JP2008020725A - Liquid crystal display and video display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a liquid crystal display having a liquid crystal panel capable of enhancing display characteristics by capturing ionic impurities mixed in a liquid crystal layer at a peripheral part of each pixel electrode and to provide a video display. <P>SOLUTION: The transmission type liquid crystal panel 1 provided with: a TFT substrate 3 wherein a plurality of pixel electrodes 8 are formed in a matrix shape and shielding electrodes 6 are formed in regions between pixel electrodes; a counter substrate 2 disposed via a prescribed gap from the TFT substrate; and a liquid crystal layer 4 held in the gap between the TFT substrate and the counter substrate, wherein there is a prescribed potential difference between a potential V applied to the shielding electrode and a potential Vcom applied to a transparent electrode 9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a liquid crystal display device and a video display device. Specifically, the present invention relates to a liquid crystal display device and a video display device having a liquid crystal panel with high display quality.

  As shown in FIG. 4, the liquid crystal panel constituting the liquid crystal display device is configured by sandwiching a liquid crystal layer 203 between a drive circuit substrate 201 and a transparent substrate 202 which are disposed facing each other. Electrodes 204 are provided on the opposing surface side of the pixel region (effective pixel region) indicated by A and the opposing surface side of the transparent substrate. The electrodes are covered with alignment films 205 and 206, respectively, and the alignment state of the liquid crystal molecules contained in the liquid crystal layer is controlled by these alignment films. Further, between the drive circuit substrate and the transparent substrate, the liquid crystal is sealed with a sealant 207 provided in the peripheral region of the pixel region (the region indicated by the symbol B and hereinafter simply referred to as “peripheral region”). The layer is filled and sealed between the drive circuit board and the transparent substrate.

  Here, in the liquid crystal panel configured as described above, it is known that the ionic impurity I dissolves from the sealant during liquid crystal injection or subsequent driving, leading to deterioration of the display characteristics of the liquid crystal panel. It has also been known that the start time of occurrence of this deterioration depends on the distance from the sealant to the pixel region.

Therefore, display devices having various configurations for the purpose of suppressing such deterioration of display characteristics have been proposed.
For example, in Patent Document 1, by using surface modification by ultraviolet irradiation, the surface energy of the alignment film located in the peripheral region is made higher than the surface energy of the alignment film in the pixel region located in the center of the liquid crystal panel. A display device that suppresses diffusion of ionic impurities dissolved from the sealing agent by setting is proposed. Patent Document 2 proposes a display device that suppresses diffusion of ionic impurities to the pixel region in the same manner as Patent Document 1 by providing an alignment film having high ion adsorptivity in the peripheral region. Further, Patent Document 3 proposes a display device in which the ability to adsorb and capture ionic impurities dissolved from the sealant is improved in an ion adsorption portion provided between the sealant and the pixel region.

In addition, as shown in FIG. 5, in the image display by the liquid crystal panel, a voltage is applied between the pixel electrode 210 formed on the drive circuit substrate and the transparent electrode 211 formed on the transparent substrate, and the pixel electrode and the transparent electrode are displayed. The light transmittance is controlled based on the birefringence characteristics of the liquid crystal substance held in the gap.
In addition, in the gap between the pixel electrodes (the region indicated by reference symbol C, hereinafter referred to as “between pixel electrodes”), there is no pixel electrode to which a voltage is applied, and there is a concern about poor alignment of liquid crystal molecules. Therefore, a shielding electrode 212 is provided in a region corresponding to between the pixel electrodes, and the same potential (Vcom) as that of the transparent electrode is applied to the shielding electrode, thereby improving the orientation of the liquid crystal molecules.

JP-A-10-260406 JP-A-7-110479 Japanese Patent Laid-Open No. 2005-283693

  By the way, although it is ideal that no impurities are mixed in the liquid crystal layer filled and sealed between the drive circuit substrate and the transparent substrate, in the process until the liquid crystal layer is filled and sealed, It was thought that ionic impurities were mixed in the liquid crystal layer, and it was found that the ionic impurities mixed in the liquid crystal layer also caused display deterioration of the liquid crystal panel.

