JP2006276370A - Liquid crystal panel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a Cson Gate type active matrix liquid crystal display panel which can have a high aperture ratio while it has high-definition constitution. <P>SOLUTION: This liquid crystal display panel 10 has a plurality of signal lines Ym, Ym+1, and Ym+2 and scanning lines Xn and Xn+1 arranged in matrix on a light-transmissive substrate, pixel transistors 14 arranged nearby intersections of the signal lines Ym, Ym+1, and Ym+2 and scanning lines Xn and Xn+1, pixel electrodes 12 which are arranged at positions surrounded by the signal lines and scanning lines and connected to the pixel transistors 14, and auxiliary capacity electrodes 13 provided below the pixel electrodes 12. In this case, the scanning lines Xn and Xn+1 are made of light blocking members and the signal and include extension portions 21 which are wider than signal lines extending to the lower part of the signal lines Ym, Ym+1, and Ym+2, and the auxiliary capacity electrodes 13 are electrically connected to the extension portions 21 of the scanning lines. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a liquid crystal display panel, and more particularly, to a Cson Gate type active matrix liquid crystal display panel that can achieve a high aperture ratio while being high definition.

First, a general configuration of a conventional active matrix liquid crystal display panel is shown in FIG. 5 which is a plan view of several pixel portions, and a schematic equivalent circuit diagram of one pixel portion of FIG. 6 and FIG. This will be briefly described with reference to FIG. In the conventional liquid crystal display panel 10A, a region surrounded by scanning lines Xn, Xn + 1,... And signal lines Ym, Ym + 1,. pixel electrodes 12 are provided, the pixel electrode 12 are equivalently represented by a liquid crystal capacitance C _LC in FIG. 6 for each. Usually the liquid crystal capacitance C _LC auxiliary capacitance Cs formed by the auxiliary capacitance electrodes 13 are connected in parallel. One end of the liquid crystal capacitance C _LC is connected to the pixel transistor 14 for driving, the other end is connected to a counter electrode 16 provided through the color filter layer CF to the second light-transmitting substrate 15 a predetermined Common potential Vc is applied.

The pixel transistor 14 comprises an insulated gate field effect type thin film transistor TFT (Thin Film Transistor), and its source electrode S is connected to signal lines Ym, Ym + 1. electrode D is connected through a contact hole 17 at one end of the liquid crystal capacitance C _LC, i.e., the pixel electrode 12. Further, the gate electrode G of the pixel transistor 14 is connected to the scanning lines Xn, Xn + 1... So that a gate pulse Vg having a predetermined voltage is applied. In the liquid crystal display panel 10A shown here, the first light-transmitting property is provided so as to cover each pixel transistor 14, the scanning lines Xn, Xn + 1... And the signal lines Ym, Ym + 1. An interlayer film 19 is provided on the entire surface of the substrate 11 so as to have a predetermined height through the insulating film 18, and the pixel electrode is provided on the surface of the interlayer film 19 so that the cell gap is kept constant. And connected to the drain electrode D of a predetermined pixel transistor 14 through a contact hole 17. A liquid crystal 20 is sealed between the pixel electrode 12 and the counter electrode 16.

In the liquid crystal display panel 10A, a coupling capacitor _CGD is formed between the liquid crystal capacitor _CLC and the gate electrode G. The coupling capacitance _CGD is a combination of the stray capacitance component between the pixel electrode 12 and the gate line Xn and the parasitic capacitance component between the drain region and the gate region inside the pixel transistor 14, and the latter parasitic capacitance component. Is dominant, and its value varies considerably depending on the individual pixel transistor 14.

