TW201727287A - Polarizing plate and liquid crystal panel - Google Patents

Abstract

The present invention provides a polarizing plate which is possible to suppress a decrease in degree of polarization due to deviation of an absorption axis of a polarizing film caused by dimensional change of an optical film during a heat resistance test. The polarizing plate comprises an optical film, a first adhesive layer, a polarizing film and a second adhesive layer in this order, wherein an angle between the absorption axis of the polarizing film and the slow axis of the optical film is about 45 DEG or about 135 DEG; when the optical film placed in an environment of 85 DEG C for 100 hours, it has a dimensional change rate D1 in a direction of 45DEG with respect to the absorption axis of the polarizing film, and a dimensional change rate D2 in a direction of 135DEG with respect to the absorption axis of the polarizing film, and D1 and D2 satisfy the following formulas (1) and (2): In the case of | D1 | > | D2 |, 2 < | D1 | / | D2 |...(1) In the case of | D1 | < | D2 |, 2 < | D2 | / | D1 |...(2).

Description

Polarizer and LCD panel

The present invention relates to a polarizing plate and a liquid crystal panel using the same.

In recent years, liquid crystal displays that consume low power, operate at low voltage, and are lightweight and thin have been rapidly popularized as information display devices such as mobile phones, portable information terminals, computer screens, and televisions. Along with the development of liquid crystal technology, various forms of liquid crystal displays have been proposed, and the problems of liquid crystal displays such as reaction speed and contrast, and narrow viewing angle are being continuously solved. Further, with the spread of portable liquid crystal displays, for example, when used outdoors, there is a case where the liquid crystal display screen is viewed in a state in which polarized sunglasses are worn, and in this case, the liquid crystal display is also required. Even if you look at the picture through polarized sunglasses, it is still excellent.

In the past, several means for improving the visibility when viewing images through polarized sunglasses have been proposed (Patent Documents 1 to 9).

[Previous Technical Literature] [Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open Publication No. 2009-122454

[Patent Document 2] Japanese Patent Laid-Open Publication No. 2011-107198

[Patent Document 3] Japanese Laid-Open Patent Publication No. 2011-215646

[Patent Document 4] Japanese Laid-Open Patent Publication No. 2012-230390

[Patent Document 5] Japanese Patent Laid-Open Publication No. 03-174512

[Patent Document 6] Japanese Patent Laid-Open Publication No. 2013-231761

[Patent Document 7] Japanese Laid-Open Patent Publication No. 2011-113018

[Patent Document 8] Japanese Patent Laid-Open Publication No. 2013-182162

[Patent Document 9] Japanese Patent Laid-Open Publication No. 2013-200445

The method for improving the visibility when viewing a screen through polarized sunglasses is to convert linearly polarized light emitted from a polarizing plate disposed on the viewing side of an image display element such as a liquid crystal cell into A method of disposing a phase difference plate (for example, a λ/4 wavelength plate) on the viewing side of the polarizing plate by polarizing a circle (or a circle) (Patent Documents 1 to 9).

However, such a phase difference plate is often subjected to an extension treatment to laminate a layer on a polarizing film via a direct adhesive. Moreover, the angle formed by the absorption axis of the polarizing plate and the slow axis of the phase difference plate is often set to a predetermined angle (for example, 45°), and when the heat resistance test is applied, there is an oblique dimension due to the extended phase difference plate. The change causes the absorption axis of the polarizing film to locally change and the degree of polarization to be lowered.

[1] A polarizing plate comprising an optical film, a first adhesive layer, and a polarizing film and a second adhesive layer; wherein an angle formed by an absorption axis of the polarizing film and a slow axis of the optical film is about 45° or about 135°; and regarding the optical film, when it is at 85° C The dimensional change rate in the direction of 45° with respect to the absorption axis of the polarizing film after standing for 100 hours in the environment is set to D1, and is allowed to stand for 100 hours in an environment of 85° C. with respect to the polarizing film. When the dimensional change rate in the direction of the absorption axis of 135° is D2, the following equations (1) and (2) are satisfied: |D1 |>| D2 |, 2<| D1 |/| D2 | …(1)

| D1 |<| D2 |, 2<| D2 |/| D1 |...(2)

[2] The polarizing plate according to [1], wherein the optical film comprises a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth)acrylic resin. At least one of the selected groups.

[3] The polarizing plate according to [1], wherein the polarizing film has a thickness of 15 μm or less.

[4] The polarizing plate according to any one of [1] to [3], further comprising a protective film between the polarizing film and the second adhesive layer.

[5] A liquid crystal panel in which at least one surface of the liquid crystal cell is laminated, and the polarizing plate according to any one of [1] to [4] is laminated via the second adhesive layer.

According to the present invention, it is possible to provide a polarizing plate which can suppress a decrease in the degree of polarization caused by a shift in the absorption axis of the polarizing film due to a dimensional change of the optical film during the heat resistance test.

10‧‧‧Polar plate

11‧‧‧Optical film

12‧‧‧1st adhesive layer

14‧‧‧ polarizing film

15‧‧‧Protective film

16‧‧‧2nd adhesive layer

20‧‧‧Surface treatment layer

30‧‧‧Absorption axis of polarizing film

31‧‧‧direction 45° with respect to the absorption axis of the polarizing film

32‧‧‧direction 135° with respect to the absorption axis of the polarizing film

33‧‧‧45°

34‧‧‧135°

40‧‧‧ Cut optical film 11

Fig. 1 is a view showing an example of a schematic cross-sectional view of a layer configuration of a polarizing plate of the present invention.

Fig. 2 is a view showing an example of a plan view showing the relationship of the axial direction of the polarizing plate of the present invention.

The layer configuration of the polarizing plate 10 of the present invention will be described with reference to Fig. 1 . The polarizing plate of the present invention is preferably formed by sequentially laminating the optical film 11, the first adhesive layer 12, the polarizing film 14, and the second adhesive layer 16. The angle formed by the absorption axis of the polarizing film 14 and the slow axis of the optical film 11 is about 45 or about 135. It is also useful to form the surface treatment layer 20 on the surface of the optical film 11 opposite to the surface on which the polarizing film is bonded.

Further, the optical film 11 preferably contains at least one film 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 polarizing film 14 is preferably 15 μm or less in thickness.

Further, according to the present invention, the polarizing plate 10 having the protective film 15 between the polarizing film 14 and the second adhesive layer 16 can be provided.

Moreover, according to the present invention, there is provided a liquid crystal panel in which the polarizing plate 10 is laminated on at least one side of the liquid crystal cell via the second adhesive layer 16.

Hereinafter, the members constituting the liquid crystal display device of the present invention will be described in detail.

[Polarizing film 14]

The polarizing film 14 is usually produced by a step of stretching a polyvinyl alcohol-based resin film on one axis, a step of dyeing a polyvinyl alcohol-based resin film with a dichroic dye to adsorb a dichroic dye, and adsorbing The step of treating the polyvinyl alcohol-based resin film of the dichroic dye with a boric acid aqueous solution and crosslinking; and subjecting the mixture to a water-washing treatment after crosslinking treatment with an aqueous boric acid solution.