  For example, as shown in FIG. 6, when a potential is applied to the pixel electrode so that the pixel area is equally divided into nine and a white and black checker pattern is displayed, that is, an area indicated by a symbol (X) in FIG. A potential that causes a predetermined potential difference from the transparent electrode is applied to the pixel electrode (for example, 1 V is applied to the transparent electrode and 5 V is applied to the pixel electrode) to display white, and a symbol (Y) in FIG. When black is displayed by applying the same potential (for example, 1 V) as the transparent electrode to the pixel electrode in the region, the ionic impurities in the liquid crystal layer in the region indicated by the symbol (X) in FIG. (For example, in the upper right direction in FIG. 6), ionic impurities stay in the boundary portion of each region obtained by dividing the pixel region indicated by the symbol (Z) in FIG. As a result, the effective voltage drops, and as a result, the boundary part is seized Elephant is considered that lead to display deterioration of the liquid crystal panel occurs.

  The present invention has been devised in view of the above points, and it is possible to improve display characteristics by capturing ionic impurities mixed in the liquid crystal layer at the periphery of each pixel electrode. An object of the present invention is to provide a liquid crystal display device and a video display device.

  In order to achieve the above object, a liquid crystal display device according to the present invention is a drive in which a plurality of pixel electrodes are formed in a matrix and a shielding electrode is formed at least in a region corresponding to a gap between the pixel electrodes. In a liquid crystal display device comprising a circuit board, a transparent substrate disposed with a predetermined gap from the drive circuit board, and a liquid crystal layer held in the gap between the drive circuit board and the transparent substrate, the shielding electrode The applied potential has a predetermined potential difference from the potential applied to the transparent electrode provided on the transparent substrate.

  In order to achieve the above object, in the video display device according to the present invention, a plurality of pixel electrodes are formed in a matrix and a shielding electrode is formed at least in a region corresponding to a gap between the pixel electrodes. A liquid crystal display device having a driving circuit board, a transparent substrate disposed with a predetermined gap from the driving circuit board, and a liquid crystal layer held in the gap between the driving circuit board and the transparent substrate, In a video display device that performs video display using light modulated by a liquid crystal display device, a potential applied to the shielding electrode has a predetermined potential difference from a potential applied to a transparent electrode provided on the transparent substrate. .

  Here, since the potential applied to the shielding electrode has a predetermined potential difference from the potential applied to the transparent electrode provided on the transparent substrate, the ionic impurities mixed in the liquid crystal layer are removed from the shielding electrode and the transparent electrode. Can be captured in the gap.

  In the liquid crystal display device and the video display device to which the present invention is applied, ionic impurities mixed in the liquid crystal can be captured in the gap between the shielding electrode and the transparent electrode, and display characteristics can be improved.

Hereinafter, embodiments of the present invention will be described with reference to the drawings to facilitate understanding of the present invention.
FIG. 1 is a schematic view for explaining a liquid crystal panel portion in a transmissive liquid crystal display device which is an example of a liquid crystal display device to which the present invention is applied. The transmissive liquid crystal panel 1 shown here is opposed to each other so as to face each other. A liquid crystal material (for example, a liquid crystal material having a negative dielectric anisotropy) is filled and sealed between a substrate 2 (an example of a transparent substrate) and a TFT substrate 3 (an example of a drive circuit substrate), and the liquid crystal material is filled and sealed. Thus, the liquid crystal layer 4 as a light modulation layer is configured.

Here, the counter substrate is made of a translucent material substrate such as quartz, glass, plastic, etc., and a transparent electrode 5 having light transmissivity is formed over the entire surface on the counter surface of the translucent material substrate. An alignment film 9 (for example, a vertical alignment film formed by the SiO ₂ oblique deposition method) is formed so as to cover the transparent electrode. This transparent electrode is made of, for example, a transparent conductive material such as ITO (Indium-Tin Oxide), which is a solid solution material of tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ), and is common to all pixel regions. A potential Vcom (for example, 7 V) is applied.

