KR20180003247A - Liquid crystal display device - Google Patents

Abstract

The liquid crystal display device of the present invention includes a light valve panel formed in the lower part of a liquid crystal panel, and selectively transmits and blocks light to realize deep black in a black screen. And, the liquid crystal display of the present invention removes one polarizing plate between the liquid crystal panel and the light-valve panel and changes an external substrate having a phase difference to an isotropic substrate at the same time. According to the present invention, it is possible to obtain an improved contrast ratio, minimize the thickness of the liquid crystal display device, and improve a dark viewing angle and brightness.

Description

[0001] LIQUID CRYSTAL DISPLAY DEVICE [0002]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device having a light valve panel and having a high contrast ratio.

Recently, there has been a growing interest in information display and a demand for portable information media has increased, and research and commercialization of a light-weight flat panel display (FPD) has been focused on. Particularly, among such flat panel display devices, a liquid crystal display (LCD) is an apparatus for displaying an image using the optical anisotropy of a liquid crystal, and is excellent in resolution, color display and picture quality and is actively applied to a notebook or a desktop monitor have.

Hereinafter, the liquid crystal display device will be described in detail with reference to the drawings.

1 is a cross-sectional view schematically showing a structure of a general liquid crystal display device.

2 is a diagram illustrating an image of a general liquid crystal display device as an example, and shows an image of a typical IPS liquid crystal display device as an example.

Referring to FIG. 1, a typical liquid crystal display device includes a liquid crystal panel 10 in which pixels are arranged in a matrix form to display an image, a driving unit (not shown) and a liquid crystal panel 10 And a backlight unit 50 installed on the rear surface and supplying light to the liquid crystal panel 10.

The liquid crystal panel 10 includes a color filter substrate 1 as a first substrate and a liquid crystal layer formed between the array substrate 2 as a second substrate and the color filter substrate 1 and the array substrate 2, (5).

Upper and lower polarizers 3 and 4 are attached to the outside of the liquid crystal panel 10 and the lower polarizer 4 polarizes the light passing through the backlight unit 50. The upper polarizer 3 is a liquid crystal display, Thereby polarizing the light passing through the panel 10.

The liquid crystal display device thus constructed has a twisted nematic (TN) method in which nematic liquid crystal molecules are driven in a direction perpendicular to the substrate. However, the TN type liquid crystal display has a drawback that the viewing angle is as narrow as 90 degrees. This is due to the refractive anisotropy of the liquid crystal molecules, because liquid crystal molecules aligned horizontally with the substrate are oriented in a direction substantially perpendicular to the substrate when a voltage is applied to the liquid crystal panel.

An in-plane switching (IPS) method in which a liquid crystal molecule is driven in a horizontal direction with respect to a substrate to improve a viewing angle to 170 degrees or more is mainly used. In recent years, an IPS method having a wide viewing angle characteristic such as an S-IPS method or a fringe field switching (FFS) method has been applied to various applications.

In this general IPS type liquid crystal display device, a common electrode (not shown) and a pixel electrode (not shown) are disposed on the same array substrate 2 to generate a transverse electric field and a liquid crystal molecule is applied to a transverse electric field And the viewing angle can be improved.

However, such an IPS type liquid crystal display device has a problem that a light leakage occurs in a diagonal direction when a black state is displayed, thereby exhibiting a low contrast ratio (hereinafter referred to as a contrast ratio).

In addition, as described above, in the IPS system, the liquid crystal molecules are aligned in a horizontal direction with respect to the substrate, and the polarized light causes optical loss due to scattering / vibration of the liquid crystal molecules. Particularly, referring to FIG. 2, scattering occurs in black to increase brightness, which results in a decrease in contrast ratio.

SUMMARY OF THE INVENTION It is a first object of the present invention to provide a liquid crystal display device having a high contrast ratio.

A second object of the present invention is to provide a liquid crystal display device in which a thickness is minimized and a viewing angle and luminance of a dark state are improved.

Other objects and features of the present invention will be described in the following description of the invention and the claims.

In order to achieve the above object, the liquid crystal display according to the first and second embodiments of the present invention includes a first polarizer attached to an upper portion of a liquid crystal panel, and a second polarizer positioned below the liquid crystal panel, And a third and fourth polarizing plates attached to upper and lower portions of the light-valve panel.

In this case, according to the liquid crystal display apparatus of the second embodiment of the present invention, the third polarizer includes a third external substrate made of an isotropic material.

The liquid crystal display according to the first and second embodiments of the present invention may further include a backlight unit positioned under the light-valve panel.

The liquid crystal panel may include a first substrate bonded to each other and a second substrate, and a first liquid crystal layer provided between the first substrate and the second substrate.

The first polarizer may include a first inner substrate attached to the liquid crystal panel, a first outer substrate, and a first polarizing element positioned between the first inner substrate and the first outer substrate.

The liquid crystal panel may be driven by a TN mode or an IPS mode.

The photo-valve panel may include a third substrate bonded to the first substrate and a fourth substrate, and a second liquid crystal layer interposed between the third substrate and the fourth substrate.

The light-valve panel may be driven by a TN system or an IPS system.

The third polarizing plate and the fourth polarizing plate have absorption axes perpendicular to each other, and the first polarizing plate may have an absorption axis perpendicular to the third polarizing plate.

The third polarizer plate may include a third inner substrate attached to the light-valve panel, a third outer substrate, and a third polarizing element positioned between the third inner substrate and the third outer substrate .

The fourth polarizer plate may include a fourth inner substrate attached to the light-valve panel, a fourth outer substrate, and a fourth polarizing element positioned between the fourth inner substrate and the fourth outer substrate .

The third external substrate may be 0-TAC, O-acrylic of PMMA, or 0-COP.

The light-valve panel can selectively transmit or block light directed to the liquid crystal panel by setting a certain region or region and selectively blocking the light or the region.

The liquid crystal display according to the third embodiment of the present invention may further include an adhesive layer provided between the liquid crystal panel and the light-valve panel to directly adhere the liquid crystal panel and the light-valve panel.

As described above, the liquid crystal display device according to the first and second embodiments of the present invention realizes deep black in a black screen, thereby providing an effect of improving the contrast ratio.

Particularly, in the liquid crystal display device according to the second embodiment of the present invention, one of the polarizing plates is removed and the optical path according to the polarizing plate is compensated to minimize the viewing angle and the luminance of the dark state in a state where the thickness of the liquid crystal display device is minimized. And provides an effect that can be improved.