The polyvinyl alcohol-based resin can be produced by saponifying a polyvinyl acetate-based resin. The polyvinyl acetate-based resin may be a copolymer of vinyl acetate and another monomer copolymerizable with vinyl acetate, in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Other single systems which can be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, acrylamides having an ammonium group, and the like.

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

A film formed of such a polyvinyl alcohol-based resin can be used as an original film of a polarizing film. The method of forming the film of 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 μm, preferably about 10 to 50 μm.

The longitudinal axis extension of the polyvinyl alcohol-based resin film can be carried out before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When the longitudinal one-axis extension is performed after dyeing, the longitudinal one-axis extension can be performed before the boric acid treatment or in the boric acid treatment. Of course, longitudinal one-axis extension can also be performed at a plurality of stages as shown here. The one-axis extending in the longitudinal direction may be a method of extending on one axis between rolls having different rotational speeds, or a method of extending on one axis using a heat roll. Further, the longitudinal one-axis stretching may be carried out by dry stretching in which the film is stretched in the air, or may be carried out by wet stretching in which the polyvinyl alcohol-based resin film is swollen using a solvent such as water. The stretching ratio is usually about 3 to 8 times.

The dyeing by the dichroic dye of the polyvinyl alcohol-based resin film can be carried out, for example, by immersing the polyvinyl alcohol-based resin film in an aqueous solution containing a dichroic dye. Specifically, iodine and a dichroic organic dye can be used as the dichroic dye system. Moreover, it is preferable that the polyvinyl alcohol-based resin film is subjected to a treatment of immersing in water and swelling it before the dyeing treatment.

When iodine is used as the dichroic dye, a method in which a polyvinyl alcohol-based resin film is immersed in an aqueous solution containing iodine and potassium iodide and dyed is usually used.

The iodine content in the aqueous solution is usually about 0.01 to 1 part by weight based on 100 parts by weight of water, and the potassium iodide content is usually about 0.5 to 20 parts by weight based on 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is usually about 20 to 40 °C. Further, the immersion time (dyeing time) immersed in the aqueous solution is usually about 20 to 1,800 seconds.

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

The boric acid treatment after dyeing by the dichroic dye can be carried out by immersing the dyed polyvinyl alcohol-based resin film in an aqueous solution containing boric acid. The content of boric acid in the aqueous solution containing boric acid 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 preferred that the aqueous solution containing boric acid contains potassium iodide. The content of potassium iodide in the aqueous solution containing boric acid 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 time of immersion in the aqueous solution containing boric acid is usually from about 60 to 1,200 seconds, preferably from 150 to 600 seconds, and more preferably from 200 to 400 seconds. The temperature of the aqueous solution containing boric acid is usually 50 ° C or higher, preferably 50 to 85 ° C, and more preferably 60 to 80 ° C.

The polyvinyl alcohol-based resin film after the boric acid treatment is usually subjected to a water washing treatment. The water washing treatment can be carried out, for example, by immersing a boric acid-treated polyvinyl alcohol-based resin film in water. In the water washing treatment, the temperature of the water is usually about 5 to 40 °C. Moreover, the immersion time is usually from 1 to 120 About seconds.

After washing, drying treatment was carried out to obtain a polarizing film. The drying treatment can be carried out using a hot air dryer or a far infrared heater. The temperature of the drying treatment is usually from about 30 to 100 ° C, preferably from 50 to 80 ° C. The drying treatment 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 thereof is usually from about 5 to 20% by weight, preferably from 8 to 15% by weight. When the water content is less than 5% by weight, the flexibility of the polarizing film may be lost, and the film may be damaged or broken after drying. Further, when the water content exceeds 20% by weight, the thermal stability tends to be insufficient.

According to the above operation, the polarizing film 14 in which the dichroic dye is adsorbed to the polyvinyl alcohol-based resin film can be produced.

From the viewpoint of suppressing the decrease in the degree of polarization under the heat resistance test, it is also preferable to make the contraction force of the polarizing film itself low. In order to suppress the polarizing film 14 to a low contraction force, the thickness of the polarizing film 14 is preferably 12 μm or less. The thickness of the polarizing film is usually 3 μm or more from the viewpoint of imparting good optical characteristics.

[Optical film 11]

In the polarizing plate used in the present invention, the optical film 11 is preferably made of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and the like. For example, a polyolefin resin such as a chain polyolefin resin (such as a polypropylene resin) or a cyclic polyolefin resin (a norbornene resin); for example, cellulose triacetate, a cellulose resin such as a cellulose ester resin such as cellulose diacetate; a polyester resin; a polycarbonate resin; Acrylic resin; polystyrene resin; or a mixture, copolymer or the like.

The optical film 11 is preferably a film satisfying the following formula: (5) 100 nm ≦R _e (590) ≦ 180 nm, (6) 0.5 < R _th (590) / R _e (590) ≦ 0.8, (7) 0.85 ≦ R _e (450) / R _e (550) < 1.00, and (8) 1.00 < R _e (630) / R _e (550) ≦ 1.1. In the formula, R _e (590), R _e (450), R _e (550), and R _e (630) are respectively shown in the in-plane retardation values of the measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, and R _th (590). It is expressed as a thickness direction phase difference value at a measurement wavelength of 590 nm. These in-plane phase difference values and thickness direction phase difference values were measured in an environment of a temperature of 23 ° C and a relative humidity of 55%.

The in-plane retardation value R _e and the thickness direction retardation value R _{th of the} optical film 11 are set to be n _x in the in-plane slow axis direction and in-plane fast axis direction (perpendicular to the in-plane slow axis direction). When the refractive index of the direction is n _y , the refractive index in the thickness direction is n _z , and the thickness of the optical film 11 is d, it is defined by the following formula: R _e = (n _{x -} n _y ) × d

R _th =[{(n _x +n _y )/2}-n _z ]×d.

A liquid crystal display in which the optical film 11 having the phase difference characteristics and the wavelength dispersion characteristics of the above formulas (5) to (8) is disposed on the viewing side is effective in suppressing transmission of polarized sunglasses from various directions (azimuth and pole) Angle) The hue change when viewing the screen, and the visibility of the liquid crystal display can be improved. On the other hand, when any one of the above formulas (5) to (8) is not satisfied, The suppression of the hue change will be insufficient.

From the viewpoint of more effectively suppressing the hue change, R _e (590) in the formula (5) is preferably from 105 to 170 nm, and R _th (590) / R _e (590) in the formula (6) is preferably. R from 0.6 to 0.75, R _e (450) / R _e (550) in the formula (7) is preferably from 0.86 to 0.98, and R _e (630) / R _e (550) in the formula (8) is preferably 1.01. To 1.06.

The optical film 11 is a retardation film having a function of converting linearly polarized light emitted from the polarizing film 14 to the optical film 11 into a circularly polarized light (including a case where it is circularly polarized) and emitting the same, in order to make the function appear. The layer formed by the angle formed by the absorption axis of the polarizing film and the slow axis of the optical film is about 45 or about 135. When the angle formed is outside the range, the function of converting the linearly polarized light into the circularly polarized light and emitting it is not obtained, and as a result, the suppression of the above-described hue change becomes 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°, and more preferably 40 to 40. 50° or 130 to 140°.