  In addition, the TFT substrate includes a gate line (not shown) arranged in the row direction, a data line (not shown) arranged in the column direction, and a TFT (Thin Film) arranged at the intersection of the gate line and the data line. A switching element (not shown) such as a transistor element is formed, and a shielding electrode 6 for shielding incident light to the TFT element, the gate line and the data line is formed on the opposite surface side of the TFT substrate. The shielding electrode is configured to be applied with a potential V (for example, 8 V) having a predetermined potential difference from the potential applied to the transparent electrode.

Further, a plurality of substantially rectangular pixel electrodes 8 made of a transparent conductive film such as ITO are arranged in a matrix on the upper layer of the shielding electrode with a protective film 7 interposed therebetween. The alignment film 9 covers the pixel electrode. (For example, a vertical alignment film formed by SiO ₂ oblique deposition) is formed.

In the present embodiment, the width of the shielding electrode indicated by symbol b in FIG. 1 is configured to be substantially the same as the width between the pixel electrodes indicated by symbol a in FIG.
Here, since the shielding electrode shields the incident light to the liquid crystal panel, the shielding electrode is reflected when the width of the shielding electrode is larger than the width between the pixel electrodes. On the other hand, when the width of the shielding electrode is extremely smaller than the width between the pixel electrodes, there is no electrode to which voltage is applied in the gap between the pixel electrode and the shielding electrode. Concerned. Therefore, in this embodiment, the width of the shielding electrode is configured to be substantially the same as the width between the pixel electrodes.

  FIG. 2 is a schematic view for explaining a liquid crystal panel portion in a reflection type liquid crystal display device which is another example of the liquid crystal display device to which the present invention is applied. The reflection type liquid crystal panels 11 shown here are arranged facing each other. A liquid crystal material (for example, a liquid crystal material having a negative dielectric anisotropy) is filled and sealed between the counter substrate 12 (an example of a transparent substrate) and a silicon substrate 13 (an example of a drive circuit substrate). A liquid crystal layer 14 as a light modulation layer is constituted by the liquid crystal material.

Here, the counter substrate is made of a light-transmitting material substrate such as quartz, glass, plastic, etc., like the above-described transmissive liquid crystal panel, and a transparent material having light transmittance on the surface facing the light-transmitting material substrate. An electrode 15 is formed over the entire surface, and an alignment film 19 (for example, a vertical alignment film formed by SiO ₂ oblique deposition) is formed so as to cover the transparent electrode. The transparent electrode is configured so that a common potential Vcom (for example, 7 V) is applied to all pixel regions.

  In addition, the silicon substrate includes a switching drive circuit including, for example, a C-MOS (Complementary-Metal Oxide Semiconductor) type or n-channel MOS type FET (Field Effect Transistor) and a capacitor serving as an auxiliary capacitor for supplying a voltage to the liquid crystal layer. A data line (not shown) formed by arranging a plurality of pixels (not shown) in a matrix for each pixel and electrically connected to the source electrode of each FET and electrically connected to the gate electrode of each FET A plurality of gate lines (not shown) formed side by side in a direction perpendicular to each other. Further, a shielding electrode 16 is formed on the opposite surface side of the silicon substrate, and a potential V (for example, 8 V) having a predetermined potential difference from the potential applied to the transparent electrode is applied to the shielding electrode. Has been.

In addition, a plurality of substantially rectangular pixel electrodes 18 electrically connected to the drain electrodes of the FETs via the protective film 17 are formed in a matrix on the upper layer of the shielding electrode so as to cover the pixel electrodes. An alignment film 19 (for example, a vertical alignment film formed by a SiO ₂ oblique deposition method) is formed.

  In addition, the pixel electrode has a high reflectance in the visible region, for example, aluminum (Al), specifically, copper (Cu) or silicon (Si) used for wiring in the LSI process is added by several weight percent or less. It consists of a metal film mainly composed of aluminum (Al). This pixel electrode has a function of reflecting light incident from the counter substrate side and a function of applying a voltage to the liquid crystal layer. In order to further increase the reflectance, a multilayer film such as a dielectric mirror is made of Al. It may be laminated on the film.

