JP2009086022A - Polarizing plate and liquid crystal display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polarizing plate with excellent dimensional stability over a long period and suitably used especially for a large screen LCD, and a liquid crystal display using the polarizing plate. <P>SOLUTION: This polarizing plate has protection films on both sides of a polarizing film and is used for a liquid crystal display device having at least a liquid crystal cell. At least one of both the side protection films on the polarizing film is heat-treated from the glass transition point temperature (Tg)-40°C to the glass transition point temperature (Tg) so that the enthalpy change (ΔH) at the glass transition point temperature (Tg) of the protection film measured by a differential scanning calorimeter (DSC) is 0.3 J/g or more. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a polarizing plate excellent in dimensional stability over a long period of time and particularly suitable for a large screen liquid crystal display and a liquid crystal display device using the polarizing plate.

Conventionally, as a polarizing plate for LCD, one in which both sides of an iodine / polyvinyl alcohol polarizing film are sandwiched between cellulose triacetate (TAC) films has been the mainstream (see Patent Document 1). The production method of this polarizing plate includes an interposing step in which an iodine / polyvinyl alcohol polarizing film is stretched in water and the polarizing film is continuously sandwiched between cellulose triacetate (TAC) films. In the sandwiching step, since the cellulose triacetate (TAC) film absorbs residual moisture in the polarizing film, the process suitability is good, and a polarizing plate having a high degree of polarization can be produced at low cost.
However, since the polarizing plate has a high hygroscopic property that is a characteristic of cellulose triacetate film, the dimensional stability is deteriorated by long-term use. This causes the problem that the iodine orientation of the polarizing plate is disturbed and light leakage occurs.
Therefore, in order to solve such problems, dye-based polarizing films that can be manufactured by a dry process have been proposed (see Patent Documents 1 to 3).
JP 2000-329936 A JP 2002-82222 A JP 2002-90528 A

However, the dye-based polarizing film has a problem that the degree of polarization is smaller than that of the iodine / polyvinyl alcohol-based polarizing film and it is difficult to achieve the high contrast required for a large-screen LCD. Accordingly, a polarizing plate that is excellent in dimensional stability over a long period of time, particularly suitable for use in large-screen LCDs, and a large-screen liquid crystal display that exhibits high viewing angle, high contrast, and high-quality display characteristics using the polarizing plate The present situation is that the necessary and sufficient performance of the apparatus has not been obtained, and the rapid development is desired.
The present invention has been made in view of the present situation, solves the above-described problems, has excellent dimensional stability over a long period of time, and is particularly suitable for use as a large-screen LCD, and the polarizing plate. An object is to provide a liquid crystal display device using a polarizing plate.

  As a result of extensive studies by the present inventors, the following knowledge was obtained. That is, among the protective films on both sides of the polarizing plate, at least one of the protective films is subjected to a glass transition temperature (Tg) between the formation of the protective film itself and the production of the polarizing plate in which the protective film is bonded to the polarizing film. ) By carrying out a heat treatment that is maintained at a temperature of −40 ° C. or higher and a glass transition temperature (Tg) or lower, the dimensional stability when used at a temperature lower than the glass transition temperature (Tg) can be remarkably improved. did it. As a result, a polarizing plate with high long-term dimensional stability was obtained, and in particular, it could be suitably used for a large screen LCD.

The present invention is based on the above findings of the present inventors, and the object is achieved by the following configuration. That is,
(1) A polarizing plate used in a liquid crystal display device having protective films on both sides of a polarizing film and having at least a liquid crystal cell,
Among the double-sided protective films in the polarizing plate, at least one of the protective films has an enthalpy change (ΔH) at the glass transition temperature (Tg) of the protective film measured by a scanning calorimeter (DSC) indicating the protective film is 0. The polarizing plate which is a protective film heat-processed in the said glass transition temperature (Tg) -40 degreeC or more and the glass transition temperature (Tg) temperature range so that it may become 3J / g or more.
(2) The polarizing plate according to (1),
The polarizing plate, wherein the at least one protective film is a protective film having a glass transition temperature (Tg) of 80 ° C. or more and a water absorption of 2% or less.
(3) The polarizing plate according to (1) or (2),
The polarizing plate, wherein the at least one protective film is a protective film selected from a norbornene film and a polyester resin film.
(4) The polarizing plate according to any one of (1) to (3),
A polarizing plate, wherein the polarizing film is an iodine / polyvinyl alcohol polarizing film stretched by adsorbing iodine to the polyvinyl alcohol film.
(5) a liquid crystal cell having at least a pair of electrodes and liquid crystal molecules sealed between the electrodes;
A liquid crystal display device comprising: the polarizing plate according to any one of (1) to (4) disposed on both surfaces of the liquid crystal cell.

