TWI537618B - Coupled polarizing plate set and in-plane switching mode liquid crystal display including the same - Google Patents

Description

Coupling polarizing plate group and coplanar switching mode liquid crystal display including coupled polarizing plate group

The invention relates to a coupled polarizing plate group and an IPS (coplanar switching) mode liquid crystal display, which can maintain the phase difference compensation effect of the initial design due to resistance to physical changes even if the coupled polarizing plate group is exposed to a high temperature and high humidity environment for a long time. .

Liquid crystal displays (LCDs) are widely used as general image displays.

The mode of the liquid crystal display is distinguished by the initial alignment of the liquid crystal, the electrode structure, and the liquid crystal properties. The currently widely used liquid crystal display modes include a twisted nematic (TN), a vertical alignment (VA), and an in-plane switching (IPS) mode. Furthermore, the liquid crystal display is divided into a normally black or normally white mode depending on whether or not light is transmitted when no voltage is applied. Furthermore, the VA mode is divided into PVA (pattern ed VA), SPVA (Super PVA), MVA (multi-domain VA) mode depending on the area of the liquid crystal and the initial alignment, and the IPS mode is divided into an S-IPS or FFS mode.

The liquid crystal particle alignment of the coplanar switching mode (hereinafter, referred to as IPS mode) is substantially uniform and parallel to the surface of the liquid crystal substrate when inactive. In the IPS mode, when the transmission axis of the lower substrate conforms to the fast axis direction of the liquid crystal particles on the front surface, the transmission axis of the lower substrate also conforms to the fast axis of the liquid crystal particles on the inclined surface. Therefore, the light passing through the lower polarizing plate passes through the liquid crystal without changing the polarization state, so that the black state can be implemented in the inactive state by arranging the polarizing plates up and down.

The IPS mode liquid crystal display can achieve a wide viewing angle without using an optical film that compensates for changes in polarization state, and can be used for a large and expensive device due to natural transmittance, ensuring uniform image quality and viewing angle on the entire screen.

A conventional IPS mode liquid crystal display includes a liquid crystal cell having a liquid crystal, a polarizer polarized on both sides of the liquid crystal cell, and a polarizer protective film made of a cellulose triacetate (TAe) film on one side or both sides of the polarizer. In this configuration, when the black state is implemented, the light polarized by the polarizer disposed on the lower plate is elliptically polarized by the cellulose triacetate on the inclined surface, and the polarization of the elliptically polarized light is amplified by the liquid crystal cell, so that the light has various colors. No light leakage.

In recent years, IPS mode liquid crystal displays have to increase the size and improve light leakage and various colors to ensure a wide viewing angle.

Thus, the IPS mode liquid crystal display is provided with an isotropic protective film between a polarizer (PVA) and a liquid crystal cell, and two or more having different optical characteristics between another polarizer (PVA) and a liquid crystal cell. A compensation film or a z-axis alignment (thickness direction alignment) film is stacked. The unstretched film acts as a compensation film to enhance the optical characteristics of the liquid crystal display (contrast, etc.).

However, the unstretched film is advantageous for enhancing optical characteristics, but the film properties are sensitive to physical changes caused by high temperature and high humidity external environments, so that phase difference and brightness change.

Accordingly, it is an object of the present invention to provide a coupled polarizing plate which maintains the phase difference compensation effect of the initial design due to resistance to physical changes even if the coupled polarizing plate group is exposed to a high temperature and high humidity environment for a long period of time.

Furthermore, another object of the present invention is to provide an IPS mode liquid crystal display in which uniform transmittance is used for all wavelengths to ensure excellent color perception on a viewing angle and an inclined surface.

According to an aspect of the present invention, a coupled polarizing plate set includes: an upper polarizing plate, wherein a protective film, a polarizing plate, a uniaxially stretched positive A plate, and a lower polarizing plate are sequentially stacked; wherein the uniaxial stretching is sequentially performed The positive A plate, the polarizer, and the protective film, wherein the positive A plate of the upper polarizing plate and the lower polarizing plate have a coplanar retardation (RO) of 10 to 100 nm each, and the slow axis is parallel to the absorption axis of the adjacent polarizer.

The coplanar retardation (RO) of the positive A plate may be 10 to 80 nm.

The coplanar retardation (RO) of the positive A plate is preferably from 10 to 50 nm.

The positive A plate has a refractive index (NZ) of 0.9 to 1.1.

