JP2017102426A - Polarizing plate and liquid crystal panel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polarizing plate that suppresses decrease in a polarization degree due to a displacement of an absorption axis of a polarizing film caused by dimensional changes of a stretched optical film when the polarizing plate is subjected to a heat resistance test.SOLUTION: The polarizing plate includes, in the following order, an optical film, a first adhesive layer, a polarizing film and a second adhesive layer, in which 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°. The optical film has such properties that a dimensional change rate D1 in a direction at an angle of 45° with respect to the absorption axis of the polarizing film when the optical film is left to stand in an environment at 85°C for 100 hours, and a dimensional change rate D2 in a direction at an angle of 135° with respect to the absorption axis of the polarizing film when the optical film is left to stand in an environment at 85°C for 100 hours satisfy expression (1): 2<|D1|/|D2| when |D1|>|D2| and expression (2): 2<|D2|/|D1| when |D1|<|D2|.SELECTED DRAWING: Figure 2

Description

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

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

  Several means for improving the visibility when viewing the screen through polarized sunglasses have been proposed (Patent Documents 1 to 9).

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

  As a method for improving visibility when viewing the screen through polarized sunglasses, linearly polarized light emitted from a polarizing plate arranged on the viewing side of an image display element such as a liquid crystal cell is elliptical (or circular). In order to convert it into polarized light, a method of arranging a retardation plate (for example, a λ / 4 wavelength plate) on the viewing side of the polarizing plate (Patent Documents 1 to 9) is employed.

  However, such a retardation plate has been stretched and is often laminated directly on the polarizing film via an adhesive layer. In addition, 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 °). There has been a problem that the absorption axis of the polarizing film is locally changed by the dimensional change of the angle, and the degree of polarization is lowered.

[1] An optical film, a first pressure-sensitive adhesive layer, a polarizing film, and a second pressure-sensitive adhesive layer are included in this order,
The angle formed between the absorption axis of the polarizing film and the slow axis of the optical film is about 45 ° or about 135 °,
When the optical film is left to stand in an environment of 85 ° C. for 100 hours, when it is left to stand in an environment of 85 ° C. for 100 hours and a dimensional change rate D1 in the direction of 45 ° with respect to the absorption axis of the polarizing film. A polarizing plate in which the dimensional change rate D2 in the direction of 135 ° with respect to the absorption axis of the polarizing film satisfies the following formulas (1) and (2).

In the case of | D1 |> | D2 |, 2 <| D1 | / | D2 | (1)
When | D1 | <| D2 |, 2 <| D2 | / | D1 | (2)

[2] The polarizing plate according to [1], wherein the optical film includes at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin.
[3] The polarizing plate according to [1] or [2], 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 including a protective film between the polarizing film and the second pressure-sensitive adhesive layer.
[5] A liquid crystal panel in which the polarizing plate according to any one of [1] to [4] is laminated on at least one surface of the liquid crystal cell via the second pressure-sensitive adhesive layer.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which can suppress the polarization degree fall by the shift | offset | difference of the absorption axis of the polarizing film caused by the dimensional change of an optical film at the time of a heat test can be provided.

It is an example of the cross-sectional schematic diagram which shows the laminated constitution of the polarizing plate which concerns on this invention. It is an example of the top view which shows the relationship of the axial direction in the polarizing plate of this invention.

  With reference to FIG. 1, the layer structure of the polarizing plate 10 concerning this invention is demonstrated. The polarizing plate of the present invention is preferably configured by laminating the optical film 11, the first pressure-sensitive adhesive layer 12, the polarizing film 14, and the second pressure-sensitive 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 approximately 45 ° or approximately 135 °. It is also useful to form the surface treatment layer 20 on the surface of the optical film 11 opposite to the bonding surface with the polarizing film.

  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.

  The polarizing film 14 preferably has a thickness of 15 μm or less.

  Moreover, according to this invention, the polarizing plate 10 which has the protective film 15 further between the polarizing film 14 and the 2nd adhesive 16 is also provided.

  The present invention also provides a liquid crystal panel in which the polarizing plate 10 is laminated on at least one of the liquid crystal cells via the second pressure-sensitive adhesive layer 16.

  Hereafter, the member which comprises the liquid crystal display device of this invention is demonstrated in detail.

