KR20100037269A - Twisted nematic in-plane switching mode for liquid crystal display - Google Patents

Twisted nematic in-plane switching mode for liquid crystal display Download PDF

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Publication number
KR20100037269A
KR20100037269A KR1020080096504A KR20080096504A KR20100037269A KR 20100037269 A KR20100037269 A KR 20100037269A KR 1020080096504 A KR1020080096504 A KR 1020080096504A KR 20080096504 A KR20080096504 A KR 20080096504A KR 20100037269 A KR20100037269 A KR 20100037269A
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KR
South Korea
Prior art keywords
liquid crystal
crystal display
mode
ips
electrode
Prior art date
Application number
KR1020080096504A
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Korean (ko)
Inventor
양승수
원태영
Original Assignee
인하대학교 산학협력단
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Priority to KR1020080096504A priority Critical patent/KR20100037269A/en
Publication of KR20100037269A publication Critical patent/KR20100037269A/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1343—Electrodes
    • G02F1/134309—Electrodes characterised by their geometrical arrangement
    • G02F1/134363—Electrodes characterised by their geometrical arrangement for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/133—Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements
    • G02F1/1333—Constructional arrangements; Manufacturing methods
    • G02F1/1347—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells
    • G02F1/13471—Arrangement of liquid crystal layers or cells in which the final condition of one light beam is achieved by the addition of the effects of two or more layers or cells in which all the liquid crystal cells or layers remain transparent, e.g. FLC, ECB, DAP, HAN, TN, STN, SBE-LC cells
    • G—PHYSICS
    • G02—OPTICS
    • G02F—OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
    • G02F1/00—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics
    • G02F1/01—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour 
    • G02F1/13—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells
    • G02F1/137—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering
    • G02F1/139—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent
    • G02F1/1396—Devices or arrangements for the control of the intensity, colour, phase, polarisation or direction of light arriving from an independent light source, e.g. switching, gating or modulating; Non-linear optics for the control of the intensity, phase, polarisation or colour  based on liquid crystals, e.g. single liquid crystal display cells characterised by the electro-optical or magneto-optical effect, e.g. field-induced phase transition, orientation effect, guest-host interaction or dynamic scattering based on orientation effects in which the liquid crystal remains transparent the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell

Abstract

PURPOSE: A TN-IPS mode for improving optical permeation properties of a liquid crystal display device and a driving method thereof are provided to improve the whole optical properties by adding a common electrode to an upper plate using positive liquid crystal. CONSTITUTION: A common electrode is arranged on an upper plate. A polarizing plate is included on the upper plate and the lower plate. A positive liquid crystal is used for TN- IPS(Twisted Nematic-In-Plane Switching) liquid crystals(400,410). A liquid crystal is rotated in horizontal direction due to horizontal electric field distribution of a pixel electrode and other electrode when voltage is applied. A polarization state of the liquid crystal is changed when the light passes a liquid crystal layer.

Description

TWISTED NEMATIC IN-PLANE SWITCHING MODE FOR LIQUID CRYSTAL DISPLAY}

The present invention relates to a liquid crystal display device, and more particularly, to a transmissive liquid crystal display device using twisted nematic (TN) liquid crystals in an in-plane switching (IPS) mode.

TFT-LCD is used in various display panels. It is not only to compensate for the shortcomings of the operation modes of the liquid crystal pixel by optimizing the electrode structure or the material characteristics, but also to develop new liquid crystal operation mode. . In other words, the field angle and driving characteristics can be improved by optimizing the electric field distribution and the characteristic parameter of the liquid crystal according to the new electrode structure, but the improvement of the unit cell characteristics through the improvement of the structure cannot solve all the problems of the liquid crystal operating mode itself. Therefore, new liquid crystal operating modes must be continuously developed and verified. In order to solve the problem of lowering the light transmittance in a specific viewing angle in the conventional IPS mode liquid crystal cell, an electrode structure having an angle of 45 degrees at the top and -45 degrees at the bottom of the liquid crystal cell has been developed. The liquid crystal molecules in the pixel rotate differently in clockwise and counterclockwise directions. In the IPS mode, the light transmittance tends to remain completely dark when no voltage is applied. However, when a voltage is applied and the light transmittance is changed to a high state, light is not transmitted in the region where the opaque electrode is positioned, which results in a poor contrast ratio characteristic compared to other liquid crystal operating modes. Accordingly, various liquid crystal operating modes have been developed to compensate for the shortcomings of the IPS mode, one of which is an in-plane switching twisted nematic (IT) mode. Comparing the IT mode with the IPS mode, there is no change in the basic electrode arrangement and the direction of the polarization axis of the upper and lower plates, but the IT mode performs the liquid crystal initial alignment as in the TN mode. That is, the rubbing of the upper plate gives an initial alignment of 90 degrees, and the rubbing direction of the lower plate gives an initial alignment of 0 degrees, so that the liquid crystals are twisted by 90 degrees. The use of negative liquid crystals is also different from the IPS mode. In the IT mode, unlike the IPS mode, since the strain is generated by applying an electric field to the liquid crystal having the initial twist strain distribution to solve the twist strain distribution, there is little change in the light transmission characteristics due to the cell gap change. In addition, it has a small color shift characteristic, which is an advantage of the double IPS mode, and shows excellent color reproduction without using a compensation film. However, since the IT mode uses an opaque electrode like the IPS mode, the aperture ratio through which light is transmitted in a bright state is small when no voltage is applied. Therefore, in the present invention, a novel twisted nematic-in (TN-IPS) for improving light transmittance characteristics in a bright state based on the driving principle of an IT mode having good characteristics of a cell gap change and having a wide viewing angle characteristic such as a basic IPS mode. -plane switching mode is proposed.

