JP2017097087A - Polarizing plate and image display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate that gives good visibility of a display through polarized sunglasses and can suppress decrease in a polarization degree due to the displacement of an absorption axis of a polarization film caused by dimensional changes in an optical film.SOLUTION: The polarizing plate includes a stretched film, a polarizing film and a first adhesive layer in this order, in which an angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is about 45° or about 135°. The stretched film shows a contraction force in the stretched direction of 0.2 N/2 mm or less when heated at 105°C for 30 minutes.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a polarizing plate and an image display device.

  In recent years, low-power consumption, low-voltage, light-weight and thin liquid crystal displays are rapidly spreading as information display devices such as mobile phones, portable information terminals, computer monitors, and televisions. With the development of liquid crystal technology, liquid crystal displays in various modes have been proposed, and problems with liquid crystal displays such as response speed, contrast, and narrow viewing angle are being solved. In addition, with the spread of mobile liquid crystal displays, for example, when used outdoors, the screen of the liquid crystal display may be viewed with polarized sunglasses. Even when viewing the screen through polarized sunglasses, excellent visibility is required.

  As a method for improving visibility when viewing the screen through polarized sunglasses, linearly polarized light emitted from a polarizing plate arranged on the viewing side of an image display element such as a liquid crystal cell is elliptical (or circular). In order to convert it into polarized light, a retardation plate (for example, a λ / 4 wavelength plate) is placed on the viewing side of the polarizing plate, and the angle formed by the absorption axis of the polarizing film and the slow axis of the retardation plate is 45 ° or 135 °. The method of arrange | positioning so that it may become is taken (patent documents 1-9).

JP 2009-122454 A JP2011-107198A JP 2011-215646 A JP 2012-230390 A Japanese Patent Laid-Open No. 03-174512 JP 2013-231761 A JP 2011-1113018 A JP 2013-182162 A JP 2013-200445 A

  A polarizing plate in which such a retardation plate is laminated on a polarizing film, when the polarizing plate is subjected to a heat resistance test, the degree of polarization decreases due to a shift in the absorption axis of the polarizing film due to a dimensional change of the retardation plate. There was a problem that was large.

[1] It has a stretched film, a polarizing film and a first pressure-sensitive adhesive layer in this order,
The angle formed between the absorption axis of the polarizing film and the slow axis of the optical film is about 45 ° or about 135 °,
The stretched film is a polarizing plate having a shrinkage force in the stretching direction of 0.2 N / 2 mm or less when heated at 105 ° C. for 30 minutes.
[2] The polarizing plate according to [1], wherein the polarizing film and the stretched film are laminated via a pressure-sensitive adhesive layer, a water-based adhesive layer, or an active energy ray-curable adhesive layer.
[3] The stretched film includes at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin. Polarizing plate.
[4] The polarizing plate according to any one of [1] to [3], wherein the stretched film has a surface treatment layer on a surface opposite to the surface on the polarizer side.
[5] The polarizing film according to any one of [1] to [4], wherein the stretched film satisfies the following formulas (1) to (4).
(1) 100 nm ≦ R _e (590) ≦ 180 nm,
(2) 0.5 <R _th (590) / R _e (590) ≦ 0.8,
(3) 0.85 ≦ R _e (450) / R _e (550) <1.00
(4) 1.00 <R _e (630) / R _e (550) ≦ 1.1
[In formulas (1) to (4), R _e (590), R _e (450), R _e (550), and R _e (630) are in-plane positions at wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively. Represents a retardation value, and R _th (590) represents a thickness direction retardation value at a wavelength of 590 nm. ]
[6] The polarizing plate according to any one of [1] to [5], wherein the polarizing plate has a rectangular shape, and the ratio of the long side length to the short side length is 10: 1 to 1: 1.
[7] An image display device in which the polarizing plate according to any one of [1] to [6] is laminated on an image display element via the first pressure-sensitive adhesive layer.

  According to the present invention, it is possible to provide a polarizing plate capable of suppressing the decrease in the degree of polarization due to the shift of the absorption axis of the polarizing film caused by the dimensional change of the optical film during the heat resistance test while improving the visibility through the polarized sunglasses. Can do.

It is an example of the cross-sectional schematic diagram which shows the laminated constitution of the polarizing plate which concerns on this invention.

  With reference to FIG. 1, the layer structure of the polarizing plate of this invention is demonstrated. As shown in FIG. 1, the polarizing plate 10 of this invention has the stretched film 11, the polarizing film 14, and the 1st adhesive layer 13 in order of a child.

  The stretched film 11 and the polarizing film 14 are preferably laminated, and the stretched film 11 and the polarizing film are interposed via a pressure-sensitive adhesive layer, an aqueous adhesive layer, or an active energy ray-curable adhesive layer as described later. Can be stacked. In FIG. 1, the pressure-sensitive adhesive layer, the water-based adhesive layer, and the active energy ray-curable adhesive layer are not shown.

  The polarizing plate 10 of the present invention preferably has a protective film 12 between the polarizing film 14 and the first pressure-sensitive adhesive layer 13. When the polarizing plate 10 has the protective film 12, the dimensional change of the polarizing film at the time of a heat test can be suppressed, and the polarization degree fall can be suppressed more.

  When the polarizing plate 10 of the present invention is incorporated in an image display device, the stretched film 11 is often disposed on the viewing-side surface of the polarizing plate. Therefore, the stretched film 11 is bonded to the polarizing film 14. It is preferable to have the surface treatment layer 20 on the opposite surface.

  Hereafter, the member which comprises the image display apparatus of this invention is demonstrated in detail.

[Polarizing film 14]
The polarizing film 14 is usually a step of uniaxially stretching a polyvinyl alcohol resin film, a step of adsorbing a dichroic dye by dyeing the polyvinyl alcohol resin film with a dichroic dye, and a dichroic dye adsorbed. The polyvinyl alcohol-based resin film is produced through a step of crosslinking with a boric acid aqueous solution and a step of washing with water after the crosslinking treatment with the boric acid aqueous solution.

  The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate resin may be a copolymer of vinyl acetate and another monomer copolymerizable therewith, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Examples of other monomers copolymerizable with vinyl acetate include unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and acrylamides having an ammonium group.

  The saponification degree of the polyvinyl alcohol resin is usually about 85 to 100 mol%, preferably 98 mol% or more. The polyvinyl alcohol resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes can be used. The degree of polymerization of the polyvinyl alcohol resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

  What formed such a polyvinyl alcohol-type resin into a film is used as a raw film of a polarizing film. The method for forming a polyvinyl alcohol-based resin is not particularly limited, and can be formed by a known method. The film thickness of a polyvinyl alcohol-type resin raw film is about 10-100 micrometers, for example, Preferably it is about 10-50 micrometers.