Since the phase difference characteristics and the wavelength dispersion characteristics of the above formulas (5) to (8) are easily imparted, and the moisture permeability and the moist heat resistance of the optical laminate are improved due to the low moisture permeability, the extended optical film is It is preferable to contain a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, or a (meth)acrylic resin, or two or more of them, and the resin component contains the above. It is better to select one or more.

The chain polyolefin resin may be a homopolymer of a chain olefin such as a polyethylene resin or a polypropylene resin. A copolymer containing two or more kinds of chain olefins is listed.

The cyclic polyolefin resin is a general term for a resin obtained by polymerizing a cyclic olefin as a polymerization unit. Specific examples of the cyclic polyolefin-based resin include a ring-opening (co)polymer of a cyclic olefin, an addition polymer of a cyclic olefin, and a chain olefin such as a chain olefin such as ethylene or propylene. a copolymer (representatively a random copolymer); and a graft polymer modified with an unsaturated carboxylic acid or a derivative thereof; and such a hydride or the like. Among them, it is particularly preferable to use a norbornene-based resin which uses a norbornene-based monomer such as norbornene or a polycyclic norbornene-based monomer as a cyclic olefin.

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. Further, it is also possible to use such a copolymer or a part of a hydroxyl group which is modified by another substituent. Among these, cellulose triacetate (i.e., cellulose triacetate: TAC) is particularly preferred.

The polyester resin is a resin having an ester bond, and generally includes 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 naphthalene dicarboxylic acid. Ester and the like. As the polyol, a divalent diol can be used, and examples thereof include ethylene glycol, propylene glycol, butanediol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of the polyester resin include polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polybutylene terephthalate. Ester, propylene naphthalate, Polyethylene terephthalate dimethyl ester, polynaphthalene dicarboxylate dimethyl dimethyl ester.

The polycarbonate resin contains a polymer in which a monomer unit is bonded via a carbonate group. The polycarbonate resin may be a resin called a modified polycarbonate such as a modified polymer skeleton, or a copolymerized polycarbonate.

The (meth)acrylic resin is a resin having a compound having a (meth)acryl fluorenyl group as a main constituent monomer. Specific examples of the (meth)acrylic resin include, for example, poly(meth)acrylate such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymer; methyl methacrylate-( Methyl) acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth) acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate and A copolymer of a compound of an alicyclic hydrocarbon group (for example, methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-methyl (meth) acrylate), and the like. It is preferable to use a polymer containing a poly(meth)acrylic acid C _1-6 alkyl ester such as poly(methyl) acrylate as a main component, and it is more preferable to use methyl methacrylate as a main component (50). To 100% by weight, preferably 70 to 100% by weight, of a methyl methacrylate-based resin.

The optical film 11 can be produced by stretching a film containing the above thermoplastic resin. The stretching treatment may be exemplified by one-axis extension and two-axis extension. The direction of extension may be, for example, the mechanical flow direction (MD) of the unstretched film, the direction perpendicular thereto (TD), and the direction in which the mechanical flow direction (MD) intersects obliquely. The two-axis extension may be a simultaneous two-axis extension extending toward two extending directions, or may extend in a predetermined direction and then extend in other directions. Successive two-axis extension. The stretching treatment can be performed, for example, by using two or more pairs of nip rolls that increase the number of revolutions on the outlet side and extending in the long direction (mechanical flow direction: MD), or not extending Both ends of the film are clamped by a chuck and extended in a direction (TD) perpendicular to the direction of mechanical flow. At this time, the phase difference value can be adjusted within the range of the above formulas (5) to (6) by adjusting the thickness of the film or adjusting the stretching ratio. Further, by adding a wavelength dispersion adjusting agent to the resin, the wavelength dispersion value can be adjusted within the range of the above formulas (7) to (8).

The thickness of the optical film 11 is not particularly limited as long as it satisfies the above formulas (5) to (8), but is preferably 90 μm or less, more preferably 60 μm or less from the viewpoint of thinning of the polarizing plate, and is processed from From the viewpoint, it is preferably 5 μm or more, and more preferably 10 μm or more.

The optical film 11 may contain one or more additives such as a smoothing agent, a plasticizer, a dispersing agent, a heat stabilizer, an ultraviolet absorber, an infrared absorber, an antistatic agent, and an antioxidant.

Moreover, in order to impart desired surface optical characteristics or other characteristics, a coating layer (surface treatment layer 20) may be provided on the outer surface of the optical film 11. 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 of forming the coating layer is not particularly limited, and a known method can be used.

In order to impart the desired phase difference characteristics, the optical film 11 of the present invention uses a dimensional change ratio D1 at a direction of 45° with respect to the absorption axis of the polarizing film after standing for 100 hours in an environment of 85 ° C. The dimensional change rate D2 in the direction of 135° with the absorption axis of the polarizing film is satisfied The person who speaks. Moreover, when the polarizing film 14 is seen from the extended optical film 11, the angle which rotates counterclockwise is positive.

| D1 |>| D2 |, 2<| D1 |/| D2 | (1)

| D1 |<| D2 |, 2<| D2 |/| D1 | (2)

D1 and D2 in the above formulas (1) to (2) can be measured in the following manner with reference to Fig. 2 . Fig. 2(a) is a plan view showing an absorption axis of the polarizing film, a direction of 45° with respect to the absorption axis, and a direction of 135° with respect to the absorption axis in the polarizing plate of the present invention. . As previously mentioned, the slow axis of the optical film is preferably substantially coincident with direction 31 or direction 32.

First, as shown in Fig. 2(b), the optical film was cut so as to have a size of 45 mm in the direction of 45° with respect to the absorption axis of the polarizing film and 100 mm in the direction of 135°. The cut optical film 40 was allowed to stand in an environment of a temperature of 23 ° C and a humidity of 55% for one day, and the dimension (L0 (45)) in the direction (direction 31) of 45° with respect to the absorption axis of the polarizing film was measured, And a dimension (L0 (135)) in a direction (direction 32) of 135° with respect to the absorption axis of the polarizing film. Next, the size (L1 (45)) of the direction 31 and the size (L1 (135)) of the direction 32 after standing for 100 hours in an environment of 85 ° C were measured. Based on the results, the dimensional change rates D1 (%) and D2 (%) can be obtained from the equations (3) and (4).

Dimensional change rate D1=[(L0(45)-L1(45))/L0(45)]×100 (3)

Dimensional change rate D2=[(L0(135)-L1(135))/L0(135)]×100 (4)

The optical film 11 satisfying the above formulas (1) to (2) can be produced, for example, by biaxially stretching a film containing the above thermoplastic resin. From the viewpoint of easily obtaining a film satisfying the above formulas (1) to (2), among the above thermoplastic resins, a cellulose ester resin such as cellulose triacetate or cellulose diacetate is particularly contained. A cellulose resin is preferred.

