WO2013191418A1 - Polarization plate and liquid crystal display device comprising same - Google Patents

Abstract

The present invention relates to a polarization plate and to a liquid crystal display device comprising same. More particularly, the polarization plate comprises a first protective film, a polarizer, a second protective film, and an adhesive layer stacked in the abovementioned order. The first protective film or the first and second protective films extend in a machine direction (MD), and have a front phase difference value (RO) of 300 nm or higher. The above-described polarization plate is used as a polarization plate for a liquid crystal display device, in which the protective film is inexpensive and has a high phase difference. Therefore, excellent price competitiveness can be achieved and rainbow discoloration, which might otherwise be caused by the first protective film, can be suppressed so as to maintain the quality of an image (e.g., to ensure a viewing angle).

Description

Polarizing plate and liquid crystal display including the same

The present invention relates to a polarizing plate capable of suppressing rainbow spots caused by the use of a protective film having a high phase difference, and a liquid crystal display including the same.

Liquid crystal displays (LCDs) replace the cathode-ray tubes (CRTs), which have the highest market share among flat panel displays and are most popular among image display devices.

Liquid crystal displays have improved many technical shortcomings in the early stages of development, and are currently making efforts to expand market share by increasing price competitiveness. Accordingly, attempts have also been made on polarizers, which are key components of the liquid crystal display.

A representative method of improving the price competitiveness of the polarizing plate is to use a low-cost polarizer protective film.

The polarizer protective film is mainly for protecting the weak polarizer mechanically. Recently, the protective film laminated on the side of the liquid crystal panel of the polarizer has been added to compensate the viewing angle by giving the appropriate phase difference through the stretching. In the case of the protective film laminated on the other side of the liquid crystal panel in the double polarizer, it is a general recognition to engineers in the art that the retardation value does not affect the optical characteristics.

 Triacetyl cellulose (TAC) or the like is typically used as such a protective film. Triacetyl cellulose (TAC) is usually produced by a casting method and the solvent is volatilized to form a negative C plate. Such triacetyl cellulose (TAC) is much higher in price than the general plastic film.

Thus, attempts are being made to replace plastic films having a lower cost as protective films instead of triacetyl cellulose (TAC).

However, the low-cost plastic film is generally stretched at a high magnification to increase the yield, so that the phase difference is large, and the liquid crystal display device in which the low-cost plastic film is laminated has a disadvantage in that image quality is degraded due to rainbow spots.

In addition, as a method for suppressing the occurrence of rainbow staining by the film stretched at high magnification, a method of treating the surface of the film stretched at high magnification or adding a diffusion agent to the film drawn at high magnification has been proposed. . However, even in this case, there is a problem that the quality of the image is deteriorated or the manufacturing cost is increased.

An object of the present invention is to provide a polarizing plate that can use a protective film having a low-cost high-order difference without deteriorating the image quality.

Another object of the present invention is to provide a liquid crystal display device having the polarizing plate.

In order to achieve the above object, the present invention is laminated in the order of the first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer, the first protective film is uniaxially stretched in the MD direction (Machine Direction), the front phase difference value A polarizing plate having a (RO) of 300 nm or more is provided.

The first protective film may have a front retardation value RO of 500 nm or more.

In addition, the present invention is laminated in the order of the first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer, the first protective film and the second protective film are each uniaxially stretched in the MD direction (Machine Direction), the front phase difference A polarizing plate having a value RO of 300 nm or more is provided.

Each of the first protective film and the second protective film may have a front retardation value RO of 500 nm or more.

The first protective film may have a refractive index ratio NZ of 0 ≦ NZ ≦ 1.

Preferably, the first protective film may have a refractive index ratio NZ of 0 or 1.

The first protective film is cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polysulfone (PSF) And it may be at least one selected from the group consisting of polymethyl methacrylate (PMMA).

The first protective film may include a surface treatment layer on the opposite side of the surface bonded to the polarizer.

The second protective film may have a refractive index ratio NZ of 0 or 1.

The second protective film is cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polysulfone (PSF) And it may be at least one selected from the group consisting of polymethyl methacrylate (PMMA).

