KR20100071254A - Bottom plate polarizer and in-plane switching mode liquid crystal display comprising the same - Google Patents

Abstract

PURPOSE: A bottom plate polarizer and in-plane switching mode liquid crystal display comprising the same are provided to have wider view angle. CONSTITUTION: A liquid crystal cell(30) is filled with liquid between two glass substrates. A liquid crystal has positive dielectric constant anisotropy. An active matrix drive electrode comprises electrode pair. The active matrix drive electrode is formed on neighboring surface of liquid cell. An absorption axis of lower polarization board and an absorption axis of the upper polarization board are perpendicularly arranged to each other.

Description

Lower plate polarizer and planar switching mode liquid crystal display including the same {BOTTOM PLATE POLARIZER AND IN-PLANE SWITCHING MODE LIQUID CRYSTAL DISPLAY COMPRISING THE SAME}

The present invention provides a planar switching using a negative biaxial A plate and a positive biaxial A plate having a specific optical property from a liquid crystal cell side, and a polarizer stacked in the order of a polarizer and a protective layer in order to ensure a wide viewing angle. PLANE SWITCHING, hereinafter referred to as 'IPS').

Liquid crystal display (LCD) is widely used as a popular image display device. However, despite its many excellent features, a narrow viewing angle is pointed out as a representative disadvantage. Therefore, a technology for securing a wide viewing angle by applying a functional optical film such as a liquid crystal driving mode and a retardation film has emerged. In particular, a liquid crystal display device using an IPS mode as a dual liquid crystal driving mode improves the viewing angle characteristics. It is well known that it has an excellent effect.

In the field switching mode (IPS mode), a liquid crystal is driven by using a lateral electric field. Twisted nematic (TN) and vertical alignment (VA) modes are different in the direction of the liquid crystal and the electric field. While vertically formed [vertical alignment] between the upper and lower plates, the IPS mode uses a horizontally oriented liquid crystal to form the direction of the electric field parallel to the liquid crystal array direction.

In the plane switching mode, since the liquid crystal molecules have a substantially horizontal and uniform arrangement on the substrate surface in the non-driven state, the optical characteristics of the liquid crystal when the transmission axis of the lower plate and the direction of the fast axis of the liquid crystal molecules coincide with each other at the front side. Since the transmission axis and the fastening axis of the liquid crystal coincide on the slope, even if the light passing through the lower polarizing plate passes through the liquid crystal, the polarization state does not change and the liquid crystal layer can pass through the liquid crystal layer as it is. By arranging the planar polarizers, it is possible to display a dark state relatively superior to other modes in the non-driven state. In addition, when the transmission axis of the lower plate and the slow axis direction of the liquid crystal molecules coincide with each other at the front side, a change in polarization state occurs at the slope, but since the transmittance of the upper plate polarizer is maintained at the same polarization state in the electric field, the neutral is maintained. Since one color can be maintained and the transmittance is maintained as described above, it is possible to display a relatively excellent black state compared to other modes.

The planar switching mode liquid crystal display device generally obtains a relatively wide viewing angle compared to other modes without using an optical film, and thus has an image quality and a viewing angle uniform throughout the screen. Therefore, the planar switching mode liquid crystal device is mainly used in high-end models of 18 inches or more.

Conventional liquid crystal display device using a plane switching mode requires a polarizing plate for polarizing light on the outside of the liquid crystal cell containing a liquid crystal, a protective film made of a triacetyl cellulose (TAC, Triacetylcellulose) film on one side or both sides of the polarizing plate It is provided in order to protect this polarizer PVA. In this case, when the liquid crystal expresses a black state, the light polarized by the polarizer provided in the lower plate is elliptically polarized by triacetylcellulose on the inclined surface instead of the front surface, and the elliptically polarized light is amplified in the liquid crystal cell. At the same time, there is a problem in that light has various colors.

Moreover, in recent years, as image display devices such as large TVs using the planar switching mode method have been manufactured, wide viewing angle characteristics are required. Therefore, in the planar switching mode liquid crystal display (IPS-LCD), in order to secure a wide viewing angle, an isotropic protective layer (isotropic TAC) is used between the polarizer (PVA) and the liquid crystal cell to eliminate elliptical polarization due to TAC. It is pointed out that it is difficult to secure a wide viewing angle because the light leakage phenomenon occurs because the absorption axis of the polarizer is still not compensated for by improving the color.

Accordingly, a new polarizer configuration capable of mass production is urgently required by easily manufacturing a composite polarizer including a phase difference film by using a roll-to-roll production form with various compensation configurations to secure an excellent wide viewing angle.