The stretching method may be a simultaneous biaxial stretching or a sequential biaxial stretching, and it is preferable that a film which satisfies the above formulas (1) to (2) can be easily obtained by a simultaneous biaxial stretching. At the same time, the method of biaxial stretching is not particularly limited, and both ends of the unstretched film may be clamped by the jig, so that the conveying speeds of the jigs at the two ends are different, and further in a direction perpendicular to the mechanical flow direction (TD). Made by extension. Further, in the simultaneous biaxial stretching, the case where the tension is extended in one direction and the tension of the other is relaxed and contracted.

In general, a long polarizing film has an absorption axis in the longitudinal direction, so that a roll-to-roll method can be used to attach a long optical film to a long polarizing film. In general, it is preferred that the optical film be produced by obliquely extending by biaxial stretching.

[Protective film 15]

The protective film 15 is preferably made of a material excellent in transparency, mechanical strength, thermal stability, moisture shielding property, and the like. The protective film 15 is preferably a cellulose resin, a polyolefin resin, or an acrylic resin because it is easy to adjust the phase difference and is easy to obtain. Here, the polyolefin resin includes a chain polyolefin resin and a cyclic polyolefin resin.

The cellulose resin, the polyolefin resin, or the acrylic resin can be the same as those exemplified for the optical film 11 .

The method of forming a film by the above resin, as long as The resin may be appropriately selected, and for example, a solvent casting method, a melt extrusion method, or the like can be employed. Among them, the polyolefin resin and the acrylic resin are preferably melt-extruded from the viewpoint of productivity. On the other hand, in general, a cellulose resin is formed by a solvent casting method.

When the liquid crystal cell is in the IPS (In-Plane Switching) mode, the phase difference R _{th of the} protective film in the thickness direction is -10 in order not to impair the wide viewing angle characteristic originally possessed by the IPS mode liquid crystal cell. A range of up to 10 nm is preferred.

The method of adjusting the phase difference R _th in the thickness direction of the protective film in the range of -10 to 10 nm is a method of reducing the distortion remaining in the in-plane and thickness directions as much as possible in the production of the film. In the solvent casting method, for example, a method in which residual shrinkage distortion in the in-plane and thickness directions generated when the cast resin solution is dried is moderated by heat treatment can be employed. On the other hand, in the above melt extrusion method, in order to prevent the resin film from being stretched between extrusion and cooling from the die, it is possible to minimize the distance from the die to the cooling cylinder and to prevent the film from being stretched. A method of controlling the amount of extrusion and the rotation speed of the cooling cylinder, and the like. Further, similarly to the solvent casting method, a method of alleviating the distortion remaining in the obtained film by heat treatment may be employed.

The thickness of the protective film is preferably 90 μm or less, more preferably 60 μm or less from the viewpoint of film formation of the polarizing plate, and is preferably 5 μm or more, and more preferably 10 μm or more from the viewpoint of handling.

[adhesive layer]

The polarizing film and the protective film can be bonded by an adhesive or an adhesive.

The adhesive layer to which the polarizing film and the protective film are bonded may have a thickness of about 0.01 to 30 μm, preferably 0.01 to 10 μm, and more preferably 0.05 to 5 μm. When the thickness of the subsequent layer is in this range, floating and peeling do not occur between the protective film and the polarizing film, and an adhesive force which is practically free from problems can be obtained. The adhesive layer to which the polarizing film and the protective film are bonded may have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.

When the polarizing film and the protective film are to be bonded together, it is also useful if the polarizing film or the protective film is previously subjected to saponification treatment, corona treatment, plasma treatment, or the like.

In the formation of the subsequent layer, an appropriate adhesive can be suitably used depending on the type and purpose of the object to be used, and an anchor coating agent can also be used as needed. Examples of the subsequent agent include a solvent-based adhesive, an emulsion-type adhesive, a pressure-sensitive adhesive, a rewet adhesive, a polycondensation adhesive, a solventless adhesive, a film adhesive, and a hot melt. Type of adhesive, etc.

One of the preferred adhesives is a water-based adhesive, and even if the adhesive component is dissolved or dispersed in water. An example of a component which can be dissolved in water is a polyvinyl alcohol-based resin. Further, examples of the component which can be dispersed in water are urethane-based resins having a hydrophilic group. The aqueous binder can be prepared by mixing such an adhesive component with water as needed, in addition to an additional additive. In the case of a commercially available polyvinyl alcohol-based resin which can be used as a water-based adhesive, there is a "KL-318" which is a carboxyl group-modified polyvinyl alcohol sold by Kuraray Co., Ltd., and the like.

The aqueous binder may contain a crosslinking agent as desired. Examples of the crosslinking agent include an amine compound, an aldehyde compound, a methylol compound, a water-soluble epoxy resin, an isocyanate compound, a polyvalent metal salt, and the like. When a polyvinyl alcohol-based resin is used as the 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 the crosslinking agent.

Here, the water-soluble epoxy resin may be, for example, a polydecylamine epoxy resin obtained by reacting a polyamine polyamine with epichlorohydrin, such as a diamethylenetriamine, a triple extension. A reaction product of a polyalkylene polyamine such as ethylene tetraamine and a dicarboxylic acid such as adipic acid. An example of a commercially available product of a water-soluble epoxy resin is "Sumirez Resin (registered trademark) 650 (30)" sold by Tiangang Chemical Industry Co., Ltd., and the like.

A water-based adhesive is applied to the surface of the polarizing film and/or the protective film bonded to the polarizing film, and the two are bonded together, followed by drying treatment, whereby a polarizing plate can be obtained. Before the next step, it is also effective to improve the wettability by performing the subsequent treatment such as saponification treatment, corona discharge treatment, plasma treatment, or primer treatment on the protective film. The drying temperature may be, for example, about 50 to 100 °C. From the viewpoint of further improving the adhesion, it is preferred to be cooked at a temperature slightly higher than room temperature (for example, a temperature of about 30 to 50 ° C) for about 1 to 10 days after the drying treatment.

Another preferred adhesive agent is a curable adhesive composition containing an epoxy compound which is cured by irradiation with an active energy ray or heating. Here, the curable epoxy compound is one having at least two epoxy groups in the molecule. At this time, the polarizing film and the protective film can be subsequently The method of irradiating an active energy ray or applying heat to the coating layer of the adhesive composition to cure the curable epoxy compound contained in the adhesive agent is carried out. The hardening of the epoxy compound is generally carried out by cationic polymerization of an epoxy compound. From the viewpoint of productivity, the curing is preferably carried out by irradiation with active energy rays.

The epoxy compound contained in the curable adhesive composition preferably has no aromatic ring in the molecule from the viewpoints of weather resistance, refractive index, cationic polymerizability and the like. The epoxy compound containing no aromatic ring in the molecule may, for example, be a hydrogenated epoxy compound, an alicyclic epoxy compound or an aliphatic epoxy compound. The epoxy compound which can be suitably used for the composition of the curable adhesive is described in detail in, for example, Japanese Laid-Open Patent Publication No. 2004-245925, which is also hereby expressly described.