Therefore, the present invention maintains the conventional advantages of the conventional IT mode liquid crystal display device by additionally forming a common electrode on the upper plate and arranging the polarizer 90 differently, so that a vertical electric field is formed so that the liquid crystals on the upper part of the pixel electrode rotate in the shape of height. It shows the effect. In addition, an object of the present invention is to provide a liquid crystal display device that facilitates transmittance control through a linear transmittance improvement and a transmittance improvement according to an aperture ratio improvement by using a positive liquid crystal and a transparent electrode.

In order to achieve the above object, the present invention is a TN-IPS liquid crystal, wherein the TN-IPS liquid crystal is provided with a common electrode, characterized in that the common electrode is disposed on the upper plate, the upper plate to form a polarizing plate The liquid crystal is a liquid crystal display device characterized in that the use of both liquid crystals.

In order to solve the problems as described above, in order to improve the light transmission characteristics of the IT mode, a new TN-IPS mode is proposed as a method of adding a common electrode to the top plate and using both liquid crystals. As a result, it has the effect of improving the overall optical properties.

In order to achieve the above object, the present invention, the electrode structure and initial liquid crystal orientation distribution of the IT mode and TN-IPS mode liquid crystal cell is shown in Figs. In the IT mode liquid crystal 130 cell, a negative liquid crystal is used, whereas in the proposed TN-IPS mode liquid crystal 230 cell, a positive liquid crystal is used, and in the case of an IT mode liquid crystal cell, a 90 degree (191) upper plate is 0 degree ( 190) but the polarizing plate direction is arranged in the case of TN-IPS mode was compensated at 90 degrees (290) in the upper plate 0 degrees (291) in the lower plate. In the case of the TN-IPS mode, the common electrode 280 which is not present in the IT mode is disposed on the upper plate. This is because the vertical electric field is formed when the voltage is applied to the lower pixel electrode 250 and the upper common electrode 280 by using the driving principle of the TN mode to rotate the liquid crystals 410 on the upper pixel electrode in the height direction. Will be displayed. In this case, the pixel electrode 250 and the common electrode 280 pass through the transparent pixel electrode to the upper plate through the transparent pixel electrode even when no voltage is applied to the initial pixel electrode by using the transparent electrode ITO. do. As the light passes through the transparent electrode, the area through which the light is transmitted, that is, the aperture ratio, is increased, unlike the IT mode. 3 and 4 illustrate the liquid crystal behavior when voltage is applied to the IT mode and TN-IPS mode liquid crystal cells. When the voltage is applied as shown in FIG. 3, the liquid crystal rotates in the horizontal direction by the horizontal electric field distribution formed between the pixel electrode and the counter electrode existing on the lower plate. At this time, the light transmitted from the lower plate passes through the liquid crystal layer between the two electrodes, and thus the polarization state of the liquid crystal is changed and eventually blocked by the polarizing plate of the upper plate, thereby obtaining a dark state in the region between the pixel electrode and the counter electrode. In contrast, the liquid crystals between the pixel electrode on the lower plate and the common electrode on the upper plate are vertically rotated by the generated electric field, but the light passing through the liquid crystals is also blocked by the polarizing plate of the upper plate, resulting in a dark state. In the TN-IPS mode, both the lateral electric field distribution by the pixel electrode and the counter electrode are formed. Looking at the characteristics of the TN-IPS mode, first of all, it accepts the advantages of the IT mode. In particular, since the IT mode is a mode based on the IPS mode, the TN-IPS mode also has a wide viewing angle characteristic, a good cell gap characteristic, and a small color change characteristic. However, in the TN-IPS mode, unlike the IT mode, since both the pixel electrode and the common electrode are transparent electrodes, the transmittance is increased because the aperture ratio is larger than that of the IT mode, and thus the contrast ratio is increased, resulting in a clearer image. It can be implemented.

