KR102113629B1 - In-Plane Switching Mode Liquid Crystal Display Device - Google Patents

Abstract

The present invention relates to a transverse electric field type liquid crystal display device that solves a problem of contrast and color shift in a diagonal direction by varying the application of an optical compensation film, and is located under the transverse electric field type liquid crystal panel; and, 1 A first polarizing plate comprising a support and a first polarizing element; And, the transverse electric field type liquid crystal panel is located directly in contact with the refractive index anisotropy (Nz) is -7.5 to -1.0 ((Nz = Rth / Re +0.5 , Re = (nx-ny) * d, Rth = ((nx + ny) / 2-nz) * d, nx, ny, and nz are refractive indexes in the x, y, and z directions, respectively, d is film A) a first optical compensation film made of a positive B-plate; and a second optical compensation film located on the first optical compensation film and made of a negative back-dispersed A plate; and the second optical compensation film Located on the, and includes a second polarizing plate comprising a second polarizing element and a second support And it characterized in that formed.

Description

Transverse electric field type liquid crystal display device {In-Plane Switching Mode Liquid Crystal Display Device}

The present invention relates to a transverse electric field type liquid crystal display device, and more particularly, to a transverse electric field type liquid crystal display device that solves a problem of weak contrast ratio and color shift in a diagonal direction by applying an optical compensation film.

With the advent of the full-fledged information age, the display field for visually displaying electrical information signals is rapidly developing. Accordingly, research is being conducted to develop performance of thinning, lightening, and low power consumption for various flat display devices.

Typical examples of such a flat panel display device are a liquid crystal display device (LCD), a plasma display panel device (PDP), a field emission display device (FED), and an electroluminescent display device. (Electro Luminescence Display device: ELD), Electro-Wetting Display device (EWD), Organic Light Emitting Display device (OLED), and the like.

These flat panel display devices commonly include a flat panel display panel for realizing an image. The flat panel display panel is a structure in which a pair of substrates with unique light emitting materials or polarizing materials interposed therebetween.

Particularly, among these flat panel display devices, a liquid crystal display (LCD) is a device that expresses an image using optical anisotropy of liquid crystal, and is excellent in resolution, color display, and image quality, and is actively applied to laptops or desktop monitors. have.

The liquid crystal display device is mainly composed of a color filter substrate as a first substrate, an array substrate as a second substrate, and a liquid crystal layer formed between the color filter substrate and the array substrate.

 At this time, the color filter substrate is a color filter composed of a plurality of sub-color filters that realize the colors of red (R), green (G) and blue (Blue) and the sub-color filter It consists of a black matrix (black matrix) to block the light passing through the liquid crystal layer, and a transparent common electrode for applying a voltage to the liquid crystal layer.

 In addition, the array substrate is a thin film transistor (Tin Film Transistor; TFT) which is a switching element formed in a plurality of gate lines and data lines arranged vertically and horizontally to define a plurality of pixel regions, and an intersection region of the gate lines and the data lines, and the It consists of a pixel electrode formed on a pixel region.

The color filter substrate and the array substrate configured as described above are bonded to face each other by a sealant formed on an outer portion of the image display area to form a liquid crystal display panel, and the color filter substrate or the array substrate is bonded to the color filter substrate or It is made through a bonding key formed on the array substrate.

 The above-described liquid crystal display device represents a twisted nematic (TN) type liquid crystal display device that drives nematic liquid crystal molecules in a direction perpendicular to a substrate, and the liquid crystal display device of the above method has a viewing angle of about 90 degrees. It has the disadvantage of being narrow. This is due to the refractive anisotropy of the liquid crystal molecules, because the liquid crystal molecules aligned horizontally with the substrate are oriented almost perpendicular to the substrate when a voltage is applied to the liquid crystal display panel.

Accordingly, an in-plane switching mode (IPS) liquid crystal display device in which a liquid crystal molecule is driven in a horizontal direction with respect to a substrate to improve a viewing angle of 170 degrees or more has been proposed.