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

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

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

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

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

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

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

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

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

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

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

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

  It is also preferable to reduce the shrinkage force of the polarizing film itself from the viewpoint of suppressing a decrease in the degree of polarization under a heat resistance test. In order to keep the contraction force of the polarizing film 14 low, 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 in that good optical properties can be imparted.

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

The optical film 11 has 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
It is preferable that the film satisfies the above. In the formula, R _e (590), R _e (450), R _e (550), and R _e (630) represent in-plane retardation values at measurement wavelengths of 590 nm, 450 nm, 550 nm, and 630 nm, respectively, and R _th ( 590) represents a thickness direction retardation value at a measurement wavelength of 590 nm. These in-plane retardation value and thickness direction retardation value are measured in an environment of a temperature of 23 ° C. and a relative humidity of 55%.

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

  In a liquid crystal display in which the optical film 11 showing the retardation characteristics and wavelength dispersion characteristics of the above formulas (5) to (8) is arranged on the viewing side, the screen is viewed from various directions (azimuth angle and polar angle) through polarized sunglasses. The color change at the time can be effectively suppressed, and the visibility of the liquid crystal display can be improved. On the other hand, when any one or more of the above formulas (5) to (8) are not satisfied, the suppression of the color change may be insufficient.

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

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

  It is easy to give the phase difference characteristics and wavelength dispersion characteristics of the above formulas (5) to (8), and since the moisture permeability is relatively low, the moisture resistance and heat and moisture resistance of the optical laminate can be improved. Preferably, the optical film contains a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, a (meth) acrylic resin, or two or more thereof, and the resin component is selected from these 1 or More preferably, it consists of 2 or more.

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

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

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

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

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

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

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

  The optical film 11 can be produced by stretching a film containing the thermoplastic resin. Examples of the stretching treatment include uniaxial stretching and biaxial stretching. Examples of the stretching direction include a machine flow direction (MD) of an unstretched film, a direction perpendicular to the machine flow direction (TD), and a direction oblique to the machine flow direction (MD). Biaxial stretching may be simultaneous biaxial stretching in which stretching is performed simultaneously in two stretching directions, or sequential biaxial stretching in which stretching is performed in a predetermined direction and then stretching in another direction. For the stretching process, for example, two or more pairs of nip rolls with increased peripheral speed on the outlet side are used to stretch in the longitudinal direction (machine flow direction: MD), or the both ends of the unstretched film are gripped with a chuck and machine flow is performed. It can be performed by spreading in a direction (TD) orthogonal to the direction. At this time, the retardation value and the wavelength dispersion can be controlled within the ranges of the above formulas (5) to (6) by adjusting the thickness of the film or adjusting the stretch ratio. Moreover, it is possible to control the wavelength dispersion value within the range of the above formulas (7) to (8) by adding a wavelength dispersion adjusting agent to the resin.

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

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

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

In the present invention, the optical film 11 has an absorption axis of the polarizing film and a dimensional change rate D1 in the direction of 45 ° and a polarizing film when left in an environment of 85 ° C. for 100 hours in order to give desired retardation characteristics. The absorption axis and the dimensional change rate D2 in the direction of 135 ° satisfy the following formula. When the polarizing film 14 is viewed from the stretched optical film 11, the counterclockwise angle is positive.

In the case of | D1 |> | D2 |, 2 <| D1 | / | D2 | (1)
When | D1 | <| D2 |, 2 <| D2 | / | D1 | (2)

  D1 and D2 in the above formulas (1) to (2) can be measured as follows with reference to FIG. FIG. 2A is an example of a plan view showing the absorption axis of the polarizing film, the direction of 45 ° with respect to the absorption axis, and the direction of 135 ° with respect to the absorption axis in the polarizing plate of the present invention. As described above, it is preferable that the slow axis of the optical film substantially coincides with the direction 31 or the direction 32.

First, as shown in FIG. 2B, the optical film is cut so as to have a size of 100 mm in the direction of 45 ° and 100 mm in the direction of 135 ° with respect to the absorption axis of the polarizing film. The cut optical film 40 is allowed to stand in an environment having a temperature of 23 ° C. and a humidity of 55% for one day. The dimension (L0 (45)) in the direction of 45 ° (direction 31) with respect to the absorption axis of the polarizing film and the polarizing film The dimension (L0 (135)) in the direction (direction 32) of 135 ° with respect to the absorption axis is measured. Next, the dimension in the direction 31 (L1 (45)) and the dimension in the direction 32 (L1 (135)) after measuring 100 hours in an environment of 85 ° C. are measured. Based on the result, 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 thermoplastic resin. Among the thermoplastic resins, it is preferable to include a cellulose-based resin such as a cellulose ester-based resin such as cellulose triacetate or cellulose diacetate because it is easy to obtain a film satisfying the above formulas (1) to (2).

