KR20080053868A - Polarizing plate and liquid crystal display device having the same - Google Patents

Abstract

A polarizing panel and an LCD(Liquid Crystal Display) having the same are provided to minimize the reduction of brightness at the white display at the parallel nicol state and to reduce a light leakage at the rectangular nicol state. A transparent protection layer(3) is stacked on one or more surface of a polarizing piece(1) through an adhesive layers(2). A viscosity layer(4) is formed at any one of the transparent protection layer. An exfoliation film(5) is attached on the viscosity layer in order to prevent the contamination. A surface treatment coating layer(6) is formed at the uppermost polarizing panel having anti-static and low-reflection function and the like. A protection film(7) is attached on the polarizing panel in order to protect the polarizing panel. The polarizing panel includes a long wavelength visible ray absorption agent with the maximum absorption peak at the wavelength area above 650nm. At the rectangular nicol state, the transmission rate at 750nm is below 3% and the transmission rate at 780nm is below 15%. The long wavelength visible ray absorption agent is coated to any one of the transparent protection layer.

Description

Polarizing plate and liquid crystal display device having the same

1 is a view showing an absorption spectrum according to the composition of the iodine compound used for staining of the polarizer,

2 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention;

3 is a diagram showing the orthogonal transmittance according to the wavelength of Example 1 and Comparative Example 1 of the present invention.

Explanation of symbols on the main parts of the drawings

1: polarizer 2: adhesive layer

3: transparent protective layer 4: adhesive layer

5: release film 6: surface treatment coating layer

7: protective film

The present invention relates to a polarizing plate capable of manufacturing a liquid crystal display device having excellent contrast and a liquid crystal display device having the same.

Recently, as the liquid crystal display is rapidly expanded for television use, high brightness and high viewing angle are required, and a wide viewing angle such as VA (vertical alignment) or IPS (planar alignment) is mainly used. The luminance deteriorated as the viewing angle is enlarged is compensated by raising the luminance of the backlight. In this method, the light leakage in the black display is also increased so that the contrast ratio, which is the contrast ratio, is often lowered, which leads to deterioration of image quality.

On the other hand, a dichroic polarizing plate made by adsorbing and orienting a dichroic substance such as iodine in a substrate such as polyvinyl alcohol is widely used. The dichroic polarizing plate uses polarized light obtained by absorbing the dichroic substance. Even if the light is partially polarized and placed in an orthogonal nicol state, there is a problem in that light leakage occurs in black display.

This light leakage causes the contrast ratio to be lowered. A method of reducing the light leakage by increasing the light absorption amount by increasing the adsorption concentration of the dichroic substance may be used, but in this case, the brightness of the white display is significantly lowered to improve the contrast ratio. This has the disadvantage of becoming difficult.

In some cases, a third polarizing plate may be introduced as a method for improving the contrast ratio. However, in the case of white display, the brightness is markedly reduced, and the thickness of the liquid crystal display is increased, which hinders the advantages of the lightweight and thin liquid crystal display. There are disadvantages.

1 is the UV spectrum of a PVA polarizer stained with an iodine compound. The iodine compound in the aqueous solution is composed of -monovalent iodine compound, -trivalent iodine compound, and -5-valent iodine compound. Of these, the -trivalent iodine compound shows the most uniform absorption in the visible light region (380 ~ 780nm), so when preparing the polarizer, the -trivalent iodine compound is mainly used by dyeing the polyvinyl alcohol (PVA) stretched film. The polarizer, which is mainly dyed with -trivalent iodine compound, has a constant absorption in the 380 ~ 700nm wavelength range and performs the original function of the polarizer, but light absorption occurs due to the rapid decrease in the absorption in the 700 ~ 780nm wavelength range. Done. Therefore, there is a problem in that the contrast ratio of the liquid crystal display device having the same decreases and becomes reddish.

Disclosure of Invention The present invention has been made to solve the above problems, and an object of the present invention is to provide a polarizing plate having excellent brightness in white display in a parallel nicol state and low light leakage in an orthogonal nicol state and an excellent liquid crystal display device using the same.