1 is a cross-sectional view schematically showing a structure of a general liquid crystal display device.
2 is a diagram showing an image of a general liquid crystal display device as an example.
3 is a cross-sectional view schematically showing a structure of a liquid crystal display device according to a first embodiment of the present invention.
4 is a plan view showing an example of a part of an array substrate of an in-plane switching type liquid crystal display device according to the first embodiment of the present invention.
FIG. 5 is a schematic cross-sectional view taken along line I-I 'of the array substrate shown in FIG. 4; FIG.
6 is a view showing an example of an image of a liquid crystal display device according to the first embodiment of the present invention.
7 is a view for explaining the principle of improving the contrast ratio of an image in the liquid crystal display device according to the first embodiment of the present invention.
8A is a view showing an example of color characteristics in a diagonal viewing angle in a liquid crystal display device according to the first embodiment of the present invention.
8B is a view showing an example of a luminance viewing angle characteristic in a dark state in the liquid crystal display device according to the first embodiment of the present invention.
9 is a cross-sectional view schematically showing a structure of a liquid crystal display device according to a second embodiment of the present invention.
FIG. 10 is a detailed view illustrating the structure of a liquid crystal display device according to a second embodiment of the present invention shown in FIG. 9; FIG.
11A is a view showing an example of color characteristics in a diagonal viewing angle in a liquid crystal display device of a comparative example.
11B is a view showing, by way of example, a luminance viewing angle characteristic in a dark state in a liquid crystal display device of a comparative example.
12A is a schematic view of a light transmission axis of an orthogonal upper and lower polarizer plates when viewed from the front;
FIG. 12B schematically shows the light transmission axis of the upper and lower polarizing plates orthogonal to each other when viewed in the diagonal direction; FIG.
13A and 13B are diagrams showing arbitrary elliptical polarized light in the orthogonal coordinate system and the corresponding percoke vector. FIG.
Fig. 14 is a view showing the polarization state of light passing through each optical element when viewed from the front, using a Porcocare sphere; Fig.
Figs. 15A and 15B are views showing a polarization state of light passing through each optical element when viewed from a diagonal direction, using a Porcocare sphere. Fig.
16A and 16B are views showing a polarization state of light passing through each optical element in a liquid crystal display device according to a second embodiment of the present invention using a Porcocare sphere.
17A is a view showing an example of a color characteristic in a diagonal viewing angle in a liquid crystal display device according to a second embodiment of the present invention.
17B is a view showing an example of a luminance viewing angle characteristic in a dark state in the liquid crystal display device according to the second embodiment of the present invention.
18A and 18B are views for explaining light transmission and blocking by a light valve panel in a liquid crystal display device according to a second embodiment of the present invention.
19 is a cross-sectional view illustrating a structure of a liquid crystal display device according to a third embodiment of the present invention.

Hereinafter, preferred embodiments of the optical member and the liquid crystal display device having the optical member according to the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The advantages and features of the present invention and the manner of achieving them will become apparent with reference to the embodiments described in detail below with reference to the accompanying drawings. It should be understood, however, that the invention is not limited to the disclosed embodiments, but is capable of many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, To fully disclose the scope of the invention to those skilled in the art, and the invention is only defined by the scope of the claims. Like reference numerals refer to like elements throughout the specification. The dimensions and relative sizes of the layers and regions in the figures may be exaggerated for clarity of illustration.

It will be understood that when an element or layer is referred to as being another element or "on" or "on ", it includes both intervening layers or other elements in the middle, do. On the other hand, when a device is referred to as "directly on" or "directly above ", it does not intervene another device or layer in the middle.

The terms spatially relative, "below," "lower," "above," "upper," and the like, And may be used to easily describe the correlation with other elements or components. Spatially relative terms should be understood to include, in addition to the directions shown in the drawings, terms that include the different directions of the elements in use, or in operation. For example, when inverting an element shown in the figures, an element described as "below" or "beneath" of another element may be placed "above" another element. Thus, the exemplary term "below" can include both downward and upward directions.

The terminology used herein is for the purpose of describing embodiments only and is not intended to be limiting of the invention. In the present specification, the singular form includes plural forms unless otherwise specified in the specification. &Quot; comprise "and / or" comprising ", as used in the specification, means that the presence of stated elements, Or additions.

3 is a cross-sectional view schematically showing the structure of a liquid crystal display device according to a first embodiment of the present invention.

3, the liquid crystal display according to the first embodiment of the present invention mainly includes a liquid crystal panel 110, a backlight unit 150 and a liquid crystal panel 110 positioned below the liquid crystal panel 110, And a light valve panel 120 positioned between the units 150.

The liquid crystal panel 110 includes a first substrate 101 and a second substrate 102. The first substrate 101 and the second substrate 102 are arranged such that pixels are arranged in a matrix form to output images and are opposite to each other to maintain a uniform cell gap. And a first liquid crystal layer 105 including a first liquid crystal molecule formed in a cell gap between the first substrate 101 and the second substrate 102.

A first alignment layer (not shown) and a second alignment layer (not shown) may be formed on the inner surfaces of the first substrate 101 and the second substrate 102 to contact the first liquid crystal layer 105, respectively. The initial alignment (orientation direction) of the first liquid crystal molecules can be determined by the alignment film and the second alignment film.

The first liquid crystal layer 105 may be replaced with a nanocapsule liquid crystal structure instead of the first liquid crystal molecule. In this case, the nanocapsule liquid crystal may be coated on the first substrate 101 or the second substrate 102 and then cured to form the first liquid crystal layer 105.

A common electrode (not shown) and a pixel electrode (not shown) are formed on the liquid crystal panel 110 in which the first substrate 101 and the second substrate 102 are bonded together to apply an electric field to the first liquid crystal layer 105 , And controls the voltage of a data signal applied to the pixel electrode in a state where a voltage is applied to the common electrode. Then, the first liquid crystal molecules of the first liquid crystal layer 105 rotate by dielectric anisotropy according to the electric field between the common electrode and the pixel electrode, thereby allowing light to be transmitted or blocked for each pixel to display characters or images.

At this time, a switching element (not shown) such as a thin film transistor (TFT) may be separately provided to the pixels to control the voltage of the data signal applied to the pixel electrode on a pixel-by-pixel basis.

The liquid crystal display according to the first embodiment of the present invention may be an IPS liquid crystal display, and the structure of the liquid crystal panel in this case will be described in detail with reference to the drawings.

4 is a plan view showing an example of a part of an array substrate of an IPS-mode liquid crystal display device according to the first embodiment of the present invention. In an actual liquid crystal display device, N gate lines and M data lines intersect to form MxN pixels But there is one pixel in the drawing to simplify the explanation.

5 is a schematic cross-sectional view of the array substrate shown in FIG. 4 taken along the line I-I '. FIG. 5 also shows a color filter substrate bonded to the array substrate shown in FIG.

4 and 5, a gate line 116 and a data line 117, which are vertically and horizontally arranged to define a pixel region, may be formed on a second substrate 102 as an array substrate, and a gate line 116, A thin film transistor T, which is a switching element, may be formed in an intersecting region between the data line 117 and the data line 117. [

At this time, the thin film transistor T is connected to the pixel electrode 118 through the gate electrode 131 connected to the gate line 116, the source electrode 132 connected to the data line 117, and the pixel electrode line 1181 And a drain electrode 133. The thin film transistor T is formed by a gate voltage supplied to the first insulating film 115a and the gate electrode 131 for insulation between the gate electrode 131 and the source and drain electrodes 132 and 133, 132 and a drain electrode 133. The active pattern 134 may be formed of a conductive material,

When an amorphous silicon is used as the active pattern 134, reference numeral 135 denotes an ohmic contact layer between the source / drain region of the active pattern 134 and the source / drain electrodes 132 and 133, - represents the contact layer. However, the present invention is not limited thereto, and the active pattern 134 may be formed of polycrystalline silicon, an oxide semiconductor, or an organic semiconductor, and in this case, the ohmic contact layer may be omitted.

