JP2009294649A - Polarizing plate and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate that improves moisture resistance by suppressing absorption of moisture, particularly through the cut surface of a polarizer, a method for manufacturing the same, an optical film that utilizes the polarizing plate, and an image display device. <P>SOLUTION: A protective film is adhered to at least one side of the polarizer of the polarizing plate with an adhesive. The protective film has moisture permeability of 150g/m<SP>2</SP>24h or lower in a 40°C, 90% RH atmosphere. At least one edge of the polarizing plate has a cut surface. A fused material layer that continues from the cut surface of the protective film to a cut surface of the polarizer is formed so as to cover the cut surface of the polarizer. The glass transition temperature (Tg) of the protective film is greater than the glass transition temperature (Tg) of the polarizer by at least 30°C. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a polarizing plate and a method for producing the same. The present invention also relates to an optical film using the polarizing plate. Further, the present invention relates to an image display device such as a polarizing plate, a liquid crystal display device using an optical film, an organic EL display device, and a PDP.

  2. Description of the Related Art Conventionally, in a liquid crystal display device, a polarizing plate is attached to one side or both sides of a liquid crystal cell in which liquid crystal is sealed between two electrode substrates on which transparent electrodes are formed because of the image forming method. As such a polarizing plate, usually, a protective film such as a triacetyl cellulose film is provided on both sides of a polarizer obtained by adsorbing and stretching and orienting a dichroic material such as iodine or a dichroic dye on a polyvinyl alcohol film. Those bonded via a polyvinyl alcohol-based adhesive are generally used.

  In recent years, liquid crystal display devices are often used for a long time under high temperature conditions or the like due to their wide use, and liquid crystal display devices with little change in hue according to the intended use are demanded. For example, liquid crystal display devices are often used for in-vehicle devices and portable information terminals, and accordingly, the optical properties of polarizing plates are also deteriorated when left under high temperature conditions or high temperature and high humidity conditions. Reliability (durability) is not required.

  As a technique for improving the moisture resistance of the polarizing plate, instead of a triacetyl cellulose film (TAC) having a high moisture permeability, a resin film having a low moisture permeability such as a norbornene resin film is used as a protective film for the polarizer. A method for improving the moisture resistance of a polarizing plate has been proposed (see, for example, Patent Document 1). However, even in a polarizing plate using a resin film with low moisture permeability as a protective film, when the edge is cut with a blade, the end face of the polarizer is exposed as a cut surface at the time of cutting. May absorb moisture. Moreover, since partial peeling of the interface is likely to occur due to the shearing force at the time of cutting, the polarization degree may change due to moisture absorption by the polarizer from that portion.

  On the other hand, a technique of cutting a polarizing plate having a protective film with a laser is also known. Patent Document 2 discloses a polarizing plate and a resin film having a light transmittance of 80% or more and a glass transition temperature of 100 ° C. or more. A method of cutting the laminate by irradiating a laser on the resin film side of the laminate is disclosed.

JP-A-8-5836 JP 2005-189530 A

  However, in this cutting method, a highly protective film such as TAC is mainly used as a protective film for the polarizer, and since the effect of the resin film to be laminated is also great, they can be used from the cut surface of the polarizer. The effect of suppressing moisture absorption was hardly expected.

  Therefore, an object of the present invention is to provide a polarizing plate capable of improving moisture resistance by suppressing moisture absorption from a cut surface of a polarizer, and a method for producing the same. Moreover, it is providing the optical film using the polarizing plate which improved such moisture resistance, and an image display apparatus.

  As a result of intensive studies to solve the above problems, the present inventors have used a resin film with low moisture permeability as a protective film for a polarizer, and when cutting the edge by melt cutting such as a laser, The present inventors have found that a melt layer continuous from the cut surface to the cut surface of the polarizer may be formed so as to cover the cut surface, thereby completing the present invention.

That is, the polarizing plate of the present invention is a polarizing plate in which a protective film is bonded to at least one side of a polarizer via an adhesive, and the protective film has moisture permeability in an atmosphere of 40 ° C. and 90% RH. 150 g / m ² · 24 h or less, and at least one end of the polarizing plate has a cut surface, and the melt layer connected from the cut surface of the protective film to the cut surface of the polarizer is the polarizer. The protective film has a glass transition temperature (Tg) higher than the glass transition temperature (Tg) of the polarizer by 30 ° C. or more. In the present invention, the “melt layer” refers to a state in which, when a protective film or the like is melted and cut, it is partially melted and deformed to form a coating layer.

  According to the polarizing plate of the present invention, when a melt film is cut using a resin film having low moisture permeability as a protective film for the polarizer, the melt layer continuous from the cut surface of the protective film to the cut surface of the polarizer is a cut surface. In particular, moisture absorption from the cut surface of the polarizer can be suppressed and moisture resistance can be improved. In other words, the melt layer is connected from the cut surface of the protective film to the cut surface of the polarizer, so that the component with low moisture permeability covers the cut surface of the polarizer, and the gap or cut at the interface with the polarizer. From the surface, moisture absorption can be effectively suppressed. In that case, by making Tg of the said protective film 30 degreeC or more higher than Tg of a polarizer, it becomes easy to cover the cut surface of an optical film with the melt of a protective film in the case of melt cutting.

  In the above, it is preferable that the thickness of the protective film is 0.8 times to 25 times the thickness of the polarizer. When the thickness of the protective film and the thickness of the polarizer are in such a relationship, it becomes easier to cover the cut surface of the optical film with the melt of the protective film without reducing handling and productivity.

On the other hand, the method for producing a polarizing plate of the present invention is a method for producing a polarizing plate in which a protective film is laminated on at least one side of a polarizer via an adhesive, under an atmosphere of 40 ° C. and 90% RH. A step of bonding a protective film having a moisture permeability of 150 g / m ² · 24 h or less and the polarizer through an adhesive, and melting and cutting at least one end of the bonded polarizing plate, Forming a melt layer continuous from the cut surface of the protective film to the cut surface of the polarizer so as to cover the cut surface.

  According to the method for producing a polarizing plate of the present invention, a resin film having a low moisture permeability is used as a protective film for a polarizer, and when the edges are melted and cut, the cut surface of the protective film leads to the cut surface of the polarizer. Since the melt layer is formed so as to cover the cut surface, it is possible to suppress moisture absorption from the cut surface of the polarizer, and to improve moisture resistance. In other words, the melt layer is connected from the cut surface of the protective film to the cut surface of the polarizer, so that the component with low moisture permeability covers the cut surface of the polarizer, and the gap or cut at the interface with the polarizer From the surface, moisture absorption can be effectively suppressed.