The hydrogenated epoxy compound may be obtained by glycidyl etherification of a nuclear hydrogenated polyhydroxy compound by using an aromatic polyhydroxy compound belonging to a raw material of an aromatic epoxy compound in the presence of a catalyst. It is obtained by selectively performing a nuclear hydrogenation reaction under pressure. Examples of the aromatic polyhydroxy compound which is a raw material of the aromatic epoxy compound include bisphenols such as bisphenol A, bisphenol F and bisphenol S; for example, phenol novolale resin (phcnol novolae) resin, cresol novolak resin And a novolac type resin such as a hydroxybenzaldehyde phenol novolak resin; a polyfunctional compound such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone or polyvinylphenol. The aromatic polyhydroxy compound is subjected to a nuclear hydrogenation reaction, and the obtained nuclear hydrogenated polyhydroxy compound is reacted with epichlorohydrin to carry out glycidyl etherification. Suitable hydrogenated epoxy compounds are exemplified by hydrogenated bisphenols. A glycidyl ether of 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 the bridged oxygen atom -O- in the structure represented by the following formula, wherein m is an integer of 2 to 5.

A compound obtained by combining a group in which one or a plurality of hydrogen atoms in the formula (CH ₂ ) _m is removed from another chemical structure may be an alicyclic epoxy compound. Further, one or a plurality of hydrogen atoms in the (CH ₂ ) _m forming the alicyclic ring may be suitably substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, an epoxy compound having an oxabicyclohexane ring (m=3 in the above formula) and an oxabicycloheptane ring (m=4 in the above formula) is excellent in performance. The adhesion is preferred. Specific examples of the alicyclic epoxy compound are disclosed below. Here, the compound names are listed first, and the corresponding chemical formulas are respectively indicated, and the same symbols are used for the compound name and the chemical formula corresponding to the chemical name.

A: 3,4-epoxycyclohexylmethyl 3,4-epoxycyclohexanecarboxylic acid, B: 3,4-epoxy-6-methylcyclohexanecarboxylic acid 3,4-epoxy -6-methylcyclohexylmethyl ester, C: exoethyl bis(3,4-epoxycyclohexanecarboxylate), D: adipic acid bis(3,4-epoxycyclohexylmethyl) )ester, 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-tetraoxaspiro[5.2. 2.5.2.2] Behenane, 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: dicyclopentane dioxide Diene, etc.

The aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyol or an alkylene oxide adduct thereof. More specifically, it can be listed For example: diglycidyl ether of propylene glycol; diglycidyl ether of 1,4-butanediol; diglycidyl ether of 1,6-hexanediol; triglycidyl ether of glycerol; trimethylolpropane a glycidyl ether; a polyglycidol of a polyether polyol obtained by adding an alkylene oxide (for example, ethylene oxide or propylene oxide) to an aliphatic polyol such as ethylene glycol, propylene glycol or glycerin An ether (for example, a diglycidyl ether of polyethylene glycol) or the like.

In the composition of the curable adhesive, the epoxy compound may be used alone or in combination of two or more. Among them, 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 which can be used in the composition of the curable adhesive usually has an epoxy equivalent in the range of 30 to 3,000 g/eq, and the epoxy equivalent is preferably in the range of 50 to 1,500 g/eq. When an epoxy compound having an epoxy equivalent of less than 30 g/equivalent is used, the flexibility of the polarized plate after hardening may be lowered, and then the strength may be lowered. On the other hand, in order to use a compound having an epoxy equivalent of more than 3,000 g/eq, the compatibility with other components contained in the adhesive composition may be lowered.

From the viewpoint of reactivity, it is preferred to use cationic polymerization as a hardening reaction of an epoxy compound. Therefore, in the curable adhesive composition containing an epoxy compound, a cationic polymerization initiator is preferably used. The cationic polymerization initiator starts a polymerization reaction by irradiating an active energy ray such as visible light, ultraviolet rays, X-rays, and electron rays or heating to generate a cationic species or a Lewis acid. From the viewpoint of workability, the cationic polymerization initiator is preferably imparted with latent properties. Hereinafter, a cationic polymerization initiator which generates a cationic species or a Lewis acid by irradiation with an active energy ray and causes the epoxy group to start a polymerization reaction is referred to as a "photocationic polymerization initiator", and further, by heat A cationic polymerization initiator which produces a cationic species or a Lewis acid and initiates polymerization of the epoxy group is referred to as a "thermal cationic polymerization initiator".

By using a photocationic polymerization initiator and irradiating an active energy ray to perform hardening of the adhesive composition, the curing can be performed under normal temperature and normal humidity, and the heat resistance or expansion of the polarizing film can be less considered. It is advantageous because the skew is caused and the protective film and the polarizing film are well adhered. Further, since the photocationic polymerization initiator exhibits a catalytic action by light, it is excellent in storage stability and workability even when it is mixed with an epoxy compound.

The photocationic polymerization initiator may, for example, be an aromatic diazonium salt; an onium salt such as an aromatic onium salt or an aromatic onium salt; an iron-propene complex (allene) complex. The compounding amount of the photocationic polymerization initiator is usually 0.5 to 20 parts by weight, preferably 1 part by weight or more, and preferably 15 parts by weight or less based on 100 parts by weight of the epoxy compound.

When the amount of the photocationic polymerization initiator is less than 0.5 part by weight based on 100 parts by weight of the epoxy compound, the hardening may be insufficient, and the mechanical strength and the subsequent strength of the cured product tend to be lowered.

On the other hand, when the 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, and the hygroscopicity of the cured product becomes high. May reduce durability.

When a photocationic polymerization initiator is used, the curable adhesive composition may further contain a photosensitizer as needed. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and the subsequent strength of the cured product can be improved. Examples of the photosensitizer include a carbonyl compound, an organic sulfide, a persulfide compound, a redox compound, an azo compound, a diazo compound, a halogen compound, and a photoreductive dye. When the photosensitizer is formulated, the amount thereof is preferably in the range of 0.1 to 20 parts by weight based on 100 parts by weight of the curable adhesive composition. Further, in order to increase the curing speed, a sensitizer such as a naphthoquinone derivative may also be used.

On the other hand, the thermal cationic polymerization initiator may, for example, be a benzyl sulfonium salt, a thiophenium salt, a thiolanium salt, a benzylammonium salt, a pyridinium salt or a hydrazine salt hydrazinium. Salt), carboxylic acid ester, sulfonate, amino ruthenium, and the like.

The curable adhesive composition containing an epoxy compound is preferably cured by photocationic polymerization as described above, but the above thermal cationic polymerization initiator may be present and hardened by thermal cationic polymerization, or may be used in combination. Photocationic polymerization and thermal cationic polymerization. In the case of photocationic polymerization and thermal cationic polymerization, it is preferred to contain both a photocationic polymerization initiator and a thermal cationic polymerization initiator in the curable adhesive composition.

