JP2011128654A - Method of manufacturing polarizing plate, polarizing plate, and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a polarizing plate to dispense with a drying process during the manufacturing process of the polarizing plate and accordingly improve the productivity of the polarizing plate, give only a small change in dimension of the obtained polarizing plate under a high-temperature or high-temperature and high-humidity environment, and improve the adhesion of a polarizer with transparent substrates on both sides; to provide the polarizing plate having excellent dimension stability and adhesion stability by such a manufacturing method; and to provide a high-quality image display device using such a polarizing plate. <P>SOLUTION: The method of manufacturing the polarizing plate having the transparent substrates on both sides of the polarizer includes steps of: adhering the polarizer with a moisture ratio of 2-15 wt.% with the transparent substrates using an active energy line curable adhesive; and curing the adhesive by application of active energy lines. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a polarizing plate manufacturing method, a polarizing plate, and an image display device such as a liquid crystal display device, an organic EL display device, or a PDP, which includes at least one polarizing plate.

  In the liquid crystal display device, it is indispensable to dispose polarizing plates on both sides of the glass substrate on which the liquid crystal panel surface is formed because of the image forming method. In general, a polarizing plate is used in which a polarizer protective film is bonded to both surfaces of a polyvinyl alcohol film and a polarizer made of a dichroic material such as iodine with a polyvinyl alcohol adhesive ( For example, see Patent Document 1).

  When using a water-based adhesive such as the above-mentioned polyvinyl alcohol-based adhesive, a drying step is required after the polarizer and the polarizer protective film are bonded together. However, the presence of a drying step in the production process of the polarizing plate is not preferable for improving the productivity of the polarizing plate.

  When an aqueous adhesive such as the above-mentioned polyvinyl alcohol-based adhesive is used, a polarizer having a moisture content of about 30% by weight is generally used to increase the affinity with the aqueous adhesive and improve the adhesiveness. However, when a polarizing plate is produced using a polarizer having a high moisture content, there is a problem that dimensional change of the obtained polarizing plate at high temperature or high temperature and high humidity becomes large.

JP 2006-220732 A

  The problems of the present invention are as follows: (1) A drying step is not required during the production process of the polarizing plate, and thus the productivity of the polarizing plate is greatly improved, and the obtained polarizing plate is at high temperature or high temperature and high humidity. To provide a method for producing a polarizing plate that has a small dimensional change and further improves the adhesion between the polarizer and the transparent substrate on both sides thereof. (2) By such a production method, dimensional stability and adhesion stability are provided. It is to provide a polarizing plate having excellent properties, and (3) to provide a high-quality image display device using such a polarizing plate.

The manufacturing method of the polarizing plate of the present invention is as follows:
A method for producing a polarizing plate having a transparent substrate on both sides of a polarizer,
Using an active energy ray-curable adhesive, the polarizer having a moisture content of 2 to 15% by weight and the transparent substrate are bonded together, and the active energy ray is irradiated to cure the adhesive.

  In a preferred embodiment, the active energy ray is an electron beam.

  According to another aspect of the present invention, a polarizing plate is provided. The polarizing plate of the present invention is obtained by the production method of the present invention.

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

  According to the present invention, there is no need for a drying step during the manufacturing process of the polarizing plate, so the productivity of the polarizing plate is greatly improved, and the dimensional change of the obtained polarizing plate under high temperature or high temperature and high humidity It is possible to provide a method for producing a polarizing plate that is small and further improves the adhesion between the polarizer and the transparent substrates on both sides thereof. In addition, such a manufacturing method can provide a polarizing plate excellent in dimensional stability and adhesion stability. Furthermore, a high-quality image display apparatus using such a polarizing plate can be provided. Such an effect is obtained by using an active energy ray-curable adhesive as an adhesive for bonding and irradiating active energy rays when a polarizer and a transparent substrate are bonded to produce a polarizing plate. It can be expressed by curing the adhesive.