  In the above, it is preferable that the glass transition temperature (Tg) of the said protective film is 30 degreeC or more higher than the glass transition temperature (Tg) of the said polarizer. By making Tg of the said protective film 30 degreeC or more higher than Tg of a polarizer, it becomes easy to cover the cut surface of an optical film with the molten material of a protective film in the case of melt cutting.

  The optical film of the present invention is an optical film in which at least one polarizing plate having the above-described effects is laminated. The image display device of the present invention is an image display device using at least one polarizing plate or optical film that exhibits the above-described effects.

Scanning electron microscope (SEM) photograph when the cut surface in the absorption axis direction of the polarizing plate obtained in Example 1 is observed from the front. Scanning electron microscope (SEM) photograph when the cut surface in the absorption axis direction of the polarizing plate obtained in Example 1 is observed from the side surface Scanning electron microscope (SEM) photograph when the cut surface in the absorption axis direction of the polarizing plate obtained in Comparative Example 2 is observed from the side surface Scanning electron microscope (SEM) photograph when the cut surface in the absorption axis direction of the polarizing plate obtained in Example 1 is observed from the front.

  In the polarizing plate of the present invention, a protective film is bonded to at least one side of a polarizer via an adhesive. The protective film should just be bonded by the single side | surface side or double-sided side of the polarizer. The protective film may have other optical functions at the same time, and may be formed by laminating other layers.

  The polarizer is not particularly limited, and various types can be used. Examples of the polarizer include hydrophilic polymers such as polyvinyl alcohol film, partially formalized polyvinyl alcohol film, and ethylene / vinyl acetate copolymer partially saponified film, and two colors such as iodine and dichroic dye. And polyene-based oriented films such as those obtained by adsorbing a functional material and uniaxially stretched, polyvinyl alcohol dehydrated products, and polyvinyl chloride dehydrochlorinated products. Among these, a polarizer composed of a polyvinyl alcohol film and a dichroic material such as iodine is preferable. When the polarizer contains a polyvinyl alcohol-based resin containing iodine, the polarizer is likely to absorb moisture, and thus the degree of polarization is likely to change. In the present invention, in particular, moisture absorption from the cut surface of the polarizer. This is particularly effective when such a polarizer is used because the moisture resistance can be improved.

Polyvinyl alcohol or a derivative thereof is used as a material for the polyvinyl alcohol film applied to the polarizer. Derivatives of polyvinyl alcohol include polyvinyl formal, polyvinyl acetal and the like, olefins such as ethylene and propylene, unsaturated carboxylic acids such as acrylic acid, methacrylic acid and crotonic acid, alkyl esters thereof, acrylamide and the like. can give. Polyvinyl alcohol having a polymerization degree of about 1000 to 10000 and a saponification degree of about 80 to 100 mol% is generally used.
The polyvinyl alcohol film may contain an additive such as a plasticizer. Examples of the plasticizer include polyols and condensates thereof, and examples thereof include glycerin, diglycerin, triglycerin, ethylene glycol, propylene glycol, and polyethylene glycol. The amount of the plasticizer used is not particularly limited, but is preferably 20% by weight or less in the polyvinyl alcohol film.

  The polyvinyl alcohol film (unstretched film) is at least subjected to uniaxial stretching treatment and iodine dyeing treatment according to a conventional method. Furthermore, boric acid treatment and iodine ion treatment can be performed. Moreover, the polyvinyl alcohol film (stretched film) subjected to the treatment is dried according to a conventional method to form a polarizer.

  The moisture content of the polarizer after drying is preferably 2.0 to 5.0% by weight, and more preferably 2.5 to 3.5% by weight. By setting the moisture content after drying within the above range, it is possible to prevent a decrease in optical properties when drying after bonding the polarizer and the protective film through an adhesive. That is, if the moisture content is too high, there is a problem that heat resistance and adhesive strength are liable to decrease, and if the moisture content is too low, there is a problem that unevenness in nicks and appearance tends to occur. By doing so, it is possible to prevent such a decrease in optical characteristics.

  In the polarizing plate of the present invention, the polarizer can contain zinc. Inclusion of zinc in the polarizer is preferable in terms of suppressing hue deterioration during heating durability. The zinc content in the polarizer is preferably adjusted so that the zinc element is contained in the polarizer in an amount of 0.002 to 2% by weight. Furthermore, it is preferable to adjust to 0.01 to 1 weight%. When the zinc content in the polarizer is within the above range, the durability improving effect is good, which is preferable for suppressing the deterioration of the hue.

As the protective film constituting the polarizing plate of the present invention, a protective film having a moisture permeability of 150 g / m ² · 24 h or less in an atmosphere of 40 ° C. and 90% RH is used. Preferably the moisture permeability of the protective film is 1~150g / m ² · 24h, more preferably from 3~120g / m ² · 24h, more preferably from 30~100g / m ² · 24h. If the moisture permeability exceeds the above range, the polarizer may fade under humidified conditions, resulting in a hue change or a decrease in polarization degree. Further, if the moisture permeability is excessively low, the pressure-sensitive adhesive may peel off during drying. Here, in this specification, the moisture permeability of the film is measured according to the moisture permeability test (cup method) of JIS Z0208, and a sample having an area of 1 m ² is transmitted in 24 hours with a relative humidity difference of 40 ° C. and 90%. Is the number of grams of water vapor.

  When the polarizing plate of the present invention has protective films on both sides of the polarizer, the protective film on one side and the protective film on the other side are the same as long as the moisture permeability requirement is satisfied. May be different. Moreover, what is necessary is just to have at least 1 layer of protective film per single side | surface, and the laminated body of 2 layers or more can also be used.

  Although the thickness of a protective film can be determined suitably, generally it is about 1-500 micrometers from points, such as workability | operativity, such as intensity | strength and handleability, and thin layer property. 1-300 micrometers is especially preferable, and 5-200 micrometers is more preferable. Since the nick tends to be easily generated as the protective film becomes thinner, the thickness of the protective film is particularly preferably 5 to 100 μm. Furthermore, it is also possible to adjust the moisture permeability appropriately by changing the thickness of the protective film.

