TWI711845B - 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 stretched during a heat resistance test.

The polarizing plate comprises a stretched optical film, a first protective film, a polarizing film and an adhesive layer in this order, wherein an angle between the absorption axis of the polarizing film and the slow axis of the optical film stretched is about 45° or about 135°; when the first protective film placed in an environment of 85℃ for 100 hours, it has a dimensional change rate D1 in a direction of 45° with respect to the absorption axis of the polarizing film, and a dimensional change rate D2 in a direction of 135° 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 |, 1 ≦ | D1 | / | D2 | ≦ 2 …(1) In the case of | D1 | < | D2 |, 1 < | D2 | / | D1 | ≦ 2 …(2).

Description

Polarizing plate and LCD panel

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

In recent years, liquid crystal displays that consume low power, operate at low voltage, and are lightweight and thin have been rapidly spreading as information display devices such as mobile phones, portable information terminals, computer screens, and televisions. With the development of liquid crystal technology, various types of liquid crystal displays have been proposed, and the problems of liquid crystal displays such as response speed and contrast, and narrow viewing angles are being solved. Moreover, with the popularization of portable liquid crystal displays, for example, when used outdoors, there are situations in which the screen of the liquid crystal display can be viewed with polarized sunglasses. In this case, the liquid crystal display is also required Even viewing the screen through polarized sunglasses is still excellent visibility.

Several methods have been proposed in the past to improve the visibility when viewing images through polarized sunglasses (Patent Documents 1 to 9).

[Prior Technical Literature] [Patent Literature]

[Patent Document 1] JP 2009-122454 A

[Patent Document 2] JP 2011-107198 A

[Patent Document 3] JP 2011-215646 A

[Patent Document 4] JP 2012-230390 A

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

[Patent Document 6] JP 2013-231761 A

[Patent Document 7] JP 2011-113018 A

[Patent Document 8] JP 2013-182162 A

[Patent Document 9] JP 2013-200445 A

The method used to improve the visibility when viewing images through polarized sunglasses is to convert linearly polarized light emitted from a polarizing plate arranged on the viewing side of an image display element such as a liquid crystal cell into A method of polarizing light from an ellipse circle (or circle), and arranging a phase difference plate (for example, a λ/4 wavelength plate) on the visible side of the above-mentioned polarizing plate (Patent Documents 1 to 9).

However, this type of retardation plate is often stretched and directly laminated on the polarizing film. Moreover, the angle formed by the absorption axis of the polarizing plate and the slow axis of the retardation plate is often arranged at a predetermined angle (for example, 45°). When the polarizing plate is put into a heat resistance test, there will The oblique size change causes a local change in the absorption axis of the polarizing film and reduces the degree of polarization.

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

[2] The polarizing plate according to [1], wherein the stretched optical film includes cyclic polyolefin resin, polycarbonate resin, cellulose resin, polyester resin, and (methyl) At least one selected from the group of acrylic resins.

[3] The polarizing plate according to [1] or [2], wherein the thickness of the polarizing film is 15 μm or less.

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

[5] A liquid crystal panel, which is arranged on at least one surface of a liquid crystal cell and is provided with the polarizing plate according to any one of [1] to [4].

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

10‧‧‧Polarizer

11‧‧‧Extended optical film

12‧‧‧Adhesive layer

13‧‧‧The first protective film

14‧‧‧Polarizing Film

15‧‧‧Second protective film

16‧‧‧Adhesive layer

20‧‧‧Surface treatment layer

21‧‧‧The direction at an angle of 45° with respect to the absorption axis of the polarizing film

22‧‧‧The direction at an angle of 135° relative to the absorption axis of the polarizing film

30‧‧‧Absorption axis of polarizing film

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

Figure 2 is an example of a plan view of the polarizing plate of the present invention.

Referring to Fig. 1, the layer structure of the polarizing plate 10 of the present invention will be described. The polarizing plate of the present invention is formed by laminating the stretched optical film 11, the first protective film 13, the polarizing film 14, and the adhesive layer 16 in this order. The angle formed by the absorption axis of the polarizing film 14 and the slow axis of the optical film 11 is preferably about 45° or about 135°. It is also useful to form the surface treatment layer 20 on the surface of the optical film 11 on the opposite side to the first protective film bonding surface.

Furthermore, the optical film 11 is preferably a film containing at least one selected from the group consisting of cyclic polyolefin resins, polycarbonate resins, cellulose resins, polyester resins, and (meth)acrylic resins. . Furthermore, from the viewpoint of the so-called reduction of anisotropy of the dimensional change of the polarizing plate during the heat resistance test, it is preferable to use a substantially unstretched film for the first protective film 13.

The term "substantially unstretched" in this specification means that the stretch magnification in any direction within the film plane is 1.1 times or less, preferably 1.05 times or less. Or from another point of view, it means that the retardation value in the film plane is 20 nm or less at a wavelength of 590 nm.

According to the present invention, it can also be provided in the polarizing film 14 and the adhesive There is a polarizing plate 10 with a second protective film 15 between the agents 16.

According to the present invention, it is also possible to provide a liquid crystal panel in which the above-mentioned polarizing plate 10 is laminated on at least one side of a liquid crystal cell via an adhesive layer 16.

The polarizing plate of the present invention has the first protective film 13 between the optical film 11 and the polarizing film 14 so that the ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is 1.5 or more , Or 3 or more, can effectively suppress the decrease in polarization degree. The ratio of the thickness of the stretched optical film 11 to the thickness of the polarizing film 14 is usually 10 or less.

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 manufactured through the following steps: a step of uniaxially stretching a polyvinyl alcohol-based resin film; a step of dyeing the polyvinyl alcohol-based resin film with a dichroic pigment to adsorb the dichroic pigment; The step of treating the polyvinyl alcohol-based resin film of the dichroic dye with an aqueous solution of boric acid and crosslinking; and the step of washing with water after the crosslinking treatment with the aqueous solution of boric acid.

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 other monomers copolymerizable with vinyl acetate in addition to polyvinyl acetate which is a homopolymer of vinyl acetate. Other monomers that can be copolymerized with vinyl acetate include, for example, unsaturated carboxylic acids, olefins, vinyl ethers, unsaturated sulfonic acids, and ammonium groups. Acrylic amides, etc.

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

Films made of such polyvinyl alcohol-based resins can be used as original films for polarizing films. The method of forming a polyvinyl alcohol resin into a film is not specifically limited, A well-known method can be formed into a film. The film thickness of the polyvinyl alcohol-based resin original sheet film is, for example, about 10 to 100 μm, preferably about 10 to 50 μm.