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

Hereinafter, although preferable embodiment of this invention is described, this invention is not limited to these embodiment.
In this specification, the in-plane refractive index is nx and ny in the slow axis direction and the fast axis direction, respectively, and the thickness direction refractive index is nz. The slow axis direction refers to the direction in which the in-plane refractive index is maximum.
In this specification, for example, ny = nz includes not only the case where ny and nz are completely the same, but also the case where ny and nz are substantially the same.
In this specification, the in-plane retardation Re can be obtained by the formula: Re = (nx−ny) × d, where d (nm) is the thickness of an optical element (such as a transparent substrate).
In this specification, the thickness direction retardation Rth can be obtained by the formula: Rth = (nx−nz) × d, where d (nm) is the thickness of an optical element (such as a transparent substrate).

[Polarizer]
The polarizer is formed from a polyvinyl alcohol-based resin. As the polarizer, a polyvinyl alcohol resin film that has been uniaxially stretched by dying a dichroic substance (typically iodine or a dichroic dye) is used. The polymerization degree of the polyvinyl alcohol resin constituting the polyvinyl alcohol resin film is preferably 100 to 5000, and more preferably 1400 to 4000.

  The polyvinyl alcohol-based resin film constituting the polarizer can be formed by any suitable method (for example, a casting method in which a solution obtained by dissolving a resin in water or an organic solvent is cast, a casting method, an extrusion method). . The thickness of the polarizer can be appropriately set according to the purpose and application of the LCD in which the polarizing plate is used, but is typically 5 to 80 μm.

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

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

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

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

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

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

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

  The polarizer used in the present invention has a moisture content of preferably 15% by weight or less, more preferably 0 to 14% by weight, still more preferably 1 to 13% by weight, and particularly preferably 2 to 12% by weight. When a polarizing plate is produced using a polarizer having a moisture content of more than 15% by weight, there is a possibility that the dimensional change of the obtained polarizing plate at high temperature or high temperature and high humidity becomes large.

  In the present invention, the polarizer and the transparent base material are cured by a specific method using a specific curable adhesive as described later without using a water-based adhesive such as a polyvinyl alcohol-based adhesive. paste. For this reason, it is not necessary to increase the moisture content of the deflector in order to increase the affinity with the water-based adhesive and improve the adhesion, and the moisture content of the polarizer is reduced to 15% by weight or less as described above. Is possible.

  In the present invention, the moisture content of the polarizer may be adjusted by any appropriate method. For example, adjusting the conditions of the drying process in the manufacturing process of a polarizer is mentioned.

(Transparent substrate)
As the transparent substrate that can be used in the present invention, any appropriate transparent substrate can be adopted as long as it can be bonded to both sides of the polarizer to form a polarizing plate. The transparent substrate may or may not have a retardation (in-plane retardation (Re) or thickness direction retardation (Rth)). In the case of having a retardation, examples of the transparent substrate include a retardation film having a relationship of nx> ny = nz, a retardation film having a relationship of nx = ny> nz, and a position having a relationship of nx>ny> nz. Examples thereof include a retardation film and a retardation film having a relationship of nx>nz> ny. The transparent substrate may be composed of only one layer, or may be a laminate of two or more layers.

  Examples of the material constituting the transparent substrate include thermoplastic resins that are excellent in transparency, mechanical strength, thermal stability, moisture barrier properties, isotropy, and the like. Specific examples of such thermoplastic resins include cellulose resins such as triacetyl cellulose (TAC), polyester resins, polyether sulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, polyimide resins, polyolefin resins, (meth) Examples thereof include acrylic resins, norbornene resins, polyarylate resins, polystyrene resins, polyvinyl alcohol resins, and mixtures thereof. In addition, thermosetting resins such as (meth) acrylic, urethane-based, acrylurethane-based, epoxy-based, and silicone-based or ultraviolet curable resins may be used. One or more arbitrary appropriate additives may be contained in the transparent substrate. 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 transparent substrate 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. . If the content of the thermoplastic resin in the transparent substrate is less than 50% by weight, the high transparency inherent in the thermoplastic resin may not be sufficiently exhibited.

