KR20170059407A - Polarizing plate and image display device - Google Patents

Abstract

Provided is a polarizing plate capable of suppressing the degradation of a polarization degree due to the deviation of an absorption axis of a polarizing film caused by the dimensional change of an optical film at a heat resistance test with high visibility when polarizing sunglasses are worn. A stretched film, a polarizing film and a first adhesive layer are successively formed. An angle between the absorption axis of the polarizing film and the slow axis of the stretched film is approximately 45 or 135, and when the stretched film is heated at 105 degrees centigrade for 30 minutes, the shrinking force of the stretching direction is 0.2 N/2 mm or less.

Description

[0001] POLARIZING PLATE AND IMAGE DISPLAY DEVICE [0002]

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

2. Description of the Related Art Liquid crystal displays that are low in power consumption, operate at a low voltage, and are lightweight and thin are rapidly spreading as information display devices such as portable telephones, portable information terminals, monitors for computers, and televisions. With the development of liquid crystal technology, liquid crystal displays of various modes have been proposed, and problems of liquid crystal displays such as response speed, contrast, and narrow viewing angle (viewing angle) have been solved. In addition, when a liquid crystal display for mobile use is used, for example, in an outdoor environment, there is a case where a screen of a liquid crystal display is visually inspected in a state of wearing polarized sunglasses. In this case, It is required to have excellent visibility even when viewed on a screen.

As a method for improving the visibility when the polarizing sunglasses are used to view a screen, in order to convert linearly polarized light emitted from a polarizing plate disposed on the viewer side of an image display device such as a liquid crystal cell into elliptical (or circular) polarized light, (For example, a? / 4 wave plate) is arranged on the visual side of the polarizing plate so that the absorption axis of the polarizing film and the slow axis of the retardation plate form an angle of 45 ° or 135 ° (see Patent Documents 1 to 9 ).

Patent Document 1: JP-A-2009-122454 Patent Document 2: Japanese Patent Laid-Open Publication No. 2011-107198 Patent Document 3: Japanese Patent Laid-Open Publication No. 2011-215646 Patent Document 4: JP-A-2012-230390 Patent Document 5: JP-A-03-174512 Patent Document 6: JP-A-2013-231761 Patent Document 7: JP-A-2011-113018 Patent Document 8: JP-A-2013-182162 Patent Document 9: JP-A-2013-200445

The polarizing plate in which such a retardation plate is laminated on a polarizing film has a problem that when the polarizing plate is used in a heat resistance test, the polarization axis of the polarizing film is distorted due to the dimensional change of the retardation plate,

[1] A polarizing plate comprising 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 stretched film is about 45 ° or about 135 °,

Wherein the stretched film has a shrinking force in the stretching direction of 0.2 N / 2 mm or less when heated at 105 캜 for 30 minutes.

[2] A polarizing plate according to [1], wherein the polarizing film and the stretched film are laminated via a pressure-sensitive adhesive layer, an aqueous adhesive layer or an active energy ray-curable adhesive layer.

[3] The stretched film according to [1] or [2], wherein the stretched film comprises 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) .

[4] The polarizer 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 polarizing film side.

[5] The polarizer 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)

_{(3) 0.85≤R e (450)} / R e (550) <1.00

(4) 1.00 < R _e (630) / R _e (550)

[Formula (1) to equation _{(4), R e (590} ), R e (450), R e (550), R e (630) are respectively the wavelength 590 nm, 450 nm, 550 nm , 630 nm in And R _th (590) represents the thickness direction retardation value at a wavelength of 590 nm.

[6] The polarizer according to any one of [1] to [5], wherein the polarizer 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.

[7] The image display apparatus according to any one of [1] to [6], wherein the polarizing plate is laminated on the image display element through the first pressure-sensitive adhesive layer.

According to the present invention, there is provided a polarizing plate capable of suppressing a decrease in polarization degree due to a displacement of an absorption axis of a polarizing film caused by a dimensional change of an optical film at the time of a heat resistance test while making the visibility in a state of wearing polarized sunglasses good can do.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is an example of a cross-sectional schematic diagram showing a layer structure of a polarizing plate according to the present invention. Fig.

The layer structure of the polarizing plate of the present invention will be described with reference to Fig. As shown in Fig. 1, the polarizing plate 10 of the present invention has a stretched film 11, a polarizing film 14 and a first pressure-sensitive adhesive layer 13 in this order.

It is preferable that the stretched film 11 and the polarizing film 14 are laminated and the stretched film 11 and the polarizing film 14 are laminated so that the pressure-sensitive adhesive layer, the water-based adhesive layer or the active energy ray- 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 the heat resistance test can be suppressed, and the decrease in polarization degree can be further suppressed.

When the polarizing plate 10 of the present invention is incorporated into an image display apparatus, the stretched film 11 is often disposed on the viewer's side of the polarizing plate, It is preferable that the surface treatment layer 20 is provided on the surface opposite to the bonding surface with the surface treatment layer 20.

Hereinafter, members constituting the image display apparatus of the present invention will be described in detail.

[Polarizing Film (14)]

The polarizing film 14 is usually formed by a process of uniaxially stretching a polyvinyl alcohol-based resin film, a process of adsorbing a dichroic dye by staining the polyvinyl alcohol-based resin film with a dichroic dye, a process of adsorbing a dichroic dye- A step of cross-linking an alcoholic resin film with an aqueous solution of boric acid and a step of washing with water after a cross-linking treatment with an aqueous solution of boric acid.

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 other monomers 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-based resin is usually 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 may be used. The polymerization degree of the polyvinyl alcohol-based resin is usually about 1,000 to 10,000, preferably about 1,500 to 5,000.