The present invention improves the problem that it is difficult to realize a perfect wide viewing angle in the dark state due to light leakage caused by the absorption axis compensation of the polarizer of the conventional IPS mode liquid crystal display device using the isotropic protective layer.

Accordingly, the present invention is a method of changing the configuration of the compensation film by the lower polarizing plate containing a retardation film having a variety of laminated structure and retardation value design to match the absorption axis of the upper polarizing plate to the polarization plane of the polarized light passing through the lower polarizing plate By doing the polarizer absorption axis compensation of the lower plate to secure a wider viewing angle than the conventional, and to propose a lower plate polarizing plate that can be produced using a roll-to-roll production mode. Specifically, the negative polarizing A plate and positive biaxial A plate having a specific optical property from the liquid crystal cell side, and a lower polarizing plate in which a polarizer and a protective layer are stacked in this order are used in the planar switching mode liquid crystal display device, so that the front and inclination angles are used. The present invention provides a planar switching mode liquid crystal display device that provides a wider viewing angle than that of the prior art by improving contrast characteristics and minimizing color change due to a change in viewing angle in a dark state.

The present invention is a lower plate polarizing plate for a planar switching (IPS) mode in which a negative biaxial A plate, a positive biaxial A plate, a polarizer and a protective layer are stacked from a liquid crystal cell side, and the negative biaxial A plate has a front phase difference value ( R0) is from 20 to 100 nm, the refractive index ratio (NZ) is 1.01? NZ? 3.5, and the slow axis is parallel to the absorption contraction of the adjacent polarizer; The positive biaxial A plate has a front phase difference value R0 of 40 to 120 nm, a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and a slow axis is characterized by a lower polarizing plate configured to be parallel to an absorption axis of an adjacent polarizer. have.

In addition, the present invention has another feature in an on-plane switching (IPS) mode liquid crystal display including the lower polarizing plate.

The planar switching mode liquid crystal display device according to the present invention applies a negative biaxial A plate and a positive biaxial A plate having a specific optical property from the liquid crystal cell side, and a lower polarizing plate laminated in the order of a polarizer and a protective layer. By enabling the implementation of the dark state can have a wider viewing angle than conventional, mass production is easy.

The present invention relates to a lower polarizing plate capable of realizing a dark state at an entire viewing angle by compensating for light leakage in a liquid crystal cell when applied to an area switching mode liquid crystal display. Such a lower plate polarizing plate is laminated | stacked in the order of a negative biaxial A plate, a positive biaxial A plate, a polarizer, and a protective layer from the liquid crystal cell side.

The term "negative biaxial (A-plate) A plate" of the present specification refers to a positive biaxial optical element whose refractive index distribution satisfies Nx> Ny> Nz, and is called "negative B plate." In this case, the positive biaxial optical element in the present invention refers to a material having a large refractive index in the stretching direction. In addition, the term “positive biaxial A plate” refers to a negative biaxial optical element satisfying Nz> Nx> Ny, and is also called a “positive B plate”. In this case, the negative bi-axial optical element in the present invention refers to a material whose refractive index decreases in the stretching direction.

The negative biaxial A plate disposed on the lower polarizing plate has a front phase difference value (R0) of 20 to 100 nm, a refractive index ratio (NZ) of 1.01 ≤ NZ ≤ 3.5, and exhibits excellent wide viewing angle characteristics in consideration of the phase difference expression range in the process. Preferably, the front phase difference value R0 is 25 to 95 nm, the refractive index ratio NZ is 1.1 ≤ NZ ≤ 3.2, more preferably the front phase difference value R0 is 30 to 90 nm, and the refractive index ratio NZ It is better to keep 1 < The slow axis of this negative biaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer on the viewing side.

The positive biaxial A plate (positive B plate) laminated on the lower surface of the negative biaxial A plate from the liquid crystal cell has a front phase difference value R0 of 40 to 120 nm and a refractive index ratio NZ of -1.2 ≤ NZ ≤ -0.01. In order to maintain and exhibit excellent wide viewing angle characteristics in consideration of the phase difference expression range in the process, the front phase difference value R0 is preferably 45 to 115 nm, and the refractive index ratio (NZ) is -1.1 to -0.1, more preferably. In the following, the front phase difference value R0 is 50 to 110 nm, and the refractive index ratio NZ is preferably maintained at -1 to -0.2.

Such a positive biaxial A plate may be a structure in which polymethyl methacrylate (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) are sequentially stacked, or at least one modified polycarbonate (PC). Can be. The slow axis of this positive biaxial A plate is configured to be parallel to the absorption axis of the adjacent polarizer on the viewing side.