By the way, the transverse electric field type liquid crystal display device has excellent viewing angle since the phase delay change of the liquid crystals different from the voltage is small and the optical axes of the upper and lower polarizing plates are maintained vertically in the vertical and horizontal directions, but the vertical states of the optical axes of the upper and lower polarizing plates Light leakage occurs in the diagonal direction in which the image is broken, causing image quality deterioration.

The conventional transverse electric field type liquid crystal display device has the following problems.

There is a problem that light leakage occurs in the black state in which the optical axis in the diagonal direction is broken vertically, and the current polarizing plate is composed of a PVA optical layer and a protective film of TAC (Triacetyl cellulose) above and below. Deterioration of image quality due to cannot be solved

The present invention has been made to solve the above problems, and to provide a transverse electric field type liquid crystal display device that solves the problem of weak contrast ratio and color shift in a diagonal direction by applying an optical compensation film.

The present invention for achieving the above object is a horizontal electric field type liquid crystal display device, a horizontal electric field type liquid crystal panel; And, the first polarizing plate is located under the horizontal electric field type liquid crystal panel, a first support and a first polarizing element; And, the transverse electric field type liquid crystal panel is located directly in contact with the upper portion, the refractive index anisotropy (Nz) is -7.5 to -1.0 ((Nz = Rth / Re +0.5, Re = (nx-ny) * d, Rth = ( (nx + ny) / 2-nz) * d, nx, ny, nz are refractive indexes in the x, y, and z directions, d is the thickness of the film, respectively) A compensation film; and a second optical compensation film located on the first optical compensation film and made of a negative back-dispersed A plate; and a second polarizing element and a second support located on the second optical compensation film. It is characterized by being made by including a second polarizing plate.

Here, the first optical compensation film has a refractive index characteristic of nz> nx> ny.

In addition, it is preferable that the second optical compensation film has an Nz value of 1.0 to 1.3. Further, in this case, it is preferable that the second optical compensation film has a refractive index condition of nx> ny = nz.

Here, the first and second polarizing elements have absorption axes perpendicular to each other.

Then, the optical axis of the transverse electric field type liquid crystal panel and the absorption axis of any one of the first polarization element and the second polarization element coincide.

Light passing through the first polarization element, the liquid crystal panel, and the first and second optical compensation films in turn may have a polarization state coinciding with the absorption axis of the second polarization element.

The first and second supports may be made of triacetyl celluose or cyclo olefin polymer (COP) without phase delay.

In this case, the transverse electric field type liquid crystal panel includes: first and second substrates facing each other; and gate lines and data lines crossing each other on the first substrate to define a plurality of pixel areas; and the gate lines and A thin film transistor formed at an intersection of a data line; and a pixel electrode and a common electrode formed alternately in each pixel area; and black formed corresponding to the gate line, the data line, and the thin film transistor on the second substrate A matrix layer; and a color filter layer formed on a second substrate corresponding to the pixel regions; And a liquid crystal layer between the first and second substrates.

The transverse electric field type liquid crystal display device of the present invention as described above has the following effects.

The transverse electric field type liquid crystal display device of the present invention is to improve the image quality by preventing color shift by preventing a light leakage defect in a dark state in a diagonal direction, and for this purpose, a liquid crystal panel and an upper polarizing element (second part) on the upper side of the liquid crystal panel Polarization element) and the properties of the first and second optical compensation films positioned therebetween.

That is, the first optical compensation film closest to the liquid crystal panel has a refractive index anisotropy Nz value in the range of -7.5 to -1.0, a biaxial positive B plate, and a second optical compensation film has a refractive index anisotropy Nz value of 1.0 to 1.3. It is assumed to be a negative A plate with reverse wavelength dispersion characteristics. Through this, when the incident light of all colors passes through the second polarizing element (upper polarizing element), it is collected on the absorption axis, thereby optically blocking light leakage in a dark state.