Such a polyvinyl alcohol-based resin film is used as the original film of the polarizing film. The method of forming the polyvinyl alcohol-based resin is not particularly limited, and a film can be formed by a known method. The film thickness of the polyvinyl alcohol-based resin original film is, for example, about 10 to 100 m, and preferably about 10 to 50 m.

The longitudinal uniaxial stretching of the polyvinyl alcohol-based resin film can be performed before, simultaneously with, or after dyeing with a dichroic dye. When the longitudinal uniaxial stretching is carried out after dyeing, the longitudinal uniaxial stretching may be carried out before the boric acid treatment or during the boric acid treatment. Of course, longitudinal uniaxial stretching may be performed at a plurality of steps described herein. As the vertical uniaxial stretching, a method of uniaxially stretching between rolls having different circumferential velocities, a method of stretching uniaxially using a heat roll, or the like can be adopted. The vertical uniaxial stretching may be performed by dry stretching in air or may be performed by wet stretching in which the polyvinyl alcohol based resin film is stretched by using a solvent such as water. The stretching magnification is usually about 3 to 8 times.

The dyeing by the dichroic dye of the polyvinyl alcohol-based resin film can be performed, for example, by a method of immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. As the dichroic dye, specifically iodine or a dichroic organic dye is used. It is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment in which it is immersed in water and subjected to swelling before dyeing.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol resin film is dipped in an aqueous solution containing iodine and potassium iodide is generally 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. The temperature of the aqueous solution used for dyeing is normally about 20 to 40 캜. 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 in which a polyvinyl alcohol-based resin film is dipped in an aqueous solution containing a water-soluble dichroic organic dye is employed. The content of the dichroic organic dye in the 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. The dye aqueous solution may contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the dichroic organic dye aqueous solution used for dyeing is usually about 20 to 80 캜. 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 dipping the dyed polyvinyl alcohol resin film in an aqueous solution containing boric acid. The content of boric acid 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, it is preferable that the aqueous solution containing boric acid 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 immersing 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 占 폚 or higher, preferably 50 to 85 占 폚, and more preferably 60 to 80 占 폚.

The polyvinyl alcohol resin film after boric acid treatment is usually subjected to water washing treatment. The water washing treatment can be carried out, for example, by 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 캜. The immersion time is usually about 1 to 120 seconds.

After washing with water, drying treatment is carried out to obtain a polarizing film. The drying treatment can be performed using a hot-air dryer or a far-infrared heater. The temperature of the drying treatment is usually about 30 to 100 占 폚, preferably 50 to 80 占 폚. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. By the drying treatment, the water content in the polarizing film is reduced to practical use. The water content thereof is usually about 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the flexibility of the polarizing film is lost, which may be damaged or broken after drying. When 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.

The polarizing film 14 preferably has a shrinking force of 3 N / 2 mm or less in the absorption axis direction when the polarizing film is heated at 80 캜, and more preferably 1.5 N / 2 mm or less.

The shrinkage force in the direction of the transmission axis when the polarizing film is heated at 80 DEG C is preferably 3 N / 2 mm or less, more preferably 1.5 N / 2 mm or less. By using such a polarizing film, the shrinkage of the polarizing film when provided in the heat resistance test can be reduced, and the lowering of the polarization degree can be further reduced.

The shrinking force of the polarizing film can be measured by the same method as the shrinking force of the stretched film described later. At this time, "ground shaft" shall be read in "absorption axis" or "transmission axis".

In order to suppress the shrinking force of the polarizing film 14 to a low level, for example, the thickness of the polarizing film 14 is preferably 15 m or less, more preferably 12 m or less. The thickness of the polarizing film is usually 3 占 퐉 or more in that good optical characteristics can be imparted. It is also useful to adjust the conditions of the drying treatment.

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 still more preferably 3 or more.

The ratio of the thickness of the stretched film 11 to the thickness of the polarizing film 14 is preferably 7 or less. By the combination of these thickness ratios, the contraction of the polarizing film 14 can be suppressed by the stretched film, and the shrinkage of the stretched film is also easily set within the range defined in the present invention.

The stretching, dyeing, boric acid treatment, washing and drying steps of the polyvinyl alcohol based resin film in the production process of the polarizing film 14 can be carried out, for example, in accordance with the method described in Japanese Patent Application Laid- You can do it. It is also useful to use a method of forming a polyvinyl alcohol-based resin layer to be a polarizer by coating a polyvinyl alcohol-based resin on a base film like the method described in this document.

[Stretch film (11)]

In the polarizing plate used in the present invention, the stretched film 11 is preferably made of a material having particularly excellent transparency, mechanical strength, thermal stability, moisture barrier property, and the like. For example, polyolefin resins such as a chain polyolefin resin (polypropylene resin and the like) and a cyclic polyolefin resin (norbornene resin and the like); Cellulose-based resins such as cellulose triacetate and cellulose diacetate; Polyester-based resin; Polycarbonate resin; (Meth) acrylic resins; Polystyrene type resin; Or a mixture or copolymer thereof, and the like.

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)

3 <1.00 and _{0.85≤R e (450) / R e} (550)

(4) 1.00 < R _e (630) / R _e (550)

Is preferable. _{Formula, R e (590), R} e (450), R e (550), R e (630) represents the in-plane retardation value in the measuring wavelength 590 nm, 450 nm, 550 nm , 630 nm , respectively, R _th (590) represents the retardation value in the thickness direction at the measurement wavelength of 590 nm. These in-plane retardation values and thickness retardation values are measured under an environment of a temperature of 23 캜 and a relative humidity of 55%.

In-plane retardation value R _e, a retardation value R _th in the thickness direction of the stretched film 11 has a refractive index of the refractive index in the in-plane slow axis direction, n _x, the in-plane fast axis direction (direction perpendicular to the in-plane slow axis direction), n _y, The refractive index in the thickness direction is n _z , and the thickness of the stretched film 11 is d, the following formula:

R _e = (n _x -n _y ) x d

_{R th = [{(n x} + n y) / 2} -n z] × d

.