The present invention for achieving the above object,

A polarizer comprising a polarizer, a protective layer laminated on any one or more surfaces of the polarizer through an adhesive layer, and a pressure-sensitive adhesive layer laminated on any one surface of the protective layer, wherein the long wavelength visible light has a maximum absorption peak in a wavelength region of 650 nm or more. It provides a polarizing plate comprising an absorbent.

In addition, in the orthogonal nicol state, a transmittance at 750 nm is 3% or less, and a transmittance at 780 nm is 15% or less.

In addition, the long wavelength visible light absorbent provides a polarizing plate, characterized in that contained in the adhesive layer or adhesive layer.

In addition, the long wavelength visible light absorbing agent provides a polarizing plate, characterized in that the coating on any one or more sides of the transparent protective layer.

In addition, the long-wavelength visible light absorbing agent, anthraquinone, dioxadine, triphenodithiazine, phenanthrene, cyanine, phthalocyanine ) Merocyanine (merocyanine), pyrylium (pyrylium), xanthine (xanthine), triphenylmethane (triphenylmethane), croconium (croconium), azo (azo), indigoid (indigoid), poly It provides a polarizing plate, characterized in that at least one selected from the group consisting of methine (polymethine), azulene (azulene), squaria-based (squarium), sulfide-based (sulfide), metal dithiolate-based (metal dithiolate) dye do.

The present invention also provides a liquid crystal display device provided with a polarizing plate.

In addition, there is provided a liquid crystal display device having a contrast ratio of 1300: 1 or more.

Hereinafter, the present invention will be described in more detail with reference to the accompanying drawings and examples. The following detailed description is for the exemplary embodiment of the present invention, and the present invention is not limited thereto.

According to the present invention, a polarizer comprising a polarizer, a protective layer laminated on at least one surface of the polarizer through an adhesive layer, and an adhesive layer laminated on any one surface of the protective layer, has a maximum absorption peak in a wavelength region of 650 nm or more. Provided is a polarizing plate comprising a long wavelength visible light absorbent having.

The long wavelength visible light absorbent may be included in at least one or more of the components of the polarizing plate, and the component is not limited as long as the contrast can be increased by including the long wavelength visible light absorbent.

The long-wavelength visible light absorber relatively absorbs visible light having a wavelength of 650 nm or more, preferably 700 nm or more, thereby absorbing light in a region of 700 to 780 nm that the iodine compound is relatively absent in the polarizer, thereby absorbing light in orthogonal nicotine. It is to provide a polarizing plate with improved contrast.

2 is a cross-sectional view of a polarizing plate according to an embodiment of the present invention. It may be composed of a polarizer 1, a transparent protective layer 3 adhered to the polarizer with an adhesive layer (2). In addition, an adhesive layer 4 may be further included in the transparent protective layer, and the release film 5 may be attached to prevent contamination of the adhesive layer 4. In addition, a surface treatment coating layer 6 such as antistatic, antiglare treatment, high hardness treatment, low reflection treatment, and the like may be formed on the front polarizer as necessary. In addition, a protective film 7 may be attached to protect the surface treatment coating or the polarizing plate. The long wavelength visible light absorber may be included in at least one of the above components.

Hereinafter, the layers constituting the polarizing plate will be described in detail.

[Polarizer]

The polarizer is usually a step of uniaxially stretching a polyvinyl alcohol-based resin film, a step of dyeing the polyvinyl alcohol-based resin film with a dichroic dye to adsorb the dichroic dye, and a polyvinyl alcohol-based resin film adsorbed on the dichroic dye. It manufactures through the process of processing with aqueous boric acid solution, and the process of washing with water after the process by this boric acid aqueous solution.

Uniaxial stretching may be performed before dyeing, simultaneously with dyeing, or after dyeing. When performing uniaxial stretching after dyeing, this uniaxial stretching may be performed before boric acid treatment, or may be performed during boric acid treatment. Of course, it is also possible to uniaxially stretch in these several steps. In uniaxial stretching, it may extend | stretch uniaxially between rolls with different circumferential speeds, and may extend | stretch uniaxially using a thermal roll. Moreover, it may be dry stretching, such as extending | stretching in air | atmosphere, or it may be wet extending | stretching extending | stretching in the state swollen with a solvent. A draw ratio is about 3 to 8 times normally.