Said negative biaxial A plate and positive biaxial A plate are independent of each other and can be applied to this invention as long as it satisfies the optical characteristic of the range which this invention defines. Specifically, triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and poly Methyl methacrylate (PMMA) can be used that is prepared from the one selected from the group consisting of.

A lower polarizing plate manufactured according to the present invention is laminated to form an in-plane switching (IPS) mode liquid crystal display device. In this case, the liquid crystal display of the present invention includes aligning the liquid crystal in a multi-domain or dividing it into multiple regions by a voltage applied thereto. According to the mode of an active matrix driving electrode including an electrode pair, an LCD may be classified into super-in-plane-switching (IPS) and fringe-field-switching (FFS). In the IPS-LCD of the present invention, the liquid crystal alignment is FFS (Fringe-Field-Switching), and the liquid crystal alignment is parallel to the absorption axis of the polarizer of the upper polarizing plate.

The top plate polarizer of the planar switching mode liquid crystal display is generally used in the art, and uses an isotropic protective layer applied to secure a wide viewing angle. Specifically, the liquid crystal cell is configured in the order of an isotropic protective layer, a polarizer, and a protective layer, and the polarizer absorption axis of the lower polarizer and the polarizer absorption axis of the upper polarizer are orthogonal to each other.

The isotropic protective layer and the protective layer constituting the upper polarizing plate, and the material forming the protective layer constituting the lower polarizing plate may be used independently of each other commonly used in the art, specifically triacetyl cellulose (TAC), Cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), polysulfone (PSF) and polymethyl methacrylate (PMMA) It may be used that is prepared as selected from. In this case, it is preferable that the isotropic protective layer has a front phase difference (RO) and a thickness direction phase difference (Rth) of less than 10 nm, preferably, an absolute value of less than 2 nm, and the protective layers of the upper and lower polarizing plates are optically based on the difference in refractive index. Since the property does not affect the viewing angle, the refractive index property is not particularly limited in the present invention.

The retardation films such as the negative biaxial A plate and the positive biaxial A plate and the isotropic protective layer of the upper polarizing plate constituting the lower polarizing plate may have a z-axis in the thickness direction and a x-axis in the direction of the in-plane refractive index as shown in FIG. When the vertical direction is referred to as the y-axis, when the refractive index corresponding to each direction is Nx, Ny, and Nz, the thickness direction phase difference Rth defined by Equation 1 below and the front phase difference R0 defined by Equation 2 below And the refractive index ratio NZ defined by the following equation (3). At this time, the characteristics of the retardation film are determined according to the size of the refractive index. When the refractive indices in the three axial directions are different from each other, there are two optical axes that do not cause retardation. This is called a biaxial retardation film. Optical properties of each film to be implemented in the present invention is a property of the light source 589.3nm, the light source range is a reference when referring to the optical properties in general, the value when the light source 589.3nm when there is no special description of the light source Say

Rth = [(Nx + Ny) / 2-Nz] × d

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

R0 = (Nx-Ny) × d

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

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

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

As described above, the present invention is to provide a lower polarizing plate having a superior viewing angle compensation effect and a planar switching mode liquid crystal display device using the same, which can be applied to mass production rather than the conventional abstract viewing angle compensation concept. The planar switching liquid crystal display device configured under the optical condition of the present invention satisfies the compensating relationship of the maximum transmittance in the dark state in the dark state of 0.1% or less, preferably 0.05% or less. The brightness of the brightest LCD currently produced is about 10000 nits using the vertical alignment mode (VA mode). The brightness is about 10000 nits × cos60 ° at a viewing angle of 60 °, and 0.05% of this is 2.5 nits. to be. Accordingly, the present invention is to implement the visibility of the omnidirectional transmittance of a level similar to that of the VA mode, which is relatively superior to the IPS mode while realizing the visibility of the omnidirectional transmittance equal to or higher than that of the liquid crystal display using the IPS mode.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view illustrating a basic structure of an IPS-LCD according to the present invention.

In the IPS mode LCD according to the present invention, the lower polarizer 10, the liquid crystal cell 30, and the upper polarizer 20 are stacked in the order of the backlight unit 40, and the lower polarizer 10 and the upper polarizer ( The protective layers 13 and 23 are positioned opposite to the liquid crystal cell of the polarizers 11 and 21 of the 20. The upper polarizing plate 20 has an isotropic protective layer 24 laminated on the liquid crystal cell side of the polarizer 21, and the lower polarizing plate 10 has a negative biaxial A plate 16 and a positive biaxial A plate 14 from the liquid crystal cell side. ) And the polarizer 21 are laminated in this order.