The uniaxial stretching of the polyvinyl alcohol-based resin film may be performed before dyeing with a dichroic dye, simultaneously with dyeing, or after dyeing. When performing uniaxial extension after dyeing, the uniaxial extension may be performed before the boric acid treatment or may be performed during the boric acid treatment. Of course, it is also possible to perform uniaxial extension in a plurality of stages shown here. Stretching on one axis can be used to stretch on one axis between rollers with different rotation speeds, or to stretch on one axis using hot rollers. Furthermore, uniaxial stretching can be performed by dry stretching in the atmosphere, or by wet stretching in a state where the polyvinyl alcohol-based resin film is stretched using a solvent such as water. The stretching ratio is usually about 3 to 8 times.

The dyeing of the polyvinyl alcohol-based resin film by a dichroic dye can be carried out, for example, by immersing the polyvinyl alcohol-based resin film in a film containing two The method is carried out in the aqueous solution of the color pigment. Specifically, iodine or a dichroic organic dye can be used for the dichroic dye system. In addition, it is preferable that the polyvinyl alcohol-based resin film be immersed in water and swelled before the dyeing treatment.

When iodine is used as a dichroic dye, a method of immersing a polyvinyl alcohol resin film in an aqueous solution containing iodine and potassium iodide for dyeing is usually adopted.

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

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

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

The polyvinyl alcohol resin film after boric acid treatment is usually washed with water. The water washing treatment can be performed, for example, by a method of immersing a polyvinyl alcohol-based resin film treated with boric acid 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 about 1 to 120 seconds.

After washing with water, a drying process is performed 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 about 30 to 100°C, preferably 50 to 80°C. The drying treatment time is usually about 60 to 600 seconds, preferably 120 to 600 seconds. Through the drying process, the moisture content in the polarizing film is reduced to a practical level. The moisture content is usually about 5 to 20% by weight, preferably 8 to 15% by weight. If the moisture content is less than 5% by weight, the flexibility of the polarizing film may be lost, and it may be damaged or broken after drying. Moreover, if the moisture content exceeds 20% by weight, the thermal stability tends to be insufficient.

According to the above operation, the polarizing film 14 with dichroic dyes adsorbed and oriented on the polyvinyl alcohol resin film can be manufactured.

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

[Stretched Optical Film 11]

In the polarizing plate used in the present invention, the stretched optical film 11 is a stretched film.

The stretched optical film 11 is particularly preferably composed of materials with excellent transparency, mechanical strength, thermal stability, and moisture shielding properties. Examples include polyolefin resins such as chain polyolefin resins (polypropylene resins, etc.), cyclic polyolefin resins (norbornene resins, etc.); such as cellulose triacetate, Cellulose resins such as cellulose ester resins such as cellulose diacetate; polyester resins; polycarbonate resins; (meth)acrylic resins; polystyrene resins; or mixtures or copolymers of these Things etc. Among them, from the viewpoint of making the present invention more effective, it is preferable to include cellulose resins such as cellulose ester resins such as cellulose triacetate and cellulose diacetate.

The stretched optical film 11 is preferably a film satisfying the following formula: (5) 100nm≦R _e (590)≦180nm, (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. _{Wherein, R e (590), R} e (450), R e (550), R e (630) are shown in a measurement wavelength 590nm, 450nm, 550nm, 630nm within the plane retardation value, R _th (590) Represents the thickness direction retardation value at a measurement wavelength of 590 nm. These in-plane retardation values and thickness direction retardation values are measured under an environment with a temperature of 23°C and a relative humidity of 55%.

By the in-plane retardation value R _e extending in the optical film 11, a thickness direction retardation R _th, based on the refractive index in-plane slow axis direction is set to n _x, in-plane fast axis direction (the plane slow axis direction in a vertical direction) is set to a refractive index n _y, the refractive index in the thickness direction is set to n _z, thickness of the optical film 11 is defined as extending through d, defined by the following formula: R _e = (n _x -n _y )×d R _th =[{(n _x +n _y )/2}-n _z ]×d.

The liquid crystal display formed by disposing the stretched optical film 11 showing the phase difference characteristics and wavelength dispersion characteristics of the above formulas (5) to (8) on the viewing side can effectively suppress the transmission of polarized sunglasses from various directions (azimuths). Angle and polar angle) the hue changes when viewing the screen, which can improve the visibility of the liquid crystal display. In contrast, when any one or more of the above-mentioned formulas (5) to (8) are not satisfied, the suppression of the above-mentioned hue change may be insufficient.

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

The stretched optical film 11 may have a polarizing film 14 The linearly polarized light emitted to the optical film 11 is converted into elliptic circularly polarized light (including the case of circularly polarized light) and emitted. In order to show this function, the absorption axis of the polarizing film and the optical film Laminated so that the angle formed by the slow axis becomes approximately 45° or approximately 135°. When the angle is outside this range, the function of converting linear polarized light into elliptical polarized light and emitting it cannot be obtained. As a result, the suppression of the above-mentioned hue change becomes insufficient. The angle formed is preferably 35 to 55° or 125 to 145°, and more preferably 40 to 50° or 130 to 140°.

Since it is easy to impart the retardation characteristics and wavelength dispersion characteristics of the above formulas (5) to (8), and because the moisture permeability is low, the moisture resistance and moisture resistance of the optical laminate can be improved, so the stretched optical film is It is preferable to include at least one selected from the group consisting of cyclic polyolefin resin, polycarbonate resin, cellulose resin, polyester resin, and (meth)acrylic resin.

As for the chain polyolefin resin, in addition to homopolymers of chain olefins such as polyethylene resins and polypropylene resins, for example, copolymers containing two or more kinds of chain olefins can also be mentioned.

Cyclic polyolefin resin is a general term for resins obtained by polymerizing cyclic olefin as a polymerization unit. Specific examples of cyclic polyolefin resins include: ring-opening (co)polymers of cyclic olefins; addition polymers of cyclic olefins; cyclic olefins and chain olefins such as ethylene and propylene Copolymers (representatively random copolymers); and graft polymers modified with unsaturated carboxylic acids or derivatives thereof; and hydrogenated products thereof. Among them, it is particularly preferable to use norbornene resin, which uses norbornene and A polycyclic norbornene monomer such as a norbornene monomer is a cyclic olefin.

Cellulose ester resin is an ester of cellulose and fatty acid. Specific examples of the cellulose ester resin include cellulose triacetate, cellulose diacetate, cellulose tripropionate, and cellulose dipropionate. Furthermore, these copolymers, or a part of the hydroxyl group modified with other substituents may also be used. Among these, cellulose triacetate (ie, cellulose triacetate: TAC) is particularly preferred.