In the liquid crystal display in which the stretched film 11 showing the retardation characteristics and the wavelength dispersion characteristics of the above-mentioned formulas (1) to (4) is arranged on the viewer side, the polarized sunglasses were used and the screen was viewed in various directions (azimuth angle and polar angle) It is possible to effectively suppress the change in color tone and improve the visibility of the liquid crystal display. On the other hand, when any one or more of the above-mentioned expressions (1) to (4) are not satisfied, the suppression of the hue change may become insufficient.

R _e (590) in the formula (1) is preferably 105 to 170 nm, and R _th (590) / R _e (590) in the formula (2) R _e (450) / R _e (550) in the formula (3) is preferably from 0.86 to 0.98, and R _e (630) / R _{and 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 circularly polarized light) The angle formed between the absorption axis of the polarizing film and the slow axis of the optical film is laminated so as to be approximately 45 DEG or approximately 135 DEG. When the angle formed is outside this range, a function of converting linearly polarized light into elliptically polarized light and outputting it can not be obtained. As a result, the suppression of the change in color tone may become insufficient. In the present invention, about 45 ° or about 135 ° means 25 to 65 ° or 115 to 155 °, preferably 35 to 55 ° or 125 to 145 °, more preferably 40 to 55 °, 50 DEG or 130 DEG to 140 DEG.

Since the retardation and wavelength dispersion characteristics of the above formulas (1) to (4) are easily imparted and the humidity resistance is relatively low, moisture resistance and heat and humidity resistance of the optical laminate can be improved, , A cyclic polyolefin-based resin, a polycarbonate-based resin, a cellulose-based resin, a polyester-based resin, or a (meth) acrylic-based resin, or a resin containing two or more thereof. Is more preferable.

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.

The cyclic polyolefin-based resin is a generic name of a resin that is polymerized using a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include ring-opened (co) polymers of cyclic olefins, addition polymers of cyclic olefins, copolymers (typically, random copolymers) of cyclic olefins and chain olefins such as ethylene and propylene, Graft polymers modified with carboxylic acids and derivatives thereof, and hydrides thereof. Among them, a norbornene resin using a norbornene monomer such as norbornene or a polycyclic norbornene monomer as the cyclic olefin is preferably used.

The cellulose ester resin is an ester of cellulose and a fatty acid. Specific examples of the cellulose ester-based resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. These copolymers and those obtained by modifying a part of hydroxyl groups with other substituents may also be used. Of these, cellulose triacetate (triacetylcellulose: TAC) is particularly preferable.

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

Specific examples of the polyester-based resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, polytrimethylene terephthalate, polytrimethylene naphthalate, polycyclohexanedimethyl terephthalate, polycyclohexane Dimethyl naphthalate.

The polycarbonate resin is composed of a polymer having a monomer unit bonded through a carbonate group. The polycarbonate resin may be a resin such as a modified polycarbonate having modified polymer skeleton, a copolymerized polycarbonate, or the like.

The (meth) acrylic resin is a resin mainly composed of a compound having a (meth) acryloyl group. Specific examples of the (meth) acrylic resin include 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 acid ester- (meth) acrylic acid copolymer; (Meth) acrylate-styrene copolymer (MS resin and the like); A copolymer of methyl methacrylate and a compound having an alicyclic hydrocarbon group (e.g., methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate- (meth) acrylate norbornyl copolymer, etc.) . Preferably, a polymer mainly composed of a poly (meth) acrylate C _1-6 alkyl ester such as poly (meth) acrylate is used, more preferably methyl methacrylate as a main component (50 to 100 wt% By weight, preferably 70 to 100% by weight) is used.

The stretched film 11 can be produced by stretching the film containing the thermoplastic resin. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine direction (MD) of the unstretched film, a direction (TD) orthogonal to the machine direction, and a direction of slacking in the machine direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which two stretching directions are simultaneously performed, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction. In the stretching treatment, for example, stretching in the machine direction (machine direction: MD) using two or more pairs of nip rolls having a larger peripheral speed at the exit side, or grasping both ends of the unstretched film with a chuck, In the direction (TD) in which the light beam is emitted. At this time, it is possible to control the retardation value and the wavelength dispersion within the ranges of the above-mentioned formulas (1) to (2) by adjusting the film thickness or the stretching magnification. Further, by adding a wavelength dispersion regulating agent to the resin, it is possible to control the wavelength dispersion value within the range of the above-mentioned formulas (3) to (4).

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

The tensile modulus of the stretched film at 80 캜 is preferably at least 2000 MPa, and more preferably at least 3500 MPa. By using such a stretched film having a tensile modulus of elasticity, the lowering of the degree of polarization can be further reduced.

The stretched film 11 may 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 to impart desired surface optical characteristics 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.

As the stretched film 11 in the present invention, a stretched film having a contraction force in the direction of the slow axis when heated at 105 캜 is 0.2 N / 2 mm or less is used. The shrinkage force in the slow axis direction when the stretched film is heated at 105 DEG C is preferably 0.15 N / 2 mm or less in that the lowering of the polarization degree can be made smaller. It is also preferable that the stretching film has a shrinkage force in the direction of the slow axis when heated at 105 DEG C of 0.002 N / 2 mm or more in that the polarizing sunglasses can protect the visibility when viewing the image display device. By using such a stretched film 11, it is possible to suppress the deviation of the absorption axis of the polarizing film in the heat resistance test, thereby making it possible to reduce the degree of polarization deterioration and to improve the visibility when viewing the image display apparatus by using polarized sunglasses It can be made good.