  The stretching method may be simultaneous biaxial stretching or sequential biaxial stretching, but the film produced by simultaneous biaxial stretching is a film satisfying the above formulas (1) to (2). It is preferable because it is easy to obtain. The method of simultaneous biaxial stretching is not particularly limited, but both ends of the unstretched film are gripped by chucks, the feed rates of the chucks at both ends are differentiated, and further spread in a direction (TD) perpendicular to the machine flow direction. Can be manufactured. Simultaneous biaxial stretching includes stretching in one direction and contracting the other tension by relaxing.

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

[Protective film 15]
In particular, the protective film 15 is preferably made of a material having excellent transparency, mechanical strength, thermal stability, moisture shielding properties, and the like. The protective film 15 preferably contains a cellulose resin, a polyolefin resin, or an acrylic resin because the retardation value is easily controlled and easily available. The polyolefin resin here includes a chain polyolefin resin and a cyclic polyolefin resin.

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

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

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

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

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

[Adhesive layer]
The polarizing film and the protective film can be bonded with an adhesive or a pressure-sensitive adhesive.

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

  In addition, the curable adhesive composition may have other additives such as ion trapping agents, antioxidants, chain transfer agents, sensitizers, tackifiers, thermoplastic resins, fillers, as long as the adhesiveness is not impaired. Agents, flow modifiers, plasticizers, antifoaming agents, and the like. Examples of the ion trapping agent include inorganic compounds including powdered bismuth-based, antimony-based, magnesium-based, aluminum-based, calcium-based, titanium-based, and mixed systems thereof. Examples of the antioxidant include And hindered phenolic antioxidants.

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

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

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

  When the adhesive composition is cured by heat, it can be heated by a generally known method. Usually, heating is performed at a temperature higher than the temperature at which the thermal cationic polymerization initiator compounded in the curable adhesive composition generates cationic species and Lewis acid, 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 to laminate the polarizing film 14 and the optical film 11 directly via the first pressure-sensitive adhesive layer 12. By laminating the polarizing film 14 and the optical film 11 via the pressure-sensitive adhesive layer, stress applied to the polarizing film due to an anisotropic dimensional change of the optical film 11 when a heat resistance test is performed can be relaxed.

[First adhesive layer 12]
The first pressure-sensitive adhesive layer 12 used for laminating the polarizing film 14 and the optical film 11 is excellent in optical transparency and adhesive properties including appropriate wettability, cohesiveness, adhesiveness and the like. However, it is preferable to have excellent durability. Specifically, the pressure-sensitive adhesive forming the first pressure-sensitive adhesive layer 12 is preferably a pressure-sensitive adhesive containing an acrylic resin (acrylic pressure-sensitive adhesive).

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

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

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

  The first pressure-sensitive adhesive layer 12 is prepared by preparing a pressure-sensitive adhesive composition in which the pressure-sensitive adhesive component as described above is dissolved in an organic solvent and bonding it to any one of the bonding surfaces (polarizing film or optical film). Apply the above-mentioned pressure-sensitive adhesive composition on the release treatment surface of the base film made of a resin film that has been subjected to a release treatment by applying directly and removing the solvent by drying, and removing the solvent by drying. It can be formed by forming a pressure-sensitive adhesive layer, sticking it to one of the bonding surfaces (polarizing film or optical film), and transferring the pressure-sensitive adhesive. When the first pressure-sensitive adhesive layer 12 is formed by the former direct coating method, a resin film (also called a separator) that has been subjected to a release treatment is bonded to the surface, and the surface of the pressure-sensitive adhesive layer is temporarily used until use. It is customary to protect the wear. The latter transfer method is often employed from the viewpoint of the handleability of the pressure-sensitive adhesive composition, which is an organic solvent solution. In this case, the release-treated substrate used for forming the first pressure-sensitive adhesive layer first is used. It is also advantageous in that the material film can be used as a separator after being attached to the polarizing plate.

  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 modulus of the pressure-sensitive adhesive at 80 ° C. is preferably 5 MPa or less, preferably 1 MPa or less. Preferably there is.