In order to dye a polyvinyl alcohol-type resin film with a dichroic dye, a polyvinyl alcohol-type resin film can be immersed in the aqueous solution containing a dichroic dye, for example. As a dichroic dye, an iodine and a dichroic dye are used specifically. In addition, it is preferable that the polyvinyl alcohol-based resin film be immersed in water before the dyeing treatment.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing iodine and potassium iodide is employ | adopted normally. The content of iodine in this aqueous solution is usually about 0.01 to 1 part by weight per 100 parts by weight of water, and the content of potassium iodide is usually about 0.5 to 20 parts by weight per 100 parts by weight of water. The temperature of the aqueous solution used for dyeing is about 20-40 degreeC normally, and the immersion time (dyeing time) in this aqueous solution is about 20-1,800 second normally.

On the other hand, when using a dichroic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type resin film in the aqueous solution containing water-soluble dichroic dye is employ | adopted normally. The content of the dichroic dye 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 1x10 ^{-4 to 10} parts by weight per 100 parts by weight of water, preferably 1x10. ^{-3 to 1} parts by weight. This aqueous solution may contain inorganic salts, such as sodium sulfate, as a dyeing adjuvant. The temperature of the dye aqueous solution used for dyeing is usually about 20 to 80, and the immersion time (dyeing time) in the aqueous solution is usually about 10 to 1,800 seconds.

The boric acid treatment after dyeing with a dichroic dye is performed by immersing the dyed polyvinyl alcohol-type resin film in boric acid containing aqueous solution. The amount of boric acid in boric acid containing aqueous solution is about 2-15 weight part normally per 100 weight part of water, Preferably it is about 5-12 weight part. When iodine is used as a dichroic dye, it is preferable that this boric acid containing aqueous solution contains potassium iodide. The amount of potassium iodide in boric acid containing aqueous solution is about 0.1-15 weight part normally per 100 weight part of water, Preferably it is about 5-12 weight part. Immersion time in boric acid containing aqueous solution is about 60 to 1,200 second normally, Preferably it is about 150 to 600 second, More preferably, it is about 200 to 400 second. The temperature of boric acid containing aqueous solution is 50 degreeC or more normally, Preferably it is 50-85 degreeC, More preferably, it is 60-80 degreeC.

The polyvinyl alcohol-based resin film after boric acid treatment is usually washed with water. The water washing process is performed by immersing the polyvinyl alcohol-type resin film processed by boric acid, for example in water. The temperature of the water in a water washing process is about 5-40 degreeC normally, and immersion time is about 1-120 second normally. After water washing, a drying process is performed and a polarizing plate is obtained. The drying treatment is usually 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 time of a drying process is about 60 to 600 second normally, Preferably it is about 120 to 600 second. In this way, the polyvinyl alcohol-based resin film is subjected to uniaxial stretching, dyeing with a dichroic dye, and boric acid treatment to obtain a polarizer. The thickness of this polarizer is about 5-40 micrometers.

[Transparent transparent layer]

The protective transparent layer includes all of the transparent protective layer, a protective transparent film can be used. As the protective transparent film, any film can be used as long as it is a transparent plastic film. For example, cycloolefin-based derivatives having units of monomers containing cycloolefin, such as norbornene or polycyclic norbornene monomer, Cellulose, ie, diacetyl cellulose, triacetyl cellulose, acetyl cellulose butyrate, isobutyl ester cellulose, ethylene-vinyl acetate copolymer, propionyl cellulose, butyryl cellulose, acetyl propionyl cellulose or polycycloolefin, polyester, polystyrene, Polyamide, polyetherimide, polyacryl, polyimide, polyethersulfone, polysulfone, polyethylene, polypropylene, polymethylpentene, polyvinyl chloride, polyvinylidene chloride, polyvinyl alcohol, polyvinyl acetal, polyether ketone, Polyetheretherketone, Poly A film made of at least one selected from thermoplastic polymers such as tersulphone, polymethyl methacrylate, polyethylene terephthalate, polycarbonate, polybutylene terephthalate, polyethylene naphthalate, polyurethane, and epoxy may be used. I), uniaxial or biaxially oriented films can be used. Among them, triaxial cellulose and isobutyl ester are preferably monoaxial or biaxially stretched polyester film, polymethyl methacrylate film or polycycloolefin-based film having excellent transparency and heat resistance, but are not transparent and optically anisotropic. A film made of cellulose or the like is suitably used.