The shrinking 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 shrinking force of the cut stretched film can be measured using a commercially available thermomechanical analyzer. The details of the measurement method are as described in the examples.

Such a stretched film 11 can be produced, for example, by biaxially stretching a film containing the thermoplastic resin. More specifically, the stretching force and the retardation characteristics can be controlled by suitably controlling the stretching conditions at the time of biaxial stretching or annealing the stretched film.

The stretched film 11 is preferably 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 It is preferable to include one species.

The stretching method may be simultaneous biaxial stretching or continuous biaxial stretching, but a film produced by simultaneous biaxial stretching is preferable because it is easy to obtain a film satisfying the shrinking force. The simultaneous biaxial stretching method is not particularly limited, but it is possible to grasp both ends of the unstretched film by chucking and to widen in the direction TD perpendicular to the machine flow direction, Can be manufactured. The simultaneous biaxial stretching may include stretching in one direction and shrinking in another stretch.

In general, a long polarizing film has an absorption axis in a long side direction. Therefore, in view of being able to bond a long optical film and a long polarizing film to each other in a roll film, the optical film is stretched diagonally by biaxial stretching Is preferably produced.

[Protection film (12)]

The protective film 12 is preferably made of a material having particularly excellent transparency, mechanical strength, thermal stability, moisture barrier property, and the like. As the protective film 12, it is preferable to include a cellulose resin, a polyolefin resin, or an acrylic resin because the control of the retardation value is easy and easy to obtain. The polyolefin resin referred to herein includes a chain polyolefin resin and a cyclic polyolefin resin.

As the cellulose-based resin, the cyclic olefin-based resin or the acrylic-based resin, those exemplified in the stretched film 11 can be used.

The film forming method using the resin as described above may appropriately select the method depending on each resin. For example, the above-mentioned solvent casting method, melt extrusion method and the like can be adopted. Among them, a melt extrusion method is preferably employed for polyolefin resins and acrylic resins from the viewpoint of productivity. On the other hand, the cellulose resin is generally formed by a solvent casting method.

When the liquid crystal cell is in an in-plane switching (IPS) mode, since the optical viewing angle characteristic inherent to the IPS mode liquid crystal cell is not impaired, the protective film has a retardation value Rth in the thickness direction of -10 to 10 nm Is preferable.

As a method for controlling the retardation value Rth in the thickness direction of the protective film within the range of -10 to 10 nm, there is a method of minimizing the deformation remaining in the plane and in the thickness direction when the film is produced. For example, in the above-mentioned solvent casting method, there can be adopted a method in which the residual shrinkage deformation in the plane and in the thickness direction, which occurs when the cast (cast) resin solution is dried, is relaxed by heat treatment. On the other hand, in the melt extrusion method, in order to prevent the resin film from extruding from the die and being stretched until it is cooled, the distance from the die to the cooling drum is shortened as much as possible and the extrusion amount and the rotation speed A method of controlling the film so as not to be stretched can be adopted. Also, in the same manner as in the solvent casting method, a method of relaxing the deformation remaining in the obtained film by heat treatment can be employed.

The thickness of the protective film is preferably 90 占 퐉 or less, more preferably 60 占 퐉 or less, further preferably 40 占 퐉 or less, particularly preferably 25 占 퐉 or less, from the viewpoint of thinning of the polarizing plate, , Preferably not less than 5 mu m, and more preferably not less than 10 mu m.

[Bonding of polarizing film 14 and protective film 12]

The polarizing film and the protective film can be bonded by an adhesive or a pressure-sensitive adhesive.

The thickness of the adhesive layer for bonding the polarizing film and the protective film can be about 0.01 to 30 mu m, preferably 0.01 to 10 mu m, more preferably 0.05 to 5 mu m. When the thickness of the adhesive layer is within this range, no peeling or peeling occurs between the protective film and the polarizing film to be laminated, and an adhesive force with no problem in practical use can be obtained. The pressure-sensitive adhesive layer for bonding the polarizing film and the protective film may have a thickness of about 5 to 50 mu m, preferably 5 to 30 mu m, more preferably 10 to 25 mu m.

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

For forming the adhesive layer, an appropriate adhesive may be appropriately used depending on the type and purpose of the adherend, and if necessary, an anchor coat agent may also be used. Examples of the adhesive include a solvent type adhesive, an emulsion type adhesive, a pressure-sensitive adhesive, a re-wetting adhesive, a polycondensation adhesive, a solventless adhesive, a film type adhesive and a hot melt type adhesive.

As an example of a preferable adhesive, an aqueous adhesive, that is, an adhesive component is dissolved or dispersed in water. Examples of the water-soluble adhesive component include a polyvinyl alcohol-based resin. Examples of the adhesive component dispersible in water include urethane-based resins having a hydrophilic group. The water-based adhesive can be prepared by mixing such an adhesive component with water together with an additional additive which is optionally compounded. Examples of a commercially available polyvinyl alcohol-based resin that can be an aqueous adhesive include "KL-318 " which is a carboxyl group-modified polyvinyl alcohol sold by Kabushiki Kaisha Kuraray.

The aqueous adhesive may contain a crosslinking agent as required. Examples of the crosslinking agent include amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, polyvalent metal salts and the like. When a polyvinyl alcohol-based resin is used as an adhesive component, an aldehyde compound including glyoxal, a methylol compound including methylolmelamine, a water-soluble epoxy resin, and the like are preferably used as a crosslinking agent.

Here, the water-soluble epoxy resin may be a polyamide obtained by reacting epichlorohydrin with a polyamide polyamine which is a reaction product of a polyalkylene polyamine such as diethylene triamine or triethylene tetramine with a dicarboxylic acid such as adipic acid, Epoxy resin. Examples of commercial products of water-soluble epoxy resins include "Sumirez resin (registered trademark) 650 (30) " sold by Daoka Kagaku Kogyo K.K.