More specifically, the lower polarizing plate 10 includes a horizontally oriented liquid crystal cell 30 filled with a liquid crystal having a positive dielectric anisotropy (Δε> 0) between two glass substrates, and an upper polarizing plate 20. In one of the glass substrates of the liquid crystal cell 30, an active matrix drive electrode including an electrode pair is formed on an adjacent surface of the liquid crystal cell 30.

The liquid crystal cell 30 has a panel retardation value (Δn × d) defined by Equation 4 below in a range of 300 to 400 nm at a wavelength of 589 nm, and more preferably about 380 nm in the configuration of the present invention. When the voltage is applied to the IPS-LCD panel, the light is linearly polarized in the horizontal direction after passing through the lower polarizing plate 10 and passed through the liquid crystal cell 30 to be linearly polarized in the vertical direction so as to become bright. This is because the retardation value of the liquid crystal cell 30 of the panel should be half wavelength of 589 nm (the brightest monochromatic light felt by a person). At this time, it may be adjusted to be slightly longer or shorter than the half wavelength in order to be white (White Color).

Δn × d = (n _e -n _o ) × d

Where n _e represents the extraordinary refractive index of the liquid crystal, n _o represents the normal ray refractive index, and d represents the cell gap; Note. Δn and d are scalars, not vectors.

The negative biaxial A plate constituting the lower polarizer 10 may have a front phase difference (R0) of 20 to 100 nm and a refractive index ratio (NZ) of 1.01 ≤ NZ ≤ 3.5, and the slow axis absorbs adjacent polarizers. It is configured to be parallel to the axis.

The positive biaxial A plate may have a front phase difference value (R0) of 40 to 120 nm and a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and a slow axis is an absorption axis of light polarizer adjacent to the viewer side. It is configured to be parallel to. In a specific embodiment, polymethyl methacrylate (PMMA), polystyrene (PS) and polymethyl methacrylate (PMMA) are made of a three-layered film sequentially arranged through extrusion at a time to be perpendicular to the MD direction. It is prepared by stretching. In this case, the change of the refractive index through the stretching is mainly generated in the polystyrene (PS) layer and acts as a protective layer polymethyl methacrylate (PMMA) to protect the brittle polystyrene (PS) layer.

The absorption axis 12 of the lower polarizing plate 10 and the absorption axis 22 of the upper polarizing plate 20 are arranged perpendicular to each other, and included in the absorption axis 22 and the liquid crystal cell 30 of the upper polarizing plate 20. The alignment directions 31 of the liquid crystals are arranged parallel to each other.

FIG. 2 shows the relationship between the alignment direction of the liquid crystal and the absorption axis. The alignment direction 31 and the lower plate polarizer 10 and the upper plate which show the direction in which the liquid crystals are arranged when viewed from the viewer side (the opposite side of the backlight unit) are shown in FIG. The absorption axes 12 and 22 of the polarizing plate 20 are shown.

In the lower polarizing plate 10 and the upper polarizing plate 20, polyvinyl alcohol (PVA) layers 11 and 21, which are polarizers having polarization functions through stretching and dyeing, are positioned, respectively, and polyvinyl alcohol (PVA) of the lower polarizing plate. In the polyvinyl alcohol (PVA) layer 21 of the layer 11 and the upper polarizing plate 21, protective films 13 and 23 are positioned on opposite sides of the liquid crystal cell 30, respectively. At this time, the protective film 13 of the lower polarizing plate 10 and the protective film 23 of the upper polarizing plate 20 are not particularly limited in the present invention because the optical properties according to the refractive index does not affect the viewing angle. .

The upper polarizing plate 20 and the lower polarizing plate 10 of the present invention are manufactured by applying a roll to roll method which is easy to mass produce. Figure 4 is a schematic diagram illustrating the MD direction in the roll-to-roll manufacturing process with reference to this as follows.