1 is a cross-sectional view showing a transverse electric field type liquid crystal display device of the present invention
FIG. 2 is a plan view of the liquid crystal panel of FIG. 1;
3 is a cross-sectional view taken along line I to I 'in FIG. 2;
Figure 4a is an exemplary view schematically showing the light transmission axes of the orthogonal first and second polarizing elements when viewed from the front
Figure 4b is an exemplary view schematically showing the light transmission axis of the orthogonal first and second polarizing elements when viewed from the diagonal direction
5A and 5B are views showing an arbitrary elliptical polarization in a Cartesian coordinate system and a corresponding Poincare vector.
6 is a view showing a light path of a comparative example of the present invention in a Poincare vector
7 is a graph showing the light scattering properties of the A-plate formed by the optical path L2 of FIG. 6 for each wavelength
8 is a graph comparing the optical dispersion of the second optical compensation film of the liquid crystal display of the present invention and the A-plate of the comparative example for each wavelength
FIG. 9 is a view showing a light path of light passing through a liquid crystal panel in a Puccan vector in the liquid crystal display device of the present invention
10A and 10B are two-dimensional views of an optical compensation path of a comparative embodiment and an embodiment of the present invention.
11A and 11B are simulation diagrams showing the luminance viewing angle characteristics of the dark state of the comparative example and the embodiment of the present invention.

Hereinafter, a lateral electric field type liquid crystal display device of the present invention will be described in detail with reference to the accompanying drawings.

1 is a cross-sectional view showing a transverse electric field type liquid crystal display device of the present invention.

As shown in FIG. 1, in the present invention, the transverse electric field type liquid crystal display device includes a liquid crystal panel 100 and a first support 112 and a first polarization element 111 located under the liquid crystal panel 100. The first polarizing plate 110, the first optical compensation film 121 is located directly in contact with the upper portion of the liquid crystal panel 100, a refractive index anisotropy (Nz) of -7.5 to -1.0 positive B plate, and Located on the first optical compensation film 121, the second optical compensation film 122 made of a negative back-dispersed A plate and the second optical compensation film 122, the second polarizing element 123 And a second polarizing plate 120 including a second support 124.

In common, Nz representing the refractive index anisotropy of the first and second optical compensation films 121 is calculated as a value of Nz = Rth / Re +0.5. Re means the phase retardation value in the plane of the optical compensation film, and is obtained under the condition of Equation 1 below, Rth means the phase retardation value in the thickness direction of the optical compensation film, and is obtained by the condition of Equation 2 Lose.

[Equation 1]

Re = (nx-ny) * d

[Equation 2]

Rth = ((nx + ny) / 2-nz) * d

Here, nx, ny, and nz are refractive indices in the x, y, and z directions, respectively, and d denotes the thickness of the corresponding optical compensation film, respectively.

Meanwhile, the first optical compensation film 121 is a biaxial film having different refractive indices in the x, y, and z directions, and has a refractive index relationship of nz> nx> ny.

The second optical compensation film 122 is characterized in that the refractive indexes in the y and z directions are approximately the same (ny = nz), and the refractive indexes nx in the x direction are larger than those of the refractive indices ny and nz. Here, ny = nz includes cases in which ny and nz are numerically completely identical as well as substantially identical cases.

In addition, the first optical compensation film 121 is a biaxial optical film, and may be formed of a cycloolefin polymer (COP), polynorbonene (PNB), polycarbonate (PC), biaxial liquid crystal film, or the like. .

In this case, the second optical compensation film 122 has an Nz value of 1.0 to 1.3, which indicates the degree of refractive index anisotropy. In addition, in this case, the second optical compensation film 122 has a reverse wavelength dispersion characteristic, and for example, when described as a refractive index, a refractive index of a long wavelength is higher than a refractive index of a short wavelength (Δn (450nm) < Δn (550 nm) <Δn (650 nm)). In this case, the second optical compensation film 122 is uniaxial, and may be formed of an olefin polymer, a stretched polycarbonate film, or a UV curable horizontally oriented liquid crystal film.