A polarizer can be obtained by applying an aqueous adhesive to the adhesive surface of the polarizing film and / or the protective film to be bonded thereto and bonding them together, followed by drying treatment. Prior to the adhesion, it is also effective to increase the wettability of the protective film by subjecting the protective film to a bonding treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment. The drying temperature may be, for example, about 50 to 100 占 폚. After the drying treatment, curing at a temperature slightly higher than the room temperature, for example, about 30 to 50 占 폚 for about 1 to 10 days is preferable in further increasing the adhesive force.

As another preferable adhesive, there is an active energy ray curable adhesive composition containing an epoxy compound which is cured by irradiation with an active energy ray or heating. Here, the active energy ray-curable epoxy compound has at least two epoxy groups in the molecule. In this case, the polarizing film and the protective film can be adhered to each other by irradiating an actinic energy ray or applying heat to the applied layer of the adhesive composition to cure the curable epoxy compound contained in the adhesive . The curing of the epoxy compound is generally carried out by cationic polymerization of the epoxy compound. Further, from the viewpoint of productivity, this curing is preferably carried out by irradiation of active energy rays.

From the viewpoints of weatherability, refractive index, cationic polymerizability and the like, it is preferable that the epoxy compound contained in the active energy ray-curable adhesive composition does not contain an aromatic ring in the molecule. Examples of the epoxy compound that does not contain an aromatic ring in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, aliphatic epoxy compounds, and the like. An epoxy compound 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 it will also be schematically described here.

The hydrogenated epoxy compound may be a glycidyl etherified product of a nuclear hydrogenated polyhydroxy compound obtained by subjecting an aromatic polyhydroxy compound as a raw material of an aromatic epoxy compound to a nuclear hydrogenation reaction selectively in the presence of a catalyst and under pressure . Examples of the aromatic polyhydroxy compound as a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F and bisphenol S; Novolak type resins such as phenol novolak resin, cresol novolak resin and hydroxybenzaldehyde phenol novolac resin; Polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone and polyvinylphenol, and the like. The glycidyl etherification can be carried out by subjecting the aromatic polyhydroxy compound to a nuclear hydrogenation reaction and then reacting the obtained nucleus hydrogenated polyhydroxy compound with epichlorohydrin. Suitable hydrogenated epoxy compounds include glycidyl ethers of hydrogenated bisphenol A.

The 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 bridging oxygen atom -O- in the structure represented by the following formula, wherein 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 bonded to other chemical structures may be an alicyclic epoxy compound. One or more hydrogen atoms in (CH ₂ ) _m forming an alicyclic ring may be appropriately substituted with a straight chain alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (wherein m = 3 in the above formula) or an oxabicycloheptane ring (in which m = 4 in the above formula) has excellent adhesiveness So that it is preferably used. Specific examples of the alicyclic epoxy compound are given below. Here, the compound names are given first, and then the corresponding chemical formulas are shown. The compound names and the corresponding chemical formulas are given the same reference numerals.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylate, 3,4-

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-epoxycyclohexylmethyl ether),

G: ethylene glycol bis (3,4-epoxycyclohexylmethyl ether),

H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispyro [5.2.2.5.2.2] heneic acid,

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 may 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; A polyglycidyl ether of a polyether polyol (e.g., a diglycidyl ether of polyethylene glycol) obtained by adding an alkylene oxide (ethylene oxide or propylene oxide) to an aliphatic polyhydric alcohol such as ethylene glycol, propylene glycol and glycerin .

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

The epoxy compound used in the active energy ray-curable adhesive composition usually has an epoxy equivalent within a range of 30 to 3,000 g / equivalent, and the epoxy equivalent is preferably in the range of 50 to 1,500 g / equivalent. 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 and the adhesive strength is lowered. On the other hand, in a compound having an epoxy equivalent of more than 3,000 g / equivalent, there is a possibility that compatibility with other components contained in the adhesive composition is lowered.

From the viewpoint of reactivity, cationic polymerization is preferably used as a curing reaction of an epoxy compound. For this purpose, it is preferable to incorporate a cationic polymerization initiator into the active energy ray-curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates a cationic species or a Lewis acid by irradiation or heating of an active energy ray such as visible light, ultraviolet ray, X-ray and electron beam to initiate polymerization reaction of the epoxy group. From the viewpoint of workability, it is preferable that the cationic polymerization initiator is given a potential. Hereinafter, a cationic polymerization initiator for generating a cationic species or a Lewis acid by irradiation of an active energy ray to initiate a polymerization reaction of an epoxy group is referred to as a &quot; photocationic polymerization initiator &quot;, and a cationic species or a Lewis acid is generated by heat to generate an epoxy group The cationic polymerization initiator for initiating the polymerization reaction is referred to as &quot; thermal cationic polymerization initiator &quot;.

The method of curing the adhesive composition by irradiation of an active energy ray using a cationic ion polymerization initiator enables curing at room temperature and normal humidity to reduce the need to consider deformation due to heat resistance or expansion of the polarizing film, It is advantageous in that the film and the polarizing film can be favorably adhered. Further, since the photocationic polymerization initiator acts catalytically with light, even when mixed with an epoxy compound, the storage stability and workability are excellent.

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 blending amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and more preferably 15 parts by weight or less, based on 100 parts by weight of the epoxy compound.

If the blending amount of the photocationic polymerization initiator is less than 0.5 parts by weight based on 100 parts by weight of the epoxy compound, the curing becomes insufficient and the mechanical strength and the adhesive strength of the cured product tend to be lowered.