In addition, the present invention provides a liquid crystal display device including a polarizing plate.

The backlight may be a polarized backlight.

The polarizing plate of the present invention not only has excellent price competitiveness by using a low cost high-level protective film when the liquid crystal display device is applied, but also suppresses the occurrence of rainbow stains due to the high-level protective film, thereby maintaining image quality (viewing angle). Securing, etc.) is possible.

1 is a vertical cross-sectional view of a polarizing plate according to the present invention,

2 shows the structure of a liquid crystal display device of Embodiment 1 according to the present invention,

3 shows omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 1 according to the present invention;

4 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 2 according to the present invention;

5 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 3 according to the present invention;

6 shows omnidirectional transmission characteristics when voltage is applied in the liquid crystal display of Example 4 according to the present invention;

7 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 5 according to the present invention;

8 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 6 according to the present invention;

9 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 7 according to the present invention;

10 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 8 according to the present invention;

11 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 9 according to the present invention;

12 illustrates omnidirectional transmission characteristics when a voltage is applied in the liquid crystal display of Example 10 according to the present invention;

FIG. 13 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 11 according to the present invention; FIG.

14 illustrates omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Example 12 according to the present invention;

15 illustrates omnidirectional transmission characteristics when the voltage of the liquid crystal display of Comparative Example 1 is applied;

16 shows omnidirectional transmission characteristics when the voltage is applied to the liquid crystal display of Comparative Example 2. FIG.

The present invention relates to a polarizing plate capable of suppressing rainbow spots caused by the use of a protective film having a high phase difference, and a liquid crystal display including the same.

The rainbow blot is a phenomenon in which polarization causes a large change in retardation value depending on an incident angle when polarized light passes through the retardation layer and a large difference in retardation value according to wavelength.

Since the high retardation film is usually produced by high magnification stretching, since the retardation value is large and the change in retardation value according to the incident angle is large, rainbow spots are generated when polarization passes. Moreover, since most of the films have the wavelength dispersion, the change of the phase difference value according to the wavelength becomes larger.

The present invention is applied to the high-phase retardation film as a protective film of the polarizing plate, by controlling the stretching method and the refractive index ratio of the high-order retardation film in a specific range to suppress the occurrence of rainbow stains.

Hereinafter, the present invention will be described in detail.

The polarizing plate of the present invention is laminated in the order of the first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer. The first protective film is uniaxially stretched in the MD direction (Machine Direction), the front retardation value (RO) is 300nm or more, preferably 500nm or more.

In the polarizing plate of the present invention, the first and second protective films are uniaxially stretched in the MD direction, respectively, and the front retardation value RO is 300 nm or more, preferably 500 nm or more.

In particular, when the liquid crystal cell is a mode in which the liquid crystal rotates in-plane, such as the IPS mode, the FFS mode, the PLS mode, and the ADS mode, it is preferable to use the same first protective film and the second protective film.

In general, when the film is manufactured by the stretching process, the more the stretching proceeds, the larger the retardation value and the lower the manufacturing cost per unit area of the film. Triacetyl cellulose (TAC), which is a typical protective film of the related art, exhibits optical characteristics of a front retardation value (RO) of 10 nm or less and a thickness direction retardation value (Rth) of 30 to 50 nm without stretching. This optical characteristic is a remarkably lower retardation range than common plastic films we usually see.

Equations 1 to 3 define the front phase difference value RO, the thickness direction phase difference value Rth, and the refractive index ratio NZ, which are optical characteristics of the first protective film and the second protective film. At this time, the optical characteristic is for the electric field in the visible light region.

[Equation 1]

RO = (Nx-Ny) × d

(Where Nx and Ny are planar refractive indices Nx ≧ Ny, and d represents the thickness of the film)

[Equation 2]

Rth = [(Nx + Ny) / 2- Nz] × d

(Where Nx and Ny are planar refractive indices Nx ≧ Ny, Nz represents the thickness direction refractive index of the film, and d represents the thickness of the film)

[Equation 3]

NZ = (Nx-Nz) / (Nx-Ny) = Rth / RO + 0.5

(Where Nx and Ny are plane refractive indices Nx ≧ Ny, and Nz represents the thickness direction refractive index of the film)

The present invention is to apply a high-stretch film used as a film in the art without limiting the retardation value of the optical properties of the protective film as in the prior art. The film having the front phase retardation value (RO) of 300 nm or more is stretched with high magnification and is a general optical property of a film having a low product cost per unit area.

