JP2009042457A - Polarizing plate, method for producing the same, optical film, and image display apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate having excellent durability in both of moisture resistance and heat resistance, and in which the generation of knick is suppressed as well, and to provide a method for producing the same. <P>SOLUTION: In a polarizing plate, protective films are laminated on both sides of a polarizer via an adhesive. The polarizer comprises a polyvinyl alcohol based resin comprising iodine, and also contains zinc. The protective film comprises a (meta)acrylic based resin at least having a lactone ring structure. The adhesive comprises: a polyvinyl alcohol based resin; a cross-linking agent; and metal compound colloid with the average particle diameter of 1 to 100 nm. <P>COPYRIGHT: (C)2009,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 heat resistance of a polarizing plate, a method of suppressing hue change during heating of the polarizer by incorporating zinc in the polarizer or adhesive has been proposed (for example, Patent Document 1, Patent Document 2). However, the moisture resistance of the polarizing plate cannot be improved by these methods.

  On the other hand, a method for improving the moisture resistance of a polarizing plate by using a norbornene-based resin film or the like as a protective film for a polarizer instead of a triacetyl cellulose film having high moisture permeability has been proposed (for example, Patent Documents). 3). However, it has been confirmed that a polarizing plate using such a film as a protective film is improved in moisture resistance, but has defects in optical characteristics due to deterioration in heat resistance. Moreover, even if the above-described film is simply bonded to the polarizer containing zinc as a protective film, both the moisture resistance and the heat resistance are not improved by utilizing the respective characteristics. Rather, their durability was even worsened.

Furthermore, when a norbornene resin film or the like is used, there is a problem that local unevenness defects (knic defects) are more likely to occur than when a film such as a triacetyl cellulose film is used. In particular, the occurrence was remarkable when bonded to a polarizer via a polyvinyl alcohol-based adhesive.
JP 2000-35512 A Japanese Patent Laid-Open No. 2003-50318 JP-A-8-5836

  The present invention is a polarizing plate in which a protective film is bonded to both surfaces of a polarizer via an adhesive, and has excellent durability in both moisture resistance and heat resistance, and further suppresses generation of nicks and It aims at providing the manufacturing method. Another object of the present invention is to provide an optical film using the polarizing plate and an image display device using the polarizing plate and / or the optical film.

  As a result of intensive studies to solve the above problems, the present inventors have found that the object can be achieved by the polarizing plate shown below, and have completed the present invention.

That is, the present invention is a polarizing plate in which a protective film is bonded to both surfaces of a polarizer via an adhesive,
The polarizer is made of a polyvinyl alcohol-based resin containing iodine, and contains zinc.
The protective film includes a (meth) acrylic resin having a lactone ring structure,
The adhesive relates to a polarizing plate comprising a polyvinyl alcohol-based resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm.

  Furthermore, in the polarizing plate of this invention, it is preferable that the said adhesive contains the said metal compound colloid in the ratio of 200 weight part or less with respect to 100 weight part of polyvinyl alcohol-type resin in an adhesive agent.

  Furthermore, in the polarizing plate of this invention, it is preferable that the said metal compound colloid has a positive charge, and it is especially preferable that it is an alumina colloid.

  Furthermore, in the polarizing plate of this invention, it is preferable that the said polyvinyl alcohol-type resin is a polyvinyl alcohol-type resin containing an acetoacetyl group.

  Furthermore, in the polarizing plate of this invention, it is preferable that the said crosslinking agent contains the compound which has a methylol group.

  Furthermore, in the polarizing plate of this invention, it is preferable that the compounding quantity of the said crosslinking agent is 10-60 weight part with respect to 100 weight part of polyvinyl alcohol-type resin in an adhesive agent.

  Furthermore, in the polarizing plate of this invention, it is preferable that the thickness of an adhesive bond layer is 10-300 nm, and the thickness of an adhesive bond layer is larger than the average particle diameter of the said metal compound colloid.

  Furthermore, in the polarizing plate of this invention, it is preferable that the zinc content in the said polarizer is 0.002 to 2 weight% in a polarizer.

Moreover, this invention relates to the manufacturing method of a polarizing plate. That is, the present invention is a method for producing the polarizing plate in which a protective film is laminated on both sides of a polarizer via an adhesive,
A protective film comprising a polarizer containing zinc and a zinc-containing polarizer and / or a (meth) acrylic resin having a lactone ring structure, a polyvinyl alcohol resin, a crosslinking agent, and an average Applying an adhesive containing a metal compound colloid having a particle size of 1 to 100 nm,
A step of bonding the polarizer and the protective film;
A step of drying after laminating the polarizer and the protective film;
The present invention relates to a method for producing a polarizing plate comprising

  Furthermore, in the manufacturing method of the polarizing plate of this invention, it is preferable that the moisture content of the polarizer used for the process of bonding the said polarizer and a protective film is 12 to 31 weight%.

  Furthermore, in the manufacturing method of the polarizing plate of this invention, it is preferable that the drying temperature in the said process to dry is 90 degrees C or less.

  Furthermore, the present invention relates to an optical film in which at least one polarizing plate is laminated.

  Furthermore, the present invention relates to an image display device using at least one of the polarizing plate or the optical film.

  Hereinafter, the polarizing film of the present invention, an iodine polarizer, a protective film having a (meth) acrylic resin having a lactone ring structure (hereinafter sometimes simply referred to as a protective film), and an adhesive will be described. In addition, the manufacturing method will be described.

  As the polarizer constituting the polarizing plate of the present invention, a polyvinyl alcohol-based polarizer containing iodine is used. 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 stretching method in the uniaxial stretching treatment is not particularly limited, and either a wet stretching method or a dry stretching method can be employed. Examples of the stretching means of the dry stretching method include an inter-roll stretching method, a heated roll stretching method, and a compression stretching method. Stretching can also be performed in multiple stages. In the stretching means, the unstretched film is usually heated. Usually, an unstretched film having a thickness of about 30 to 150 μm is used. The stretch ratio of the stretched film can be appropriately set according to the purpose, but the stretch ratio (total stretch ratio) is about 2 to 8 times, preferably 3 to 6.5 times, more preferably 3.5 to 6 times. Is desirable. The thickness of the stretched film is preferably about 5 to 40 μm.