At this time, the common line 1081 and the storage electrode 118s may be arranged in a direction parallel to the gate line 116 in the pixel region. The plurality of common electrodes 108 and the pixel electrodes 118 for switching the first liquid crystal molecules 130 by generating the transverse electric field 190 in the pixel region are arranged in a direction parallel to the data lines 117 .

At this time, the storage electrode 118s may overlap with a part of the common line 1081 below the first insulating layer 115a to form a storage capacitor Cst.

The first substrate 101 serving as a color filter substrate is provided with a thin film transistor T and a black matrix 106 for preventing light from leaking into the gate line 116 and the data line 117, A color filter 107 for realizing the color of the color filter 107 may be formed.

Referring to FIG. 3 again, a first polarizing plate 103 and a second polarizing plate 104 may be attached to the outer sides of the first substrate 101 and the second substrate 102, respectively. At this time, the second polarizing plate 104 polarizes the light transmitted through the backlight unit 150 and the light-valve panel 120, and the first polarizing plate 103 polarizes the light transmitted through the liquid crystal panel 110 have.

At this time, the first polarizing plate 103 and the second polarizing plate 104 may have absorption axes orthogonal to each other.

At this time, an antistatic layer (not shown) may be formed between the first substrate 101 and the first polarizing plate 103 or outside the first polarizing plate 103.

Next, the photo-valve panel 120 according to the first embodiment of the present invention is positioned at a lower portion of the liquid crystal panel 110 as described above, and selectively transmits / blocks the light to form a deep black ) Can be implemented.

That is, in order to overcome the limit of the contrast ratio of the IPS liquid crystal display device, the present invention is characterized in that a light-valve panel 120 capable of adjusting an amount of light according to an image is provided below the liquid crystal panel 110.

The light valve panel 120 includes a third substrate 121 and a second substrate 121 formed on the cell gap between the fourth substrate 122 and the third substrate 121 and the fourth substrate 122, And a second liquid crystal layer 125 including liquid crystal molecules.

A third polarizer 123 and a fourth polarizer 124 may be attached to the outside of the third substrate 121 and the fourth substrate 122, respectively.

The second liquid crystal layer 125 may be replaced with a nanocapsule liquid crystal structure instead of the second liquid crystal molecule.

At this time, the third polarizer 123 and the fourth polarizer 124 may have absorption axes perpendicular to each other. In addition, the first polarizing plate 103 and the third polarizing plate 123 may have absorption axes perpendicular to each other.

Though not shown, a pixel electrode connected to the thin film transistor and the thin film transistor may be formed on the fourth substrate 122. In this case, when the light valve panel 120 is driven by the IPS method, a common electrode may be formed on the fourth substrate 122 so as to be spaced apart from the pixel electrode.

A third alignment film and a fourth alignment film which are in contact with the second liquid crystal layer 125 may be formed on the inner surfaces of the third substrate 121 and the fourth substrate 122. The third alignment film and the fourth alignment film may be formed by the third alignment film and the fourth alignment film, The initial arrangement (alignment direction) of the two liquid crystal molecules can be determined.

The liquid crystal display according to the first embodiment of the present invention configured as described above is constructed so that the light from the backlight unit 150 located under the light valve panel 120 is selectively The contrast ratio of the IPS liquid crystal display device can be improved. At this time, the light-valve panel 120 can selectively transmit or block light directed to the liquid crystal panel 110 by a predetermined region or region by setting a certain region or region. At this time, the predetermined region or region may be set to include a predetermined number of sub-pixels, but the present invention is not limited thereto.

FIG. 6 is a diagram illustrating an image of a liquid crystal display device according to the first embodiment of the present invention.

7 is a diagram for explaining the principle of improving the contrast ratio of an image in the liquid crystal display device according to the first embodiment of the present invention.

6 and 7, in the liquid crystal display device according to the first embodiment of the present invention, the light-to-darkness of the lower portion of the liquid crystal panel 110 according to the degree of brightness of the image formed on the liquid crystal panel 110, It can be seen that the contrast ratio can be improved by adjusting the luminance in the valve panel 120. [

That is, light is selectively blocked in the light-valve panel 120 in a certain region of the screen where the black image is displayed, while light is blocked in the light-valve panel 120 in a certain region of the screen, It can be seen that the contrast ratio is improved by selectively transmitting light (transmission amount of light is controlled).

At this time, in the black image, the liquid crystal panel 110 may be in a voltage off state and the light-valve panel 120 may be in a voltage on state. In addition, in the white image or the intermediate-tier image, the liquid crystal panel 110 may be in a voltage-on state and the light-valve panel 120 may be in a voltage-off state. However, the present invention is not limited thereto, and may be varied depending on the driving mode of the liquid crystal (i.e., the normally black mode or the normally white mode).

8A is a view showing an example of color characteristics at a viewing angle in a diagonal direction in the liquid crystal display device according to the first embodiment of the present invention.

FIG. 8B is a view showing an example of the luminance viewing angle characteristic in the dark state in the liquid crystal display device according to the first embodiment of the present invention.

Here, FIGS. 8A and 8B illustrate the case where the IPS method is applied to the light valve panel, but the present invention is not limited thereto, and substantially the same result can be obtained even when the TN method is applied.

Referring to FIG. 8A, when a light-valve panel is provided under the liquid crystal panel to selectively transmit / block light as in the first embodiment of the present invention, deep black can be implemented in a black screen.

Referring to FIG. 8B, in the case of the liquid crystal display according to the first embodiment of the present invention, the maximum luminance value in the dark state is about 0.0024, which means that the black luminance is extremely low.

However, since the light-valve panel alone can not adjust the light amount of light incident from the backlight unit, a polarizer is provided outside the light-valve panel.

Accordingly, since the liquid crystal display according to the first embodiment of the present invention uses two polarizing plates, i.e., the second polarizing plate and the third polarizing plate, between the liquid crystal panel and the light-valve panel, the transmittance decreases and the material cost rises, The thickness of the display device is increased.

9 is a cross-sectional view schematically showing the structure of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 10 is a detailed view illustrating a structure of a liquid crystal display device according to a second embodiment of the present invention shown in FIG. 2. FIG. 10 shows components of the polarizer plate in detail.

In this case, the liquid crystal display according to the second embodiment of the present invention shown in FIG. 9 and FIG. 10 eliminates one polarizer plate between the liquid crystal panel and the light-valve panel and changes an external substrate having a phase difference to an isotropic substrate The liquid crystal display according to the first embodiment of the present invention has substantially the same configuration as that of the liquid crystal display according to the first embodiment of the present invention.

In addition, the liquid crystal display device according to the second embodiment of the present invention shown in Figs. 9 and 10 takes an IPS liquid crystal display device as an example.