  The longitudinal uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before dyeing with the dichroic dye, simultaneously with dyeing, or after dyeing. When longitudinal uniaxial stretching is performed after dyeing, the longitudinal uniaxial stretching may be performed before boric acid treatment or during boric acid treatment. Of course, longitudinal uniaxial stretching can also be performed in a plurality of stages shown here. For the longitudinal uniaxial stretching, a method of stretching uniaxially between rolls having different peripheral speeds, a method of stretching uniaxially using a hot roll, or the like can be adopted. The longitudinal uniaxial stretching may be performed by dry stretching in which stretching is performed in the air, or may be performed by wet stretching in which a polyvinyl alcohol-based resin film is stretched using a solvent such as water. The draw ratio is usually about 3 to 8 times.

  The polyvinyl alcohol resin film can be dyed with a dichroic dye by, for example, a method of immersing the polyvinyl alcohol resin film in an aqueous solution containing the dichroic dye. Specifically, iodine or a dichroic organic dye is used as the dichroic dye. In addition, it is preferable to perform the process which a polyvinyl alcohol-type resin film swells by immersing in water before a dyeing process.

  When iodine is used as the dichroic dye, a method of dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing iodine and potassium iodide is usually employed. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. It is. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 20 to 1,800 seconds.

On the other hand, when a dichroic organic dye is used as the dichroic dye, a method of immersing and dyeing a polyvinyl alcohol-based resin film in an aqueous solution containing a water-soluble dichroic organic dye is usually employed. The content of the dichroic organic dye in this aqueous solution is usually about 1 × 10 ⁻⁴ to 10 parts by weight, preferably 1 × 10 ⁻³ to 1 part by weight per 100 parts by weight of water. This aqueous dye solution may contain an inorganic salt such as sodium sulfate as a dyeing assistant. The temperature of the aqueous dichroic organic dye solution used for dyeing is usually about 20 to 80 ° C. Moreover, the immersion time (dyeing time) in this aqueous solution is usually about 10 to 1,800 seconds.

  The boric acid treatment after dyeing with the dichroic dye can be performed by a method of immersing the dyed polyvinyl alcohol resin film in a boric acid-containing aqueous solution. The boric acid content in the boric acid-containing aqueous solution is usually about 2 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing aqueous solution preferably contains potassium iodide. The content of potassium iodide in the boric acid-containing aqueous solution is usually about 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight per 100 parts by weight of water. The immersion time in the boric acid-containing aqueous solution is usually about 60 to 1,200 seconds, preferably 150 to 600 seconds, and more preferably 200 to 400 seconds. The temperature of the boric acid-containing aqueous solution is usually 50 ° C. or higher, preferably 50 to 85 ° C., more preferably 60 to 80 ° C.

  The polyvinyl alcohol resin film after the boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of immersing a boric acid-treated polyvinyl alcohol resin film in water. The temperature of water in the water washing treatment is usually about 5 to 40 ° C. The immersion time is usually about 1 to 120 seconds.

  After washing with water, a drying process is performed to obtain a polarizing film. The drying process can be performed using a hot air dryer or a far infrared heater. The temperature of a drying process is about 30-100 degreeC normally, Preferably it is 50-80 degreeC. The drying time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the moisture content in the polarizing film is reduced to a practical level. The moisture content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. When the moisture content is less than 5% by weight, the polarizing film loses its flexibility, and may be damaged or broken after drying. On the other hand, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

  As described above, the polarizing film 14 in which the dichroic dye is adsorbed and oriented on the polyvinyl alcohol-based resin film can be produced.

  In the polarizing film 14, the contraction force in the absorption axis direction when the polarizing film is heated at 80 ° C. is preferably 3 N / 2 mm or less, and more preferably 1.5 N / 2 mm or less. The contraction force in the transmission axis direction when the polarizing film is heated at 80 ° C. is preferably 3 N / 2 mm or less, and more preferably 1.5 N / 2 mm or less. By using such a polarizing film, shrinkage of the polarizing film when subjected to a heat resistance test can be reduced, and a decrease in the degree of polarization can be further reduced.

  The shrinkage force of the polarizing film can be measured by the same method as that of the stretched film described later. The “slow axis” is read as “absorption axis” or “transmission axis”.

  In order to keep the contraction force of the polarizing film 14 low, for example, the thickness of the polarizing film 14 is preferably 15 μm or less, and more preferably 12 μm or less. The thickness of the polarizing film is usually 3 μm or more in that good optical properties can be imparted. It is also useful to adjust the conditions for the drying treatment.

  Further, the ratio of the thickness of the stretched film 11 to the thickness of the polarizing film 14 is preferably 1 or more, more preferably 2 or more, and further preferably 3 or more. Further, the ratio of the thickness of the stretched film 11 to the thickness of the polarizing film 14 is preferably 7 or less. By such a combination of thickness ratios, shrinkage of the polarizing film 14 is suppressed by the stretched film, and shrinkage of the stretched film is easily within the range specified in the present application.

  Moreover, even if the extending | stretching of the polyvinyl alcohol-type resin film in the manufacturing process of the polarizing film 14, dyeing | staining, a boric-acid process, a water washing process, and a drying process are performed according to the method described in Unexamined-Japanese-Patent No. 2012-159778, for example. Good. As in the method described in this document, it is also useful to use a method of forming a polyvinyl alcohol resin layer to be a polarizer by coating a base film with a polyvinyl alcohol resin.

[Stretched film 11]
In the polarizing plate used in the present invention, the stretched film 11 is preferably composed of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding properties and the like. For example, polyolefin resin such as chain polyolefin resin (polypropylene resin, etc.), cyclic polyolefin resin (norbornene resin, etc.); cellulose resin such as cellulose ester resin, such as cellulose triacetate and cellulose diacetate; Polyester resins; polycarbonate resins; (meth) acrylic resins; polystyrene resins; or mixtures and copolymers thereof.

The stretched film 11 has the following formula:
(1) 100 nm ≦ R _e (590) ≦ 180 nm,
(2) 0.5 <R _th (590) / R _e (590) ≦ 0.8,
(3) 0.85 ≦ R _e (450) / R _e (550) <1.00, and (4) 1.00 <R _e (630) / R _e (550) ≦ 1.1
It is preferable that the film satisfies the above. In the formula, R _e (590), R _e (450), R _e (550), and R _e (630) represent in-plane retardation values at measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively, and R _th ( 590) represents a thickness direction retardation value at a measurement wavelength of 590 nm. These in-plane retardation value and thickness direction retardation value are measured in an environment of a temperature of 23 ° C. and a relative humidity of 55%.