  The iodine staining treatment is performed by immersing the polyvinyl alcohol film in an iodine solution containing iodine and potassium iodide. The iodine solution is usually an iodine aqueous solution, and contains iodine and potassium iodide as a dissolution aid. The iodine concentration is about 0.01 to 1% by weight, preferably 0.02 to 0.5% by weight. The potassium iodide concentration is about 0.01 to 10% by weight, and further 0.02 to 8% by weight. It is preferable to use it.

  In the iodine dyeing treatment, the temperature of the iodine solution is usually about 20 to 50 ° C, preferably 25 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably 20 to 240 seconds. In the iodine dyeing treatment, the iodine content and potassium content in the polyvinyl alcohol film are within the above ranges by adjusting the conditions such as the concentration of the iodine solution, the immersion temperature of the polyvinyl alcohol film in the iodine solution, and the immersion time. Adjust as follows. The iodine dyeing process may be performed at any stage before the uniaxial stretching process, during the uniaxial stretching process, or after the uniaxial stretching process.

  The boric acid treatment is performed by immersing a polyvinyl alcohol film in an aqueous boric acid solution. The boric acid concentration in the boric acid aqueous solution is about 2 to 15% by weight, preferably 3 to 10% by weight. In the boric acid aqueous solution, potassium ions and iodine ions can be contained by potassium iodide. The potassium iodide concentration in the boric acid aqueous solution is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. A boric acid aqueous solution containing potassium iodide can provide a lightly colored polarizer, that is, a so-called neutral gray polarizer having a substantially constant absorbance over almost the entire wavelength range of visible light.

  In the boric acid treatment, the temperature of the boric acid aqueous solution is, for example, 30 ° C. or higher, preferably 40 to 85 ° C. The immersion time is usually about 1 to 1200 seconds, preferably about 10 to 600 seconds, and more preferably about 20 to 500 seconds. The step of performing the boric acid treatment is after the iodine staining treatment. The boric acid treatment is performed during or after uniaxial stretching. The boric acid treatment may be performed a plurality of times.

  For the iodine ion treatment, for example, an aqueous solution containing iodine ions with potassium iodide or the like is used. The potassium iodide concentration is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight. In the iodine ion impregnation treatment, the temperature of the aqueous solution is usually about 15 to 60 ° C, preferably 25 to 40 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. The stage of iodine ion treatment is not particularly limited as long as it is before the drying process. It can also be performed after water washing described later.

  The polarizing plate of the present invention is characterized in that the polarizer contains 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.

  A zinc salt solution is used for the zinc impregnation treatment. As the zinc salt, an inorganic salt compound in an aqueous solution such as zinc halides such as zinc chloride and zinc iodide, zinc sulfate and zinc acetate is suitable. Among these, zinc sulfate is preferable because the retention rate of zinc in the polarizer can be increased. Various zinc complex compounds can be used for the zinc impregnation treatment. The concentration of zinc ions in the zinc salt aqueous solution is about 0.1 to 10% by weight, preferably 0.3 to 7% by weight. The zinc salt solution is preferably an aqueous solution containing potassium ions and iodine ions with potassium iodide or the like because it is easy to impregnate zinc ions. The potassium iodide concentration in the zinc salt solution is preferably about 0.5 to 10% by weight, more preferably 1 to 8% by weight.

  In the zinc impregnation treatment, the temperature of the zinc salt solution is usually about 15 to 85 ° C, preferably 25 to 70 ° C. The immersion time is usually about 1 to 120 seconds, preferably 3 to 90 seconds. In the zinc impregnation treatment, the zinc content in the polyvinyl alcohol film can be adjusted by adjusting conditions such as the concentration of the zinc salt solution, the immersion temperature of the polyvinyl alcohol film in the zinc salt solution, and the immersion time. The stage of the zinc impregnation treatment is not particularly limited, and may be before the iodine dyeing treatment, before the immersion treatment in the boric acid aqueous solution after the iodine dyeing treatment, during the boric acid treatment, or after the boric acid treatment. Further, it may be carried out simultaneously with the iodine dyeing treatment in the presence of a zinc salt in the iodine dyeing solution. The zinc impregnation treatment is preferably performed together with boric acid treatment. Moreover, a uniaxial stretching process can also be performed with a zinc impregnation process. Moreover, you may perform a zinc impregnation process in multiple times.

  The treated polyvinyl alcohol film (stretched film) can be subjected to a water washing step and a drying step according to a conventional method.

  The water washing step is usually performed by immersing a polyvinyl alcohol film in pure water. The water washing temperature is usually in the range of 5 to 50 ° C, preferably 10 to 45 ° C, more preferably 15 to 40 ° C. The immersion time is usually about 10 to 300 seconds, preferably about 20 to 240 seconds.

  Arbitrary appropriate drying methods, for example, natural drying, ventilation drying, heat drying, etc., can be adopted as the drying step. For example, in the case of heat drying, the drying temperature is typically 20 to 80 ° C., preferably 25 to 70 ° C., and the drying time is typically about 1 to 10 minutes.

  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.

  The protective film which comprises the polarizing plate of this invention uses what contains the (meth) acrylic-type resin which has a lactone ring structure in the said polarizer both surfaces. Since the (meth) acrylic resin having a lactone ring structure has low moisture permeability and excellent heat resistance, a polarizing plate with little change in optical properties can be obtained even in a high temperature and high humidity environment.

  The polarizing plate of the present invention has protective films on both sides of the polarizer, but the protective film contains one side of the polarizer and the other side as long as it contains a (meth) acrylic resin having a lactone ring structure. In terms of surface, the same protective film may be used, and the protective film may be the same in thickness, resin composition, additive type, amount, and the like. 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.

  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.

  The (meth) acrylic resin having a lactone ring structure preferably has a ring structure represented by the following general formula (1).

^Wherein, R 1, ^{R 2} and ^{R 3} each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. The organic residue may contain an oxygen atom.

  The content ratio of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is preferably 5 to 90% by weight, more preferably 10 to 70% by weight, The amount is preferably 10 to 60% by weight, particularly preferably 10 to 50% by weight. When the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is less than 5% by weight, heat resistance, solvent resistance, and surface hardness are poor. May be sufficient. If the content of the lactone ring structure represented by the general formula (1) in the structure of the (meth) acrylic resin having a lactone ring structure is more than 90% by weight, molding processability may be poor. The ratio of the lactone ring structure in the (meth) acrylic resin having a lactone ring structure can be quantified by a dynamic TG (DTG) method disclosed in JP-A-2006-171464.