  For example, a polymer film formed from a resin composition as described in JP 2001-343529 A (WO 01/37007) can also be used as a transparent substrate. 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. For example, an extruded product of such a resin composition can be used.

  The transparent substrate is preferably transparent and uncolored. Specifically, the thickness direction retardation Rth of the transparent substrate is preferably −90 nm to +75 nm, more preferably −80 nm to +60 nm, and most preferably −70 nm to +45 nm. When the retardation Rth in the thickness direction of the transparent substrate is within such a range, the optical coloring of the polarizer caused by the transparent substrate can be eliminated.

  The thickness of the transparent substrate can be appropriately set according to the purpose. The thickness of the transparent substrate is typically 500 μm or less, preferably 5 to 300 μm, and more preferably 5 to 150 μm.

  One specific example of the transparent substrate is a cellulose resin. Preferred is an ester of cellulose and a fatty acid. Specific examples of such a cellulose resin include cellulose triacetate (triacetyl cellulose: TAC), cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Cellulose triacetate (triacetyl cellulose: TAC) is particularly preferred. This is because it has low birefringence and high transmittance. Many products are commercially available, and TAC is advantageous in terms of availability and cost.

  Specific examples of TAC commercial products are trade names “UV-50”, “UV-80”, “SH-50”, “SH-80”, “TD-80U”, “TD” manufactured by Fuji Photo Film Co., Ltd. -TAC "," UZ-TAC ", trade name" KC series "manufactured by Konica, and trade name" cellulose triacetate 80 [mu] m series "manufactured by Lonza Japan.

  Another specific example of the transparent substrate is a transparent film having a small thickness direction retardation (Rth). Specifically, Rth is preferably 10 nm or less, more preferably 6 nm or less, and even more preferably 3 nm or less. The lower limit value of Rth is preferably 0 nm or more, and more preferably exceeds 0 nm.

  The transparent film having a small Rth as described above preferably has a small in-plane retardation (Re). Re is preferably 2 nm or less, more preferably 1 nm or less. The lower limit of Re is preferably 0 nm or more, and more preferably exceeds 0 nm.

  Any appropriate material can be adopted as the transparent film having a small Rth as described above. For example, a cellulose resin and a norbornene resin can be used. Preferred examples of the cellulose resin include fatty acid-substituted cellulose polymers such as diacetyl cellulose and triacetyl cellulose.

  The transparent film having a small Rth as described above can be preferably obtained by subjecting a cellulose-based film having a large Rth to an appropriate treatment for reducing the Rth.

  Any appropriate processing method can be adopted as the processing for reducing Rth. For example, a base film such as polyethylene terephthalate, polypropylene, and stainless steel coated with a solvent such as cyclopentanone and methyl ethyl ketone is bonded to a general cellulose film and dried by heating (for example, 3 to 10 at about 80 to 150 ° C. After removing the base film, a solution obtained by dissolving a norbornene resin, a (meth) acrylic resin or the like in a solvent such as cyclopentanone or methyl ethyl ketone is applied to a general cellulose film, Examples include a method of peeling a coated film after heat drying (for example, at about 80 to 150 ° C. for about 3 to 10 minutes).

  As a material for the transparent film having a small Rth as described above, a fatty acid-substituted cellulose polymer with a controlled degree of fatty acid substitution can be used. Generally used triacetyl cellulose has an acetic acid substitution degree of about 2.8, preferably an acetic acid substitution degree of 1.8 to 2.7, more preferably a propionic acid substitution degree of 0.1 to 2.7. By controlling to 1, Rth can be controlled to be small. By adding a plasticizer such as dibutyl phthalate, p-toluenesulfonanilide, and acetyltriethyl citrate to the fatty acid-substituted cellulose polymer, Rth can be controlled to be small. The addition amount of the plasticizer is preferably 40 parts by weight or less, more preferably 1 to 20 parts by weight, and still more preferably 1 to 15 parts by weight with respect to 100 parts by weight of the fatty acid-substituted cellulose polymer.