  Examples of the material constituting the protective film include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, and moisture barrier properties. Moreover, when optical isotropy is requested | required of a protective film, it is preferable to select resin with small intrinsic birefringence. Specific examples of such thermoplastic resins include, for example, polyester resins, polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, and (meth) acrylic resins. , Norbornene resins, polyarylate resins, and mixtures thereof. In addition, thermosetting resins such as (meth) acrylic resins or ultraviolet curable resins can also be used. Among the above, in terms of moisture permeability and optical characteristics, it is preferable to use (meth) acrylic resin, polyimide resin, or norbornene resin.

  The Tg (glass transition temperature) of the (meth) acrylic resin is preferably 100 ° C. or higher, more preferably 105 ° C. or higher, further preferably 110 ° C. or higher, and particularly preferably 115 ° C. or higher. When Tg is within the above range, a polarizing plate having excellent heat resistance can be produced. Moreover, although the upper limit of Tg of the said (meth) acrylic-type resin is not specifically limited, From a viewpoint of a moldability etc., it is preferable that it is 150 degrees C or less.

Any appropriate (meth) acrylic resin can be adopted as the (meth) acrylic resin as long as the effects of the present invention are not impaired. For example, poly (meth) acrylic acid ester such as polymethyl methacrylate, methyl methacrylate- (meth) acrylic acid copolymer, methyl methacrylate- (meth) acrylic acid ester copolymer, methyl methacrylate-acrylic acid ester -(Meth) acrylic acid copolymer, (meth) acrylic acid methyl-styrene copolymer (MS resin, etc.), copolymer having an aliphatic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate-norbornyl methacrylate copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. Among these, more preferred is a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight). Specific examples of these (meth) acrylic resins include, for example, Acrypet VH, Acrypet VRL20A manufactured by Mitsubishi Rayon Co., Ltd.

  Moreover, it is also possible to use what contains the (meth) acrylic-type resin which has a lactone ring structure. Examples of the (meth) acrylic resin having a lactone ring structure include JP 2000-230016, JP 2001-151814, JP 2002-120326, JP 2002-254544, and JP 2005. No. 146084, JP-A-2006-171464, and the like.

As the polyimide resin, for example, a polymer film formed from a resin composition as described in JP-A-2001-343529 (WO01 / 37007) can be used. More specifically, it is a mixture of a thermoplastic resin having a substituted imide group or an unsubstituted imide group in the side chain and a thermoplastic resin having a substituted phenyl group or an unsubstituted phenyl group and a cyano group in the side chain. Specific examples include a resin composition having an alternating copolymer composed of isobutene and N-methylenemaleimide and an acrylonitrile / styrene copolymer tight.
Norbornene-based resin is a general generic name for resins obtained from cyclic olefins such as norbornene, tetracyclododecene, and derivatives thereof. For example, JP-A-3-14882, JP-A-3-122137 and the like Are listed. Specifically, ring-opening polymers of cyclic olefins, addition polymers of cyclic olefins, random copolymers of cyclic olefins and α-olefins such as ethylene and propylene, and these are modified with unsaturated carboxylic acids or their derivatives. Examples of such graft-modified products can be given. Furthermore, these hydrides are mentioned. Examples of the products include ZEONEX and ZEONOR manufactured by Nippon Zeon, Arton manufactured by JSR, and TOPAS manufactured by TICONA.

  The protective film may contain one or more arbitrary appropriate additives. Examples of the additive include other resins, ultraviolet absorbers, antioxidants, lubricants, plasticizers, mold release agents, anti-coloring agents, flame retardants, nucleating agents, antistatic agents, pigments, and coloring agents. . The content of the thermoplastic resin in the protective film is preferably 50 to 100% by weight, more preferably 50 to 99% by weight, still more preferably 60 to 98% by weight, and particularly preferably 70 to 97% by weight. When content of the said thermoplastic resin in a protective film is 50 weight% or less, the high transparency etc. which a thermoplastic resin originally has may not fully be expressed.

  As the protective film, the cell-side protective film may have a retardation function for viewing angle compensation, and the opposite side of the cell-side protective film may or may not have a phase difference.

  The surface of the protective film that adheres to the polarizer can be subjected to an easy adhesion treatment. Examples of the easy adhesion treatment include dry treatment such as plasma treatment and corona treatment, chemical treatment such as alkali treatment (saponification treatment), and coating treatment for forming an easy adhesion layer. Among these, a coating treatment or an alkali treatment for forming an adhesive layer is preferable. Various easily adhesive materials such as polyol resin, polycarboxylic acid resin, and polyester resin can be used for forming the easily adhesive layer. Note that the thickness of the easy-adhesion layer is usually about 0.001 to 10 μm, more preferably about 0.001 to 5 μm, and particularly preferably about 0.001 to 1 μm.

  The surface of the protective film to which the polarizer is not adhered may be subjected to a treatment for the purpose of hard coat layer, antireflection treatment, antisticking, diffusion or antiglare.

  The adhesive constituting the polarizing plate of the present invention is not particularly limited as long as it is optically transparent, and water-based, solvent-based, hot-melt-based, and radical-curing types are used. A radical curable adhesive is preferred.

  Although it does not specifically limit as a water-system adhesive agent which forms an adhesive bond layer, For example, a vinyl polymer type | system | group, a gelatin type, a vinyl type latex type, a polyurethane type, an isocyanate type, a polyester type, an epoxy type etc. can be illustrated. Such an adhesive layer composed of an aqueous adhesive can be formed as an aqueous solution coating / drying layer, etc., but when preparing the aqueous solution, a catalyst such as a crosslinking agent, other additives, and an acid can be used as necessary. Can be blended. As the water-based adhesive, an adhesive containing a vinyl polymer is preferably used, and the vinyl polymer is preferably a polyvinyl alcohol resin. The polyvinyl alcohol-based resin can contain a water-soluble crosslinking agent such as boric acid, borax, glutaraldehyde, melamine, or oxalic acid. In particular, when a polyvinyl alcohol polymer film is used as the polarizer, it is preferable from the viewpoint of adhesiveness to use an adhesive containing a polyvinyl alcohol resin. Furthermore, an adhesive containing a polyvinyl alcohol-based resin having an acetoacetyl group is more preferable from the viewpoint of improving durability.