  The (meth) acrylic resin having a lactone ring structure may have a structure other than the lactone ring structure represented by the general formula (1). The structure other than the lactone ring structure represented by the general formula (1) is not particularly limited, but a (meth) acrylic acid ester which will be described later as a method for producing a (meth) acrylic resin having a lactone ring structure. , A polymer structural unit (repeating structural unit) formed by polymerizing at least one selected from the group consisting of a hydroxyl group-containing monomer, an unsaturated carboxylic acid, and a monomer represented by the following general formula (2): .

In the formula, R ⁴ represents a hydrogen atom or a methyl group, and X represents a hydrogen atom, an alkyl group having 1 to 20 carbon atoms, an aryl group, an —OAc group, a —CN group, a —CO—R ⁵ group, or —C—. Represents an O—R ⁶ group, an Ac group represents an acetyl group, R ⁵ and R ⁶ represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms.

  The content ratio of the structure other than the lactone ring structure represented by the general formula (1) in the (meth) acrylic resin structure having a lactone ring structure is a polymer structure formed by polymerizing a (meth) acrylate ester. In the case of a unit (repeating structural unit), it is preferably 10 to 95% by weight, more preferably 10 to 90% by weight, further preferably 40 to 90% by weight, and particularly preferably 50 to 90% by weight. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing a polymer, it is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, still more preferably 0 to 15% by weight, particularly preferably 0. -10% by weight. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing an unsaturated carboxylic acid, it is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, still more preferably 0 to 15% by weight, particularly Preferably it is 0 to 10% by weight. In the case of a polymer structural unit (repeating structural unit) formed by polymerizing the monomer represented by the general formula (2), it is preferably 0 to 30% by weight, more preferably 0 to 20% by weight, still more preferably. Is 0 to 15% by weight, particularly preferably 0 to 10% by weight.

  The method for producing the (meth) acrylic resin having a lactone ring structure is not particularly limited. Preferably, an acrylic polymer (a) having a hydroxyl group and an ester group in the molecular chain is obtained by a polymerization step. Thereafter, the obtained acrylic polymer (a) is heat-treated to carry out a lactone cyclization condensation step for introducing a lactone ring structure into the polymer.

  In the polymerization step, an acrylic polymer (a) having a hydroxyl group and an ester group in the molecular chain by carrying out a polymerization reaction of a monomer component containing a monomer represented by the following general formula (3). Get.

In the formula, R ⁷ and R ⁸ each independently represent a hydrogen atom or an organic residue having 1 to 20 carbon atoms. Examples of the monomer represented by the general formula (3) include methyl 2- (hydroxymethyl) acrylate, ethyl 2- (hydroxymethyl) acrylate, isopropyl 2- (hydroxymethyl) acrylate, 2- ( Hydroxymethyl) normal butyl acrylate, 2- (hydroxymethyl) acrylate tertiary butyl and the like. Among these, methyl 2- (hydroxymethyl) acrylate and 2- (hydroxymethyl) ethyl acrylate are preferable, and methyl 2- (hydroxymethyl) acrylate is particularly preferable in that the effect of improving heat resistance is high. As for the monomer represented by the general formula (3), only one type may be used, or two or more types may be used in combination.

  The monomer component used in the polymerization step may contain a monomer other than the monomer represented by the general formula (3). As such a monomer, for example, the (meth) acrylic acid ester, the hydroxyl group-containing monomer, the unsaturated carboxylic acid, and the monomer represented by the general formula (2) are preferably mentioned. Only one type of monomer other than the monomer represented by formula (3) may be used, or two or more types may be used in combination.

  The (meth) acrylic acid ester is not particularly limited as long as it is a (meth) acrylic acid ester other than the monomer represented by the general formula (1). For example, methyl acrylate, ethyl acrylate, acrylic acid n -Acrylic acid esters such as butyl, isobutyl acrylate, t-butyl acrylate, cyclohexyl acrylate, benzyl acrylate; methyl methacrylate, ethyl methacrylate, propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, methacrylic acid methacrylic acid esters such as t-butyl, cyclohexyl methacrylate, benzyl methacrylate; and the like. These may be used alone or in combination of two or more. Among these, methyl methacrylate is particularly preferable from the viewpoint of excellent heat resistance and transparency.

  The hydroxyl group-containing monomer is not particularly limited as long as it is a hydroxyl group-containing monomer other than the monomer represented by the general formula (2). For example, α-hydroxymethyl styrene, α-hydroxyethyl styrene, 2 -2- (hydroxyalkyl) acrylic acid ester such as methyl (hydroxyethyl) acrylate; 2- (hydroxyalkyl) acrylic acid such as 2- (hydroxyethyl) acrylic acid, and the like. Or two or more of them may be used in combination.

  Examples of the unsaturated carboxylic acid include acrylic acid, methacrylic acid, crotonic acid, α-substituted acrylic acid, α-substituted methacrylic acid and the like. These may be used alone or in combination of two or more. You may do it. Among these, acrylic acid and methacrylic acid are preferable in that the effects of the present invention are sufficiently exhibited.

  Examples of the monomer represented by the general formula (2) include styrene, vinyl toluene, α-methyl styrene, acrylonitrile, methyl vinyl ketone, ethylene, propylene, and vinyl acetate. These are used alone. Or two or more of them may be used in combination. Among these, styrene and α-methylstyrene are particularly preferable in that the effects of the present invention are sufficiently exhibited.

  When performing the cyclization condensation reaction, in addition to the acrylic polymer (a), another thermoplastic resin may coexist. Moreover, when performing cyclization condensation reaction, the catalyst of cyclization condensation reaction can be used as needed.

  The (meth) acrylic resin having a lactone ring structure has a mass average molecular weight (sometimes referred to as a weight average molecular weight) of preferably 1,000 to 2,000,000, more preferably 5,000 to 1,000,000, still more preferably 10,000 to 500,000, and particularly preferably. Is 50,000 to 500,000. If the mass average molecular weight is out of the above range, it is not preferable from the viewpoint of moldability. The mass average molecular weight can be determined by gel permeation chromatography (GPC system, manufactured by Tosoh Corporation) using tetrahydrofuran as a solvent in terms of polystyrene.