  The techniques for controlling Rth to be small as described above may be used in appropriate combination.

  Another specific example of the transparent substrate is a (meth) acrylic resin. The (meth) acrylic resin has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 120 ° C. or higher, still more preferably 125 ° C. or higher, and particularly preferably 130 ° C. or higher. When Tg (glass transition temperature) is 115 ° C. or higher, it can be excellent in durability. Although the upper limit of Tg of the said (meth) acrylic-type resin is not specifically limited, From viewpoints of a moldability etc., Preferably it is 170 degrees C or less.

As the (meth) acrylic resin, any appropriate (meth) acrylic resin can be adopted 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.), polymer having an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer) And methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, poly (meth) acrylic acid C _1-6 alkyl such as poly (meth) acrylate methyl is used. More preferably, a methyl methacrylate resin containing methyl methacrylate as a main component (50 to 100% by weight, preferably 70 to 100% by weight) is used.

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

  As the (meth) acrylic resin, a (meth) acrylic resin having a lactone ring structure can also be used. This is because it has high heat resistance, high transparency, and high mechanical strength.

  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. Examples thereof include (meth) acrylic resins having a lactone ring structure described in Japanese Patent No. 146084.

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

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

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

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

  The (meth) acrylic resin having a lactone ring structure has a Tg (glass transition temperature) of preferably 115 ° C. or higher, more preferably 125 ° C. or higher, still more preferably 130 ° C. or higher, particularly preferably 135 ° C., most preferably 140 ° C. or higher. When Tg is 115 ° C. or higher, for example, when incorporated in a polarizing plate as a polarizer protective film, it can be excellent in durability. The upper limit of Tg of the (meth) acrylic resin having the lactone ring structure is not particularly limited, but is preferably 170 ° C. or less from the viewpoint of moldability and the like.

  The (meth) acrylic resin having a lactone ring structure is preferably as the total light transmittance of a molded product obtained by injection molding measured by a method according to ASTM-D-1003 is higher, preferably 85. % Or more, more preferably 88% or more, and still more preferably 90% or more. The total light transmittance is a measure of transparency. If the total light transmittance is less than 85%, the transparency may be lowered.

  Another specific example of the transparent substrate is a cyclic olefin-based resin, and a norbornene-based resin is particularly preferable. The cyclic olefin-based resin is a general term for resins that are polymerized using a cyclic olefin as a polymerization unit, and is described in, for example, JP-A-1-240517, JP-A-3-14882, JP-A-3-122137, and the like. Resin. Specific examples include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and α-olefins such as ethylene and propylene (typically random copolymers). And graft modified products in which these are modified with an unsaturated carboxylic acid or a derivative thereof, and hydrides thereof. Specific examples of the cyclic olefin include norbornene monomers.

  Examples of the norbornene-based monomer include norbornene and alkyl and / or alkylidene substituted products thereof such as 5-methyl-2-norbornene, 5-dimethyl-2-norbornene, 5-ethyl-2-norbornene, and 5-butyl. 2-Norbornene, 5-ethylidene-2-norbornene, etc., polar substituents such as halogens; dicyclopentadiene, 2,3-dihydrodicyclopentadiene, etc .; dimethanooctahydronaphthalene, its alkyl and / or alkylidene Substituents and polar group substituents such as halogen such as 6-methyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6- Ethyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-oct Hydronaphthalene, 6-ethylidene-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-chloro-1,4: 5,8-dimethano -1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-cyano-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a -Octahydronaphthalene, 6-pyridyl-1,4: 5,8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene, 6-methoxycarbonyl-1,4: 5 8-dimethano-1,4,4a, 5,6,7,8,8a-octahydronaphthalene and the like; 3-pentamer of cyclopentadiene, for example, 4,9: 5,8-dimethano-3a, 4 4a, 5,8,8a, 9,9a-octahydro-1H-benzoin 4,11: 5,10: 6,9-trimethano-3a, 4,4a, 5,5a, 6,9,9a, 10,10a, 11,11a-dodecahydro-1H-cyclopentanthracene and the like. It is done.