9 and 10, a liquid crystal display according to a second exemplary embodiment of the present invention mainly includes a liquid crystal panel 210, a backlight unit 250 disposed below the liquid crystal panel 210, and a liquid crystal panel 210 And a light-valve panel 220 positioned between the backlight unit 250 and the backlight unit 250.

The liquid crystal panel 210 includes a first substrate 201 and a second substrate 202. The first substrate 201 and the second substrate 202 are stacked so that pixels are arranged in a matrix form to output images and are opposite to each other to maintain a uniform cell gap. And a first liquid crystal layer 205 including a first liquid crystal molecule formed in a cell gap between the first substrate 201 and the second substrate 202.

A first alignment layer (not shown) and a second alignment layer (not shown) may be formed on the inner surfaces of the first substrate 201 and the second substrate 202 to contact the first liquid crystal layer 205, respectively. The initial alignment (orientation direction) of the first liquid crystal molecules can be determined by the alignment film and the second alignment film.

The first liquid crystal layer 205 may be replaced with a nanocapsule liquid crystal structure instead of the first liquid crystal molecule. In this case, the nanocapsule liquid crystal may be coated on the first substrate 201 or the second substrate 202 and then cured to form the first liquid crystal layer 205.

Although not shown, a gate line and a data line, which are vertically and horizontally arranged to define a pixel region, may be formed on the second substrate 202, which is an array substrate, as described above. In a crossing region between the gate line and the data line, A thin film transistor can be formed.

At this time, the thin film transistor may include a gate electrode connected to the gate line, a source electrode connected to the data line, and a drain electrode connected to the pixel electrode. The thin film transistor may include a first insulating film for insulation between the gate electrode and the source / drain electrode, and an active pattern for forming a conduction channel between the source electrode and the drain electrode by a gate voltage supplied to the gate electrode.

The first substrate 201, which is a color filter substrate, may include a thin film transistor, a black matrix for preventing light from leaking into gate lines and data lines, and a color filter for implementing red, green, and blue colors have.

The first polarizer 203 may be attached to the outside of the first substrate 201 having such a structure. At this time, the first polarizing plate 203 can polarize the light passing through the liquid crystal panel 210.

In the case of the liquid crystal display according to the second embodiment of the present invention, when the second polarizing plate under the second substrate 202 is removed and the third polarizing plate 223 of the light-valve panel 220 is commonly used However, the present invention is not limited thereto. The second polarizer may be attached to the lower part of the second substrate 202 and the third polarizer 223 outside the light valve panel 220 may be removed.

At this time, an antistatic layer (not shown) may be formed between the first substrate 201 and the first polarizing plate 203 or outside the first polarizing plate 203.

The first polarizing plate 203 includes a first inner substrate 203b and a first polarizing element 203a disposed between the first outer substrate 203c and the first inner substrate 203b and the first outer substrate 203c And the like.

The first inner substrate 203b may be attached to the outside of the first substrate 201 through an adhesive (not shown).

The first polarizing element 203a may be made of polyvinyl alcohol (PVA).

The first polarizing element 203a refers to a film that can be converted into natural polarized light or polarized light. At this time, the first polarizing element 203a has a function of passing one polarized light component when the incident light is divided into two polarized light components orthogonal to each other, and has a function of absorbing, reflecting, and scattering the other polarized light component May be used.

The optical film used for the first polarizing element 203a is not particularly limited. For example, a stretched film of a polymer film containing a PVA-based resin containing iodine or a dichroic dye as a main component, An O-type polarizing element in which a liquid crystal composition containing a liquid crystal compound is oriented in a certain direction, and an E-type polarizing element in which a lyotropic liquid crystal is oriented in a certain direction.

The first inner substrate 203b may be a general protection film without phase retardation. For example, 0-RT (modified triacetyl cellulose having Rth near 0 nm) acetyl cellulose (TAC), which may be referred to as O-TAC), O-acrylic, or 0-COP (Cyclo Olefin Polymer) of PMMA. Or an ATW (Advanced True Wide) film which is a panel viewing angle compensation film.

The first external substrate 203c may be made of an anisotropic material, for example, a TAC having an Rth of about -40 nm to which a UV absorber or the like is added.

Next, the photo-valve panel 220 according to the second embodiment of the present invention is positioned below the liquid crystal panel 210 to selectively transmit / block the light, thereby realizing deep black in the black screen .

The light valve panel 220 includes a third substrate 221 and a second substrate 221 formed on the cell gap between the fourth substrate 222 and the third substrate 221 and the fourth substrate 222, And a second liquid crystal layer 225 including liquid crystal molecules.

A third polarizer 223 and a fourth polarizer 224 may be attached to the outside of the third substrate 221 and the fourth substrate 222, respectively.

The second liquid crystal layer 225 may be replaced with a nanocapsule liquid crystal structure in place of the second liquid crystal molecule.

At this time, the third polarizer 223 and the fourth polarizer 224 may have absorption axes perpendicular to each other. In addition, the first polarizing plate 203 and the third polarizing plate 223 may have absorption axes perpendicular to each other.

As described above, in the case of the liquid crystal display device according to the second embodiment of the present invention, the second polarizing plate under the second substrate 202 is removed and the third polarizing plate 223 of the light- However, the present invention is not limited thereto. The second polarizer may be attached to the lower part of the second substrate 202 and the third polarizer 223 outside the light-valve panel 220 may be removed.

Though not shown, a pixel electrode connected to the thin film transistor and the thin film transistor may be formed on the fourth substrate 222. In this case, when the light valve panel 220 is driven in the IPS mode, a common electrode may be formed on the fourth substrate 222, spaced apart from the pixel electrode. However, the present invention is not limited thereto, and the light-valve panel 220 may be driven in a TN mode. In this case, the common electrode may be formed on the third substrate 221.

A third alignment film and a fourth alignment film, which are in contact with the second liquid crystal layer 225, may be formed on the inner surfaces of the third substrate 221 and the fourth substrate 222, respectively. The third alignment film and the fourth alignment film, The initial arrangement (alignment direction) of the two liquid crystal molecules can be determined.

The third polarizing plate 223 includes a third inner substrate 223b and a third polarizing element 223a positioned between the third outer substrate 223c and the third outer substrate 223b and the third outer substrate 223c And the like.

The fourth polarizing plate 224 includes a fourth inner substrate 224b and a fourth polarizing element 224a positioned between the fourth outer substrate 224c and the fourth inner substrate 224b and the fourth outer substrate 224c. ). ≪ / RTI >

The third inner substrate 223b and the fourth inner substrate 224b may be attached to the outside of the third substrate 221 and the fourth substrate 222 through a pressure sensitive adhesive (not shown), respectively.

The third polarizing element 223a and the fourth polarizing element 224a may be made of PVA.

The third polarizing element 223a and the fourth polarizing element 224a refer to a film that can be converted into natural polarized light or polarized light in the same manner as the first polarizing element 203a described above. In this case, the third polarizing element 223a and the fourth polarizing element 224a have a function of passing one polarized light component when the incident light is divided into two polarized light components orthogonal to each other, and the other polarized light component And a function of absorbing, reflecting, and scattering light.