  The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, further preferably 130 ° C. or higher, particularly preferably 135 ° C. or higher, most preferably. 140 ° C. or higher. By setting Tg within the above range, it is possible to obtain a polarizing plate with small dimensional change and optical characteristics even under a high temperature environment. Although the upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, it is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure of the present invention preferably has a higher total light transmittance measured by a method according to ASTM-D-1003, preferably 85% or more, more preferably It is 88% or more, more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  In addition, the protective film used for the polarizing plate of this invention can contain another thermoplastic resin other than the (meth) acrylic-type resin which has a lactone ring structure. Other thermoplastic resins are preferably those that are thermodynamically compatible and improve transparency and mechanical strength.

  When the (meth) acrylic resin having a lactone ring structure contains another thermoplastic resin, the ratio of the former: latter is preferably 60 to 99: 1 to 40% by weight, more preferably 70 to 97. : 3 to 30% by weight, more preferably 80 to 95: 5 to 20% by weight. When the content ratio of the thermoplastic resin other than the (meth) acrylic resin having a lactone ring structure in the protective film exceeds the above range, the effects of the present invention may not be sufficiently exhibited.

  Examples of the other thermoplastic resins include olefin polymers such as polyethylene, polypropylene, ethylene-propylene copolymer, and poly (4-methyl-1-pentene); halogen-containing materials such as vinyl chloride and chlorinated vinyl resins. Acrylic polymers such as polymethyl methacrylate; styrene polymers such as polystyrene, styrene-methyl methacrylate copolymer, styrene-acrylonitrile copolymer, acrylonitrile-butadiene-styrene block copolymer; polyethylene terephthalate, poly Polyesters such as butylene terephthalate and polyethylene naphthalate; polyamides such as nylon 6, nylon 66 and nylon 610; polyacetal; polycarbonate; polyphenylene oxide; polyphenylene sulfide; Chromatography ether ether ketone; polysulfone; polyether sulfone; polyoxyethylene benzylidene alkylene; polyamideimide; polybutadiene rubber, rubber-like polymer such as ABS resin or ASA resin containing an acrylic rubber; and the like.

  In addition to the (meth) acrylic resin having the lactone ring structure and other thermoplastic resins, 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 additive in the protective film is preferably 50% by weight or less, more preferably 1 to 50% by weight, further preferably 2 to 40% by weight, and 3 to 30% by weight. It is particularly preferred that When there is too much content of the said additive in a protective film, transparency of a protective film, heat resistance, and moisture resistance may be impaired.

Moisture permeability is preferably not more than 150g / m ² · 24h of the protective film, more preferably 10~150g / m ² · 24h, more preferably in a 30~120g / m ² · 24h, 50 It is especially preferable that it is -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.

  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 generated more easily as the protective film becomes thinner, the thickness of the protective film is particularly preferably 10 to 100 μm. Furthermore, it is also possible to adjust the moisture permeability appropriately by changing the thickness of the protective film.

  Although the manufacturing method of the protective film containing the (meth) acrylic-type resin which has a lactone ring structure is not specifically limited, For example, the raw material (resin composition) which forms the film containing a (meth) acrylic-type resin as a main component, It can be obtained by subjecting it to extrusion molding (melt extrusion method such as T-die method or inflation method), cast molding (solution casting method or the like), and calendar molding. The obtained film is preferably stretched in order to improve the film strength, and in particular, biaxial stretching that stretches both in the longitudinal and lateral directions is preferred.

  A transparent protective film containing a (meth) acrylic resin having a lactone ring structure does not cause retardation in an unstretched state, but causes retardation when stretched. When a protective film with a small retardation is required, among the other thermoplastic resins, by blending a (meth) acrylic resin and a birefringent sign as a retardation reducing agent, It is possible to prevent a phase difference from occurring. Examples of the retardation reducing agent include styrene-acrylonitrile copolymers. The retardation value can be controlled by the draw ratio and the blending amount of the retardation reducing agent. In the case of biaxial stretching, the phase difference can be controlled not only by the stretching ratio but also by the ratio of the longitudinal and lateral stretching ratios.

  A protective film having a front phase difference of less than 40 nm and a thickness direction retardation of less than 80 nm is usually used. The front phase difference (Re) is represented by Re = (nx−ny) × d. The thickness direction retardation (Rth) is represented by Rth = (nx−nz) × d. [However, the refractive indexes in the slow axis direction, the fast axis direction, and the thickness direction of the film are nx, ny, and nz, respectively, and d (nm) is the thickness of the film. The slow axis direction is the direction that maximizes the refractive index in the film plane. ]. The protective film is preferably as colored as possible. A protective film having a thickness direction retardation (Rth) of −90 nm to +75 nm is preferably used. By using a film having such a thickness direction retardation of −90 nm to +75 nm, the coloring (optical coloring) of the polarizing plate caused by the protective film can be almost eliminated. The thickness direction retardation is more preferably −80 nm to +60 nm, and particularly preferably −70 nm to +45 nm.

  In the present invention, by adjusting the (meth) acrylic resin having a lactone ring structure used for the protective film and the type and content of other thermoplastic resins, the thickness direction retardation is further brought close to 0, It is also possible to obtain a polarizing plate with little optical coloring. In particular, for the purpose of obtaining a product with small optical coloring, the thickness direction retardation is preferably −50 to +50 nm, more preferably −40 to +40 nm, and further preferably −30 to +30 nm.

  On the other hand, as a protective film, the function of a phase difference plate having a front phase difference of 40 nm or more and / or a thickness direction retardation of 80 nm or more can be provided. The front phase difference is usually controlled in the range of 40 to 200 nm, and the thickness direction phase difference is usually controlled in the range of 80 to 300 nm. When a retardation plate is used as the transparent protective film, the retardation plate functions also as a protective film, so that the thickness can be reduced.

  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.

  Hard coat treatment is performed for the purpose of preventing scratches on the surface of the polarizing plate. For example, a cured film having excellent hardness and slipping properties with an appropriate ultraviolet curable resin such as acrylic or silicone is applied to the protective film. It can be formed by a method of adding to the surface. The antireflection treatment is performed for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the conventional art. Further, the anti-sticking treatment is performed for the purpose of preventing adhesion with an adjacent layer.