  According to the present invention, a polarizing plate that is excellent in dimensional stability over a long period of time, particularly suitable for use in a large screen LCD, and has a high viewing angle, high contrast, and high image quality display characteristics using the polarizing plate. A large-screen liquid crystal display device can be provided.

Hereinafter, preferred embodiments of a polarizing plate and a liquid crystal display device according to the present invention will be described in detail with reference to the drawings.
(Polarizer)
The polarizing plate of the present invention is a polarizing plate used in a liquid crystal display device having a protective film on both sides of the polarizing film and having at least a liquid crystal cell, and at least one protective film in the polarizing plate is the protective film. The glass transition temperature (Tg) −40 ° C. or higher so that the enthalpy change (ΔH) at the glass transition temperature (Tg) of the protective film measured by a suggestive scanning calorimeter (DSC) is 0.3 J / g or higher. The polarizing plate is heat-treated in a temperature range below the glass transition temperature (Tg). Furthermore, it has another member as needed.
The temperature of the heat treatment may be Tg−40 ° C. or higher and Tg or lower, but Tg−20 ° C. or higher and Tg−1 ° C. or lower is desirable, and Tg−10 ° C. or higher and Tg−3 ° C. or lower is the most efficient. Heat treatment can be performed and is the most desirable temperature range. As a precaution at the time of heat treatment, it is necessary to carry out at a constant temperature or while gradually cooling from a high temperature to a low temperature. When the temperature is changed from a low temperature to a high temperature, the effect is small or cannot be obtained at all. Therefore, it is necessary to strictly control the temperature.
Any form of heat treatment is possible in principle, but it is desirable to carry out a roll form in which only the film is wound around a core after film formation. At that time, using a hollow core as the winding core, heating from the outside of the roll and inside the winding core while circulating hot air in a high temperature air tank, and heat-treating while heating the roll as uniformly as possible desirable.
Here, the glass transition temperature (Tg) is a deviation from the baseline when a differential scanning calorimeter (DSC) is used and a sample film 10 mg is heated at 20 ° C./min in a nitrogen stream. When an endothermic peak appears at the arithmetic average temperature of the temperature at which the temperature begins to return and the temperature at which it returns to the new pace line, or the glass transition temperature (Tg), the temperature at which the maximum value of the endothermic peak appears is defined as the glass transition temperature (Tg). .

The enthalpy change (ΔH) means the amount of heat per unit sample film weight of the endothermic peak that appears when the glass transition temperature (Tg) is measured using DSC. The larger the value of the enthalpy change (ΔH), the better, and as the heat treatment time increases, ΔH increases. Generally, the increase in ΔH varies depending on the type of polymer, but the upper limit is 3 to 5 J / g.

  Here, FIG. 1 is a schematic sectional view showing an example of the polarizing plate 10 of the present invention. An upper protective film 3 and a lower protective film 4 are attached to both surfaces of the polarizing film 1 with an adhesive layer (not shown). Although not shown in the polarizing plate 10 in FIG. 1, a liquid crystal cell of a liquid crystal display device is disposed below the lower protective film 4. An isotropic film (for example, a cellulose film) is used for the lower protective film 4 on the liquid crystal cell side, and a melt-formed film (for example, a polyester resin film) is used for the upper protective film 3 on the outermost surface side. It is done.

-Polarizing film-
The polarizing film is not particularly limited and can be appropriately selected according to the purpose. For example, a polyvinyl alcohol film, a partially formalized polyvinyl alcohol film, an ethylene / vinyl acetate copolymer partially saponified film, etc. A film formed by adsorbing iodine to a hydrophilic polymer film is suitable. Among these, an iodine / polyvinyl alcohol (PVA) polarizing film obtained by adsorbing iodine to a polyvinyl alcohol film is an extinction ratio and cost. This is particularly preferable.