Plane retardation value R _e, the thickness direction retardation R _th of the stretched film 11 is orthogonal to the refractive index of in-plane slow axis direction n _x, a-plane fast axis direction (in-plane slow axis direction the refractive index in the direction) n _y, a n _z refractive index in the thickness direction, when the thickness of the stretched film 11 is d, the following formula:
_{R e = (n x -n y} ) × d
_{R th = [{(n x} + n y) / 2} -n z] × d
Defined by

  In a liquid crystal display in which the stretched film 11 showing the retardation characteristics and wavelength dispersion characteristics of the above formulas (1) to (4) is arranged on the viewing side, the screen is viewed from various directions (azimuth and polar angles) through polarized sunglasses. The color change at the time can be effectively suppressed, and the visibility of the liquid crystal display can be improved. On the other hand, when any one or more of the above formulas (1) to (4) are not satisfied, the suppression of the color change may be insufficient.

From the viewpoint of more effectively suppressing color change, R _e (590) in formula (1) is preferably 105 to 170 nm, and R _th (590) / R _e (590) in formula (2) is It is preferable that it is 0.6-0.75, R _e (450) / R _e (550) in Formula (3) is preferably 0.86-0.98, and R _e in Formula (4) (630) / R _e (550) is preferably 1.01 to 1.06.

  The stretched film 11 is a kind of retardation film having a function of converting linearly polarized light emitted from the polarizing film 14 toward the stretched film 11 into elliptically polarized light (including a case of circularly polarized light) and emitting the polarized light, In order to develop this function, the angle between the absorption axis of the polarizing film and the slow axis of the optical film is laminated so as to be about 45 ° or about 135 °. If the formed angle is outside this range, the function of converting linearly polarized light into elliptically polarized light and emitting it cannot be obtained, and as a result, the suppression of the color change may be insufficient. In the present invention, approximately 45 ° or approximately 135 ° means 25 to 65 ° or 115 to 155 °, preferably 35 to 55 ° or 125 to 145 °, more preferably It means 40 to 50 ° or 130 to 140 °.

  It is easy to give the phase difference characteristics and wavelength dispersion characteristics of the above formulas (1) to (4), and since the moisture permeability is relatively low, the moisture resistance and heat-and-moisture resistance of the optical laminate can be improved. Preferably, the optical film contains a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, a (meth) acrylic resin, or two or more thereof, and the resin component is selected from these 1 or More preferably, it consists of 2 or more.

  Examples of the chain polyolefin-based resin include a homopolymer of a chain olefin such as a polyethylene resin and a polypropylene resin, and a copolymer composed of two or more chain olefins.

  Cyclic polyolefin resin is a general term for resins that are polymerized using cyclic olefins as polymerization units. Specific examples of cyclic polyolefin resins include ring-opening (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers of cyclic olefins and chain olefins such as ethylene and propylene (typically Are random copolymers), graft polymers obtained by modifying them with unsaturated carboxylic acids or derivatives thereof, and hydrides thereof. Among these, norbornene resins using norbornene monomers such as norbornene and polycyclic norbornene monomers as cyclic olefins are preferably used.

  The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Moreover, these copolymers and those in which a part of the hydroxyl group is modified with other substituents can also be used. Among these, cellulose triacetate (triacetyl cellulose: TAC) is particularly preferable.

  The polyester-based resin is a resin having an ester bond, and is generally made of a polycondensate of a polyvalent carboxylic acid or a derivative thereof and a polyhydric alcohol. As the polyvalent carboxylic acid or a derivative thereof, a divalent dicarboxylic acid or a derivative thereof can be used, and examples thereof include terephthalic acid, isophthalic acid, dimethyl terephthalate, and dimethyl naphthalenedicarboxylate. As the polyhydric alcohol, a divalent diol can be used, and examples thereof include ethylene glycol, propanediol, butanediol, neopentyl glycol, and cyclohexanedimethanol.

  Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexanedimethyl naphthalate.

  The polycarbonate resin is composed of a polymer in which monomer units are bonded via a carbonate group. The polycarbonate-based resin may be a resin called a modified polycarbonate having a modified polymer skeleton, a copolymer polycarbonate, or the like.

The (meth) acrylic resin is a resin containing a compound having a (meth) acryloyl group as a main constituent monomer. Specific examples of (meth) acrylic resins include, for example, poly (meth) acrylic acid esters such as polymethyl methacrylate; methyl methacrylate- (meth) acrylic acid copolymer; methyl methacrylate- (meth) acrylic acid Ester copolymer; methyl methacrylate-acrylic ester- (meth) acrylic acid copolymer; (meth) methyl acrylate-styrene copolymer (MS resin etc.); methyl methacrylate and alicyclic hydrocarbon group And a copolymer (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer). Preferably, a polymer based on a poly (meth) acrylic acid C _1-6 alkyl ester such as poly (meth) acrylic acid methyl is used, and more preferably methyl methacrylate is the main component (50-100). % Methyl methacrylate resin is used.

  The stretched film 11 can be produced by stretching a film containing the thermoplastic resin. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction. For the stretching process, for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or the both ends of the unstretched film are gripped with a chuck and machine flow is performed. It can be performed by spreading in a direction (TD) orthogonal to the direction. At this time, the retardation value and the wavelength dispersion can be controlled within the ranges of the above formulas (1) and (2) by adjusting the thickness of the film or adjusting the stretch ratio. Moreover, it is possible to control the wavelength dispersion value within the range of the above formulas (3) to (4) by adding a wavelength dispersion adjusting agent to the resin.

  The thickness of the stretched film 11 is not particularly limited as long as the above formulas (1) to (4) are satisfied, but from the viewpoint of thinning the polarizing plate, it is preferably 90 μm or less, more preferably 60 μm or less, and even more preferably 45 μm or less. From the viewpoint of handling, it is preferably 5 μm or more, more preferably 10 μm or more.

  The stretched elastic modulus of the stretched film at 80 ° C. is preferably 2000 MPa or more, and more preferably 3500 MPa or more. By using a stretched film having such a tensile modulus, the degree of polarization reduction can be further reduced.

  The stretched film 11 can contain one or more additives such as a lubricant, a plasticizer, a dispersant, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant. When the stretched film 11 contains an ultraviolet absorber, the transmittance of the stretched film 11 at a wavelength of 380 nm is preferably 10% or less.