The optical film used for the third polarizing element 223a and the fourth polarizing element 224a is not particularly limited, and for example, a polymer film containing a PVA-based resin containing iodine or dichromatic dye as a main component An O-type polarizing element in which a liquid crystal composition containing a dichroic substance and a liquid crystal compound are aligned in a certain direction, and an E-type polarizing element in which a lyotropic liquid crystal is oriented in a certain direction.

The third inner base material 223b and the fourth inner base material 224b may be made of a general protective film having no phase delay and may be made of 0-TAC, O-acrylic, or 0-COP of PMMA, . Alternatively, the fourth inner substrate 224b may be formed of an ATW film that is a panel viewing angle compensation film.

The fourth external substrate 224c may be made of an anisotropic material, for example, a TAC having an Rth of about -40 nm to which a UV absorber or the like is added.

At this time, the third external substrate 223c according to the second embodiment of the present invention is characterized by being made of an isotropic material having no phase delay, for example, 0-TAC or O-acrylic of PMMA or 0-COP .

Compared with the first embodiment of the present invention, optical compensation is distorted by eliminating one polarizing plate (second polarizing plate or third polarizing plate), and the optical compensation is distorted by the removal of the remaining polarizing plate (third polarizing plate or second polarizing plate) Phase shift, a phase change occurs in the light passing through the polarizer due to such a phase difference, which results in a decrease in front and viewing angle performance. Particularly, when the ATW film is applied on the liquid crystal panel 210, optical compensation is not performed.

Therefore, in the second embodiment of the present invention, the third external substrate 223c is changed to an isotropic substrate having no phase difference.

Hereinafter, color characteristics and luminance viewing angle characteristics of a liquid crystal display device according to a second embodiment of the present invention will be described in detail in comparison with a liquid crystal display device of a comparative example.

At this time, it is assumed that the liquid crystal display device of the comparative example has the same configuration as that of the liquid crystal display device according to the second embodiment of the present invention, except that TAC having Rth of about -40 nm is used as the third external substrate.

FIG. 11A is a view showing, by way of example, color characteristics at a viewing angle in a diagonal direction in a liquid crystal display device of a comparative example.

FIG. 11B is a view showing, by way of example, the luminance viewing angle characteristics in the dark state in the liquid crystal display device of the comparative example.

11A and 11B show an example in which the IPS method is applied to the photo-valve panel.

Referring to FIG. 11A, it can be seen that a viewing angle light leakage occurs on a black screen in the liquid crystal display device of the comparative example. That is, it can be seen that light leakage occurs at a viewing angle of about 60 °, 120 °, 240 ° and 300 °, and shows a greenish color.

Referring to FIG. 11B, in the case of the liquid crystal display device of the comparative example, the maximum luminance value in the dark state is about 0.021, which means that the black luminance is increased as compared with the first embodiment of the present invention.

This is due to the phase difference of the external base material, which shows that the optical performance of the liquid crystal display of the comparative example is lowered.

As described above, when the IPS mode liquid crystal display device displays a dark state, leakage of light occurs in a diagonal direction, resulting in a low contrast ratio.

This problem is not a problem of the IPS liquid crystal display device itself but a problem caused by a polarizing plate generally used. That is, in general, the diagonal light leakage is more effective than the effect due to the liquid crystal layer due to the polarizing plate, and since the transverse electric field mode like the IPS liquid crystal display device can determine the initial alignment state so as not to be influenced by the liquid crystal in all directions, In the case of light, the light leakage is caused entirely by the polarizing plate.

FIG. 12A is a view schematically showing a light transmission axis of orthogonal upper and lower polarizing plates when viewed from the front. FIG.

FIG. 12B is a view schematically showing the light transmission axis of the orthogonal upper and lower polarizing plates when viewed from the diagonal direction. FIG.

12A and 12B, this is because the orthogonality of the two polarizing plates is broken along the viewing angle direction even if the polarizing plates have the light absorption axes perpendicular to each other. Here, the solid lines shown in Figs. 12A and 12B indicate, for example, the light absorption axis direction of the upper polarizer and the dotted line indicate the light absorption axis direction of the lower polarizer.

As shown in FIG. 12A, when the liquid crystal panel is viewed from the front, the optical absorption axes of the upper and lower polarizers are 90 degrees to realize a dark state. However, as shown in FIG. 12B, The light absorption axis of the upper and lower polarizers is 90 degrees or more, and light leakage occurs because the orthogonality of the two polarizers is broken.

As described above, in the IPS-mode liquid crystal display device, a lateral electric field is applied to the liquid crystal layer, and the phase delay of the liquid crystal varies with voltage, and the optical axis of the upper and lower polarizers maintains a vertical state in the up, In the diagonal direction in which the vertical state of the optical axis of the upper and lower polarizers is broken, light leakage occurs and image quality deterioration is caused.

Thus, optical compensation is performed through the substrate of the polarizing plate or the compensation film. In the case of deleting one polarizing plate as in the second embodiment of the present invention, the predetermined optical compensation is distorted. Therefore, it should be compensated by taking this into consideration, which will be explained in detail using the Poincare sphere expression.

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

First, the Jones vector can represent only the full polarization, and the Stokes parameter, which is defined as shown in Equation 1 below, is used to represent more general partial polarized light.

는 시간평균을 나타내며, 이 네 변수 사이에는

의 부등식이 성립하는데, 등식은 완전편광에서만 적용된다.At this time,

Represents the time average, and between these four variables

, The equation applies only to complete polarization.

In the case of perfect polarization, the following relationship is established between normalized variables s ₁ , s ₂ and s ₃ , which is obtained by dividing S ₁ , S ₂ and S ₃ by the brightness S ₀ of light.

This is an equation of a sphere with a radius of one in three-dimensional space, and a sphere consisting of points with (s ₁ , s ₂ , s ₃ ) as orthogonal coordinates means a pork curry sphere.

At this time, all the points on the equator line in the Poincare sphere correspond to linearly polarized light, and the north pole corresponds to the right-hand circular polarization and the south pole corresponds to the left-hand circular polarization. All points in the Northern Hemisphere correspond to right-handed elliptical polarized light, and all points in the southern hemisphere correspond to left-handed elliptical polarized light.

Figs. 13A and 13B are diagrams showing arbitrary elliptical polarized light in the orthogonal coordinate system and the corresponding percoke vector. Fig.

이다. 이 점이 북반구에 있으면 전기장 벡터의 회전방향이 시계방향이고 남반구에 있으면 반시계방향이다. 뽀앙카레 구 위의 대척점들은 서로 직교하는 편광 상태를 나타낸다.Referring to FIGS. 13A and 13B, the latitude angle of the pornographic vector P corresponding to the elliptical polarized light having the azimuth angle Ψ of the long axis of the polarization ellipse and the elliptical angle x is 2x, the azimuth angle is 2Ψ,

to be. If this point is in the northern hemisphere, the direction of rotation of the electric field vector is clockwise and counterclockwise if it is in the southern hemisphere. The opposite points on the Porcine Curve show polarized states perpendicular to each other.