The upper and lower polarizing plates 10 and 20 are made of a combination of various optical films, and each optical film is in a roll state before being bonded to the composite polarizing plate. The direction in which the film is unwound or wound in the roll is called MD (Machine Direction) direction. In the case of the upper polarizing plate 20, the directions of the protective layer 23 and the isotropic protective layer 24 have no influence on optical performance, so roll to roll production is possible, and in the case of the lower polarizing plate 20, the protective layer It is irrelevant to the direction of (13) and roll to roll production is possible by matching the MD directions of the polarizer 11, the positive biaxial A plate 14 and the negative biaxial A plate 16. . Specifically, the absorption axis 12 of the polarizer 11 in the lower polarizing plate 10 is in the MD direction, which is the MD PVA through the MD direction stretching from the PVA fabric used as a material of the polarizer when giving a polarizing function in the polarizing plate Direction and the iodine dyeing, the direction of light absorption becomes the MD direction. Negative biaxial A plate 16 requires stretching in the MD direction and the direction perpendicular thereto for a film having a positive refractive index characteristic of increasing refractive index with respect to the stretching direction. Specifically, when stretching in the MD direction and stretching in the direction perpendicular to the MD or relatively less in the vertical direction thereof, and stretching in the MD direction relatively much, the axis is formed in the MD direction. In the former case, when stretching in the MD direction, Nx is formed in the MD direction, Nx becomes larger, and Ny and Nz become smaller, but there is no restriction during stretching in the vertical direction and the thickness direction of the MD direction, so the ratio decreases. Therefore, NZ becomes 1, and when it is later drawn perpendicular to the MD direction, Ny becomes large and Nx does not change since the length is fixed in the MD direction. At this time, since Ny is not larger than Nx and Nz is smaller, since Ny has a refractive index of Nx > Ny > Nz, NZ is larger than 1 and the axis is formed in the MD direction. In the latter case, when the MD direction is set to Nx and the drawing is made perpendicular to the MD direction, Ny becomes large and Nx is fixed because the length of the MD direction is constrained while drawing Nx. When it is stretched relatively in the MD direction, Ny and Nz are reduced and Nx becomes large, and the refractive index of Nx > Ny > Nz is NZ > 1 and the axis is formed in the MD direction.

In addition, the positive biaxial A plate 14 imparts a phase difference through stretching in a direction perpendicular to the MD direction of a film having a negative refractive index characteristic of decreasing refractive index with respect to the stretching direction, wherein the slow axis 15 is in the MD direction. Formed and the refractive index in the MD direction becomes Nx. In the above case, the size of Nx is almost unchanged because the length of Nx is fixed in the MD direction during stretching, but the size of Nz is increased because the size of Ny decreases and the thickness direction shrinks because the vertical direction of the MD direction is stretched. . Therefore, NZ value becomes smaller than 0, and the direction of slow axis 15 becomes MD direction.

When manufacturing a lower polarizing plate using the film made by such an extending process, joining by the roll-to-roll process is possible.

In the present invention, the absorption axis 12 of the lower polarizing plate 10 and the polarizer 11 should be located in the vertical direction when viewed from the viewing side. Specifically, when the absorption axis 12 of the lower polarizing plate 10 near the backlight unit 40 is in the vertical direction, light passing through the lower polarizing plate 10 is polarized in the horizontal direction, which is the liquid crystal cell 30 of the panel. When the light passes through the light, the light passes in the vertical direction and passes through the upper polarizing plate 20 on the side of the visual viewer whose absorption axis is in the horizontal direction. At this time, the person wearing the polarized sunglasses having the absorption axis in the horizontal direction (the absorption axis of the polarized sunglasses is in the horizontal direction) at the viewer can recognize the light emitted from the liquid crystal display. If the absorption axis 12 of the lower polarizing plate 10 near the backlight unit 40 is in the horizontal direction, a problem occurs in that an image is not visible to a person wearing polarized sunglasses. In addition, in the case of a large liquid crystal display device, in order to make the image visible from the viewer's side, in view of the fact that a human's field of view is wider than a vertical direction, a general liquid crystal display device except for a special purpose liquid crystal display device such as an advertisement is used. Since the field of view is wider in the horizontal direction than in the vertical direction, it is manufactured in the form of 4: 3 or 16: 9.

The slow axis 17 of the negative biaxial A plate of the present invention and the slow axis 15 of the positive biaxial A plate are light-positive positive biaxial A plate 15 and negative biaxial A. When the plate 16 is incident in the normal direction, it means the axis through which the light passes slowly by the retardation film, which means the axis having the largest refractive index, which does not cause a phase difference when passing through the retardation film. It is distinguished from the optical axis. When the liquid crystal displays black, the absorption axes 12 and 22 of the polarizing plates 10 and 20 that are orthogonal to the viewer's front face cannot be kept in an orthogonal state due to their geometrical characteristics on a slope other than the front side, so that light leaks. And the light narrows the viewing angle. According to the present invention, since the optical system can keep the absorption axes 12 and 22 in the orthogonal state from the slope between the polarizers 11 and 21 of the upper and lower polarizing plates 10 and 20, the viewing angle is narrow without narrowing the light. You won't lose. The light does not leak in the phase difference value condition of the present invention can be explained through the Poincare sphere (Poincare sphere).