Polyester resins are resins having ester bonds, and generally include polycondensates of polycarboxylic acids or their derivatives and polyhydric alcohols. Polycarboxylic acid or its derivative, dicarboxylic acid or its derivative can be used, for example: terephthalic acid, isophthalic acid, dimethyl terephthalate, dimethyl naphthalate Wait. Divalent diols can be used as the polyol, and examples thereof include ethylene glycol, propylene glycol, butylene glycol, neopentyl glycol, and cyclohexane dimethanol.

Specific examples of polyester resins include: polyethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polytrimethylene terephthalate Esters, poly(propylene naphthalate), poly(cyclohexane dimethyl terephthalate), poly(cyclohexane dimethyl naphthalate).

The polycarbonate resin contains a polymer in which a monomer unit is bonded via a carbonate group. The polycarbonate resin may also be a resin called a modified polycarbonate, or a copolymerized polycarbonate, which has a modified polymer backbone.

The (meth)acrylic resin is a resin having a compound having a (meth)acryloyl group as a main monomer. Specific examples of (meth)acrylic resins include, for example, poly(meth)acrylates such as polymethyl methacrylate; methyl methacrylate-(meth)acrylic acid copolymers; methyl methacrylate-( Meth)acrylate copolymer; methyl methacrylate-acrylate-(meth)acrylic acid copolymer; methyl (meth)acrylate-styrene copolymer (MS resin, etc.); methyl methacrylate with Copolymers of alicyclic hydrocarbon-based compounds (for example: methyl methacrylate-cyclohexyl methacrylate copolymer, methyl methacrylate-norbornyl (meth)acrylate copolymer, etc.). Preferably, a polymer containing poly(meth)acrylate C _1-6 alkyl esters such as polymethyl(meth)acrylate as the main component can be used, and more preferably, a polymer containing methyl methacrylate as the main component can be used (50 to 100% by weight, preferably 70 to 100% by weight) of methyl methacrylate resin.

The stretched optical film 11 can be produced by stretching the film containing the above-mentioned thermoplastic resin. The stretching treatment may include one-axis stretching and two-axis stretching. Extending directions include: the mechanical flow direction (MD) of the unstretched film, the direction perpendicular to it (TD), the direction obliquely intersecting with the mechanical flow direction (MD), etc. The two-axis extension can be simultaneous two-axis extension while extending in two extension directions, or it can be a sequential two-axis extension that extends in a predetermined direction and then extends in other directions. The stretching treatment can be carried out, for example, by using two or more pairs of nip rolls that increase the rotation speed on the outlet side and stretching in the longitudinal direction (machine flow direction: MD), or by unstretching The two ends of the film are clamped by chuck and stretched in a direction (TD) perpendicular to the direction of mechanical flow. At this time, by adjusting the thickness of the film or adjusting the stretching ratio, the retardation value and the wavelength dispersion can be adjusted within the range of the above formulas (5) to (6). Furthermore, 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 stretched optical film 11 is not particularly limited as long as it satisfies the above formulas (5) to (8), but from the viewpoint of thinning the polarizing plate, it is preferably 90 μm or less, and more preferably 60 μm or less, and From the viewpoint of handling, it is preferably 5 μm or more, and more preferably 10 μm or more.

The stretched optical film 11 may contain one or more additives such as smoothing agent, plasticizer, dispersant, heat stabilizer, ultraviolet absorber, infrared absorber, antistatic agent, antioxidant, etc.

Furthermore, in order to impart desired surface optical properties 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 anti-glare layer, an anti-reflection layer, an antistatic layer, and an antifouling layer. The method of forming a coating layer is not specifically limited, A well-known method can be used.

[第1保护膜13]

The first protective film 13 is particularly preferably composed of a material excellent in transparency, mechanical strength, thermal stability, and moisture shielding properties. From the viewpoint of easy availability, the first protective film 13 preferably contains at least one selected from the group consisting of cellulose resin, polyolefin resin, and acrylic resin. Here, the term "polyolefin resin system" includes chain polyolefin resin and cyclic polyolefin resin. In this specification, having transparency refers to a film with a monomer transmittance of 80% or more in the visible light region.

The cellulose resin, polyolefin resin, or acrylic resin may be the same as those used for the optical film.

The method of forming a film from the above resin can be appropriately selected according to each resin. For example, solvent casting method, melt extrusion method can be used. Out of law and so on. Among them, for polyolefin resins and acrylic resins, it is preferable to adopt a melt extrusion method from the viewpoint of productivity. On the other hand, in general, cellulose resins are formed into films by solvent casting methods.

The first protective film 13 is used: the dimensional change rate D1 in the direction of 45° with respect to the absorption axis of the polarizing film after standing for 100 hours at 85°C, and 135 with respect to the absorption axis of the polarizing film The dimensional change rate D2 in the direction of ° satisfies the following formula (1) and formula (2). In this specification, the direction where the angle formed by the absorption axis of the polarizing film is 45° and the direction where the angle formed by the absorption axis of the polarizing film is 135° is the main surface of the polarizer as shown in Figure 2. The inner angles respectively indicate a direction 21 at an angle of 45° with respect to the absorption axis 30 of the polarizing film, and a direction 22 at an angle of 135° with respect to the absorption axis 30 of the polarizing film, respectively. In addition, when viewing the polarizing film 14 from the stretched optical film 11, the angle rotated counterclockwise is positive. When ｜D1｜≧｜D2｜, 1≦｜D1｜/｜D2｜≦2 (1) ｜D1｜<｜D2｜, 1<｜D2｜/｜D1｜≦2 (2)

The film that satisfies the above formula has a small anisotropy of thermal shrinkage and thermal expansion during the heat resistance test, so that the shift of the absorption axis of the polarizing film 14 caused by the dimensional change of the stretched optical film due to heat can be suppressed. The film satisfying the above-mentioned formulas (1) and (2) can be obtained by not being substantially stretched when the film is manufactured. In the present specification, "substantially unstretched" means that the stretching ratio in any direction within the film surface is 1.1 times or less, preferably 1.05 times or less. Or from another point of view, it means that the retardation value in the film plane is 20 nm or less at a wavelength of 590 nm.

D1 and D2 in the above formulas (1) and (2) can be based on the following The way to determine. First, the film is cut to a size of 100 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 film was allowed to stand for 1 day in an environment with a temperature of 23°C and a humidity of 55%, and the dimensions (L0(45)) in the direction of 45° with respect to the absorption axis of the polarizing film (L0(45)) and the The size of the absorption axis is 135° (L0(135)). Secondly, measure the dimension (L1(45)) in the direction of 45° with the absorption axis of the polarizing film (L1(45)) and the dimension in the direction of 135° with the absorption axis of the polarizing film ( L1(135)). Based on the results, the dimensional change rates D1 (%) and D2 (%) can be obtained from equations (3) and (4). Size change rate D1=[(L0(45)-L1(45))/L0(45)]×100 (3) Size change rate D2=[(L0(135)-L1(135))/L0(135) )×100 (4)

By using the first protective film that satisfies the above formulas (1) and (2), even when the stretched optical film is a film with a large dimensional change rate satisfying the following formula, the present invention can appropriately suppress the polarization of the polarizing plate Degree decreases. In addition, in the following formulas (1) and (2), the left side of each formula may be 2.5 or more, or 3.0 or more. When ｜D1｜≧｜D2｜, 2≦｜D1｜/｜D2｜ (1’) ｜D1｜<｜D2｜, 2<｜D2｜/｜D1｜ (2’)

In addition, in the above formulas (1') and (2'), the definitions of D1 and D2 are the same as those in the above formulas (1) and (2).