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

[Second adhesive layer 16]
The pressure-sensitive adhesive layer 16 can be used as a pressure-sensitive adhesive layer for bonding the polarizing plate 10 to a liquid crystal cell. The 2nd adhesive layer 16 formed in the surface on the opposite side to the bonding surface with the polarizing film 14 in the protective film 15 is excellent in optical transparency, moderate wettability, cohesiveness, adhesiveness, etc. However, those having excellent durability and the like are preferably used. Specifically, as the pressure-sensitive adhesive forming the second pressure-sensitive adhesive layer 16, a pressure-sensitive adhesive (acrylic pressure-sensitive adhesive) containing an acrylic resin is preferably used. Specifically, the same adhesive as the first adhesive 12 may be used.

  Similar to the first pressure-sensitive adhesive layer 12, the second pressure-sensitive adhesive layer 16 may contain various additives. In particular, the second pressure-sensitive adhesive layer 16 preferably contains an antistatic agent. In general, when attaching a polarizing plate to a liquid crystal cell via an adhesive layer, the surface protective film (separator) that has been temporarily protected by covering the adhesive layer is peeled off and then attached to the liquid crystal cell. The static electricity generated when the surface protective film is peeled off causes the alignment failure of the liquid crystal in the liquid crystal cell, and this phenomenon may cause the display failure of the liquid crystal display device. As a means for reducing or preventing the generation of static electricity, it is effective to add an antistatic agent to the adhesive.

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

[Production method of polarizing plate]
Although it does not restrict | limit especially as a method to manufacture the polarizing plate of this invention, For example, with the adhesive which laminated | stacked the polarizing film which laminated | stacked the polarizing film 14 and the protective film 15, and the optical film 11 and the 1st adhesive layer 12 The polarizing plate 10 is obtained by bonding an optical film with a roll-to-roll through the first pressure-sensitive adhesive layer 12. Furthermore, a polarizing plate with an adhesive is obtained by forming the second adhesive layer 16 on the protective film 15. The polarizing plate with the pressure-sensitive adhesive can be bonded to the liquid crystal cell via the second pressure-sensitive adhesive layer 16.

[Liquid Crystal Cell]
The liquid crystal cell has two cell substrates and a liquid crystal layer sandwiched between the substrates. In general, the cell substrate is often made of glass, but may 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 types employed in this field.

[LCD panel]
A liquid crystal panel can be produced by bonding the polarizing plate 10 to the liquid crystal cell via the second pressure-sensitive adhesive layer 16. Usually, although a polarizing plate is bonded on both surfaces of a liquid crystal cell, the polarizing plate of this invention is used suitably for the visual recognition side of a liquid crystal display device.

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

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

(2) Measurement of in-plane retardation and thickness direction retardation:
In-plane retardation and thickness direction retardation at a predetermined wavelength at a temperature of 23 ° C. using a phase difference meter “KOBRA (registered trademark) -WPR” based on the parallel Nicol rotation method manufactured by Oji Scientific Instruments Co., Ltd. Was measured.
(3) Measurement of polarization degree and single transmittance of polarizing plate:
The measurement was performed using a spectrophotometer with an integrating sphere [“V7100” manufactured by JASCO Corporation, 2-degree field of view; C light source].

(4) Measuring method of dimensional change rate of film With respect to the dimensional change rate D1 in the direction of 45 ° with respect to the absorption axis of the polarizing film and the absorption axis of the polarizing film when the film is allowed to stand for 100 hours in an environment of 85 ° C. The dimensional change rate D2 in the direction of 135 ° was measured as follows using a two-dimensional measuring instrument “NEXIV VMR-12072” manufactured by Nikon Corporation. First, the optical film was cut so as to have 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 optical film is allowed to stand for 1 day in an environment of a temperature of 23 ° C. and a humidity of 55%, and the dimension in the direction of 45 ° (L0 (45)) with respect to the absorption axis of the polarizing film and 135 with respect to the absorption axis of the polarizing film. The dimension in the direction (L0 (135)) was measured. Next, it is allowed to stand in an environment of 85 ° C. for 100 hours, and after being allowed to stand in a high temperature environment, the dimension in the direction of 45 ° (L1 (45)) with respect to the absorption axis of the polarizing film and On the other hand, the dimension in the direction of 135 ° (L1 (135)) was measured. Based on the results, dimensional change rates D1 (%) and D2 (%) were determined from 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)

(Measurement method of storage modulus)
The storage elastic modulus (G ′) of the pressure-sensitive adhesive was prepared by preparing a cylindrical test piece having a diameter of 8 mm × thickness of 1 mm made of a pressure-sensitive adhesive to be measured, and measuring a dynamic viscoelasticity measuring device (Dynamic Analyzer RDA II: manufactured by REOMETRIC Corporation) ), The initial strain was set to 1N by the torsional shearing method with a frequency of 1 Hz, and the measurement was performed under the condition of a temperature of 80 ° C.