The iodine / polyvinyl alcohol polarizing film is produced by casting a stock solution in which polyvinyl alcohol is dissolved in water or an organic solvent, and stretching (wet stretching) in a bath for iodine staining or stretching. And a method of treating with a boron compound after dyeing and stretching, and the like.
Examples of the solvent used in preparing the stock solution include polyhydric alcohols such as water, dimethyl sulfoxide, N-methylpyrrolidone, glycerin, ethylene glycol, propylene glycol, diethylene glycol, triethylene glycol, tetraethylene glycol, and trimethylolpropane; And amines such as ethylenediamine and diethylenetriamine; or a mixture thereof.
The stretching is preferably 2.5 times or more, more preferably 4.5 times or more in a uniaxial direction. In this case, stretching (stretching to prevent shrinkage in the width direction or more) can also be performed in the perpendicular direction. The stretching temperature is preferably in the range of 30 to 130 ° C.
The stretching of the polyvinyl alcohol film is not limited to the above-described wet stretching, and can be appropriately selected depending on the purpose. For example, other methods such as a dry stretching method of stretching before dipping in a wet bath The stretching method may be employed.

  Dyeing with iodine on the polyvinyl alcohol film, that is, adsorption of iodine, is performed by bringing the film into contact with a liquid containing iodine. Usually, an aqueous solution of iodine-potassium iodide is used. The concentration of iodine is preferably 0.1 to 2.0 g / l, and the concentration of potassium iodide is preferably 10 to 50 g / l. The mass ratio of iodine / potassium iodide is preferably 20-100. The dyeing time is preferably about 30 to 500 seconds.

-Protective film-
As the protective film, a norbornene resin film or a polyester resin film having a glass transition temperature (Tg) of 80 ° C. or more and a water absorption of 2% or less is used.

As the norbornene-based polymer, norbornene and its derivatives, tetracyclododecene and its derivatives, dicyclopentadiene and its derivatives, methanotetrahydrofluorene and its monomers as a main component of a monomer polymer, Ring-opening polymer of norbornene monomer, ring-opening copolymer of norbornene monomer and other monomer capable of ring-opening copolymerization, addition polymer of norbornene monomer, copolymerizable with norbornene monomer Examples include addition copolymers with other monomers and hydrogenated products thereof. Among these, from the viewpoints of heat resistance, mechanical strength, and the like, a ring-opening polymer hydride of a norbornene monomer is most preferable. The molecular weight of the norbornene-based polymer, the monocyclic olefin polymer, or the cyclic conjugated diene polymer is appropriately selected according to the purpose of use, but is a cyclohexane solution (a toluene solution if the polymer resin does not dissolve). Polyisoprene or polystyrene-converted weight average molecular weight measured by gel permeation chromatography, preferably 5,000 to 500,000, more preferably 8,000 to 200,000, still more preferably 10,000 to 100 When it is in the range of 1,000, the mechanical strength of the film (A) and the moldability are highly balanced and suitable. Typical polymers include those described in JP2003-327800A and JP2004233604A.

  The polyester-based resin film is not particularly limited and may be appropriately selected depending on the intended purpose.For example, a polyethylene terephthalate film, a polyethylene naphthalate film, a polybutylene terephthalate film, a polyethylene terephthalate-isophthalate copolymer film, Among these, a polyethylene terephthalate film and a polyethylene naphthalate film are particularly preferable.

  As said polyester-type resin film, what was synthesize | combined suitably may be used and a commercial item may be used. As this commercial item, Lumirror (made by Toray Industries, Inc.) etc. are mentioned suitably, for example.

  As a method for forming the transparent resin into a sheet or film, for example, either a hot melt molding method or a solution casting method can be used. The heat-melt molding method can be further classified into an extrusion molding method, a press molding method, an inflation molding method, an injection molding method, a blow molding method, a stretch molding method, etc. Among these methods, mechanical strength, surface In order to obtain a film excellent in accuracy and the like, the extrusion molding method, the inflation molding method, and the press molding method are preferable, and the extrusion molding method is most preferable.

The enthalpy change ΔH at the glass transition temperature (Tg) measured with a differential scanning calorimeter (DSC) of the norbornene resin film or polyester resin film is preferably 0.3 J / g or more. When ΔH is less than 0.3 J / g, long-term dimensional stability becomes insufficient, and light leakage may occur at the edge of the LCD screen due to changes over time.
Here, the glass transition temperature (Tg) is a deviation from the baseline when a differential scanning calorimeter (DSC) is used and a sample film 10 mg is heated at 20 ° C./min in a nitrogen stream. When an endothermic peak appears at the arithmetic average temperature of the temperature at which the temperature begins to return and the temperature at which it returns to the new pace line, or the glass transition temperature (Tg), the temperature at which the endothermic peak reaches its maximum is defined as the glass transition temperature (Tg). .