  The anti-glare treatment is applied for the purpose of preventing the outside light from being reflected on the surface of the polarizing plate and obstructing the visibility of the light transmitted through the polarizing plate. For example, the surface is roughened by a sandblasting method or an embossing method. It can be formed by imparting a fine concavo-convex structure to the surface of the protective film by an appropriate method such as a blending method of transparent fine particles. The fine particles to be included in the formation of the surface fine concavo-convex structure are, for example, conductive materials made of silica, alumina, titania, zirconia, tin oxide, indium oxide, cadmium oxide, antimony oxide or the like having an average particle size of 0.5 to 50 μm. In some cases, transparent fine particles such as inorganic fine particles, organic fine particles composed of a crosslinked or uncrosslinked polymer, and the like are used. When forming a surface fine uneven structure, the amount of fine particles used is generally about 2 to 50 parts by weight, preferably 5 to 25 parts by weight, based on 100 parts by weight of the transparent resin forming the surface fine uneven structure. The antiglare layer may also serve as a diffusion layer (viewing angle expanding function or the like) for diffusing the light transmitted through the polarizing plate to expand the viewing angle.

  The antireflection layer, antisticking layer, diffusion layer, antiglare layer, and the like can be provided on the protective film itself, or can be provided separately from the transparent protective layer as an optical layer.

  The adhesive constituting the polarizing plate of the present invention is a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm.

  Examples of the polyvinyl alcohol resin include polyvinyl alcohol resins and polyvinyl alcohol resins having an acetoacetyl group. A polyvinyl alcohol resin having an acetoacetyl group is a polyvinyl alcohol-based adhesive having a highly reactive functional group, and is preferable because durability of the polarizing plate is improved.

  Polyvinyl alcohol resin is polyvinyl alcohol obtained by saponifying polyvinyl acetate; a derivative thereof; a saponified product of a copolymer of vinyl acetate and a monomer having copolymerizability; Examples thereof include modified polyvinyl alcohols that have been converted into ethers, ethers, grafts, or phosphoric esters. 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 can be used singly or in combination of two or more.

  The polyvinyl alcohol-based resin is not particularly limited, but from the viewpoint of adhesiveness, the average degree of polymerization is about 100 to 5000, preferably 1000 to 4000, the average saponification degree is about 85 to 100 mol%, preferably 90 to 100 mol%. It is.

  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. Another example is a method in which diketene gas or liquid diketene is brought into direct contact with polyvinyl alcohol.

  The degree of acetoacetyl group modification of the polyvinyl alcohol-based resin containing 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 tends to be insufficient. The degree of acetoacetyl group modification is preferably about 0.1 to 40 mol%, more preferably 1 to 20 mol%, and particularly preferably 2 to 7 mol%. If the degree of acetoacetyl modification exceeds 40 mol%, the effect of improving water resistance may not be sufficiently obtained. The degree of acetoacetyl modification can be quantified by NMR.

  As a crosslinking agent, what is used for the polyvinyl alcohol-type adhesive agent can be especially used without a restriction | limiting. A compound having at least two functional groups having reactivity with the polyvinyl alcohol resin can be used. For example, alkylene diamines having two alkylene groups and two amino groups such as ethylenediamine, triethylenediamine, hexamethylenediamine; tolylene diisocyanate, hydrogenated tolylene diisocyanate, trimethylolpropane tolylene diisocyanate adduct, triphenylmethane triisocyanate, methylene bis (Isocyanates such as 4-phenylmethane triisocyanate, isophorone diisocyanate and their ketoxime block product or phenol block product; ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, glycerin di or triglycidyl ether, 1,6-hexane Diol diglycidyl ether, trimethylolpropane triglycidyl ether, jig Epoxys such as sidylaniline and diglycidylamine; monoaldehydes such as formaldehyde, acetaldehyde, propionaldehyde, and butyraldehyde; Aldehydes: amino-formaldehyde resins such as methylol urea, methylol melamine, alkylated methylol urea, alkylated methylolated melamine, acetoguanamine, condensate of benzoguanamine and formaldehyde; further sodium, potassium, magnesium, calcium, aluminum, iron And salts of divalent metals such as nickel or trivalent metals and oxides thereof, among which amino-formaldehyde resins and dia Dehydro are preferred amino -.. Is preferably a compound having a methylol group as a formaldehyde resin, the dialdehydes are preferred glyoxal is inter alia a compound having a methylol group, methylol melamine is particularly preferred.

  The amount of the crosslinking agent can be appropriately designed according to the type of the polyvinyl alcohol resin in the adhesive and the like, but is usually about 10 to 60 parts by weight, preferably 20 with respect to 100 parts by weight of the polyvinyl alcohol resin. ~ 50 parts by weight. In such a range, good adhesiveness can be obtained.

  In order to improve durability, it is preferable to use a polyvinyl alcohol-based resin containing an acetoacetyl group. Also in this case, it is preferable to use the crosslinking agent in the range of 10 to 60 parts by weight, and further 20 to 50 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin in the adhesive. 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 usable time (pot life) as an adhesive becomes extremely short, and industrial use may be 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.

  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 adhesion 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.

  Various types of metal compound colloids can be used. For example, as a metal compound colloid, colloids of metal oxides such as alumina, silica, zirconia, titania, aluminum silicate, calcium carbonate and magnesium silicate; colloids of metal salts such as zinc carbonate, barium carbonate and calcium phosphate; celite, Examples include colloids of minerals such as talc, clay and kaolin.

  The metal compound colloid is dispersed in a dispersion medium and exists in a state of a colloid solution. The dispersion medium is mainly water. In addition to water, other dispersion media such as alcohols can also be used. The solid content concentration of the metal compound colloid in the colloid solution is not particularly limited, but is generally about 1 to 50% by weight, and more preferably 1 to 30% by weight. In addition, as the metal compound colloid, those containing an acid such as nitric acid, hydrochloric acid, and acetic acid as a stabilizer can be used.

  Metal compound colloids are electrostatically stabilized and can be classified into those having a positive charge and those having a negative charge. Metal compound colloids are non-conductive materials. 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 charge in the state of the colloidal solution of the present application is affected by the pH of the adjusted adhesive solution. The pH of the adhesive solution is usually set in the range of 2 to 6, preferably 2.5 to 5, more preferably 3 to 5, and further 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. 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 film. The compounding ratio of the metal compound colloid is preferably 10 to 200 parts by weight, more preferably 20 to 175 parts by weight, and further preferably 30 to 150 parts by weight. If the blending ratio of the metal compound colloid with respect to the polyvinyl alcohol resin is excessive, the adhesiveness may be inferior. If the blending ratio of the metal compound colloid is small, the effect of suppressing the occurrence of nicks may not be sufficiently obtained.

  The adhesive used for the polarizing plate of the present invention is a resin solution containing a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm, and 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.