In addition, the Unitary Jones matrix describing the change in polarization state when a light is transmitted through a transparent medium can be interpreted as a rotation transformation on a Porcocare sphere.

Fig. 14 is a diagram showing a polarization state of light passing through each optical element when viewed from the front, using a Porcocare sphere. Fig.

15A and 15B are views showing the polarization state of light passing through each optical element when viewed from the diagonal direction, using a Porcocare sphere.

15B corresponds to a view in which the Poincare sphere shown in FIG. 15A is viewed from the front, and FIG. 15B, which is two-dimensionally represented, shows the movement before and after the angle change in the polarization state using arrows in the drawing , It can be expressed on a porch curling sphere by rotation to a specific angle around a specific axis determined corresponding to each optical characteristic.

In this case, as described above, the Poincare sphere expresses all the polarization states of light on the spherical surface. If the optical axis and the phase delay value of the optical element are known, the polarization state can be easily predicted using the Poincare sphere. .

These ppoang all points on the sphere equator in the curry denote a linear polarizer, Pole S ₃ a right-hand circularly polarized light point, South Pole -S _3, at which point represents the left-handed circularly polarized light. In the remaining region, the northern hemisphere represents right-handed elliptical polarized light, and the southern hemisphere represents left-handed elliptical polarized light.

14, the point A and the point A 'represent the transmission axis of the absorption axis of the lower polarizer and the transmission axis of the upper polarizer when the liquid crystal display device is viewed from the front, the point B and the point B' are the transmission axis of the lower polarizer, Represents the absorption axis of the upper polarizer plate. The polarization state of the upper polarizer plate and the lower polarizer plate is symmetrical with respect to the center O of the Porcine curry sphere, and they are perpendicular to each other, and thus exhibit an excellent dark state. That is, as described above, the opposite points (A, B ') on the porch curlephere show polarized states orthogonal to each other.

14A and 14B, when the liquid crystal display device is viewed from the diagonal direction, the transmission axis A 'of the upper polarizer and the transmission axis B of the lower polarizer move a predetermined distance toward the S ₂ axis, The absorption axis B 'of the upper polarizer and the absorption axis A of the lower polarizer are shifted a predetermined distance toward the -S ₂ axis. At this time, since the points A and B 'are not symmetrical with respect to the center O, the polarization states of the upper polarizer and the lower polarizer are not perpendicular to each other.

Therefore, the optical compensation film must be used so that the optical axis of the light reaching the upper polarizer coincides with the absorption axis of the upper polarizer. Here, the polarization state of the incident light passing through the lower polarizer corresponds to point B, and the polarization state of the light absorbed and absorbed by the absorption axis of the upper polarizer corresponds to point B '.

That is, when the incident light passes through the lower polarizer plate in which the absorption axis direction is located at point A on the porcine curve, it is linearly polarized and positioned at point B. Then, the linearly polarized light passes through a homogeneous liquid crystal layer. Since the alignment direction of the liquid crystal layer is orthogonal to the polarization direction of the linearly polarized light, the linearly polarized light has no phase change in the liquid crystal layer. Therefore, the light passing through the liquid crystal layer maintains the same linearly polarized light state and has a polarization state corresponding to the point B.

In this way, in the IPS liquid crystal display device, the light leakage out of the axis in the diagonal direction is caused by the discrepancy between the points B and B '. Therefore, the optical compensation film is used to cause a change in the polarization state of the incident light from the point B to the point B ', including a change in the polarization state of the liquid crystal layer.

At this time, when viewed from the diagonal direction, the polarization state of the light passing through the optical element is firstly reflected by the third external substrate of the third polarizer plate made of TAC (corresponding to the negative C plate) having Rth of about -40 nm or so, (More precisely near the B point) to the C point. For reference, in the ideal case, point B becomes the starting point, but considering the various factors such as the pretilt angle of the actual alignment film, the point near the point B becomes the starting point.

Then, the first liquid crystal layer of the liquid crystal panel having the phase delay value of 280 nm to 350 nm moves from point C to point D. Next, the first inner substrate of the first polarizing plate as a compensating film, for example, ATW film (corresponding to the positive biaxial film), moves from point D to point E. In this case, the polarization state (point E) of light reaching the first polarizing element of the first polarizing plate does not coincide with the absorption axis (point B ') of the first polarizing element, so that the viewing angle compensation is distorted, do.

16A and 16B are views showing a polarization state of light passing through each optical element in a liquid crystal display device according to a second embodiment of the present invention using a Porcocare sphere.

Here, FIG. 16B is a diagram for two-dimensionally explaining a mechanism of compensating the optical path using the Porcocare sphere shown in FIG. 16A.

16A and 16B, when viewing an IPS-type liquid crystal display device in which an isotropic material is applied to a third external substrate in a diagonal direction according to the second embodiment of the present invention, The polarization state is not influenced by the third external substrate having the phase delay value of 0, unlike the above-described comparative example.

Then, the first liquid crystal layer of the liquid crystal panel having the phase delay value of 280 nm to 350 nm moves to the point D 'in the vicinity of the point B, as described above.

Next, the film is finally moved from the D 'point to the E' point by the first internal substrate of the first polarizer plate, which is a compensation film, for example, an ATW film (corresponding to the positive biaxial film). In this case, since the point E 'is located close to the point B', which is the absorption axis of the first polarizing element, the incident light is mostly absorbed by the first polarizing element, thereby exhibiting an excellent dark state in the diagonal direction.

As described above, according to the second embodiment of the present invention, since the path of the light that is erased by erasing the polarizing plate is compensated by the third external substrate, it has a light path similar to that of the first embodiment of the present invention.

17A is a diagram showing color characteristics at a viewing angle in a diagonal direction in a liquid crystal display device according to a second embodiment of the present invention.

17B is a view showing an example of the luminance viewing angle characteristic in the dark state in the liquid crystal display device according to the second embodiment of the present invention.

Here, FIGS. 17A and 17B show an example in which the IPS method is applied to the light-valve panel. However, the present invention is not limited thereto, and substantially the same result can be obtained even when the TN system is applied.

Referring to FIG. 17A, it can be seen that the viewing angle light leakage in the black screen of the liquid crystal display device according to the second embodiment of the present invention is improved as compared with the comparative example. That is, it can be seen that the light leakage generated at the diagonal viewing angle is reduced and the color tone of greenish is improved.

17B, in the case of the liquid crystal display according to the second embodiment of the present invention, the maximum luminance value in the dark state is about 0.0088, which means that the black luminance is much reduced as compared with the above-described comparative example. This is equivalent to the first embodiment of the present invention.

In the liquid crystal display according to the second embodiment of the present invention configured as described above, as in the first embodiment of the present invention, by driving the light-valve panel 220, It is possible to improve the contrast ratio of the IPS liquid crystal display device by selectively transmitting or blocking light from the backlight unit 250 located in the IPS mode. At this time, the light-valve panel 220 can selectively transmit or block light directed to the liquid crystal panel 210 by a predetermined region or region by setting a certain region or region. At this time, the predetermined region or region may be set to include a predetermined number of sub-pixels, but the present invention is not limited thereto.