On the other hand, if the compounding amount of the photocationic polymerization initiator is more than 20 parts by weight based on 100 parts by weight of the epoxy compound, the ionic substance in the cured product increases, thereby increasing the hygroscopicity of the cured product and possibly lowering the durability.

When a photocationic polymerization initiator is used, the active energy ray-curable adhesive composition may further contain a photosensitizer, if necessary. By using a photosensitizer, the reactivity of the cationic polymerization can be improved, and the mechanical strength and adhesive strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfur compound, a persulfide compound, a redox compound, an azo compound, a diazo compound, a halogen compound, a light reducing pigment and the like. When the photosensitizer is blended, the amount thereof is preferably within a range of 0.1 to 20 parts by weight based on 100 parts by weight of the active energy ray curable adhesive composition. Further, in order to improve the curing rate, a sensitizer such as a naphthoquinone derivative may be used.

On the other hand, examples of the thermal cationic polymerization initiator include benzylsulfonium salts, thiophenium salts, thioronium salts, benzylammonium, pyridinium salts, hydrazinium salts, carboxylic acid esters, sulfonic acid esters and amine imides.

The active energy ray-curable adhesive composition containing an epoxy compound is preferably cured by light-ionic polymerization as described above, but it may be cured by thermal cationic polymerization in the presence of the thermal cationic polymerization initiator described above, And thermal cationic polymerization may be used in combination. When the cationic ion polymerization and the thermal cation polymerization are used in combination, it is preferable that the active energy ray-curable adhesive composition contains both a cationic polymerization initiator and a thermal cationic polymerization initiator.

Further, the active energy ray-curable adhesive composition may further contain a compound that promotes cation polymerization such as an oxetane compound or a polyol compound. The oxetane compound is a compound having a 4-membered ring ether in the molecule. When the oxetane compound is compounded, the amount thereof is usually 5 to 95% by weight, preferably 5 to 50% by weight, in the active energy ray-curable adhesive composition. The polyol compound may be an alkylene glycol or an oligomer thereof, such as ethylene glycol, hexamethylene glycol, or polyethylene glycol, a polyester polyol, a polycaprolactone polyol, a polycarbonate polyol, or the like. When blending the polyol compound, the amount thereof is generally 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 may contain other additives such as an ion trapping agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin, a filler, Plasticizers, antifoaming agents, and the like. Examples of the ion trap agent include inorganic compounds including powdery bismuth, antimony, magnesium, aluminum, calcium, titanium, and mixtures thereof. Examples of the antioxidant include hindered Phenol antioxidants and the like.

An active energy ray curable adhesive composition containing an epoxy compound is coated on the adhesive surface of the polarizing film or the protective film or both the adhesive surfaces thereof and then bonded on the coated surface of the adhesive to irradiate the active energy ray or to heat Whereby the uncured adhesive layer can be cured to adhere the polarizing film and the protective film. As the coating method of the adhesive, 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 agent substantially not containing a solvent. However, since each coating method has an optimum viscosity range, a solvent may be added for viscosity adjustment . The solvent is preferably an organic solvent that dissolves each component including the epoxy compound well without deteriorating the optical performance of the polarizing film. Examples thereof include hydrocarbons typified by toluene, esters typified by ethyl acetate, and the like. Can be used.

When the adhesive composition is cured by irradiation of an active energy ray, various kinds of the above-mentioned active energy rays can be used. However, ultraviolet rays are preferably used because they are easy to handle and easily control the amount of irradiation light. The irradiation intensity or irradiation amount of an active energy ray, for example, ultraviolet ray is suitably adjusted so as not to affect various optical performances including the polarization degree of the polarizing film and various optical performances including transparency and retardation characteristics of the protective film .

When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, the thermal cationic polymerization initiator mixed in the active energy ray-curable adhesive composition is heated at a temperature not lower than a temperature at which a cationic species or Lewis acid is generated, and the specific heating temperature is, for example, about 50 to 200 캜.

It is also possible to laminate the polarizing film 14 and the protective film via a pressure-sensitive adhesive layer. The pressure-sensitive adhesive layer to be used for the lamination of the polarizing film 14 and the protective film may be any one having excellent optical transparency and excellent adhesive properties including appropriate wettability, cohesiveness and adhesiveness, and further preferably excellent in durability and the like . Specifically, as the pressure-sensitive adhesive for forming the pressure-sensitive adhesive layer, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferable.

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

The acrylic pressure sensitive adhesive is usually blended with a crosslinking agent together with an acrylic resin. As typical examples of the crosslinking agent, there can be mentioned isocyanate compounds having at least two isocyanato groups (-NCO) in the molecule.

The pressure-sensitive adhesive may further contain various additives. Suitable additives include silane coupling agents and antistatic agents. The silane coupling agent is effective in enhancing adhesion to glass. The antistatic agent is effective in reducing or preventing the generation of static electricity.

The pressure-sensitive adhesive layer can be formed by a method of preparing a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component as described above is dissolved in an organic solvent, applying the pressure-sensitive adhesive composition directly to a bonding surface (polarizing film or protective film), drying and removing the solvent, The pressure-sensitive adhesive composition described above is applied to the release-treated surface of the base film made of the resin film, and the solvent is removed by drying to form a pressure-sensitive adhesive layer, which is adhered to any of the bonding surfaces (polarizing film or protective film) Method can be formed. When a pressure-sensitive adhesive layer is formed by a direct coating method using an electron, it is customary to bond a surface of a resin film (also referred to as a separator) subjected to release treatment to the surface thereof and temporarily adhere and protect the surface of the pressure- The latter transfer method is widely used in view of handling properties of the pressure-sensitive adhesive composition which is an organic solvent solution. In this case, the release-treated base film used for forming the pressure-sensitive adhesive layer at the beginning is adhered to the polarizer, It is also suitable for being able to be.