  In order to improve the durability, a polyvinyl alcohol resin containing an acetoacetyl group is used. Also in this case, the crosslinking agent is used in the range of about 4 to 60 parts by weight, preferably about 10 to 55 parts by weight, and more preferably 20 to 50 parts by weight, as described above, with respect to 100 parts by weight of the polyvinyl alcohol resin. Is preferred. When the amount of the crosslinking agent is too large, the reaction of the crosslinking agent proceeds in a short time and the adhesive tends to gel. As a result, the pot life as an adhesive is extremely shortened, making industrial use difficult. From this point of view, the blending amount of the crosslinking agent is used in the above blending amount. However, since the resin solution of the present invention contains the metal compound colloid, the blending amount of the crosslinking agent is large as described above. Even if it exists, it can be used with good stability.

  As the polarizing plate adhesive of the present invention, a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle size of 1 to 100 nm is preferably used. The resin solution is usually used as an aqueous solution. The concentration of the resin solution is not particularly limited, but is 0.1 to 15% by weight, preferably 0.5 to 10% by weight in consideration of coating properties and storage stability.

  The metal compound colloid is one in which fine particles are dispersed in a dispersion medium, and is electrostatically stabilized due to mutual repulsion of the same kind of charge of the fine particles, and has permanent stability. The average particle diameter of the metal compound colloid (fine particles) is 1 to 100 nm. When the average particle diameter of the colloid is within the above range, the metal compound can be dispersed substantially uniformly in the adhesive layer, the adhesiveness can be ensured, and the nick can be suppressed. 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. The average particle size of the metal compound colloid is preferably 1 to 100 nm, more preferably 1 to 50 nm.

  Although the viscosity of the resin solution which is an adhesive for polarizing plates is not particularly limited, those having a range of 1 to 50 mPa · s are used. The nick generated in the production of the polarizing plate tends to increase as the viscosity of the resin solution decreases. However, according to the polarizing plate adhesive of the present invention, a range of 1 to 20 mPa · s can be obtained. Even in the low viscosity range, the occurrence of nicks can be suppressed, and the occurrence of nicks can be suppressed regardless of the viscosity of the resin solution. A polyvinyl alcohol resin containing an acetoacetyl group cannot be increased in polymerization degree compared to a general polyvinyl alcohol resin and has been used at a low viscosity as described above. Even when a polyvinyl alcohol-based resin containing an acetyl group is used, the occurrence of nicks caused by the low viscosity of the resin solution can be suppressed.

  Examples of the radical curable adhesive include various active energy ray curable types such as an electron beam curable type and an ultraviolet ray curable type, and a thermosetting type. preferable.

  Examples of the curable component include a compound having a (meth) acryloyl group and a compound having a vinyl group. These curable components may be monofunctional or bifunctional or higher. Moreover, these curable components can be used individually by 1 type or in combination of 2 or more types. As these curable components, for example, compounds having a (meth) acryloyl group are suitable. For example, various epoxy (meth) acrylates, urethane (meth) acrylates, polyester (meth) acrylates, and various (meth) acrylates. Examples thereof include acrylate monomers.

  When the curable component is used, a polarizing plate having a small dimensional change can be produced, so that it is possible to easily cope with an increase in the size of the polarizing plate, and it is possible to suppress the production cost from the viewpoint of yield and number. Further, since the polarizing plate obtained in the present invention has good dimensional stability, it is possible to suppress the occurrence of unevenness in the image display device due to the external heat of the backlight.

  In addition, the adhesive for polarizing plate includes various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, plasticizers, leveling agents, foaming inhibitors, antistatic cracks, hydrolysis stabilizers, and other stabilizers. A stabilizer such as can also be blended. Further, the metal compound colloid and the metal compound filler in the present application are non-conductive materials, but may contain fine particles of a conductive substance. In addition, examples of additives include sensitizers that increase the curing speed and sensitivity by electron beams typified by carbonyl compounds, coupling agents such as silane coupling agents and titanium coupling agents, and adhesives typified by ethylene oxide. Accelerators, additives that improve wettability with the transparent protective film, acryloxy group compounds, hydrocarbons (natural and synthetic resins), and the like.

The polarizing plate of the present invention is produced by bonding the polarizer and the protective film together using the adhesive. In other words, the method for producing a polarizing plate of the present invention is a method for producing a polarizing plate in which a protective film is laminated on at least one side of a polarizer via an adhesive, under an atmosphere of 40 ° C. and 90% RH. A step of bonding a protective film having a moisture permeability of 150 g / m ² · 24 h or less and the polarizer through an adhesive is provided. In the obtained polarizing plate, a protective film is provided on one or both sides of the polarizer via an adhesive layer formed of the polarizing plate adhesive.

  Application | coating of the said adhesive agent may be performed to any of a protective film and a polarizer, and may be performed to both. The application of the adhesive is preferably performed so that the thickness of the adhesive layer after drying is about 10 to 300 nm. The thickness of the adhesive layer is more preferably from 10 to 200 nm, and even more preferably from 20 to 150 nm, from the viewpoint of obtaining a uniform in-plane thickness and sufficient adhesive strength. As described above, the thickness of the adhesive layer is preferably designed to be larger than the average particle diameter of the metal compound colloid contained in the polarizing plate adhesive.

  The method of adjusting the thickness of the adhesive layer is not particularly limited, and examples thereof include a method of adjusting the solid content concentration of the adhesive solution and an adhesive application device. The method for measuring the thickness of the adhesive layer is not particularly limited, but cross-sectional observation measurement using SEM (Scanning Electron Microscopy) or TEM (Transmission Electron Microscopy) is preferably used. The application operation of the adhesive is not particularly limited, and various means such as a roll method, a spray method, and an immersion method can be employed.

  After applying the adhesive, the polarizer and the protective film are bonded together using a roll laminator or the like. In the method for producing a polarizing plate of the present invention, as described above, the moisture content of the polarizer used in the bonding step is preferably 12 to 31% by weight, and preferably 20 to 27% by weight. More preferred. By setting the moisture content within the above range, it is possible to prevent the heat resistance from decreasing, the adhesive strength decreasing nick and the appearance unevenness.