  In addition, a coating layer (surface treatment layer 20) can be provided on the outer surface of the stretched film 11 in order to impart desired surface optical properties or other characteristics. Specific examples of the coating layer include a hard coat layer, an antiglare layer, an antireflection layer, an antistatic layer, and an antifouling layer. The method for forming the coating layer is not particularly limited, and a known method can be used.

  In the present invention, the stretched film 11 is one having a shrinkage force in the slow axis direction of 0.2 N / 2 mm or less when the stretched film is heated at 105 ° C. The shrinkage force in the slow axis direction when the stretched film is heated at 105 ° C. is preferably 0.15 N / 2 mm or less because the degree of polarization can be further reduced. In addition, the contraction force in the slow axis direction when the stretched film is heated at 105 ° C. is 0.002 N / 2 mm or more in that the visibility when viewing the image display device through polarized sunglasses can be ensured. It is preferable. By using such a stretched film 11, it is possible to suppress the shift of the absorption axis of the polarizing film in the heat resistance test, to reduce the decrease in the degree of polarization, and to view the image display device through the polarized sunglasses. Visibility can be improved.

  The shrinkage force of the stretched film can be measured as follows. The stretched film is cut into a rectangle having a short side of 2 mm and a long side of 50 mm so that the slow axis of the stretched film coincides with the long side. The shrinkage force of the cut stretched film can be measured using a commercially available thermomechanical analyzer. The details of the measurement method follow the example section.

  Such a stretched film 11 can be produced, for example, by biaxially stretching a film containing the thermoplastic resin. More specifically, the shrinkage force and phase difference characteristics can be controlled by appropriately adjusting the stretching conditions for biaxial stretching or by annealing the stretched film.

  The stretched film 11 is at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin in that it can easily control the shrinkage force and retardation characteristics. It is preferable to contain.

  The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching, but a film produced by simultaneous biaxial stretching is preferable because a film satisfying the shrinkage force can be easily obtained. The method of simultaneous biaxial stretching is not particularly limited, but both ends of the unstretched film are gripped by chucks, the feed rates of the chucks at both ends are differentiated, and further spread in a direction (TD) perpendicular to the machine flow direction. Can be manufactured. Simultaneous biaxial stretching includes stretching in one direction and contracting the other tension by relaxing.

  In general, a long polarizing film has an absorption axis in the long side direction, so that an optical film can be bonded to a long optical film and a long polarizing film by roll-to-roll. It is preferable that it is manufactured by being stretched obliquely by biaxial stretching.

[Protective film 12]
In particular, the protective film 12 is preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. The protective film 12 preferably contains a cellulose-based resin, a polyolefin-based resin, or an acrylic resin because the retardation value is easily controlled and easily available. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.

  As the cellulose-based resin, environmental olefin-based resin, or acrylic-based resin, those similar to those exemplified for the stretched film 11 can be used.

  As a method for forming a film from the resin as described above, a method corresponding to each resin may be appropriately selected. For example, the solvent casting method, the melt extrusion method described above, or the like can be employed. Among these, for polyolefin resins and acrylic resins, the melt extrusion method is preferably employed from the viewpoint of productivity. On the other hand, a cellulose resin is generally formed into a film by a solvent casting method.

  When the liquid crystal cell is in an in-plane switching (IPS) mode, the protective film has a thickness direction retardation value Rth of −10 in order not to impair the wide viewing angle characteristics inherent in the IPS mode liquid crystal cell. It is preferably in the range of -10 nm.

  Examples of the method for controlling the retardation value Rth in the thickness direction of the protective film within a range of −10 to 10 nm include a method for minimizing the distortion remaining in the plane and in the thickness direction as much as possible. For example, in the solvent casting method, a method of relaxing residual shrinkage strain in the plane and in the thickness direction generated when the cast resin solution is dried by heat treatment can be employed. On the other hand, in the melt extrusion method, the distance from the die to the cooling drum is reduced as much as possible in order to prevent the resin film from being drawn from the die and cooled, and the extrusion amount and the rotation speed of the cooling drum are reduced. A method of controlling the film so that the film is not stretched can be employed. Moreover, the method of relieving the distortion which remains in the obtained film by heat processing similarly to the solvent casting method is also employable.

  The thickness of the protective film is preferably 90 μm or less, more preferably 60 μm or less, further preferably 40 μm or less, particularly preferably 25 μm or less, from the viewpoint of thinning the polarizing plate, and from the viewpoint of handling, preferably 5 μm or more. More preferably, it is 10 μm or more.

[Bonding of polarizing film 14 and protective film 12]
The polarizing film and the protective film can be bonded with an adhesive or a pressure-sensitive adhesive.
The adhesive layer that bonds the polarizing film and the protective film can have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. If the thickness of the adhesive layer is within this range, the protective film and the polarizing film to be laminated do not float or peel off, and an adhesive force having no practical problem can be obtained. The pressure-sensitive adhesive layer for bonding the polarizing film and the protective film can have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.

  In adhering the polarizing film and the protective film, it is also useful to perform a saponification treatment, a corona treatment, a plasma treatment or the like on the polarizing film or the protective film in advance.

  In forming the adhesive layer, an appropriate adhesive can be used as appropriate according to the type and purpose of the adherend, and an anchor coating agent can be used as necessary. Examples of the adhesive include a solvent-type adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet-adhesive, a polycondensation-type adhesive, a solventless-type adhesive, a film-type adhesive, and a hot-melt-type adhesive. Can be mentioned.

  One preferred adhesive is an aqueous adhesive, that is, an adhesive component in which the adhesive component is dissolved or dispersed in water. Examples of adhesive components that can be dissolved in water include polyvinyl alcohol resins. An example of an adhesive component that can be dispersed in water is a urethane resin having a hydrophilic group. The water-based adhesive can be prepared by mixing such an adhesive component with water together with an additional additive added as necessary. Examples of commercially available polyvinyl alcohol resins that can be used as water-based adhesives include “KL-318”, which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

  The water-based adhesive can contain a crosslinking agent as necessary. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts. When a polyvinyl alcohol resin is used as an adhesive component, an aldehyde compound such as glyoxal, a methylol compound such as methylol melamine, a water-soluble epoxy resin, or the like is preferably used as a crosslinking agent. Here, the water-soluble epoxy resin is, for example, a polyamide obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylenetriamine or triethylenetetramine and a dicarboxylic acid such as adipic acid. It can be an epoxy resin. An example of a commercially available water-soluble epoxy resin is “Smileise Resin (registered trademark) 650 (30)” sold by Taoka Kogyo Co., Ltd.