The positive A plate can be selected from TAC (cellulose triacetate), COP (cycloolefin polymer), COC (cycloolefin copolymer), PET (polyethylene terephthalate), PP (polypropylene), PC ( It is made up of a group consisting of polycarbonate), PSF (polyfluorene), and PMMA (polymethyl methacrylate).

The absorption axes of the upper polarizing plate and the lower polarizing plate may be perpendicular to each other.

According to another aspect of the present invention, an IPS mode liquid crystal display comprising the above-described coupled polarizing plate group is provided.

The present invention can provide a laminated polarizer set which maintains the phase difference compensation effect of the initial design due to resistance to physical changes even if the laminated polarizer group is exposed to a high temperature and high humidity environment for a long period of time.

Furthermore, the present invention can provide an IPS mode liquid crystal display, and by including a polarizing plate, an excellent viewing angle can be ensured even in a high temperature and high humidity environment.

Furthermore, by presenting a uniform transmittance for all wavelengths, the present invention can provide an IPS mode liquid crystal display having excellent color feeling even on an inclined surface.

Furthermore, the present invention enables a coupled polarizing plate group or a liquid crystal display including a coupled polarizing plate group to be transported through or used in a high temperature and high humidity region, such as a tropical region, an offshore region, and an equatorial region.

Furthermore, the present invention can be effectively used even if a backlight having a large amount of heat is used, or the size of the liquid crystal display is lowered to reduce the distance between the polarizing plate and the backlight.

The invention relates to a coupled polarizing plate group and an IPS (coplanar switching) mode liquid crystal display, which can maintain the phase difference compensation effect of the initial design due to resistance to physical changes even if the coupled polarizing plate group is exposed to a high temperature and high humidity environment for a long time. .

Hereinafter, the coupled polarizing plate group of the present invention will be described in detail.

The coupled polarizing plate assembly of the present invention comprises an upper polarizing plate for sequentially stacking a protective film, a polarizing plate, a uniaxially stretched positive A plate, and a lower polarizing plate for sequentially stacking a uniaxially stretched positive A plate, a polarizing plate, and a protective film. .

The coplanar retardation (RO) and refractive index (NZ) of the positive A plate of the upper polarizing plate and the lower polarizing plate are each 10 to 100 nm and 0.9 to 1.1. Furthermore, the slow axis is parallel to the absorption axis of the adjacent polarizer.

The polarizer is an optical film that changes the incident natural light into a single polarization state (linear polarization state) as long as the general polarization function can be performed.

For example, the polarizer can be produced by dyeing polyvinyl alcohol (PVA) with iodine or a dichroic dye and then stretching in a predetermined direction. Further, a thin polarizing plate having a conductive pattern of a polarizing function and a thin polarizing plate of an insulating layer are plated on the groove, and a ridge of the crystal lattice can be used for the transparent substrate.

The polyvinyl alcohol resin constituting the polarizer can be obtained by saponification of a polyvinyl acetate resin. The polyvinyl acetate resin may contain, for example, a copolymer of polyvinyl acetate, vinyl acetate, and any other monomer copolymerizable with vinyl acetate as a vinyl acetate homopolymer. The monomer copolymerizable with vinyl acetate may be selected from the group consisting of unsaturated carboxylic acid monomers, unsaturated sulfonic acid monomers, olefins, vinyl ester monomers, and acrylamide monomers having an ammonium group.

The polyvinyl alcohol resin may be a modified resin such as a resin modified with an aldehyde such as polyvinyl formal or polyvinyl acetal. The degree of saponification of the polyvinyl alcohol resin may be from 85 to 100 mol%, preferably at least 98 mol%. The polyvinyl alcohol resin may be polymerized to a degree of from 1,000 to 10,000, preferably from 1,500 to 5,000.

A layer of polyvinyl alcohol resin is used as a polarizer. The method of forming the polyvinyl alcohol resin layer is not particularly limited, and various methods of the related art can be used. The polyvinyl alcohol resin film may have a thickness of 10 to 150 μm, which is not particularly limited.

The process of the polarizer is to uniaxially stretch the polyvinyl alcohol film, dye and absorb with a dichroic dye, treat with a boric acid solution, clean and dry.

The process of uniaxially stretching the polyvinyl alcohol film can be carried out before, at the same time as, or after the dyeing. When uniaxial stretching is performed after dyeing, it may be carried out before boric acid treatment or during boric acid treatment. Obviously, uniaxial stretching can be carried out in multiple steps. The uniaxial stretching may be a dry stretching which is stretched in the atmosphere or a wet stretching which is stretched after being expanded by a solvent. Usually, the draw ratio is 3 to 8 times.