  Furthermore, the polarizing plate of the present invention is preferably dried at an appropriate drying temperature after the protective films are bonded to both sides of the polarizer. From the viewpoint of optical properties, the drying temperature is preferably 90 ° C. or lower, more preferably 85 ° C. or lower, and further preferably 80 ° C. or lower. Moreover, although there is no minimum in drying temperature, when the efficiency and practicality of a process are considered, it is preferable that it is 50 degreeC or more. In addition, the drying temperature can be increased in stages within the above temperature range.

  In the polarizing plate of the present invention, at least one end of the polarizing plate has a cut surface, and a melt layer continuous from the cut surface of the protective film to the cut surface of the polarizer covers the cut surface of the polarizer. It is formed as follows. Such a polarizing plate can be suitably produced by the production method of the present invention. That is, in the manufacturing method of the present invention, at least one end side of the bonded polarizing plate is melted and cut, so that the melt layer continuous from the cut surface of the protective film to the cut surface of the polarizer is converted into a polarizer. A step of covering the cut surface. In the present invention, the melt layer only needs to cover a part of the cut surface of the polarizer, but it preferably covers at least the interface portion between the protective film and the polarizer. What covers the whole is more preferable. Examples of the melt cutting method include laser, heat cut, and heat ray cut.

The laser used for cutting is not particularly limited, and examples thereof include a CO ₂ laser, a YAG laser, and a semiconductor laser. The kind of laser can be freely selected according to the film used for the polarizing plate to be cut. In particular, a polarizer and a protective film having a large light absorption are preferably used. Thereby, in addition to being able to improve a cutting speed, since a film can be heated more than melting | fusing point, the edge part of a polarizer can be covered with the melt of a protective film.

In general, in the case of a UV laser such as an excimer laser, the energy of a photon increases, so that chemical decomposition (ablation) of the film tends to occur and the melt layer tends to be difficult to form. In contrast, infrared lasers such as CO ₂ lasers, YAG lasers, and semiconductor lasers are less prone to decomposition reactions, and the laser light is absorbed by the optical film described above, converted into molecular vibrational energy and rotational energy, and further heat energy. Since the film is melted and cut, the melt layer generated by melting is easily formed. The type of laser is appropriately selected from those suitable for the absorption wavelength of the optical film.

Due to such a mechanism, the CO ₂ laser cutting device is provided with an assist gas supply mechanism for removing the melt during cutting. In the present invention, the thickness or the like of the formed melt layer can be adjusted also by the supply speed of the assist gas. If the supply speed of the assist gas is too large, the thickness of the melt layer becomes thin. The covering state of the cut surface by the layer tends to deteriorate. In addition, if the heating temperature at the time of laser irradiation is too high, the viscosity of the melted resin is further reduced, and the thickness of the melt layer is likely to be thinned. It is preferable to set it low.
In the present invention, from the viewpoint as described above, it is preferable that the power density of the laser is 30 to 1,000 / mm ^2, more preferably 50~800W / mm ^2. Such an output density is determined by the laser irradiation output and the irradiation diameter. The laser irradiation output is, for example, 10 W to 800 W, and the laser irradiation diameter is, for example, 50 to 500 μmφ. The laser irradiation diameter can be adjusted using a condensing lens or the like.

  Further, when the laser output density is lowered, it is necessary to secure a laser irradiation amount per unit time to some extent, and this laser irradiation amount can be adjusted by a feed rate at the time of cutting. In the present invention, the feed rate when cutting with the laser is preferably 10 to 100 m / min from the viewpoint of improving the covering state of the cut surface by the melt layer with appropriate energy. More preferably, it is 60 m / min.

  In the present invention, it is preferable to supply an assist gas for removing the melt at the time of cutting, and the supply speed can be adjusted by the gas pressure at the time of supply. The gas pressure at the time of supply is preferably 0.05 to 20 MPa, more preferably 0.1 to 10 MPa. In this case, for example, the nozzle diameter can be about 2.5 mm. The assist gas is preferably an inert gas such as nitrogen, argon or xenon from the viewpoint of suppressing a chemical reaction with the melt.

  Cutting with a laser may be performed with a single irradiation or a plurality of irradiations. However, from the viewpoint of improving the continuity and coverage of the melt layer, it is preferable to perform the cutting with a single irradiation. .

  The formed melt layer is preferably formed mainly from a melt of a protective film from the viewpoint of suppressing moisture absorption from the cut surface of the polarizer and improving moisture resistance. Such a melt layer can be formed by melt-cutting (for example, laser irradiation) from the protective film side.

  In order to cover the cutting of the optical film with the melt of the protective film, the thickness of the protective film needs to be thick enough for the melt to cover the cut surface with respect to the thickness of the polarizer. However, when the thickness of the protective film is too thick, the cutting property is lowered, the thickness of the laminated optical film is too thick, and handling and productivity are lowered. For this reason, in order to cover a cut surface with the melt of a protective film, Preferably it is 0.8 to 25 times of polarizer thickness, More preferably, it is 1 to 5 times. Furthermore, when handling is considered, the thickness of the protective film is preferably 20 μm or more.

  Further, since the melt covers the cut surface, the glass transition temperature (Tg) of the protective film and the polarizer is an important factor. The Tg of the protective film is preferably a material higher by 30 ° C. than the Tg of the polarizer. When the Tg of the polarizer is lower than that of the protective film at the time of cutting, the film is cut and contracted before the protective film, but when the Tg of the protective film is 30 ° C. higher than the Tg of the polarizer, the protective film is higher than the polarizer. However, the melt of the protective film that has flowed later can cover the cut surface without any pinholes. That is, the Tg of the polymer has a certain degree of correlation with its melting point (in the case of a crystalline polymer) and flow initiation temperature (in the case of an amorphous polymer), and the difference in Tg between the polymers is 30 ° C. If it becomes above, even if both crystallinity differs, the starting temperature in the case of fusion | melting and fluidization will hardly reverse. For this reason, the protective film and the Tg of the polarizer as described above are important factors.

  Furthermore, the melt viscosity of the protective film is also an important factor. If the melt viscosity is too high, the cut surface is solidified before the melt covers it. On the other hand, if the melt viscosity is too low, the melt flows and the cut surface cannot be covered with the melt. For this reason, it is necessary to make it the melt viscosity suitable for covering the cut surface of a film. However, since the melt viscosity changes depending on the temperature, the protective film can be melted by adjusting the laser power, irradiation diameter, laser feed rate during cutting, assist gas pressure, and room temperature as appropriate under the above conditions. The object can cover the film cross section.