It is preferable that the thickness of the protective transparent film is thin, but if it is too thin, the strength decreases and the workability is inferior. On the other hand, if the thickness is too thick, problems such as transparency decrease or the weight of the polarizing plate increase. Therefore, it is about 8-1,000 micrometers, Preferably 40-100 micrometers is used.

[Surface Treatment Coating Layer]

As long as the objective of this invention is not impaired, the said transparent protective film may perform surface treatment etc. for the purpose of a high hardness treatment, a low reflection treatment, an antistatic treatment, an anti-glare treatment, etc.

The high hardness treatment is carried out for the purpose of preventing damage to the surface of the polarizing plate, and the like, for example, by using a suitable UV curable resin such as silicone, to form a cured film having excellent hardness and sliding property on the surface of the transparent protective film. Can be.

The low reflection treatment is carried out for the purpose of preventing reflection of external light on the surface of the polarizing plate, and can be achieved by forming an antireflection film or the like according to the prior art.

The antistatic treatment can achieve antistatic development, foreign matter adsorption, or adhesion to an adjacent layer.

The antiglare treatment is performed for the purpose of preventing external light from reflecting off the polarizing plate and impairing the visibility of the transmitted light of the polarizing plate. For example, a roughness increasing method or a method of blending transparent fine particles by a sand blast method or an embossing method, etc. It can be formed by providing a fine concavo-convex structure on the surface of the transparent protective film in an appropriate manner.

Examples of the transparent fine particles include silica, alumina, titania, zirconia, indium oxide, cadmium oxide, and ammonium oxide having an average particle diameter of 0.5 to 20 µm, and inorganic fine particles having conductivity may be used. Organic microparticles | fine-particles etc. which consist of an uncrosslinked polymer particulate matter etc. can be used.

[Adhesive layer]

An adhesive layer may be formed for the adhesive treatment of the polarizer and the transparent protective layer (generally in the form of a film). Although the adhesive agent used for an adhesive layer is not specifically limited, For example, the polyvinyl alcohol adhesive agent or urethane adhesive agent which has a refractive index in the range of 1.46-1.52 can be used. Examples of polyvinyl alcohol adhesives include polyvinyl alcohol, polyvinyl acetate partially saponified, polyvinyl alcohol modified with a carboxyl group or acetacetyl group, polyvinyl alcohol formalized or boric acid, borax, glutaraldehyde, and melanin in the adhesive. The adhesive agent which added water-soluble crosslinking agents, such as nitric acid, etc. are mentioned. As a urethane type adhesive agent, the reactive adhesive which consists of a polyol and polyisocyanate, the solution or emulsion of polyurethane, etc. are mentioned. The adhesive may be used as it is a commercially available adhesive that is transparent and optically isotropic. For example, there are POVAL Series manufactured by Kurage Co., Ltd. and Gohsenol Series manufactured by Nippon Synthetic Chemical Co., Ltd.

[adhesive]

As the pressure-sensitive adhesive, a (meth) acrylate copolymer, a crosslinking agent, a silane coupling agent and a small amount of additives (plasticizer, epoxy resin and curing agent, etc. may be further mixed and used, and an ultraviolet absorber, an antioxidant, a colorant, a reinforcing agent, a filler), etc. The substance dissolved in this organic solvent can be used.