For the process of dyeing a stretched polyvinyl alcohol film by a dichroic dye, a method of immersing a polyvinyl alcohol film with a solution containing a dichroic dye can be used. Iodine or dichroic dyes are examples of dichroic dyes. Further, the polyvinyl alcohol film is preferably infiltrated to be swollen before dyeing.

When iodine is used as a dichroic dye, a dyeing method in which a polyvinyl alcohol film is immersed in a dyeing solution containing iodine or potassium iodide can be usually used. Usually, the iodine content of the dyeing solution is 0.01 to 1 part by weight with respect to 100 parts by weight of water (distilled water), and the potassium iodide content is 0.5 to 20 parts by weight with respect to 100 parts by weight of water. Usually, the dyeing solution temperature is 20 to 40 ° C, and the infiltration time, for example, the dyeing time is 20 to 1800 seconds.

When the dichroic organic dye is used as a dichroic dye, a dyeing method in which a polyvinyl alcohol film is immersed in a dye solution containing a soluble dichroic organic dye can be used. The dichroic organic dye content of the dyeing solution is usually from 1 × 10 ^-4 to 10 parts by weight, preferably from 1 × 10 ^-3 to 1 part by weight, per 100 parts by weight of water. The dyeing solution may further contain an inorganic salt such as sodium sulfate. The dyeing solution temperature is usually from 20 to 80 ° C, and the infiltration time, for example, the dyeing time is usually from 10 to 1,800 seconds.

The process of treating boric acid for the dyed polyvinyl alcohol film can be carried out by immersing the film in a solution containing boric acid. Usually, the boric acid content of the solution containing boric acid is 2 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. When iodine is used as the dichroic dye, the boric acid-containing solution preferably contains potassium iodide, and the content is usually 0.1 to 15 parts by weight, preferably 5 to 12 parts by weight, per 100 parts by weight of water. The temperature of the solution containing boric acid is 50 ° C or more, preferably 50 to 85 ° C, more preferably 60 to 80 ° C, and the infiltration time is 60 to 1,200 seconds, preferably 150 to 600 seconds, more preferably 200 to 400 seconds.

After the boric acid treatment, the polyvinyl alcohol film was cleaned and dried. Cleaning can be carried out by immersing a boric acid treated polyvinyl alcohol film in water. The clean water temperature is 5 to 40 ° C and the infiltration time is 1 to 120 seconds. After cleaning, it is dried to obtain a polarizer. Usually, the drying can be carried out using a hot air dryer or a far infrared ray heater, and the drying temperature is 30 to 100 ° C, preferably 50 to 80 ° C, and the drying time is 60 to 600 seconds, preferably 120 to 600 seconds.

The polarizer may have a thickness of 5 to 40 μm.

The uniaxially stretched positive A plate of the present invention has a coplanar retardation (R) of 10 to 100 nm. The positive A plate has a refractive index (NZ) of 0.9 to 1.1.

The positive A plate coplanar retardation (RO) is an optimum range for ensuring a wide viewing angle, and may be 10 nm to 100 nm, preferably 10 nm to 80 nm, more preferably 10 nm to 50 nm.

Further, the positive A plate refractive index (NZ) is theoretically 1.0, but it is difficult to produce a positive A plate having a refractive index of 1.0 for the film process. Therefore, in general, a refractive index (NZ) range which can exhibit substantially the same properties as a refractive index of 1.0 is regarded as a positive A plate.

In the present invention, the positive A plate refractive index (NZ) is assumed to be 0.9 to 1.1.

For all wavelengths in the visible range, the positive A plate optical properties are defined by Equations 1 through 3 below.

If the wavelength of the light source is not specifically stated, the optical properties of 589 nm are indicated. In this context, Nx is the refractive index of the axis with the largest refractive index of light oscillating in the coplanar direction, Ny is the refractive index of the light oscillating in the direction perpendicular to the coplanar direction, and Nz is the refractive index of the light oscillating in the thickness direction. 2 is expressed as follows.

[Formula 1]

Rth=[(Nx+Ny)/2-Nz]×d

(where Nx and Ny are the refractive indices of the light oscillating in the coplanar direction and Nx Ny, Nz is the refractive index of light oscillating in the film thickness direction, and d is the film thickness).

[Formula 2]

R0=(Nx-Ny)×d

(where Nx and Ny are the refractive indices of the light oscillating in the coplanar direction, d is the film thickness, Nx Ny).