Accordingly, in the liquid crystal display device according to the second embodiment of the present invention, one polarizing plate is removed, and the viewing angle and luminance of the dark state are minimized while the thickness of the liquid crystal display device is minimized by compensating the optical path according to the polarizing plate And provides an effect that can be improved.

18A and 18B are views for explaining light transmission and blocking by the light-valve panel in the liquid crystal display according to the second embodiment of the present invention.

18A and 18B illustrate light transmission and blocking by the light-valve panel when TN mode is applied to the light-valve panel for convenience of explanation. However, the present invention is not limited to this, and it can be seen that even when the IPS system is applied, it is driven in substantially the same manner.

At this time, the polarization states of the polarizers constituting the liquid crystal display according to the second embodiment of the present invention, specifically, the absorption axes of the polarizers are shown on the left side of FIGS. 18A and 18B.

18A, in the off-state of the light-valve panel in which no electric field is formed between the pixel electrode 227 and the common electrode 226, by the third and fourth alignment films (not shown) The long axis of the second liquid crystal molecules 230 of the second liquid crystal layer 225 is arranged in a twisted state at 90 degrees in parallel to the direction of light provided from the backlight unit (not shown).

At this time, the light provided from the backlight unit is linearly polarized in the transmission axis direction of the fourth polarizing element by the fourth polarizing plate 224, and then passes through the second liquid crystal layer 225. At this time, the polarization direction of the light passing through the second liquid crystal layer 225 is changed by 90 degrees by the second liquid crystal molecules 230 twisted by 90 degrees. Therefore, the light having passed through the second liquid crystal layer 225 passes through the third polarizing element of the third polarizing plate 223 having the transmission axis perpendicular to the polarization direction of the fourth polarizing element (in the case of the normally white mode). That is, in the off state, the light-valve panel serves as a light transmission.

18B, in the on-state of the light-valve panel in which an electric field is formed between the pixel electrode 227 and the common electrode 226, the long axis of the second liquid crystal molecules 230 is shifted from the backlight unit And arranged in parallel to the direction of the provided light.

Therefore, the light provided from the backlight unit is linearly polarized in the transmission axis direction of the fourth polarizing element, and then passes through the second liquid crystal layer 225 without changing the polarization direction. Therefore, the light having passed through the second liquid crystal layer 225 is blocked by the third polarizing element of the third polarizing plate 223 having the transmission axis perpendicular to the polarization direction of the fourth polarizing element. That is, in the ON state, the light-valve panel serves as a light shielding function.

Meanwhile, the liquid crystal panel and the light-valve panel according to the first and second embodiments of the present invention can be attached to each other by an adhesive layer. That is, the third polarizer plate of the liquid crystal panel and the light-valve panel can be attached to each other by the adhesive layer, which will be described in detail in the following third embodiment of the present invention.

FIG. 19 is a cross-sectional view illustrating a structure of a liquid crystal display device according to a third embodiment of the present invention, and shows components constituting the polarizer in detail.

In this case, the liquid crystal display according to the third embodiment of the present invention shown in Fig. 19 is different from the liquid crystal display of the second embodiment of the present invention except that the third polarizer plate of the liquid crystal panel and the light- Which is substantially the same as the embodiment.

In addition, the liquid crystal display device according to the third embodiment of the present invention shown in FIG. 19 exemplifies an IPS liquid crystal display device.

19, a liquid crystal display according to a third exemplary embodiment of the present invention mainly includes a liquid crystal panel 310, a backlight unit (not shown) and a liquid crystal panel 310 located below the liquid crystal panel 310, And a light-valve panel 320 positioned between the backlight units.

Although not shown in detail, the liquid crystal panel 310 includes a first substrate on which pixels are arranged in a matrix form to output an image, and which are bonded together so as to face each other and maintain a uniform cell gap, a second substrate, And a first liquid crystal layer including first liquid crystal molecules formed in a cell gap between the first substrate and the second substrate.

In addition, a first alignment layer and a second alignment layer, which are in contact with the first liquid crystal layer, may be formed on the inner surfaces of the first substrate and the second substrate, respectively. The initial alignment of the first liquid crystal molecules ) Can be determined.

The first liquid crystal layer may be replaced with a nanocapsule liquid crystal structure instead of the first liquid crystal molecule. In this case, the nanocapsule liquid crystal may be coated on the first substrate or the second substrate and then cured to form the first liquid crystal layer.

The first polarizing plate 303 may be attached to the outside of the upper part of the liquid crystal panel 310 having the above structure. When the light valve panel 320 is positioned above the liquid crystal panel 310, the first polarizer 303 may be positioned below the liquid crystal panel 310.

At this time, the first polarizing plate 303 can polarize light passing through the liquid crystal panel 310.

In this case, in the case of the liquid crystal display device according to the third embodiment of the present invention, the second polarizing plate under the second substrate is removed and the third polarizing plate 323 of the light-valve panel 320 is commonly used However, the present invention is not limited thereto. The second polarizer may be attached to the lower portion of the second substrate and the third polarizer 323 outside the light-valve panel 320 may be removed.

At this time, an antistatic layer (not shown) may be formed between the liquid crystal panel 310 and the first polarizing plate 303 or outside the first polarizing plate 303.

The first polarizing plate 303 includes a first inner substrate 303b and a first polarizing element 303a positioned between the first outer substrate 303c and the first inner substrate 303b and the first outer substrate 303c And the like.

The first inner substrate 303b may be attached to the outside of the liquid crystal panel 310 through an adhesive (not shown).

The first polarizing element 303a may be made of PVA.

The optical film used for the first polarizing element 303a is not particularly limited. For example, a stretched film of a polymer film containing a PVA-based resin containing iodine or a dichromatic dye as a main component, An O-type polarizing element in which a liquid crystal composition containing a compound is oriented in a certain direction, and an E-type polarizing element in which a lyotropic liquid crystal is oriented in a certain direction.

The first inner substrate 303b may be made of a general protective film having no phase delay, for example, 0-TAC, O-acrylic of PMMA, 0-COP, or the like. Or an ATW film as a panel viewing angle compensation film.

The first external substrate 303c may be made of an anisotropic material, and may be made of TAC having an Rth of about -40 nm to which an UV absorber or the like is added.

Next, the photo-valve panel 320 according to the third embodiment of the present invention is positioned below the liquid crystal panel 310 to selectively transmit / block the light, thereby realizing deep black in the black screen .

Although not shown in detail, the light-valve panel 320 includes a third substrate bonded to each other and a fourth substrate, a second liquid crystal layer 322 including second liquid crystal molecules formed in the cell gap between the third substrate and the fourth substrate, Layer.

At this time, a third alignment film and a fourth alignment film, which are in contact with the second liquid crystal layer, respectively, may be formed on the inner surfaces of the third substrate and the fourth substrate, and the initial alignment of the second liquid crystal molecules may be determined by the third alignment film and the fourth alignment film have.