The first protective film, or the first and second protective films must be uniaxially stretched in the MD direction (Machine Direction). The MD direction refers to a direction in which a film existing in a roll state is unrolled or wound on a roll before being bonded to the polarizer, and uniaxial stretching refers to a film oriented by stretching only in one direction.

When the film is uniaxially stretched in the MD direction, the extension line of the optical axis does not come out of the surface of the film and exists in the surface, so that high-order mura does not occur.

In addition, the first protective film preferably has a refractive index ratio (NZ) of 0 ≦ NZ ≦ 1, NZ is 0 or 1 in consideration of process ease and industrial usefulness. If the refractive index ratio NZ is less than 0 or more than 1, a problem may occur in which high-order difference stains occur on the inclined surface.

The first protective film is cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polysulfone (PSF) And polymethyl methacrylate (PMMA) may be used one or more selected from the group consisting of.

In addition, the first protective film may include a surface treatment layer on the opposite side of the surface bonded to the polarizer.

The polarizer is an optical film that serves to change the incident natural light into a desired single polarization state (linear polarization state), and a dichroic dye is adsorbed and oriented on a film made of polyvinyl alcohol-based resin.

Polyvinyl alcohol-type resin which comprises a polarizer can be manufactured by saponifying polyvinyl acetate type resin. Examples of the polyvinyl acetate-based resin include copolymers with other monomers copolymerizable with vinyl acetate, in addition to polyvinyl acetate, which is a homopolymer of vinyl acetate. Specific examples of the other monomer copolymerizable with vinyl acetate include unsaturated carboxylic acids, unsaturated sulfonic acids, olefins, vinyl ethers, acrylamides having an ammonium group, and the like. In addition, the polyvinyl alcohol-based resin may be modified, for example, polyvinyl formal or polyvinyl acetal modified with aldehydes may be used. The degree of saponification of the polyvinyl alcohol-based resin may be 85 to 100 mol%, preferably 98 mol% or more. In addition, the degree of polymerization of the polyvinyl alcohol-based resin is usually 1,000 to 10,000, preferably 1,500 to 5,000.

This polyvinyl alcohol-based resin is formed into a film and used as a polarizer. The film forming method of the polyvinyl alcohol-based resin is not particularly limited, and various known methods can be used. The film thickness of the polyvinyl alcohol-based resin is not particularly limited, and may be, for example, 3 to 150 μm.

A polarizer is normally manufactured through the process of uniaxially stretching a polyvinyl alcohol-type film as described above, a process of dyeing with a dichroic dye, adsorbing, treating with an aqueous solution of boric acid, and washing with water and drying.

The process of uniaxially stretching the polyvinyl alcohol-based film may be performed before dyeing, simultaneously with dyeing, or after dyeing. If uniaxial stretching is carried out after dyeing, it may be carried out before or during boric acid treatment. Of course, it is also possible to perform uniaxial stretching in a plurality of stages in which each of them is combined. Uniaxial stretching may use rolls or thermal rolls having different circumferential speeds, and may be dry stretching in the air or wet stretching in a state swelled with a solvent. The draw ratio is usually 3 to 8 times.

For the process of dyeing the stretched polyvinyl alcohol-based film with a dichroic dye, for example, a method of immersing the polyvinyl alcohol-based film in an aqueous solution containing a dichroic dye may be used. Specific examples of the dichroic dye include iodine or a dichroic organic dye. In addition, the polyvinyl alcohol-based film is preferably swelled by dipping in water before dyeing.

When using iodine as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type film in the dyeing aqueous solution containing iodine and potassium iodide can be used normally. Usually, the content of iodine in the aqueous solution for dyeing is 0.01 to 1 part by weight based on 100 parts by weight of water (distilled water), and the content of potassium iodide is 0.5 to 20 parts by weight based on 100 parts by weight of water. The temperature of the aqueous solution for dyeing is usually 20 to 40 ° C., and the immersion time, for example, the dyeing time is usually 20 to 1800 seconds.