[Formula 3]

NZ=(Nx-Nz)/(Nx-Ny)=Rth/R0+0.5

(where Nx and Ny are the refractive indices of the light oscillating in the coplanar direction and Nx Ny, Nz is the refractive index of light oscillating in the film thickness direction, and d is the film thickness).

Rth is the thickness retardation, showing the phase difference of the coplanar average refractive index in the thickness direction, which is not a substantial difference but a reference value.

R0 is a coplanar retardation, which is the substantial phase difference when light penetrates the film in the normal direction (vertical direction).

Furthermore, NZ is the refractive index from which the type of sheet of the compensation film can be resolved.

The type of the compensation film is referred to as an A plate when the optical axis having no phase difference exists in the coplanar direction of the film, the C plate when the optical axis exists in the vertical direction of the plane, and the biaxial plate when the optical axis exists.

The positive A plate of the present invention can be made of a film having positive (+) refractive index characteristics. In particular, optional free TAC (cellulose triacetate), COP (cycloolefin polymer), COC (cycloolefin copolymer), PET (polyethylene terephthalate), PP (polypropylene), PC Among the groups consisting of (polycarbonate), PSF (polyfluorene), and PMMA (polymethyl methacrylate).

The positive A plate of the present invention is produced by stretching a film having a positive refractive index in one direction to maintain resistance to physical changes in the external environment. The macromolecular arrangement of the membrane is deformed, and the stretched film is less sensitive to physical changes in the external environment than the unstretched film.

Stretching is divided into fixed end stretching and free end stretching. The fixed end stretching is a fixed length in a direction excluding the stretching direction when the film is stretched. The free end stretching imparts a degree of freedom in a direction excluding the stretching direction when the film is stretched.

The positive A plate of the present invention is uniaxially stretched at the free end.

Furthermore, the additional process can be applied to control the slow axis direction, the phase difference value, and the NZ value, and the additional process is a common process that is not particularly limited.

The uniaxially stretched positive A-plate is set such that the slow axis is parallel to the polarizer absorption axis of the lower polarizer. The polarizing plate component of the polarizer made of polyvinyl alcohol having polarization function is most sensitive to the external environment of high temperature and high humidity. Therefore, by making the slow axis of the positive A plate parallel to the absorption axis of the polarizer, the physical resistance to the external environment can be improved.

Since the polarizer is mechanically weak, the protective film means to protect the film of the polarizer.

The protective film can have excellent transparency, mechanical strength, thermal stability, water repellency, and isotropic properties. The moisture permeability of the protective film varies depending on the kind of the resin, and it is preferable to select the protective film in consideration of the moisture permeability.

The protective film may be selected from thermoplastic resins such as polyester resins such as polyethylene terephthalate, polyethylene isophthalate, polyethylene phthalate, polybutylene terephthalate ; cellulose resins such as cellulose diacetate and cellulose triacetate; polycarbonate resins; acrylic resins such as polymethyl methacrylate and polyethyl methacrylate; styrene resins such as polystyrene and acrylonitrile -styrene copolymer; polyolefin resin such as polyethylene, polypropylene, polyolefin having a ring-shaped or norbornene structure; olefin resin such as ethylene-propylene copolymer; vinyl chloride resin; polyimide resin such as nylon And aromatic polyamidamine; melamine resin; polyether oxime resin; oxime resin; polyether ketone resin; polyphenylene sulfide resin; vinyl alcohol resin; dichloroethylene resin; vinyl butyral resin; allyl Resin; polyacetal resin; epoxy resin, film can also be composed of a mixture of thermoplastic resins. Further, the film may be formed using a thermosetting resin of methyl acrylate, polyurethane, epoxy, enamel resin or an ultraviolet curable resin.

The protective film has a thermoplastic resin content of 50 to 100% by weight, preferably 50 to 99% by weight, more preferably 60 to 98% by weight, most preferably 70 to 97% by weight. When the content is less than 50% by weight, the unique high transmittance of the thermoplastic resin cannot be sufficiently achieved.

Polarizers are typically fabricated by roll-to-roll processes and sheet-to-sheet processes. Considering the yield and efficiency in the process, it is best to apply the shaft-to-axis process because the PVA polarizer absorption axis is fixed in the MD direction, so it is particularly effective.

Since the coupled polarizing plate group of the present invention has excellent resistance to physical changes even when exposed to a high temperature and high humidity environment, the phase difference compensation effect of the initial design can be maintained. For example, after three days in an environment exposed to 50 ° C and 80% RH, the change in coplanar retardation (RO) is less than 0.5 nm, and the change in thickness retardation (Rth) is less than 1 nm.