  The enthalpy change (ΔH) means the amount of heat per unit sample film weight of the endothermic peak that appears when the glass transition temperature (Tg) is measured using DSC. The larger the value of the enthalpy change (ΔH), the better, and as the heat treatment time is increased, ΔH increases. Generally, the increase in ΔH varies depending on the type of polymer, but the upper limit is 3 to 5 J / g.

As described above, the norbornene-based resin film or the polyester-based resin film has a glass transition temperature (Tg) of −40 ° C. or higher so that the enthalpy change ΔH satisfies 0.3 J / g or higher. Annealing treatment (BTA treatment, below Tg annealing treatment) is performed at a temperature equal to or lower than the temperature (Tg). Regarding the temperature of the heat treatment, Tg-20 ° C. or higher and Tg−1 ° C. or lower is more desirable, and Tg−10 ° C. or higher and Tg−3 ° C. or lower is the most desirable temperature range because heat treatment can be most efficiently performed. . As a precaution at the time of heat treatment, it is necessary to carry out at a constant temperature or while gradually cooling from a high temperature to a low temperature. When the temperature is changed from a low temperature to a high temperature, the effect is small or cannot be obtained at all. Therefore, it is necessary to strictly control the temperature.
Any form of heat treatment is possible in principle, but it is desirable to carry out a roll form in which only the film is wound around a core after film formation. At that time, using a hollow core as the winding core, heating from the outside of the roll and inside the winding core while circulating hot air in a high temperature air tank, and heat-treating while heating the roll as uniformly as possible desirable. This annealing treatment is preferably performed, for example, for 24 hours or longer, preferably 24 hours to 48 hours.

(Production method of polarizing plate)
There is no restriction | limiting in particular as a manufacturing method of the said polarizing plate, Although it can select suitably according to the objective, A longitudinal direction is made to correspond with a protective film with respect to the long polarizing film supplied with a roll form. It is preferable to stick them together.

There is no restriction | limiting in particular as said bonding method, According to the objective, it can select suitably, For example, the adhesion process through a transparent contact bonding layer, the joining process through a transparent adhesion layer, etc. are mentioned.
The transparent adhesive layer is not particularly limited and can be appropriately selected depending on the purpose. From the viewpoint of preventing changes in optical properties of the constituent members, a high-temperature process is required for curing and drying during the adhesion process. What does not require is preferable, and what does not require a long-time hardening process and drying time is more preferable.
The material for the transparent adhesive layer is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include acrylic polymers, silicone polymers, polyester resins, polyurethane resins, polyether resins, and synthetic rubbers. Among these, acrylic polymers are more preferable from the viewpoints of optical transparency, adhesive properties, weather resistance, and the like.

(Liquid crystal display device)
The liquid crystal display device of the present invention comprises at least a pair of electrodes and a liquid crystal cell having liquid crystal molecules sealed between the electrodes, and a polarizing plate disposed on both surfaces of the liquid crystal cell, and the present invention is used as the polarizing plate. The polarizing plate is used, and further has other members as necessary.

  The display mode of the liquid crystal element is not particularly limited and can be appropriately selected according to the purpose. For example, a TN (Twisted Nematic) mode, a VA (Vertical Alignment) mode, an IPS (In-Plane Switching) mode, An OCB (Optically Compensatory Bend) mode, an ECB (Electrically Controlled Birefringence) mode, and the like can be given. Among these, a TN mode is preferable because of its high contrast ratio.

Here, FIG. 2 is a schematic configuration diagram showing an example of the liquid crystal display device of the present invention.
As shown in FIG. 2, the liquid crystal display device 100 includes a liquid crystal element 130 (liquid crystal cell) disposed between a pair of an upper polarizing plate 101 and a lower polarizing plate 102 that are opposed to each other. As a protective film for either the upper polarizing plate 101 or the lower polarizing plate 102, a norbornene resin film or a polyester resin film is used.

In the liquid crystal element 130, an upper substrate 131 made of a glass substrate and a lower substrate 132 are disposed to face each other, and a liquid crystal 136 is sealed between the upper substrate 131 and the lower substrate 132. A pixel electrode (not shown), a circuit element (thin film transistor (TFT)) 144 and the like are formed on the opposing surfaces of the upper substrate 131 and the lower substrate 132. An upper alignment film 142 and a lower alignment film 143 are formed on the surfaces of the upper substrate 131 and the lower substrate 132 that are in contact with the liquid crystal 136. A rubbing process is performed on the surface of the alignment film in contact with the liquid crystal 136 in order to align the alignment direction of the liquid crystal molecules. 2, 140 represents a color filter, and 141 represents a spacer.