In addition, the first and second polarization elements 111 and 123 have absorption axes perpendicular to each other.

In this case, the optical axis of the liquid crystal panel 100 and the absorption axis of any one of the first polarization element 111 and the second polarization element 123 coincide.

In the transverse electric field type liquid crystal display device of the present invention, the light passing through the first polarizing element 111, the liquid crystal panel 100, and the first and second optical compensation films 121 and 122 in turn is the above. It may have a polarization state that matches the absorption axis of the second polarization element 123 without a color difference.

The first and second supports 112 and 124 may be formed of a protective film such as triacetyl celluose or cyclo olefin polymer (COP) without phase delay.

In addition, although the first and second polarizing elements 111 and 123 are not particularly limited as optical films, for example, a stretched film of a polymer film mainly composed of a PVA-based resin containing iodine or a dichroic dye, a dichroism It may be an O-type polarizing element in which a liquid crystal composition containing a substance and a liquid crystal compound is aligned in a certain direction, an E-type polarizing element in which a lyotropic liquid crystal is aligned in a certain direction, or the like.

Meanwhile, the internal structure of the liquid crystal panel of the transverse electric field type liquid crystal display device of the present invention will be briefly described below.

FIG. 2 is a plan view of the liquid crystal panel of FIG. 1, and FIG. 3 is a cross-sectional view taken along line I to I 'in FIG. 2.

In an actual lateral electric field type liquid crystal display, N gate lines and M data lines intersect and there are MxN pixels, but for simplicity, the drawing is illustrated with one pixel.

2 and 3, the liquid crystal panel 100 of the transverse electric field type liquid crystal display device, the first and second substrates (10, 5) opposite to each other, and crossing each other on the first substrate 10 A gate line 16 and a data line 17 defining a plurality of pixel areas, a thin film transistor T formed at an intersection of the gate line 16 and the data line 17, and each pixel area to each other A black matrix formed corresponding to the gate line 16, the data line 17, and the thin film transistor T on the alternately formed pixel electrode 18 and the common electrode 8 and the second substrate 5 A layer 6 and a color filter layer 7 formed on a second substrate 5 corresponding to the pixel regions and a liquid crystal layer 30 between the first and second substrates 10 and 5 It is done.

 Each of the first and second substrates 10 and 5 is made of a transparent substrate, and in the white state, light incident through the transmission axis of the lower first polarizing element 111 is transferred to the liquid crystal panel 100. , Transmitted through the transmission axis of the second polarizing element 123 through the first and second optical compensation films 121 and 122, and display is performed.

Meanwhile, the thin film transistor T includes a gate electrode 21 connected to the gate line 16, a source electrode 22 connected to the data line 17 and a drain electrode 23 spaced apart from the gate electrode 21. Here, the drain electrode 23 is integrally connected to the pixel electrode line 181 connecting the branched pixel electrodes 18.

In addition, the thin film transistor T includes a first insulating film 15a for insulating between the gate electrode 21 and the source / drain electrodes 22 and 23, and the source electrode 22 and the drain electrode ( 23) an active pattern 24 forming a conductive channel between the first insulating layer 15a and the source / drain electrodes 22 and 23 is included between the layers.

For reference, reference numeral 25, which is not described, denotes an ohmic-contact layer that makes ohmic contact between the source / drain regions of the active pattern 24 and the source / drain electrodes 22, 23.

 In the pixel area, a common line 8l and a storage electrode 18s are arranged in a direction parallel to the gate line 16, and a transverse electric field 90 is generated in the pixel area to generate liquid crystal molecules (not shown). ) A plurality of common electrodes 8 and pixel electrodes 18 switching are arranged in a direction parallel to the data line 17.

 At this time, the storage electrode 18s overlaps a portion of the common line 8l under the first insulating layer 15a to form a storage capacitor Cst.

The liquid crystal panel 100 configured as described above has an alignment film (not shown) that determines the initial alignment direction of the liquid crystal molecules on the opposite surfaces of the liquid crystal layers of the first and second substrates 10 and 5, respectively. Is formed.