  In addition, the affinity between the melt of the protective film and the polarizer and the surface tension are also necessary elements for covering the cut surface, and the protective film described above is suitable including the above reasons.

  When heat cut is used for melt cutting, a polarizing plate or an optical film can be cut by heating a blade such as a plate blade, a round blade, or a Thomson blade.

  The temperature of the blade is preferably equal to or higher than the melting point in order to melt and cover the cut surface of the optical film. Even when heat cutting is performed for the same reason as laser cutting, a material having a Tg of 30 ° C. higher than the Tg of the polarizer is preferable. For these reasons, the temperature of the blade during heat cutting is preferably 250 ° C. or higher, more preferably 300 ° C. or higher.

  When the contact time between the blade and the film is too short, the end face cannot be covered. If the contact time is too long, the molten protective film flows down or the productivity is lowered, which is not preferable. Therefore, the contact time between the blade and the film is preferably 0.05 seconds or more and 1 second or less.

  When hot wire cutting is used for melt cutting, the polarizing plate and the optical film can be cut by a method of generating heat by energizing a linear resistor such as a nichrome wire.

  For the same reason when the heat ray is cut, a material having a Tg of the protective film higher than that of the polarizer by 30 ° C. or more is preferable. As for the temperature of heat ray cut, 800 ° C or more is preferred. Moreover, since the contact time is cut at a temperature much higher than that of the heat cut, the cut surface can be covered with the melt even in a considerably short time. For this reason, the contact time is preferably 0.2 seconds or less.

  As shown in FIG. 1, the melt layer once formed on almost the entire cut surface may be partially broken due to contraction of the polarizer or the like. In order to prevent this, the thickness of the melt layer to be formed should be more than a certain value, a polarizer with a low moisture content should be selected, the thickness of the polarizer protective film can be increased, or a highly elastic protective film can be used. It is effective to do.

  The shape of the polarizing plate at the time of cutting is not particularly limited, but is generally quadrangular, and may be cut in the absorption axis direction and the polarization axis direction of the polarizing plate. In the present invention, the laser cutting is performed on at least one edge, but it is preferable to perform the cutting on the absorption axis direction, the polarization axis direction, or both.

  Furthermore, the polarizing plate of the present invention can be used as an optical film laminated with another optical layer in practical use. The optical layer is not particularly limited. For example, for forming a liquid crystal display device such as a reflection plate, a semi-transmission plate, a retardation plate (including wavelength plates such as 1/2 and 1/4), and a viewing angle compensation film. One or more optical layers that may be used can be used. In particular, a reflective polarizing plate or a semi-transmissive polarizing plate in which a polarizing plate or a semi-transmissive reflecting plate is further laminated on the polarizing plate of the present invention, an elliptical polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on the polarizing plate. A wide viewing angle polarizing plate obtained by further laminating a viewing angle compensation film on a plate or a polarizing plate, or a polarizing plate obtained by further laminating a brightness enhancement film on the polarizing plate is preferable.

  A reflective polarizing plate is a polarizing plate provided with a reflective layer, and is used to form a liquid crystal display device or the like that reflects incident light from the viewing side (display side). Such a light source can be omitted, and the liquid crystal display device can be easily thinned. The reflective polarizing plate can be formed by an appropriate method such as a method in which a reflective layer made of metal or the like is attached to one surface of the polarizing plate via a transparent protective layer or the like as necessary.

  The semi-transmissive polarizing plate can be obtained by using a semi-transmissive reflective layer such as a half mirror that reflects and transmits light with the reflective layer. A transflective polarizing plate is usually provided on the back side (backlight side) of a liquid crystal cell, and reflects incident light from the viewing side (display side) when a liquid crystal display device is used in a relatively bright atmosphere. In a relatively dark atmosphere, a liquid crystal display device of a type that displays an image using a built-in light source such as a backlight built in the back side of the transflective polarizing plate can be formed. In other words, the transflective polarizing plate is useful for forming a liquid crystal display device of a type that can save energy of using a light source such as a backlight in a bright atmosphere and can be used with a built-in light source even in a relatively dark atmosphere. It is.

  An elliptically polarizing plate or a circularly polarizing plate in which a retardation plate is further laminated on a polarizing plate will be described. A phase difference plate or the like is used when changing linearly polarized light to elliptically polarized light or circularly polarized light, changing elliptically polarized light or circularly polarized light to linearly polarized light, or changing the polarization direction of linearly polarized light. In particular, a so-called quarter-wave plate (also referred to as a λ / 4 plate) is used as a retardation plate that changes linearly polarized light into circularly polarized light or changes circularly polarized light into linearly polarized light. A half-wave plate (also referred to as a λ / 2 plate) is usually used when changing the polarization direction of linearly polarized light.

  The elliptical polarizing plate and the reflective elliptical polarizing plate are obtained by laminating a polarizing plate or a reflective polarizing plate and a retardation plate in an appropriate combination. Such an elliptically polarizing plate or the like can also be formed by sequentially laminating them sequentially in the manufacturing process of the liquid crystal display device so as to be a combination of a (reflection type) polarizing plate and a retardation plate. An optical film such as a polarizing plate has an advantage that it can improve the production efficiency of a liquid crystal display device and the like because of excellent quality stability and lamination workability.

  An adhesive layer for adhering to other members such as a liquid crystal cell may be provided on the polarizing plate described above or an optical film in which at least one polarizing plate is laminated. The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, an acrylic polymer, silicone-based polymer, polyester, polyurethane, polyamide, polyether, fluorine-based or rubber-based polymer is appropriately selected. 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, heat resistance and the like can be preferably used.

  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 adhesive layer is, for example, natural or synthetic resins, in particular, tackifier resins, fillers or pigments made of glass fibers, glass beads, metal powders, other inorganic powders, colorants, antioxidants, etc. It may contain an additive to be added to the adhesive layer. Moreover, the adhesion layer etc. which contain microparticles | fine-particles and show light diffusibility may be sufficient.

  Attachment of the adhesive layer to one or both sides of the polarizing plate or the optical film 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 an appropriate 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 an adhesive layer is formed on a separator according to the above, and this is applied to a polarizing plate or an optical film. The method of moving up is mentioned.

