a main component and having a moisture content of 3.1 wt% to 4.0 wt%.   The polarizer protective film according to claim 1, wherein the cellulose resin is triacetyl cellulose.   It is a polarizing plate which has a protective layer on both sides of a polarizer, and at least one of the protective layers is a cellulose resin layer, and the cellulose resin layer uses the polarizer protective film according to claim 1. A polarizing plate is formed.   The polarizing plate according to claim 3, wherein the cellulose resin layer is a triacetylcellulose layer.   The polarizing plate of Claim 3 or 4 which has a cellulose resin layer only in the one surface side of a polarizer.   The polarizing plate of Claim 5 which has a layer which contains a (meth) acrylic-type resin as a main component in the surface side opposite to the surface side which has a cellulose resin layer of a polarizer.   The at least one of the protective layer which it has on both surfaces of the said polarizer is laminated | stacked with this polarizer through the adhesive bond layer formed from a polyvinyl alcohol-type adhesive agent in any one of Claim 3-6. Polarizing plate.   The polarizing plate according to claim 7, wherein both of the protective layers on both sides of the polarizer are laminated with the polarizer via an adhesive layer formed from a polyvinyl alcohol-based adhesive. .   The polarizing plate according to claim 7 or 8, wherein the polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin and a crosslinking agent.   The polarizing plate according to claim 7 or 8, wherein the polyvinyl alcohol-based adhesive contains a polyvinyl alcohol-based resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm.   The polarizing plate according to claim 10, wherein the metal compound colloid is blended at a ratio of 200 parts by weight or less with respect to 100 parts by weight of the polyvinyl alcohol resin.   The polarizing plate according to claim 3, 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 3.

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