And, as an external configuration of the liquid crystal panel, the first polarizing element 111 is formed directly in contact with the outer surface of the first substrate 10, the first optical compensation film on the outer surface of the second substrate 5 (121) is formed by direct contact.

In the liquid crystal panel 100 having the above-described structure, the common electrode 8 and the pixel electrode 18 are disposed on the same first substrate 10 to generate a transverse electric field, and liquid crystal molecules are disposed on the first substrate 10. Since it is arranged side by side with the transverse electric field parallel to the plane, it has an advantage of improving the viewing angle.

However, the liquid crystal panel 100 of the transverse electric field method has a problem of exhibiting a low contrast ratio when applied to itself, since light leakage occurs in a diagonal direction when displaying a black state. have.

On the other hand, the liquid crystal layer 30 may include a liquid crystal that is homogeneously oriented in a state in which there is no electric field (light (white) state), and in this case, the liquid crystal layer 30 has an nx> ny = nz. Refractive index characteristics can be exhibited. However, the in-plane refractive index is set to nx and ny, and the refractive index in the thickness direction is set to nz. In this case, ny = nz includes not only numerically identical but also substantially identical cases.

The transverse electric field method uses a voltage-controlled birefringence (ECB) effect to equip the liquid crystal layer with a nematic liquid crystal homogeneously oriented in the absence of an electric field, between a pixel electrode and a common electrode when a voltage is applied. This is a method of driving a liquid crystal layer with a transverse electric field that is created.

4A is an exemplary view schematically showing the light transmission axes of the first and second polarizing elements that are orthogonal when viewed from the front, and FIG. 4B is the first and second orthogonal when viewed from the diagonal direction. It is an exemplary view schematically showing the light transmission axis of the polarizing element.

As illustrated in FIG. 4A, when the liquid crystal panel is viewed from the front, the light absorption axes of the first and second polarizing elements positioned at the lower and upper portions of the liquid crystal panel form 90 °, thereby realizing a dark state. When looking at the liquid crystal panel in the diagonal direction as shown in 4b, the difference between the light absorption axes of the first and second polarizing elements is observed to be 90 ° or more, and when viewed in the diagonal direction, between the first and second polarizing elements Because orthogonality is broken, light leakage occurs.

As described above, the transverse electric field type liquid crystal display device has a small change in phase retardation of the liquid crystal according to the voltage in a manner in which a transverse electric field is applied to the liquid crystal layer, and the viewing angle is maintained because the optical axes of the upper and lower polarizing plates maintain a vertical state in the vertical direction. Although excellent, light leakage may occur in the diagonal direction in which the vertical states of the optical axes of the first and second polarizing elements are broken, which may cause deterioration of image quality.

In order to improve the deterioration of the image quality in the diagonal direction, an optical compensation film must be applied, and the current protective layer (mainly the material is a TAC layer) that protects the optical layer (PVA layer) of the polarizing plate itself is compensated. There is a limit.

Hereinafter, the principle of applying the first and second optical compensation films to prevent light leakage in the diagonal direction of the present invention will be described using a Puancare sphere.

In order to geometrically interpret the optical properties of a transparent medium such as a liquid crystal, the expression of the Paucan Curry in polarized state is used.

First, the Jones vector can represent only complete polarization, and the Stokes parameter defined as Equation 3 below is used to express more general partial polarization.

[Equation 3]

At this time, <> represents the time average, and an inequality is established between these four variables, and the equation is applied only to full polarization.

In the case of full polarization, the relationship of the following equation (4) holds between the standardized variables s1, s2, and s3 obtained by dividing S ₁ , S ₂ and S ₃ by the brightness S0 of light.

[Equation 4]

This is the equation of a sphere with a radius of 1 in 3D space, and the sphere consisting of dots with (s1, s2, s3) as Cartesian coordinates means the Poincare sphere.