[Production Example 1] Production of polarizing film A polyvinyl alcohol film having a thickness of 20 µm (average polymerization degree of about 2400, saponification degree of 99.9 mol% or more) is uniaxially stretched by about 4 times by dry stretching, and further maintained in a tension state. The sample was immersed in pure water at 40 ° C. for 40 seconds, and then immersed in an aqueous solution having an iodine / potassium iodide / water weight ratio of 0.052 / 5.7 / 100 at 28 ° C. for 30 seconds to perform a dyeing treatment. It was. Thereafter, it was immersed in an aqueous solution having a weight ratio of potassium iodide / boric acid / water of 11.0 / 6.2 / 100 at 70 ° C. for 120 seconds. Subsequently, after washing with pure water at 8 ° C. for 15 seconds, the film is dried at 60 ° C. for 50 seconds and then at 75 ° C. for 20 seconds while being held at a tension of 300 N, and iodine is adsorbed and oriented on the polyvinyl alcohol film. A polarizing film having a thickness of 7 μm was obtained.

[Production Example 2] Preparation of water-based adhesive 3 parts by weight of carboxyl group-modified polyvinyl alcohol [trade name “KL-318” obtained from Kuraray Co., Ltd.] was dissolved in 100 parts by weight of water, and a water-soluble epoxy was dissolved in the aqueous solution. 1.5 parts by weight of a resin-based polyamide epoxy additive [trade name “Smileise Resin (registered trademark) 650 (30)” obtained from Taoka Chemical Co., Ltd., aqueous solution with a solid content of 30 wt%] was added. A water-based adhesive was prepared.

[Adhesive]
Adhesive A: Sheet-like adhesive having a thickness of 25 μm [“P-3132” manufactured by Lintec Corporation]
Adhesive B: Sheet-shaped adhesive with a thickness of 15 μm [“P-0082” manufactured by LINTEC Corporation, storage elastic modulus at 80 ° C. is 0.04 MPa]
Adhesive C: Sheet-like adhesive having a thickness of 5 μm [“NCF # L2” manufactured by Lintec Corporation, storage elastic modulus at 80 ° C. is 0.2 MPa]
Adhesive D: Sheet-shaped adhesive having a thickness of 25 μm [“NCF # E4” manufactured by Lintec Corporation, storage elastic modulus at 80 ° C. is 0.8 MPa]
Adhesive E: Sheet-like adhesive having a thickness of 25 μm [Lintec Corporation's “# E5” processed into a sheet-like adhesive, storage elastic modulus at 80 ° C. is 1.3 MPa]
Prepared.

[Protective film]
The following protective films were prepared.

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

[Optical film]
Optical film: Triacetyl cellulose film manufactured by Konica Minolta 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, Rth (590) / Re (590) = 0.71, Re (450) / Re (550) = 0.96, Re (630) / Re (550) = 1.02, dimensional change rate D1 = 0.08%, dimensional change rate D2 = 0.26%, | D2 | / | D1 | = 3.25).

[Example 1]
One side of the protective film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The corona-treated surface of the protective film and the polarizing film were bonded with an aqueous adhesive to obtain a polarizing plate with a single-side protective film. Next, the adhesive B was laminated on one surface of the optical film to obtain an optical film with an adhesive. The polarizing film side of the obtained polarizing plate with a single-sided protective film and the adhesive surface of the optical film with an adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were 45 °. Got. Furthermore, the adhesive A was laminated | stacked on the protective film side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained. The polarization degree of the polarizing plate was 99.993%.

  The polarizing plate thus prepared was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning 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. The degree of polarization after the heat test was 99.975%.