[Long-wavelength visible light absorber]

As the long-wavelength visible light absorbing agent used in the present invention, one having a maximum absorption peak at a wavelength of 650 nm or more, preferably 700 nm or more is preferred, and particularly preferably a maximum absorption peak at 700 to 850 nm. In addition, it is preferable that the light absorption is low in the visible light region.

Such long wavelength visible light absorbers include those known as carbon black, infrared absorbing dyes or infrared absorbing pigments. Particular preference is given to using infrared absorbing dyes. Infrared absorption dyes include organic compounds and inorganic compounds. Although they absorb mainly the infrared region, while absorbing light in the visible region, while absorbing a relatively large amount of the long wavelength region in the visible region, the effect of the present invention can be realized.

Examples of the long-wavelength visible light absorber include anthraquinone (IR750), Nippon Chemical Co., Ltd., KIR101, SIR114, Mitsui Totsu Corporation, dioxadine, tripheno-dithiazine, and phenanthrene. (phenanthrene), cyanine (cyanine), phthalocyanine (phthalocyanine: KIR103, SIR103, Mitsui Toatsu Corporation) merocyanine (merocyanine), pyrylium (pyrylium), xanthine, triphenylmethane (triphenylmethane) ), Croconium (croconium), azo (azo), indigoid (indigoid), polymethine (polymethine: IR820, IRT, IR13F, Showa Deko KK Co., Ltd.), azulene (azulene), At least one selected from the group consisting of squarium-based, sulfide-based, and metal dithiolate-based dyes is preferable.

The method of including a long wavelength visible light absorber in a polarizing plate includes a method of including a long wavelength visible light absorber in an adhesive layer or an adhesive layer, a method of coating a long wavelength visible light absorber on at least one surface of the transparent protective layer constituting the polarizing plate, or a long wavelength visible light in a surface treatment coating layer. The method of including an absorbent is mentioned.

As a coating method, the above-mentioned long wavelength visible light absorbent is used at a predetermined concentration with respect to alcohols such as methanol, ethanol, isopropyl alcohol, ethoxyethanol and butyl alcohol, and 100 parts by weight of organic solvents such as cyclohexane, acetone and methyl ethyl ketone. Dissolve to 0.001 ~ 10 parts by weight and the solution is coated on the transparent protective film (example). The coating method is not particularly limited, but a method capable of coating with a uniform thickness is preferable. Such coating methods include spin coating, wire bar coating, micro gravure coating, gravure coating, dip coating, spray coating, and the like. have.

The method of removing the solvent from the long-wavelength visible light absorber solution coated at a predetermined concentration on the transparent protective film by the coating method is not particularly limited as long as it can remove most of the solvent, usually at room temperature drying, drying oven Drying, drying by heating on a heating plate, drying using infrared rays, and the like can be used.

When the long wavelength visible light absorber is coated on the polarizing plate layer, coating with a thickness of 1 nm to 10 μm is possible, but it is preferable to minimize the refraction of light caused by the long wavelength visible light absorber coating layer and to prevent coloring of the polarizing plate generated when the polarizing plate is excessively used. Preferably, a thickness of 10 nm to 100 nm is preferable.

Preferably, the method of including a long wavelength visible light absorber in an adhesive layer or an adhesion layer from the viewpoint of workability, manufacturing ease, and stability is preferable.

In the case where a long wavelength visible light absorbent is mixed with an adhesive layer or an adhesive layer, it is preferable to add 1 ppm to 10,000 ppm with respect to 1 g of the adhesive layer or adhesive layer remaining after drying. In order to minimize the brightness damage in the white state in the range is preferably a range having an addition amount of 10 ~ 1,000ppm. The polarizing plate including the long wavelength visible light absorbent may be manufactured when the polarizing plate is manufactured using an adhesive or / and an adhesive in which the long wavelength visible light absorbent is mixed.

The polarizing plate including the long-wavelength visible light absorbing agent according to an embodiment of the present invention has a polarization degree of 99.99 or more in parallel nicotine, a transmittance of 3% or less at 750 nm in orthogonal nicotine, and a transmittance at 780 nm as shown in Examples below. This can be 15% or less, which is excellent. In addition, when the contrast ratio is measured by the method described below, the contrast ratio of the liquid crystal display device to which the polarizing plate of the present invention is applied may be 1300: 1 or more, so that excellent contrast can be realized when the polarizing plate of the present invention is applied to the liquid crystal display device. .