[Second protective film 15]

The second protective film 15 is particularly preferably composed of materials excellent in transparency, mechanical strength, thermal stability, and moisture shielding properties. Regarding the second protective film 15, it is easy to control the retardation value and easy to obtain From a viewpoint, it is preferable to contain a cellulose resin, a polyolefin resin, or an acrylic resin. Here, the term "polyolefin resin system" includes chain polyolefin resin and cyclic polyolefin resin.

As the cellulose resin, polyolefin resin, or acrylic resin, the same ones as those used for the first protective film can be used.

The method of forming a film from the above-mentioned resin may be appropriately selected according to each resin, and for example, the solvent casting method and the melt extrusion method described above can be used. Among them, for polyolefin resins and acrylic resins, it is preferable to adopt a melt extrusion method from the viewpoint of productivity. On the other hand, in general, cellulose resins are formed into films by solvent casting methods.

When the liquid crystal cell is in the lateral electric field effect (IPS: In-Plane Switching) mode, in order not to impair the original wide viewing angle characteristics of the IPS mode liquid crystal cell, the transparent protective film has a thickness direction retardation value R _th of -10 The range to 10 nm is preferable.

The method of adjusting the retardation value R _th in the thickness direction of the transparent protective film within the range of -10 to 10 nm includes a method of reducing the distortion remaining in the plane and in the thickness direction as much as possible when the film is produced. In the above-mentioned solvent casting method, for example, a method in which residual shrinkage distortion in the plane and thickness direction generated when the casting resin solution is dried is relieved by heat treatment. On the other hand, in the above-mentioned melt extrusion method, in order to prevent the resin film from being stretched from the die to the cooling, the distance from the die to the cooling cylinder can be shortened as much as possible and the film is not stretched. Ways to control the extrusion volume and the rotation speed of the cooling drum, etc. Moreover, similarly to the solvent casting method, a method in which distortion remaining in the obtained film is alleviated by heat treatment can also be adopted.

[Lamination of polarizing film and protective film]

The bonding of the polarizing film and the first protective film and the bonding of the polarizing film and the second protective film may be bonded by an adhesive or an adhesive, and bonding is preferably by an adhesive. In this specification, the first protective film and the second protective film may be collectively referred to as protective films.

The adhesive layer for bonding the polarizing film and the protective film 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. As long as the thickness of the adhesive layer is within this range, floating and peeling will not occur between the laminated protective film and the polarizing film, and an adhesive force that is practically no problem can be obtained. The adhesive layer for bonding the polarizing film and the protective film may have a thickness of about 5 to 50 μm, preferably 5 to 30 μm, and more preferably 10 to 25 μm.

When adhering the polarizing film and the protective film, it is also useful if the polarizing film and the protective film are subjected to saponification treatment, corona treatment, plasma treatment, etc. in advance.

The adhesive system can be suitably used when the optical film and the protective film described later are laminated.

In the formation of the adhesive layer, an appropriate adhesive can be appropriately used according to the type and purpose of the object to be adhered, and an anchor coating agent can also be used as needed. Examples of the adhesive include solvent-based adhesives, emulsion-type adhesives, pressure-sensitive adhesives, remoisturizing adhesives, polycondensation-type adhesives, solvent-free adhesives, film-like adhesives, and hot melt Type adhesive, etc.

One of the preferable adhesives includes water-based adhesives, even if the adhesive components are dissolved or dispersed in water. To cite examples of adhesive components that are soluble in water, there are polyvinyl alcohol-based resins. Moreover, if an example of an adhesive component that can be dispersed in water is given, there is a urethane-based resin having a hydrophilic group. The water-based adhesive can be prepared by mixing such an adhesive component and additional additives prepared as necessary in water. To cite examples of commercially available polyvinyl alcohol-based resins that can be used as water-based adhesives, there is "KL-318" which is a carboxylic acid group-modified polyvinyl alcohol sold by Kuraray Co., Ltd.

The water-based adhesive may contain a crosslinking agent as needed. To cite examples of crosslinking agents, there are amine compounds, aldehyde compounds, methylol compounds, water-soluble epoxy resins, isocyanate compounds, and polyvalent metal salts. When a polyvinyl alcohol resin is used as an adhesive component, it is preferable to use an aldehyde compound including glyoxal, a methylol compound including methylol melamine, a water-soluble epoxy resin, etc. as a crosslinking agent.

Here, the water-soluble epoxy resin can be, for example, a polyamide epoxy resin obtained by reacting a polyamide polyamine with epichlorohydrin, and the polyamide polyamine is based on diethylene triamine, tertiary A reaction product of polyalkylene polyamines such as ethylenetetramine and dicarboxylic acids such as adipic acid. To cite examples of commercially available water-soluble epoxy resins, there are "Sumirez Resin (registered trademark) 650(30)" sold by Taoka Chemical Industry Co., Ltd. and the like.

A water-based adhesive is applied to the adhesive surface of the polarizing film and/or the protective film bonded to the polarizing film and the two are bonded together, and then drying is performed to obtain a polarizing plate. Before proceeding, if the protective film is applied It is also effective for easy subsequent treatments such as saponification treatment, corona discharge treatment, plasma treatment or primer treatment to improve the wettability. The drying temperature may be about 50 to 100°C, for example. From the viewpoint of further improving the adhesive force, it is preferable to mature 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 preferable adhesive includes a curable adhesive composition containing an epoxy compound that is cured by irradiation with active energy rays or heating. Here, the curable epoxy compound has at least two epoxy groups in the molecule. At this time, the adhesion of the polarizing film and the protective film can be carried out by the following method: a method of irradiating the coating layer of the adhesive composition with active energy rays or applying heat to harden the curable epoxy compound contained in the adhesive . The curing of epoxy compounds is generally carried out by cationic polymerization of epoxy compounds. Furthermore, from the viewpoint of productivity, this curing is preferably performed by irradiation with active energy rays.