  Here, in the case of the transmissive liquid crystal panel described above, the width of the shielding electrode is configured to be substantially the same as the width between the pixel electrodes. In this embodiment, however, the shielding is indicated by a symbol d in FIG. The width of the electrodes is configured to be larger than the width between the pixel electrodes indicated by the symbol c in FIG. This is because the shielding electrode is not reflected even when the width of the shielding electrode is larger than the width of the pixel electrode.

  In the transmissive liquid crystal panel and the reflective liquid crystal panel configured as described above, by applying a potential to the shielding electrode, the orientation of liquid crystal molecules between the pixel electrodes can be improved, and the shielding electrode Since the applied potential has a predetermined potential difference from the potential applied to the transparent electrode, the ionic impurities mixed in the liquid crystal layer can be captured between the pixel electrodes, and the display quality of the liquid crystal panel is reliable. The improvement in performance is realized.

Here, with respect to the transmission type liquid crystal panel described above, the potential applied to the shielding electrode is changed with reference to the potential applied to the transparent electrode, and how the alignment stability between the burn-in and the pixel electrode changes. Was conducted.
Here, in the burn-in evaluation, after displaying a checker pattern of white (1 V is applied to the transparent electrode, 5 V is applied to the pixel electrode) and black (1 V is applied to the transparent electrode and the pixel electrode) for 3 hours, a halftone raster screen is displayed. The remaining condition (burn-in) of the checker pattern was evaluated as (applying 1 V to the transparent electrode and applying approximately 2 V to the pixel electrode).
As for the alignment stability between the pixel electrodes, the white alignment state (1 V was applied to the transparent electrode and 5 V was applied to the pixel electrode) was observed with a microscope. At this time, the polarizing plate was rotated with respect to the liquid crystal panel while maintaining the crossed nicols, thereby evaluating whether or not the azimuth angle component of the liquid crystal alignment was in the normal direction.
In Table 1, “applied potential” means “(potential applied to transparent electrode (1V)) − (potential applied to shielding electrode)”. In Table 1, “alignment rank” means the evaluation result regarding the alignment stability between the pixel electrodes shown in Table 3.

As shown in Table 1, it was found that the seizure and the alignment stability change by changing the magnitude of the applied potential. It was also found that the transmissive liquid crystal panel described above is an optimal condition that can satisfy both image sticking and alignment stability when the applied potential is -1 (V).
In the transmissive liquid crystal panel described above, it was confirmed that the applied potential of -1 (V) was the optimum condition, but the optimum condition for seizure varies depending on the liquid crystal material, the sealing agent, and the like. .

  FIG. 3 is a schematic diagram for explaining a transmissive liquid crystal projector which is an example of a video display device to which the present invention is applied. A transmissive liquid crystal display device using the transmissive liquid crystal panel shown in FIG. 1 is used for the three light valves corresponding to the three primary colors, and a projection-type image that displays an enlarged color image on a screen (not shown). It is a video display device.

  Specifically, the transmissive liquid crystal projector includes a lamp 101 that is a light source that emits illumination light, an R dichroic mirror 103R that reflects only red light (R) among illumination light from the lamp, and illumination light from the lamp. Among them, a G dichroic mirror 103G that reflects only green light (G), and an R light valve 104R that is a light modulation means that modulates and transmits red light (R), green light (G), and blue light (B). , G light valve 104G and B light valve 104B, dichroic prism 105 which is a combining optical means for combining modulated red light (R), green light (G), and blue light (B), and combined illumination light And a projection lens 106 which is a projection means for projecting the image onto the screen.

  Here, the lamp emits white light including red light (R), green light (G), and blue light (B), and includes, for example, a halogen lamp, a metal halide lamp, a xenon lamp, or the like.