The present invention also provides a liquid crystal display device to which the polarizing plate is applied.

By incorporating the polarizing plate of the present invention into a liquid crystal display device, various liquid crystal display devices of the present invention having excellent visibility can be manufactured. The polarizing plate of the present invention is preferably applied to a liquid crystal display device of various driving methods such as a reflection type, a transmission type, a transflective type liquid crystal display device, or a TN type, an STN type, an OCB type, an HAN type, a VA type, or an IPS type. have. The configuration of the liquid crystal display device is well known in the art, and thus description thereof is omitted.

Although the Example of this invention is given to the following and described, this invention is not limited to these Examples.

<Example 1>

Dry uniaxially stretch the polyvinyl alcohol film (polymerization degree 2,400, saponification degree 99.9 mol% or more) with a draw ratio of 5 times, and immerse in 60 ° C pure water for 60 seconds while maintaining the tension state. Iodine / potassium iodide / water was dyed by immersion for 60 seconds in an aqueous solution of 0.05 / 5/100 by weight ratio. Potassium iodide / boric acid / water was then immersed in an aqueous solution of 6 / 7.5 / 100 by weight ratio at 73 ° C. for 300 seconds. The obtained polarizer was immersed for 5 minutes in 25 degreeC distilled water, and it dried at 50 degreeC for 5 minutes, and manufactured the polarizer. Both surfaces of the obtained polarizer were adhere | attached on the saponified TAC film using polyvinyl alcohol adhesive (POVAL, Kurare), and it dried at 60 degreeC for 5 minutes, and obtained the polarizing plate whose protective transparent film is a TAC film to a polarizer.

On one side of the obtained polarizing plate, as a long-wavelength visible light absorber, a polymethine-based absorber (IRT, Showa Denko KK) was dissolved in isopropyl alcohol at a concentration of 250 ppm, and then coated at 1000 rpm using a spin coater (K-359, Kyowariken). A long wavelength visible light absorber having a thickness of 20 nm was coated on the polarizer. A polarizer with an adhesive was obtained by using a non-carrier film on one side of a polarizing plate coated with a long wavelength visible light absorbent.

<Example 2>

20 parts by weight of a pressure-sensitive adhesive (acrylic adhesive) was dissolved on 100 parts by weight of acetone on one side of the bonded polarizer obtained in Example 1, and then 0.002 parts by weight of a polymethine absorber (IRT, Showa Denko KK) was dissolved with a long wavelength visible light absorbent. A pressure-sensitive adhesive liquid containing a visible light absorbent was prepared. The obtained pressure-sensitive adhesive liquid was dried on a release-treated PET film and then coated and formed using a baker bar so that the coating film thickness was 25 μm, thereby transferring to the polarizing plate by a film lamination method to obtain a polarizing plate with an adhesive.

<Example 3>

After dissolving 1.5 parts by weight of polyvinyl alcohol (POVAL, Kurare) in 100 parts by weight of water, 8 parts by weight of the polymethine-based absorbent (IRT, Showa Denko KK) dissolved in isopropyl alcohol (the polymethine-based absorbent was dissolved in isopropyl alcohol. 0.2% melted solution) was added to prepare an adhesive in which a long wavelength visible light absorber was mixed. The polarizer obtained in Example 1 and the transparent protective film on both sides of the polarizer were bonded with the adhesive, and dried in a 50 ° C. oven to obtain a polarizing plate. The non-carrier film was used for the one side of the obtained polarizing plate, and the polarizing plate with an adhesive was obtained.

Comparative Example 1

The same as in Example 1 except that the long wavelength visible light absorber is not coated on the polarizing plate.

(Measurement and evaluation)

Orthogonal transmittance and polarization degree of the polarizing plates produced in Examples 1 to 3 and Comparative Example 1, and the brightness and contrast ratio of the liquid crystal display having the same were measured by the following method.