The voltage waveform of each part of this one pixel will be described with reference to FIG. In the liquid crystal display panel 10A, the common potential Vc applied to the counter electrode 16 is periodically inverted, and the image signal Vs applied to the signal lines Ym, Ym + 1. A bias voltage to be inverted is superimposed. First, when the gate pulse Vg is applied to the gate electrode G during the selection period of a predetermined pixel, the pixel transistor 14 of this pixel is turned on. At this time, the image signal Vs supplied from the signal line Ym is written to the pixel electrode 12 via the pixel transistor 14 and so-called sampling is performed. Next, when this pixel enters the non-selection period, the application of the gate pulse Vg is stopped and the low level gate voltage is applied, and the pixel transistor 14 is turned off, but the written image signal is held in the liquid crystal capacitor _CLC. ing.

When moving from the selection period to the non-selection period, since the rectangular wave gate pulse Vg falls abruptly from the high level to the low level, accumulated in the liquid crystal capacitance C _LC by coupling through the coupling capacitor C _GD described above this time The discharged electric charge is instantaneously discharged. This causes a voltage shift ΔV (not shown) in the image signal Vs written to the pixel electrode. Accordingly, since the value of the coupling capacitance C _GD varies among the individual pixels of the liquid crystal display panel, the voltage shift ΔV also varies. As a result, the display screen of the liquid crystal panel is changed periodically, so-called flicker. In addition, an afterimage is generated and the display quality is remarkably deteriorated.

Conventionally, for suppressing the absolute amount and the variation of the voltage shift [Delta] V, measures that larger form an auxiliary capacitance Cs connected in parallel to the liquid crystal capacitance C _LC had been taken. That is intended to store charge sufficient to compensate for the amount of charge is discharged via the coupling capacitor C _GD in advance the auxiliary capacitance Cs. The auxiliary capacitor Cs is of a so-called Cson Common type storage capacitor type in which an auxiliary capacitor electrode 13 independent of other electrodes is arranged so as to overlap the pixel electrode 12 and a common voltage is applied to the auxiliary capacitor electrode 13. In addition, there is a so-called Cson Gate type additional capacitance type in which a part of the scanning lines Xn, Xn + 1.

  The liquid crystal display panel 10A shown in FIGS. 5 to 7 is of the Cson Common type. The Cs on Gate type liquid crystal display panel is the same as the former in that one electrode of the auxiliary capacitor Cs is connected to the drain electrode D of the pixel transistor 14 as compared with the Cs on Common type. The other electrode of the capacitor Cs is different from the former in that it is connected to the scanning lines Xn, Xn + 1.

  However, in the conventional liquid crystal display panel, the auxiliary capacitor Cs is formed in the pixel electrode region regardless of whether it is a Cson Common type or a Cs on Gate type. Since the aperture ratio is sacrificed, sufficient display contrast cannot be obtained. Particularly, in recent years, small liquid crystal display panels for mobile phones have been improved in definition, and as a result, crosstalk due to parasitic capacitance between electrodes / wiring is likely to occur, so a large auxiliary capacitance Cs is required. However, since the ratio of signal lines or scanning lines other than the pixel electrodes increases with the increase in definition, the problem of a decrease in the aperture ratio of the pixels due to an increase in the auxiliary capacitance Cs is remarkable. Appear.

In addition, in the liquid crystal display panel, it is necessary to prevent light from leaking between the pixel electrode and the signal line and between the pixel electrode and the scanning line. In the Cson Common type liquid crystal display panel 10A shown in FIGS. 5 to 7, in order to prevent light from leaking from the boundary between the pixel electrode 12 and the signal lines Ym, Ym + 1,. +1... Is used to shield the signal line itself from light at the boundary between the pixel electrode 12 and the signal line. When such a configuration is adopted, the pixel electrode 12 and the signal line Ym, to parasitic capacity with new capacity occurs in parallel with the conventional parasitic capacitance C _SD between the Ym + 1 ···, the influence of the voltage shift ΔV of the aforementioned becomes larger.