  The pressure-sensitive adhesive layer can be provided on one side or both sides of a polarizing plate or an optical film as a superimposed layer of different compositions or types. Moreover, when providing in both surfaces, it can also be set as the adhesion layers of a different composition, a kind, thickness, etc. in the front and back of a polarizing plate or an optical film. The thickness of the pressure-sensitive adhesive layer can be appropriately determined according to the purpose of use and adhesive force, and is generally 1 to 500 μm, preferably 5 to 200 μm, particularly preferably 10 to 100 μm.

  On the exposed surface of the adhesive layer, a separator is temporarily attached and covered for the purpose of preventing contamination until it is put to practical use. Thereby, it can prevent contacting an adhesion layer in the usual handling state. As the separator, except for the above thickness conditions, for example, a suitable thin leaf body such as a plastic film, rubber sheet, paper, cloth, non-woven fabric, net, foam sheet, metal foil, laminate thereof, and the like, silicone type or Appropriate conventional ones such as those coated with an appropriate release agent such as long-chain alkyl, fluorine-based, or molybdenum sulfide can be used.

  In the present invention, the polarizer, protective film, optical film, etc. that form the polarizing plate described above, and each layer such as an adhesive layer include, 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 or the optical film of the present invention can be preferably used for forming various devices such as a liquid crystal display device. The liquid crystal display device can be formed according to the conventional method. That is, a liquid crystal display device is generally formed by appropriately assembling components such as a liquid crystal cell, a polarizing plate or an optical film, and an illumination system as necessary, and incorporating a drive circuit. There is no limitation in particular except the point which uses the polarizing plate or optical film by invention, and it can apply according to the former. As the liquid crystal cell, any type such as a TN type, an STN type, or a π type can be used.

  An appropriate liquid crystal display device such as a liquid crystal display device in which a polarizing plate or an optical film is disposed on one side or both sides of a liquid crystal cell, or a backlight or a reflector used in an illumination system can be formed. In that case, the polarizing plate or optical film by this invention can be installed in the one side or both sides of a liquid crystal cell. When providing a polarizing plate or an optical film on both sides, they may be the same or different. Further, when forming a liquid crystal display device, for example, a single layer or a suitable part such as a diffusing plate, an antiglare layer, an antireflection film, a protective plate, a prism array, a lens array sheet, a light diffusing plate, a backlight, etc. Two or more layers can be arranged.

  Examples of the present invention will be described below, but the present invention is not limited to the examples shown below. In addition, the following examples and comparative examples were evaluated by the following methods.

(Zinc content)
The content of zinc in the polarizer was measured with a fluorescent X-ray analyzer (manufactured by Rigaku Corporation, ZSX).

(Moisture permeability)
The moisture permeability of the film was measured according to the moisture permeability test (cup method) of JIS Z0208, with the relative humidity difference of 40 ° C. and 90%, and the weight of water vapor that permeated the sample of area 1 m ² in 24 hours (glass transition). Temperature (Tg))
It calculated | required by the DSC method according to JISK7121 (1987) using the thermal analyzer (EXSTAR-6000) of the product made from SII (Seiko Instruments Inc.).

(Average particle size)
The average particle size of the colloid in the aqueous solution was measured by a dynamic light scattering method (light correlation method) with a particle size distribution meter (manufactured by Nikkiso Co., Ltd., Nanotrack UAP150).

(Viscosity of adhesive aqueous solution)
The prepared adhesive aqueous solution (normal temperature: 23 ° C.) was measured with a rheometer (RSI-HS, manufactured by HAAKE).

(Measurement of degree of polarization and transmittance)
Using a spectrophotometer (Murakami Color Research Laboratory, DOT-3), the transmittance (single transmittance) of one polarizing plate was measured. Further, using the same spectrophotometer, the transmittance (parallel transmittance: H ₀ ) when two identical polarizing plates are overlapped so that both transmission axes are parallel, and both transmission axes are The transmittance (orthogonal transmittance: H ₉₀ ) at the time of overlapping so as to be orthogonal was measured. Then, the degree of polarization was calculated by applying the parallel transmittance (H ₀ ) and the orthogonal transmittance (H ₉₀ ) to the following equation.
Polarization degree (%) = {(H ₀ −H ₉₀ ) / (H ₀ + H ₉₀ )} ^1/2 × 100
The single transmittance, the parallel transmittance (H ₀ ), and the orthogonal transmittance (H ₉₀ ) are Y values obtained by correcting the visibility with a two-degree field of view (C light source) of JIS Z8701.

(Moisture resistance test)
The polarizing plate was put into a constant temperature and humidity chamber at 85 ° C. and 85% RH, the degree of polarization after 250 hours was measured, and the amount of change (ΔP ₂₅₀ ) from the initial value was calculated.

(Example 1)
(Creating a polarizer)
A polyvinyl alcohol film having an average degree of polymerization of 2700 and a thickness of 75 μm was stretched and conveyed while being dyed between rolls having different peripheral speed ratios. First, the film was immersed in a 30 ° C. water bath for 1 minute to swell the polyvinyl alcohol film and stretched 1.2 times in the conveying direction, and then the potassium iodide concentration at 30 ° C. was 0.03% by weight, and the iodine concentration was 0.3. The film was stretched 3 times in the transport direction while being dyed by immersing in a weight% aqueous solution (bath solution) for 1 minute on the basis of a film that was not stretched at all. Next, the film was completely stretched in the conveying direction while being immersed in an aqueous solution (bath solution) having a boric acid concentration of 4% by weight, a potassium iodide concentration of 5% and a zinc sulfate concentration of 2.5% by weight for 30 seconds. The film was stretched 6 times based on no film. Subsequently, the obtained stretched film was dried at 70 ° C. for 2 minutes to obtain a polarizer. The thickness of the obtained polarizer was 30 μm, the zinc content was 0.20 wt%, the moisture content was 25.0 wt%, and the Tg was about 79 ° C.

(Protective film)
An acrylic resin film having a lactone ring structure (Tg about 125 ° C., molecular weight Mw about 120,000, thickness 40 μm) was used. The moisture permeability of this film was 95 g / m ² · 24 h.

(Preparation of adhesive)
With respect to 100 parts of polyvinyl alcohol resin containing an acetoacetyl group (average polymerization degree of 1200, saponification degree of 98.5%, acetoacetylation degree of 5 mol%), 50 parts of methylol melamine are subjected to a temperature condition of 30 ° C. An aqueous solution having a solid content of 3.7% by weight was prepared by dissolving in pure water. An aqueous adhesive solution 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 this aqueous solution. The viscosity of the adhesive solution was 9.6 mPa · s, the pH was in the range of 4 to 4.5, and the compounding amount of the alumina colloid was 74 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin.