  Further, in the optical path between the lamp and the R dichroic mirror, a filter 109 that cuts infrared rays and ultraviolet rays, a fly-eye lens 107 that equalizes the illuminance distribution of the illumination light emitted from the lamp, and the P of the illumination light , A polarization conversion element 108 for converting the S polarization component into one polarization component (for example, S polarization component) is disposed.

  The projection lens has a function of enlarging and projecting light from the dichroic prism toward the screen.

  In the transmissive liquid crystal projector configured as described above, white light emitted from the lamp is separated into red light (R), green light (G), and blue light (B) by the R dichroic mirror and the G dichroic mirror. . The separated red light (R), green light (G), and blue light (B) are incident on each light valve via the condenser lens 112. Red light (R), green light (G), and blue light (B) incident on each light valve are subjected to polarization modulation in accordance with a driving voltage applied to each pixel of each light valve, and then are dichroic prism. The synthesized light is enlarged and projected on the screen by the projection lens.

  By the way, the transmissive liquid crystal display device constituting each light valve can improve the orientation of the liquid crystal molecules between the pixel electrodes as described above, and can remove the ionic impurities mixed in the liquid crystal layer. Since it can be captured between the pixel electrodes, the reliability of display quality can be improved also in the transmission projector shown here.

  In this embodiment, a projection type image display device that projects onto a screen like a transmission type projector has been described as an example. However, the present invention is a direct view type image in which a transmission type liquid crystal display device is directly viewed. The present invention can be widely applied to display devices.

It is a schematic diagram for demonstrating the liquid crystal panel part in the transmissive liquid crystal display device which is an example of the liquid crystal display device to which this invention is applied. It is a schematic diagram for demonstrating the liquid crystal panel part in the reflection type liquid crystal display device which is another example of the liquid crystal display device to which this invention is applied. It is a schematic diagram for demonstrating the transmissive liquid crystal projector which is an example of the video display apparatus to which this invention is applied. It is a schematic diagram (1) for demonstrating the conventional liquid crystal panel. It is a schematic diagram (2) for demonstrating the conventional liquid crystal panel. It is a schematic diagram for demonstrating the image sticking phenomenon.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Transmission type liquid crystal panel 2 Opposite substrate 3 TFT substrate 4 Liquid crystal layer 5 Transparent electrode 6 Shielding electrode 7 Protective film 8 Pixel electrode 9 Orientation film 11 Reflective liquid crystal panel 12 Counter substrate 13 Silicon substrate 14 Liquid crystal layer 15 Transparent electrode 16 Shielding electrode 17 Protective film 18 Pixel electrode 19 Alignment film 100 Transmission type liquid crystal projector 101 Lamp 103R R dichroic mirror 103G G dichroic mirror 104R R light valve 104G G light valve 104B B light valve 105 Dichroic prism 106 Projection lens 107 Fly eye lens 108 Polarization conversion element 109 Filter 110 Total reflection mirror 111 Relay lens 112 Condenser lens

Claims (3)

A drive circuit substrate in which a plurality of pixel electrodes are formed in a matrix and a shielding electrode is formed at least in a region corresponding to a gap between the pixel electrodes;
A transparent substrate disposed via a predetermined gap with the drive circuit substrate;
In a liquid crystal display device comprising a liquid crystal layer held in a gap between the drive circuit substrate and the transparent substrate,
The liquid crystal display device, wherein the potential applied to the shielding electrode has a predetermined potential difference from the potential applied to the transparent electrode provided on the transparent substrate. The liquid crystal display device according to claim 1, wherein the pixel electrode is made of a transmissive material, and the width of the shielding electrode is substantially the same as a gap between the pixel electrodes. A plurality of pixel electrodes are formed in a matrix, and at least a driving circuit board having a shielding electrode formed in a region corresponding to a gap between the pixel electrodes, and the driving circuit board is disposed with a predetermined gap therebetween A liquid crystal display device having a transparent substrate and a liquid crystal layer held in a gap between the drive circuit substrate and the transparent substrate;
In a video display device that performs video display using light modulated by the liquid crystal display device,
The potential applied to the shielding electrode has a predetermined potential difference from the potential applied to the transparent electrode provided on the transparent substrate.

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