On the other hand, in such Cson Common mode liquid crystal display panel, when shading a boundary between the pixel electrode and the signal line, the parasitic capacitance C _SD configured with a reduced parasitic capacitance is generated in parallel Patent Document 1 Is disclosed. The operation principle of the liquid crystal display panel 10B disclosed in the following Patent Document 1 is shown in FIG. 9 which is a plan view of several pixels, FIG. 10 which is an equivalent circuit of one pixel portion, and a cross-sectional view taken along line BB in FIG. This will be described with reference to FIG. Note that in the liquid crystal display panel 10B disclosed in Patent Document 1 below, the pixels are arranged in a staggered pattern, but here they are arranged in the same manner as the liquid crystal display panel 10A shown in FIG. The same components as those described above and shown in FIGS. 5 to 7 are designated by the same reference numerals, and detailed description thereof is omitted.

The Cson Common type liquid crystal display panel 10B shown in FIGS. 9 to 11 is different from the configuration of the liquid crystal display panel 10A shown in FIGS. 5 to 7 in that a part of the auxiliary capacitance electrode 13 is extended. This is that the extended portion 13 ′ covers the boundary portion between the signal line and the pixel electrode so as to shield the light. With such a configuration, a new capacitance Cad1 is generated between the extension portion 13 ′ of the auxiliary capacitance electrode 13 and the pixel electrode 12, and this new capacitance Cad1 is a conventional auxiliary capacitance as shown in FIG. Since it is connected in parallel with the capacitor Cs, it functions substantially as an auxiliary capacitor. That is, the liquid crystal display panel of Cs on Common method disclosed in Patent Document 1, without reduction in the aperture ratio, effectively reduced the new parasitic capacitance is generated in parallel with the parasitic capacitance C _SD This produces an effect that the boundary between the signal lines Ym, Ym + 1... And the pixel electrode 12 can be effectively shielded from light.
JP 2002-151699 A

  The inventors of the present application have conducted various experiments to obtain a configuration capable of achieving the same effect in a Cs on Gate type liquid crystal display panel different from the Cs on Common type liquid crystal display panel. In this case, the boundary between the signal line and the pixel electrode is shielded, and the auxiliary capacitance electrode is connected to the scanning line. The present invention has been completed by finding that the boundary between the pixel electrode and the pixel electrode can be effectively shielded from light.

  That is, an object of the present invention is to provide a Cson Gate type active matrix liquid crystal display panel that can achieve a high aperture ratio while being high definition.

  The above object of the present invention can be achieved by the following configurations. That is, the invention of the active matrix type liquid crystal display panel according to claim 1 is provided in the vicinity of an intersection of a plurality of signal lines and scanning lines arranged in a matrix on a translucent substrate, and the signal lines and scanning lines. A pixel transistor disposed at a position surrounded by each signal line and scanning line and connected to the pixel transistor, and an auxiliary capacitance electrode provided below the pixel electrode; In the active matrix type liquid crystal display panel provided with the scanning line, the scanning line is formed of a light-shielding member, and has an extension part wider than the signal line disposed below the signal line, The auxiliary capacitance electrode is electrically connected to the extension of the scanning line.

  According to a second aspect of the present invention, in the active matrix type liquid crystal display element according to the first aspect, the extension of the scanning line extends below the pixel electrode.

    According to a third aspect of the present invention, in the active matrix liquid crystal display element according to the first or second aspect, an interlayer film is provided at a constant height on the signal line, the scanning line, the auxiliary capacitance electrode, and the pixel transistor. Each pixel electrode is provided on the interlayer film.

  The present invention provides the following excellent effects by having the above-described configuration. That is, according to the first aspect of the present invention, the lower portion of the signal line can be shielded by the extension of the scanning line, and the light can be effectively shielded between the pixel electrode and the signal line. Since the capacitance generated between them functions as an auxiliary capacitance, even when the resolution is increased, the auxiliary capacitance can be increased while preventing the parasitic capacitance without lowering the aperture ratio. An active matrix type liquid crystal display panel with good display quality that hardly causes afterimages can be obtained.

  According to the second aspect of the present invention, the light shielding between the pixel electrode and the signal line can be sufficiently performed, and the auxiliary capacity can be further increased. Therefore, the flicker and the afterimage are less likely to occur. An active matrix type liquid crystal display panel with good display quality can be obtained.