At this time, all points on the equatorial line in the Puancare sphere correspond to linear polarization, the polar point corresponds to the circular polarization of the right hand and the polar point to the polar circle of the left hand. In addition, all points in the northern hemisphere correspond to polarization of the right hand ellipse, and all points in the southern hemisphere correspond to polarization of the left hand.

5A and 5B are views showing an arbitrary elliptical polarization in the Cartesian coordinate system and a corresponding Puan Curry vector.

As shown in the figure, the latitude angle of the Puan curry vector P corresponding to the elliptical polarization whose azimuthal angle is Ψ and the elliptical angle x is 2x and the azimuth angle is 2Ψ. If this point is in the northern hemisphere, the direction of rotation of the electric field vector is clockwise; if it is in the southern hemisphere it is counterclockwise. The opposing points on the puan curry sphere show polarization states orthogonal to each other.

In addition, the Unitary Jones matrix, which describes the change in polarization state when light passes through a transparent medium, can be interpreted as a rotational transformation on a Puan Curry sphere.

On the other hand, the following describes the change in the optical path movement according to the characteristics of forward and backward dispersion applied to the optical compensation film.

Fig. 6 is a view showing a light path of a comparative example of the present invention in a Puan Curry vector. And, Figure 7 is a graph showing the light scattering properties of the A-plate consisting of the optical path L2 of Figure 6 for each wavelength. In the comparative examples shown in Figs. 6 and 7, the first and second optical compensation films commonly have constant dispersion characteristics, and the first optical compensation film on the liquid crystal panel is a positive B plate and a second optical compensation film Has the properties of a negative A plate. The first and second optical compensation films have the refractive index anisotropy (Nz) characteristic described in FIG. 1 except for the static dispersion characteristic.

6, in the comparative example, in the Puancare sphere, P represents the absorption axis of the lower polarization element (first polarization element), and the opposite point S in the equatorial plane represents the transmission axis of the lower polarization element. And, A is the absorption axis of the upper polarizing element (second polarizing element) when the liquid crystal panel is viewed from the diagonal direction, and the opposite point (A ') of the equatorial plane represents the transmission axis of the upper polarizing element. Here, since viewed from the diagonal direction, the absorption axis P of the lower polarization element and the absorption axis A of the upper polarization element are not completely 90 degrees.

Therefore, the light incident on the liquid crystal panel through the lower polarizing element is at point S of the Puancare sphere, and the absorption axis of the upper polarizing element is at point A, and without the optical compensation film, the transmitted light is not completely obscured by the absorption axis, causing light leakage. Since this appears, the transverse electric field type liquid crystal display device of the present invention has a first optical compensation film having an optical path L1 to change the light at point S to the latitude of the southern hemisphere, and an optical path L2 that ellipses from point D to point A And a second optical compensation film. Here, when the first optical compensation film is a positive B-type plate, and the second optical compensation film has a constant dispersion characteristic of FIG. 7 (the phase delay value becomes lower as the wavelength increases), as shown in FIG. 6, the upper polarization element In the absorption axis, the phase delay for each color of R, G, and B is different, so that R (red) compared to G (green) does not reach A, and B (blue) rather exceeds A, so that red and blue Color shift phenomenon can be expected to occur.

However, in particular, the phase retardation when moving the elliptical polarized light has a greater influence by the wavelength of the incident light than the dispersion of the wavelength of the compensation film itself, resulting in a difference in the phase delay value for each wavelength of the incident light. In this case, a short wavelength light path becomes longer at point A, and color characteristic difference occurs due to RGB dispersion, so that color shift is recognized.

In order to solve the phase retardation problem for each color in the second optical compensation film of the above-described comparative example, the transverse electric field type liquid crystal display device of the present invention is formed by forming a negative A plate having a reverse dispersion wavelength characteristic.

8 is a graph comparing the optical dispersion of the second optical compensation film of the liquid crystal display device of the present invention and the A-plate of the comparative example by wavelength, and FIG. 9 is a liquid crystal display device of the present invention, which passes through the liquid crystal panel This is a diagram showing the optical path of light in the Puan Curry vector.