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

[First pressure-sensitive adhesive layer (13)]

The first pressure-sensitive adhesive layer 13 formed on the surface side of the protective film 12 opposite to the surface to be bonded to the polarizing film 14 is excellent in optical transparency and has appropriate wettability, cohesiveness, . However, it is preferable to use one having excellent durability and the like. Specifically, as the pressure-sensitive adhesive for forming the first pressure-sensitive adhesive layer 13, a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive) is preferably used. Specifically, a pressure-sensitive adhesive that can be used for laminating the polarizing film and the protective film may be used.

The first pressure sensitive adhesive layer 13 may contain various additives in the same manner as the pressure sensitive adhesive layer for laminating the polarizing film and the protective film. Among them, the first pressure sensitive adhesive layer 13 preferably contains an antistatic agent. Generally, when a polarizing plate is attached to a liquid crystal cell through a pressure-sensitive adhesive layer, the surface protective film (separator) which has been temporarily adhered and protected by covering the pressure-sensitive adhesive layer until then is peeled off and then bonded to the liquid crystal cell. The static electricity may cause defective orientation of liquid crystal in the liquid crystal cell, and this phenomenon may cause display failure of the liquid crystal display device. It is effective to add an antistatic agent to the pressure-sensitive adhesive as a means for reducing or preventing the generation of such static electricity.

When joining the protective film 12 and the first pressure-sensitive adhesive layer 13, it is also effective to perform corona treatment, plasma treatment, or the like on the surface to which the protective film 12 and the first pressure-sensitive adhesive layer 13 are bonded.

[Polarizing plate production method]

The method for producing the polarizing plate of the present invention is not particularly limited. For example, after the polarizing film 14 and the protective film 12 are bonded to each other with a roll roll, 11) with a roll roll, or a method of simultaneously bonding the stretched film 11, the polarizing film 14, and the protective film 12 with an adhesive. Further, by forming the first pressure-sensitive adhesive layer 13 on the protective film 12, a polarizer having a pressure-sensitive adhesive can be obtained. The polarizing plate having a pressure-sensitive adhesive can be bonded to the image display device through the first pressure-sensitive adhesive layer (13).

Then, the polarizing plate is cut into a single sheet of paper to produce a polarizing plate having a desired shape and size. The shape of the polarizing plate is not particularly limited, but is preferably a rectangular shape having long sides and short sides. When the polarizing plate of the present invention has a rectangular shape with long sides and short sides, the ratio of the length of the long side to the length of the short side is preferably 10: 1 to 1: 1, more preferably 2: 1 to 1: 1 Do. The length of the long side of the polarizing plate is preferably 50 mm or more, more preferably 150 mm or more, and the length of the short side is preferably 40 mm or more, more preferably 80 mm or more. Specifically, the size of the polarizing plate of the present invention is preferably 2.7 mm (55 mm x 41 mm) or more, more preferably 7.0 mm (154 mm x 87 mm) or more, and more preferably 11.3 mm mm x 231 mm).

[Image display element, image display device]

An image display apparatus of the present invention comprises an image display element and a 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 apparatus can be manufactured by laminating the polarizing plate of the present invention on the image display element. When the image display apparatus is a liquid crystal display apparatus, it is preferable that the polarizing plate of the present invention is disposed on the viewer side.

[Example]

The present invention will be described in more detail with reference to the following examples, but the present invention is not limited to these examples. In the examples, parts and% indicating the content or amount are based on the weight unless otherwise specified. In addition, the respective properties in the following examples were measured by the following methods.

(1) Measurement of thickness:

Was measured using a digital micrometer "MH-15M" manufactured by Nikon Corporation.

(2) Measurement of in-plane retardation value and wavelength dispersion characteristics

Plane retardation value Re (590) of the films A to E at a temperature of 23 占 폚 using a phase difference meter "KOBRA (registered trademark) -WPR" based on a parallel Nicol rotation method manufactured by Oji Keisukei Kikai Co., Re (450) / Re (550) and Re (630) / Re (550) were calculated by measuring Re (450), Re (550) and Re (630)

(3) Measurement of Polarizability and Bulk Transmittance of Polarizer:

A spectrophotometer having an integrating sphere (&quot; V7100 &quot; manufactured by Nippon Bunko Co., Ltd., 2 degrees viewing angle; C light source].

(4) Measurement of shrinkage force of stretched film

The stretched film was cut out with a super cutter (manufactured by Ogino Seiki Seisakusho Co., Ltd.) with a rectangle of 2 mm in short side and 50 mm in long side so that the slow axis of the stretched film coincided with the long side. The shrinkage force of the test piece was measured using a thermomechanical analyzer (Type TMA / 6100, manufactured by SAI, Nanotechnology Co., Ltd.). This measurement is performed in a constant-size mode (distance between chucks is 10 mm), and the test piece is allowed to stand in a room at 20 ° C for a sufficient time. Then, the temperature setting of the room is raised from 20 ° C to 105 ° C for 10 minutes And after the temperature was raised, the room temperature of the sample was set to be maintained at 105 ° C. After raising the temperature, the test piece was further left for 30 minutes, and then the shrinkage force in the long-side direction of the test piece was measured under an environment of 105 ° C. In this measurement, a static load was set to 0 mN, and a probe made of SUS was used for the jig.

[Production Example 1] A polarizing plate having a protective film

A polyvinyl alcohol film (average degree of polymerization of about 2,400, degree of saponification of 99.9 mol% or more) having a thickness of 20 占 퐉 was uniaxially stretched by about 5 times by dry stretching and immersed in pure water at 60 占 폚 for one 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. Thereafter, 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 a polyvinyl alcohol film.