  Although the viscosity of the resin solution which is an adhesive for polarizing plates is not particularly limited, a resin solution in the range of 1 to 50 mPa · s can be suitably used. In making a polarizing plate, it is common that the occurrence of nicks increases as the viscosity of the adhesive decreases. However, by setting the adhesive to the composition as described above, regardless of the viscosity of the resin solution, 1 Even in a low viscosity range such as ˜20 mPa · s, the occurrence of nicks can be suppressed. The polyvinyl alcohol-based resin containing an acetoacetyl group cannot be increased in polymerization degree compared to a general polyvinyl alcohol resin, and has been used with a low viscosity as described above. In the case of using a polyvinyl alcohol resin containing an acetoacetyl group as an adhesive, the occurrence of nicks caused by the low viscosity of the resin solution can be suppressed.

  The method for preparing the resin solution that is the polarizing plate adhesive is not particularly limited. In general, a resin solution is prepared by mixing a polyvinyl alcohol resin and a crosslinking agent and blending a metal compound colloid with a mixture having an appropriate concentration. 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. In addition, the density | concentration of the resin solution which is an adhesive agent for polarizing plates can also be adjusted suitably after preparing a resin solution.

  The polarizing plate adhesive further includes coupling agents such as silane coupling agents and titanium coupling agents, various tackifiers, ultraviolet absorbers, antioxidants, heat stabilizers, and hydrolysis stabilizers. A stabilizer or the like can also be blended. Moreover, although the metal compound colloid in this application is a nonelectroconductive material, it can also contain the fine particle of an electroconductive substance.

  The polarizing plate of the present invention is produced by bonding the polarizer and the protective film together using the adhesive. In the obtained polarizing plate, a protective film is provided on 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.

  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.

  The viewing angle compensation film is a film for widening the viewing angle so that an image can be seen relatively clearly even when the screen of the liquid crystal display device is viewed from a slightly oblique direction rather than perpendicular to the screen. As such a viewing angle compensation phase difference plate, for example, a phase difference plate, an alignment film such as a liquid crystal polymer, or an alignment layer such as a liquid crystal polymer supported on a transparent substrate is used. A normal retardation plate uses a birefringent polymer film uniaxially stretched in the plane direction, whereas a retardation plate used as a viewing angle compensation film stretches biaxially in the plane direction. A birefringent polymer film, a biaxially stretched film such as a polymer having a birefringence with a controlled refractive index in the thickness direction and uniaxially stretched in the plane direction and also stretched in the thickness direction, and a tilted orientation film are used. . Examples of the inclined alignment film include a film obtained by bonding a heat shrink film to a polymer film and stretching or / and shrinking the polymer film under the action of the contraction force by heating, and a film obtained by obliquely aligning a liquid crystal polymer. Can be mentioned. The raw material polymer of the phase difference plate is the same as the polymer described in the previous phase difference plate, preventing coloring and the like due to a change in viewing angle based on the phase difference by the liquid crystal cell, and widening the viewing angle for good visual recognition. An appropriate one for the purpose can be used.

  Also, from the viewpoint of achieving a wide viewing angle with good visibility, an optically compensated phase difference in which a liquid crystal polymer alignment layer, in particular an optically anisotropic layer composed of a discotic liquid crystal polymer gradient alignment layer, is supported by a triacetylcellulose film. A plate can be preferably used.

  A polarizing plate obtained by bonding a polarizing plate and a brightness enhancement film is usually provided on the back side of a liquid crystal cell. The brightness enhancement film reflects a linearly polarized light with a predetermined polarization axis or a circularly polarized light in a predetermined direction when natural light is incident due to a backlight such as a liquid crystal display device or reflection from the back side, and transmits other light. In addition, a polarizing plate in which a brightness enhancement film is laminated with a polarizing plate allows light from a light source such as a backlight to enter to obtain transmitted light in a predetermined polarization state, and reflects light without transmitting the light other than the predetermined polarization state. The The light reflected on the surface of the brightness enhancement film is further inverted through a reflective layer or the like provided behind the brightness enhancement film and re-incident on the brightness enhancement film, and part or all of the light is transmitted as light having a predetermined polarization state. Luminance can be improved by increasing the amount of light transmitted through the enhancement film and increasing the amount of light that can be used for liquid crystal display image display or the like by supplying polarized light that is difficult to be absorbed by the polarizer.

  The brightness enhancement film has a characteristic of transmitting linearly polarized light having a predetermined polarization axis and reflecting other light, such as a multilayer thin film of dielectric material or a multilayer laminate of thin film films having different refractive index anisotropies. Such as an alignment film of a cholesteric liquid crystal polymer or an alignment liquid crystal layer supported on a film substrate, which reflects either left-handed or right-handed circularly polarized light and transmits other light. Appropriate things such as a thing can be used.

  An optical film in which the optical layer is laminated on a polarizing plate can be formed by a method of sequentially laminating separately in the manufacturing process of a liquid crystal display device or the like. There is an advantage that the manufacturing process of a liquid crystal display device or the like can be improved because of excellent stability and assembly work. For the lamination, an appropriate adhesive means such as an adhesive layer can be used. When adhering the polarizing plate and other optical films, their optical axes can be set at an appropriate arrangement angle in accordance with the target retardation characteristics.

  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.

  Next, an organic electroluminescence device (organic EL display device) will be described. Generally, in an organic EL display device, a transparent electrode, an organic light emitting layer, and a metal electrode are sequentially laminated on a transparent substrate to form a light emitter (organic electroluminescent light emitter). Here, the organic light emitting layer is a laminate of various organic thin films, for example, a laminate of a hole injection layer made of a triphenylamine derivative and the like and a light emitting layer made of a fluorescent organic solid such as anthracene, Alternatively, a structure having various combinations such as a laminate of such a light emitting layer and an electron injection layer composed of a perylene derivative or the like, or a laminate of these hole injection layer, light emitting layer, and electron injection layer is known. It has been.

  In organic EL display devices, holes and electrons are injected into the organic light-emitting layer by applying a voltage to the transparent electrode and the metal electrode, and the energy generated by recombination of these holes and electrons excites the fluorescent material. Then, light is emitted on the principle that the excited fluorescent material emits light when returning to the ground state. The mechanism of recombination in the middle is the same as that of a general diode, and as can be predicted from this, the current and the emission intensity show strong nonlinearity with rectification with respect to the applied voltage.