The coupled polarizing plate group of the present invention can be used for an IPS mode liquid crystal display.

Assuming that the counterclockwise direction from the visible side right horizontal direction is the normal (+) direction, and no voltage is applied, a liquid crystal cell having a liquid crystal alignment direction of 90° (S-IPS) or a liquid crystal alignment direction of 0° (FFS) can be used.

The panel phase difference (Δn x d) of the S-IPS is defined by the following formula 4, in the range of 300 nm to 330 nm at a wavelength of 589 nm, and in the range of 370 to 400 nm at an FFS.

[Formula 4]

Δn×d=(n _e -n _o )×d

(where n _e is the extraordinary ray index of the liquid crystal, n _o is the refractive index of the ordinary ray, d is the cell gap, Δn and d are scalar, non-vector).

The upper polarizing plate absorption axis of the present invention is perpendicular to the lower polarizing plate absorption axis. When viewed from the visible side, the lower polarizer absorption axis is preferably in the vertical direction.

When the absorption axis of the polarizer near the backlight unit is vertically aligned, the light passing through the lower polarizer is horizontally polarized. The horizontally polarized light passes through the panel voltage and is switched to the liquid crystal cell in the white state, and the light changes vertically, passing through the upper polarizing plate on the visible side in the horizontal direction. In this case, a person carrying polarized sunglasses that absorbs the axis in the horizontal direction of the visible side will find light leaving the liquid crystal display.

However, when the absorption axis of the polarizing plate near the backlight unit is in the horizontal direction, the person carrying the polarizing sunglasses does not see the image.

Furthermore, for large liquid crystal displays, a horizontally wide liquid crystal display is used so that the image can be clearly seen from the visible side. This is to consider that the main field of view of the person is wider than the vertical direction in the horizontal direction. For general liquid crystal displays, the liquid crystal display is manufactured in a ratio of 4:3 or 16:9, except for liquid crystal displays having special purposes (such as advertising).

The effect of compensating the viewing angle of the present invention can be understood by presenting a change in polarization state of each optical layer on a Poincare sphere.

The Bangka ball exhibits a change in polarization state at a particular viewing angle. A change in polarization state can occur when light passes through the various optical elements of the liquid crystal display. The light entering the liquid crystal display is polarized light, and the incident light exits through the inside of the liquid crystal display at a specific angle of view.

A particular perspective of the present invention is the F=45° and θ=60° directions of the semicircular coordinate system of FIG. The wavelength distribution can be seen by a change in the polarization state on the ball that presents the light that leaves all wavelengths in this direction.

Further, from FIGS. 7A to 7C, depending on the transmittance of the wavelength, the color sensation at a specific viewing angle (inclined surface) after exposure to a high temperature and high humidity environment can be seen.

Since the present invention has a specific positive A plate stretched on the upper and lower polarizing plates, the uniform transmittance exhibits a wavelength within 300 to 780 nm, so that the color feeling is excellent not only on the front side but also on the inclined surface.

Hereinafter, preferred embodiments will be described with reference to examples and comparative examples to better understand the present invention. However, it is to be understood by those skilled in the art that the present invention may be modified and modified without departing from the scope and spirit of the invention. .

Instance

Example 1

In the structure of Fig. 1, actual data of the optical film, liquid crystal cell, and backlight according to the present invention were measured on TECH WIZ LCD 1D (SANAYI SYSTEM, Korea). The structure of Fig. 1 will be described in detail below.

Example 1 includes a lower polarizing plate 10 and an IPS mode liquid crystal cell 30 from the backlight (when the counterclockwise direction from the right horizontal direction of the visible side is the normal (+) direction, no voltage is applied, and the liquid crystal alignment direction is 90°), Polarizing plate 20. The lower polarizing plate 10 is formed by stacking the positive A plate 14, the polarizing plate 11, and the protective film 13 from the liquid crystal cells. The upper polarizing plate 20 is formed by stacking the positive A plate 24, the polarizing plate 21, and the protective film 23 from the liquid crystal cells 30.

When the counterclockwise direction from the right horizontal direction of the visible side is the normal (+) direction, the absorption axis 12 of the polarizer 11 of the lower polarizing plate 10 is at 90°, and the absorption axis 22 of the polarizer 21 of the upper polarizing plate 20 is at 0. °.

The LCD cell is the LC420WU5 of the 42-inch panel of LG Display.

The optical film and backlight unit used in this example each have the following optical properties.