  The norbornene-based monomer may be used in combination with other cycloolefin capable of ring-opening polymerization within the range not impairing the object of the present invention. Specific examples of such cycloolefins include compounds having one reactive double bond such as cyclopentene, cyclooctene, and 5,6-dihydrodicyclopentadiene.

  The cyclic olefin-based resin preferably has a number average molecular weight (Mn) measured by a gel permeation chromatography (GPC) method using a toluene solvent, preferably 25,000 to 200,000, and more preferably 30,000 to 100,000. Most preferably, it is 40,000-80,000. When the number average molecular weight is in the above range, a material having excellent mechanical strength, good solubility, moldability, and casting operability can be obtained.

  When the cyclic olefin resin is obtained by hydrogenating a ring-opening polymer of a norbornene monomer, the hydrogenation rate is preferably 90% or more, more preferably 95% or more, Preferably it is 99% or more. Within such a range, the heat deterioration resistance and light deterioration resistance are excellent.

  Various products are commercially available as cyclic olefin resins. Specific examples include trade names “ZEONEX” and “ZEONOR” manufactured by ZEON CORPORATION, “Arton” manufactured by JSR, “TOPAS” trade name manufactured by TICONA, and trade names manufactured by Mitsui Chemicals, Inc. “APEL” may be mentioned.

[Active energy ray-curable adhesive]
As the active energy ray-curable adhesive, any appropriate adhesive can be adopted as long as it is an adhesive that is cured by irradiation with active energy rays. Only one type of active energy ray-curable adhesive may be used, or two or more types may be used in combination.

  The active energy ray-curable adhesive is preferably a photopolymerizable monomer or a photopolymerizable oligomer. Only one type of photopolymerizable monomer or photopolymerizable oligomer may be used, or two or more types may be used in combination.

  Examples of the photopolymerizable monomer include unsaturated carboxylic acids such as acrylic acid and methacrylic acid or esters thereof (for example, alkyl-, cycloalkyl-, halogenated alkyl-, alkoxyalkyl-, hydroxyalkyl-, aminoalkyl-, Tetrahydrofurfuryl-, allyl-, glycidyl-, benzyl-, phenoxy-acrylate and methacrylate), alkylene glycol, mono or diacrylate and methacrylate of polyoxyalkylene glycol, trimethylolpropane triacrylate and methacrylate, pentaerythritol tetraacrylate and Methacrylate, acrylamide, methacrylamide or derivatives thereof (for example, acrylamide mono- or di-substituted with alkyl or hydroxyalkyl groups) Methacrylamide, diacetone acrylamide and methacrylamide, N, N'-alkylenebisacrylamide and methacrylamide), allyl compounds (eg, allyl alcohol, allyl isocyanate, diallyl phthalate, triallyl isocyanurate), maleic acid, maleic anhydride , Fumaric acid or its esters (for example, alkyl, halogenated alkyl, alkoxyalkyl mono- or dimaleate and fumarate), other unsaturated compounds (for example, styrene, vinyltoluene, divinylbenzene, N-vinylcarbazole, N-vinylpyrrolidone) ).