5 is a planar switching mode liquid crystal display device arranged in the configuration of FIG. 1 using a film having an optical property of the present invention, which is a human being in the coordinate system defined by FIG. 6 on a Poincare Sphere. It shows the change in polarization state at the time θ = 60 ° and Φ = 45 ° at the wavelength of light 550 nm which is brightly felt. Specifically, using the configuration of FIG. 1, the light passing through the polarizer 11 on the backlight side 40 is polarized in the polarization state 1 on the Poincare Sphere and is a positive biaxial A plate 14. While passing through the negative biaxial A plate 16, the FFS liquid crystal cell 30, and the isotropic protective layer 24, the polarization state on the Poincare Sphere (Poincare Sphere) changes in the form of polarization state 2, 3, 4, and 5. Specifically, the light polarized in the polarization state 1 becomes the polarization states 2 and 3 by the positive biaxial A plate 14 and the negative biaxial A plate 16, and the light passing through the FFS liquid crystal cell 30 is polarized. After changing to state 4 and passing through the isotropic protective layer 24, as described above, the polarizers become orthogonal to the polarized state 5 in which light does not leak and the viewing angle does not become narrow.

Hereinafter, the effects of the dark state implementation at the viewing angle when the voltage is applied by the above configuration are summarized in Examples and Comparative Examples. The invention can be better understood by the following examples, which are intended to illustrate the invention and are not intended to limit the scope of protection as defined by the appended claims.

Example

In Examples 1 to 6 and Comparative Examples 1 to 4 below, the wide viewing angle effect was compared by performing simulation by applying the LCD simulation program TECH WIZ LCD 1D (man system, KOREA).

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 1D (man system, KOREA) with a structure as shown in FIG. 1. Referring to the structure of Figure 1 in detail.

The backlight unit 40 , the lower polarizing plate 10, the liquid crystal cell 30, and the upper polarizing plate 20 are sequentially stacked, and the lower polarizing plate 10 is negative biaxial A plate 16, positive from the liquid crystal cell side. It consists of a biaxial A plate 14, a polarizer 11 and a protective layer 13, the upper polarizing plate 20 is an isotropic protective layer 24, a polarizer 21 and a protective layer 23 from the liquid crystal cell side. ) In order.

At this time, the polarizers 11 and 21 are imparted with the function of the polarizers by stretching and dyeing, and the absorption axes of the polarizers 10 and 20 are respectively on both sides of the FFS mode liquid crystal cell 30 (Wooo9000, HITACHI, JAPAN). Placed orthogonally. Referring to FIG. 2, the absorption axis 22 of the upper polarizing plate 20 and the alignment direction 31 of the liquid crystal included in the liquid crystal cell 30 are described with reference to the absorption axis 22 of the polarizer 21 of the upper polarizing plate 20. ) And the absorption axis 12 of the polarizer 11 of the lower polarizing plate 10 are orthogonal to each other, and the absorption axis 22 of the polarizer 21 of the upper polarizing plate 20 and the alignment direction 31 of the liquid crystal are parallel to each other. Are arranged.

In addition, protective layers 13 and 23 are arranged on opposite surfaces of the liquid crystal cell 30 of the polarizer 11 of the lower polarizing plate 10 and the polarizer 21 of the upper polarizing plate 20.

On the other hand, each of the optical film and the backlight used in the embodiment of the present invention was used to have the optical properties as follows.

라고 할 때 하기 수학식 5 내지 9에 의해 정의된다.First, the polarizers 11 and 21 of the lower polarizing plate 10 and the upper polarizing plate 20 are dyed iodine in the stretched PVA to impart a polarizer function. The degree of polarization is 99.9% or more, and the visibility of light transmittance is 41% or more. The visibility polarization and the visibility single transmittance are the TD (λ) transmittance of the transmission axis according to the wavelength, and the transmittance correction of the absorption axis according to the wavelength of MD (λ) and the visibility correction value defined in JIS Z 8701: 1999.

Is defined by the following equations (5) to (9).

The optical characteristics caused by the difference in internal refractive index according to the direction of each film were 589.3 nm in the light source, and the negative biaxial A plate 16 had a front phase difference R0 of 81 nm and a refractive index ratio NZ of 1.21; The positive biaxial A plate 14 has a front phase difference R0 of 90 nm and a refractive index ratio NZ of -0.21; As the isotropic protective layer 14, a front phase difference (R0) of 0 nm and a thickness direction phase difference (Rth) of 0 nm were used. At this time, the direction of the slow axis of each of the negative biaxial A plate 14 and the positive biaxial A plate 16 is parallel to the absorption axis 12 of the adjacent polarizer 11.