From the viewpoints of weather resistance, refractive index, cationic polymerizability, etc., the epoxy compound contained in the curable adhesive composition preferably contains no aromatic ring in the molecule. Examples of epoxy compounds that do not contain aromatic rings in the molecule include hydrogenated epoxy compounds, alicyclic epoxy compounds, and aliphatic epoxy compounds. Such an epoxy compound suitable for use in a curable adhesive composition is described in detail in, for example, Japanese Patent Application Laid-Open No. 2004-245925, and is also described briefly here.

The hydrogenated epoxy compound may be obtained by glycidyl etherification of a nuclear hydrogenated polyhydroxy compound. The nuclear hydrogenated polyhydroxy compound is obtained by making an aromatic polyhydroxy compound which is a raw material of an aromatic epoxy compound in It is obtained by selective nuclear hydrogenation reaction in the presence of catalyst and under pressure. Aromatic polyhydroxy compounds that are the raw materials of aromatic epoxy compounds, for example, bisphenols such as bisphenol A, bisphenol F and bisphenol S; such as phenol novolac resin, cresol novolac resin And novolac resins such as paraben novolac resin; such as polyfunctional compounds such as tetrahydroxydiphenylmethane, tetrahydroxybenzophenone and polyvinylphenol. By subjecting such an aromatic polyhydroxy compound to a nuclear hydrogenation reaction and reacting the obtained nuclear hydrogenated polyhydroxy compound with epichlorohydrin, glycidyl etherification can be performed. Examples of suitable hydrogenated epoxy compounds include hydrogenated glycidyl ether of 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 an alicyclic ring" means a bridged oxygen atom -O- in the structure shown in the following formula, where m is an integer from 2 to 5.

The compound formed by combining the radical of the form after removing one or more hydrogen atoms in (CH ₂ ) _m of this formula with other chemical structures may be an alicyclic epoxy compound. Furthermore, one or more hydrogen atoms in (CH ₂ ) _m forming an alicyclic ring may be appropriately substituted with a linear alkyl group such as a methyl group or an ethyl group. Among the alicyclic epoxy compounds, epoxy compounds with oxabicyclohexane ring (m=3 in the above formula) and oxabicycloheptane ring (m=4 in the above formula) are due to their excellent performance The adhesion is better. Specific examples of alicyclic epoxy compounds are disclosed below. Here, the compound name is listed first, and then the corresponding chemical formula is shown respectively, and the same symbol is attached to the compound name and the chemical formula corresponding to the chemical name.

A: 3,4-epoxycyclohexanecarboxylic acid 3,4-epoxycyclohexyl methyl ester, B: 3,4-epoxy-6-methylcyclohexanecarboxylic acid 3,4-epoxy -6-Methylcyclohexyl methyl ester, C: ethylene bis(3,4-epoxycyclohexanecarboxylate), D: adipic acid bis(3,4-epoxycyclohexylmethyl) ) Ester, E: bis(3,4-epoxy-6-methylcyclohexylmethyl) adipic acid ester, F: diethylene glycol bis(3,4-epoxycyclohexylmethyl ether) , G: ethylene glycol bis (3,4-epoxycyclohexyl methyl ether), H: 2,3,14,15-diepoxy-7,11,18,21-tetraoxatrispiro [5.2.2.5.2.2] Eicosan, I: 3-(3,4-epoxycyclohexyl)-8,9-epoxy-1,5-dioxaspiro[5.5]undecane , J: Dioxide 4-vinylcyclohexene dioxide (4-vinylcyclohexene dioxide), K: Limonene dioxide (limonene dioxide), L: Bis (2,3-epoxycyclopentyl) ether, M: Dioxide Dicyclopentadiene and so on.

The aliphatic epoxy compound may be a polyglycidyl ether of an aliphatic polyol or an alkylene oxide adduct thereof. More specifically, examples include: diglycidyl ether of propylene glycol; 1,4-butanediol Diglycidyl ether; 1,6-hexanediol diglycidyl ether; glycerol triglycidyl ether; trimethylolpropane triglycidyl ether; for ethylene glycol, propylene glycol and glycerol and other fats The polyglycidyl ether of polyether polyol (for example, diglycidyl ether of polyethylene glycol) and the like are obtained by adding alkylene oxide (for example, ethylene oxide, propylene oxide) to the group polyol.

In the curable adhesive composition, 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 that can be used in the curable adhesive composition usually has an epoxy equivalent in the 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 with an epoxy equivalent of less than 30g/equivalent is used, the flexibility of the polarizing plate after curing may decrease, and the subsequent strength may decrease. On the other hand, when a compound having an epoxy equivalent of more than 3,000 g/equivalent is used, the compatibility with other components contained in the adhesive composition may decrease.

From the viewpoint of reactivity, it is preferable to use cationic polymerization as the curing reaction of the epoxy compound. Therefore, it is preferable to formulate a cationic polymerization initiator in the curable adhesive composition containing an epoxy compound. The cationic polymerization initiator generates cationic species or Lewis acid by irradiating active energy rays such as visible rays, ultraviolet rays, X-rays, and electron rays or heating to start the polymerization reaction of epoxy groups. From the viewpoint of workability, the cationic polymerization initiator is preferably provided with latent properties. Below, the system will generate cationic species or pathways by irradiating active energy rays The cationic polymerization initiator that starts the polymerization reaction of epoxy group is called "photocationic polymerization initiator". In addition, it will generate cationic species or Lewis acid by heat and start polymerization of epoxy group The reactive cationic polymerization initiator is called "thermal cationic polymerization initiator".

The method of curing the adhesive composition by using a photocationic polymerization initiator and irradiating active energy rays is because it can be cured under normal temperature and humidity, and it is less necessary to consider the heat resistance or expansion of the polarizing film. The resulting skew, and the protective film and the polarizing film can be bonded well, which is advantageous. Furthermore, since the photocationic polymerization initiator acts as a catalyst by light, even if it is mixed with an epoxy compound, the storage stability and workability are still excellent.

Examples of the photocationic polymerization initiator include aromatic diazonium salts; onium salts such as aromatic iodonium salts and aromatic sulfonium salts, iron-allene complexes, and the like. 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, relative to 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 relative to 100 parts by weight of the epoxy compound, curing will become insufficient, and the mechanical strength and adhesive strength of the cured product will tend to decrease.

On the other hand, relative to 100 parts by weight of the epoxy compound, if the blending amount of the photocationic polymerization initiator exceeds 20 parts by weight, the ionic substances in the cured product will increase, and the moisture absorption of the cured product will increase. , May reduce durability.