  In the case where the curing shrinkage is hindered as a photopolymerizable monomer, for example, isobornyl acrylate or methacrylate, norbornyl acrylate or methacrylate, dicyclopentenoxyethyl acrylate or methacrylate, dicyclopentenoxypropyl Acrylate or methacrylate, acrylate or methacrylate of diethylene glycol dicyclopentenyl monoether, acrylate or methacrylate of polyoxyethylene glycol dicyclopentenyl monoether or polypropylene glycol dicyclopentenyl monoether, dicyclopentenyl cinnamate , Dicyclopentenoxyethyl cinnamate, dicyclopentenoxyethyl monofumarate or difumarate It is. Also, 3,9-bis (1,1-bismethyl-2-oxyethyl) -spiro [5,5] undecane, 3,9-bis (1,1-bismethyl-2-oxyethyl) -2,4,8, 10-tetraoxaspiro [5,5] undecane, 3,9-bis (2-oxyethyl) -spiro [5,5] undecane, 3,9-bis (2-oxyethyl) -2,4,8,10- Mono-, diacrylate or mono-, such as tetraoxaspiro [5,5] undecane, dimethacrylate, or mono-, diacrylate, or mono-, dimeta of ethylene oxide or propylene oxide addition polymers of these spiroglycols Acrylate or methyl ether of the above monoacrylate or methacrylate, 1-azabicyclo [2,2,2] -3-octenyl Rate or methacrylate, bicyclo [2,2,1] -5-heptene-2,3-dicarboxyl monoallyl ester, dicyclopentadienyl acrylate or methacrylate, dicyclopentadienyloxyethyl acrylate or methacrylate, dihydrodi Examples include cyclopentadienyl acrylate or methacrylate.

  As a photopolymerizable oligomer, the oligomer body of the said photopolymerizable monomer is mentioned, for example.

  More specifically, as an active energy ray-curable adhesive, a product name “DA-141” manufactured by Nagase ChemteX, a product name “E704” manufactured by Nitta Gelatin, and a product name “UXC-401” manufactured by Sanyo Kasei Co., Ltd. Is mentioned.

[Production method of polarizing plate]
The method for producing a polarizing plate of the present invention is a method for producing a polarizing plate having a transparent substrate on both sides of a polarizer, and the polarizer and the transparent substrate are bonded using an active energy ray-curable adhesive. The adhesive is cured by irradiating active energy rays.

  The active energy ray-curable adhesive is applied by applying on either side or both sides of the transparent substrate and on either side or both sides of the polarizer.

  A polarizer and a transparent base material are bonded together through the active energy ray-curable adhesive applied as described above. Bonding of the polarizer and the transparent substrate can be performed with a roll laminator or the like.

  After bonding a polarizer and a transparent base material, an active energy ray is irradiated and an active energy ray hardening adhesive is hardened. The irradiation direction of the active energy ray can be irradiated from any appropriate direction. Preferably, it irradiates from the transparent base material side. When irradiated from the polarizer side, the polarizer may be deteriorated.

  Any appropriate active energy ray can be adopted as the active energy ray as long as it can cure the active energy ray-curable adhesive. For example, an electron beam and ultraviolet rays are mentioned. An electron beam is more preferable because an initiator is unnecessary and the curing speed is fast.

  As an irradiation condition of the active energy ray, any appropriate condition can be adopted as long as the active energy ray-curable adhesive can be cured. Taking electron beam irradiation as an example, the acceleration voltage is preferably 50 kV to 200 kV, and the irradiation dose is preferably 5 kGy to 100 kGy (total irradiation dose with line speed taken into account). When the acceleration voltage is low, the electron beam is irradiated through the transparent base material, so the electron beam is absorbed by the transparent base material, and the electron beam does not reach the active energy ray curable adhesive, and the active energy ray curable adhesive. May not cure. If the acceleration voltage is high, the electron beam will pass through too much, so the electron beam will pass through the layer of the active energy ray-curable adhesive and irradiate the polarizer. May cause. Moreover, when there is little irradiation dose, there exists a possibility that an active energy ray hardening adhesive may not react and adhesiveness may not be acquired. When the irradiation dose is large, there is a possibility that the mechanical strength of the transparent substrate is deteriorated or yellowed.