  A polarizing plate can be obtained by applying a water-based adhesive to the polarizing film and / or the adhesive surface of the protective film to be bonded to the polarizing film and bonding them together, followed by drying treatment. Prior to adhesion, it is also effective to subject the protective film to easy adhesion treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment to enhance wettability. A drying temperature can be about 50-100 degreeC, for example. After the drying treatment, curing at a temperature slightly higher than room temperature, for example, at a temperature of about 30 to 50 ° C. for about 1 to 10 days is preferable for further enhancing the adhesive force.

  Another preferred adhesive is an active energy ray-curable adhesive composition containing an epoxy compound that is cured by irradiation or heating with active energy rays. Here, the active energy ray-curable epoxy compound has at least two epoxy groups in the molecule. In this case, the adhesive between the polarizing film and the protective film is performed by irradiating the applied layer of the adhesive composition with an active energy ray or applying heat to the adhesive composition, and a curable epoxy compound contained in the adhesive. It can carry out by the method of hardening. Curing of the epoxy compound is generally performed by cationic polymerization of the epoxy compound. Further, from the viewpoint of productivity, this curing is preferably performed by irradiation with active energy rays.

  From the viewpoints of weather resistance, refractive index, cationic polymerizability, etc., the epoxy compound contained in the active energy ray-curable adhesive composition preferably does not contain an aromatic ring in the molecule. Examples of epoxy compounds that do not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. An epoxy compound that is suitably used for such an active energy ray-curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, but the outline is also described here.

  The hydrogenated epoxy compound is a glycidyl compound obtained by subjecting an aromatic polyhydroxy compound, which is a raw material of an aromatic epoxy compound, to a nuclear hydrogenated polyhydroxy compound obtained by selectively performing a nuclear hydrogenation reaction in the presence of a catalyst and under pressure. It can be etherified. Examples of the aromatic polyhydroxy compound that is a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F, and bisphenol S; And novolak type resins; polyhydroxy compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone, and polyvinylphenol. A glycidyl ether can be obtained by performing a nuclear hydrogenation reaction on such an aromatic polyhydroxy compound and reacting the resulting hydrogenated polyhydroxy compound with epichlorohydrin. Suitable hydrogenated epoxy compounds include hydrogenated glycidyl ether of bisphenol A.

  An alicyclic epoxy compound is a compound having at least one epoxy group bonded to an alicyclic ring in the molecule. The “epoxy group bonded to the alicyclic ring” means a bridged oxygen atom —O— in the structure represented by the following formula, and m is an integer of 2 to 5.

A compound in which one or more hydrogen atoms in (CH ₂ ) _m in this formula are removed and bonded to another chemical structure can be an alicyclic epoxy compound. Further, one or more hydrogen atoms in (CH ₂ ) _m forming the alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m = 3 in the above formula) or an oxabicycloheptane ring (m = 4 in the above formula) has excellent adhesion. It is preferably used from the indication. Specific examples of the alicyclic epoxy compound are listed below. Here, the compound names are given first, and then the chemical formulas corresponding to each are shown, and the same reference numerals are given to the compound names and the chemical formulas corresponding thereto.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate,
B: 3,4-epoxy-6-methylcyclohexylmethyl 3,4-epoxy-6-methylcyclohexanecarboxylate,
C: ethylene bis (3,4-epoxycyclohexanecarboxylate),
D: Bis (3,4-epoxycyclohexylmethyl) adipate,
E: bis (3,4-epoxy-6-methylcyclohexylmethyl) adipate,
F: Diethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether),
H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] henicosane,
I: 3- (3,4-epoxycyclohexyl) -8,9-epoxy-1,5-dioxaspiro [5.5] undecane,
J: 4-vinylcyclohexene dioxide,
K: Limonene dioxide
L: bis (2,3-epoxycyclopentyl) ether,
M: Dicyclopentadiene dioxide and the like.

  The aliphatic epoxy compound can be a polyglycidyl ether of an aliphatic polyhydric alcohol or an alkylene oxide adduct thereof. More specifically, diglycidyl ether of propylene glycol; diglycidyl ether of 1,4-butanediol; diglycidyl ether of 1,6-hexanediol; triglycidyl ether of glycerin; triglycidyl ether of trimethylolpropane; ethylene Polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) obtained by adding alkylene oxide (ethylene oxide or propylene oxide) to aliphatic polyhydric alcohol such as glycol, propylene glycol, and glycerin Can be mentioned.

  In the active energy ray-curable adhesive composition, the epoxy compound may be used alone or in combination of two or more. Among these, the epoxy compound preferably includes an alicyclic epoxy compound having at least one epoxy group bonded to the alicyclic ring in the molecule.

  The epoxy compound used in the active energy ray-curable adhesive composition usually has an epoxy equivalent in the range of 30 to 3,000 g / equivalent, and this epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent. is there. When an epoxy compound having an epoxy equivalent of less than 30 g / equivalent is used, there is a possibility that the flexibility of the polarizing plate after curing is lowered or the adhesive strength is lowered. On the other hand, in a compound having an epoxy equivalent exceeding 3,000 g / equivalent, compatibility with other components contained in the adhesive composition may be reduced.

  From the viewpoint of reactivity, cationic polymerization is preferably used as the curing reaction of the epoxy compound. For that purpose, it is preferable to mix | blend a cationic polymerization initiator with the active energy ray hardening-type adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating with active energy rays such as visible light, ultraviolet rays, X-rays, and electron beams, and initiates an epoxy group polymerization reaction. From the viewpoint of workability, it is preferable that the cationic polymerization initiator is provided with latency. Hereinafter, a cationic polymerization initiator that generates a cationic species or Lewis acid by irradiation of active energy rays and initiates a polymerization reaction of an epoxy group is referred to as a “photo cationic polymerization initiator”, and generates a cationic species or a Lewis acid by heat. The cationic polymerization initiator that initiates the polymerization reaction of the epoxy group is referred to as “thermal cationic polymerization initiator”.

  The method of curing the adhesive composition by irradiation with active energy rays using a cationic photopolymerization initiator enables curing at normal temperature and humidity, reducing the need to consider the distortion due to heat resistance or expansion of the polarizing film. And it is advantageous in that the protective film and the polarizing film can be satisfactorily bonded. In addition, since the cationic photopolymerization initiator acts catalytically by light, it is excellent in storage stability and workability even when mixed with an epoxy compound.

  Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts, and iron-allene complexes. The compounding quantity of a photocationic polymerization initiator is 0.5-20 weight part normally with respect to 100 weight part of epoxy compounds, Preferably it is 1 weight part or more, Preferably it is 15 weight part or less. When the blending amount of the cationic photopolymerization initiator is less than 0.5 parts by weight with respect to 100 parts by weight of the epoxy compound, curing becomes insufficient, and the mechanical strength and adhesive strength of the cured product tend to decrease. On the other hand, when the blending amount of the cationic photopolymerization initiator exceeds 20 parts by weight with respect to 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, resulting in an increase in the hygroscopic property of the cured product and durability performance. May be reduced.

  When using a photocationic polymerization initiator, the active energy ray-curable adhesive composition can further contain a photosensitizer as necessary. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include carbonyl compounds, organic sulfur compounds, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. When mix | blending a photosensitizer, it is preferable to make the quantity into the range of 0.1-20 weight part with respect to 100 weight part of active energy ray hardening-type adhesive compositions. Further, a sensitizing aid such as a naphthoquinone derivative may be used for improving the curing rate.

  On the other hand, examples of the thermal cationic polymerization initiator include benzylsulfonium salt, thiophenium salt, thioranium salt, benzylammonium, pyridinium salt, hydrazinium salt, carboxylic acid ester, sulfonic acid ester, and amine imide.

  The active energy ray-curable adhesive composition containing an epoxy compound is preferably cured by photocationic polymerization as described above, but can also be cured by thermal cationic polymerization in the presence of the thermal cationic polymerization initiator. In addition, photocationic polymerization and thermal cationic polymerization can be used in combination. When photocationic polymerization and thermal cationic polymerization are used in combination, the active energy ray-curable adhesive composition preferably contains both a photocationic polymerization initiator and a thermal cationic polymerization initiator.

  The active energy ray-curable adhesive composition may further contain a compound that promotes cationic polymerization, such as an oxetane compound or a polyol compound. An oxetane compound is a compound having a 4-membered ring ether in the molecule. When mix | blending an oxetane compound, the quantity is 5 to 95 weight% normally in an active energy ray hardening-type adhesive composition, Preferably it is 5 to 50 weight%. The polyol compound may be alkylene glycol including ethylene glycol, hexamethylene glycol, polyethylene glycol or the like, or an oligomer thereof, polyester polyol, polycaprolactone polyol, polycarbonate polyol and the like. When the polyol compound is blended, the amount thereof is usually 50% by weight or less, preferably 30% by weight or less, in the active energy ray-curable adhesive composition.

  Further, the active energy ray-curable adhesive composition is not limited to other adhesives, for example, ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastics, unless the adhesiveness is impaired. Resins, fillers, flow regulators, plasticizers, antifoaming agents, and the like can be included. Examples of the ion trapping agent include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Examples of the antioxidant include And hindered phenolic antioxidants.

  After applying the active energy ray-curable adhesive composition containing the epoxy compound to the adhesive surface of the polarizing film or the protective film, or the adhesive surface of both of them, it is bonded to the adhesive-coated surface, The polarizing film and the protective film can be adhered by curing the uncured adhesive layer by irradiating with active energy rays or heating. As an adhesive coating method, for example, various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, and a gravure coater can be adopted.

  This active energy ray-curable adhesive composition can basically be used as a solvent-free adhesive that does not substantially contain a solvent, but each coating method has an optimum viscosity range. A solvent may be included for viscosity adjustment. The solvent is preferably an organic solvent that dissolves each component including an epoxy compound well without degrading the optical performance of the polarizing film. For example, hydrocarbons typified by toluene, typified by ethyl acetate, etc. Esters can be used.

  When the adhesive composition is cured by irradiation with active energy rays, the above-mentioned various types of active energy rays can be used, but since the handling is easy and the amount of irradiation light is easy to control, ultraviolet rays are not emitted. Preferably used. Active energy rays such as ultraviolet irradiation intensity and irradiation dose do not affect various optical performance including polarization degree of polarizing film, and various optical performance including transparency and retardation characteristics of protective film. Therefore, it is determined as appropriate so as to maintain an appropriate productivity.

  When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator blended in the active energy ray-curable adhesive composition generates cationic species and Lewis acid, and the specific heating temperature is, for example, 50 to 200 ° C. Degree.

  It can also laminate | stack through the adhesive layer for bonding of the polarizing film 14 and a protective film. The pressure-sensitive adhesive layer used for laminating the polarizing film 14 and the protective film may be any layer as long as it has excellent optical transparency and excellent adhesive properties including appropriate wettability, cohesiveness, adhesiveness, etc. Those excellent in durability and the like are preferable. Specifically, as the pressure-sensitive adhesive forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferable.

  The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of an acrylic acid alkyl ester such as butyl acrylate, ethyl acrylate, isooctyl acrylate, and 2-ethylhexyl acrylate. This acrylic resin is usually copolymerized with a polar monomer. The polar monomer is a compound having a polymerizable unsaturated bond and a polar functional group. Here, the polymerizable unsaturated bond is generally derived from a (meth) acryloyl group, and the polar functional group. The group can be a carboxyl group, a hydroxyl group, an amide group, an amino group, an epoxy group, or the like. Specific examples of polar monomers include (meth) acrylic acid, 2-hydroxypropyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, (meth) acrylamide, 2-N, N-dimethylaminoethyl ( Examples include meth) acrylate and glycidyl (meth) acrylate.

  The acrylic pressure-sensitive adhesive usually contains a crosslinking agent together with the acrylic resin. A typical example of the crosslinking agent is an isocyanate compound having at least two isocyanato groups (—NCO) in the molecule.

  Various additives may be further blended in the adhesive. Suitable additives include silane coupling agents and antistatic agents. A silane coupling agent is effective in increasing the adhesive strength with glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

  The pressure-sensitive adhesive layer is prepared by preparing a pressure-sensitive adhesive composition in which the above-mentioned pressure-sensitive adhesive components are dissolved in an organic solvent, and applying this directly to one of the bonding surfaces (polarizing film or protective film). Apply the above-mentioned pressure-sensitive adhesive composition to the release-treated surface of the base film made of a resin film that has been subjected to a release treatment by a dry removal method, and dry-removing the solvent to form a pressure-sensitive adhesive layer. Can be formed by a method of sticking to any of the bonding surfaces (polarizing film or protective film) and transferring the adhesive. When the pressure-sensitive adhesive layer is formed by the former direct coating method, a resin film (also called a separator) that has been subjected to a release treatment is bonded to the surface, and the pressure-sensitive adhesive layer surface is temporarily protected until use. Is customary. The latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition that is an organic solvent solution. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer first is used. It is also advantageous in that it can be used as a separator after being attached to a polarizing plate.