(Creation of polarizing plate)
The adhesive was applied to one side of the protective film so that the adhesive layer thickness after drying was 80 nm. The protective film to which the adhesive was applied was bonded to both surfaces of the above-described zinc-containing polarizer using a roll machine and dried at 55 ° C. for 6 minutes to prepare a polarizing plate.

In order to cut to 16 × 9 cm using this polarizing plate, using a CO ₂ laser cutting device, the wavelength is 10.6 μm, the output is 80 W, the irradiation diameter is 200 μmφ (the output density is 400 W / mm ² ), and the conveyance speed is 30 m / min. The laser was irradiated from the protective film side under the condition of assist gas (dry air) supply gas pressure of 0.2 MPa, cut along the absorption axis direction, and then cut in the vertical direction. The scanning electron microscope (SEM) photograph of the cross section of the absorption axis direction in that case is shown in FIGS. Moreover, the scanning electron microscope (SEM) photograph at the time of observing the cut surface of an absorption-axis direction from the front is shown in FIG. As a result, it was confirmed that a melt layer continuous from the cut surface of the protective film to the cut surface of the polarizer was formed so as to cover the cut surface. In particular, in the SEM photograph shown in FIG. 4, it is confirmed that the melt layer connecting the cut surface of the protective film to the cut surface of the polarizer covers the cut surface with such a thickness that the layer structure composed of each layer cannot be confirmed. did it.

(Example 2)
Polarized light in the same manner as in Example 1 except that a norbornene-based resin film (manufactured by Nippon Zeon Co., Ltd., ZEONOR film (thickness 40 μm), Tg of about 135 ° C., moisture permeability of 5 g / m ² · 24 h) was used as the protective film. After making the plate, cutting was performed. When the cut surface was observed with a scanning electron microscope (SEM), the same melt layer as in Example 1 was observed.

(Example 3)
In Example 1, a norbornene-based film (manufactured by Nippon Zeon Co., Ltd., ZEONOR film, Tg of about 135 ° C., thickness of 60 μm) was laminated on the side opposite to the polarizer of the protective film, and the conveyance speed during laser cutting was 15 m / A polarizing plate was prepared in the same manner as in Example 1 except that it was divided, and then cut.

(Comparative Example 1)
After producing a polarizing plate in the same manner as in Example 1 except that a triacetylcellulose film (Konica Minolta, KC4UWY (thickness 40 μm), moisture permeability 400 g / m ² · 24 h) was used as the protective film, Cutting was performed.

(Comparative Example 2)
In Example 1, a polarizing plate was prepared in the same manner as in Example 1 except that the polarizing plate was cut using a push-cut type cutting device instead of cutting with a laser, and then cut. When the cut surface was observed with a scanning electron microscope (SEM), it was observed that the cut surface was exposed as shown in FIG.

  Table 1 shows the evaluation results of the polarizing plates obtained in the above Examples and Comparative Examples.

  From the results of Table 1, it was found that the polarizing plate of the present invention suppressed moisture absorption from the cut surface of the polarizer and improved moisture resistance as compared with the case of cutting a blade (Comparative Example 2). In contrast, in the polarizing plate using TAC as the protective film (Comparative Example 1), almost no improvement in moisture resistance was observed.

(Example 4)
The polarizing plate used in Example 3 was heat cut by heating the plate blade to 300 ° C. The cutting speed was 5 m / min and the contact time was 0.4 seconds. When the cross section of this polarizing plate was observed with SEM, the same melt layer as Example 1 was observed.

(Comparative Example 3)
In Example 1, it has a cut surface in the same manner as in Example 1 except that amorphous PET having a Tg of 70 ° C. (a moisture permeability of 50 g / m ² · 24 h) was used as the protective film. A polarizing plate was produced. As a result of observing the cross section of this polarizing plate with SEM, the cut surface was exposed as in Comparative Example 2, and the moisture resistance was also inferior to that of Example 1. (5.0%)
(Comparative Example 4)
In Example 1, a polarizing plate having a cut surface was prepared in the same manner as in Example 1 except that acrylic having a thickness of 20 μm was used as the protective film. As a result of observing the cross section of this polarizing plate with SEM, the cut surface was exposed as in Comparative Example 2, and the moisture resistance was also inferior to that of Example 1. (2.9%)
(Comparative Example 5)
In Example 1, except that the polarizing plate was cut using an excimer laser, a polarizing plate was prepared in the same manner as in Example 1, and then cut to prepare a polarizing plate having a cut surface. When the cut surface was observed by SEM, it was confirmed that the cut surface was exposed as in Comparative Example 2, and the moisture resistance was also inferior to that of Example 1. (2.0%)

Claims (4)

A polarizing plate in which a protective film is bonded to at least one side of a polarizer via an adhesive, and the protective film has a moisture permeability of 150 g / m ² · 24 h or less in an atmosphere of 40 ° C. and 90% RH. And at least one end of the polarizing plate has a cut surface, and a melt layer connected from the cut surface of the protective film to the cut surface of the polarizer is formed to cover the cut surface of the polarizer. The polarizing plate is characterized in that the glass transition temperature (Tg) of the protective film is 30 ° C. or more higher than the glass transition temperature (Tg) of the polarizer.   The polarizing plate according to claim 1, wherein a thickness of the protective film is 0.8 times or more and 25 times or less of a thickness of the polarizer. A method for producing a polarizing plate in which a protective film is laminated on at least one side of a polarizer via an adhesive,
A step of bonding a protective film having a moisture permeability of 150 g / m ² · 24 h or less under an atmosphere of 40 ° C. and 90% RH and the polarizer through an adhesive;
By melting and cutting at least one end of the bonded polarizing plate, a melt layer connected from the cut surface of the protective film to the cut surface of the polarizer is formed so as to cover the cut surface of the polarizer And a process of
The manufacturing method of the polarizing plate which has this.   The manufacturing method of the polarizing plate of Claim 3 whose glass transition temperature (Tg) of the said protective film is 30 degreeC or more higher than the glass transition temperature (Tg) of the said polarizer.

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