  The thickness of the active energy ray-curable adhesive layer (hereinafter sometimes referred to as “adhesive layer”) obtained by curing by irradiation with active energy rays is preferably 0.5 to 20 μm, more preferably. It is 1-10 micrometers, More preferably, it is 1-8 micrometers, Most preferably, it is 1-6 micrometers. If the thickness of the adhesive layer is thinner than 0.5 μm, the cohesive force of the adhesive layer itself cannot be obtained, and the adhesive strength may not be obtained. If the thickness of the adhesive layer is greater than 20 μm, the cost increases and the effect of curing shrinkage of the adhesive itself appears, which may adversely affect the optical properties of the polarizing plate.

〔Polarizer〕
The polarizing plate of the present invention can be obtained by the production method of the present invention. One preferred embodiment of the polarizing plate of the present invention is that, as shown in FIG. 1, one surface of a polarizer 31 is bonded to a transparent substrate 34 via an adhesive layer 32. The other surface is bonded to the transparent substrate 35 through the adhesive layer 33. The adhesive layer 32 and the adhesive layer 33 may be the same type of adhesive layer or different types of adhesive layers. The transparent substrate 34 and the transparent substrate 35 may be the same type of transparent substrate or different types of transparent substrates.

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

  The pressure-sensitive adhesive forming the pressure-sensitive adhesive layer is not particularly limited. For example, a polymer such as a (meth) acrylic polymer, a silicone-based polymer, a polyester, a polyurethane, a polyamide, a polyether, a fluorine-based or a rubber-based polymer is used as the base polymer. What to do can be selected suitably and can be used. Particularly, a (meth) acrylic pressure-sensitive adhesive that is excellent in optical transparency, exhibits appropriate wettability, cohesiveness, and adhesive pressure-sensitive adhesive properties, and is excellent in weather resistance, heat resistance, and the like can be preferably used. In particular, a (meth) acrylic pressure-sensitive adhesive made of a (meth) acrylic polymer having 4 to 12 carbon atoms is preferred.

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

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

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

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

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

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

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

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

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

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

  In the present invention, the polarizer, transparent substrate, and pressure-sensitive adhesive layer that form the polarizing plate described above include, for example, salicylic acid ester compounds, benzophenol compounds, benzotriazole compounds, cyanoacrylate compounds, nickel, It may be one having a UV absorbing ability by a method such as a method of treating with a UV absorber such as a complex salt compound.

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

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

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

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

  EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited to these Examples. Evaluation was performed as follows.

<Moisture content of polarizer>
The water content of the polarizer is calculated by the ratio between the absorbance at a wavelength of 2.2 μm where infrared absorption of water is observed and the absorbance at a wavelength of 1.8 μm where absorption of water is not observed. Calculated by The measuring instrument used was IRMA1100 manufactured by Chino Corporation.

<Method for measuring thickness>
When the thickness was less than 10 μm, measurement was performed using a spectrophotometer for thin film (manufactured by Otsuka Electronics Co., Ltd., product name “instant multiphotometry system MCPD-2000”). When the thickness was 10 μm or more, measurement was performed using an Anritsu digital micrometer “KC-351C type”.

<Line speed>
The rotation speed was controlled by reading the motor rotation speed of the winding roller with an encoder, and the line speed (winding speed) was controlled.

<Polarizing plate dimension change>
A 10 cm × 10 cm polarizing plate was left in an atmosphere of 80 ° C. or 60 ° C./90% RH for 240 hours, and the dimensional change in the MD direction was measured.

<Warm water immersion test>
A 25 mm × 50 mm polarizing plate was immersed in warm water at 60 ° C. for 10 hours, and the amount of peeling from the end face was measured.