Further, the curable adhesive composition may further contain a compound which promotes cationic polymerization such as an oxetane compound and a polyol compound. The oxetane compound is a compound having a 4-membered cyclic ether in the molecule. When the oxetane compound is blended, the amount thereof is usually from 5 to 95% by weight, preferably from 5 to 50% by weight, based on the composition of the curable adhesive. Further, the polyol compound may be an alkylene glycol or an oligomer thereof including ethylene glycol or hexamethylene glycol, polyethylene glycol or the like, a polyester polyol, a polycaprolactone polyol, and a polycarbonate polyol. Alcohol, etc. When the polyol compound is blended, the amount is usually 50% by weight or less, preferably 30% by weight or less, based on the curable adhesive composition.

In addition, the curable adhesive composition may contain other additives without damaging its adhesion, for example, may contain an ion trapping agent, an antioxidant, a chain transfer agent, a sensitizer, a tackifier, a thermoplastic resin. , fillers, flow regulators, plasticizers, defoamers, etc. The ion trapping agent may, for example, be an inorganic compound containing a powdery lanthanoid, lanthanoid, magnesium, aluminum, calcium, titanium, or the like, and examples of the antioxidant include hindered phenol antioxidants. Wait.

After applying the curable adhesive composition containing the epoxy compound to the adhesion surface of the polarizing film or the protective film, or the adhesion surface of the both, bonding with the surface coated with the adhesive, and irradiating the active energy ray The uncured adhesive layer is hardened by heating, whereby the polarizing film and the protective film can be bonded. The coating method of the subsequent agent can employ various coating methods such as a doctor blade, a wire bar, a die coater, a comma coater, a gravure coater, and the like.

The curable adhesive composition can be basically used as a solventless adhesive which does not substantially contain a solvent, but various coating methods have respective optimum viscosity ranges, so that a solvent can be contained for adjusting the viscosity. . The solvent is preferably an organic solvent which does not lower the optical properties of the polarizing film and can dissolve various components including an epoxy compound well, for example, A hydrocarbon represented by toluene, an ester represented by ethyl acetate, or the like.

When the adhesive composition is cured by irradiation with an active energy ray, the above-described various types of active energy ray can be used. However, from the viewpoint of easy handling and easy adjustment of the amount of irradiation light, ultraviolet rays are preferably used. The irradiation intensity and the irradiation amount of the active energy ray (for example, ultraviolet ray) are not affected by various optical properties such as the degree of polarization of the polarizing film and various optical properties including the transparency and phase difference characteristics of the protective film. It is appropriately determined in such a manner as to maintain proper productivity.

When the curing of the adhesive composition is carried out by heat, it can be heated according to a generally known method. The thermal cationic polymerization initiator which is formulated in the curable adhesive composition is usually heated at a temperature above the temperature at which the cationic species and the Lewis acid are generated, and the specific heating temperature is, for example, about 50 to 200 °C.

[Lamination of polarizing film 14 and optical film 11]

It is preferable that the polarizing film 14 and the optical film 11 are directly laminated via the first adhesive layer 12. The polarizing film 14 and the optical film 11 are laminated via the adhesive layer, whereby the stress on the polarizing film due to the anisotropic dimensional change of the optical film 11 during the heat resistance test can be alleviated.

[1st adhesive layer 12]

The first adhesive layer 12 used for the layering of the polarizing film 14 and the optical film 11 is preferably excellent in optical transparency, suitable in wettability, and excellent in adhesion properties including aggregability and adhesion. Further superior in durability and the like. Specifically, the adhesive of the first adhesive layer 12 is formed, An adhesive (acrylic adhesive) containing an acrylic resin is preferred.

The acrylic resin contained in the acrylic pressure-sensitive adhesive is a resin mainly composed of an alkyl acrylate such as butyl acrylate, ethyl acrylate, isooctyl acrylate or 2-ethylhexyl acrylate. A polar monomer is usually copolymerized in the acrylic resin. A polar single system having a polymerizable unsaturated bond and a polar functional group, wherein the polymerizable unsaturated bond is generally derived from a (meth) acrylonitrile group, and the polar functional group may be a carboxyl group, a hydroxyl group or a guanamine group. , amine group, epoxy group, and the like. Specific examples of the polar monomer include (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, (A) Base) 2-N,N-dimethylaminoethyl acrylate, glycidyl (meth)acrylate, and the like.

Further, in the acrylic pressure-sensitive adhesive, a crosslinking agent is usually blended together with an acrylic resin.

Representative examples of the crosslinking agent include an isocyanate compound having at least two isocyanate groups (-NCO) in the molecule.

Various additives can be further formulated in the adhesive. Suitable additives include a decane coupling agent, an antistatic agent, and the like. The decane coupling agent is effective for increasing the adhesion to the glass. Antistatic agents are effective in reducing or preventing the generation of static electricity.

The first adhesive layer 12 can be formed by dissolving an adhesive composition in which an adhesive component is dissolved in an organic solvent, and applying the adhesive composition directly to any subsequent bonding surface. (a polarizing film or an optical film), and drying the solvent to remove the solvent; or coating the above-mentioned adhesive on the release-treated surface of the substrate film containing the resin film subjected to the release treatment The composition of the agent is obtained by drying and removing the solvent to form an adhesive layer, and attaching the adhesive layer to any of the bonding surfaces (polarizing film or optical film) and transferring the adhesive. When the first adhesive layer 12 is formed by the direct coating method of the former, a resin film (also referred to as a separator) subjected to release treatment is conventionally attached to the surface thereof to temporarily protect the adhesive. The surface of the layer is not used until use. From the viewpoint of the handleability of the adhesive composition of the organic solvent solution, the latter transfer method is often employed, and in this case, the release-treated substrate used in the formation of the first first adhesive layer is used. It is also suitable for the film to be directly attached to the polarizing plate as a separator.

In the heat resistance test, in order to ensure sufficient adhesion and dimensional stability during the heat resistance test and to suppress the decrease in the degree of polarization, the storage elastic modulus of the adhesive at 80 ° C is preferably 5 MPa or less, and more preferably 1 MPa or less. good.

It is also useful to perform corona treatment, plasma treatment, and the like on the surface of the polarizing film to be bonded, the surface of the stretched optical film, and the surface of the adhesive before the lamination by the adhesive and the adhesive.

[2nd adhesive layer 16]

The adhesive layer 16 can be used as an adhesive layer for bonding the polarizing plate 10 to the liquid crystal cell.

The second adhesive layer 16 formed on the surface of the protective film 15 opposite to the bonding surface of the polarizing film 14 is excellent in optical transparency, suitable in wettability, and includes adhesion such as cohesiveness and adhesion. The characteristics are excellent, and it is preferable to use it even more excellent in durability. Specifically, the adhesive for forming the second adhesive layer 16 is preferably an acrylic resin. Adhesive (acrylic adhesive). Specifically, the same as the first adhesive 12 described above can be used.