Subsequently, 3 parts of a carboxyl group-modified polyvinyl alcohol (trade name "KL-318 ", available from Kabushiki Kaisha Kurara Co., Ltd.) was dissolved in 100 parts of water on one side of the polarizing film, An epoxy-based adhesive to which 1.5 parts of an amide epoxy additive (Sumirez Resin (registered trademark) 650 (30), an aqueous solution having a solid content concentration of 30%, obtained from Daoka Kagaku Kogyo K.K.) (Trade name: "ZF-14-013 ", manufactured by Nippon Zeon Co., Ltd.) having a thickness of 13 탆 was bonded as a protective film to obtain a polarizing plate having a protective film / polarizing film.

[Production Example 2]

The following stretched films were prepared by adjusting the stretching magnification. As a reference example, an unoriented film was also prepared.

Stretched film A: An unstretched triacetylcellulose (TAC) film was stretched to prepare a stretched TAC film having a thickness of 40 탆. The shrinking force of this film in the slow axis direction was 0.18 N / 2 mm.

Stretched film B: An unstretched TAC film was stretched to prepare a stretched TAC film having a thickness of 40 탆. The shrinkage force of this film in the slow axis direction was 0.02 N / 2 mm.

Stretched film C: An unstretched TAC film was stretched to prepare a stretched TAC film having a thickness of 40 탆. The shrinking force of the film in the slow axis direction was 0.30 N / 2 mm.

Stretched Film D: An unoriented cycloolefin resin (COP) film was stretched to produce a stretched COP film having a thickness of 25 탆. The shrinking force of the film in the slow axis direction was 0.002 N / 2 mm.

Unstretched film E: An unoriented TAC film having a thickness of 40 탆 was produced. The contraction force in any direction was 0.001 N / 2 mm.

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

[Example 1]

3 parts of a carboxyl group-modified polyvinyl alcohol (trade name "KL-318 ", available from Kabushiki Kaisha Kurara Co., Ltd.) was dissolved in 100 parts of water on a polarizing film of a polarizing plate having a protective film, An epoxy adhesive to which 1.5 parts of a polyamide epoxy additive (Sumirez Resin (registered trademark) 650 (30), an aqueous solution having a solid content concentration of 30%, obtained from Daoka Kagaku Kogyo Co., Ltd.) . The 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 x 40 mm and pressed against the alkali-free glass through an adhesive so that the protective film became a bonding surface with the alkali-free glass. The mixture was allowed to stand in an autoclave at 50 DEG C under a load of 5 kg for 20 minutes to mature the adhered state, and then left to stand for 10 hours under an environment of 23 DEG C / 60% RH.

Then, 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 (visual sensitivity correction polarization degree) was calculated in accordance with JIS-Z8729.

A heat resistance test was conducted in which the produced polarizing plate was allowed to stand in an environment of 105 캜 for 1 hour using a constant temperature and humidity machine manufactured by Espec Corporation. Within 30 minutes immediately after the polarizer was removed from the thermo-hygrostat, the degree of polarization was measured by the same method as the measurement of the initial polarization. The initial polarized light of this polarizing plate and the difference in polarization degree after the heat resistance test (change amount of polarization degree) were -0.028%.

Further, in order to evaluate the visibility in the state of wearing polarized sunglasses, the polarizing plate was bonded to the liquid crystal cell through the pressure-sensitive adhesive layer to obtain a liquid crystal display device. The obtained liquid crystal display was turned on, and the image was observed through polarized sunglasses. Observation was performed at a 360-degree angle with respect to the screen of the liquid crystal display device, and evaluation was made based on the following criteria.

<Visibility in polarized sunglasses>

A: Images can be viewed from any direction.

X: There is an angle at which the image can not be viewed.

&Lt; Coloring in the state of wearing polarized sunglasses >

&Amp; cir &amp;: Visible from any direction without changing color tone.

○: There is an angle at which the color tone changes, but it is acceptable.

[Examples 2 to 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 the stretched films B to D or the unstretched film E. Each of the prepared polarizing plates was measured for initial polarization degree and polarization degree after heat resistance test, and visibility and coloring evaluation in the state of wearing polarized sunglasses was performed. The results are shown in Table 1.

According to the present invention, there is provided a polarizing plate capable of suppressing a decrease in polarization degree caused by a change in the absorption axis of a polarizing film caused by a dimensional change of an optical film at the time of heat resistance test while making the visibility in a state of polarizing sunglasses good It is useful because it can do.

10: polarizing plate, 11: stretched film, 12: protective film, 13: first pressure-sensitive adhesive layer, 14: polarizing film, 15: protective film,

Claims (7)

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 stretched film is about 45 ° or about 135 °,
Wherein the stretched film has a shrinking force in the stretching direction of 0.2 N / 2 mm or less when heated at 105 캜 for 30 minutes. The polarizing plate according to claim 1, wherein the polarizing film and the stretched film are laminated through a pressure-sensitive adhesive layer, an aqueous adhesive layer or an active energy ray-curable adhesive layer. The stretched film according to claim 1 or 2, wherein the stretched film comprises 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. The polarizing plate according to claim 1 or 2, wherein the stretched film has a surface treatment layer on a surface opposite to the surface on the polarizing film side. The polarizing plate according to claim 1 or 2, 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)
_{(3) 0.85≤R e (450)} / R e (550) <1.00
(4) 1.00 < R _e (630) / R _e (550)
[Formula (1) to equation _{(4), R e (590} ), R e (450), R e (550), R e (630) are respectively the wavelength 590 nm, 450 nm, 550 nm , 630 nm in And R _th (590) represents the thickness direction retardation value at a wavelength of 590 nm. The polarizing plate according to claim 1 or 2, 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. The image display apparatus according to claim 1 or 2, wherein the polarizing plate is laminated on the image display element through the first pressure-sensitive adhesive layer.

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