On the other hand, when using a dichroic organic dye as a dichroic dye, the method of immersing and dyeing a polyvinyl alcohol-type film in the aqueous solution for dyeing containing a water-soluble dichroic organic dye can be used normally. The content of the dichroic organic dye in the aqueous solution for dyeing is preferably 1 × 10 ^-4 to 10 parts by weight, preferably 1 × 10 ^-3 to 1 part by weight based on 100 parts by weight of water. The aqueous dyeing solution may further contain an inorganic salt such as sodium sulfate as a dyeing aid. The temperature of the aqueous solution for dyeing is usually 20 to 80 ° C., and the immersion time such as dyeing time is usually 10 to 1,800 seconds.

Boric acid treatment of the dyed polyvinyl alcohol-based film can be carried out by immersing in a boric acid-containing aqueous solution. Usually, the content of boric acid in the aqueous solution containing boric acid is 2 to 15 parts by weight, preferably 5 to 12 parts by weight, based on 100 parts by weight of water. The boric acid-containing aqueous solution in the case of using iodine as a dichroic dye preferably contains potassium iodide, and its content is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight with respect to 100 parts by weight of water. The temperature of the boric acid-containing aqueous solution is 50 ° C or higher, preferably 50 to 85 ° C, more preferably 60 to 80 ° C, and the immersion time is 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably It is preferable that it is 200 to 400 seconds.

After the boric acid treatment, the polyvinyl alcohol-based film is washed with water and dried. Washing treatment may be performed by immersing the boric acid-treated polyvinyl alcohol-based film in water, the temperature of the water during the washing treatment is 5 to 40 ℃, immersion time is 1 to 120 seconds. The polarizer can be obtained by drying after washing with water. The drying treatment may be generally performed using a hot air dryer or a far infrared heater, and the drying treatment temperature is usually 30 to 100 ° C., preferably 50 to 80 ° C., and the drying time is usually 60 to 600 seconds, preferably 120 to 80 ° C. 600 seconds is good.

The polarizer may have a thickness of 3 to 40 μm.

The second protective film is a film for protecting the polarizer because it is mechanically weak.

The second protective film has a moisture permeability different according to the type of resin, and may be selected and used according to transparency, mechanical strength, thermal stability, moisture shielding, and isotropy.

Specific examples thereof include polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene naphthalate, and polybutylene terephthalate; Cellulose resins such as diacetyl cellulose and triacetyl cellulose; Polycarbonate resins; Acrylic resins such as polymethyl (meth) acrylate and polyethyl (meth) acrylate; Styrene resins such as polystyrene and acrylonitrile-styrene copolymers; Polyolefin resins such as polyethylene, polypropylene, cyclo-based or norbornene-structured polyolefins, ethylene-propylene copolymers; Vinyl chloride-based resins; Amide resins such as nylon and aromatic polyamides; Imide resin; Polyether sulfone resin; Sulfone resins; Polyether sulfone resin; Polyether ether ketone resins; Sulfided polyphenylene resins; Vinyl alcohol-based resins; Vinylidene chloride-based resins; Vinyl butyral resin; Allyl resins; Polyoxymethylene resin; Films selected from the group consisting of thermoplastic resins such as epoxy resins can be used, and films composed of blends of the thermoplastic resins can also be used. Moreover, you may use the film which consists of thermosetting resins, such as a (meth) acrylic-type, a urethane type, an acryl urethane type, an epoxy type, a silicone type, or an ultraviolet curable resin.

In the second protective film, the content of the thermoplastic resin is 50 to 100% by weight, preferably 50 to 99% by weight, more preferably 60 to 98% by weight, and most preferably 70 to 97% by weight. If the content is less than 50% by weight, it may not sufficiently express the inherent high transparency of the thermoplastic resin.

In addition, in the present invention, the second protective film may be uniaxially stretched in the machine direction (MD), and the front retardation value RO may be 300 nm or more, in which case the refractive index ratio NZ is preferably 0 or 1.