The second adhesive layer 16 may contain various additives similarly to the first adhesive layer 12. Preferably, the second adhesive layer 16 contains an antistatic agent. In general, when the polarizing plate is attached to the liquid crystal cell via the adhesive layer, the surface protective film (separator) which has been temporarily protected by the adhesive layer is peeled off, and then bonded to the liquid crystal cell, but When the surface protective film is peeled off, static electricity is generated to cause alignment failure of the liquid crystal in the liquid crystal cell, which may cause a display failure of the liquid crystal display device. For the means for reducing or preventing the generation of such static electricity, it is effective to formulate an antistatic agent in the adhesive.

When the protective film 15 and the second adhesive layer 16 are bonded together, it is also useful to perform corona treatment, plasma treatment, or the like on the surface where the protective film 15 and the second adhesive layer 16 are bonded to each other.

[Method of Manufacturing Polarizing Plate]

The method for producing the polarizing plate of the present invention is not particularly limited. For example, a polarizing plate formed by the polarizing film 14 and the protective film 15 and an adhesive layer formed by laminating the optical film 11 and the first adhesive layer 12 can be attached. The optical film of the agent is bonded to the first adhesive layer 12 by a roll-to-roll method to obtain a polarizing plate 10. Further, by forming the second adhesive layer 16 on the protective film 15, a polarizing plate with an adhesive is obtained. The polarizing plate with an adhesive can be bonded to the liquid crystal cell via the second adhesive layer 16.

[Liquid Crystal Unit]

The liquid crystal cell has two unit substrates and is sandwiched between the two substrates The liquid crystal layer between. The unit substrate is generally made of glass, but may be a plastic substrate. Further, the liquid crystal cell itself used in the liquid crystal panel of the present invention can be composed of various substances used in the field.

[LCD panel]

The liquid crystal panel can be produced by bonding the polarizing plate 10 to the liquid crystal cell via the second adhesive layer 16. Generally, the polarizing plate is bonded to both sides of the liquid crystal cell, but the polarizing plate of the present invention can be suitably used for the viewing side of the liquid crystal display device.

(Example)

The following series are shown to further illustrate the invention, but the invention is not limited by the examples. In the examples, the parts and % of the content or the amount used are indicated on a weight basis unless otherwise specified. Further, the measurement of each physical property in the following examples was carried out by the following method.

(1) Determination of thickness:

It was measured using a digital micrometer "MH-15M" manufactured by Nikon Co., Ltd.

(2) Determination of the in-plane phase difference and the phase difference in the thickness direction:

The phase difference meter "KOBRA (registered trademark) - WPR" manufactured by Oji Scientific Instruments Co., Ltd. is a parallel polarizer rotation method, and the in-plane phase at a predetermined wavelength is measured at a temperature of 23 ° C. The difference in phase between the difference and the thickness direction.

(3) Determination of the degree of polarization and the transmittance of the monomer of the polarizing plate:

Using a spectrophotometer with an integrating sphere [Japan Branch Co., Ltd. "V7100", 2 degree field of view; C light source] measurement.

(4) Method for measuring dimensional change rate of film

The dimensional change rate D1 of the film in the direction of 45° with respect to the absorption axis of the polarizing film after leaving the film in an environment of 85° C. for 100 hours and the dimensional change rate in the direction of 135° with respect to the absorption axis of the polarizing film D2 was measured in the following manner using a two-dimensional measuring device "NEXIV VMR-12072" manufactured by Nikon Co., Ltd. First, the optical film was cut so as to be 100 mm in a direction of 45° with respect to the absorption axis of the polarizing film, and 100 mm in a direction of 135°. The cut optical film was allowed to stand in an environment of a temperature of 23 ° C and a humidity of 55% for one day, and the dimension (L0 (45)) in the direction of 45° with respect to the absorption axis of the polarizing film and the polarizing film were measured. Absorbs the axis and has a dimension of 135° (L0 (135)). Next, after standing at 85 ° C for 100 hours, the size (L1 (45)) in the direction of 45° with respect to the absorption axis of the polarizing film after standing in a high-temperature environment and relative to the polarizing film were measured. Absorbs the axis and has a dimension of 135° (L1 (135)). Based on the results, the dimensional change rates D1 (%) and D2 (%) were obtained from the equations (3) and (4).

Dimensional change rate D1=[(L0(45)-L1(45))/L0(45)]×100 (3)

Dimensional change rate D2=[(L0(135)-L1(135))/L0(135)]×100 (4)

(Method for measuring storage elastic modulus)

The storage elastic modulus (G') of the adhesive is a cylindrical test piece of 8 mm in diameter × 1 mm in thickness made of an adhesive to be measured, and a dynamic viscoelasticity measuring device (Dynamic Analyzer RDA II: REOMETRIC Co., Ltd.) is used. The system was set to 1 N at a temperature of 80 ° C according to the torsion shear method at a frequency of 1 Hz.

[Manufacturing Example 1] Production of Polarizing Film

A polyvinyl alcohol film having a thickness of 20 μm (average degree of polymerization of about 2400, degree of saponification of 99.9 mol% or more) was stretched by a dry stretching to about 4 times, and then kept at a tight state, at 40 ° C of pure water. The mixture was immersed for 40 seconds, and immersed in an aqueous solution of iodine/potassium iodide/water in a weight ratio of 0.052/5.7/100 at 28 ° C for 30 seconds to carry out a dyeing treatment. Thereafter, it was immersed in an aqueous solution of potassium iodide/boric acid/water in a weight ratio of 11.0/6.2/100 at 70 ° C for 120 seconds. Then, after washing with pure water at 8 ° C for 15 seconds, it was dried at 60 ° C for 50 seconds while maintaining a tension of 300 N, and then dried at 75 ° C for 20 seconds to obtain a thickness of 7 μm of iodine adsorbed on the polyvinyl alcohol film. Polarized film.

[Production Example 2] Production of a water-based adhesive

3 parts by weight of a carboxyl group-modified polyvinyl alcohol (trade name "KL-318" obtained by Kuraray Co., Ltd.) was dissolved in 100 parts by weight of water, and a polyhydrazine which is a water-soluble epoxy resin was added to the aqueous solution. An amine epoxy-based additive (supply name: "Sumirez Resin (registered trademark) 650 (30)" obtained from the company, and 1.5 parts by weight of an aqueous solution having a solid content of 30% by weight) was prepared to prepare a water-based adhesive.

[adhesive]

Prepare the following Adhesives A to E.

Adhesive A: a sheet-like adhesive having a thickness of 25 μm ["P-3132" manufactured by Lintec Co., Ltd.]

Adhesive B: a sheet-like adhesive having a thickness of 15 μm ("P-0082" manufactured by Lintec Co., Ltd., and a storage elastic modulus of 0.04 MPa at 80 ° C]

Adhesive C: a sheet-like adhesive having a thickness of 5 μm [NCF # L2" manufactured by Lintec Co., Ltd., and a storage elastic modulus of 0.2 MPa at 80 ° C]

Adhesive D: a sheet-like adhesive having a thickness of 25 μm [NCF # E4" manufactured by Lintec Co., Ltd., and a storage elastic modulus of 0.8 MPa at 80 ° C]

Adhesive agent E: a sheet-like adhesive having a thickness of 25 μm [manufactured by Lintec Co., Ltd. as "flaky adhesive", the storage elastic modulus at 80 ° C is 1.3 MPa]

[protective film]

Prepare the following protective film.