  According to the invention of claim 3, since the surface of the pixel electrode becomes flat and the cell gap is made uniform over the entire surface of the pixel electrode, the active matrix having good display quality with little variation in display quality for each pixel. Type liquid crystal display panel is obtained.

  Hereinafter, embodiments of an active matrix liquid crystal display panel according to the present invention will be described in detail with reference to the drawings. However, the embodiment described below exemplifies an active matrix type liquid crystal display panel for embodying the technical idea of the present invention, and is not intended to specify the present invention in this embodiment. The present invention can be equally applied to various modifications without departing from the technical idea shown in the claims. 1 is a plan view of several pixels of the active matrix liquid crystal display panel of the embodiment, FIG. 2 is a schematic equivalent circuit diagram of one pixel portion, and FIG. It is X sectional drawing. For ease of understanding, the same components as those of the conventional Cs on common type liquid crystal display panel shown in FIGS.

  The liquid crystal display panel 10 of the present embodiment is surrounded by scanning lines Xn, Xn + 1... And signal lines Ym, Ym + 1... Provided in a matrix on the first translucent substrate 11. A pixel electrode 12 is provided for each region, and an auxiliary capacitance electrode 13 and a pixel transistor 14 are provided below the pixel electrode 12. Further, the counter electrode 16 provided on the second translucent substrate 15 via the color filter layer CF is provided. A liquid crystal 20 is sealed between the pixel electrode 12 and the counter electrode 16.

  The pixel transistor 14 is made of a TFT, and its source electrode S is connected to the signal lines Ym, Ym + 1..., And the drain electrode D is connected to the pixel electrode 12 via the contact hole 17. The gate electrode G of the transistor 14 also serves as scanning lines Xn, Xn + 1. In the liquid crystal display panel 10, the entire surface of the first translucent substrate 11 is covered so as to cover each pixel transistor 14, the scanning lines Xn, Xn + 1... And the signal lines Ym, Ym + 1. In addition, the interlayer film 19 is provided so as to have a predetermined height through the insulating film 18, and the pixel electrode is provided on the surface of the interlayer film 19 so that the cell gap is kept constant, and the contact hole 17 is connected to the drain electrode D of a predetermined pixel transistor 14.

  In the liquid crystal display panel 10 of the present embodiment, the scanning lines Xn, Xn + 1... Are formed of a light-shielding member, and the signal lines extending below the signal lines Ym, Ym + 1. A wider extension portion 21 is provided, and this extension portion 21 is provided so as to be slightly overlapped with the end portion of the pixel electrode 12 so as to completely shield light from the pixel electrode 12. The capacitor electrode 13 is electrically connected. With this configuration, a new capacitor Cad2 is formed between the scanning line extension portion 21 and the pixel electrode 12, and this new capacitor Cad2 is formed as shown in FIG. Since it is connected in parallel with the capacitor Cs, it substantially functions as an auxiliary capacitor. In addition, since the overlapping portion between the scanning line extension portion 21 and the pixel electrode 12 is small, the decrease in the aperture ratio is small.

Hereinafter, the manufacturing process of the liquid crystal display panel 10 will be described with reference to FIGS. First, a scanning line is formed into a predetermined pattern using a light-shielding conductive material made of Mo / Al directly on the surface of the first light-transmissive substrate 11 made of a glass substrate or the like or through an insulating film (not shown). Xn, Xn + 1... And the auxiliary capacitance electrode 13 are provided. Next, the entire surface of the first translucent substrate 11 is covered with an insulating film 22 made of SiO ₂ or SiN, and an amorphous-Si layer 23 is formed in the gate region. Next, the drain electrode D and the source electrode S of the pixel transistor 14 and the signal lines Ym, Ym + 1... Are formed in a predetermined pattern using Mo / Al / Mo, and a first light transmitting property is formed on the surface. The entire substrate 11 is covered with an insulating film 24 made of SiO ₂ or SiN, and an interlayer film 19 made of an organic material such as polyimide is provided on the surface thereof to have a predetermined thickness (about 3 μm). After the formation, each pixel electrode 12 is formed in a predetermined pattern using ITO (Indium Tin Oxide) which is a transparent conductive material.