When using a photocationic polymerization initiator, the curable adhesion The agent composition may further contain a photosensitizer if necessary. By using a photosensitizer, the reactivity of cationic polymerization can be improved, and the mechanical strength and adhesive strength of the hardened product can be improved. Examples of photosensitizers include carbonyl compounds, organic sulfides, persulfides, redox compounds, azo compounds, diazo compounds, halogen compounds, and photoreducible dyes. When the photosensitizer is formulated, the amount is preferably set within the range of 0.1 to 20 parts by weight relative to 100 parts by weight of the curable adhesive composition. Moreover, in order to increase the curing speed, sensitizers such as naphthoquinone derivatives can also be used.

On the other hand, thermal cationic polymerization initiators include: benzyl sulfonium salt, thiophenium salt, thiolanium salt, benzyl ammonium, pyridinium salt, hydrazine salt ( hydrazinium salt), carboxylic acid ester, sulfonic acid ester, amido imine, etc.

The curable adhesive composition containing an epoxy compound is preferably cured by photocationic polymerization as described above, but the thermal cationic polymerization initiator can be present and cured by thermal cationic polymerization, or it can be used in combination Photo cationic polymerization and thermal cationic polymerization. When photocationic polymerization and thermal cationic polymerization are used in combination, it is preferable to include both a photocationic polymerization initiator and a thermal cationic polymerization initiator in the curable adhesive composition.

Moreover, the curable adhesive composition may further contain compounds that promote cationic polymerization, such as oxetane compounds and polyol compounds. The oxetane compound is a compound having a 4-membered cyclic ether in the molecule. When the oxetane compound is formulated, its amount in the curable adhesive composition is usually 5 to 95% by weight, and preferably 5 to 50% by weight. Moreover, the polyol compound may include ethylene glycol or hexamethylene glycol, polyethylene Alkylene glycol or its oligomers such as diol, polyester polyol, polycaprolactone polyol, polycarbonate polyol, etc. When the polyol compound is blended, the amount is usually 50% by weight or less in the curable adhesive composition, and preferably 30% by weight or less.

In addition, the curable adhesive composition may contain other additives, such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, without impairing its adhesion. , Filling agent, flow regulator, plasticizer, defoamer, etc. Examples of the ion trapping agent include powdery inorganic compounds including bismuth, antimony, magnesium, aluminum, calcium, titanium, and a mixture of these. Examples of antioxidants include hindered phenol antioxidants. Wait.

After coating the curable adhesive composition containing epoxy compound on the adhesive surface of the polarizing film or the protective film, or the adhesive surface of the two, the adhesive-coated surface is bonded together and irradiated with active energy rays Or heating to harden the uncured adhesive layer, thereby bonding the polarizing film and the protective film. Various coating methods such as a doctor blade, a wire rod, a die coater, a comma coater, and a gravure coater can be used for the coating method of the adhesive.

This curable adhesive composition can basically be used as a solvent-free adhesive that contains substantially no solvent. However, since various coating methods have their own optimum viscosity ranges, they can also contain solvents for viscosity adjustment. . The solvent is preferably an organic solvent that does not reduce the optical properties of the polarizing film and can well dissolve various components such as epoxy compounds. For example, hydrocarbons represented by toluene, esters represented by ethyl acetate, etc. can be used .

When curing the adhesive composition by irradiating an active energy ray, the active energy ray can be any of the above-mentioned active energy rays. However, in terms of easy handling and easy control of the amount of irradiated light, it is preferable to use ultraviolet rays. The irradiation intensity and amount of active energy rays (such as ultraviolet rays) are within the range that does not affect the various optical properties of the polarizing film, including the degree of polarization, and the protective film’s various optical properties, including the transparency and retardation characteristics. Decide appropriately in a way that maintains appropriate productivity.

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

[Layer of the first protective film 13 and the optical film 11]

The laminated layer of the first protective film 13 and the optical film 11 may be the same as the adhesive used for bonding the polarizing film and the protective film. In another aspect, it is preferable to use an adhesive for the lamination of the first protective film 13 and the optical film 11.

[Adhesive layer 12]

The adhesive layer 12 used for the lamination of the first protective film 13 and the optical film 11 should be one that has excellent optical transparency, appropriate wettability, and excellent adhesion properties including cohesiveness, adhesiveness, etc., preferably It is further superior in durability. Specifically, the adhesive forming the adhesive layer 12 is preferably an adhesive containing acrylic resin (acrylic adhesive).

The acrylic resin contained in the acrylic adhesive is based on butyl acrylate, ethyl acrylate, isooctyl acrylate and acrylic acid A resin in which alkyl acrylate such as 2-ethylhexyl ester is the main monomer. Polar monomers are usually copolymerized in the acrylic resin. A polar single-system compound with a polymerizable unsaturated bond and a polar functional group. Among them, the polymerizable unsaturated bond is generally derived from (meth)acrylic acid groups, and the polar functional groups can be carboxyl groups, hydroxyl groups, and amide groups. , Amine group, epoxy group, etc. To cite specific examples of polar monomers, there are (meth)acrylic acid, 2-hydroxypropyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate, (meth)acrylamide, (meth)acrylamide, Base) 2-N,N-dimethylaminoethyl acrylate, glycidyl (meth)acrylate, etc.

Furthermore, in acrylic adhesives, the crosslinking agent is usually formulated together with acrylic resin.

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

Various additives can be further formulated in the adhesive. Suitable additives include silane coupling agents and antistatic agents. Silane coupling agent is effective in improving adhesion to glass. Antistatic agents are effective in reducing or preventing static electricity generation.

The adhesive layer 12 can be formed by the following method: preparing an adhesive composition prepared by dissolving the above-mentioned adhesive components in an organic solvent, and applying the adhesive composition directly on any subsequent bonding surface (polarized light Film or protective film), and drying to remove the solvent; or, coating the above-mentioned adhesive composition on the release treatment surface of the base film containing the resin film that has been subjected to release treatment, and drying to remove the solvent to make an adhesive The method of transferring the adhesive and attaching the adhesive layer to any bonding surface (polarizing film or protective film). When the adhesive layer 12 is formed by the former direct coating method, conventionally, A resin film (also called a separator) that has undergone a release treatment is attached to its surface to temporarily protect the surface of the adhesive layer until it is used. From the viewpoint of the handleability of the adhesive composition of an organic solvent solution, the latter transfer method is often used. In this case, the release-treated base film used in the initial formation of the adhesive layer is It can be directly used as a separator after being attached to the polarizing plate, which is also suitable for this feature.

Before laminating with an adhesive and an adhesive, it is also useful to perform corona treatment and plasma treatment on the polarized film surface, protective film surface, and adhesive surface to be bonded in advance.

[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 adhesive layer 16 formed on the side of the polarizing film 14 away from the first protective film may be one that has excellent optical transparency, appropriate wettability, and excellent adhesion properties including cohesion, adhesiveness, etc., preferably To use those that are further superior in durability. Specifically, as the adhesive forming the adhesive layer, it is preferable to use an acrylic resin-containing adhesive (acrylic adhesive). Specifically, the same thing as the adhesive 12 mentioned above can be used. The adhesive layer 16 and the adhesive layer 12 may be formed of the same adhesive or different adhesives.