  Before laminating a polarizing film and a protective film with an adhesive or pressure-sensitive adhesive, it is also useful to perform corona treatment or plasma treatment in advance on the polarizing film surface to be bonded and the stretched optical film surface or pressure-sensitive adhesive surface. It is.

[First adhesive layer 13]
The 1st adhesive layer 13 formed in the surface side on the opposite side to the bonding surface with the polarizing film 14 in the protective film 12 is excellent in optical transparency, moderate wettability, cohesiveness, adhesiveness. However, those having excellent durability and the like are preferably used. Specifically, as the pressure-sensitive adhesive forming the first pressure-sensitive adhesive layer 13, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferably used. Specifically, the same adhesive as that which can be used for laminating the polarizing film and the protective film may be used.

  The 1st adhesive layer 13 may contain various additives similarly to the adhesive layer for laminating | stacking a polarizing film and a protective film. Of these, the first pressure-sensitive adhesive layer 13 preferably contains an antistatic agent. In general, when attaching a polarizing plate to a liquid crystal cell via an adhesive layer, the surface protective film (separator) that has been temporarily protected by covering the adhesive layer is peeled off and then attached to the liquid crystal cell. The static electricity generated when the surface protective film is peeled off causes the alignment failure of the liquid crystal in the liquid crystal cell, and this phenomenon may cause the display failure of the liquid crystal display device. As a means for reducing or preventing the generation of static electricity, it is effective to add an antistatic agent to the adhesive.

  When the protective film 12 and the first pressure-sensitive adhesive layer 13 are bonded, it is also useful to perform corona treatment, plasma treatment, etc. on the surface where the protective film 12 and the first pressure-sensitive adhesive layer 13 are bonded together. is there.

[Production method of polarizing plate]
Although it does not restrict | limit especially as a method of manufacturing the polarizing plate of this invention, For example, after bonding the polarizing film 14 and the protective film 12 with a roll to roll through an adhesive agent, it adhere | attaches on the polarizing film 14 Examples thereof include a method in which the stretched film 11 is bonded by a roll-to-roll through an agent, and a method in which the stretched film 11, the polarizing film 14, and the protective film 12 are simultaneously bonded through an adhesive. Furthermore, a polarizing plate with an adhesive is obtained by forming the first adhesive layer 13 on the protective film 12. The polarizing plate with the adhesive can be bonded to the image display element via the first adhesive layer 13.

  Then, a polarizing plate having a desired shape and size can be produced by cutting the polarizing plate into a sheet. The shape of the polarizing plate is not particularly limited, but is preferably a rectangular shape having a long side and a short side. When the polarizing plate of the present invention has a rectangular shape having a long side and a short side, the ratio of the length of the long side to the length of the short side is preferably 10: 1 to 1: 1, and 2: 1 to 2: 1. More preferably, it is 1: 1. The size of the polarizing plate is preferably 50 mm or more, and more preferably 150 mm or more, and the length of the short side is preferably 40 mm or more, and 80 mm or more. It is more preferable that Specifically, the size of the polarizing plate of the present invention is, for example, preferably 2.7 type (55 mm × 41 mm) or more, more preferably 7.0 type (154 mm × 87 mm) or more, and further preferably 11.3. It is a mold (174 mm × 231 mm) or more.

[Image display device, image display device]
The image display device of the present invention includes the image display element and the polarizing plate of the present invention. Examples of the image display element include a liquid crystal cell and an organic electroluminescence (EL) display element. An image display device can be manufactured by laminating the polarizing plate of the present invention on the image display element. When the image display device is a liquid crystal display device, the polarizing plate of the present invention is preferably arranged on the viewing side.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated further more concretely, this invention is not limited by these examples. In the examples, the parts and% indicating the content or amount used are based on weight unless otherwise specified. In addition, each physical property in the following examples was measured by the following method.

(1) Measurement of thickness:
Measurement was performed using a digital micrometer “MH-15M” manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation and wavelength dispersion characteristics Film A at a temperature of 23 ° C. using a phase difference meter “KOBRA (registered trademark) -WPR” based on the parallel Nicol rotation method manufactured by Oji Scientific Instruments Co., Ltd. In-plane retardations Re (590), Re (450), Re (550), Re (630) of ~ E are measured, and Re (450) / Re (550), Re (630) / Re (550) are measured. Calculated.

(3) Measurement of polarization degree and single transmittance of polarizing plate:
The measurement was performed using a spectrophotometer with an integrating sphere [“V7100” manufactured by JASCO Corporation, 2-degree field of view; C light source].

(4) Measurement of shrinkage force of stretched film The stretched film was cut into a rectangle with a short side of 2 mm and a long side of 50 mm with a super cutter (manufactured by Hadano Seiki Co., Ltd.) so that the slow axis of the stretched film coincided with the long side. A test piece was obtained. The shrinkage force of the test piece was measured using a thermomechanical analyzer (model II TMA / 6100, manufactured by SII Nano Technology Co., Ltd.). This measurement was carried out in a constant dimension mode (the distance between chucks was set to 10 mm), and the specimen was left in the room at 20 ° C. for a sufficient period of time, and then the temperature setting in the sample room was changed from 20 ° C. to 105 ° C. in 10 minutes. The temperature was raised, and the temperature inside the sample chamber was set at 105 ° C. after the temperature was raised. After the temperature was raised, the sample was left for another 30 minutes, and then the contraction force in the long side direction of the test piece was measured in an environment of 105 ° C. In this measurement, the static load was 0 mN, and a SUS probe was used as the jig.

[Production Example 1] Polarizing plate with protective film A polyvinyl alcohol film having a thickness of 20 μm (average polymerization degree of about 2,400, saponification degree of 99.9 mol% or more) is uniaxially stretched about 5 times by dry stretching, and While maintaining the tension state, the sample was immersed in pure water at 60 ° C. for 1 minute, and then immersed in an aqueous solution having a weight ratio of iodine / potassium iodide / water of 0.05 / 5/100 at 28 ° C. for 60 seconds. Then, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 8.5 / 8.5 / 100 at 72 ° C. for 300 seconds. Subsequently, the film was washed with pure water at 26 ° C. for 20 seconds and then dried at 65 ° C. to obtain a polarizing film having a thickness of 7 μm in which iodine was adsorbed and oriented on the polyvinyl alcohol film.