[Example 1]
A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, it was immersed in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide, and further stretched to 6.0 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. Thereafter, it was immersed in a 5% by weight aqueous potassium iodide solution. Thereafter, drying was performed in an oven at 40 ° C. for 1 minute to obtain a polarizer having a thickness of 30 μm and a moisture content of 14% by weight.
A triacetyl cellulose film (manufactured by Konica, trade name: KC4UYW, thickness 40 μm) was attached to both surfaces of the obtained polarizer to produce a polarizing plate (1). At this time, an electron beam curable adhesive (manufactured by Nagase ChemteX, product name: DA141) is applied to a thickness of 5 μm on the surface of the triacetylcellulose film attached to the polarizer, and the triacetyl is sandwiched between the polarizers. The cellulose film was pressure-bonded by lamination from both sides, and then an electron beam with an irradiation amount of 100 kGy was irradiated to cure the electron beam curable adhesive.
The evaluation results of the polarizing plate (1) are shown in Table 1.

[Example 2]
A polyethylene terephthalate (PET) film (trade name: U4300, thickness 38 μm) is used in place of the triacetyl cellulose film, and an electron beam is used instead of the electron beam curable adhesive (manufactured by Nagase ChemteX, product name: DA141). A polarizing plate (2) was produced in the same manner as in Example 1 except that a curable adhesive (manufactured by Nitta Gelatin, trade name: E704) was used.
The evaluation results of the polarizing plate (2) are shown in Table 1.

Example 3
A polarizing plate (3) was produced in the same manner as in Example 1 except that a norbornene-based resin film (manufactured by ZEON, trade name: ZEONOR, thickness 75 μm) was used instead of the triacetylcellulose film.
The evaluation results of the polarizing plate (3) are shown in Table 1.

Example 4
A norbornene-based resin film (manufactured by JSR, trade name: Arton, thickness 75 μm) is used instead of the triacetyl cellulose film, and an electron beam curable adhesive is used instead of the electron beam curable adhesive (manufactured by Nagase ChemteX, trade name: DA141). A polarizing plate (4) was produced in the same manner as in Example 1 except that an adhesive (manufactured by Sanyo Chemical Industries, trade name: UXC-401) was used.
The evaluation results of the polarizing plate (4) are shown in Table 1.

[Comparative Example 1]
A polyvinyl alcohol film having a thickness of 80 μm was dyed in an aqueous iodine solution of 5% by weight (weight ratio: iodine / potassium iodide = 1/10). Next, it was immersed in an aqueous solution containing 3% by weight boric acid and 2% by weight potassium iodide, and further stretched to 6.0 times in an aqueous solution containing 4% by weight boric acid and 3% by weight potassium iodide. Thereafter, it was immersed in a 5% by weight aqueous potassium iodide solution. Thereafter, drying was performed in an oven at 25 ° C. for 3 minutes to obtain a polarizer having a thickness of 30 μm and a moisture content of 30% by weight.
A polyvinyl alcohol adhesive aqueous solution prepared by adjusting an aqueous solution containing 20 parts by weight of methylolmelamine to 100 parts by weight of an acetoacetyl-modified polyvinyl alcohol resin (degree of acetylation 13%) to a concentration of 0.5% by weight Prepared.
A triacetyl cellulose film (manufactured by Konica, trade name: KC4UYW, thickness 40 μm) was attached to both surfaces of the polarizer to produce a polarizing plate (C1). At this time, the polyvinyl alcohol adhesive aqueous solution was pressed between the triacetylcellulose film and the polarizer while being poured, and then dried at 70 ° C. for 10 minutes.
Table 1 shows the evaluation results of the polarizing plate (C1).

  The polarizing plate obtained by the production method of the present invention can be suitably used for various image display devices (liquid crystal display devices, organic EL display devices, PDPs, etc.).

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

Claims (4)

A method for producing a polarizing plate having a transparent substrate on both sides of a polarizer,
Using an active energy ray-curable adhesive, the polarizer having a moisture content of 2 to 15% by weight and the transparent substrate are bonded together, and the adhesive is cured by irradiation with active energy rays.
Manufacturing method of polarizing plate.   The manufacturing method according to claim 1, wherein the active energy ray is an electron beam. A polarizing plate obtained by the production method according to claim 1 . An image display device comprising at least one polarizing plate according to claim 3 .

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