When the NZ of the second protective film is 0 or 1, the optical axis can be hidden in the film plane, which is more effective in suppressing rainbow spots. At this time, the material of the second protective film is the same as the first protective film.

The thickness of the first and second protective films is not particularly limited, but if the thickness is too thin, the strength and the workability are lowered. If the thickness is too thick, the transparency or the curing time is long after lamination to the polarizer. The thickness of the protective film is 5 to 200 μm, respectively, preferably 10 to 150 μm, more preferably 20 to 100 μm.

An adhesive layer is formed between the polarizer and the first protective film and between the polarizer and the second protective film. For example, the adhesive layer may use an aqueous adhesive or a UV curable adhesive.

The adhesive is not particularly limited as long as it can sufficiently bond the polarizer and the protective film, and has excellent optical transparency and no change in yellowing over time, and for example, an aqueous adhesive composition containing a polyvinyl alcohol-based resin and a crosslinking agent. Can be mentioned.

The polyvinyl alcohol-based resin contained in the water-based adhesive composition may be a polyvinyl alcohol resin or a polyvinyl alcohol resin having an acetoacetyl group, and among these, the polyvinyl alcohol resin having an acetoacetyl group is a polyvinyl having a highly reactive functional group. The alcohol adhesive is preferable in that durability of the polarizing plate is improved.

The resin contained in the UV curable adhesive composition may be generally used in the art, and may be an epoxy resin, an acrylic resin, or the like.

In addition, in order to increase the adhesion to the surface of the polarizer to be bonded to the protective film, surface treatment such as plasma treatment, corona treatment, ultraviolet irradiation treatment, flame (flame) treatment or saponification treatment may be appropriately performed.

The method of bonding the protective film to the polarizer with an adhesive may use a method commonly known in the art, for example, a polarizer, a protective film by a casting method, a wire bar coating method, a gravure coating method, a die coating method, or a spraying method. Or the method of apply | coating an adhesive agent to all these bonding surfaces, and bonding them is mentioned. In this case, the casting method is performed by moving the polarizer or the protective film to be coated in a substantially vertical direction, a substantially horizontal direction, or in an inclined direction between them, while dropping an adhesive on the surface of the coated object to expand (

) After apply | coating an adhesive agent, a polarizer and a protective film are pinched together and bonded together.

The pressure-sensitive adhesive layer may be formed of a pressure-sensitive adhesive composition commonly used in the art, which includes a pressure-sensitive adhesive resin and a crosslinking agent as a layer for bonding to a liquid crystal cell.

The pressure-sensitive adhesive resin contained in the pressure-sensitive adhesive composition may be an acrylic, silicone, rubber, urethane, polyester or epoxy copolymer, etc., preferably an acrylic copolymer. The pressure-sensitive adhesive composition may also contain known antistatic agents such as alkali metal salts, ionic compounds, conductive polymers, metal oxides, and CNTs. Among these, it is more preferable to include an ionic compound.

The method of laminating the pressure-sensitive adhesive layer on the polarizing plate is not particularly limited as long as it is a method commonly used in the art. For example, the pressure-sensitive adhesive composition on the antistatic coating layer formed on the polarizer protective film can be applied by using the same method as in the coating method of the antistatic coating liquid composition, dried and laminated. In addition, after forming a pressure-sensitive adhesive layer by forming the pressure-sensitive adhesive layer on the silicone-coated release film by the same coating method as described above, it may be laminated on the antistatic coating layer formed on the polarizer protective film using a roll pressing device. At this time, when the ultraviolet-curable compound is contained in the pressure-sensitive adhesive composition as a crosslinking agent, it is preferable to irradiate ultraviolet rays after applying the pressure-sensitive adhesive composition or after lamination using a roll pressing device.

The thickness of the pressure-sensitive adhesive layer can be adjusted according to the adhesive force, it is usually preferably 3 to 100㎛, more preferably 10 to 100㎛.

In the liquid crystal display device of the present invention, the polarizing plate may be provided on the upper plate, the lower plate, or the upper / lower plate. When the polarizing plate is provided on the upper plate or the lower plate, the other polarizing plate is generally used in the art and may use a form in which a protective film is bonded to both surfaces of the polarizer.