That is, as shown in Fig. 8, by applying the negatively dispersed A plate to the second optical compensation film performing the optical path L2, as shown in Fig. 9A, the elliptical movements of R, G, and B are the same, and the absorption of the upper polarizing element is absorbed. This is to make the L2 movement of each color to the axis A point.

As shown in Fig. 8, when applied to the transverse electric field type liquid crystal display device of the present invention, the wavelength dispersion of the first optical compensation film in contact with the second substrate surface of the liquid crystal panel is a constant dispersion (the phase delay value is small in the case of long wavelengths). It is set as a B plate, and the second optical compensation film thereon is used as a negative A plate of reverse dispersion.

At this time, as shown in FIG. 9, light exiting the liquid crystal panel and moving latitude from the S point to the southern hemisphere via the first optical compensation film moves from the S point to the D point (moves in the L1 path), and the second optical compensation film When the ellipse moves through the optical path of L2, the phase delay of the red light is relatively higher than that of the comparative example and the phase delay of the blue light is reduced by applying inverse dispersion to increase the phase delay of the long wavelength. Let the light gather at point A. Accordingly, the color shift problem is prevented, and light passing through the second optical compensation film is collected by the absorption axis of the upper polarizing element, and light leakage in the black state can be prevented.

 10A and 10B are views illustrating two-dimensionally the optical compensation path of the comparative example and the embodiment of the present invention, and FIGS. 11A and 11B are simulations showing the luminance viewing angle characteristics of the dark state of the comparative example and the embodiment of the present invention. It is.

10A and 10B are two-dimensional descriptions of the optical compensation path of the comparative example and the embodiment of the present invention, respectively.

In the case of Figure 10a, when the incident light (Tin) is located on the s2 axis, L1 moves through the first light compensation film to the s3 axis, and passes through the second optical compensation film on the s3 axis, the light stars of each R, G, B color Since the phase delay value is different, the green (G) light gathers on the absorption axis (A) of the upper polarizing element, but the phase delay of the red (R) light is less than the absorption axis of the upper polarizing element, and the phase delay of the blue (B) light Since the absorption axis of the upper polarizing element is crossed, light of each color is not collected on the absorption axis A of the upper polarizing element.

The result is that when viewed in a diagonal direction, color shift is recognized.

 On the other hand, in the case of Figure 10b, in the light compensation path of the embodiment of the present invention, the incident light (Tin) is located on the s2 axis, L1 moves through the first optical compensation film to the s3 axis, the second optical compensation film on the s3 axis When it is rough, it has a reverse dispersion characteristic, and the phase delay values of each R, G, and B colors are matched, so that the red, green, and blue (R, G, B) light passes through the same L2 optical path and the upper polarization element Collected on the absorption axis (A). This shows that the incident light is gathered on the absorption axis, indicating an excellent dark state in a black state.

Accordingly, according to an embodiment of the present invention, even when viewed in a diagonal direction, an image without color shift can be recognized.

In the black state of FIGS. 11A and 11B, when examining the luminance viewing angle characteristics of the comparative example and the embodiment of the present invention, it can be observed that the degree of light leakage is reduced in the embodiment of the present invention.

On the other hand, Table 1 shows that the experiment was performed by varying the values of refractive index anisotropy (Nz) of the first and second optical compensation films in the transverse electric field type liquid crystal display device of the present invention.

1st optical compensation film (Nz) Second optical compensation film (Nz) Color shift prevention properties 1st experiment -4.0 1.2 Good 2nd experiment -1.0 1.3 Good Third experiment -7.5 1.0 Good

As shown in Table 1, in the first experiment, the Nz value of the first optical compensation film is -4.0, and the Nz value of the second optical compensation film is 1.2, and in this case, it can be seen that color shift is prevented.

In the second experiment, the Nz value of the first optical compensation film is −1.0, and the Nz value of the second optical compensation film is 1.3, and in this case, it can be seen that color shift is prevented.