  There is no restriction | limiting in particular as said other structure, Although it can select suitably according to the objective, The transparent protective film which has on one side or both surfaces of the said polarizing plate, an antireflection film, an anti-glare treatment film, etc. are mentioned.

There is no restriction | limiting in particular as said antireflection film, According to the objective, it can select suitably, For example, optical interference films, such as a coating film of a fluorine-type polymer, a multilayer metal vapor deposition film, etc. are mentioned.
The anti-glare film is not particularly limited and can be appropriately selected depending on the purpose. Examples thereof include a film provided with a fine uneven structure.

  Since the liquid crystal display device of the present invention uses the polarizing plate of the present invention which has excellent dimensional stability over a long period of time and does not leak light, a large screen showing a high viewing angle, high contrast, and high image quality display characteristics. A liquid crystal display device can be provided.

Examples of the present invention will be described below, but the present invention is not limited to these examples.
(Comparative Example 1)
-Production of polarizing plate-
1. A long polyvinyl alcohol film (manufactured by Kuraray Co., Ltd., 9P75R) having a thickness of 75 μm is immersed in a dyeing bath (30 ° C.) containing iodine and potassium iodide while being continuously conveyed through a guide roll. After performing 5 times the extending | stretching process, the extending | stretching process and bridge | crosslinking process which are 5 times in total were performed in the acidic bath (60 degreeC) which added boric acid and potassium iodide. The obtained iodine / PVA polarizing film having a thickness of about 30 μm was dried in a dryer at 50 ° C. for 30 minutes. Thus, an iodine / PVA polarizing film was produced.

Next, a methylene chloride solution of triacetyl cellulose (TAC) is uniformly applied onto a mirror-finished stainless steel plate, preliminarily dried at 50 ° C. for 5 minutes, and then peeled off from the stainless steel plate, so that the film is not stressed. The film was dried at 150 ° C. for 10 minutes to prepare a protective film having a thickness of 70 μm.
The said protective film was adhere | attached on both surfaces of the obtained iodine and PVA polarizing film through the 20-micrometer-thick acrylic adhesive layer. Thus, the polarizing plate of Comparative Example 1 was produced.

Example 1
-Production of polarizing plate-
In Comparative Example 1, 100 μm norbornene-based resin film (Zeonor, Japan), which was annealed (BTA treatment, bellow Tg annealing treatment) at a thickness of 130 ° C. for 24 hours on the surface to be bonded to the liquid crystal cell of the iodine / PVA polarizing film. A polarizing plate of Example 1 was produced in the same manner as in Comparative Example 1 except that Zeon Co., Ltd., enthalpy change ΔH = 0.5 J / g) was bonded via an acrylic adhesive layer having a thickness of 20 μm.

(Example 2)
-Production of polarizing plate-
In Comparative Example 1, 100 μm norbornene-based resin film (arton, manufactured by JSR Corporation, enthalpy change ΔH = 0), which was annealed at 165 ° C. for 24 hours on the surface to be bonded to the liquid crystal cell of the iodine / PVA polarizing film. 0.5 J / g) was prepared in the same manner as in Comparative Example 1 except that the polarizing plate of Example 1 was prepared except that the adhesive layer was bonded via an acrylic adhesive layer having a thickness of 20 μm.

(Example 3)
-Production of polarizing plate-
In Example 1, except that the annealing time of the norbornene-based resin film (Zeonor, manufactured by Nippon Zeon Co., Ltd.) was 12 hours (enthalpy change ΔH = 0.3 J / g), Example 1 3 polarizing plates were produced.

Example 4
-Production of polarizing plate-
In Example 2, Example 4 was performed in the same manner as in Example 2 except that the annealing time of the norbornene-based resin film (Arton, manufactured by JSR Corporation) was 12 hours (enthalpy change ΔH = 0.3 J / g). A polarizing plate was prepared.

(Comparative Example 2)
-Production of polarizing plate-
Comparative Example as in Example 1 except that the annealing time of the norbornene-based resin film (Zeonor, manufactured by Nippon Zeon Co., Ltd.) was 5 hours (enthalpy change ΔH = 0.2 J / g). 2 polarizing plates were produced.

(Comparative Example 3)
-Production of polarizing plate-
Comparative Example 3 was performed in the same manner as in Example 2 except that the annealing time of the norbornene-based resin film (Arton, manufactured by JSR Corporation) was set to 5 hours (enthalpy change ΔH = 0.2 J / g). A polarizing plate was prepared.