The adhesive layer 16 can contain various additives similarly to the adhesive layer 12. Among them, it is preferable that the adhesive layer 16 contains an antistatic agent. Generally speaking, when a polarizing plate is attached to a liquid crystal cell via an adhesive layer, it is a surface protection film (separator) that has been covered with the adhesive layer for temporary protection It is peeled and then attached to the liquid crystal cell, but when the surface protective film is peeled off, static electricity will be generated and the liquid crystal in the liquid crystal cell will have poor orientation. This phenomenon may lead to poor display of the liquid crystal display device. Regarding the means to reduce or prevent the generation of such static electricity, it is effective to mix antistatic agents in the adhesive.

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

[Method of manufacturing polarizing plate]

The method of manufacturing the polarizing plate of the present invention is not particularly limited. For example, a polarizing plate composed of the first protective film 13, the polarizing film 14, and the second protective film 15, and the optical film 11 and the adhesive can be prepared in advance. The adhesive-attached optical film formed by the layer 12 is laminated, and the two are laminated through the adhesive layer 12 of the adhesive-attached optical film in a roll-to-roll method to obtain polarized light Board 10. By further forming the adhesive layer 16 on the second protective film 15, the polarizing plate can be attached to the liquid crystal cell through the adhesive layer 16.

[LCD cell]

The liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the two substrates. The unit substrate is generally composed of glass, but it can also be a plastic substrate. In addition, the liquid crystal cell itself used in the liquid crystal panel of the present invention can be composed of various materials used in this field.

[LCD panel]

The polarizing plate 10 is attached to the liquid crystal cell through the adhesive layer 16 to produce a liquid crystal panel. The polarizing plate of the present invention only needs to be attached to the liquid crystal cell At least one of the back side and the visible side is sufficient. The polarizing plate of the present invention is preferably attached to the liquid crystal cell by arranging the polarizing plate of the present invention on the visible side of the liquid crystal display device.

[Example]

The following series of examples illustrate the present invention in detail, but the present invention is not limited by these examples. The examples indicate the content or use amount in parts and %. Unless otherwise specified, it is the weight basis. In addition, the physical properties of the following examples were measured by the following methods.

(1) Measurement of thickness:

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

(2) Measurement of in-plane retardation and thickness direction retardation:

Using the phase difference meter "KOBRA (registered trademark)-WPR" manufactured by Oji Measuring Instruments Co., Ltd. based on the parallel nicols rotation method, the in-plane retardation at a predetermined wavelength at a temperature of 23°C is measured And thickness direction retardation.

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

Use a spectrophotometer with an integrating sphere ("V7100" manufactured by JASCO Corporation, 2 degree field of view; C light source].

(4) Measuring method of dimensional change rate of film

Measure the dimensional change rate D1 in the direction of 45° with respect to the absorption axis of the polarizing film after the film is allowed to stand for 100 hours in an environment of 85°C, and the size in the direction of 135° with respect to the absorption axis of the polarizing film The method of the rate of change D2 is as follows. First, cut the film to make it The retracted axis is 100mm in the 45° direction and 100mm in the 135° direction. The cut film was allowed to stand for 1 day in an environment with a temperature of 23°C and a humidity of 55%, and the size (L0(45)) in the direction of 45° relative to the absorption axis of the polarizing film and the absorption relative to the polarizing film were measured The size of the axis is 135° (L0(135)). Next, measure the dimension (L1(45)) in the direction of 45° with respect to the absorption axis of the polarizing film (L1(45)) and 135° with respect to the absorption axis of the polarizing film after standing for 100 hours in an environment of 85°C The size of the direction (L1(135)). Based on the results, the dimensional change rates D1 (%) and D2 (%) are obtained from equations (3) and (4). Size change rate D1=[(L0(45)-L1(45))/L0(45)]×100 (3) Size change rate D2=[(L0(135)-L1(135))/L0(135) )×100 (4)

[Manufacturing example 1] Making of polarizing film

A polyvinyl alcohol film with a thickness of 30μm (average degree of polymerization of about 2400, saponification degree of 99.9 mol% or more) is stretched to about 4 times in one axis by dry stretching, and then kept tight in pure water at 40°C After being immersed in the medium for 40 seconds, it was immersed in an aqueous solution with a weight ratio of iodine/potassium iodide/water of 0.052/5.7/100 at 28°C for 30 seconds for dyeing treatment. After that, it was immersed in an aqueous solution with a weight ratio of potassium iodide/boric acid/water of 11.0/6.2/100 at 70°C for 120 seconds. Then, after washing with pure water at 8°C for 15 seconds, drying at 60°C for 50 seconds while maintaining a tension of 300N, followed by drying at 75°C for 20 seconds, to obtain a thickness of 12μm with iodine adsorbed on the polyvinyl alcohol film. The absorption type polarizer.

[Production example 2] Production of water-based adhesive

With respect to 100 parts by weight of water, 3 parts by weight of polyvinyl alcohol modified with carboxyl groups (trade name "KL-318" obtained from Kuraray Co., Ltd.) are dissolved, Add a polyamide epoxy additive which is a water-soluble epoxy resin to the aqueous solution (trade name "Sumirez Resin (registered trademark) 650(30)" obtained by Taoka Chemical Industry Co., Ltd., and a solid content of 30% by weight Aqueous solution] 1.5 parts by weight to prepare an aqueous adhesive.

[Adhesive]

Prepare the following adhesives A and B.

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

Adhesive B: A sheet-like adhesive with a thickness of 5 μm ["NCF # L2" manufactured by Lintec Co., Ltd.].

[Transparent protective film A to E]

Prepare the following 5 kinds of protective films.