Hereinafter, preferred examples are provided to aid the understanding of the present invention, but the following examples are merely for exemplifying the present invention, and it will be apparent to those skilled in the art that various changes and modifications can be made within the scope and spirit of the present invention. It is natural that such variations and modifications fall within the scope of the appended claims.

Example 1

Measurement data of each optical film, a liquid crystal cell, and a backlight according to the present invention were laminated on a TECH WIZ LCD with a structure as shown in FIG. 2. The liquid crystal cell of the 55-inch PS-VA mode liquid crystal display device was laminated on TECH WIZ LCD.

The liquid crystal display device was composed of a polarizing backlight, a lower polarizing plate PS-VA mode liquid crystal cell, and an upper polarizing plate. The upper and lower polarizing plates were laminated in the order of the pressure-sensitive adhesive layer, the second protective film, the adhesive layer, the polarizer, the adhesive layer, and the first protective film, respectively, from the liquid crystal cell side.

The polarizer imparted polarizer function to the PVA through stretching and dyeing, and the absorption axis of the backlight-side polarizer was stacked in the vertical direction when viewed from the viewer side, and the absorption axis of the viewer-side polarizer was disposed in the horizontal direction.

The polarizing performance of such a polarizer was 99.9% or more of visibility polarization degree and 41% or more of visibility single transmittance in 370-780 nm visible light region. The visibility polarization and the visibility single transmittance were determined by TD (λ) for the transmission axis according to the wavelength, and MD (λ) for the absorption axis according to the wavelength, according to the visibility correction values defined in JIS Z 8701: 1999.

Is defined by the following equations (4) to (8).

[Equation 4]

[Equation 5]

[Equation 6]

[Equation 7]

[Equation 8]

Each of the first protective film of the upper plate and the lower plate was uniaxially stretched in the MD direction, and a polyethylene terephthalate (PET) film having a front retardation value (RO) of 2000 nm and a refractive index ratio (NZ) of 1 was laminated at a light source 589 nm. . The first protective film was laminated so that the directions of absorption and slow axes of adjacent polarizers were perpendicular to each other.

Each of the upper and lower plates of the second protective film is a protective film having a phase difference compensation function. A cycloolefin polymer (COP) having a front phase difference value (RO) of 50 nm and a thickness direction phase difference value (Rth) of 125 nm at a light source 589 nm. The film was laminated.

The upper polarizer and the lower polarizer each formed an acrylic adhesive layer between the protective films on both sides.

3 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 2

The first protective film of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front phase difference value (RO) is 2000 nm, and the refractive index ratio (NZ) is 0 at the light source 589 nm. Polystyrene (PS) films were laminated.

4 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 3

The first protective film of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front phase difference value (RO) is 1000 nm, and the refractive index ratio (NZ) is 1 at the light source 589 nm. Polyethylene terephthalate (PET) film was laminated.

5 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 4

The first protective film of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 500 nm and the refractive index ratio (NZ) is 1 at 589 nm. Polyethylene terephthalate (PET) film was laminated.

6 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 5

In the same manner as in Example 1, each of the first and second protective films of the upper plate and the lower plate of the IPS mode liquid crystal panel is uniaxially stretched in the MD direction, and the front phase difference value (RO) is 2000 nm at the light source 589 nm, A polyethylene terephthalate (PET) film having a refractive index ratio (NZ) of 1 was laminated.

7 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 6

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 2000 nm at the light source 589 nm, the refractive index ratio (NZ) A polystyrene (PS) film having 0 was laminated.

8 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that the rainbow spots did not occur at all.

Example 7

The first protective film of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 2000 nm, and the refractive index ratio (NZ) is 0 at the light source 589 nm. A modified polystyrene (PS) film was laminated.

In addition, each of the second protective films of the upper plate and the lower plate is uniaxially stretched in the MD direction, and a polyethylene terephthalate (PET) film having a front retardation value (RO) of 2000 nm and a refractive index ratio (NZ) of 1 at a light source 589 nm. Laminated.

9 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 8

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 500 nm at the light source 589 nm, the refractive index ratio (NZ) A polyethylene terephthalate (PET) film having a value of 1 was laminated.