The stretched PVA is dyed with iodine so that the polarizing plates 11 and 21 of the lower polarizing plate 10 and the upper polarizing plate 20 have a polarizing function. The polarizer polarization function has a luminance degree of polarization of 99.9% or more and a luminance group transmittance of 41% or more in the visible light region of 370 to 780 nm.

When the transmittance of the transmission axis with wavelength is TD(λ), the transmittance of the absorption axis with wavelength is MD(λ), and the luminance compensation value defined by JIS Z 8701:1999 is At (λ), the degree of polarization and the luminance group transmittance are defined by the following formulas 5 to 9, where S(λ) is the source spectrum and the source is the C source.

At a 589.3 nm light source, the positive A plate 24 of the upper polarizing plate and the positive A plate 14 of the lower polarizing plate have a coplanar retardation (RO) of 50 nm, a thickness retardation (Rth) of 25 nm, and a refractive index (NZ) of 1.0.

The absorption axis 22 of the upper polarizer 21 is parallel to the fast axis 25 of the positive A plate 24, and the absorption axis 12 of the lower polarizer 11 is parallel to the fast axis 15 of the positive A plate 14.

The positive A-plate 24 of the upper polarizing plate and the positive A-plate 14 of the lower polarizing plate are manufactured by the uniaxial stretching process of the stretched free end to have desired optical properties.

Further, the outer protective films 13 and 22 of the upper and lower polarizing plates 10 and 20 are made of TAC (cellulose triacetate) having a thickness retardation (Rth) of 50 nm for 589.3 nm incident light. The actual data of the 32-inch TV LC320WX4 model (LG. PHILIPS LCD) is used for the backlight unit 50.

Example 2

Example 2 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 50 nm, a thickness retardation (Rth) of 25 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 80 nm, a thickness retardation (Rth) of 40 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 3

Example 3 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 80 nm, a thickness retardation (Rth) of 40 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 80 nm, a thickness retardation (Rth) of 40 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 4

Example 4 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 80 nm, a thickness retardation (Rth) of 40 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 50 nm, a thickness retardation (Rth) of 25 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 5

Example 5 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 30 nm, a thickness retardation (Rth) of 15 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 30 nm, a thickness retardation (Rth) of 15 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 6

Example 6 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 10 nm, a thickness retardation (Rth) of 5 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 10 nm, a thickness retardation (Rth) of 5 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 7

Example 7 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 100 nm, a thickness retardation (Rth) of 50 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 100 nm, a thickness retardation (Rth) of 50 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Example 8

Further, Example 8 was carried out in the same manner as in Example 1, using the positive A plate 24 of the upper polarizing plate and the positive A plate 14 of the lower polarizing plate to manufacture an IPS mode liquid crystal display having a coplanar retardation (RO) of 50 nm, thickness The retardation (Rth) was 20 nm and the refractive index (NZ) was 0.9.

Example 9

Further, Example 9 was carried out in the same manner as in Example 1, using the positive A plate 24 of the upper polarizing plate and the positive A plate 14 of the lower polarizing plate to manufacture an IPS mode liquid crystal display having a coplanar retardation (RO) of 50 nm, thickness The retardation (Rth) was 30 nm and the refractive index (NZ) was 1.1.

Comparative example 1

Comparative Example 1 was carried out in the same manner as in Example 1, using an isotropic protective film to fabricate an IPS mode liquid crystal display having a coplanar retardation (RO) of 1 nm and a thickness retardation (Rth) of 2 nm instead of the upper polarizing plate and the lower polarizing film. The positive A plates 14 and 24 of the plate.

Comparative example 2

Comparative Example 2 was carried out in the same manner as in Example 1, and the IPS mode liquid crystal display was manufactured such that the absorption axis 22 of the upper polarizer 21 and the fast axis 25 of the positive A plate 24 were perpendicular, and the absorption axis 12 of the lower polarizer 11 and the positive A plate 14 were The fast axis 15 is vertical.

Comparative example 3

Comparative Example 3 was carried out in the same manner as in Example 1, in which the positive A plate 24 of the upper polarizing plate 20 had a coplanar retardation (RO) of 50 nm, a thickness retardation (Rth) of 25 nm, and a refractive index (NZ) of 1.0.

Further, an IPS mode liquid crystal display was manufactured using an isotropic protective film having a coplanar retardation (RO) of 1 nm and a thickness retardation (Rth) of 2 nm instead of the positive A plate 14 of the lower polarizing plate 10.

Comparative example 4

Comparative Example 4 was carried out in the same manner as in Example 1, using an isotropic protective film having a coplanar retardation (RO) of 1 nm and a thickness retardation (Rth) of 2 nm instead of the positive A plate 14 of the upper polarizing plate 20.