Protective film A: Cellulose triacetate film manufactured by Konicaminolta Co., Ltd.; KC2CT (thickness 20μm, in-plane retardation value at wavelength 590nm=1.2nm, retardation value in thickness direction at wavelength 590nm=1.3nm)

Protective film B: Cyclic polyolefin resin film made by Japan Zeon Co., Ltd.; ZF14-023 (thickness 23μm, in-plane retardation value at a wavelength of 590nm = 0.5nm, retardation value in the thickness direction at a wavelength of 590nm = 4.3nm )

Protective film C: cellulose triacetate film manufactured by Konicaminolta Co., Ltd.; KU2UAW (thickness 25μm, dimensional change rate D1=0.21%, dimensional change rate D2=0.20%, |D1|/|D2|=1.05)

Protective film D: Cellulose triacetate film manufactured by Konicaminolta Co., Ltd.; KU2UAW is stretched into 1.05 times film (thickness 24μm, dimensional change rate D1=0.21%, dimensional change rate) with a tenter stretcher. D2=0.38%,｜D2｜/｜D1｜=1.81)

Protective film E: cellulose triacetate film manufactured by Konicaminolta Co., Ltd.; KU2UAW is stretched to 1.15 times the film (thickness 22μm, dimensional change rate D1=0.21%, dimensional change rate D2=0.47) with a tenter stretcher. %,｜D2｜/｜D1｜=2.24)

[Optical Film]

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

(Example)

[Example 1]

Saponify the protective film A, protective film C and optical film. The protective film A, the polarizing film, and the protective film C are sequentially bonded with an aqueous adhesive to obtain a polarizing plate. Next, the adhesive B is layered on one area of the optical film to obtain an optical film with adhesive. The C surface side of the protective film of the polarizing plate obtained and the adhesive surface of the optical film with the adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were at 135° to obtain a polarizing plate. In addition, an adhesive A was laminated on the protective film A side of the obtained polarizing plate to obtain an adhesive-attached polarizing plate. The degree of polarization of the polarizer is 99.997%.

The polarizing plate was cut into a 40mm square, and attached to EAGLE XG manufactured by Corning, to make a heat resistance test evaluation sample. The sample prepared in this way was put into an oven at 85°C for 750 hours. The degree of polarization after heat resistance test is 99.983%.

[Example 2]

Perform corona treatment on one side of protective film B, and perform saponification treatment on protective film C and optical film. The corona treated surface of the protective film B, the polarizing film, and the protective film C are sequentially bonded with an aqueous adhesive to obtain a polarizing plate. Next, the adhesive B is layered on one area of the optical film to obtain an optical film with adhesive. The C surface side of the protective film of the polarizing plate obtained and the adhesive surface of the optical film with the adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were at 135° to obtain a polarizing plate. In addition, an adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain an adhesive-attached polarizing plate. The degree of polarization of the polarizer is 99.997%.

The polarizing plate was cut into a 40mm square and attached to EAGLE XG manufactured by Corning to prepare a heat-resistant evaluation sample. The sample prepared in this way was put into an oven at 85°C for 750 hours. The degree of polarization after heat resistance test is 99.983%.

[Example 3]

Perform corona treatment on one side of protective film B, and perform saponification treatment on protective film D and optical film. The corona treatment surface of the protective film B, the polarizing film, and the protective film D are sequentially bonded with an aqueous adhesive to obtain a polarizing plate. At this time, bonding was performed so that the absorption axis of the polarizing film and the extending direction of the protective film D were at 135°. Next, the adhesive B is layered on one area of the optical film to obtain an optical film with adhesive. Adhere the D surface side of the protective film of the polarizing plate obtained so that the absorption axis of the polarizing plate and the slow axis of the optical film are 135° The adhesive surface of the optical film of the agent is bonded to obtain a polarizing plate. In addition, an adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain an adhesive-attached polarizing plate. The degree of polarization of the polarizer is 99.996%.

The polarizing plate was cut into a 40mm square and attached to EAGLE XG manufactured by Corning to prepare a heat-resistant evaluation sample. The sample prepared in this way was put into an oven at 85°C for 750 hours. The degree of polarization after heat resistance test is 99.981%.

[Comparative Example 1]

Perform corona treatment on one side of the protective film B, and perform saponification treatment on the optical film. The corona treatment surface of the protective film B, the polarizing film, and the optical film are sequentially bonded with an aqueous adhesive to obtain a polarizing plate. The absorption axis of the obtained polarizer and the slow axis of the optical film were 135°. In addition, an adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain an adhesive-attached polarizing plate. The degree of polarization of the polarizer is 99.992%.

The polarizing plate was cut into a 40mm square and attached to EAGLE XG manufactured by Corning to prepare a heat-resistant evaluation sample. The sample produced in this way was put into an oven at 85°C for 750 hours. The polarization degree after the heat resistance test is 99.963%.

[Comparative Example 2]

Perform corona treatment on one side of protective film B, and perform saponification treatment on protective film E and optical film. The corona treated surface of the protective film B, the polarizing film, and the protective film E are bonded in this order with an aqueous adhesive to obtain a polarizing plate. At this time, the bonding is performed so that the absorption axis of the polarizing film and the extending direction of the protective film E are at 135°. Second, layer adhesive B on one area of the optical film to obtain Optical film with adhesive. The protective film E side of the obtained polarizer and the adhesive surface of the optical film with the adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were at 135° to obtain a polarizing plate. In addition, an adhesive A was laminated on the protective film B side of the obtained polarizing plate to obtain an adhesive-attached polarizing plate. The degree of polarization of the polarizer is 99.994%.

The polarizing plate was cut into a 40mm square and attached to EAGLE XG manufactured by Corning to prepare a heat-resistant evaluation sample. The sample prepared in this way was put into an oven at 85°C for 750 hours. The degree of polarization after heat resistance test is 99.975%.

The above results are summarized in Table 1.

(Industrial availability)

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

10‧‧‧Polarizer

21‧‧‧The direction at an angle of 45° with respect to the absorption axis of the polarizing film

22‧‧‧The direction at an angle of 135° relative to the absorption axis of the polarizing film

30‧‧‧Absorption axis of polarizing film

Claims (5)

A polarizing plate comprising in order: a stretched optical film, a first protective film, a polarizing film and an adhesive layer; wherein the angle formed by the absorption axis of the polarizing film and the slow axis of the stretched optical film About 45° or about 135°; Regarding the aforementioned first protective film, the dimension of the first protective film in the direction of 45° with respect to the absorption axis of the polarizing film after being allowed to stand at 85°C for 100 hours The rate of change is set to D1, and when the rate of dimensional change in the direction of 135° with respect to the absorption axis of the polarizing film is set to D2, the following equations (1) and (2) are satisfied: |D1|≧| When D2｜, 1≦｜D1｜/｜D2｜≦2 (1) When ｜D1｜<｜D2｜, 1<｜D2｜/｜D1｜≦2 (2). The polarizing plate described in claim 1, wherein the stretched optical film includes cyclic polyolefin resin, polycarbonate resin, cellulose resin, polyester resin, and (methyl) At least one selected from the group of acrylic resins. According to the polarizing plate described in item 1 or item 2 of the scope of patent application, the thickness of the aforementioned polarizing film is 15 μm or less. According to the polarizing plate described in item 1 or item 2 of the scope of patent application, there is a second protective film between the polarizing film and the adhesive layer. A liquid crystal panel, in which at least one side of a liquid crystal cell is provided with the polarizing plate described in any one of the first to the fourth patent applications.

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