In the third experiment, the Nz value of the first optical compensation film is -7.5, and the Nz value of the second optical compensation film is 1.0. In this case, it can be seen that color shift is prevented.

Here, only one example is shown as a table, and the present invention is not limited thereto, and each of the first optical compensation films may select an Nz value from a value of -7.5 to -1.0, and the Nz values of the second optical compensation film may be 1.0 to 1.3 You can choose from a range of.

The transverse electric field type liquid crystal display device of the present invention prevents color shift by preventing light leakage defects in a dark state in a diagonal direction, and ultimately improves image quality. To this end, a liquid crystal panel and an upper polarizing element (second part) on the upper side of the liquid crystal panel Polarization element), and defines properties of the first and second optical compensation films.

That is, the first optical compensation film closest to the liquid crystal panel has a refractive index anisotropy Nz value in the range of -7.5 to -1.0, a biaxial positive B plate, and a second optical compensation film has a refractive index anisotropy Nz value of 1.0 to 1.3. It is assumed to be a negative A plate with reverse wavelength dispersion characteristics. Through this, when the incident light of all colors passes through the second polarizing element (upper polarizing element), it is collected on the absorption axis, thereby optically blocking light leakage in a dark state.

On the other hand, the present invention described above is not limited to the above-described embodiments and the accompanying drawings, it is possible that various substitutions, modifications and changes are possible within the scope without departing from the technical spirit of the present invention. It will be obvious to those with ordinary knowledge.

100: liquid crystal panel 110: first polarizing plate
111: first polarizing element 112: first support
120: second polarizing plate 121: first optical compensation film
122: second optical compensation film 123: second polarizing element
124: second support

Claims (9)

A transverse electric field type liquid crystal panel;
A first polarizing plate positioned under the transverse electric field type liquid crystal panel and including a first support and a first polarizing element;
Located directly above the transverse electric field type liquid crystal panel, the refractive index anisotropy (Nz) is -7.5 to -1.0 (where Nz = Rth / Re +0.5, Re = (nx-ny) * d, Rth = ((nx + ny) / 2-nz) * d, where nx, ny, and nz are refractive indexes in the x, y, and z directions, and d is the thickness of the film). film;
A second optical compensation film which is located on the first optical compensation film and is made of a negative reverse dispersion A plate; And
Located on the second optical compensation film, a horizontal electric field type liquid crystal display device comprising a second polarizing plate comprising a second polarizing element and a second support. According to claim 1,
The first optical compensation film has a refractive index of nz>nx> ny, characterized in that the transverse field type liquid crystal display device. According to claim 1,
The second optical compensation film has a Nz value of 1.0 to 1.3, a transverse electric field type liquid crystal display device. According to claim 3,
The second optical compensation film has a refractive index condition of nx> ny = nz. According to claim 1,
The first and second polarizing elements have a horizontal electric field type liquid crystal display device, characterized in that having an absorption axis perpendicular to each other. The method of claim 5,
A transverse electric field type liquid crystal display device, characterized in that the optical axis of the transverse electric field type liquid crystal panel and any one absorption axis of the first polarization element and the second polarization element coincide. The method of claim 6,
The light passing through the first polarizing element, the liquid crystal panel, and the first and second optical compensation films in sequence has a polarization state coinciding with the absorption axis of the second polarizing element. According to claim 1,
The first and second supports are a transverse field type liquid crystal display device, characterized in that it is made of triacetyl celluose or cyclo olefin polymer (COP) without phase delay. According to claim 1,
The transverse electric field type liquid crystal panel,
First and second substrates facing each other;
A gate line and a data line crossing each other on the first substrate to define a plurality of pixel areas;
A thin film transistor formed at an intersection of the gate line and the data line;
A pixel electrode and a common electrode formed alternately in each pixel area;
A black matrix layer formed on the second substrate corresponding to the gate line, the data line, and the thin film transistor;
A color filter layer formed on a second substrate corresponding to the pixel regions; And
A transverse electric field type liquid crystal display device comprising a liquid crystal layer between the first and second substrates.

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