  Next, 3 parts of carboxyl group-modified polyvinyl alcohol [trade name “KL-318” obtained from Kuraray Co., Ltd.] is dissolved in 100 parts of water on one side of this polarizing film, and a water-soluble epoxy resin is added to the aqueous solution. Epoxy adhesive added with 1.5 parts of a certain polyamide epoxy additive [trade name “Smiles Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30%] A polarizing plate with a protective film consisting of a protective film / polarizing film and a 13 μm-thick cyclic olefin resin film (trade name “ZF-14-013” manufactured by Nippon Zeon Co., Ltd.) Obtained.

[Production Example 2] Stretched film The following stretched films were prepared by adjusting the stretch ratio. An unstretched film was also prepared as a reference example.

Stretched film A: An unstretched triacetylcellulose (TAC) film was stretched to produce a stretched TAC film having a thickness of 40 μm. The shrinkage force in the slow axis direction of this film was 0.18 N / 2 mm.
Stretched film B: An unstretched TAC film was stretched to produce a stretched TAC film having a thickness of 40 μm. The shrinkage force in the slow axis direction of this film was 0.02 N / 2 mm.
Stretched film C: An unstretched TAC film was stretched to produce a stretched TAC film having a thickness of 40 μm. The shrinkage force in the slow axis direction of this film was 0.30 N / 2 mm.
Stretched film D: An unstretched cyclic olefin resin (COP) film was stretched to produce a stretched COP film having a thickness of 25 μm. The shrinkage force in the slow axis direction of this film was 0.002 N / 2 mm.
Unstretched film E: An unstretched TAC film having a thickness of 40 μm was produced. In either direction, the contraction force was 0.001 N / 2 mm.

  The optical properties and the like of the film are as shown in Table 1 below.

[Example 1]
On a polarizing film of a polarizing plate with a protective film, 3 parts of carboxyl group-modified polyvinyl alcohol [trade name “KL-318” obtained from Kuraray Co., Ltd.] is dissolved in 100 parts of water, and a water-soluble epoxy resin is added to the aqueous solution. Epoxy adhesive added with 1.5 parts of a certain polyamide epoxy additive [trade name “Smiles Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30%]. Was applied. A stretched film A was bonded to the surface coated with the epoxy adhesive to obtain a polarizing plate.

  The obtained polarizing plate was cut into a size of 40 mm × 40 mm, and pressure-bonded to the alkali-free glass via an adhesive so that the protective film became a bonding surface with the alkali-free glass. The adhesive state was aged by being left in an autoclave at 50 ° C. under a load of 5 kg for 20 minutes, and then left in an environment of 23 ° C./60% RH for 10 hours.

  Thereafter, in order to obtain the initial polarization degree of the obtained polarizing plate, the ultraviolet-visible spectrum of the polarizing plate in the transmission axis direction and the absorption axis direction was measured. The degree of polarization (visibility correction polarization degree) was obtained by calculation according to JIS-Z8729.

  Using a temperature and humidity chamber manufactured by ESPEC, a heat resistance test was performed in which the produced polarizing plate was left in an environment of 105 ° C. for 1 hour. Within 30 minutes immediately after removing the polarizing plate from the thermo-hygrostat, the polarization degree was measured by the same method as the measurement of the initial polarization degree. The difference between the initial degree of polarization of this polarizing plate and the degree of polarization after the heat resistance test (the amount of change in the degree of polarization) was -0.028%.

Moreover, in order to evaluate the visibility through polarized sunglasses, a polarizing plate was bonded to a liquid crystal cell via an adhesive layer to obtain a liquid crystal display device. The obtained liquid crystal display device was turned on, and the image was observed through polarized sunglasses. Observation was performed from 360 ° in all directions with respect to the screen of the liquid crystal display device, and evaluation was performed according to the following criteria.
<Visibility through polarized sunglasses>
○: The image can be viewed from any direction.
×: There is an angle at which the image cannot be visually recognized.
<Coloring through polarized sunglasses>
A: Visible without any change in color from any orientation.
○: Although there is an angle where the color change occurs, it is an acceptable level.

[Examples 2-3, Comparative Example 1, Reference Example 1]
A polarizing plate was produced in the same manner as in Example 1 except that the stretched film A was changed to stretched films B to D or unstretched film E. For each of the produced polarizing plates, the initial polarization degree and the polarization degree after the heat resistance test were measured, and the visibility and coloring evaluation through polarized sunglasses were performed. The results are shown in Table 1.

  According to the present invention, it is possible to provide a polarizing plate capable of suppressing the decrease in the degree of polarization due to the shift of the absorption axis of the polarizing film caused by the dimensional change of the optical film during the heat resistance test while improving the visibility through the polarized sunglasses. This is useful.

DESCRIPTION OF SYMBOLS 10 Polarizing plate 11 Stretched film 12 Protective film 13 1st adhesive layer 14 Polarizing film 15 Protective film 20 Surface treatment layer

Claims (7)

It has a stretched film, a polarizing film and a first pressure-sensitive adhesive layer in this order,
The angle formed between the absorption axis of the polarizing film and the slow axis of the optical film is about 45 ° or about 135 °,
The stretched film is a polarizing plate having a shrinkage force in the stretching direction of 0.2 N / 2 mm or less when heated at 105 ° C. for 30 minutes.   The polarizing plate according to claim 1, wherein the polarizing film and the stretched film are laminated via an adhesive layer, an aqueous adhesive layer, or an active energy ray-curable adhesive layer.   The polarizing plate according to claim 1 or 2, wherein the stretched film contains at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin.   The said stretched film is a polarizing plate in any one of Claims 1-3 which has a surface treatment layer in the surface on the opposite side to the surface at the side of the said polarizer. The said stretched film is a polarizing plate in any one of Claims 1-4 satisfy | filling the following formula | equation (1)-Formula (4).
(1) 100 nm ≦ R _e (590) ≦ 180 nm,
(2) 0.5 <R _th (590) / R _e (590) ≦ 0.8,
(3) 0.85 ≦ R _e (450) / R _e (550) <1.00
(4) 1.00 <R _e (630) / R _e (550) ≦ 1.1
[In formulas (1) to (4), R _e (590), R _e (450), R _e (550), and R _e (630) are in-plane positions at wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively. Represents a retardation value, and R _th (590) represents a thickness direction retardation value at a wavelength of 590 nm. ]   The polarizing plate according to claim 1, wherein the polarizing plate has a rectangular shape, and the ratio of the length of the long side to the length of the short side is 10: 1 to 1: 1.   An image display device in which the polarizing plate according to claim 1 is laminated on an image display element through the first pressure-sensitive adhesive layer.

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