[Example 2]
One side of the protective film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The corona-treated surface of the protective film and the polarizing film were bonded with an aqueous adhesive to obtain a polarizing plate with a single-side protective film. Next, the adhesive C was laminated on one surface of the optical film to obtain an optical film with an adhesive. The polarizing film side of the obtained polarizing plate with a single-sided protective film and the adhesive surface of the optical film with an adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were 45 °. Got. Furthermore, the adhesive A was laminated | stacked on the protective film side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained. The polarization degree of the polarizing plate was 99.997%.

  The polarizing plate thus prepared was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning 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. The degree of polarization after the heat test was 99.974%.

[Example 3]
One side of the protective film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The corona-treated surface of the protective film and the polarizing film were bonded with an aqueous adhesive to obtain a polarizing plate with a single-side protective film. Next, an adhesive D was laminated on one surface of the optical film to obtain an optical film with an adhesive. The polarizing film side of the obtained polarizing plate with a single-sided protective film and the adhesive surface of the optical film with an adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were 45 °. Got. Furthermore, the adhesive A was laminated | stacked on the protective film side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained. The polarization degree of the polarizing plate was 99.996%.

  The polarizing plate thus prepared was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning 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. The degree of polarization after the heat test was 99.975%.

[Example 4]
One side of the protective film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The corona-treated surface of the protective film and the polarizing film were bonded with an aqueous adhesive to obtain a polarizing plate with a single-side protective film. Next, the adhesive E was laminated | stacked on one surface of the optical film, and the optical film with an adhesive was obtained. The polarizing film side of the obtained polarizing plate with a single-sided protective film and the adhesive surface of the optical film with an adhesive were bonded so that the absorption axis of the polarizing plate and the slow axis of the optical film were 45 °. Got. Furthermore, the adhesive A was laminated | stacked on the protective film side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained. The polarization degree of the polarizing plate was 99.994%.

  The polarizing plate thus prepared was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning 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. The degree of polarization after the heat test was 99.973%.

[Comparative Example 1]
One side of the protective film was subjected to corona treatment, and the optical film was subjected to saponification treatment. The corona-treated surface of the protective film, the polarizing film, and the optical film were bonded in this order with an aqueous adhesive to obtain a polarizing plate. The absorption axis of the obtained polarizing plate and the slow axis of the optical film were set to 45 °. Furthermore, the adhesive A was laminated | stacked on the protective film B side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained. The polarization degree of the polarizing plate was 99.995%.

  The polarizing plate thus prepared was cut into a 40 mm square, and bonded to Eagle XG manufactured by Corning 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. The degree of polarization after the heat test was 99.962%.

  The above results are summarized in Table 1.

  ADVANTAGE OF THE INVENTION According to this invention, the polarizing plate which can suppress the polarization degree fall by the shift | offset | difference of the absorption axis of the polarizing film caused by the dimensional change of an optical film at the time of a heat test can be provided.

DESCRIPTION OF SYMBOLS 10 Polarizing 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 31 of a polarizing film The direction of 45 degrees with respect to the absorption axis of a polarizing film 32 Direction of 135 ° to the absorption axis of the polarizing film 33 45 °
34 135 °
40 Cut optical film 11

Claims (5)

Including an optical film, a first pressure-sensitive adhesive layer, a polarizing film and a second pressure-sensitive adhesive layer in this order,
The angle formed between the absorption axis of the polarizing film and the slow axis of the optical film is about 45 ° or about 135 °,
When the optical film is left to stand in an environment of 85 ° C. for 100 hours, when it is left to stand in an environment of 85 ° C. for 100 hours and a dimensional change rate D1 in the direction of 45 ° with respect to the absorption axis of the polarizing film. A polarizing plate in which the dimensional change rate D2 in the direction of 135 ° with respect to the absorption axis of the polarizing film satisfies the following formulas (1) and (2).

In the case of | D1 |> | D2 |, 2 <| D1 | / | D2 | (1)
When | D1 | <| D2 |, 2 <| D2 | / | D1 | (2)
  The polarizing plate according to claim 1, wherein the optical film includes at least one selected from the group consisting of a cyclic polyolefin resin, a polycarbonate resin, a cellulose resin, a polyester resin, and a (meth) acrylic resin.   The polarizing plate according to claim 1, wherein the polarizing film has a thickness of 15 μm or less.   The polarizing plate according to claim 1, further comprising a protective film between the polarizing film and the second pressure-sensitive adhesive layer. A liquid crystal panel in which the polarizing plate according to claim 1 is laminated on at least one surface of a liquid crystal cell via the second pressure-sensitive adhesive layer.

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