The negative biaxial A plate 16 uses a cycloolefin polymer (COP, Zeonor, Optes, Japan), while the positive biaxial A plate 14 is negative between two polymethylmethacrylates (PMMA). PS having a refractive index characteristic was sequentially arranged a retardation film (I-Film, Optes, Japan). In addition, triacetyl cellulose (TAC) having an optical property having an Rth of 50 nm with respect to incident light 589.3 nm was used as the outer protective layers 13 and 23 of the upper and lower polarizing plates 10 and 20, respectively. As the backlight unit 50, actual measurement data mounted on a 32-inch Wooo9000 model (HITACHI, JAPAN) was used.

The optical components were stacked as shown in FIG. 1 and subjected to simulation of visibility omnidirectional transmittance. As a result, the results as shown in FIG. 7 were obtained. FIG. 7 illustrates the distribution of visibility of permeability in the case of displaying the black on the screen, and the range on the scale ranges from 0% to 0.05% of the transmittance, and the portion exceeding 0.05% of the transmittance when displaying the cancer is red, Low permeability areas are indicated in blue. At this time, it was confirmed that the wider the range of blue in the center, the wider the viewing angle. This is because the polarization state change on the inclined plane as shown in Fig. 5 (R1).

Example 2

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 89 nm and a refractive index ratio NZ of 1.21 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 51 nm and the refractive index ratio NZ was -0.99 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 8. This is because the polarization state of the Pohang Care sphere as shown in FIG.

Example 3

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 31 nm and a refractive index ratio NZ of 2.99 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged so that the front phase difference R0 was 109 nm and the refractive index ratio NZ was -0.21 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 9. This is because the polarization state change on the inclined plane as shown in Fig. 5 (R3).

Example 4

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 39 nm and a refractive index ratio NZ of 2.99 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 70 nm and the refractive index ratio NZ was -0.99 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching LCD are shown in FIG. 10. This is because the polarization state change in the plane of the Poang Kare sphere as shown in Fig. 5 (R4) on the inclined surface.

Example 5

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 94 nm and a refractive index ratio NZ of 1.1 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 51 nm and the refractive index ratio NZ was -0.99 to manufacture an in-plane switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 11.

Example 6

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 89 nm and a refractive index ratio NZ of 1.21 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 44 nm and the refractive index ratio NZ was -1.1 to manufacture a planar switching (IPS) liquid crystal display device.

The results of the simulation of visibility and omnidirectional transmittance of the planar switching liquid crystal display are shown in FIG. 12.

Comparative Example 1

In the configuration of Example 1, the negative biaxial A plate 14 and the positive biaxial A plate 16 were removed, and an isotropic protective film was replaced to manufacture a planar switching (IPS) liquid crystal display device as shown in FIG. 13.

As a result of performing visibility visibility omnidirectional transmittance simulation of the planar switching liquid crystal display device, a result as shown in FIG. 14 was obtained.

7 of the first embodiment is wider blue portion in the center than in Figure 14 it can be seen that a wider viewing angle is implemented. In addition, the maximum omnidirectional transmittance is calculated as 0.024% for the optimization value in Example 1, 0.34% in the case of Comparative Example 1, which can be seen that Comparative Example 1 is about 14.2 times larger than the maximum transmission in all directions.

Comparative Example 2

In the same manner as in Example 1, except that the negative biaxial A plate 16 has a front phase difference R0 of 130 nm and a refractive index ratio NZ of 3 at a light source of 589.3 nm; The positive biaxial A plate 14 was disposed such that the front phase difference R0 was 50 nm and the refractive index ratio NZ was -1 to manufacture a planar switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display were shown in FIG. 15, and the viewing angle was narrow due to high transmittance of the inclined surface in the black state.

Comparative Example 3

In the same manner as in Example 1, except that the negative biaxial A plate 16 had a front phase difference R0 of 30 nm and a refractive index ratio NZ of 3 at a light source of 589.3 nm; The positive biaxial A plate 14 was arranged such that the front phase difference R0 was 150 nm and the refractive index ratio NZ was -0.2 to manufacture a planar switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display device were shown in FIG. 16, and it was confirmed that the viewing angle was narrow due to high transmittance of the inclined plane in the black state.

Comparative Example 4

In Example 1, the positions of the negative biaxial A plate 16 and the positive biaxial A plate 14 were changed to manufacture a planar switching (IPS) liquid crystal display device.