  Then, the liquid crystal 20 of this embodiment is sealed by facing the surface of the second translucent substrate 15 on which the transparent counter electrode 16 made of the color filter layer CF and ITO is formed, and enclosing the liquid crystal 20 therebetween. The display panel 10 is completed.

  In the liquid crystal display panel 10 of this embodiment, the common potential Vc applied to the counter electrode 16 is periodically inverted as in the case of the conventional Cs on common method shown in FIG. The image signal Vs applied to the signal lines Ym, Ym + 1,. However, in the liquid crystal display panel 10 of this embodiment, since the auxiliary capacitance electrode 13 is connected to the scanning lines Xn, Xn + 1..., As shown in FIG. The gate pulse Vg applied to the gate electrode Vg in a form in which the common potential Vc is superimposed on the conventional gate pulse is obtained because the common potential Vc applied to the counter electrode 16 is periodically inverted. It is necessary to apply.

    In this embodiment, the extension portions 21 of the scanning lines Xn, Xn + 1... Are provided so as to slightly overlap the end portions of the pixel electrodes 12 so that the gap between the pixel electrodes 12 and the extension portions 21 is completely provided. Although an example in which light is shielded is shown, if it is not always necessary to completely shield this part, it may be provided so that the space between the pixel electrode 12 and the extension 21 is extremely narrow.

It is a top view for several pixels of the active matrix type liquid crystal display panel of an Example. FIG. 2 is a schematic equivalent circuit diagram of one pixel portion of the active matrix liquid crystal display panel of FIG. 1. It is XX sectional drawing of FIG. FIG. 2 is a diagram illustrating voltage waveforms of respective portions of one pixel of the active matrix liquid crystal display panel of FIG. 1. It is a top view of one pixel part of the conventional active matrix type liquid crystal display panel. FIG. 6 is a schematic equivalent circuit diagram of one pixel portion of the active matrix liquid crystal display panel of FIG. 5. It is AA sectional drawing of FIG. FIG. 6 is a diagram illustrating voltage waveforms of respective portions of one pixel of the active matrix liquid crystal display panel of FIG. 5. It is a top view of one pixel part of another conventional active matrix type liquid crystal display panel. FIG. 10 is a schematic equivalent circuit diagram of one pixel portion of the active matrix liquid crystal display panel of FIG. 9. It is BB sectional drawing of FIG.

Explanation of symbols

10, 10A, 10B Active matrix liquid crystal display panel 11 First translucent substrate 12 Pixel electrode 13 Auxiliary capacitance electrode 14 Pixel transistor (TFT)
15 Second translucent substrate 16 Common electrode 17 Contact holes 18, 22, 24 Insulating film 19 Interlayer film 20 Liquid crystal 21 Scanning line extension 23 Amorphous silicon layer CF Color filter layer Xn, Xn + 1... Scanning line Ym, Ym + 1 ... Signal line

Claims (3)

A plurality of signal lines and scanning lines arranged in a matrix on the substrate, pixel transistors arranged near intersections of the signal lines and scanning lines, and positions surrounded by the signal lines and scanning lines, respectively. In an active matrix liquid crystal display panel having a pixel electrode disposed and connected to the pixel transistor, and an auxiliary capacitance electrode provided below the pixel electrode, the scanning line is formed of a light-shielding member. And an extension portion wider than the signal line disposed below the signal line, and the auxiliary capacitance electrode is electrically connected to the extension portion of the scanning line. An active matrix liquid crystal display panel. 2. The active matrix type liquid crystal display device according to claim 1, wherein an extension of the scanning line extends below the pixel electrode. The interlayer film is provided at a certain height on the signal line, the scanning line, the auxiliary capacitance electrode, and the pixel transistor, and each pixel electrode is provided on the interlayer film. 3. An active matrix liquid crystal display element according to 1 or 2.

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