  In an organic EL display device, in order to extract light emitted from the organic light emitting layer, at least one of the electrodes must be transparent, and a transparent electrode usually formed of a transparent conductor such as indium tin oxide (ITO) is used as an anode. It is used as. On the other hand, in order to facilitate electron injection and increase luminous efficiency, it is important to use a material having a small work function for the cathode, and usually metal electrodes such as Mg—Ag and Al—Li are used.

  In the organic EL display device having such a configuration, the organic light emitting layer is formed of a very thin film having a thickness of about 10 nm. For this reason, the organic light emitting layer transmits light almost completely like the transparent electrode. As a result, light that is incident from the surface of the transparent substrate at the time of non-light emission, passes through the transparent electrode and the organic light emitting layer, and is reflected by the metal electrode is again emitted to the surface side of the transparent substrate. The display surface of the organic EL display device looks like a mirror surface.

  In an organic EL display device comprising an organic electroluminescent light emitting device comprising a transparent electrode on the surface side of an organic light emitting layer that emits light upon application of a voltage and a metal electrode on the back side of the organic light emitting layer, the surface of the transparent electrode While providing a polarizing plate on the side, a retardation plate can be provided between the transparent electrode and the polarizing plate.

  Since the retardation plate and the polarizing plate have a function of polarizing light incident from the outside and reflected by the metal electrode, there is an effect that the mirror surface of the metal electrode is not visually recognized by the polarization action. In particular, the mirror surface of the metal electrode can be completely shielded by configuring the retardation plate with a quarter-wave plate and adjusting the angle formed by the polarization direction of the polarizing plate and the retardation plate to π / 4. .

  That is, only the linearly polarized light component of the external light incident on the organic EL display device is transmitted by the polarizing plate. This linearly polarized light becomes generally elliptically polarized light by the phase difference plate, but becomes circularly polarized light particularly when the phase difference plate is a quarter wavelength plate and the angle formed by the polarization direction of the polarizing plate and the phase difference plate is π / 4. .

  This circularly polarized light is transmitted through the transparent substrate, the transparent electrode, and the organic thin film, is reflected by the metal electrode, is again transmitted through the organic thin film, the transparent electrode, and the transparent substrate, and becomes linearly polarized light again on the retardation plate. And since this linearly polarized light is orthogonal to the polarization direction of a polarizing plate, it cannot permeate | transmit a polarizing plate. As a result, the mirror surface of the metal electrode can be completely shielded.

  The present invention will be described below with reference to examples, 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.

(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.

(Orthogonal chromaticity)
The orthogonal chromaticity of the polarizing plate was measured with a spectrophotometer (DOT-3, manufactured by Murakami Color Research Laboratory) using the a value in the Hunter color system.

(Heat resistance test)
The orthogonal chromaticity (a ₀ and a ₅₀₀ ) was measured at the initial stage of the polarizing plate and after being left for 500 hours under the condition of 105 ° C.

(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 500 hours was measured, and the amount of change (ΔP ₅₀₀ ) from the initial value was calculated.

(Appearance inspection: Knick defect)
Two polarizing plates are cut out so as to form a square of 1000 mm × 1000 mm, and ^two are laminated on a fluorescent lamp with a luminance of 8000 candela / m ² so that the transmission axes thereof are orthogonal to each other. Were visually counted.

(Measurement of peeling amount)
A sample was prepared by cutting out the polarizing plate so as to be a rectangle having an absorption axis direction of 50 mm and a direction orthogonal to the absorption axis of 25 mm. This sample was immersed in warm water at 60 ° C. for 5 hours and then removed from the warm water, and the amount of peeling of the protective film at the end of the sample was measured with a caliper. In addition, the caliper of the JIS first grade standard was used for the measurement of peeling allowance.

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 transport 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% by weight 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% by weight, and the moisture content was 25.0% by weight.
(Protective film)
(Meth) acrylic resin pellets having a lactone ring structure obtained by cyclocondensing a copolymer of methyl methacrylate (MMA) and 2- (hydroxymethyl) methyl acrylate (MHMA) (ratio of lactone ring structure) : 19.4%, weight average molecular weight: 133000, melt flow rate: 6.5 g / 10 min, glass transition temperature: 131 ° C., and acrylonitrile-styrene (AS) resin (manufactured by Toyo Styrene Co., Ltd .; trade name Toyo AS AS20) ) Was kneaded at a weight ratio of 90:10 using a single screw extruder (φ = 30 mm) to obtain transparent pellets. The obtained pellet had a glass transition temperature of 127 ° C. This pellet was dissolved in methyl ethyl ketone, and a film having a thickness of about 50 μm was prepared by a solution casting method. This film was longitudinally uniaxially stretched 1.5 times at a speed of 0.1 m / min at 100 ° C. to obtain a mixed film of lactone ring-containing acrylic resin having a thickness of 40 μm and acrylonitrile-styrene (AS) resin. The film obtained had a moisture permeability of 95 g / m ² · 24 h and a moisture content of 2.5% by weight.
(Preparation of adhesive)
Polyvinyl alcohol resin containing acetoacetyl group (average polymerization degree 1200, saponification degree 98.5%, acetoacetylation degree 5 mol%) 100 parts by weight, methylol melamine 50 parts by weight, 30 ° C. temperature condition Then, it was dissolved in pure water to prepare an aqueous solution having a solid content concentration of 3.7% by weight. 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%, 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.

(Example 2)
(Preparation of adhesive)
The amount of alumina colloid aqueous solution (average particle size 15 nm, solid content concentration 10% by weight, positive charge) was adjusted so that the compounding amount of alumina colloid was 140 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. Except for this, the adhesive was adjusted in the same manner as in Example 1.
(Creation of polarizing plate)
A polarizing plate was produced in the same manner as in Example 1 except that the above adhesive was used as the adhesive.

(Example 3)
(Preparation of adhesive)
An adhesive was prepared in the same manner as in Example 1 except that an alumina colloid aqueous solution (average particle size 75 nm, solid content concentration 10% by weight, positive charge) was used.
(Creation of polarizing plate)
A polarizing plate was produced in the same manner as in Example 1 except that the above adhesive was used as the adhesive.

(Comparative Example 1)
(Creating a polarizer)
A polarizer not containing zinc was prepared in the same manner as in Example 1 except that zinc sulfate was not contained in the bath liquid used when the polyvinyl alcohol film was stretched 6 times.
(Creation of polarizing plate)
A polarizing plate was prepared in the same manner as in Example 1 except that the above-described polarizer containing no zinc was used.