Further, an IPS mode liquid crystal display having a coplanar retardation (RO) of 50 nm, a thickness retardation (Rth) of 25 nm, and a refractive index (NZ) of 1.0 was produced using the positive A plate 14 of the lower polarizing plate 10.

Experimental example

The characteristics of the coupled polarizing plate group and the liquid crystal display manufactured by the examples and comparative examples were measured by the following methods.

(1) Degree of polarization of the liquid crystal display

The degree of polarization of a 30 x 30 mm polarizing plate was measured using a V7100.

(2) The amount of phase difference change of the coupled polarizer group

The coupled polarizing plate group was placed in a chamber (temperature/high humidity chamber) at a temperature of 50 ° C and 80% RH to measure the phase difference of the coupled polarizing plate group, and the phase difference was measured three days later.

(3) The polarization state of the liquid crystal display changes

The change in polarization state in the oblique directions of f = 45° and θ = 60° was measured on a Bangka ball.

(4) Whether pollution occurs in the coupled polarizer group

The coupled polarizing plate group was placed in a chamber of 50 ° C temperature and 80% RH (high temperature / high humidity chamber) to measure the phase difference of the coupled polarizing plate group, and visually checked for contamination after three days.

[Base of pollution generation]

○: very little pollution

Δ: ordinary

×: a lot of pollution

Figure 5 presents the measurement of the degree of polarization of the liquid crystal displays manufactured in Examples 1 to 7 and Comparative Examples 1 to 4. It can be seen that the degree of polarization exhibits the same range regardless of whether or not stretching is performed.

Fig. 6 presents phase difference changes for the coupled polarizing plate groups of Examples 1 to 7 and Comparative Examples 1 to 4. It can be seen from Fig. 6 that the amount of change in the coplanar retardation and the thickness retardation greatly differs depending on whether or not stretching is performed before and after the coupled polarizing plate group is placed in the high temperature and high humidity chamber. It can be seen that the amount of change in the phase difference when using the unstretched film is much greater than when the stretched film is used.

Further, it can be seen that the amount of change in the phase difference is greater in the combination of the stretched film and the unstretched film than in the combination of the stretched film.

Further, Table 1 below shows the degree of contamination generation of the coupled polarizing plate groups of Examples 1 to 7 and Comparative Example 1. It can be seen from Table 1 that the degree of contamination generation is much smaller in Examples 1 to 7 using the coupled polarizing plate of the present invention.

7A to 7C show the transmittance change measurement with wavelength after the IPS liquid crystal display manufactured in Example 1 and Comparative Examples 1 and 3 was placed in a high temperature and high humidity chamber. In the figure, the wavelength of the blue path is 430 nm, the wavelength of the red path is 630 nm, and the wavelength of the green path is 430 nm.

Referring to Fig. 7, the coupled polarizing plate group of Example 1 exhibited uniform transmittance at all wavelengths (300 to 780 nm) even after being placed in a high temperature and high humidity chamber. On the other hand, it can be seen from Comparative Examples 1 and 3 that the transmittance differs depending on the wavelength. Therefore, since the transmittance was low with a change in wavelength, Example 1 had an excellent color feeling on the front and inclined surfaces.

Fig. 8A presents the polarization state change of the liquid crystal display manufactured in Example 6 and Comparative Examples 1 and 4. It can be seen from Fig. 8A that Comparative Example 1 and Example 6 using the isotropic film exhibited the same brightness. 8A shows a 550 nm light on a Bangka ball sequentially passing through a polarizer 11 (polarization state 1) of the first polarizing plate 10, a positive A plate (14) (polarization state 2), a liquid crystal cell 30 (polarization state 3), The polarization state of the positive A-plate 24 (polarization state 4) changes.

Figure 8B presents the polarization state of the liquid crystal display fabricated in Example 5. It can be seen from the polarization state of Fig. 8B that the luminance is the same as that of Fig. 8A (see Fig. 9).

Fig. 8C shows the polarization state of the liquid crystal display manufactured in Comparative Example 2. It can be seen from Fig. 8C that the polarization state is very different from the present invention because the polarizer absorption axis and the film fast axis are perpendicular to each other. It is expected that the polarization state of Figure 8C will make a large difference in ensuring a change in viewing angle and brightness level.

Fig. 9 shows the results of simulating the transmittances of all the light directions from Examples 1 to 7 and Comparative Example 1, and it can be seen that the luminance is the same as Comparative Example 1 using the isotropic film.