10 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 9

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 300 nm at the light source 589 nm, the refractive index ratio (NZ) A polyethylene terephthalate (PET) film having a value of 1 was laminated.

11 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 10

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate is uniaxially stretched in the MD direction, the front retardation value (RO) is 300 nm at the light source 589 nm, the refractive index ratio (NZ) A modified polystyrene (PS) film having a value of 0 was laminated.

12 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 11

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate was uniaxially stretched in the MD direction. The first protective film was laminated with a polyethylene terephthalate (PET) film having a front retardation value (RO) of 300 nm and a refractive index ratio (NZ) of 0.8 at a light source 589 nm, and the second protective film having a retardation value (RO) of The polyethylene terephthalate (PET) film which is 300 nm and whose refractive index ratio (NZ) is 1 was laminated | stacked.

13 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Example 12

In the same manner as in Example 5, each of the first and second protective films of the upper plate and the lower plate was uniaxially stretched in the MD direction. The first protective film was laminated with a modified polystyrene (PS) film having a front retardation value (RO) of 300 nm and a refractive index ratio (NZ) of 0.2 at a light source 589 nm, and the second protective film having a retardation value (RO) of 300. A modified polystyrene (PS) film having a nm thickness and a refractive index ratio (NZ) of 0 was laminated.

14 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display device, it was confirmed that no rainbow spots occurred.

Comparative Example 1

The first protective film of the upper plate and the lower plate is uniaxially stretched in the TD direction, the front retardation value (RO) is 2000 nm, and the refractive index ratio (NZ) is 1.9 at the light source 589 nm. It was laminated.

15 is a result of calculating the rainbow spots in all directions by applying a voltage to the liquid crystal cell of the liquid crystal display, it was confirmed that a number of rainbow spots occurred.

Comparative Example 2

The same process as in Example 1, except that the first protective film of the upper plate and the lower plate was biaxially stretched, and the front phase difference value (RO) was 2000 nm and the refractive index ratio (NZ) was 3 at the light source 589 nm. .

16 is a result of calculating rainbow spots in all directions by applying voltage to the liquid crystal cell of the liquid crystal display, and it was confirmed that a plurality of rainbow spots occurred.

Claims (12)

1. The first protective film, the polarizer, the second protective film and the pressure-sensitive adhesive layer is laminated in order, the first protective film is uniaxially stretched in the MD direction (Machine Direction), the polarizing plate having a front phase difference value (RO) of 300nm or more.
2. The polarizing plate of claim 1, wherein the first protective film has a front retardation value (RO) of 500 nm or more.
3. The first protective film, the polarizer, the second protective film, and the pressure-sensitive adhesive layer are laminated in this order, and the first protective film and the second protective film are uniaxially stretched in the machine direction (MD), respectively, and the front phase difference value (RO) is 300 nm or more polarizing plate.
4. The polarizing plate according to claim 3, wherein the first protective film and the second protective film each have a front retardation value (RO) of 500 nm or more.
5. The polarizing plate of claim 1 or 3, wherein the first protective film has a refractive index ratio (NZ) of 0 ≦ NZ ≦ 1.
6. The polarizing plate of claim 5, wherein the first protective film has a refractive index ratio (NZ) of 0 or 1. 7.
7. The method of claim 1 or 3, wherein the first protective film is cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polystyrene (PS) ), Polysulfone (PSF) and polymethyl methacrylate (PMMA) is at least one member selected from the group consisting of.
8. The polarizing plate of claim 1 or 3, wherein the first protective film includes a surface treatment layer on an opposite surface of the surface to be bonded to the polarizer.
9. The polarizing plate of claim 3, wherein the second protective film has a refractive index ratio NZ of 0 or 1. 5.
10. The method of claim 3, wherein the second protective film is cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polystyrene (PS), Polysulfone (PSF) and polymethyl methacrylate (PMMA) is one or more selected from the group consisting of a polarizing plate.
11. Liquid crystal display comprising the polarizing plate of claim 1 or 3.
12. The liquid crystal display device of claim 11, wherein the backlight is a polarized backlight.

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