(Comparative Example 2)
(Protective film)
A triacetyl cellulose film (Konica Minolta, KC4UWY (thickness 40 μm)) was used. The moisture permeability of this film was 400 g / m ² · 24 h.
(Creation of polarizing plate)
A polarizing plate was prepared in the same manner as in Example 1 except that the above triacetyl cellulose film was used as a protective film.

(Comparative Example 3)
(Creation of polarizing plate)
A polarizing plate was prepared in the same manner as in Example 1, except that the same lactone ring-containing acrylic film as in Example 1 was used on one side of the polarizer and the same triacetyl cellulose film as in Comparative Example 2 was used on the other side. did.

(Comparative Example 4)
(Creating a polarizer)
A polyvinyl alcohol film having an average polymerization degree of 2700 and a thickness of 75 μm was immersed in a 30 ° C. water bath to swell, and then from an aqueous solution (concentration 1% by weight) of a commercially available dichroic dye (manufactured by Kishida Chemical Co., Ltd., Congo Red). The film was stretched about 3 times in a dye bath at 30 ° C. Then, it extended | stretched so that the total draw ratio might be 6 times in the crosslinking bath which consists of a 3 weight% boric acid aqueous solution of 50 degreeC. Furthermore, it cross-linked with a 4% by weight aqueous solution of boric acid at 30 ° C. Next, it was dried at 50 ° C. for 4 minutes to obtain a polarizer containing an absorbing dichroic dye instead of iodine.
(Creation of polarizing plate)
A polarizing plate was prepared using a triacetyl cellulose film as a protective film on both sides of the polarizer in the same manner as in Comparative Example 2 except that the above dye-based polarizer was used.

(Comparative Example 5)
(Preparation of adhesive)
An adhesive aqueous solution was prepared in the same manner as in Example 1 except that the alumina colloid aqueous solution was not added when adjusting the adhesive.
(Creating a polarizer)
A polarizing plate was produced in the same manner as in Example 1 except that the above adhesive was used as the adhesive.

(Comparative Example 6)
(Preparation of adhesive)
The amount of alumina colloid aqueous solution (average particle size 15 nm, solid content concentration 10% by weight, positive charge) was adjusted so that the amount of alumina colloid blended was 300 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin. Except for this, the adhesive was adjusted in the same manner as in Example 1.
(Creation of polarizing plate)
A polarizing plate was produced in the same manner as in Example 1 except that the above adhesive was used as the adhesive.

(Comparative Example 7)
(Preparation of adhesive)
An adhesive was prepared in the same manner as in Example 1 except that an alumina colloid aqueous solution (average particle diameter 1 μm, solid content concentration 10% by weight, positive charge) was used.
(Creation of polarizing plate)
A polarizing plate was produced in the same manner as in Example 1 except that the above adhesive was used as the adhesive.

  Table 1 shows the production conditions and evaluation results of the polarizing plates obtained in Examples 1 to 3 and Comparative Examples 1 to 7.

  From the comparison between each example and Comparative Examples 1 and 2, it can be seen that the durability of the polarizing plate can be enhanced by the (meth) acrylic protective film having a zinc content in the polarizer and a lactone ring structure. Moreover, from the comparative example 3, when a (meth) acrylic-type protective film is used only on one side, although durability is higher than the comparative example 2, it turns out that it is inferior to durability compared with each Example. In addition, the comparison between each example and Comparative Example 4 shows that when a dye-based polarizer is used, the durability is high but the optical properties (degree of polarization) are poor.

  Furthermore, from the comparison between each Example and Comparative Examples 5 to 7, a suitable amount of a metal compound colloid having an appropriate particle size in the pressure-sensitive adhesive prevents the pressure-sensitive adhesive from peeling off and has an excellent appearance. It can be seen that

Claims (14)

A polarizing plate in which a protective film is bonded to both sides of a polarizer via an adhesive,
The polarizer is made of a polyvinyl alcohol-based resin containing iodine, and contains zinc.
The protective film includes a (meth) acrylic resin having a lactone ring structure,
The adhesive comprises a polyvinyl alcohol resin, a crosslinking agent, and a metal compound colloid having an average particle diameter of 1 to 100 nm.   The polarizing plate of Claim 1 in which the said adhesive agent contains a metal compound colloid in the ratio of 200 weight part or less with respect to 100 weight part of polyvinyl alcohol-type resin in an adhesive agent.   The polarizing plate according to claim 1, wherein the metal compound colloid has a positive charge.   The polarizing plate according to claim 3, wherein the metal compound colloid is an alumina colloid.   The polarizing plate according to claim 1, wherein the polyvinyl alcohol resin is a polyvinyl alcohol resin containing an acetoacetyl group.   The thickness of an adhesive bond layer is 10-300 nm, and the thickness of an adhesive bond layer is larger than the average particle diameter of the said metal compound colloid, The polarizing plate of any one of Claims 1-5.   The polarizing plate according to claim 1, wherein the crosslinking agent contains a compound having a methylol group.   The polarizing plate according to claim 1, wherein the amount of the crosslinking agent is 10 to 60 parts by weight with respect to 100 parts by weight of the polyvinyl alcohol resin in the adhesive.   The polarizing plate according to any one of claims 1 to 8, wherein a zinc content in the polarizer is 0.002 to 2% by weight in the polarizer. A method for producing a polarizing plate according to any one of claims 1 to 9, wherein protective films are laminated on both surfaces of the polarizer via an adhesive,
A protective film comprising a polarizer containing zinc and a zinc-containing polarizer and / or a (meth) acrylic resin having a lactone ring structure, a polyvinyl alcohol resin, a crosslinking agent, and an average Applying an adhesive containing a metal compound colloid having a particle size of 1 to 100 nm,
A step of bonding the polarizer and the protective film;
A step of drying after laminating the polarizer and the protective film;
The manufacturing method of the polarizing plate which has this.   The manufacturing method of the polarizing plate of Claim 10 whose moisture content of the polarizer used for the process of bonding the said polarizer and a protective film is 12 to 31 weight%.   The method for producing a polarizing plate according to claim 10 or 11, wherein a drying temperature in the drying step is 90 ° C or lower.   An optical film in which at least one polarizing plate according to claim 1 is laminated.   An image display device using at least one polarizing plate according to claim 1 or an optical film according to claim 13.