  Next, about the sample which cut each polarizing plate of obtained Examples 1-3 and Comparative Examples 1-2 in the magnitude | size of length 40cm x width 50cm, it was as follows and the shrinkage rate of a peripheral part, and light The leak was evaluated. The results are shown in Table 1.

<Measurement of shrinkage at the periphery>
About each polarizing plate, the dimensional change rate before and after performing the 120-hour heating test at 80 degreeC Dry and 60 degreeC90% was calculated | required from following Numerical formula 1.

<Evaluation method of light leakage>
The light leakage due to the temporal alignment disorder of the polarizing plate is noticeable in the corner portions (A, B, D, E) in FIG. Therefore, as an evaluation method of light leakage, each polarizing plate having a length of 260 mm × width of 450 mm was pasted on a glass plate in a crossed Nicol arrangement. An acrylic adhesive was used for pasting. Next, the luminances at points A, B, D, and E (all of these are positions 1 cm inside from the corner) and C (center portion) shown in FIG. 3 are YA, YB, YC, YD, and YE. Then, the light leakage X that is the difference between the luminance of the corner portions (A, B, D, E) and the luminance of the central portion (C) can be obtained from the following formula 2, and the light leakage was evaluated according to the following criteria. . In addition, the light leakage defined here is calculated from numerical values measured after 120 hours of heating test of each polarizing plate at 80 ° C. Dry and 60 ° C. and 90%.
Here, Dry means that the treatment is performed in an atmosphere having a relative humidity in air of 10% or less.

[Formula 2]
Light leakage X = [(YA + YB + YD + YE) / 4] −YC
〔Evaluation criteria〕
○: 0 <X ≦ 0.5 cd / m ²
×: 0.5 cd / m ² <X

-Production of liquid crystal display device-
Using each polarizing plate of Examples 1 to 4 and Comparative Examples 1 and 2, liquid crystal display devices were produced by a known method (Japanese Patent Laid-Open No. 11-248921). About each obtained liquid crystal display device, when display performance was evaluated, compared with the liquid crystal display device of Comparative Examples 1-2, the liquid crystal display device of Examples 1-4 is excellent in dimensional stability over a long period of time. Since the polarizing plate of the present invention having no light leakage was used, it was confirmed that display characteristics with high viewing angle, high contrast, and high image quality were exhibited.

  The polarizing plate of the present invention is excellent in dimensional stability over a long period of time and does not cause light leakage, and is suitably used for a large-screen liquid crystal display (LCD) such as a personal computer monitor, a notebook personal computer, and a television monitor. be able to.

It is a schematic sectional drawing which shows an example of the polarizing plate of this invention. It is a schematic sectional drawing which shows an example of the liquid crystal display device of this invention. (A) And (B) is explanatory drawing for demonstrating the evaluation method of light leakage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Polarizing film 3 Upper protective film 4 Lower protective film 10 Polarizing plate 100 Liquid crystal display device 101 Upper polarizing plate 102 Lower polarizing plate 130 Liquid crystal cell 131 Upper substrate 132 Lower substrate 136 Liquid crystal 140 Color filter 141 Spacer 142 Upper alignment film 143 Lower alignment film 144 Thin film transistor (TFT)

Claims (5)

A polarizing plate used in a liquid crystal display device having a protective film on both sides of a polarizing film and having at least a liquid crystal cell,
Among the double-sided protective films in the polarizing plate, at least one of the protective films has an enthalpy change (ΔH) at the glass transition temperature (Tg) of the protective film measured by a scanning calorimeter (DSC) indicating the protective film is 0. The polarizing plate which is a protective film heat-processed in the said glass transition temperature (Tg) -40 degreeC or more and the glass transition temperature (Tg) temperature range so that it may become 3J / g or more. The polarizing plate according to claim 1,
The polarizing plate, wherein the at least one protective film is a protective film having a glass transition temperature (Tg) of 80 ° C. or more and a water absorption of 2% or less. The deflecting plate according to claim 1 or 2,
The polarizing plate, wherein the at least one protective film is a protective film selected from a norbornene film and a polyester resin film. The polarizing plate according to any one of claims 1 to 3,
A polarizing plate, wherein the polarizing film is an iodine / polyvinyl alcohol polarizing film stretched by adsorbing iodine to the polyvinyl alcohol film. A liquid crystal cell having at least a pair of electrodes and liquid crystal molecules sealed between the electrodes;
A liquid crystal display device comprising: the polarizing plate according to claim 1 disposed on both surfaces of the liquid crystal cell.

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