Protective film: Cylindrical polyolefin resin film manufactured by Zeon Co., Ltd.: ZF14-013 (thickness: 13 μm, in-plane retardation value at wavelength 590 nm = 0.5 nm, phase difference in thickness direction at wavelength 590 nm = 3.3 nm)

[Optical film]

Prepare the following optical film.

Optical film: cellulose triacetate film manufactured by Konicaminolta Co., Ltd.; KC4UGR-HC (thickness 44 μm, in-plane retardation value at wavelength 590 nm = 106 nm, thickness direction retardation at wavelength 590 nm = 75 nm, R _th (590 ) /R _e (590)=0.71, R _e (450)/R _e (550)=0.96, R _e (630)/R _e (550)=1.02, dimensional change rate D1=0.08%, dimensional change rate D2 =0.26%, | D2 |/| D1 |=3.25)

[Example 1]

Corona treatment was performed on one side of the protective film, and saponification treatment was performed on the optical film. The corona-treated surface of the protective film and the polarizing film are connected by a water-based adhesive A polarizing plate with a protective film on one side is obtained. Next, an adhesive film of an adhesive film is obtained by adhering the adhesive agent B to one area of the optical film. The surface of the polarizing film of the polarizing plate of the single-sided protective film obtained is bonded to the adhesive film of the optical film with the adhesive, so that the absorption axis of the polarizing plate is 45° with the slow axis of the optical film. , obtained a polarizing plate. Further, an adhesive A was laminated on the protective film side of the obtained polarizing plate to obtain a polarizing plate with an adhesive. The polarizing plate has a degree of polarization of 99.993%.

The polarizing plate produced in this manner was cut into a 40 mm square and attached to EAGLE XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample for heat resistance evaluation was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.975%.

[Embodiment 2]

Corona treatment was performed on one side of the protective film, and saponification treatment was performed on the optical film. The corona-treated surface of the protective film and the polarizing film were followed by a water-based adhesive to obtain a polarizing plate having a protective film on one side. Next, an adhesive film of an adhesive is applied to an area of the optical film to obtain an optical film with an adhesive. The surface of the polarizing film of the polarizing plate of the single-sided protective film obtained is bonded to the adhesive film of the optical film with the adhesive, so that the absorption axis of the polarizing plate is 45° with the slow axis of the optical film. , obtained a polarizing plate. Further, an adhesive A was laminated on the protective film side of the obtained polarizing plate to obtain a polarizing plate with an adhesive. The polarizing plate has a degree of polarization of 99.997%.

The polarizing plate produced in this manner was cut into a 40 mm square and attached to EAGLE XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample for heat resistance evaluation was put into an oven at 105 ° C for 30 minutes. bell. The degree of polarization after the heat resistance test was 99.974%.

[Example 3]

Corona treatment was performed on one side of the protective film, and saponification treatment was performed on the optical film. The corona-treated surface of the protective film and the polarizing film were followed by a water-based adhesive to obtain a polarizing plate having a protective film on one side. Next, an adhesive film D is obtained on one area of the optical film to obtain an optical film with an adhesive. The surface of the polarizing film of the polarizing plate of the single-sided protective film obtained is bonded to the adhesive film of the optical film with the adhesive, so that the absorption axis of the polarizing plate is 45° with the slow axis of the optical film. , obtained a polarizing plate. Further, an adhesive A was laminated on the protective film side of the obtained polarizing plate to obtain a polarizing plate with an adhesive. The polarizing plate has a degree of polarization of 99.996%.

The polarizing plate produced in this manner was cut into a 40 mm square and attached to EAGLE XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample for heat resistance evaluation was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.975%.

[Example 4]

Corona treatment was performed on one side of the protective film, and saponification treatment was performed on the optical film. The corona-treated surface of the protective film and the polarizing film were followed by a water-based adhesive to obtain a polarizing plate having a protective film on one side. Next, an adhesive film E is obtained in one area of the optical film to obtain an optical film with an adhesive. The surface of the polarizing film of the polarizing plate of the single-sided protective film obtained is bonded to the adhesive film of the optical film with the adhesive, so that the absorption axis of the polarizing plate is 45° with the slow axis of the optical film. , obtained a polarizing plate. Further, an adhesive A was laminated on the protective film side of the obtained polarizing plate to obtain a polarizing plate with an adhesive. Polarizer The luminosity is 99.994%.

The polarizing plate produced in this manner was cut into a 40 mm square and attached to EAGLE XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample for heat resistance evaluation was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.973%.

[Comparative Example 1]

Corona treatment was performed on one side of the protective film, and saponification treatment was performed on the optical film. The corona-treated surface of the protective film, the polarizing film, and the optical film were sequentially passed through a water-based adhesive to obtain a polarizing plate. The absorption axis of the obtained polarizing plate was made 45° with the slow axis of the optical film. Further, an adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain a polarizing plate with an adhesive. The polarizing plate has a degree of polarization of 99.995%.

The polarizing plate produced in this manner was cut into a 40 mm square and attached to EAGLE XG manufactured by Corning Co., Ltd. to prepare a sample for heat resistance evaluation. The sample for heat resistance evaluation was placed in an oven at 105 ° C for 30 minutes. The degree of polarization after the heat resistance test was 99.962%.

The above results are summarized in Table 1.

(industrial availability)

According to the present invention, it is possible to provide a polarizing plate which can suppress a decrease in the degree of polarization caused by a shift in the absorption axis of the polarizing film due to a dimensional change of the optical film during the heat resistance test.

10‧‧‧Polar plate

11‧‧‧Optical film

12‧‧‧1st adhesive layer

14‧‧‧ polarizing film

15‧‧‧Protective film

16‧‧‧2nd adhesive layer

20‧‧‧Surface treatment layer

Claims (5)

A polarizing plate comprising, in order, an optical film, a first adhesive layer, a polarizing film, and a second adhesive layer; wherein an angle formed by an absorption axis of the polarizing film and a slow axis of the optical film is about 45° Or about 135°; with respect to the optical film, the dimensional change rate in the direction of 45° with respect to the absorption axis of the polarizing film after standing for 100 hours in an environment of 85° C. is set to D1, and When the dimensional change rate in the direction of 135° with respect to the absorption axis of the polarizing film after standing for 100 hours in an environment of 85 ° C is D2, the following formulas (1) and (2) are satisfied: | D1 |>| D2 |, 2<| D1 |/| D2 | (1) | D1 |<| D2 |, 2<| D2 |/| D1 | (2). The polarizing plate according to claim 1, wherein the optical film comprises a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth)acrylic resin. At least one of the selected groups. The polarizing plate according to claim 1 or 2, wherein the polarizing film has a thickness of 15 μm or less. The polarizing plate according to any one of claims 1 to 3, further comprising a protective film between the polarizing film and the second adhesive layer. A liquid crystal panel in which a polarizing plate according to any one of claims 1 to 4 is laminated on at least one surface of a liquid crystal cell via the second adhesive layer.