Figures 10 through 13 present changes in the polarization state and transmittance of all light directions from the IPS mode liquid crystal displays fabricated in Examples 8 and 9, which can be seen to be very similar to Example 5.

That is, it can be seen that the plate having a refractive index (NZ) of 0.9 and 1.1 exhibits substantially the same characteristics as a positive A plate having a refractive index (NZ) of 1.0.

Although the present invention has been described with reference to the preferred embodiments thereof, it is understood by those skilled in the art that various modifications and changes can be made without departing from the scope of the invention as defined by the appended claims.

10. . . Lower polarizer

11. . . Polarizer

12. . . Absorption axis

13. . . Protective film

14. . . Positive A board

15. . . Fast axis

20. . . Upper polarizer

twenty one. . . Polarizer

twenty two. . . Absorption axis

twenty three. . . Protective film

twenty four. . . Positive A board

25. . . Fast axis

30. . . IPS liquid crystal cell

40. . . Backlight

1 is a perspective view showing the structure of an IPS mode liquid crystal display according to the present invention.

Figure 2 is a schematic diagram showing the refractive index of a compensation film in accordance with the present invention.

Figure 3 is a schematic view showing the MD direction in the process to reveal the stretching direction of the compensation film and the polarizing plate according to the present invention.

Figure 4 is a schematic diagram showing the factors represented by f and θ of the coordinate system of the present invention.

Figure 5 presents polarization measurements for the coupled polarizers of Examples 1 to 7 and Comparative Examples 1 to 4 of the present invention.

Fig. 6 presents polarization difference changes for the coupled polarizing plates of Examples 1 to 7 and Comparative Examples 1 to 4 of the present invention.

7A to 7C present changes in transmittance measured with respect to wavelengths after the IPS mode liquid crystal display manufactured by Example 1 (7A) and Comparative Examples 1 (7B) and 3 (7C) were placed in a high temperature and high humidity chamber.

8A to 8C present polarization state changes of the IPS mode liquid crystal display fabricated in Example 6, Comparative Examples 1 and 4 (8A), Example 5 (8B), and Comparative Example 2 (8C).

Figure 9 shows the transmittance of all IPS mode liquid crystal displays manufactured by Examples 1 to 7 and Comparative Example 1 from all light directions.

10 and 11 show changes in the polarization state and transmittance of all IPS mode liquid crystal displays manufactured by Example 8 of the present invention from all light directions.

Figures 12 and 13 show changes in the polarization state and transmittance of all IPS mode liquid crystal displays manufactured by Example 9 of the present invention from all light directions.

10. . . Lower polarizer

11. . . Polarizer

12. . . Absorption axis

13. . . Protective film

14. . . Positive A board

15. . . Fast axis

20. . . Upper polarizer

twenty one. . . Polarizer

twenty two. . . Absorption axis

twenty three. . . Protective film

twenty four. . . Positive A board

25. . . Fast axis

30. . . IPS liquid crystal cell

40. . . Backlight

Claims (7)

A coupled polarizing plate set comprises: an upper polarizing plate, wherein a protective film, a polarizing plate, a uniaxially stretched positive A plate, and a lower polarizing plate are sequentially stacked; wherein the uniaxially stretched positive A plate, the polarizer, and the like are sequentially stacked; The protective film, wherein the positive A plate of the upper polarizing plate and the lower polarizing plate has a coplanar retardation (RO) of 10 to 100 nm each, and a slow axis thereof is parallel to an absorption axis of the adjacent polarizer. According to the coupled polarizing plate group of claim 1, wherein the positive A plate has a coplanar retardation (RO) of 10 to 80 nm. According to the coupled polarizing plate group of claim 2, wherein the positive A plate has a coplanar retardation (RO) of 10 to 50 nm. According to the coupled polarizing plate group of claim 1, wherein the positive A plate has a refractive index (NZ) of 0.9 to 1.1. According to the coupled polarizing plate group of claim 1, wherein the positive A plate is selected from the group consisting of TAC (cellulose triacetate), COP (cycloolefin polymer), COC (cycloolefin copolymer), PET (polyethylene terephthalate) It is made up of a group consisting of formate), PP (polypropylene), PC (polycarbonate), PSF (polyfluorene), and PMMA (polymethyl methacrylate). A coupled polarizing plate group according to claim 1, wherein the absorption axes of the upper polarizing plate and the lower polarizing plate are perpendicular to each other. A coplanar switching mode liquid crystal comprising the coupled polarizing plate group according to any one of claims 1 to 6.