The simulation results of the visibility of the planar switching liquid crystal display were shown in FIG. 17, and it was confirmed that the viewing angle was narrow because the transmittance of the inclined plane in the black state was high.

As described above, the planar switching liquid crystal display device according to the present invention can provide a good image quality for all time, it can be applied to a liquid crystal display that requires high viewing angle characteristics.

1 is a perspective view showing the structure of an on-plane switching liquid crystal display (IPS-LCD) according to the present invention;

2 is a schematic diagram for explaining the arrangement of the absorption axis and the alignment direction of the liquid crystal of the polarizing plate according to the present invention,

3 is a schematic diagram for explaining the refractive index of the retardation film according to the present invention,

Figure 4 is a schematic diagram showing the MD direction in the manufacturing process for explaining the stretching direction of the retardation film and the polarizing plate according to the present invention,

FIG. 5 shows a change in polarization state capable of viewing angle compensation at θ = 60 ° and Φ = 45 ° of the present invention on a Poincare Sphere.

6 is a schematic view for explaining what is represented by θ, Φ in the coordinate system of the present invention,

7 is a simulation result of the visibility of the omnidirectional transmittance of Example 1 according to the present invention,

8 is a simulation result of the visibility of the visibility of Example 2 according to the present invention,

9 is a simulation result of the visibility of the omnidirectional transmittance of Example 3 according to the present invention,

10 is a simulation result of the visibility of the visibility of Example 4 according to the present invention,

11 is a simulation result of the visibility of the omnidirectional transmittance of Example 5 according to the present invention,

12 is a result of simulating the visibility of omnidirectional transmittance of Example 6 according to the present invention,

13 is a perspective view showing the structure of an on-plane switching liquid crystal display device (IPS-LCD) including an isotropic protective film of Comparative Example 1 of the present invention;

14 is a simulation result of the visibility of the omnidirectional transmittance of Comparative Example 1 of the present invention,

15 is a simulation result of the visibility of omnidirectional transmittance of Comparative Example 2 of the present invention,

16 is a result of simulating the visibility omnidirectional transmittance of Comparative Example 3 of the present invention,

17 is a simulation result of the visibility of omnidirectional transmittance of Comparative Example 4 of the present invention.

Claims (10)

As a lower plate polarizing plate for planar switching (IPS) modes laminated in the order of a negative biaxial A plate, a positive biaxial A plate, a polarizer, and a protective layer from the liquid crystal cell side, The negative biaxial A plate has a front phase difference value (R 0) of 20 to 100 nm, a refractive index ratio (NZ) of 1.01 ≦ NZ ≦ 3.5, and a slow axis is parallel to an absorption axis of an adjacent polarizer; The positive biaxial A plate has a front phase difference value (R0) of 40 to 120 nm, a refractive index ratio (NZ) of -1.2 ≤ NZ ≤ -0.01, and a slow axis configured to be parallel to an absorption axis of an adjacent polarizer. The method of claim 1, wherein the negative biaxial A plate and the positive biaxial A plate are independently of each other triacetylcellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), A lower polarizing plate made of one selected from the group consisting of polypropylene (PP), polycarbonate (PC), polysulfone (PSF), and polymethyl methacrylate (PMMA). The lower plate polarizer of claim 1, wherein the positive biaxial A plate has a structure in which polymethyl methacrylate (PMMA), polystyrene (PS), and polymethyl methacrylate (PMMA) are sequentially stacked. The lower polarizing plate according to claim 1, wherein at least one layer of the positive biaxial A plate is a modified polycarbonate (PC). The method of claim 1, wherein the protective layer is triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP), polycarbonate (PC), A lower polarizing plate made of one selected from the group consisting of polysulfone (PSF) and polymethyl methacrylate (PMMA). An in-plane switching (IPS) mode liquid crystal display comprising the lower polarizing plate of claim 1. 7. The liquid crystal display device according to claim 6, wherein the luminous transmittance omnidirectional maximum transmittance satisfies a compensation relationship of 0.1% or less. 7. An isotropic protective layer according to claim 6, wherein the front phase difference (R0) and the thickness direction phase difference (Rth) are respectively less than 10 nm from the liquid crystal cell side; Polarizer; And a top polarizer stacked in a protective layer order. The method of claim 8, wherein the isotropic protective layer and the protective layer are independently of each other triacetyl cellulose (TAC), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethylene terephthalate (PET), polypropylene (PP) And polycarbonate (PC), polysulfone (PSF), and polymethyl methacrylate (PMMA). The liquid crystal display of claim 6, wherein the liquid crystal cell is configured such that a liquid crystal alignment direction is parallel to an absorption axis of the upper polarizing plate.

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