5 is a graph showing a change in light transmittance according to a change in applied voltage. In the case of TN-IPS mode, the transmittance area is improved by improving the aperture ratio, and thus, the light transmittance characteristic is about 25% higher than that of the IT mode. In the IT mode, the change in transmittance due to the applied voltage rises sharply, whereas in the TN-IPS mode, the change in the transmittance decreases slowly in the applied voltage rise, so that the TN-IPS mode can be more easily controlled in controlling the transmittance of the liquid crystal cell. do.

The foregoing has somewhat broadly improved the features and technical advantages of the present invention to better understand the claims that follow. Additional features and advantages that make up the claims of the present invention will be described below. It should be appreciated by those skilled in the art that the conception and specific embodiments of the invention disclosed may be readily used as a basis for designing or modifying other structures for carrying out similar purposes to the invention.

In addition, the inventive concepts and embodiments disclosed herein may be used by those skilled in the art as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. In addition, such modifications or altered equivalent structures by those skilled in the art may be variously evolved, substituted and changed without departing from the spirit or scope of the invention described in the claims.

1 is a diagram illustrating a counter electrode, a pixel electrode, an initial liquid crystal alignment state, and a polarizer polarization direction in one unit pixel of a conventional IT mode liquid crystal display device.

FIG. 2 is a view showing a counter electrode, a pixel electrode and an initial liquid crystal alignment state, and a polarizer polarization direction in one unit pixel of a TN-IPS mode liquid crystal display according to the present invention; FIG.

3 is a view showing an alignment state of liquid crystals after voltage is applied to one unit pixel of a conventional IT mode liquid crystal display.

4 is a diagram illustrating an alignment state of liquid crystals after voltage is applied to one unit pixel of the TN-IPS mode liquid crystal display according to the present invention;

5 is a graph showing the light transmittance according to the applied voltage of the TN-IPS mode liquid crystal display according to the conventional IT mode.

<Explanation of symbols for the main parts of the drawings>

100: upper polarizer of the conventional IT mode liquid crystal display

110: upper substrate glass of the conventional IT mode liquid crystal display

120: dielectric of the upper substrate of the conventional IT mode liquid crystal display

130: liquid crystal of the conventional IT mode liquid crystal display device

140: lower substrate dielectric of the conventional IT mode liquid crystal display

150: counter electrode of lower substrate of conventional IT mode liquid crystal display

160: lower substrate glass of the conventional IT mode liquid crystal display

170: lower polarizer of the conventional IT mode liquid crystal display

180: pixel electrode of the lower substrate of the conventional IT mode liquid crystal display

190: polarization direction of the upper polarizer of the conventional IT mode liquid crystal display

191: Polarization direction of the lower polarizer of the conventional IT mode liquid crystal display

200: upper polarizer of the TN-IPS mode liquid crystal display according to the present invention

210: upper substrate glass of the TN-IPS mode liquid crystal display according to the present invention

220: upper substrate dielectric of the TN-IPS mode liquid crystal display according to the present invention

230: liquid of the TN-IPS mode liquid crystal display device according to the present invention

240: lower substrate dielectric of the TN-IPS mode liquid crystal display according to the present invention

250: counter electrode of lower substrate of TN-IPS mode liquid crystal display according to the present invention

260: lower substrate glass of the TN-IPS mode liquid crystal display according to the present invention

270: Lower polarizer of TN-IPS mode liquid crystal display according to the present invention

280: upper lower substrate pixel electrode of the TN-IPS mode liquid crystal display according to the present invention

290: polarization direction of the upper polarizer of the TN-IPS mode liquid crystal display according to the present invention

291: polarization direction of the lower polarizer of the TN-IPS mode liquid crystal display according to the present invention

300: liquid crystal behavior after applying voltage of the conventional IT mode liquid crystal display

400: liquid crystal behavior after voltage application of the TN-IPS mode liquid crystal display according to the present invention

410: Liquid crystal behavior after applying voltage on the pixel electrode of the TN-IPS mode liquid crystal display according to the present invention

Claims (2)

In the TN-IPS liquid crystal, the TN-IPS liquid crystal is provided with a common electrode, the common electrode is characterized in that disposed on the upper plate, characterized in that to form a polarizing plate on the lower plate, the liquid crystal is a positive liquid crystal The liquid crystal display device characterized by the above-mentioned.       The liquid crystal display device according to claim 1, wherein a transparent electrode is used to increase the permeability of the transmissive liquid crystal display device.
KR1020080096504A 2008-10-01 2008-10-01 Twisted nematic in-plane switching mode for liquid crystal display KR20100037269A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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