(1) Orthogonal Transmittance and Polarization

Orthogonal transmittances at wavelengths of 750 nm and 780 nm were obtained for the polarizing plates obtained in Examples and Comparative Examples using an integrated old spectrophotometer (V7100, Shimadzu Corporation). In addition, the average value was obtained by irradiating the parallel and orthogonal transmittance 10 times in the entire area of 380 to 780 nm, and the polarization degree was obtained by the following formula (1). The results are shown in Table 1 and FIG.

Equation 1) polarization degree = v ((parallel transmittance-orthogonal transmittance) / (parallel transmittance + orthogonal transmittance)))

Table 1

Example 1 Example 2 Example 3 Comparative Example 1 Orthogonal Transmittance (750nm) 1.82% 1.78% 1.96% 3.63% Orthogonal Transmittance (780nm) 11.70% 10.80% 12.30% 17.40% Polarization degree 99.993 99.993 99.993 99.992

(2) Measurement of White Luminance and Contrast Ratio

After attaching the polarizing plates obtained in Examples and Comparative Examples to the 32-inch Samsung Bordeaux panel, using a contrast measuring instrument (SR-3A-12, TOPCON) to measure the contrast ratio for nine points to calculate the average value. The results are shown in Table 2 below.

Table 2

Example 1 Example 2 Example 3 Comparative Example 1 White brightness 616 608 604 610 Contrast Ratio 1,624 1,645 1,582 1,188

As can be seen from the results of Table 1, Table 2 and Figure 3 Examples 1 to 3 has a cross-permeability of 1% or less at a wavelength of 380 ~ 700nm, orthogonal transmittance of 3% or less at 750nm, 15 at 780nm Less than% light leakage Therefore, the liquid crystal display device employing the polarizing plates of Examples 1 to 3 has a good contrast ratio. However, in Comparative Example 1, although the light leakage is small with the orthogonal transmittance of 1% or less at the wavelength of 380-700 nm, the orthogonal transmittance is greater than 3% at 750 nm, and the orthogonal transmittance is greater than 15% at 780 nm, compared with the values of Examples 1 to 3. Each measurement peak has a larger value. Therefore, the contrast ratio of the liquid crystal display device to which the polarizing plate of Comparative Example 1 is applied is small and reddish.

The polarizing plate according to the present invention could be manufactured stably and easily with little light leakage in the orthogonal nicotine state while minimizing the reduction of the brightness in the white display in the parallel nicol state. In addition, the liquid crystal display device employing the polarizing plate of the present invention could have excellent contrast.

Claims (7)

In the polarizing plate comprising a polarizer, a transparent protective layer laminated on at least one surface of the polarizer via an adhesive layer and an adhesive layer laminated on any one surface of the transparent protective layer, A polarizing plate comprising a long wavelength visible light absorber having a maximum absorption peak in the wavelength range of 650nm or more. The polarizing plate according to claim 1, wherein in the orthogonal nicotine, the transmittance at 750 nm is 3% or less, and the transmittance at 780 nm is 15% or less. The polarizing plate of claim 1, wherein the long wavelength visible light absorbent is included in the adhesive layer or the adhesive layer. The polarizing plate of claim 1, wherein the long wavelength visible light absorber is coated on at least one surface of the transparent protective layer. The method of claim 1, wherein the long wavelength visible light absorbing agent, anthraquinone (diohraquinone), dioxadine (dioxadine), tripheno-dithiazine (phenhenrene), phenanthrene (cyanine), Phthalocyanine (merocyanine) merocyanine (merocyanine), pyrylium (pyrylium), xanthine (xanthine), triphenylmethane (triphenylmethane), croconium (azo), indigoide ( indigoid, polymethine, azulene, azulene, squaria, sulfide, sulfide, and metal dithiolate dyes. Polarizer. A liquid crystal display device comprising the polarizing plate of any one of claims 1 to 5. The liquid crystal display device according to claim 6, wherein the contrast ratio is 1300: 1 or more.

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