In addition, a third polarizing plate 323 and a fourth polarizing plate 324 may be attached to the outside of the light-valve panel 320, that is, the third substrate and the fourth substrate.

The second liquid crystal layer may be replaced with a nanocapsule liquid crystal structure instead of the second liquid crystal molecule.

At this time, the third polarizing plate 323 and the fourth polarizing plate 324 may have absorption axes perpendicular to each other. In addition, the first polarizing plate 303 and the third polarizing plate 323 may have absorption axes perpendicular to each other.

As described above, in the case of the liquid crystal display device according to the third embodiment of the present invention, the second polarizing plate under the liquid crystal panel 310 is removed and the third polarizing plate 323 of the light-valve panel 320 is commonly used However, the present invention is not limited thereto. The present invention can also attach a second polarizing plate to the lower part of the liquid crystal panel 310 and remove the third polarizing plate 323 outside the light-valve panel 320.

The third polarizing plate 323 includes a third inner substrate 323b and a third polarizing element 323a positioned between the third outer substrate 323c and the third outer substrate 323b and the third outer substrate 323c And the like.

The fourth polarizing plate 324 includes a fourth inner substrate 324b and a fourth outer polarizing element 324a positioned between the fourth outer substrate 324c and the fourth inner substrate 324b and the fourth outer substrate 324c. ). ≪ / RTI >

The third inner substrate 323b and the fourth inner substrate 324b may be attached to the outside of the third substrate 321 and the fourth substrate 322 through a pressure sensitive adhesive (not shown), respectively.

The third polarizing element 323a and the fourth polarizing element 324a may be made of PVA.

The optical film used for the third polarizing element 323a and the fourth polarizing element 324a is not particularly limited. For example, a polymer film containing a PVA-based resin containing iodine or dichroic dye An O-type polarizing element in which a liquid crystal composition containing a dichroic substance and a liquid crystal compound are aligned in a certain direction, and an E-type polarizing element in which a lyotropic liquid crystal is oriented in a certain direction.

The third inner substrate 323b and the fourth inner substrate 324b may be made of a general protective film having no phase delay and may be made of O-TAC, O-acrylic, or 0-COP of PMMA, . Alternatively, the fourth inner substrate 324b may be made of an ATW film which is a panel viewing angle compensation film.

The fourth external substrate 324c may be made of an anisotropic material, for example, a TAC having an Rth of about -40 nm added with a UV absorber or the like.

In this case, the third external substrate 323c according to the third embodiment of the present invention may be formed of an isotropic material having no phase delay, for example, 0-TAC or O-acrylate of PMMA, as in the second embodiment of the present invention described above. , 0-COP, and the like.

Therefore, according to the third embodiment of the present invention, as the path of the light that is distorted by the deletion of the polarizing plate is compensated by the third external substrate 323c, it has a light path similar to the first and second embodiments of the present invention do.

The liquid crystal display according to the third embodiment of the present invention having the above-described structure is constructed in the same manner as the first and second embodiments of the present invention by driving the light-valve panel 320, 320, the contrast ratio of the IPS-mode liquid crystal display device can be improved by selectively transmitting or blocking the light from the backlight unit disposed under the liquid crystal display device. At this time, the light-valve panel 320 can selectively transmit or block light directed to the liquid crystal panel 310 by a predetermined region or region by setting a certain region or region. At this time, the predetermined region or region may be set to include a predetermined number of sub-pixels, but the present invention is not limited thereto.

Therefore, in the liquid crystal display device according to the third embodiment of the present invention, one of the polarizers is eliminated, and the viewing angle and the luminance of the dark state are minimized while the thickness of the liquid crystal display device is minimized by compensating the optical path along the polarizer And provides an effect that can be improved.

Particularly, in the liquid crystal display device according to the third embodiment of the present invention, the liquid crystal panel 310 and the third polarizing plate 323 of the light-valve panel 320 are attached to each other by the adhesive layer 360 do.

In the liquid crystal display according to the first and second embodiments of the present invention, an air gap exists between the liquid crystal panel and the light-valve panel, thereby causing a luminance loss due to interface reflection. In contrast, in the liquid crystal display device according to the third embodiment of the present invention, the interface reflection is suppressed as the liquid crystal panel 310 and the light-valve panel 320 are attached to each other by the adhesive layer 360, Can be minimized.

While a great many are described in the foregoing description, it should be construed as an example of preferred embodiments rather than limiting the scope of the invention. Therefore, the invention should not be construed as limited to the embodiments described, but should be determined by equivalents to the appended claims and the claims.

103, 203, 303: first polarizer 110, 210, 310: liquid crystal panel
120, 220, 320: light-valve panel 123, 223, 323: third polarizer plate
124, 244, 324: fourth polarizer 150, 250: backlight unit
360: Adhesive layer

Claims (13)

A first polarizer attached to an upper portion of the liquid crystal panel;
A light valve panel positioned below the liquid crystal panel and selectively transmitting or blocking light to the liquid crystal panel; And
And third and fourth polarizers attached to upper and lower portions of the light-valve panel,
Wherein the third polarizer comprises a third external substrate made of an isotropic material. The liquid crystal display of claim 1, further comprising a backlight unit located below the light-valve panel. The liquid crystal display device according to claim 1,
A first substrate and a second substrate bonded together facing each other; And
And a first liquid crystal layer provided between the first substrate and the second substrate. The liquid crystal display according to claim 1,
A first inner substrate attached to the liquid crystal panel;
A first outer substrate; And
And a first polarizing element positioned between the first inner substrate and the first outer substrate. The liquid crystal display of claim 1, wherein the liquid crystal panel is driven by a TN mode or an IPS mode. The light-valve panel according to claim 1,
A third substrate and a fourth substrate bonded together facing each other; And
And a second liquid crystal layer provided between the third substrate and the fourth substrate. The liquid crystal display of claim 1, wherein the light-valve panel is driven by a TN system or an IPS system. The liquid crystal display of claim 1, wherein the third polarizer and the fourth polarizer have mutually perpendicular absorption axes, and the first polarizer has an absorption axis perpendicular to the third polarizer. The liquid crystal display according to claim 1, wherein the third polarizer comprises:
A third inner substrate attached to the light-valve panel;
A third outer substrate; And
And a third polarizing element positioned between the third inner substrate and the third outer substrate. The liquid crystal display according to claim 1, wherein the fourth polarizer comprises:
A fourth inner substrate attached to the light-valve panel;
A fourth outer substrate; And
And a fourth polarizing element positioned between the fourth inner substrate and the fourth outer substrate. The liquid crystal display of claim 1, wherein the third external substrate comprises 0-TAC, O-acrylic, or 0-COP of PMMA. The liquid crystal display of claim 1, wherein the light-valve panel selectively transmits or blocks light directed to the liquid crystal panel by a predetermined region or region. The liquid crystal display of claim 1, further comprising an adhesive layer disposed between the liquid crystal panel and the light-valve panel to directly adhere the liquid crystal panel and the light-valve panel.

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